U.S. patent application number 12/521654 was filed with the patent office on 2011-06-02 for all-solid-state lithium secondary battery.
Invention is credited to Yasushi Tsuchida.
Application Number | 20110129723 12/521654 |
Document ID | / |
Family ID | 39689902 |
Filed Date | 2011-06-02 |
United States Patent
Application |
20110129723 |
Kind Code |
A1 |
Tsuchida; Yasushi |
June 2, 2011 |
ALL-SOLID-STATE LITHIUM SECONDARY BATTERY
Abstract
A safe and highly-reliable all-solid-state lithium secondary
battery using a sulfide-based solid electrolyte material which can
restrain generation of hydrogen sulfide gas, in case a large amount
of water is entered into a battery case by an accident such as
submersion associated with a breakage of the container. An
all-solid-state lithium secondary battery using a sulfide-based
solid electrolyte material, wherein the battery has a metal salt
M-X comprising a metal element "M" and an anionic part "X" in a
battery case thereof, and further wherein a metal cation of the
metal salt M-X generated by disassociation caused with water can
react with a sulfide ion generated by a reaction between the
sulfide-based solid electrolyte material and the water.
Inventors: |
Tsuchida; Yasushi;
(Shizuoka-ken, JP) |
Family ID: |
39689902 |
Appl. No.: |
12/521654 |
Filed: |
January 25, 2008 |
PCT Filed: |
January 25, 2008 |
PCT NO: |
PCT/JP2008/051055 |
371 Date: |
November 1, 2010 |
Current U.S.
Class: |
429/163 |
Current CPC
Class: |
H01M 4/38 20130101; H01M
4/525 20130101; H01M 2300/0068 20130101; Y02E 60/10 20130101; H01M
10/052 20130101; Y02T 10/70 20130101; H01M 10/0562 20130101 |
Class at
Publication: |
429/163 |
International
Class: |
H01M 2/02 20060101
H01M002/02 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 13, 2007 |
JP |
2007-032561 |
Claims
1. An all-solid-state lithium secondary battery using a
sulfide-based solid electrolyte material, wherein the battery has a
metal salt M-X comprising a metal element "M" and an anionic part
"X" in a battery case thereof, and further wherein a metal cation
of the metal salt M-X generated by disassociation caused with water
can react with a sulfide ion generated by a reaction between the
sulfide-based solid electrolyte material and the water.
2. The all-solid-state lithium secondary battery according to claim
1, wherein the metal element "M" of the metal salt M-X is at least
one selected from the group consisting of Cd, Sn, Pb, Cu, Hg, Ag,
Al, Mn, Zn, Fe and Ni, and further wherein the anionic part "X" of
the metal salt M-X is at least one selected from the group
consisting of OH, SO.sub.4 and NO.sub.3.
Description
TECHNICAL FIELD
[0001] The present invention relates to a safe and highly-reliable
all-solid-state lithium secondary battery using a sulfide-based
solid electrolyte material which can restrain generation of
hydrogen sulfide gas.
BACKGROUND ART
[0002] With the recent rapid spread of information-related devices
and communication devices such as personal computers, video cameras
and cellular phones, developments of good secondary batteries, such
as lithium secondary batteries, as electric power supply for those
devices have been gaining recognition. Further, apart from the
technical fields of information-related devices and communication
devices, developments of high output and high capacity lithium
secondary batteries for electric vehicles and hybrid-power cars as
low-emission vehicles have been progressed in other fields such as
an automobile industry.
[0003] However, since current lithium secondary batteries
commercially-supplied use organic electrolyte solutions which have
combustible organic media as solvents, attaching of safety systems
to prevent temperature rising against short circuit and
improvements in their technical structures and materials to prevent
short circuit are required.
[0004] In contrast, since all-solid-state lithium secondary
batteries having their batteries made to an all-solid-state by
changing liquid electrolytes to solid electrolytes do not use
combustible organic solvents therein, their safety systems are
simplified. Accordingly, it is thought that such batteries are good
in reducing production costs and in enhancing productivity.
[0005] The above-mentioned all-solid-state lithium secondary
batteries are produced, for example, by: forming a pellet of
three-layer structure of cathode/solid electrolyte/anode by a
powder-molding method, inserting the respective battery into a
conventional coin-type battery case or a button type battery case,
and sealing the periphery thereof. Such all-solid-state lithium
secondary batteries tend to have a larger electrochemical
resistance and a smaller output current compare to lithium
secondary batteries using organic electrolyte solution, because
their members constituting the batteries, which are cathode, anode
and electrolyte, are all hard solid.
[0006] In light of this, it is preferable to use a material having
a high ion conductivity as an electrolyte in order to enhance an
output current of an all-solid-state lithium secondary battery.
Sulfide glasses such as Li.sub.2S--SiS.sub.2,
Li.sub.2S--B.sub.2S.sub.3, Li.sub.2S--P.sub.2S.sub.5 show a high
ion conductivity over 10.sup.-4 S/cm. Further, a material in which
a substance such as LiI, Li.sub.3PO.sub.4 added thereto also show a
high ion conductivity of about 10.sup.-3 S/cm. It is thought that
these glasses having sulfide as their main constituent show higher
ion conductivities compare to those of oxide glasses because
sulfide ions are ions having larger polarization compare to oxide
ions and sulfide ions have small electrostatic attractive force
with lithium ions.
[0007] However, with batteries using solid electrolyte materials
(sulfide-based solid electrolyte materials) which have the
above-mentioned sulfide as their main constituent, there is a risk
of leaking hydrogen sulfide gas to the outside of their battery
cases when water is entered into the battery cases and the gas is
generated. As hydrogen sulfide gas has pungent odor, prevention of
the gas leakage to the outside of the battery case is desired.
[0008] To respond such desire, a method of providing an adsorbent
to inside or outside of a battery case to absorb the gas generated
inside the battery is proposed. For example, in the Patent Document
1, hydrogen sulfide gas is absorbed by using adsorbents such as
zeolite, silica gel and activated carbon. However, since the
adsorbent such as zeolite, silica gel and activated carbon absorb
the gas using the surface adsorption, their adsorptive capacity are
lost when the surface is covered by a large amount of water or the
like. Therefore, there has been a problem of being incapable in
preventing the leakage of hydrogen sulfide gas generated because
their adsorptive capacity is lowered when a large amount of water
is entered into a battery by an accident such as submersion caused
by breakage of the container or being exposed to buckets of rain.
[0009] Patent Document 1: Japanese Patent Application Laid-Open
(JP-A) No. 2004-087152 [0010] Patent Document 2: JP-A No.
2004-227818 [0011] Patent Document 3: JP-A No. 2003-151558 [0012]
Patent Document 4: JP-A No. 2001-052733 [0013] Patent Document 5:
JP-A No. 11-219722 [0014] Patent Document 6: JP-A No.
2001-155790
DISCLOSURE OF INVENTION
Problem to be Solved by the Invention
[0015] The present invention was achieved in view of the
above-mentioned problems. A main object of the present invention is
to provide a safe and highly-reliable all-solid-state lithium
secondary battery using a sulfide-based solid electrolyte material
which can restrain generation of hydrogen sulfide gas, in case a
large amount of water is entered into a battery case by an accident
such as submersion associated with a breakage of the container.
Means for Solving the Problems
[0016] To attain the above-mentioned object, the present invention
provides an all-solid-state lithium secondary battery using a
sulfide-based solid electrolyte material, characterized in that the
battery has a metal salt M-X comprising a metal element "M" and an
anionic part "X" in a battery case thereof, and further
characterized in that a metal cation of the metal salt M-X
generated by disassociation caused with water can react with a
sulfide ion generated by a reaction between the sulfide-based solid
electrolyte material and the water.
[0017] According to the present invention, the metal cation of the
metal salt M-X generated by disassociation caused with water can
react with the sulfide ion generated by a reaction between the
sulfide-based solid electrolyte material and the water.
Accordingly, the present invention can provide a safe and
highly-reliable all-solid-state lithium secondary battery using a
sulfide-based solid electrolyte material which can restrain
generation of hydrogen sulfide gas, in case a large amount of water
is entered into a battery case by an accident such as submersion
associated with a breakage of the container.
[0018] In the above-mentioned invention, it is preferable that the
metal element "M" of the metal salt M-X is at least one selected
from the group consisting of Cd, Sn, Pb, Cu, Hg, Ag, Al, Mn, Zn, Fe
and Ni, and that the anionic part "X" of the metal salt M-X is at
least one selected from the group consisting of OH, SO.sub.4 and
NO.sub.3. This is because, such "M" and "X" as mentioned above
allow a reaction between: the metal cation generated by
dissociation of the metal salt M-X in water, and the sulfide ion
generated by a reaction between the sulfide-based solid electrolyte
material and the water, and the resultant can precipitate as a
stable solid substance less likely to be dissolved in water.
Further, by being precipitated as the solid substance mentioned
above, the resultant does not disperse in the atmosphere and
possible dangers such as a person inhaling the resultant can be
strongly restrained. Therefore, a safer and more highly-reliable
all-solid-state lithium secondary battery using a sulfide-based
solid electrolyte material can be obtained.
Effect of the Invention
[0019] The present invention attains an effect of providing a safe
and highly-reliable all-solid-state lithium secondary battery using
a sulfide-based solid electrolyte material which can restrain
generation of hydrogen sulfide gas, in case a large amount of water
is entered into a battery case by an accident such as submersion
associated with a breakage of the container.
BRIEF DESCRIPTION OF DRAWINGS
[0020] FIGS. 1A and 1B are a schematic sectional view showing one
example of the structure of an all-solid-state lithium secondary
battery of the present invention.
DESCRIPTION OF THE REFERENCE NUMBER
[0021] 1 All-solid-state lithium secondary battery [0022] 2 Solid
electrolyte layer [0023] 3 Cathode layer [0024] 4 Anode layer
[0025] 5 Spacer [0026] 6 Battery case [0027] 7 Resin packing [0028]
8 Metal salt [0029] 9 Current collector
BEST MODE FOR CARRYING OUT THE INVENTION
[0030] Hereinafter, an all-solid-state lithium secondary battery of
the present invention will be explained in detail.
[0031] The all-solid-state lithium secondary battery of the present
invention uses a sulfide-based solid electrolyte material and is
characterized in that the battery has a metal salt M-X comprising a
metal element "M" and an anionic part "X" in a battery case
thereof, and further characterized in that a metal cation of the
metal salt M-X generated by disassociation caused with water can
react with a sulfide ion generated by a reaction between the
sulfide-based solid electrolyte material and the water.
[0032] According to the present invention, the metal cation of the
metal salt M-X generated by disassociation caused with water can
react with the sulfide ion generated by a reaction between the
sulfide-based solid electrolyte material and the water. The
sulfide-based solid electrolyte material generates hydrogen sulfide
(H.sub.2S) gas when it is contacted to water. The hydrogen sulfide
(H.sub.2S) gas firstly dissolves into the water and dissociates to
H.sup.+ and S.sup.2- in the water. The amount that H.sup.+ and
S.sup.2- respectively dissolves into water has a saturated amount,
and when the dissolved amount reaches to the saturated amount,
hydrogen sulfide (H.sub.2S) gas is generated into the
atmosphere.
[0033] In the present invention, the metal salt M-X is presented in
a battery case. When a large amount of water is entered into the
battery case, the metal salt M-X reacts with the water and
dissociates therefrom to generate a metal cation. The metal cation
reacts with the sulfide ion (S.sup.2-). As a result, an M-S (metal
sulfide) is generated and become a precipitate to fix the sulfide
ion (S.sup.2-). Therefore, it is possible to restrain the sulfide
ion (S.sup.2-) in the water from reaching to the saturated amount
and to further restrain the generation of the hydrogen sulfide
(H.sub.2S) gas into the atmosphere. Accordingly, the present
invention can provide a safe and highly-reliable all-solid-state
lithium secondary battery using a sulfide-based solid electrolyte
material which can restrain generation of hydrogen sulfide gas, in
case a large amount of water is entered into a battery case by an
accident such as submersion associated with a breakage of the
container.
[0034] Hereinafter, the all-solid-state lithium secondary battery
of the present invention will be explained with a reference to the
drawings.
[0035] FIG. 1A is a view showing one embodiment of a technical
structure of a coin type all-solid-state lithium secondary battery
of the present invention. As shown in FIG. 1A, when the battery of
the present invention is a coin type, it has a technical structure
wherein an all-solid-state lithium secondary battery 1 comprises a
solid electrolyte layer 2 sandwiched between a cathode layer 3 and
an anode layer 4, a spacer 5 is further provided on the outside of
the anode layer, and those mentioned are covered by a battery case
6 as a whole and sealed by a resin packing 7. A metal salt 8 is
provided in a place inside the battery case 6 where no potential is
applied. FIG. 1B is a view showing one embodiment of a technical
structure of a laminate type all-solid-state lithium secondary
battery of the present invention. As shown in FIG. 1B, when the
battery of the present invention is a laminate type, it has a
technical structure wherein an all-solid-state lithium secondary
battery 1 comprises a solid electrolyte layer 2 sandwiched between
a cathode layer 3 and an anode layer 4, a current collector 9 is
further provided on the outside thereof, and those mentioned are
covered by a battery case 6 as a whole and sealed. Similar to the
coin type battery, a metal salt 8 is provided in a place inside the
battery case 6 where no potential is applied.
[0036] Hereinafter, the all-solid-state lithium secondary battery
will be explained by each structure.
1. Metal Salt
[0037] The metal salt used in the present invention comprises a
metal element "M" and an anionic part "X", wherein a metal cation
of the metal salt M-X generated by dissociation caused with water
can react with a sulfide ion generated by a reaction between water
and a sulfide-based solid electrolyte material to be explained
later. The sulfide-based solid electrolyte material is specifically
a sulfide-based solid electrolyte material Li-A-S comprising Li, A
(A is at least one selected from the group consisting of P, Ge, B,
Si and I), and S. Accordingly, generation of hydrogen sulfide gas
can be restrained, in case a large amount of water is entered into
the battery case by an accident such as submersion associated with
a breakage of the container. This is because of the following
reasons. Generally, when the sulfide-based solid electrolyte
material is in contact with water, a reaction shown in the below
formula (1) is caused and hydrogen sulfide (H.sub.2S) gas is
generated:
Li-A-S (sulfide-based solid electrolyte
material)+H.sub.2O.fwdarw.Li-A-O+H.sub.2S (1)
(in the formula, A is at least one selected from the group
consisting of P, Ge, B, Si and I).
[0038] In the above-mentioned formula (1), the hydrogen sulfide
(H.sub.2S) gas firstly dissolves into water and dissociates to
H.sup.+ and S.sup.2- in the water. The amount that H.sup.+ and
S.sup.2- respectively dissolves into water has a saturated amount,
and when the dissolved amount reaches to the saturated amount,
hydrogen sulfide (H.sub.2S) gas is generated into the
atmosphere.
[0039] In the present invention, the metal salt M-X is presented in
a battery case, and a metal cation is generated by disassociation
caused by a reaction between the metal salt M-X and water in case a
large amount of water is entered into the battery case. As the
metal cation reacts with the sulfide ion (S.sup.2-), an M-S (metal
sulfide) is generated, become a precipitate and fixes the sulfide
ion (S.sup.2-) as shown in the below formula (2):
Li-A-S (sulfide-based solid electrolyte
material)+M-X+H.sub.2O.fwdarw.Li-A-O+M-S (metal sulfide)+2H--X
(2)
(in the formula, A is at least one selected from the group
consisting of P, Ge, B, Si and I). Therefore, the sulfide ion
(S.sup.2-) in the water is restrained from reaching to its
saturated amount and further, generation of hydrogen sulfide
(H.sub.2S) gas into the atmosphere can be restrained.
[0040] In the present invention, the metal salt M-X is not
particularly restricted as long as the metal salt reacts with water
to generate a metal cation and the metal cation can react with the
sulfide ion (S.sup.2-). It is preferable that the generated
substance thereby obtained is a stable solid substance less soluble
in water and precipitates therein. By being precipitated as the
solid substance mentioned above, the resultant does not disperse in
the atmosphere and possible dangers such as a person inhaling the
resultant can be strongly restrained. Therefore, a safer and more
highly-reliable all-solid-state lithium secondary battery using a
sulfide-based solid electrolyte material can be obtained. Such
metal element "M" of the metal salt M-X is preferably at least one
selected from the group consisting of Cd, Sn, Pb, Cu, Hg, Ag, Al,
Mn, Zn, Fe and Ni. Among them, Cd, Sn, Pb, Cu, Hg and Ag are more
preferable and Ag, Cu and Sn are especially preferable because they
have fast generating rate in generating the precipitate and being
low in their environmental burden.
[0041] Further, as the anionic part "X" of the metal salt M-X, it
is preferable that the part is at least one selected from the group
consisting of OH.sup.-, SO.sub.4.sup.2- and NO.sub.3.sup.-. Among
them, SO.sub.4.sup.2- and NO.sub.3.sup.- is more preferable, and
NO.sub.3.sup.- is especially preferable since they have a high
dissociation degree.
[0042] When the metal element "M" is Al, the anionic part "X" is
preferably OH.sup.-.
[0043] The state of the metal salt used in the present invention is
not particularly limited as long as the metal salt has the
above-mentioned functions as a metal salt. It is preferable that
the metal state is in a state which reacts with water when the
water enters into the battery case. For example, a metal salt in
solid state can be cited. As the example of the solid state, a
powder state, a pellet state obtained by molding and solidifying
the powder or by other means, and a film state can be cited. Among
them, a film state is preferable because it dissolves well into the
entered water. As an example of a producing method of a metal salt
in such a film state, a method of dropping an aqueous solution of
metal salt to a predetermined position and drying it can be
cited.
[0044] A position to provide the metal salt is preferably a
position which does not contact to a part where potential of a
terminal and an electrode such as a cathode or an anode is applied.
This is to prevent the metal salt from changing caused with a
reaction such as reduction by the potential to the metal salt.
[0045] Further, a position close to a sulfide-based solid
electrolyte layer which has a risk of generating much hydrogen
sulfide gas when water is entered into the battery case, a position
close to the sealed part sealing the battery where the water is
likely to enter, and the like are preferable.
[0046] Still further, it is preferable to provide the metal salt
over parts as wide as possible within the battery case. This is to
respond to a damage caused to every part of the battery case.
Thereby, the metal salt can be dissociated no matter where of the
battery case the water is entered, the metal cation generated by
the dissociation can react with a sulfide ion to precipitate the
metal sulfide and the sulfide ion can be fixed. As a result,
generation of the hydrogen sulfide gas can be restricted more
safely.
[0047] The amount of the metal salt provided in the battery case is
not particularly restricted as long as the above-mentioned
functions as the metal salt can be retained. The amount varies
depending on factors such as the amount of the sulfide ion
(S.sup.2-) generated when the sulfide-based solid electrolyte
material reacts with water, or the state of the metal salt.
Generally, the metal salt is preferably provided in large excess to
the sulfur (S) contained in the sulfide-based solid electrolyte
layer. Specifically, when the anionic part "X" of the metal salt is
a divalent anion in mol ratio to 1 mol, for example, it is
preferable to be within the range of: sulfur (S): metal salt=1:1 to
100, more preferable to be within the range of: sulfur (S): metal
salt=1:1 to 10, and particularly preferable to be within the range
of: sulfur (S): metal salt=1:1 to 5. When the anionic part "X" of
the metal salt is a monovalent anion, the amount needs to be double
of the case when the anionic part "X" of the metal salt is
divalent.
[0048] When the mol ration between the sulfur (S) and the metal
salt remains the above-mentioned ranges, it is sufficient for the
metal cation generated by dissociation of the metal salt caused
with water to fix, as the metal sulfide, the sulfide ion (S.sup.2-)
generated when the sulfide-based solid electrolyte material reacts
with water and dissolves therein. Accordingly, sulfur (S) can be
fixed better and generation of the hydrogen sulfide gas can be
restrained more safely.
2. Sulfide-Based Solid Electrolyte Layer
[0049] A sulfide-based solid electrolyte layer used in the present
invention will be explained. The sulfide-based solid electrolyte
layer used in the present invention uses a sulfide-based solid
electrolyte material. Specifically, a sulfide-based solid
electrolyte material uniaxially-compressed and molded into a pellet
form can be cited as an example.
[0050] In the present invention, as the sulfide-based solid
electrolyte material used for the sulfide-based solid electrolyte
layer, a solid electrolyte material (Li-A-S) made of Li, A, and S
can be cited. The "A" of the sulfide-based solid electrolyte
material Li-A-S is at least one selected from the group consisting
of P, Ge, B, Si and I. As the specific examples of such
sulfide-based solid electrolyte material Li-A-S,
70Li.sub.2S-30P.sub.2S.sub.5, LiGe.sub.0.25P.sub.0.75S.sub.4,
80Li.sub.2S-20P.sub.2S.sub.5, and Li.sub.2S--SiS.sub.2 can be
cited. Among them, 70Li.sub.2S-30P.sub.2S.sub.5 is particularly
preferable because it has a high ion conductivity.
[0051] As a method to produce a sulfide-based solid electrolyte
material used in the present invention, it is not particularly
restricted as long as a desired sulfide-based solid electrolyte
material can be obtained. For example, a method of vitrifying a
material such as a material containing Li and S by a planetary ball
mill and heat treating the same can be cited.
3. Cathode Layer
[0052] A cathode layer used in the present invention will be
explained. The cathode layer used in the present invention is not
particularly limited as long as the layer has a function as a
cathode layer. Materials used for general all-solid-state lithium
secondary batteries can be applied as cathode materials used for
the cathode layer. For example, a material wherein a cathode active
material LiCoO.sub.2 and a solid electrolyte
LiGe.sub.0.25P.sub.0.75S.sub.4 are mixed and made to a cathode mix
can be cited. Further, a conductivity auxiliary agent such as an
acetylene black, a Ketjen Black and carbon fiber may be contained
in the cathode layer in order to improve conductivity.
[0053] A layer thickness of the cathode layer used in the present
invention is not particularly restricted. A cathode layer having a
thickness same to a thickness of a solid electrolyte film used for
a general all-solid-state lithium secondary battery may be
used.
4. Anode Layer
[0054] An anode layer used in the present invention will be
explained. The anode layer used in the present invention is not
particularly limited as long as the layer has a function as an
anode layer. Materials used for general all-solid-state lithium
secondary batteries can be applied as an anode layer material used
for the anode layer. For example, an indium foil can be cited.
Further, a conductivity auxiliary agent such as an acetylene black,
a Ketjen Black and carbon fiber may be contained in the anode layer
in order to improve conductivity.
[0055] A layer thickness of the anode layer used in the present
invention is not particularly restricted. An anode layer having a
thickness same to a thickness of a solid electrolyte film used for
a general all-solid-state lithium secondary battery may be
used.
5. Other Structure
[0056] In the all-solid-state lithium secondary battery of the
present invention, constituents other than the above-mentioned
metal salt, sulfide-based solid electrolyte layer, cathode layer,
anode layer, i.e., such as a spacer, a resin packing, a battery
case, and a current collector, are not particularly restricted and
those used in general all-solid-state lithium secondary batteries
can be used. Specifically, as a spacer, a material same as the
battery case is preferable and a spacer made of materials such as
stainless and aluminum can be cited as examples. As a resin
packing, a resin having a low water absorption rate is preferable
and an epoxy resin can be cited as an example. Further, as a
battery case, a metal made is generally used and a battery case
made of stainless can be cited as an example. Moreover, a current
collector has a function to transmit an electron caused by a
reaction. As the current collector, it is not particularly
restricted as long as it has conductivity. For example, a metal
foil of Al, Ni, Ti, or a carbon paper can be cited as an example.
Further, the current collector used in the present invention may be
the one combining the function of the battery case. Specifically, a
case of preparing a battery case made of a SUS (stainless steel)
and using a part thereof as a current collector can be cited as an
example.
[0057] In the present invention, as an adsorbent, a material such
as zeolite, silica gel and activated carbon may be provided inside
or outside of the battery case. Thereby, when hydrogen sulfide
(H.sub.2S) gas is generated by a small amount of water, small to
the extent that dissociation of the metal salt of the present
invention would not be caused, such as in a case when the battery
is placed under a highly-humid environment and moisture presented
in the atmosphere enters into the battery case, the generated
hydrogen sulfide (H.sub.2S) gas can be adsorbed. Therefore, a safer
and more highly-reliable all-solid-state lithium secondary battery
using a sulfide-based solid electrolyte material can be
obtained.
6. Method for Producing an All-Solid-State Lithium Secondary
Battery
[0058] A method for producing an all-solid-state lithium secondary
battery of the present invention is not particularly restricted as
long as the above-mentioned all-solid-state lithium secondary
battery can be obtained. For example, the following method of
producing a battery cell can be cited: the cathode material, the
sulfide-based solid electrolyte material, and the anode material
are placed in a molding holder and uniaxial compressed and molded
into a pellet form to obtain an all-solid-state lithium secondary
battery pellet in pellet state; and next, after an aqueous solution
of a metal salt is provided to the predetermined position in the
battery case, the all-solid-state lithium secondary battery pellet
is provided in the battery case.
7. Application
[0059] The application of the all-solid-state lithium secondary
battery obtained by the present invention is not particularly
limited. For example, the battery can be used as an all-solid-state
lithium secondary battery for an automobile.
8. Shape
[0060] As an example of the all-solid-state lithium secondary
battery obtained in the present invention, a coin type, a laminate
type, a cylindrical type, and a square type can be cited. Among
them, a coin type, a laminate type and a square type is
preferable.
[0061] The present invention is not limited to the embodiments
described above. The embodiments described above are mere
illustrative, and those having substantially the same constitution
and the same working effect as in the technical idea described in
the claims of the present invention are included in the technical
scope of the present invention.
EXAMPLES
[0062] Hereinafter, the present invention is explained in more
detail by reference to the Examples.
Example 1
Production of an All-Solid-State Lithium Secondary Battery
[0063] A cathode active material (LiCoO.sub.2) and a solid
electrolyte material (LiGe.sub.0.25P.sub.0.75S.sub.4) were mixed by
a mass ratio of 7:3 and a cathode mix was prepared. This cathode
mix of 15 mg and the solid electrolyte material of 200 mg, and an
indium foil of 60 mg (thickness 0.2 mm) as an anode were placed in
a molding holder and pressed by 5 t/cm.sup.2 to produce an
electrode pellet having a diameter of about 10 mm and a thickness
of about 1.5 mm.
[0064] Next, an aqueous solution of cupric nitrate was dropped onto
the end part of the inner side of an upper cover for a battery case
of coin case type (made of SUS) and dried to precipitate cupric
nitrate (metal salt) of about 0.5 g. Further, as the Example was
supposed to create a submersion of the battery case at the time of
case breakage, a hole of .phi. 1 mm was made to the upper cover of
the coin case.
[0065] The above-mentioned electrode pellet was placed inside of
the coin case and the coin case was sealed by a resin (PP
(polypropylene)) to produce a coin cell.
Example 2
Production of an All-Solid-State Lithium Secondary Battery
[0066] A cathode active material (LiCoO.sub.2) and a solid
electrolyte material (LiGe.sub.0.25P.sub.0.75S.sub.4) were mixed by
a mass ratio of 7:3 and a cathode mix was prepared. This cathode
mix of 15 mg and the solid electrolyte material of 200 mg, and an
indium foil of 60 mg (thickness 0.2 mm) as an anode were placed in
a molding holder and pressed by 5 t/cm.sup.2 to produce an
electrode pellet having a diameter of about 10 mm and a thickness
of about 1.5 mm.
[0067] Next, an aqueous solution of cupric nitrate was dropped onto
an upper cover for a battery case of laminate case type (made of
aluminum) provided with a current collector made of SUS and a part
of the inside of a lower cover thereof where no current collector
is provided, that is the part where no potential is applied, and
dried to precipitate cupric nitrate (metal salt) of about 0.5 g.
Further, as the Example was supposed to create a submersion of the
battery case at the time of case breakage, a hole of .phi. 1 mm was
made to the upper cover of the laminate case.
[0068] After the above-mentioned electrode pellet was placed inside
of the laminate case, the laminate case was sealed so as the
current collector was derived to outside of the battery case.
Thereby, a laminate cell was produced.
Example 3
[0069] A laminate cell was produced in the same manner as in the
Example 2 except that a solid electrolyte material was changed to
70Li.sub.2S-30P.sub.2S.sub.5 (obtained by following to the method
disclosed in JP-A No. 2005-228570, wherein Li.sub.2 and
P.sub.2S.sub.5 were vitrified by a planetary ball mill with a mole
ratio of Li.sub.2S:P.sub.2S.sub.5=70:30 and then by heat treated)
and an amount of cupric nitrate precipitated was made to 1.0 g.
Example 4
[0070] A laminate cell was produced in the same manner as in the
Example 3 except that the metal salt used in the Example 3 was
changed into lead nitrate and its amount precipitated was 1.5
g.
Comparative Example 1
[0071] A coin cell is produced in the same manner as in the Example
1 except that the metal salt used in the Example 1 was not
used.
Comparative Example 2
[0072] A laminate cell is produced in the same manner as in the
Example 3 except that the metal salt used in the Example 3 was not
used.
Evaluation
Hydrogen Sulfide Level Measurement
[0073] The respective all-solid-state lithium secondary battery
cells obtained in the Examples 1-4 and the Comparative Examples 1-2
were submersed into water of 30 ml in a 100 ml beaker placed inside
of sealed plastic bag. The respective hydrogen sulfide level in the
plastic bag after one minute from the submersion was subsequently
measured with a hydrogen sulfide gas sensor (GBL-HS.RTM.
manufactured by JIKCO Ltd.) set in the plastic bag. Measured
results of the hydrogen sulfide level are shown in Table 1.
TABLE-US-00001 TABLE 1 Hydrogen Sulfide Level Hydrogen Sulfide
Level ppm Example 1 0 Example 2 0 Example 3 0 Example 4 0
Comparative Example 1 7 Comparative Example 2 16
[0074] As shown in Table 1, the respective hydrogen sulfide levels
obtained in Examples 1-4 were 0 ppm. On the other hand, hydrogen
sulfide of 7 ppm and that of 16 ppm were detected in the
Comparative Examples 1 and 2, respectively. The reason of this is
assumed to be as follows. As no metal salt was presented in the
respective cases when submersed, sulfide ions generated by a
reaction between the sulfide-based solid electrolyte materials and
water were unable to fix themselves so that hydrogen sulfide gas
was generated in each cases.
[0075] In view of the above-mentioned results, it was ascertained
that, in the respective all-solid-state lithium secondary batteries
obtained in the Examples, by comprising the metal salt in the
battery case, the metal cation of the metal salt generated by
dissociation caused with water reacted with the sulfide ion
generated by a reaction between the sulfide-based solid electrolyte
material and the water, the precipitate is generated, and thereby
the sulfide ion is fixed as the metal sulfide. It was ascertained
thereby that the all-solid-state lithium secondary battery of the
present invention has an effect of restricting generation of
hydrogen sulfide gas.
* * * * *