U.S. patent application number 14/920451 was filed with the patent office on 2016-02-11 for glass particles.
This patent application is currently assigned to IDEMITSU KOSAN CO., LTD.. The applicant listed for this patent is Ryo ABURATANI, Masao AIDA, Tadanori JUNKE, Minoru SENGA. Invention is credited to Ryo ABURATANI, Masao AIDA, Tadanori JUNKE, Minoru SENGA.
Application Number | 20160043433 14/920451 |
Document ID | / |
Family ID | 47914159 |
Filed Date | 2016-02-11 |
United States Patent
Application |
20160043433 |
Kind Code |
A1 |
ABURATANI; Ryo ; et
al. |
February 11, 2016 |
GLASS PARTICLES
Abstract
Glass particles including Li, P and S, wherein when a Raman
spectrum of the glass particles is measured five times or more and
a peak at 330 to 450 cm.sup.-1 in the Raman spectrum is separated
into peaks of components by waveform separation, the standard
deviation of the area ratio of each of the peaks of the components
is 3.0 or less, the area of the peak of PS.sub.4.sup.3- component
obtained by the waveform separation is 10 to 95% of the total area,
and the area of P.sub.2S.sub.7.sup.4- component obtained by the
waveform separation is 5 to 45% of the total area, and the area of
the peak of PS.sub.4.sup.3- component is larger than the area of
the peak of P.sub.2S.sub.7.sup.4- component.
Inventors: |
ABURATANI; Ryo;
(Sodegaura-shi, JP) ; SENGA; Minoru;
(Sodegaura-shi, JP) ; JUNKE; Tadanori;
(Sodegaura-shi, JP) ; AIDA; Masao; (Ichihara-shi,
JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
ABURATANI; Ryo
SENGA; Minoru
JUNKE; Tadanori
AIDA; Masao |
Sodegaura-shi
Sodegaura-shi
Sodegaura-shi
Ichihara-shi |
|
JP
JP
JP
JP |
|
|
Assignee: |
IDEMITSU KOSAN CO., LTD.
Chiyoda-ku
JP
|
Family ID: |
47914159 |
Appl. No.: |
14/920451 |
Filed: |
October 22, 2015 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
14345809 |
Mar 19, 2014 |
9196925 |
|
|
PCT/JP2012/005992 |
Sep 20, 2012 |
|
|
|
14920451 |
|
|
|
|
Current U.S.
Class: |
429/322 |
Current CPC
Class: |
C03C 1/02 20130101; C03C
12/00 20130101; C01P 2004/61 20130101; H01M 10/0525 20130101; C01B
17/22 20130101; C03C 10/00 20130101; H01M 2300/0068 20130101; C01P
2006/12 20130101; C01P 2006/14 20130101; C01B 17/36 20130101; C01P
2006/80 20130101; C03C 3/321 20130101; C03C 4/18 20130101; H01B
1/10 20130101; C01B 25/14 20130101; H01M 10/0562 20130101; Y02E
60/10 20130101 |
International
Class: |
H01M 10/0562 20060101
H01M010/0562; H01M 10/0525 20060101 H01M010/0525; C01B 25/14
20060101 C01B025/14 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 22, 2011 |
JP |
2011-207408 |
Mar 27, 2012 |
JP |
2012-071370 |
May 30, 2012 |
JP |
2012-122844 |
Claims
1: A method for producing an ionic conductive substance,
comprising: (i) contacting at least one compound selected from the
group consisting of phosphor sulfide, germanium sulfide, silicon
sulfide and boron sulfide with an alkali metal sulfide compound or
an alkaline earth metal sulfide in a solvent with stirring; and
(ii) circulating a product produced in the contacting (i) between a
pulverizer pulverizing the product in a solvent and a
temperature-retaining tank, with stirring of the product in the
solvent.
2: The method according to claim 1, wherein the alkali metal
sulfide compound or the alkaline earth metal sulfide is lithium
sulfide.
3: The method according to claim 1, wherein the compound is
phosphor sulfide.
4: The method according to claim 1, wherein the solvent in the (i)
contacting is an organic solvent.
5: The method according to claim 1, wherein the solvent in the (i)
contacting comprises a toluene.
6: The method according to claim 1, wherein the compound is
phosphor sulfide, the alkali metal sulfide compound or the alkaline
earth metal sulfide is lithium sulfide, and an amount ratio is
60:40<Li:P.ltoreq.85:15 in molar ratio.
7: The method according to claim 1, wherein the alkali metal
sulfide compound or the alkaline earth metal sulfide is lithium
sulfide, and the compound is phosphor sulfide.
8: The method according to claim 1, wherein the solvent in the (i)
contacting is an organic solvent, the compound is phosphor sulfide,
the alkali metal sulfide compound or the alkaline earth metal
sulfide is lithium sulfide, and the amount ratio becomes
60:40<Li:P.ltoreq.85:15 in molar ratio.
9: The method according to claim 1, wherein the solvent in the (i)
contacting comprises a toluene, the compound is phosphor sulfide,
the alkali metal sulfide compound or the alkaline earth metal
sulfide is lithium sulfide, and the amount ratio is
60:40<Li:P.ltoreq.85:15 in molar ratio.
10: The method according to claim 1, wherein the contact
temperature in the (i) contacting is from 50 to 210.degree. C.
11: The method according to claim 1, wherein the contact
temperature in the (i) contacting is from 50 to 210.degree. C., and
the stirring temperature in the temperature-retaining tank of the
(ii) circulating is from 50 to 210.degree. C.
12: The method according to claim 1, wherein the solvent in the (i)
contacting is the same as the solvent in the (ii) circulating.
13: The method according to claim 7, wherein the contact
temperature in the (i) contacting is from 50 to 210.degree. C.
14: The method according to claim 7, wherein the solvent in the (i)
contacting is the same as the solvent in the (ii) circulating.
15: The method according to claim 4, wherein the solvent in the (i)
contacting is the same as the solvent in the (ii) circulating.
16: The method according to claim 5, wherein the solvent in the (i)
contacting is the same as the solvent in the (ii) circulating.
17: The method according to claim 4, wherein the contact
temperature in the (i) contacting is from 50 to 210.degree. C.
18: The method according to claim 8, wherein the contact
temperature in the (i) contacting is from 50 to 210.degree. C.
Description
CROSS REFERENCE TO RELATED APPLICATION(S)
[0001] This application is a continuation of U.S. application Ser.
No. 14/345,809, filed on Mar. 19, 2014, which is a 35 U.S.C. 371
national stage patent application of international patent
application PCT/JP12/005992, filed Sep. 20, 2012, the text of which
is incorporated by reference, and claims foreign priority to JP
2011-207408 filed on Sep. 22, 2011, JP 2012-071370 filed on Mar.
27, 2012, and JP 2012-122844, filed on May 30, 2012, the entire
content of which is incorporated herein by reference.
TECHNICAL FIELD
[0002] The invention relates to solid electrolyte glass particles
used in a lithium ion battery or the like.
BACKGROUND ART
[0003] In recent years, a highly safe and high-capacity lithium ion
battery has been actively developed.
[0004] Due to the liquid electrolyte, a lithium ion battery which
has been practically used at present has a drawback that it is not
safe. Therefore, an inorganic solid electrolyte has been developed
(Patent Document 1).
[0005] All-solid lithium battery using an inorganic solid
electrolyte in Patent Document 1 is highly safe. However, since it
is produced by subjecting lithium sulfate and phosphorous
pentasulfide to mechanical milling, the surface is not uniform, and
hence, the battery performance may be deteriorated.
[0006] The uniformity of the electrolyte surface is an important
property in stabilizing the performance of a battery as a final
product. Since the electrolyte surface is a medium on which lithium
ions move directly, if the uniformity thereof is poor, resistance
partially increases, and as a result, stable battery performance is
not developed. Further, in order to allow it to be glass ceramic,
if the electrolyte surface is not uniform, crystals that are
favorable for attaining excellent conductivity are not formed
partially. As a result, when used in a battery, such an un-uniform
surface of an electrolyte may lower the battery performance.
RELATED ART DOCUMENTS
Patent Document
[0007] Patent Document 1: JP-A-H11-134937
SUMMARY OF THE INVENTION
[0008] A first object of the invention is to obtain glass particles
having uniform surfaces and are capable of suppressing a partial
increase in resistance.
[0009] A second object of the invention is to shorten the
production time of a solid electrolyte.
[0010] A third object of the invention is to provide a method for
producing an ionic conductive substance which can be produced for a
short period of time and spends only a small amount of energy in
production.
[0011] The above-mentioned first to third objects respectively
correspond to the following first to third inventions.
[0012] According to the first invention, the following glass
particles are provided.
1. Glass particles comprising Li, P and S, wherein when a Raman
spectrum of the glass particles is measured five times or more and
a peak at 330 to 450 cm.sup.-1 in the Raman spectrum is separated
into peaks of components by waveform separation, the standard
deviation of the area ratio of each of the peaks of the components
is 3.0 or less,
[0013] the area of the peak of PS.sub.4.sup.3- component obtained
by the waveform separation is 10 to 95% of the total area, and the
area of P.sub.2S.sub.7.sup.4- component obtained by the waveform
separation is 5 to 45% of the total area, and
[0014] the area of the peak of PS.sub.4.sup.3- component is larger
than the area of the peak of P.sub.2S.sub.7.sup.4- component.
2. The glass particles according to 1, wherein the standard
deviation is 2.7 or less, the area of the peak of PS.sub.4.sup.3-
component is 70 to 90% of the total area and the area of
P.sub.2S.sub.7.sup.4- component is 5 to 20% of the total area. 3.
The glass particles according to 1 or 2 having an average particle
diameter of 10 .mu.m or less. 4. The glass particles according to
any of 1 to 3 which are produced by using lithium sulfide having a
specific surface area of 0.1 m.sup.2/g or more and a pore volume of
0.02 ml/g or more.
[0015] According to the second invention, the following method for
producing a solid electrolyte is provided.
1. A method for producing a solid electrolyte wherein a slurry
comprising a raw material comprising alkali metal sulfide particles
and a solvent is circulated between a pulverizer that synthesizes a
solid electrolyte by reacting the raw material while pulverizing
and a temperature-retaining apparatus that retains the slurry at
40.degree. C. to 300.degree. C., wherein the alkali metal sulfide
particles have a specific surface area measured by the BET method
of 10.0 m.sup.2/g or more. 2. A method for producing a solid
electrolyte wherein a slurry comprising a raw material comprising
alkali metal sulfide particles and a solvent is circulated between
a pulverizing means that synthesizes a solid electrolyte by
reacting the raw material while pulverizing and a
temperature-retaining means that retains the slurry at 40.degree.
C. to 300.degree. C., wherein the alkali metal sulfide particles
have a specific surface area measured by the BET method of 10.0
m.sup.2/g or more. 3. The method for producing a solid electrolyte
according to 1 or 2, wherein the alkali metal sulfide particles
have a diameter of 100 .mu.m or less. 4. The method for producing a
solid electrolyte according to any of 1 to 3, wherein the alkali
metal sulfide particles are lithium sulfide particles and the raw
material further comprise one or more compounds selected from
phosphor sulfide, germanium sulfide, silicon sulfide and boron
sulfide.
[0016] According to the third invention, the following method for
producing an ionic conductive substance or the like is
provided.
1. A method for producing an ionic conductive substance
comprising:
[0017] a first process in which one or more compounds selected from
phosphor sulfide, germanium sulfide, silicon sulfide and boron
sulfide are brought into contact with an alkali metal sulfide
compound or an alkaline earth metal sulfide in a solvent with
stirring, and
[0018] a second process in which a product produced in the first
process is subjected to a mechanical treatment.
2. The method for producing an ionic conductive substance according
to 1, wherein the mechanical treatment in the second process is
conducted in a solvent. 3. The method for producing an ionic
conductive substance according to 1 or 2, which further comprises a
third process in which the product that has been subjected to a
mechanical treatment in the second process is stirred in a solvent,
and the second process and the third process are alternately
repeated. 4. The method for producing an ionic conductive substance
according to any of 1 to 3, wherein the alkali metal sulfide
compound or the alkaline earth metal sulfide is lithium sulfide. 5.
The method for producing an ionic conductive substance according to
any of 1 to 4, wherein the one or more compounds selected from
phosphor sulfide, germanium sulfide, silicon sulfide and boron
sulfide is phosphor sulfide.
[0019] According to the first invention, glass particles having
uniform surfaces and are capable of suppressing a partial increase
in resistance can be provided.
[0020] According to the second invention, the production time of
solid electrolyte can be shortened.
[0021] According to the third invention, a method for producing an
ionic conductive substance which can be produced for a short period
of time and spends only a small amount of energy in production can
be provided.
BRIEF DESCRIPTION OF THE DRAWINGS
[0022] FIG. 1 is a Raman spectrum of glass particles prepared in
Example 1-1 of the first invention;
[0023] FIG. 2 is a spectrum obtained by separating a Raman spectrum
of glass particles prepared in Comparative Examples 1-1 of the
first invention;
[0024] FIG. 3 is a SEM photograph of glass particles prepared in
Example 1-1 of the first invention;
[0025] FIG. 4 is a view showing one example of an apparatus that
can be used in the production methods according to the first and
second inventions; and
[0026] FIG. 5 is a view showing another example of an apparatus
that can be used in the production methods according to the first
and second inventions.
MODE FOR CARRYING OUT THE INVENTION
First Invention
[0027] The glass particles of the invention comprise each of Li, P
and S elements. For each sample, a Raman spectrum is measured five
or more times. A peak at 330 to 450 cm.sup.-1 in the Raman spectrum
is separated into peaks of components by waveform separation, and
the standard deviation of the area ratio of each component is 3.0
or less. The peak surface area of the PS.sub.4.sup.3- component
obtained by the waveform separation is 10 to 95% of the total area.
The peak surface area of the P.sub.2S.sub.7.sup.4- component is 5
to 45% of the total area. That is, the peak area of the
PS.sub.4.sup.3- component is larger than the peak area of the
P.sub.2S.sub.7.sup.4- component.
[0028] The Raman spectrum is used to grasp the state of a solid,
powder or the like. By grasping the properties of the spectrum, the
property of a solid material is specified (see JP-A-2005-336000,
JP-A-H10-326611 and JP-A-2001-19450).
[0029] The Raman spectrum is suited to analyze the surface state of
a solid. When the particles in the same lot are measured, if the
composition on the particle surfaces is not uniform, a different
spectrum is obtained.
[0030] For example, when a solid material is subjected to
mechanical milling, if a fully pulverized part and an
insufficiently pulverized part (e.g. in which the material is
adhered to the wall) are mixed, the spectrum varies due to
deteriorated uniformity of the particles. As a result, if the
measurement is repeated, reproducibility of the spectrum is
lowered. Therefore, by taking the spectrum of the uniform material
as the standard and by comparing the spectrum of measured particles
with the standard, the surface state of the measured particles can
be evaluated. In the invention, with the reproducibility of the
spectrum (variance, in particular) being taken as an index, the
surface state of the particles is evaluated.
[0031] FIG. 1 shows an example of the Raman spectrum of the glass
particles of the invention.
[0032] In the glass particles of the invention, a characteristic
peak is detected around 400 cm.sup.-1. Due to its asymmetric shape,
this peak is a mixed peak of a plurality of components. This peak
is confirmed to be a mixed peak of three components of
PS.sub.4.sup.3-, P.sub.2S.sub.7.sup.4- and P.sub.2S.sub.6.sup.4-
(M. Tachez, J.-P. Malugani, R. Mercier, and G. Robert, Solid State
Ionics, 14,181(1984)).
[0033] It is desired that the above-mentioned peaks are detected
according to the component by using an apparatus having a high
resolution power. However, it is possible to separate into
individual peaks by using a common or apparatus-dedicated waveform
analysis software. As the waveform analysis software, GRAMS Al
manufactured by Thermo SCIENTIFIC can be used, for example.
[0034] FIG. 2 shows an example in which the peaks are separated
into individual peaks by using a waveform analysis software. From
the peak separated, the area of each component can be obtained.
[0035] The standard deviation can be calculated from the
above-mentioned area by using a common calculation method. It is
desirable to conduct calculation five or more times (five or more
locations) for one object to be measured (an aggregate of
particles). It does not mean the same location of one object to be
measured is measured repeatedly, but means different locations of
the object to be measured is measured five or more times.
[0036] If the standard deviation of the area ratio of each
component (PS.sub.4.sup.3-, P.sub.2S.sub.7.sup.4- and
P.sub.2S.sub.6.sup.4-) is 3.0 or less, the surface of each glass
particle is uniform, and when used in a battery, the battery
performance is stabilized. Each of the above-mentioned standard
deviations is preferably 2.7 or less, more preferably 2.5 or less,
with 2.0 or less being particularly preferable. Although no
specific restrictions are imposed on the lower limit, the lower
limit is normally 0.1 or more.
[0037] The molar ratio of each element, i.e. Li, P and S, of glass
particles can be adjusted by the elemental ratio of the raw
material. The elemental ratio of the raw material is almost
coincident with the elemental ratio of the glass.
[0038] The glass particles of the invention may comprise only Li, P
and S as mentioned above, and, in addition to these elements, a
substance including Al, B, Si, Ge or the like may be contained.
Such a substance may be contained in an amount of 1.0% or less, for
example.
[0039] In the invention, the area of the peak of the
PS.sub.4.sup.3- component obtained by waveform separation is 10 to
95% of the total area, the area of the peak of the
P.sub.2S.sub.7.sup.4- component is 5 to 45% of the total area, and
the area of the peak of the PS.sub.4.sup.3- component is larger
than the peak of the P.sub.2S.sub.7.sup.4- component. As a result,
a stable electrolyte can be obtained. It is preferred that the area
of the peak of the PS.sub.4.sup.3- component be 70 to 90% of the
total area. For example, it is 75 to 85%. The area of the peak of
the P.sub.2S.sub.7.sup.4- component is 5 to 20% of the entire area.
For example, the area is 7 to 15%.
[0040] If the conditions of the peak are outside the
above-mentioned range, the uniformity of the invention cannot be
obtained especially in a region having a large amount of the
P.sub.2S.sub.7.sup.4- component. JP-A-2010-250981 states that, in
the mechanical milling method, a uniform electrolyte cannot be
obtained easily by simply prolonging the milling time. In contrast,
under the above-mentioned peak conditions, a uniform electrolyte
can be obtained in the mechanical milling method by conducting
milling for a sufficiently long period of time.
[0041] It is preferred that the glass particles be produced from
Li.sub.2S and P.sub.2S.sub.5. As for the amount ratio (mol %),
Li.sub.2S:P.sub.2S.sub.5 is preferably 72 to 82:28 to 18, more
preferably 72 to 80:28 to 20, with 73 to 78:27 to 22 being further
preferable.
[0042] The average particle size of the glass particles is
preferably 10 .mu.m or less. More preferably, 0.10 .mu.m or more
and 8 .mu.m or less. Further preferably, 0.15 .mu.m or more and 7
.mu.m or less.
[0043] The average particle size means the average value of the
major axes of a plurality of glass particles which have been
arbitrary selected by observing the glass particles by a scanning
electron microscope (SEM).
[0044] The amount of the organic solvent (used in production)
remained in the glass particles of the invention is preferably 5.0
wt % or less, more preferably 3.0 wt % or less.
[0045] The glass particles of the invention can be produced by
using a raw material comprising an organic compound, an inorganic
compound or both of an organic compound and an inorganic compound.
It is preferred that the glass particles of the invention be
produced from lithium sulfate (Li.sub.2S) and phosphorus
pentasulfide (P.sub.2S.sub.5) as the raw material.
[0046] As the lithium sulfide, commercially-available high-purity
lithium sulfide can be used. The purity is preferably 95% or
more.
[0047] The purity of lithium sulfate can be measured by
titration.
[0048] The specific surface area of lithium sulfide is preferably
0.1 m.sup.2/g or more, more preferably 1.0 m.sup.2/g or more. The
upper limit is not particularly restricted, but normally 200
m.sup.2/g or less.
[0049] The pore volume of lithium sulfide is preferably 0.02 ml/g
or more, more preferably 0.05 ml/g or more. The upper limit is not
particularly restricted, but normally 5 ml/g or less.
[0050] The surface area and pore volume of lithium sulfide are
values measured by the BET method using nitrogen.
[0051] The lithium sulfide as mentioned above can be produced by
the following method, for example. A hydrogen sulfide gas is blown
to a slurry comprising lithium hydroxide and a hydrocarbon-based
organic solvent, thereby allowing the lithium hydroxide and the
hydrogen sulfide to react. The reaction is continued while removing
the water generated by the reaction from the slurry, and after the
reaction system has become substantially empty of the water
content, blowing of the hydrogen sulfide is stopped, and then an
inert gas is blown (see JP-A-2010-163356).
[0052] No specific restrictions are imposed on the phosphorus
pentasulfide, as long as it is commercially produced and sold.
Instead of P.sub.2S.sub.5, phosphor (P) as a simple substance and
sulfur (S) as a simple substance can be used with a corresponding
molar ratio.
[0053] The glass particles of the invention can be produced by
subjecting a specific amount of the above-mentioned raw material to
mechanical milling (MM) for a sufficiently long period of time.
[0054] As the apparatus to be used in the mechanical milling, a
planetary ball mill or the like can be given. As the ball, a
zirconia ball can be used. It is preferred that the ball be in the
form of a sphere having a diameter of 10 mm or more and 30 mm or
less.
[0055] An alumina-made pot can be used, and the size thereof is
preferably 5 L or more and 10 L or less.
[0056] The amount of the raw material to be put in a ball mill is
preferably 20 vol % to 50 vol % relative to the amount of balls
placed in the ball mill. The number of rotations at the time of the
treatment is preferably 100 rpm or more and 500 rpm or less, and
the rotation time is preferably 100 hours or more and 480 hours or
less.
[0057] The glass particles of the invention can be obtained by
mixing the pulverized raw material in a solvent to obtain a slurry,
and conducting a reaction while pulverizing the raw material in the
slurry (hereinafter referred to as the "slurry method").
[0058] For example, it can be obtained by allowing the slurry
containing the raw material that contains lithium sulfide and a
solvent to circulate between a pulverizing machine that synthesizes
a solid electrolyte by allowing the raw material to react while
pulverizing the raw material and a temperature-retaining apparatus
that retains the slurry at 40.degree. C. to 300.degree. C.
[0059] It is preferred that the lithium sulfide used as the raw
material have a specific surface area measured by the BET method of
10.0 m.sup.2/g or more. It is preferable to use lithium sulfide as
the raw material after finely pulverizing (hereinafter, referred to
as modification).
[0060] The above-mentioned slurry method and the modification
method are as explained in the second invention, given later.
Second Invention
[0061] The method for producing a solid electrolyte of the
invention is a method wherein a slurry containing the raw material
that contains alkali metal sulfide particles and a solvent is
circulated between a pulverizing machine that synthesizes a solid
electrolyte by allowing the raw material to react while pulverizing
the raw material and a temperature-retaining apparatus that retains
the slurry at 40.degree. C. to 300.degree. C. (slurry method). In
the invention, as the alkali metal sulfide particles, one having a
specific surface area measured by the BET method of 10.0 m.sup.2/g
or more is used.
[0062] According to the method of the invention, the time required
for the production of a solid electrolyte can be shortened. Even in
the case where the molar ratio of lithium sulfide in the raw
material exceeds 70 mol %, the production time can be
shortened.
[0063] Further, even if the molar ratio of lithium sulfide exceeds
75 mol %, the amount of remaining lithium sulfide as the raw
material is very small or almost zero.
[0064] As the method for producing a sulfide-based solid
electrolyte, a method of producing an electrolyte by a
heating/melting method at a high temperature (WO2005/119706), a
method in which a solid electrolyte is produced by the milling
method while conducting pulverization (JP-A-H11-134937) or the like
can be mentioned.
[0065] However, the production method disclosed in WO2005/119706
has a defect that it requires a special equipment since production
is conducted at high temperatures, and a large amount of energy is
required during production.
[0066] In the production method disclosed in JP-A-11-134937, since
a milling machine is required and used, energy is required.
[0067] As the method for producing a solid electrolyte, the raw
material is circulated between a pulverization/synthesis means that
synthesizes a solid electrolyte by allowing the raw material to
react in a hydrocarbon-based solvent while pulverizing and a
synthesis means that synthesizes a solid electrolyte by allowing
the raw material to react in a hydrocarbon-based solvent is
disclosed (JP-A-2010-140893).
[0068] However, the manufacturing method disclosed in
JP-A-2010-140893 has a defect that the production of a solid
electrolyte takes time. In particular, in a region where the molar
ratio of lithium sulfide in the raw material exceeds 70 mol %, a
solid electrolyte having a high ionic conductivity cannot be
obtained when the reaction time is insufficient.
[0069] In the invention, first, a slurry is prepared by mixing a
raw material that contains alkali metal sulfide particles and a
solvent.
[0070] The alkali metal sulfide particles used as the raw material
have a specific surface area measured by the BET method of 10.0
m.sup.2/g or more. Due to such a specific surface area, the
production time of a solid electrolyte can be shortened. The
specific surface area is preferably 12.0 m.sup.2/g or more, more
preferably 17.0 m.sup.2/g or more, further preferably 25.0
m.sup.2/g or more, further preferably 31.0 m.sup.2/g or more, with
35 m.sup.2/g or more being most preferable.
[0071] The upper limit of the specific surface area is not
particularly restricted, but normally 200 m.sup.2/g or less.
[0072] The particle size of alkali metal sulfide particles used as
the raw material is preferably 100 .mu.m or less, more preferably
80 .mu.m or less, and further preferably 50 .mu.m or less.
[0073] The particle size of alkali metal sulfide particles was
measured by means of Mastersizer 200 (manufactured by MALVERN
Instruments Ltd.) by the laser diffraction method and calculated
from the volume average particle size. It is desired that this
measurement be conducted directly in the slurry state without
passing through the dried state. The reason therefor is that, once
drying is conducted, particles are aggregated at the time of
drying, whereby the apparent particle size may become large.
[0074] Further, it is preferred that the alkali metal sulfide
particles used as the raw material have a pore volume of 0.01 ml/g
or more. If the alkali metal sulfide particles have a pore volume
of 0.01 ml/g or more, they can be reacted easily with the raw
materials other than the alkali metal sulfide particles. At the
same time, the alkali metal sulfide particles can be pulverized
easily, whereby the reaction can proceed more easily.
[0075] The pore volume of the alkali metal sulfide particles is
more preferably 0.1 ml/g or more, further preferably 0.2 ml/g or
more.
[0076] The upper limit of the pore volume is not particularly
restricted, but normally, it is 5 ml/g or less.
[0077] It is preferred that the alkali metal sulfide particles used
as the raw material be lithium sulfide (Li.sub.2S) particles.
[0078] Further, the particles may contain one or more compounds
selected from phosphor sulfide, germanium sulfide, silicon sulfide
and boron sulfide as the raw material. Of these, phosphor sulfide
is preferable. The kind of the sulfide is not particularly limited,
and those commercially available can be used. Preferred are one or
more compounds selected from lithium sulfide and one or more
compounds selected from phosphor sulfide, germanium sulfide,
silicon sulfide and boron sulfide. Lithium sulfide and phosphor
sulfide are more preferable.
(i) Method for Producing Lithium Sulfide
[0079] For example, lithium sulfide can be prepared by the methods
described JP-A-H07-330312, JP-A-H09-283156, JP-A-2010-163356 and
JP-A-2011-84438.
[0080] Specifically, lithium hydroxide and hydrogen sulfide are
reacted in a nonprotonic organic solvent to produce lithium
hydrogen sulfide. Then, this reaction liquid is hydrodesulfurized
to form lithium sulfide (JP-A-H07-330312).
[0081] Further, by reacting lithium sulfide and gaseous sulfur
source at a temperature of 130.degree. C. or more and 445.degree.
C. or less, lithium sulfide can be synthesized
(JP-A-H09-283156).
[0082] Further, lithium sulfide (Li.sub.2S) as the raw material can
be synthesized by reacting, in an organic solvent, lithium
hydroxide and hydrogen sulfide, for example. Specifically, a
hydrogen sulfide gas is blown to a slurry comprising lithium
hydroxide and an organic solvent, thereby to react lithium
hydroxide and hydrogen sulfide. At this time, the reaction
continues while removing water generated by this reaction from the
slurry. When the water in the system is substantially removed,
lithium sulfide is produced by stopping blowing of the hydrogen
sulfide and by starting blowing of an inert gas
(JP-A-2010-163356).
[0083] The organic solvent used in this method is not particularly
limited, a solvent which forms an azeotropic composition with water
is preferable. The organic solvent may be used singly or in a
combination of two or more. Specifically, a hydrocarbon-based
organic solvent can be given. One selected from benzene (boiling
point: 80.degree. C.), toluene (boiling point: 111.degree. C.),
xylene (boiling point: p-body, 138.degree. C., m-body, 139.degree.
C., o-body, 144.degree. C.), ethylbenzene (boiling point:
136.degree. C.) and dodecane (boiling point: 215.degree. C.) or a
mixture thereof can be preferably used.
[0084] Further, lithium hydroxide and hydrogen sulfide are reacted
in an aqueous solvent at a temperature of 10.degree. C. to
100.degree. C. to form lithium hydrogen sulfide. Then, the reaction
liquid is hydrodesulfurized, whereby lithium sulfide can be
synthesized (JP-A-2011-84438).
(ii) Purity of Lithium Sulfide
[0085] As for lithium sulfide, the total content of a lithium salt
of a sulfur oxide is preferably 0.15 mass % or less, more
preferably 0.1 mass % or less and the content of lithium
N-methylaminobutyrate is preferably 0.15 mass % or less, more
preferably 0.1 mass % or less. If the total content of a lithium
salt of a sulfur oxide is 0.15 mass % or less, a solid electrolyte
obtained by melt quenching or mechanical milling becomes a
glass-like electrolyte (completely amorphous). On the other hand,
if the total content of a lithium salt of a sulfur oxide exceeds
0.15 mass %, the resulting electrolyte may be a crystallized
product from the beginning, and this crystallized product has a low
ionic conductivity. Further, this crystallized product does not
change even if it is subjected to a heat treatment, and a
sulfide-based solid electrolyte having a high ionic conductivity
may not be obtained.
[0086] If the content of lithium N-methylaminobutyrate is 0.15 mass
% or less, a deteriorated product of lithium N-methylaminobutyrate
does not lower the cycle performance of a lithium ion battery. If
lithium sulfide having a reduced amount of impurities, an
electrolyte having a high ionic conductivity can be obtained.
(iii) Method for Purifying Lithium Sulfide
[0087] It is preferred that lithium sulfide produced by the method
described in JP-A-H07-330312 and JP-A-H09-283156 be purified since
it contains a lithium salt of a sulfur oxide or the like.
[0088] On the other hand, lithium sulfide produced by the method
for producing lithium sulfide disclosed in JP-A-2010-163356 has a
very small amount of a lithium salt of a sulfur oxide or the like,
and hence, it may be used for the production of a sulfide-based
solid electrolyte without being subjected to purification.
[0089] As the preferable method for purification, a purification
method disclosed in WO2005/40039 or the like can be given.
Specifically, lithium sulfide obtained as mentioned above is washed
at a temperature of 100.degree. C. or more by using an organic
solvent.
[0090] In order to increase the specific surface area and/or the
pore volume of the lithium sulfide prepared as mentioned above, for
example, lithium sulfide is modified (pulverized). Alternatively, a
physical technique using a mill or the like or a technique in which
a polar solvent having a solubility parameter of 9.0 or more is
added to lithium sulfide can be given.
[0091] If a physical method using a milling apparatus is used in
order to increase the specific surface area of lithium sulfide, it
can be conducted by a dry method or by a wet method.
[0092] In the case of a dry method, a ball mill, a planetary ball
mill, a tumbling mill, a jet mill or the like can be used. In the
case of a wet method, a non-aqueous solvent can be used as a
solvent. As the non-aqueous solvent, hexane, heptane, octane,
toluene, xylene, ethylbenzene, cyclohexane, methylcyclohexane,
petroleum ether or the like can be given. The same milling
apparatus as that used in the dry method can be used.
[0093] A technology in which a slurry solution of lithium sulfide
is prepared and the resulting slurry solution is supplied to or
circulated in a milling apparatus is also possible.
[0094] When a technology in which a polar solvent having one or
more polar groups is added to lithium sulfide in order to increase
the specific surface area of lithium sulfide is used, the following
method can be implemented.
[0095] The polar solvent (modifier) having a solubility parameter
of 9.0 or more is preferably a solvent having one or more polar
groups selected from a hydroxyl group, a carboxy group, a nitrile
group, an amino group, an amide bond, a nitro group, a
--C(.dbd.S)-bond, an ether (--O--) bond, a --Si--O-bond, a ketone
(--C(.dbd.O)--) bond, an ester (--C(.dbd.O)--O--) bond, a carbonate
(--O--C(.dbd.O)--O--) bond, a --S(.dbd.O)-bond, chloro, and
fluoro.
[0096] As the polar solvent containing one polar group, methanol
(14.5) (numbers in parentheses indicate the solubility parameter),
ethanol (12.7), n-propanol, isopropanol (11.5), n-butanol,
isobutanol, n-pentanol, water (23.4), ethylene glycol (14.2),
formic acid (13.5), acetic acid (12.6), acetonitrile (11.9),
propionitrile, malononitrile, succinonitrile, fumaronitrile,
trimethylsilyl=cyanide, N-methylpyrrolidone, triethylamine,
pyridine, dimethylformamide (12.0), dimethylacetamide,
nitromethane, carbon disulfide, diethyl ether, diisopropyl ether,
t-butyl methyl ether, phenyl methyl ether, dimethoxy methane,
diethoxy ethane, tetrahydrofuran, dioxane, trimethylmethoxysilane,
dimethyldimethoxysilane, tetramethoxysilane, tetraethoxysilane,
cyclohexylmethyldimethoxysilane, acetone (10.0), methyl ethyl
ketone, acetoaldehyde, ethyl acetate (9.0), acetic anhydride,
methylene carbonate, propylene carbonate, dimethylsulfoxide,
methylene chloride, chloroform, dichloroethane, dichlorobenzene,
hexafluorobenzene, trifluorobenzene or the like can be given.
[0097] As the polar solvent containing two types of the polar
group, 2,2,2-trifluoroethanol, hexafluoroisopropanol,
2-aminoethanol, chloroacetic acid, trifluoroacetic acid,
methoxypropionitrile, 3-ethoxypropionitrile, methyl cyanoacetae,
difluoroacetonitrile or the like can be given.
[0098] The solvent may include a solvent having a solubility
parameter of less than 9.0. As a solvent having a solubility
parameter of less than 9.0, hexane (7.3), heptane, octane, decane,
cyclohexane, ethylcyclohexane, methylcyclohexane, toluene (8.8),
xylene (8.8), ethylbenzene, Ipsol 100 (manufactured by Idemitsu
Kosan Co., Ltd.), Ipsol 150 (manufactured by Idemitsu Kosan Co.,
Ltd), IP solvent (manufactured by Idemitsu Kosan Co., Ltd), fluid
paraffin, petroleum ether or the like can be given.
[0099] The above-mentioned solvent having a solubility parameter of
9.0 or more and the solvent having a solubility parameter of less
than 9.0 are not required to be dehydrated. However, depending on
the amount of water, water may adversely affect the amount of an
alkali metal hydroxide generated as a by-product in a pulverized
product. Therefore, the amount of water is preferably 50 ppm or
less, more preferably 30 ppm or less.
[0100] The concentration in the total solvent of a polar solvent
having a solubility parameter of 9.0 or more (the total solvent
means one obtained by mixing a polar solvent having a solubility
parameter of 9.0 or more and a solvent having a solubility of less
than 9.0) is preferably 0.1 wt % or more and 100 wt % or less, more
preferably 0.2 wt % or more, with 0.5 wt % or more being most
preferable. A larger solubility parameter leads to greater
modification effects. Therefore, the amount thereof may be small.
On the contrary, if the solubility parameter is close to 9,
modification effects are small. Accordingly, it is required to
increase the amount added to prolong the modification time.
[0101] The boiling point of a polar solvent having a solubility
parameter of 9.0 or more is preferably 40.degree. C. to 300.degree.
C., more preferably 45.degree. C. to 280.degree. C. under normal
pressure. This temperature range is preferable in respect of
easiness in drying when a solvent is removed under heating in
vacuum.
[0102] When modification is conducted, the amount of lithium
sulfide is 0.5 parts by volume to 100 parts by volume, preferably 1
part by volume to 100 parts by volume, more preferably 1 part by
volume to 50 parts by volume relative to 100 parts by volume of the
total solvent (the total solvent means one obtained by mixing a
polar solvent having a solubility parameter of 9.0 or more and a
solvent having a solubility of less than 9.0).
[0103] The modification temperature varies according to the boiling
point and the solidification point of a solvent used. Preferably,
it is -100.degree. C. or more and 100.degree. C. or less, more
preferably -80.degree. C. or more and 80.degree. C. or less. A
desirable effect may not be obtained by a modification treatment at
high temperatures.
[0104] The modification time is preferably 5 minutes to 1 week,
with 1 hour to 5 days being more preferable.
[0105] The modification treatment may be conducted either in the
continuous phase or the batch phase. In the case of a batch
reaction, a common blade can be used for stirring. Preferable
blades include an Anchor blade, a Pfaudler blade, a helical blade,
and a max blend blade. On the laboratory scale, stirring by means
of a stirrer is commonly used. In the batch reaction, a reaction
tank using a ball mill is also usable.
[0106] After the modification treatment is completed, the solvent
is removed according to need. A polar solvent having a solubility
parameter of 9.0 or more is removed by heating in the vacuum or by
substitution with a non-polar solvent, for example. By the
substitution by the non-polar solvent, the solvent can be replaced
to a solvent having a solubility parameter of less than 9.0, for
example. If the processes after the modification require the slurry
state, it can be stored in the slurry state after this solvent
substitution is conducted.
[0107] The modified pulverized product is subjected to a drying
treatment if need arises in order to remove a remaining solvent.
The drying treatment is preferably conducted in a nitrogen
atmosphere or in vacuum. The drying temperature is preferably from
room temperature to 300.degree. C.
[0108] Depending on the type of a modification agent, an alkali
metal hydroxide may be formed as a by-product. This hydroxide can
be re-converted into a sulfide by introducing a hydrogen sulfide
gas to the slurry solution of a pulverized product. This blowing of
hydrogen sulfide can be conducted in a non-aqueous-based
solvent.
[0109] Modification (pulverization) of lithium sulfide can also be
conducted by using a polar solvent having a carbonate bond having a
solubility parameter of 8.5 or more instead of a polar solvent
having a solubility parameter of 9.0 or more.
[0110] As the polar solvent with a carbonate bond having a
solubility parameter of 8.5 or more, in addition to those mentioned
above, diethyl carbonate is included.
[0111] In the method for producing a solid electrolyte of the
invention, as the solvent for the slurry, a non-protonic organic
solvent (for example, a hydrocarbon-based organic solvent), a
non-protonic polar organic solvent (for example, an amide compound,
a lactam compound, a urea compound, an organic sulfur compound, a
cyclic organic phosphor compound, or the like) can be preferably
used as a single solvent or a mixed solvent.
[0112] The hydrocarbon-based solvent is saturated hydrocarbon,
unsaturated hydrocarbon, aromatic hydrocarbon or the like.
[0113] As the saturated hydrocarbon, hexane, pentane,
2-ethylhexane, heptane, decane, cyclohexane or the like can be
given.
[0114] As the unsaturated hydrocarbon, hexene, heptane, cyclohexene
or the like can be given.
[0115] As the aromatic hydrocarbon, toluene, xylene, decaline,
1,2,3,4-tetrahydronaphthalene or the like can be given.
[0116] Of these, toluene and xylene are particularly
preferable.
[0117] The amount of water in the solvent is preferably 50 ppm (by
weight) or less in respect of the reaction of the raw material
sulfide and the synthesized sulfide-based solid electrolyte. The
water causes the sulfide-based solid electrolyte to be de-natured,
thereby deteriorating the performance of a solid electrolyte.
Therefore, the amount of water is preferably as small as possible,
more preferably 30 ppm or less, and further preferably 20 ppm or
less.
[0118] In the invention, a reaction is conducted in the state where
a solvent is added to the above-mentioned raw material (for
example, including lithium sulfide and other sulfides). By
conducting a reaction in the state where a solvent is added,
granulation at the time of processing can be suppressed, whereby a
synthesis reaction can be promoted efficiently. As a result, a
solid electrolyte having excellent uniformity and has a low content
of an unreacted raw material can be obtained. Further, adhesion of
the raw material or the unreacted substance to the wall of an
apparatus can be prevented, whereby the yield of a product can be
improved.
[0119] The amount of lithium sulfide charged at the time of the
reaction is preferably 30 mol % to 95 mol % relative to the total
of lithium sulfide and other sulfides. The amount is further
preferably 60 mol % to 85 mol %, with 68 mol % to 80 mol % being
particularly preferable. By adjusting the raw material amount ratio
appropriately, a solid electrolyte having a high ionic conductivity
can be produced.
[0120] The amount of the solvent is added preferably in an amount
that allows the lithium sulfide and other sulfides as the raw
material to be a solution or a slurry. Normally, the amount of the
raw material added (total amount) relative to 1 kg of the solvent
is about 0.03 to 1 kg. The amount is preferably 0.05 to 0.5 kg,
with 0.1 to 0.3 kg being particularly preferable.
[0121] According to the production method of the invention, the
resulting slurry is circulated between a pulverizer (pulverizing
means) that synthesizes a solid electrolyte while pulverizing the
raw material and the temperature-retaining apparatus
(temperature-retaining means) that retains the slurry at 40.degree.
C. to 300.degree. C.
[0122] As the pulverizer (pulverizing means), a roll mill (a
tumbling mill), a swing mill, a vibration mill and a beads mill can
be given. Of them, a beads mill is preferable.
[0123] If the pulverizer includes a ball, in order to prevent
mixing in of foreign matters to a solid electrolyte due to the wear
of the ball and the container, it is preferred that the ball be
made of zirconium, reinforced aluminum or alumina.
[0124] The pulverization temperature by a pulverizer is preferably
20.degree. C. or more and 80.degree. C. or less, more preferably
20.degree. C. or more and 60.degree. C. or less. If the temperature
of the treatment by means of a pulverizer is less than 20.degree.
C., the effects of reducing the reaction time are small. If the
temperature of the treatment by means of a pulverizer exceeds
80.degree. C., lowering in strength of zirconia, reinforced alumina
and alumina becomes significant, and as a result, wear or
deterioration of a container or a ball or contamination of a solid
electrolyte may occur.
[0125] As the temperature-retaining apparatus
(temperature-retaining means), a container provided with a heater
or the like can be used.
[0126] The temperature retained by the temperature-retaining
apparatus is preferably 40.degree. C. to 200.degree. C., more
preferably 50.degree. C. to 150.degree. C., with 60.degree. C. to
100.degree. C. being further preferable. By retaining the
temperature, the temperature of the pulverizer can be stably
controlled. If the temperature is less than 40.degree. C.,
glassification takes time, thereby leading to insufficient
production efficiency. If the temperature exceeds 300.degree. C.,
unfavorable crystals may be precipitated. It is preferred that the
raw material be reacted in a hydrocarbon-based solvent to allow a
solid electrolyte to be synthesized in the temperature-retaining
apparatus.
[0127] The reaction is preferably conducted at a high temperature
since a reaction proceeds at a high speed in a high-temperature
zone. However, if the temperature of a pulverizer exceeds
80.degree. C., mechanical problems such as wear may occur.
Therefore, it is preferred that the temperature be retained higher
in the temperature-retaining apparatus, and the temperature be
retained relatively lower in the pulverizer.
[0128] By drying a reaction product and removing the solvent
therefrom, a sulfide-based solid electrolyte as sulfide glass is
obtained.
[0129] If the ionic conductivity is improved when crystallized, it
is preferable to crystalize. For example, a solid electrolyte
obtained from a raw material having a ratio
Li.sub.2S:P.sub.2S.sub.5 (molar ratio) of 68:32 to 72:28 can have
an improved ionic conductivity by further subjecting it to a heat
treatment of 200.degree. C. or more and 400.degree. C. or less,
more preferably 250.degree. C. to 320.degree. C. The reason
therefor is that sulfide-based solid electrolyte becomes sulfide
crystallized glass (glass ceramics).
[0130] The heat treatment time is preferably 1 hour to 5 hours,
with 1.5 hours to 3 hours being particularly preferable.
[0131] As a preferable embodiment, the heating in the drying
process and the heating in the crystallization process are not
conducted separately, but they are allowed to be a single heating
process.
[0132] FIG. 4 shows one example of an apparatus which can be used
when the method for producing a solid electrolyte of the invention
is implemented.
[0133] When a solid electrolyte is produced by using this apparatus
1, a slurry is respectively supplied to a pulverizer 10 and a
temperature-retaining tank 20. Hot water (HW) is placed in a heater
30 and then discharged (RHW). While keeping the temperature of the
pulverizer 10 by means of the heater 30 at 20.degree. C. to
80.degree. C., for example, the raw material is allowed to react
while being pulverized in a solvent, whereby a solid electrolyte is
synthesized. The temperature of the temperature-retaining tank 20
is retained by means of an oil bath 40 at 60.degree. C. to
300.degree. C., for example. Preferably, the raw material is
reacted in a solvent and a solid electrolyte is synthesized in the
temperature-retaining tank 20. At this time, a stirring blade 24 is
allowed to rotate by means of a motor (M) to stir the slurry,
thereby preventing precipitation of the raw material. A cooling
water (CW) is introduced into a cooling tube 26 and then discharged
(RCW). The cooling tube 26 cools and liquefies a gasified solvent
in a vessel 22. The liquefied solvent is returned to the vessel 22.
During the time period in which a solid electrolyte is synthesized
by the pulverizer 10, by means of a pump 54, the slurry is
circulated between the pulverizer 10 and the temperature-retaining
tank 20 after passing through connecting tubes 50 and 52.
[0134] When the pulverizer contains a ball, in order to prevent
mixing of the ball from the pulverizer 10 to the
temperature-retaining tank 20, a filter that separates the ball
from the raw material and solvent may be provided in the pulverizer
10 or a first connecting tube 50.
[0135] The ratio of the capacity of the temperature-retaining tank
20 and the capacity of the pulverizer 10 may be arbitral, but
normally, the capacity of the temperature-retaining tank 20 is
about 1 to 100 times that of the capacity of the pulverizer 10.
[0136] FIG. 5 is a view showing another production apparatus.
[0137] A production apparatus 2 is the same as the above-mentioned
production apparatus 1 except that a heat exchanger 60 (heat
exchanging means) is attached to a second connection part 52. The
same elements are indicated by the same numerals, and a detailed
explanation is omitted.
[0138] The heat exchanger 60 cools the raw material having a high
temperature and the solvent that are supplied from the
temperature-retaining tank 20, and then supplies them to a stirrer
10. For example, if a reaction is conducted in the
temperature-retaining tank 20 at a temperature exceeding 80.degree.
C., the raw material or the like is cooled to 80.degree. C. or
less, and then sent to the stirrer 10.
[0139] The solid electrolyte obtained by the production method of
the invention can be used as a solid electrolyte layer or as a
solid electrolyte to be mixed with a cathode mix of an all-solid
lithium secondary battery, or the like.
[0140] For example, in addition to a cathode and an anode, by
forming a layer comprising the solid electrolyte obtained by the
production method of the invention between the cathode and the
anode, an all-solid lithium secondary battery is obtained.
Third Invention
Method for Producing an Ionic Conductive Substance
[0141] The method for producing an ionic conductive substance of
the invention comprises a first process in which one or more
compounds selected from phosphor sulfide, germanium sulfide,
silicon sulfide and boron sulfide (hereinafter referred to as the
"first sulfide") and an alkali sulfide metal compound or an
alkaline earth metal sulfide (hereinafter referred to as the
"second sulfide") are brought into contact in a solvent with
stirring, and the contact is completed under predetermined
conditions, and a second process in which a product obtained in the
first process is subjected to a mechanical treatment.
[0142] In the first process, an ionic conductive substance can be
produced by allowing the first sulfide and the second sulfide to
contact while stirring in a solvent. In the contact reaction, the
ionic conductive substance may contain the first sulfide and/or the
second sulfide that remain unreacted. In such a case, in the method
for producing an ionic conductive substance of the invention
(hereinafter, simply referred to as the "production method of the
invention"), by subjecting a product obtained in the first process
to a mechanical treatment, the reaction of the first sulfide and/or
the second sulfide that remain unreacted can be completed.
[0143] By pulverizing not the raw material but the product (an
ionic conductive substance containing an unreacted raw material),
the product is pulverized while proceeding a reaction. Therefore,
the control of the grain diameter and the control for completing
the reaction can be conducted simultaneously.
[0144] As the method for producing a sulfide-based solid
electrolyte, in addition to the methods disclosed in the
above-mentioned WO2005/119706 or the JP-A-H11-134937, a method
disclosed in WO2009/047977 in which a solid electrolyte is produced
by reacting the raw material while stirring in a hydrocarbon
solvent can be given. Further, JP-A-2010-140893 discloses a method
for producing a solid electrolyte using a solid electrolyte
production apparatus having a pulverizing synthesis means, in which
a raw material containing lithium sulfide and other sulfides is
reacted in a hydrocarbon-based solvent.
[0145] However, in the method disclosed in WO2009/047977, in order
to obtain a highly-pure sulfide-based solid electrolyte, it is
required to finely pulverize lithium sulfide or the like as the raw
material by applying a mechanical force, and at the same time, a
long period of time is required to produce a sulfide-based solid
electrolyte. Further, in JP-A-2010-140893, since it is required to
move the pulverizing synthesis means all the time, although the
required amount of energy becomes small as compared with the
technology disclosed in Patent Document 2, a large amount of energy
is still required.
[0146] Therefore, it is required to reduce the amount of energy
used in the production as compared with the production method
disclosed in JP-A-2010-140893, as well as to shorten the production
time as compared with the production method disclosed in
WO2009/047977.
[0147] It is possible to produce only in the first process an ionic
conductive substance that does not contain the first sulfide and
the second sulfide remained. However, since no mechanical energy is
exerted only by the contact reaction, a significantly long reaction
time is required.
[0148] The mechanical treatment in the second process is to exert
mechanical energy which is large enough to pulverize the raw
material by means of a milling apparatus, and is different from the
stirring in the first process. The first and second processes are
conducted in a batch-wise manner.
[0149] In the invention, by conducting the first process, an ionic
conductive substance in which the first sulfide and/or the second
sulfide remain unreacted can be produced, and by conducting the
second process, an ionic conductive substance in which no first
sulfide and second sulfide remain unreacted can be produced while
shortening the reaction time.
[0150] Even though the raw material is pulverized, as compared with
a production method in which the raw material is pulverized and
only the first process is conducted, by conducting both the first
process and the second process, the production time can be
shortened.
[0151] Hereinbelow, each process will be explained.
[First Process]
(1) First Sulfide
[0152] A first sulfide is one or more compounds selected from
phosphor sulfide, germanium sulfide, silicon sulfide and boron
sulfide. Preferably, the first sulfide is phosphor sulfide, with
phosphorus pentasulfide being more preferable.
[0153] As the first sulfide, a commercially-available product can
be used. However, it is preferred that it have a high purity.
[0154] When the first sulfide is phosphorus pentasulfide
(P.sub.2S.sub.5), no specific restrictions are imposed on
phosphorous pentasulfide as long as it is produced and sold on the
industrial basis. The purity of phosphorous pentasulfide is
preferably 95% or more, with 99% or more being further
preferable.
[0155] The molecular formula of phosphorus pentasulfide
(P.sub.2S.sub.5) is P.sub.4S.sub.10, but here, it is taken as
P.sub.2S.sub.5. Therefore, in Examples or the like, phosphorus
pentasulfide is described to have a molecular weight of 222.3.
[0156] Instead of P.sub.2S.sub.5, phosphor (P) as a simple
substance and sulfur (S) as a simple substance having a
corresponding molar ratio can be used. No specific restrictions are
imposed on the phosphor (P) as a simple substance and sulfur (S) as
a simple substance as long as they are produced and sold on the
industrial basis.
(2) Second Sulfide
[0157] A second sulfide is an alkali metal sulfide compound or an
alkaline earth metal sulfide. Specific examples of the alkali metal
sulfide compound or the alkaline earth metal sulfide include
lithium sulfide, sodium sulfide, potassium sulfide, rubidium
sulfide, cesium sulfide, beryllium sulfide, magnesium sulfide,
calcium sulfide, strontium sulfide, barium sulfide or the like. Of
these, lithium sulfide and sodium sulfide are preferable, with
lithium sulfide being particularly preferable.
[0158] If the second sulfide is lithium sulfide, no specific
restrictions are imposed. For example, commercially-available
lithium sulfide can be used. Highly-pure lithium sulfide is
preferable.
[0159] As for lithium sulfide, the total content of lithium salts
of a sulfur oxide is preferably 3.0 mass % or less, more preferably
2.5 mass % or less. The content of lithium N-methylaminobutyrate is
preferably 0.15 mass % or less, more preferably 0.1 mass % or less.
The content of lithium hydroxide is preferably 4.0 mass % or less,
more preferably 3.0 mass % or less. The content of lithium
carbonate is preferably 2.0 mass % or less, more preferably 1.0
mass % or less. The content of lithium hydrogen sulfide is
preferably 2.0 mass % or less, more preferably 1.0 mass % or less.
The total content of metals other than lithium, i.e. sodium,
potassium, magnesium, iron or the like is preferably 1.0 mass % or
less, with 0.1 mass % being more preferable.
[0160] Lithium sulfide as the second sulfide can be produced by the
following NMP method (A) or the hydrocarbon-based organic solvent
method (B). The resulting lithium sulfide may further be subjected
to a pulverization treatment (C).
(A) NMP Method
[0161] As for the method for producing lithium sulfide, no specific
restrictions are imposed as long as the amount of impurities can be
at least reduced. For example, it can be obtained by purifying
lithium sulfide produced by the following methods a to c. Of the
following methods, the method a or b is particularly
preferable.
a. A method in which lithium hydroxide and hydrogen sulfide are
reacted at 0 to 150.degree. C. in a non-protonic organic solvent to
form lithium hydrogen sulfide. Then, this reaction solution is
subjected to hydrodesulfurization at 150 to 200.degree. C. (see
JP-A-H07-330312). b. A method in which lithium hydroxide and
hydrogen sulfide are reacted at 150 to 200.degree. C. to directly
form lithium sulfide (see JP-A-H07-330312). c. A method in which
lithium hydroxide and a gaseous sulfur source are reacted at a
temperature of 130 to 445.degree. C. (see JP-A-H09-283156).
[0162] No specific restrictions are imposed on the method for
purification of lithium sulfide obtained as mentioned above. As the
preferable purification method, a purification method disclosed in
WO2005/40039 can be given. Specifically, lithium sulfide obtained
as above is washed at a temperature of 100.degree. C. or more by
using an organic solvent.
[0163] It is preferred that the organic solvent used for the
washing be a non-protonic polar solvent. Further, it is more
preferred that the non-protonic organic solvent used in the
production of lithium sulfide be the same as that used for the
washing.
[0164] As the non-protonic polar organic solvent preferably used in
the washing, a non-protonic polar organic compound such as an amide
compound, a lactam compound, a urea compound, an organic sulfur
compound and a cyclic organic phosphor compound or the like can be
given. These solvents can preferably be used as a single solvent or
a mixed solvent. In particular, N-methyl-2-pyrollydone (NMP) is
selected as a good solvent.
[0165] The amount of the organic solvent used in the washing is not
particularly restricted, and the frequency of the washing is not
particularly restricted. However, it is preferable to conduct
washing twice or more. It is preferred that washing be conducted
under an inert gas such as nitrogen and argon.
[0166] By drying the washed lithium sulfide at a temperature which
is equal to or higher than the boiling point of the organic solvent
used for washing in an inert gas atmosphere such as nitrogen under
normal pressure or reduced pressure for 5 minutes or more,
preferably about 2 to 3 hours, purified lithium sulfide can be
obtained.
(B) Hydrocarbon-Based Organic Solvent Method
[0167] Lithium hydroxide and hydrogen sulfide are reacted by
blowing a hydrogen sulfide gas to a slurry composed of lithium
hydroxide and a hydrocarbon-based solvent. The reaction is
continued while removing water generated by the reaction from the
slurry. After the water content in the reaction system is
substantially removed, blowing of an inert gas is stopped, whereby
lithium sulfide can be produced (JP-A-2010-163356).
[0168] Lithium sulfide prepared by the hydrocarbon-based organic
solvent method may be used as the second sulfide after drying once.
Alternatively, it may be used as the second sulfide in the state of
a slurry solution.
(C) an Increase in the Specific Surface Area of Lithium Sulfide
[0169] As for lithium sulfide, one obtained by the above-mentioned
method can be directly used. Alternatively, lithium oxide may be
subjected to a treatment (modification treatment) for increasing
the specific surface area of lithium sulfide by the technique
mentioned below.
[0170] Further, by conducting a modification treatment, there are
advantages that the specific surface area of lithium sulfide is
increased and the particle size is also decreased.
[0171] In addition, by pulverizing lithium sulfide, it is possible
to shorten the time of the first process. Further, it is supposed
that the reaction also proceeds inside lithium sulfide with a
decrease in particle size of lithium oxide.
[0172] As for the method for increasing the specific surface area
of lithium sulfide, the same modification method as the
above-mentioned second invention can be mentioned.
(3) Production of an Ionic Conductive Substance
[0173] By allowing the first sulfide to contact with the second
sulfide in a solvent with stirring, an ionic conductive substance
can be synthesized.
[0174] The contact can be conducted in an organic solvent. The
organic solvent is preferably a non-aqueous solvent. Specific
examples of the non-aqueous solvent include hexane, heptane,
octane, toluene, xylene, ethyl benzene, cyclohexane, methyl
cyclohexane and petroleum ether.
[0175] As for the mixing ratio of the first sulfide and the second
sulfide, in the case where the first sulfide is phosphorous sulfide
and the second sulfide is lithium sulfide, for example, they are
mixed such that the amount ratio becomes 60:40<Li:P.ltoreq.85:15
(molar ratio), preferably 65:35<Li:P.ltoreq.0.83:17 (molar
ratio), further preferably 67:33<Li:P.ltoreq.81:19 (molar
ratio).
[0176] If the mixing ratio is outside this range, the ionic
conductivity of the electrolyte may be lowered.
[0177] An example in which the first sulfide is phosphorous sulfide
and the second sulfide is lithium sulfide is given above. However,
the same can be applied to a combination of other first sulfides
and other second sulfides.
[0178] As for the concentration of the contact reaction solution,
the amount of a solid component as the reactive substrate (the
first sulfide and the second sulfide) relative to the reaction
solvent is preferably 0.1 to 70 wt %, more preferably 0.5 to 50 wt
%.
[0179] If the concentration of the reactive substrate in the
solvent exceeds 70 wt %, homogenous stirring may become difficult
by normal stirring. On the other hand, if the concentration of the
reactive substrate in the solvent is less than 0.1 wt %, the
productivity may be lowered.
[0180] The contact reaction temperature is 50 to 210.degree. C.,
for example, preferably 60 to 180.degree. C., with 100 to
180.degree. C. being more preferable.
[0181] If the reaction temperature exceeds 210.degree. C., since
the reaction and the crystallization proceed simultaneously, the
reaction does not proceed, whereby the amount of remaining sulfide
such as remaining lithium sulfide may become large. If the
temperature is less than 50.degree. C., the reaction may not
proceed smoothly.
[0182] It is preferred that the contact reaction be conducted in
the atmosphere of an inert gas such as nitrogen and argon. The dew
point of the inert gas is preferably -20.degree. C. or less, with
-40.degree. C. or less being particularly preferable. The pressure
is normally from normal pressure to 100 MPa, preferably from normal
pressure to 20 MPa.
[0183] The contact reaction time is 1 to 200 hours, for example,
with 4 to 180 hours being preferable.
[0184] If the reaction time is less than 1 hour, the reaction may
not proceed. If the reaction time is too long, the ionic
conductivity may be lowered, although the reason therefor is
unclear.
[0185] In the first process, the contact is completed under
prescribed conditions.
[0186] The prescribed conditions are as follows, for example. The
first process is conducted for 50% or more and 99% or less,
preferably 60% or more and 98% or less of the total of the reaction
time of the first process and the reaction time of the second
process, and for the rest of the time, the second process is
conducted or the second process and the third process are conducted
repeatedly.
[Second Process]
[0187] In the second process of the production method of the
invention, the product obtained in the first process is subjected
to a mechanical treatment.
[0188] It is preferred that the mechanical treatment mean that the
product obtained in the first step be subjected to a mechanical
milling treatment in a solvent. As for the solvent used in the
mechanical milling, the same solvent as that used in the first
process can be used. Therefore, the transfer from the first process
to the second process can be realized by subjecting a slurry
solution containing the product of the first process to a
mechanical treatment as it is.
[0189] It is also possible to conduct transfer by drying the slurry
solution to obtain dry powder of the product, followed by addition
of a solvent.
[0190] Alternatively, the slurry solution may be dried to obtain
dry power of the product, and the dry power may be subjected to a
mechanical milling treatment without adding a solvent.
[0191] Various types of pulverization methods can be used for the
mechanical milling treatment. It is particularly preferable to use
a planetary ball mill. In a planetary ball mill, while a pot is
rotating, the table is revolving, whereby a significantly high
impact energy can be generated efficiently. A beads mill is also
preferable.
[0192] The rotation speed and the rotation time of the mechanical
milling treatment are not particularly restricted. However, the
higher the rotation speed is, the higher the formation speed of a
glass-like electrolyte. A longer rotation time leads to a higher
conversion ratio of the raw material to a glass-like
electrolyte.
[0193] However, if the rotation speed of the mechanical milling
treatment is high, a heavy burden may be imposed on a pulverizer.
If the rotation time is prolonged, production of a glass-like
electrolyte takes time.
[0194] For example, if a planetary ball mill is used, it suffices
to conduct rotation at a speed of 250 rpm or more and 300 rpm or
less for 5 minutes or more and 50 hours or less. A more preferable
reaction time is 10 minutes or more and 40 hours or less.
[0195] If a beads mill is used, for example, the rotation is
conducted at a speed of 100 rpm or more and 10000 rpm or less for 5
minutes or more and 24 hours or less. A more preferable reaction
time is 10 minutes or more and 12 hours or less.
[0196] In the second process, by conducting a mechanical milling
treatment preferably in the presence of a solvent, the treatment
time can be shortened. Heating can be conducted from 20.degree. C.
to 200.degree. C., according to need. A preferable heating
temperature is 20.degree. C. or more and 80.degree. C. or less,
with 30.degree. C. or more and 80.degree. C. or less being more
preferable.
[0197] If heating is conducted at a temperature of 80.degree. C. or
less, the wear of the ball of the ball milling machine can be
prevented.
[0198] Further, by conducting a mechanical milling treatment in the
presence of a solvent, granulation at the time of the treatment can
be suppressed, whereby the synthesis reaction can be promoted
efficiently. As a result, an ionic conductive substance with a high
degree of homogeneity and has a low content of the raw material
remains unreacted. In addition, adhesion of the raw material or the
reaction product to the apparatus wall or the like can be
prevented, and as a result, the yield of the product can be
improved.
[0199] By conducting the above-mentioned mechanical milling
treatment, the ionic conductive substance of the invention can be
obtained.
[0200] If the mechanical treatment is a mechanical milling
treatment in a solvent, when the resulting ionic conductive
substance is used in the state of a slurry solution, after the
reaction, it may be used after removing a supernatant or after
adding a non-aqueous solvent and transferring to other
container.
[0201] When the ionic conductive substance is used as dry powder,
it is required to remove the solvent. This can be conducted in the
vacuum or in the atmosphere of nitrogen at room temperature or
under heated conditions. If the removal of the solvent is conducted
under heated conditions, the heating temperature is 40 to
200.degree. C., for example, preferably 50 to 160.degree. C. If the
temperature is higher than these, crystallization may proceed to
deteriorate the conductivity performance. Further, if the
temperature is low, the remaining solvent may not be removed
completely.
[0202] By the above-mentioned removal treatment, the amount of the
remaining solvent in the product is 5 wt % or less, for example,
preferably 3 wt % or less. If the amount of the remaining solvent
is large, a non-conductor which functions as a resistance component
is formed in the electrolyte, thereby leading to lowering of
battery performance.
[Third Process]
[0203] According to the production method of the invention, it is
possible to produce an ionic conductive substance only by the first
process and the second process. However, it may further include the
third process.
[0204] In the third process, the product which has been subjected
to a mechanical treatment in the second process is stirred in a
solvent.
[0205] Here, the third process is a process in which a product
obtained in the second process (including a product containing an
unreacted raw material) is placed in a container or the like
together with a solvent without being subjected to a mechanical
treatment, and stirring or the like is conducted to cause the raw
material remained unreacted in the product to be reacted.
[0206] The same solvent as that used in the first process can be
used in the third process, and the stirring in the third process
can be conducted under the similar stirring conditions (contact
temperature, contact time) as those in the first process. That is,
the solvent and stirring conditions used in the third process may
be completely the same as those in the first process. The apparatus
and conditions in the first process can be used as they are.
[0207] In the production method of the invention, the product which
has been stirred in the above-mentioned third process is preferably
further subjected to a mechanical treatment in the second process.
The third process and the second process are repeated alternately.
By such repetition, an ionic conductive substance having only a
small amount of an unreacted material can be produced.
[0208] No specific restrictions are imposed on the number of the
repetition of the third process and the second process, and these
processes may be repeated appropriately.
[0209] The repetition of the third process and the second process
can be implemented by using an apparatus shown in FIG. 4 or FIG. 5,
which is explained with reference to the second invention.
Specifically, the second process can be implemented by the
pulverizer 10 and the third process can be implemented by the
temperature-retaining tank 20.
[Ionic Conductive Substance]
[0210] The ionic conductivity of the ionic conductive substance
obtained by the production method of the invention is preferably
1.times.10.sup.-6 S/cm or more, with 5.times.10.sup.-6 S/cm being
more preferable.
[0211] In the invention, the ionic conductivity is a value obtained
by the alternating current impedance method. The details thereof
will be explained in Examples.
[0212] The average particle diameter of the ionic conductive
substance is 50 .mu.m or less and 0.1 .mu.m or more, preferably 30
.mu.m or less and 0.2 .mu.m or more. If the average particle
diameter is larger than this, when a battery is produced, the
thickness of the electrolyte layer may become un-uniform, causing
short circuit.
[0213] The above-mentioned particle diameter can be measured by
means of a laser. It is desirable to conduct such measurement
directly in the state of a slurry, without passing through the
dried state. Once drying is conducted, aggregation of particles may
be generated, leading to an apparently large particle size.
[0214] By crystallizing by heating, an ionic conductive substance
(ionic conductive glass) having a higher ionic conductivity (e.g. a
solid electrolyte obtained from a raw material of which the
Li.sub.2S:P.sub.2S.sub.5 (molar ratio) is 68:32 to 72:28) may be
obtained.
[0215] The heating temperature is 80.degree. C. or more and
400.degree. C. or less, preferably 170.degree. C. or more and
380.degree. C. or less, with 180.degree. C. or more and 360.degree.
C. or less being more preferable. If the heating temperature is
less than 80.degree. C., crystallized glass having a high
crystallization degree may not be obtained. If the heating
temperature exceeds 400.degree. C., crystallized glass having a low
crystallization degree may be generated.
[0216] The above-mentioned heating may be conducted for an ionic
conductive substance in the state of a slurry.
[0217] It is preferred that the ionic conductive glass be heated at
a dew point of -40.degree. C. or less, more preferably at a dew
point of -60.degree. C. or less.
[0218] The pressure at the time of heating may be normal pressure
or reduced pressure.
[0219] The atmosphere may be air or an inert gas.
[0220] The heating time may preferably be 0.1 hour or more and 24
hours or less, more preferably 0.5 hours or more and 12 hours or
less.
[0221] By the above-mentioned heating treatment, a crystallized
ionic conductive substance can be obtained.
[0222] The crystallized ionic conductive substance may be totally
crystallized, or a part thereof may be crystallized and the
remaining part may be amorphous. A crystal substance which is
crystallized by the above-mentioned crystallization method is
supposed to have a higher ionic conductivity than that of an
amorphous substance.
[0223] The crystallization degree of the crystallized ionic
substance is preferably 50% or more, more preferably 70% or more.
If 50% or more is crystallized, effects of improving ionic
conductivity by crystallization are further enhanced.
[0224] The above-mentioned ionic conductive substance and the
crystallized ionic conductive substance can be used as the material
for a battery.
[0225] In the first embodiment of the battery, it contains at least
one of the crystallized ionic conductive substance and the ionic
conductive substance. The crystallized ionic conductive substance
and the ionic conductive substance may be contained in the
electrolyte layer or in the electrode layer of the battery. They
may be contained in both of the electrolyte layer and the electrode
layer.
[0226] In another embodiment of the battery, it is produced by
using at least one of the crystallized ionic conductive substance
and the ionic conductive substance. The crystallized ionic
conductive substance and the ionic conductive substance may be used
in the electrolyte layer of the battery or in the electrode layer.
They may be used in both of the electrolyte layer and the electrode
layer.
[0227] For the constitutional elements of the battery (e.g. an
electrode active substance, a conductive assistant, a collector or
the like), known elements can be used. Elements which will be
invented in the future can also be applied.
[0228] As for the production method of the battery, a known
production method can be applied, and a production method which
will be invented later may also be applied.
EXAMPLES
Production Example 1
Production of Lithium Sulfide
[0229] In the atmosphere of nitrogen, 270 g of toluene as a
non-polar solvent was added to a 600 ml-separable flask. Then, 30 g
of lithium hydroxide (manufactured by Honjo Chemical Corporation)
was incorporated, and the resultant was retained at 95.degree. C.
while stirring at 300 rpm by means of a fullzone stirrer. While
blowing hydrogen sulfide at a supply speed of 300 ml/min, the
slurry was heated to 104.degree. C. From the separable flask, an
azeotropic gas of water and toluene was continuously discharged.
Dehydration was conducted by condensing this azeotropic gas by a
condenser placed outside the reaction system. During this time, the
same amount of toluene as that distilled off was continuously
supplied, the level of the reaction liquid was retained at a
constant level.
[0230] The amount of water in the condensed liquid was gradually
decreased. After 6 hours from the introduction of hydrogen sulfide,
distillation of water was no longer observed (the total water
amount was 22 ml). During the reaction, a state in which solids
were dispersed in toluene and stirred was kept, and there was no
water content separated from toluene. Thereafter, hydrogen sulfide
was changed to nitrogen, and nitrogen was circulated for one hour
at 300 ml/min. The solid matters were filtrated and dried to
obtained lithium sulfide as white powder.
[0231] The resulting powder was analyzed by the hydrochloric
titration and the silver nitrate nitration. It was found that the
purity of lithium sulfide was 99.0%. As a result of an X-ray
diffraction analysis, it was confirmed that no peak other than the
crystal pattern of lithium sulfide was observed. The average
particle size was 450 .mu.m (slurry solution).
[0232] The specific surface area of the resulting lithium sulfide
was measured by the BET method by using a nitrogen gas, by means of
AUTOSORB6 (manufactured by Sysmex Corporation), and was found to be
14.8 m.sup.2/g. The pore volume was measured by the same apparatus
for measuring the specific surface area. The pore volume was
obtained from the measurement point of a relative pressure of
P/P.sub.0 of 0.99 or more by interpolating to 0.99, and was found
to be 0.15 ml/g.
Production Example 2
Pulverization Treatment
[0233] 26 g of lithium sulfide obtained in Production Example 1 was
weighed in a Schlenk cocked-bottle in a glove box. In a nitrogen
atmosphere, 50 ml of dehydrated toluene (manufactured by Wako Pure
Chemical Industries, Ltd.) and 250 ml of dehydrated ethanol
(manufactured by Wako Pure Chemical Industries, Ltd.) were added in
this sequence, and the resultant was stirred by means of a stirrer
at room temperature for 24 hours. After the modification treatment,
the bath temperature was raised to 120.degree. C., and a hydrogen
sulfide gas was circulated at a rate of 200 ml/min for 90 minutes
to conduct a treatment. After the hydrogen sulfide gas treatment,
the solvent was distilled off in the atmosphere of nitrogen at room
temperature. Further, in the vacuum, drying was conducted for 2
hours to collect pulverized lithium sulfide.
[0234] The thus pulverized lithium sulfide was evaluated in the
same manner as in the Production Example 1. Lithium sulfide had a
purity of 97.2%, a lithium hydroxide content of 0.3%, an average
particle diameter of 9.1 .mu.m (un-dried slurry solution), a
specific surface area of 43.2 m.sup.2/g and a pore volume of 0.68
ml/g. The purity and the lithium hydroxide content were
quantitatively measured by the titration method. The reason that
the total of the analysis values was not 100% is that it contained
lithium carbonate, other ionic salts and a remaining solvent.
Production Example 3
Pulverization Treatment
[0235] Lithium sulfide produced in Production Example 1 was
pulverized in a nitrogen atmosphere by means of a jet mil apparatus
(manufactured by Aishin Nano Technologies, Co., Ltd.). The
collected lithium sulfide had a specific surface area of 20.0
m.sup.2/g, a particle size of 2.1 .mu.m and a pore volume of 0.17
ml/g.
Production Example 4
Production of Lithium Sulfide
[0236] Lithium sulfide was produced in accordance with the method
of the first embodiment (2-process method) disclosed in Japanese
Patent No. 3528866 (JP-A-H07-330312). Specifically, in a 10
L-autoclave provided with a stirring blade, 3326.4 g (33.6 mol) of
N-methyl-2-pyrrolidone (NMP) and 287.4 g (12 mol) of lithium
hydroxide were placed, stirred at 300 rpm, and the temperature was
elevated to 130.degree. C. After the heating, hydrogen sulfide was
blown to the liquid at a supply speed of 3 L/min for 2 hours.
Subsequently, this reaction liquid was heated in a nitrogen
atmosphere (200 cc/min), and the reacted lithium hydrogen sulfide
was hydrosulfurized, thereby to obtain lithium sulfide. As the
temperature was raised, water obtained as a by-product due to the
reaction of hydrogen sulfide and lithium hydroxide started to
evaporate. This water was condensed by means of a condenser and
withdrawn outside the reaction system. Simultaneously with
distillation off of the water outside the system, the temperature
of the reaction liquid was elevated. When the temperature reached
180.degree. C., the heating was stopped, and the temperature was
retained at constant. After the completion of the
hydrodesulfurization of lithium hydrogen sulfide (after about 80
minutes), the reaction was completed, whereby lithium sulfide was
obtained.
[Purification of Lithium Sulfide]
[0237] NMP in 500 mL of the slurry reaction solution (NMP-lithium
sulfide slurry) obtained above was subjected to decantation, and
100 mL of dehydrated NMP was added. The resulting mixture was
stirred at 105.degree. C. for about 1 hour. Further, 100 mL of NMP
was added, and the resultant was stirred at 105.degree. C. for
about 1 hour. At that temperature, NMP was subjected to
decantation. The similar operation was repeated four times in
total. After the completion of the decantation, in a nitrogen
atmosphere at 230.degree. C. (a temperature which is higher than
the boiling point of NMP), lithium sulfide was dried for 3 hours at
normal pressure. The content of impurities in the resulting lithium
sulfide was measured.
[0238] The content of each of sulfur oxides, i.e. lithium sulfite
(Li.sub.2SO.sub.3), lithium sulfide (Li.sub.2SO.sub.4) and lithium
thiosulfate (Li.sub.2S.sub.2O.sub.3) and lithium
N-methylaminobutyrate (LMAB) was quantitatively measured by the ion
chromatography method. As a result, it was found that the total
content of sulfur oxides was 0.13 mass % and the content of lithium
N-methylamino butyrate (LMAB) was 0.07 mass %.
[0239] The specific surface area and the pore volume of the
resulting lithium as measured by the BET method using a nitrogen
gas by using AUTOSORBE6.
The specific surface area and the pore volume were equal to or
lower than the measureable lowest limit (0.1 m.sup.2/g or less, and
the specific surface area was 0.001 ml/g or less). Measurement was
conducted by the krypton method capable of measuring a low surface
area, the low surface area was found to be 0.04 m.sup.2/g. The
particle diameter was 190 .mu.m.
Example of the First Invention
Example 1-1
[0240] As the raw material, 41.8 g (75 mol %) of Li.sub.2S in
Production Example 1 and 67.5 g (25 mol %) of P.sub.2S.sub.5
manufactured by Sigma-Aldrich Japan K.K. were used. These powders
were weighed in a dry box filled with nitrogen, and incorporated in
an alumina-made pot (6.7 L) used in a planetary ball mill together
with zirconia-made balls (only balls each having a diameter of 20
mm). The pot was completely sealed in the state where it was filled
with a nitrogen gas. This pot was installed in a planetary ball
mill machine, and, at the initial stage, milling was conducted at a
low speed (rotation: 85 rpm) for several minutes in order to fully
mix the raw material. Thereafter, the rotational speed was
gradually increased, and mechanical milling was conducted at 370
rpm for 120 hours.
[0241] The SEM photograph of the collected electrolyte glass is
shown in FIG. 3. In this photograph, an agglomerate of primary
particles having a diameter of 1 to 5 .mu.m or less was observed.
It can be understood that the average particle size does not exceed
10 .mu.m.
Comparative Example 1-1
[0242] An experiment was conducted in the same manner as in Example
1-1, except that 39.0 g (70 mol %) of Li.sub.2S produced in
Production Example 4 and 81.0 g (30 mol %) of P.sub.2S.sub.5
manufactured by Sigma-Aldrich Japan K.K. were used as the raw
material, and the pulverization time was changed to 40 hours.
Comparative Example 1-2
[0243] An experiment was conducted in the same manner as in
Comparative Example 1-1, except that the pulverization time was
changed to 280 hours. The ionic conductivity of the resulting glass
was found to be 2.0.times.10.sup.-4 S/cm.
[0244] The Raman spectra of glass particles obtained in Example 1-1
and Comparative Examples 1-1 and 1-2 were measured under the
following conditions.
[0245] Laser Raman measurement conditions:
[0246] Measurement apparatus: Almega manufactured by ThermoFisher
Scientific K.K.
[0247] Laser wavelength: 532 nm
[0248] Laser output: 10%
[0249] Aperture: 25 .mu.m .phi.
[0250] Exposure time: 10 seconds
[0251] Exposure frequency: 10
[0252] Objective lens: .times.100
[0253] Resolution: High (2400 lines/mm)
[0254] As for the Raman spectrum, measurement was conducted 5 times
after sealing the same lot sample in a Raman tube, while changing
the measurement position.
[0255] One example of the Raman spectrum of the glass particles of
Example 1-1 is shown in FIG. 1.
[0256] As for the measured spectrum, the spectrum was separated
into peaks by using a waveform analysis software (GRAMS Al,
manufactured by Thermo Scientific K.K.)
[0257] As the example of the spectrum which was separated into each
peak by using the waveform analysis software, the result of
Comparative Example 1-1 is shown in FIG. 2. The three separated
peaks in the original Raman spectrum show the peaks of
P.sub.2S.sub.7.sup.-4, PS.sub.4.sup.3- and P.sub.2S.sub.6.sup.4-,
in the order of height.
[0258] The average value of the area ratio and the standard
deviation of each peak separated is shown in Table 1.
TABLE-US-00001 TABLE 1 Example Standard 1-1 Area ratio (%)
deviation PS.sub.4.sup.3- 78.6 1.8 P.sub.2S.sub.7.sup.4- 15.6 2.6
P.sub.2S.sub.6.sup.4- 5.8 0.8 Com. Ex. Standard 1-1 Area ratio (%)
deviation PS.sub.4.sup.3- 28.1 6.1 P.sub.2S.sub.7.sup.4- 50.8 6.4
P.sub.2S.sub.6.sup.4- 21.1 7.8 Com. Ex. Standard 1-2 Area ratio (%)
deviation PS.sub.4.sup.3- 36.5 1.9 P.sub.2S.sub.7.sup.4- 46.4 3.7
P.sub.2S.sub.6.sup.4- 17.1 4.8
[0259] As for the glass particles obtained by conducting the sample
preparation of Example 1-1 and Comparative Example 1-1 five times
each, the ion conductivity was measured. The measurement results,
the average value thereof and the standard deviation are shown in
Table 2.
TABLE-US-00002 TABLE 2 Example 1-1 Com. Ex. 1-1 Ionic conductivity
3.86 .times. 10.sup.-4 1.04 .times. 10.sup.-4 (S/cm) 2.85 .times.
10.sup.-4 1.09 .times. 10.sup.-4 3.50 .times. 10.sup.-4 1.29
.times. 10.sup.-4 3.78 .times. 10.sup.-4 1.95 .times. 10.sup.-4
3.74 .times. 10.sup.-4 1.96 .times. 10.sup.-4 Average value 3.55
.times. 10.sup.-4 1.47 .times. 10.sup.-4 Standard 0.41 .times.
10.sup.-4 0.46 .times. 10.sup.-4 deviation
[0260] It can be understood that the standard deviation of the
ionic conductivity in Example 1-1 is smaller than that in
Comparative Example, reflecting the Raman spectrum. The reason
therefor is that the difference in standard deviation of ionic
conductivity shown in Table 2 is smaller than the Raman spectrum,
but the average value of the ionic conductivity in Examples is
high. When the standard deviation is obtained from the average
value, the standard variation is 12% in Examples and 31% in
Comparative Examples. This means that the variation in conductivity
performance has been improved by nearly 20%.
Example 1-2
Li/P Ratio 75/25 Mol
[0261] An apparatus 1 shown in FIG. 4 was used. As the pulverizer
10, Star mill MINICER (manufactured by Ashizawa Finetech Ltd. (0.15
L) (beads mill) was used. 450 g of 0.5 mm-diameter zirconia balls
were placed. As a temperature-retaining tank 20, a 1.5 L glass-made
reactor provided with a stirrer was used.
[0262] To 42.1 g (75 mol %) of lithium sulfide produced in
Production Example 1 and 67.9 g (25 mol %) of P.sub.2S.sub.5
(manufactured by Sigma-Aldrich Japan K.K.), 1100 g of dehydrated
toluene was added. The mixture was charged in the
temperature-retaining tank and the mill. The contents were
circulated by means of a pump at a flow rate of 400 mL/min, and,
and the temperature-retaining tank was heated to 80.degree. C.
[0263] By passing through hot water by external circulation in
order to hold the temperature of the liquid inside at 70.degree.
C., and the mill body was operated at a circumferential speed of 8
m/s. The reaction time was 40 hours. A solid portion of the slurry
containing the solid electrolyte obtained after the reaction was
separated, dried under vacuum to obtain a powdery solid
electrolyte. For the resulting powder, an XRD spectrum was obtained
by the X-ray diffraction measurement, and it was confirmed that the
peak of lithium sulfide as the raw material disappeared. The ionic
conductivity of this solid electrolyte was measured and found to be
2.2.times.10.sup.-4 S/cm.
[0264] For the solid electrolyte thus obtained, the Raman spectrum
was measured in the same manner as in Example 1-1. Further, the
amount of toluene contained in the solid electrolyte was measured.
The results are shown in Table 3.
[0265] The amount of toluene was measured as follows.
[0266] The dry solid electrolyte was weighed in a nitrogen
atmosphere. To this, dehydrated methanol was added to obtain a
homogeneous solution, and the solution was subjected to gas
chromatography.
Example 1-3
Li/P Ratio 75/25 Mol
[0267] A reaction was conducted in the same manner as in Example
1-2, except that lithium sulfide produced in Production Example 2
was used instead of lithium sulfide produced in Production Example
1. The reaction time was 18 hours. For the powder obtained after
the reaction, an XRD spectrum was obtained by an X-ray diffraction
measurement. It was confirmed that the peak of lithium sulfide as
the raw material disappeared. The ionic conductivity of the
resulting solid electrolyte was found to be 3.0.times.10.sup.-4
S/cm.
[0268] The resulting solid electrolyte was evaluated in the same
manner as in Example 1-2. The results are shown in Table 3.
Example 1-4
Li/P Ratio 75/25 Mol
[0269] A reaction was conducted in the same manner as in Example
1-2, except that lithium sulfide produced in Production Example 3
was used instead of lithium sulfide produced in Production Example
1. The reaction time was 18 hours. For the powder obtained after
the reaction, an XRD spectrum was obtained by an X-ray diffraction
measurement. It was confirmed that the peak of lithium sulfide as
the raw material disappeared. The ionic conductivity of the
resulting solid electrolyte was found to be 2.7.times.10.sup.-4
S/cm.
[0270] The resulting solid electrolyte was evaluated in the same
manner as in Example 1-2. The results are shown in Table 3.
Example 1-5
Li/P Ratio 80/20 Mol
[0271] The same apparatus as that in Example 1-2 was used. To 42.1
g (75 mol %) of lithium sulfide produced in Production Example 2
and 67.9 g (25 mol %) of P.sub.2S.sub.5 (manufactured by
Sigma-Aldrich Japan, K.K.), 1100 g of dehydrated toluene was added.
The mixture was charged in the temperature-retaining tank and the
mill.
[0272] The contents were circulated by means of a pump at a flow
rate of 400 mL/min, and, and the temperature-retaining tank was
heated to 80.degree. C.
[0273] By passing through hot water by external circulation in
order to hold the temperature of the liquid inside at 70.degree.
C., and the mill body was operated at a circumferential speed of 8
m/s. The reaction time was 20 hours. A solid portion of the slurry
containing the solid electrolyte obtained after the reaction was
separated, dried under vacuum to obtain a powdery solid
electrolyte. For the resulting powder, an XRD spectrum was obtained
by the X-ray diffraction measurement, and it was confirmed that the
peak of lithium sulfide as the raw material disappeared. The ionic
conductivity of this solid electrolyte was measured and found to be
2.8.times.10.sup.-4 S/cm.
[0274] For the solid electrolyte thus obtained, the Raman spectrum
was measured in the same manner as in Example 1-2. Further, the
amount of toluene contained in the solid electrolyte was measured.
The results are shown in Table 3.
TABLE-US-00003 TABLE 3 Amount of Area ratio (%) Standard deviation
toluene PS.sub.4.sup.3- P.sub.2S.sub.7.sup.4- P.sub.2S.sub.6.sup.4-
PS.sub.4.sup.3- P.sub.2S.sub.7.sup.4- P.sub.2S.sub.6.sup.4- wt %
Example 1-2 80 11.6 8.4 1.1 0.9 0.9 2.2 Example 1-3 80.6 11.4 8 1.2
0.8 0.8 2.4 Example 1-4 79.8 12.3 7.9 1 0.8 0.7 2.5 Example 1-5
83.2 8 8.9 1.2 1.5 0.4 1.9
Examples of the Second Invention
Referential Example 2-1
Li/P Ratio 70/30 Mol
[0275] An apparatus 1 shown in FIG. 4 was used. As the pulverizer
10, Star mill MINICER (manufactured by Ashizawa Finetech Ltd. (0.15
L) (beads mill) was used. 450 g of 0.5 mm-diameter zirconia balls
were placed. As a temperature-retaining tank 20, a 1.5 L glass-made
reactor provided with a stirrer was used.
[0276] To 39.05 g (70 mol %) of lithium sulfide produced in
Production Example 1 and 80.95 g (30 mol %) of P.sub.2S.sub.5
(manufactured by Sigma-Aldrich Japan K.K.), 1100 g of dehydrated
toluene was added. The mixture was charged in the
temperature-retaining tank and the mill.
[0277] The contents were circulated by means of a pump at a flow
rate of 400 mL/min, and the temperature-retaining tank was heated
to 80.degree. C.
[0278] By passing through hot water by external circulation in
order to hold the temperature of the liquid inside at 70.degree.
C., and the mill body was operated at a circumferential speed of 8
m/s. The reaction time was 10 hours. A solid portion of the slurry
containing the solid electrolyte obtained after the reaction was
separated, dried under vacuum to obtain a powdery solid
electrolyte. For the resulting powder, an XRD spectrum was obtained
by the X-ray diffraction measurement, and it was confirmed that the
peak of lithium sulfide as the raw material disappeared.
[0279] The ionic conductivity of this solid electrolyte was
measured and found to be 1.6.times.10.sup.-4 S/cm.
[0280] Further, the solid electrolyte was subjected to a heat
treatment at 300.degree. C. for 2 hours, whereby glass ceramic
electrolyte was obtained. The ionic conductivity was
2.0.times.10.sup.-3 s/cm.
[0281] The ionic conductivity was measured by the following
method.
[0282] A sulfide-based solid electrolyte was charged in a tablet
molding machine. A pressure of 4 to 6 MPa was applied to obtain a
molded product. Further, an electrode mixture obtained by mixing
carbon and glass ceramic electrolyte at a weight ratio of 1:1 was
put on the both sides of the molded product. A pressure was again
applied by the tablet molding machine, whereby a molded product
(diameter: about 10 mm, thickness: about 1 mm) was produced. For
this molded product, the ionic conductivity was measured by the
alternating current impedance method. As the value of the ionic
conductivity, a numerical value at 25.degree. C. was used.
[0283] The X-ray diffraction measurement of the resulting solid
electrolyte was conducted by means of an X-ray generating apparatus
(Ultima-Ill manufactured by Rigaku Corporation)
(CuK.alpha.:.DELTA.=1.5418 .ANG.).
Referential Example 2-2
Li/P Ratio 70/30 Mol
[0284] A reaction was conducted in the same manner as in
Referential Example 2-1, except that lithium sulfide produced in
Production Example 2 was used instead of lithium sulfide produced
in Production Example 1. The reaction time was 6 hours. For the
powder obtained after the reaction, an XRD spectrum was obtained by
an X-ray diffraction measurement. It was confirmed that the peak of
lithium sulfide as the raw material disappeared. The ionic
conductivities of the solid electrolyte and the glass ceramic
electrolyte were found to be 1.7.times.10.sup.-4 S/cm and
2.1.times.10.sup.-3 S/cm.
Referential Example 2-3
Li/P Ratio 70/30 Mol
[0285] A reaction was conducted in the same manner as in
Referential Example 2-1, except that lithium sulfide produced in
Production Example 3 was used instead of lithium sulfide produced
in Production Example 1. The reaction time was 6 hours. For the
powder obtained after the reaction, an XRD spectrum was obtained by
an X-ray diffraction measurement. It was confirmed that the peak of
lithium sulfide as the raw material disappeared. The ionic
conductivities of the solid electrolyte and the glass ceramic
electrolyte were found to be 1.6.times.10.sup.-4 S/cm and
1.9.times.10.sup.-3 S/cm.
Comparative Example 2-1
Li/P Ratio 70/30 Mol
[0286] A reaction was conducted in the same manner as in
Referential Example 2-1, except that lithium sulfide produced in
Production Example 4 was used instead of lithium sulfide produced
in Production Example 1. The reaction time was 12 hours. For the
powder obtained after the reaction, an XRD spectrum was obtained by
an X-ray diffraction measurement. It was confirmed that the peak of
lithium sulfide as the raw material disappeared. The ionic
conductivities of the solid electrolyte and the glass ceramic
electrolyte were found to be 1.2.times.10.sup.-4 S/cm and
1.8.times.10.sup.-3 S/cm.
Referential Example 2-4
Li/P Ratio 75/25 Mol
[0287] The same apparatus as that in Referential Example 1-2 was
used. To 42.1 g (75 mol %) of lithium sulfide produced in
Production Example 1 and 67.9 g (25 mol %) of P.sub.2S.sub.5
(manufactured by Sigma-Aldrich Japan K.K.), 1100 g of dehydrated
toluene was added. The mixture was charged in the
temperature-retaining tank and the mill.
[0288] The contents were circulated by means of a pump at a flow
rate of 400 mL/min, and the temperature-retaining tank was heated
to 80.degree. C.
[0289] By passing through hot water by external circulation in
order to hold the temperature of the liquid inside at 70.degree.
C., and the mill body was operated at a circumferential speed of 8
m/s. The reaction time was 40 hours. A solid portion of the slurry
containing the solid electrolyte obtained after the reaction was
separated, dried under vacuum to obtain a powdery solid
electrolyte. For the resulting powder, an XRD spectrum was obtained
by the X-ray diffraction measurement, and it was confirmed that the
peak of lithium sulfide as the raw material disappeared. The ionic
conductivity of this solid electrolyte was measured and found to be
2.2.times.10.sup.-4 S/cm.
Referential Example 2-5
Li/P Ratio 75/25 Mol
[0290] A reaction was conducted in the same manner as in
Referential Example 2-4, except that lithium sulfide produced in
Production Example 2 was used instead of lithium sulfide produced
in Production Example 1. The reaction time was 18 hours. For the
powder obtained after the reaction, an XRD spectrum was obtained by
an X-ray diffraction measurement. It was confirmed that the peak of
lithium sulfide as the raw material disappeared. The ionic
conductivity of the resulting solid electrolyte was
3.0.times.10.sup.-4 S/cm.
Referential Example 2-6
Li/P Ratio 75/25 Mol
[0291] A reaction was conducted in the same manner as in
Referential Example 2-4, except that lithium sulfide produced in
Production Example 3 was used instead of lithium sulfide produced
in Production Example 1. The reaction time was 18 hours. For the
powder obtained after the reaction, an XRD spectrum was obtained by
an X-ray diffraction measurement. It was confirmed that the peak of
lithium sulfide as the raw material disappeared. The ionic
conductivity of the resulting solid electrolyte was
2.7.times.10.sup.-4 S/cm.
Comparative Example 2-2
Li/P Ratio 75/25 Mol
[0292] A reaction was conducted in the same manner as in
Referential Example 2-4, except that lithium sulfide produced in
Production Example 4 was used instead of lithium sulfide produced
in Production Example 1. The reaction time was 40 hours. For the
powder obtained after the reaction, an XRD spectrum was obtained by
an X-ray diffraction measurement. The peak of lithium sulfide as
the raw material was observed, confirming that the lithium sulfide
remained. The ionic conductivity of the resulting solid electrolyte
was found to be 1.5.times.10.sup.-4 S/cm
Comparative Example 2-3
Li/P Ratio 75/25 Mol
[0293] 41.8 g (75 mol %) of Li.sub.2S in Production Example 1 and
67.5 g (25 mol %) of P.sub.2S.sub.5 (manufactured by Sigma-Aldrich
Japan K.K.) were weighed in a dry box filled with nitrogen, and
incorporated in an alumina-made pot (6.7 L) used in a planetary
ball mill together with zirconia-made balls (diameter: 20 mm). The
pot was completely sealed in the state where it was filled with a
nitrogen gas. This pot was installed in a planetary ball mill
machine, and, at the initial stage, milling was conducted at a low
speed (rotation: 85 rpm) for several minutes in order to fully mix
the raw material at room temperature. Thereafter, the rotational
speed was gradually increased, and mechanical milling was conducted
at 370 rpm for 120 hours at room temperature. For the powder
obtained after the reaction, an XRD spectrum was obtained by an
X-ray diffraction measurement. It was confirmed that the peak of
lithium sulfide as the raw material disappeared. The ionic
conductivity of the resulting solid electrolyte was found to be
3.5.times.10.sup.-4 S/cm.
Referential Example 2-7
Li/P Ratio 80/20 Mol
[0294] The same apparatus as that in Referential Example 2-1 was
used. To 42.1 g (75 mol %) of lithium sulfide produced in
Production Example 2 and 67.9 g (25 mol %) of P.sub.2S.sub.5
(manufactured by Sigma-Aldrich Japan K.K.), 1100 g of dehydrated
toluene was added. The mixture was charged in the
temperature-retaining tank and the mill.
[0295] The contents were circulated by means of a pump at a flow
rate of 400 mL/min, and the temperature-retaining tank was heated
to 80.degree. C.
[0296] By passing through hot water by external circulation in
order to hold the temperature of the liquid inside at 70.degree.
C., and the mill body was operated at a circumferential speed of 8
m/s. The reaction time was 20 hours. A solid portion of the slurry
containing the solid electrolyte obtained after the reaction was
separated, dried under vacuum to obtain a powdery solid
electrolyte. For the resulting powder, an XRD spectrum was obtained
by the X-ray diffraction measurement, and it was confirmed that the
peak of lithium sulfide as the raw material disappeared. The ionic
conductivity of this solid electrolyte was measured and found to be
2.8.times.10.sup.-4 S/cm.
[0297] The results of the above-mentioned Referential Examples and
Comparative Examples are shown in Table 4.
[0298] From Table 4, it can be understood that, when Referential
Examples and Comparative Examples in which the molar ratio of
Li.sub.2S and P.sub.2S.sub.5 was the same are compared, it is
understood that the reaction time was shorter in Referential
Examples. Further, the solid electrolytes obtained in Referential
Examples 2-1 to 2-7 and Comparative Examples 2-1 and 2-3 each had a
high ionic conductivity.
TABLE-US-00004 TABLE 4 Ref. Ref. Ref. Com. Ref. Ref. Ref. Com. Com.
Ref. Ex. 2-1 Ex. 2-2 Ex. 2-3 Ex. 2-1 Ex. 2-4 Ex. 2-5 Ex. 2-6 Ex.
2-2 Ex. 2-3 Ex. 2-7 Li.sub.2S:P.sub.2S.sub.5 70:30 70:30 70:30
70:30 75:25 75:25 75:25 75:25 75:25 80:20 (Molar ratio) Li.sub.2S
used as raw Pro. Pro. Pro. Pro. Pro. Pro. Pro. Pro. Pro. Pro.
material Ex. 1 Ex. 2 Ex. 3 Ex. 4 Ex. 1 Ex. 2 Ex. 3 Ex. 4 Ex. 1 Ex.
2 Specific surface 14.8 43.2 20.0 0.8 14.8 43.2 20 0.8 14.8 43.2
area of Li.sub.2S [m.sup.2/g] Pore volume of 0.15 0.68 0.17 0.0001
0.15 0.68 0.17 0.0001 0.15 0.68 Li.sub.2S [ml/g] Temperature of 80
80 80 80 80 80 80 80 -- 80 temperature- retaining apparatus
[.degree. C.] Circulation speed 400 400 400 400 400 400 400 400 --
400 [mL/min] Temperature of 70 70 70 70 70 70 70 70 Room 70 mill
[.degree. C.] tem- perature Circumferential 8 8 8 8 8 8 8 8 -- 8
speed (mill) [m/s] Reaction time [h] 10 6 6 12 40 18 18 40 120 20
Ionic conductivity 1.6 .times. 1.7 .times. 1.6 .times. 1.2 .times.
2.2 .times. 3.0 .times. 2.7 .times. 1.5 .times. 3.5 .times. 2.8
.times. [S/cm] 10.sup.-4 10.sup.-4 10.sup.-4 10.sup.-4 10.sup.-4
10.sup.-4 10.sup.-4 10.sup.-4 10.sup.-4 10.sup.-4 Ionic
conductivity after treating solid electrolyte 2.0 .times. 2.1
.times. 1. 9 .times. 1.8 .times. -- -- -- -- -- -- at 300.degree.
C. for 2 h 10.sup.-3 10.sup.-3 10.sup.-3 10.sup.-3 [S/cm]
Examples of the Third Invention
Referential Example 3-1
Preparation of Electrolyte Glass
[0299] A 0.5 L-autoclave provided with a stirrer was replaced with
nitrogen. In this autoclave, 12 g (75 mol %) of pulverized
Li.sub.2S produced in Production Example 2, 18.8 g (25 mol %) of
phosphorous pentasulfide and 300 mL of toluene which had been
dehydrated to have a water content of 10 ppm (manufactured by Wako
Pure Chemical Industries, Ltd) were charged. The resulting mixture
was subjected to a contact reaction while stirring at 150.degree.
C. for 72 hours, whereby an amorphous solid electrolyte slurry was
obtained.
[0300] Subsequently, this slurry solution was subjected to a
mechanical milling treatment for 3 hours by using the apparatus
shown in FIG. 1, to which a compact milling apparatus was attached.
The mechanical milling was conducted at an internal temperature of
the reaction tank of 80.degree. C., a circumferential temperature
of 12 m/s and a rotational speed of the beads mill of 3880 rpm.
After the completion of the mechanical milling, the resulting
amorphous solid electrolyte was taken out, and the solid portion
was separated and dried in vacuum, whereby an amorphous solid
electrolyte was obtained.
[0301] The resulting amorphous solid electrolyte was powdery, and
had an ionic conductivity of 2.53.times.10.sup.-4 S/cm. For the
resulting powder, an XRD spectrum was obtained by the X-ray
diffraction measurement, and it was confirmed that the peak of
lithium sulfide as the raw material disappeared. As a result of
measurement of the slurry solution of the amorphous solid
electrolyte, the average particle diameter was found to be 4.0
.mu.m.
Comparative Example 3-1
[0302] An amorphous solid electrolyte was produced in the same
manner as in Referential Example 3-1, except that the mechanical
milling was not conducted. That is, the amorphous solid electrolyte
slurry solution prior to the supply to the compact milling machine
was collected. A solid portion was separated, dried in vacuum to
obtain an amorphous solid electrolyte.
[0303] In an XRD spectrum of the resulting amorphous solid
electrolyte, a peak derived from lithium sulfide was observed. The
ionic conductivity was found to be 1.88.times.10.sup.-4 S/cm.
Comparative Example 3-2
[0304] A 0.5 L-autoclave provided with a stirrer was replaced with
nitrogen. In this autoclave, 12 g (75 mol %) of pulverized
Li.sub.2S produced in Production Example 2, 18.8 g (25 mol %) of
phosphorous pentasulfide and 300 mL of toluene which had been
dehydrated to have a water content of 10 ppm (manufactured by Wako
Pure Chemical Industries, Ltd.) were charged. The resulting mixture
was subjected to a contact reaction while stirring at 150.degree.
C. for 168 hours, whereby an amorphous solid electrolyte slurry was
obtained.
[0305] A solid portion of the resulting amorphous solid electrolyte
was separated, dried in vacuum to obtain an amorphous solid
electrolyte.
[0306] The resulting amorphous solid electrolyte was powdery, and
had an ionic conductivity of 1.22.times.10.sup.-4 S/cm. For the
resulting powder, an XRD spectrum was obtained by the X-ray
diffraction measurement, and it was confirmed that the peak of
lithium sulfide as the raw material remained. As a result of
measurement of the slurry solution of the amorphous solid
electrolyte, the average particle diameter was found to be 4.0
.mu.m.
Referential Example 3-2
[0307] The amorphous solid electrolyte slurry solution prior to the
mechanical milling treatment of Referantial Example 3-1 was dried
at 150.degree. C. for 2 hours, whereby amorphous solid electrolyte
powder ws obtained. 1.0 g of the resulting powder was pulverized at
370 rpm for 3 hours by means of a planetary ball mill, thereby to
obtain amorphous solid electrolyte powder.
[0308] The amorhous solid electrolyte powder after the
pulverization was 2.69.times.10.sup.-4 S/cm. For the resulting
powder, an XRD spectrum was obtained by the X-ray diffraction
measurement, and it was confirmed that the peak derived from
lithium sulfide disappeared.
Referential Example 3-3
[0309] Lithium sulfide produced in Production Example 1 was used
instead of lithium sulfide produced in Production Example 2, and
charged in an autoclave such that the amount ratio of lithium
sulfide and phosphorous pentasulfide became 70:30 (mol:mol).
Thereafter, an amorphous solid electrolyte was produced in the same
manner as in Referential Example 3-1, except that the contact
reaction time was changed from 72 hours to 24 hours. This
electrolyte slurry solution was subjected to a mechanical milling
treatment for 3 hours by using a compact milling apparatus as in
Referential Example 3-1. For the resulting amorphous solid
electrolyte, an XRD spectrum was obtained by the X-ray diffraction
measurement, and it was confirmed that the peak derived from
lithium sulfide disappeared. The ionic conductivity of this
amorphous solid electrolyte was 1.02.times.10.sup.-4 S/cm.
[0310] The resulting amorphous solid electrolyte was subjected to a
heat treatment at 300.degree. C. for 2 hours, thereby to obtain
glass ceramic electrolyte. The resulting glass ceramic electrolyte
has an ionic conductivity of 1.80.times.10.sup.-3 S/cm.
Comparative Example 3-3
[0311] An amorphous solid electrolyte was produced in the same
manner as in Referential Example 3-3, except that the mechanical
milling treatment was not conducted. Specifically, the amorphous
solid electrolyte slurry solution prior to the supply to the
compact milling apparatus was collected, and a solid portion was
separated, dried under vacuum to obtain an amorphous solid
electrolyte. For the resulting amorphous solid electrolyte, an XRD
spectrum was obtained by the X-ray diffraction measurement, and it
was confirmed that the peak derived from lithium sulfide as the raw
material was observed. The ionic conductivity of this amorphous
solid electrolyte was 5.57.times.10.sup.-5 S/cm.
[0312] The resulting amorphous solid electrolyte was subjected to a
heat treatment at 300.degree. C. for 2 hours, thereby to obtain
glass ceramic electrolyte. The resulting glass ceramic electrolyte
has an ionic conductivity of 1.07.times.10.sup.-3 S/cm.
Referential Example 3-4
[0313] Lithium sulfide produced in Production Example 1 was
pulverized in a nitrogen atmosphere by means of a jet mil apparatus
(manufactured by Aishin Nano Technologies, Co., Ltd.). The
collected lithium sulfide had a specific surface area of 20.0
m.sup.2/g and a particle size of 2.1 .mu.m.
[0314] An amorphous solid electrolyte was obtained in the same
manner as in Referential Example 3-1, except that lithium sulfide
pulverized by the jet mill apparatus was used instead of lithium
sulfide produced in Production Example 2.
[0315] The resulting amorphous solid electrolyte was powdery, and
had an ionic conductivity of 2.22.times.10.sup.-4 S/cm. For the
resulting powder, an XRD spectrum was obtained by the X-ray
diffraction measurement, and it was confirmed that the peak derived
from lithium sulfide disappeared.
Referential Example 3-5
[0316] The amorphous solid electrolyte slurry solution prior to the
mechanical milling treatment of Referantial Example 3-4 was dried
at 150.degree. C. for 2 hours, whereby amorphous solid electrolyte
powder ws obtained. 1.0 g of the resulting powder was pulverized at
370 rpm for 3 hours by means of a planetary ball mill, thereby to
obtain amorphous solid electrolyte powder was obtained.
[0317] The amorhous solid electrolyte powder after the
pulverization was 1.62.times.10.sup.-4 S/cm. For the resulting
powder, an XRD spectrum was obtained by the X-ray diffraction
measurement, and it was confirmed that the peak derived from
lithium sulfide disappeared.
Comparative Example 3-4
[0318] An amorphous solid electrolyte was produced in the same
manner as in Referential Example 3-4, except that the mechanical
milling treatment was not conducted. Specifically, the amorphous
solid electrolyte slurry solution prior to the supply to the
compact milling apparatus was collected, and a solid portion was
separated, dried under vacuum to obtain an amorphous solid
electrolyte. For the resulting amorphous solid electrolyte, an XRD
spectrum was obtained by the X-ray diffraction measurement, and it
was confirmed that the peak derived from lithium sulfide as the raw
material was partially observed. The ionic conductivity of this
amorphous solid electrolyte was 1.15.times.10.sup.-4 S/cm.
INDUSTRIAL APPLICABILITY
[0319] The glass according to the first invention can be preferably
used as an electrolyte or an electrode material of an all-solid
battery.
[0320] The production methods according to the second and third
inventions are preferable for the production of an ionic conductive
substance. The ionic conductive substance of the invention can be
used as the raw material of a secondary battery or the like.
[0321] Although only some exemplary embodiments and/or examples of
this invention have been described in detail above, those skilled
in the art will readily appreciate that many modifications are
possible in the exemplary embodiments and/or examples without
materially departing from the novel teachings and advantages of
this invention. Accordingly, all such modifications are intended to
be included within the scope of this invention.
[0322] The documents described in the specification and the
Japanese application specification claiming priority under the
Paris Convention are incorporated herein by reference in its
entirety.
* * * * *