U.S. patent application number 10/262096 was filed with the patent office on 2003-02-20 for process for preparation of spinel-type lithium manganate.
This patent application is currently assigned to Mitsui Mining & Smelting Co., Ltd.. Invention is credited to Arimoto, Shinji, Kamada, Tsuneyoshi, Nakashima, Takuya, Numata, Koichi.
Application Number | 20030035997 10/262096 |
Document ID | / |
Family ID | 26442173 |
Filed Date | 2003-02-20 |
United States Patent
Application |
20030035997 |
Kind Code |
A1 |
Numata, Koichi ; et
al. |
February 20, 2003 |
Process for preparation of spinel-type lithium manganate
Abstract
The process for preparing spinel-type lithium manganate
according to the present invention is constituted by a process to
admix the electrolyzed manganese dioxide, which is obtained by
neutralizing manganese dioxide precipitated by means of
electrolysis with any of potassium hydroxide, potassium carbonate
and lithium hydroxide, and a lithium material and a process to
subject the resulting mixture to a sintering process.
Inventors: |
Numata, Koichi;
(Takehara-shi, JP) ; Kamada, Tsuneyoshi;
(Takehara-shi, JP) ; Nakashima, Takuya;
(Kadoma-shi, JP) ; Arimoto, Shinji; (Kadoma-shi,
JP) |
Correspondence
Address: |
Charles A. Muserlian
c/o Bierman, Muserlian and Lucas
600 Third Avenue
New York
NY
10016
US
|
Assignee: |
Mitsui Mining & Smelting Co.,
Ltd.
|
Family ID: |
26442173 |
Appl. No.: |
10/262096 |
Filed: |
September 30, 2002 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10262096 |
Sep 30, 2002 |
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09701670 |
Nov 29, 2000 |
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09701670 |
Nov 29, 2000 |
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PCT/JP00/02211 |
Apr 6, 2000 |
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Current U.S.
Class: |
429/224 ;
204/292; 205/539; 423/599; 429/231.1 |
Current CPC
Class: |
H01M 4/505 20130101;
H01M 10/0525 20130101; C01G 45/1242 20130101; C01G 45/1221
20130101; H01M 4/485 20130101; H01M 4/131 20130101; Y02E 60/10
20130101; C01P 2002/32 20130101; C01P 2006/40 20130101 |
Class at
Publication: |
429/224 ;
423/599; 205/539; 204/292; 429/231.1 |
International
Class: |
H01M 004/50; C01G
045/12; C25B 011/04; C25B 001/00 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 8, 1999 |
JP |
11-101272 |
Apr 8, 1999 |
JP |
11-101273 |
Claims
What is claimed is:
1. A process for preparing spinel-type lithium manganate
characterized in that the spinel-type lithium manganate is prepared
by admixing electrolyzed manganese dioxide, which is obtained by
neutralizing manganese dioxide precipitated by means of
electrolysis with any of potassium hydroxide, potassium carbonate
and lithium hydroxide, and a lithium material and consequently by
subjecting the mixture to a sintering process.
2. The process for preparing spinel-type lithium manganate
according to claim 1, wherein pH of the electrolyzed manganese
dioxide being neutralized with either potassium hydroxide or
potassium carbonate is 2 or more.
3. The process for preparing spinel-type lithium manganate
according to claim 1, wherein the electrolyzed manganese dioxide
being neutralized with lithium hydroxide contains lithium in an
amount of 0.02-0.5% by weight.
4. The process for preparing spinel-type lithium manganate
according to any of claims 1 to 3, wherein the manganese dioxide is
pulverized either before or after the neutralization with any of
potassium hydroxide, potassium carbonate and lithium hydroxide.
5. The process for preparing spinel-type lithium manganate
according to claim 4, wherein the average particle size of the
pulverized manganese dioxide is in a range of from 5 to 30 m.
6. The process for preparing spinel-type lithium manganate
according to any of claims 1 through 5, wherein the sintering
process is operated at a temperature higher than 750.degree. C.
7. An anode material for non-aqueous electrolyte containing
secondary battery characterized by being composed of the
spinel-type lithium manganate obtained according to the process
described in any of claims 1 through 6.
8. A non-aqueous electrolyte containing secondary battery
characterized by being constituted with an anode using the anode
material for non-aqueous electrolyte containing secondary battery
according to claim 7, a cathode capable of occluding or
de-occluding lithium alloy or lithium and non-aqueous electrolyte.
Description
FIELD OF INVENTION
[0001] The present invention is directed to a process for preparing
spinel-type lithium manganate, and more specifically to a process
for preparing spinel-type lithium manganese, from which eluting
amount of manganese after prepared it into an anode material for
non-aqueous electrolyte secondary battery is reduced, and which can
improve performance of the battery under high temperature, such as
preservation property and cycle property under high
temperature.
BACKGROUND ART
[0002] Based on recent rapid shift to miniaturized and cordless
electronic hardware, such as personal computers and telephones, a
need for using secondary batteries as a driving power source is
becoming very intensive. Among the secondary batteries, the biggest
interest is directed to non-aqueous electrolyte containing
secondary battery since it can be the smallest in size and can
generates high energy density. As the anode material for
non-aqueous electrolyte containing secondary battery which
facilitates such desires as described above, lithium cobaltate
(LiCoO.sub.2), lithium nickelate (LiNiO.sub.2), lithium manganate
(LiMn.sub.2O.sub.4), etc. can be used, for example. Each of these
complex oxides has a voltage more than 4 V to lithium, and
therefore, a battery having high energy density can be obtained by
using any of such complex oxides.
[0003] Among the complex oxides described above, LiCoO.sub.2 and
LiNiO.sub.2 have a theoretical capacity of more or less 280 mAh/g,
while LiMn.sub.2O.sub.4 has a smaller theoretical capacity of 148
mAh/g. However, LiMn.sub.2O.sub.4 can be suitably used for EV use
because the resource of the raw material, manganese dioxides, is
plenty and is cheaper in cost as well as no cause of thermal
instability at charging like LiNiO.sub.2.
[0004] However, lithium manganate (LiMn.sub.2O.sub.4) has a problem
of elution of Mn therefrom at a high temperature, which gives
inferior battery property, such as preservation and cycle property
under high temperature.
[0005] Therefore, it is an object of the present invention to
provide a process for preparing spinel-type lithium manganate,
which can reduce the eluting amount of manganese at charging when
it is used as an anode material for non-aqueous electrolyte
containing secondary battery and can improve the battery property
under high temperature, such as preservation and cycle properties
under high temperature, an anode material composed of the lithium
manganate and a non-aqueous electrolyte containing secondary
battery using the said anode material.
DISCLOSURE OF THE INVENTION
[0006] In solving the problem described above, the first invention
of the present invention directing to a process for preparing
spinel-type lithium manganate is characterized by admixing the
electrolyzed manganese dioxide, which is prepared by neutralizing
the manganese dioxide precipitated by means of electrolysis with
any of potassium hydroxide, potassium carbonate and lithium
hydroxide, and a lithium material and then subjecting the resulting
mixture to a sintering process.
[0007] The second invention of the present invention is directed to
the process specified in the first invention, wherein pH of the
electrolyzed manganese dioxide being neutralized with either
potassium hydroxide or potassium carbonate is 2 or more.
[0008] The third invention of the present invention is directed to
the process specified in the first invention, wherein the
electrolyzed manganese dioxide being neutralized with lithium
hydroxide contains lithium in an amount of 0.02-0.5% by weight.
[0009] The fourth invention of the present invention is directed to
the process specified in the first, second and third inventions
described above characterized in that the manganese dioxide is
pulverized either before or after the neutralization with any of
potassium hydroxide, potassium carbonate and lithium hydroxide.
[0010] The fifth invention of the present invention is directed the
fourth invention, wherein the average particle size of the
pulverized manganese dioxide is in a range of from 5 to 30
.mu.m.
[0011] The sixth invention of the present invention is directed to
the process specified in any of the first to the fifth inventions,
wherein the sintering process is operated at a temperature higher
than 750.degree. C.
[0012] The seventh invention of the present invention is directed
to an anode material to be used for non-aqueous electrolyte
containing secondary battery, wherein the anode material is
composed of the spinel-type lithium manganate obtained according to
the process specified in any of the first to the sixth
inventions.
[0013] The eighth invention of the present invention is directed to
a non-aqueous electrolyte containing secondary battery, wherein the
secondary battery is composed of an anode using the anode material
for non-aqueous electrolyte containing secondary battery specified
in the seventh invention, a cathode capable of occluding and
de-occluding either lithium alloy or lithium and non-aqueous
electrolyte.
BRIEF EXPLANATION ON DRAWINGS
[0014] FIG. 1 is longitudinal section of the coin-type non-aqueous
electrolyte containing secondary battery specified in the Examples
and Comparative examples described below.
BEST MODE FOR CARRYING OUT THE INVENTION
[0015] Now, the present invention is explained in detail with
referring the attached drawings.
[0016] The present invention is explained hereinbelow, however, it
should be noted that the scope of the present invention shall not
be limited to the following description.
[0017] The process for preparing spinel-type lithium manganate
according to the present invention is constituted by a process to
admix the electrolyzed manganese dioxide being neutralized
beforehand by treating manganese dioxide precipitated by means of
electrolysis with any of potassium salt, lithium salt, etc. and a
lithium material, and the following process to sinter the resulting
mixture.
[0018] In the present invention, electrolyzed manganese dioxide is
used as the manganese material for the spinel-type lithium
manganate.
[0019] In the present invention, the electrolyzed manganese dioxide
is obtained according to the following process. For example, for
the electrolysis, manganese sulfate solution prepared at a fixed
concentration is used as an electrolyte, a carbon plate is used for
a cathode, and a titanium plate is used for an anode, then
electrolysis is proceeded at a fixed current density while heating
to electrically precipitate manganese dioxide around the cathode.
Then the precipitated manganese dioxide is exfoliated from the
anode and is then crushed to particles with a desired particle
size, preferably to an average particle size of from 5 to 30
.mu.m.
[0020] In the non-aqueous electrolyte containing secondary battery,
since the anode material is formed as a film having a thickness of
more or less 100 .mu.m, cracking of the film may be caused if the
particle size of the electrolyzed manganese dioxide is too large,
and formation of an uniform film tends to be difficult. When
providing the electrolyzed manganese dioxide having an-average
particle size of from 5 to 30 .mu.m as the material to produce the
spinel-type lithium manganate, an anode material suitable to be
used for film formation can be obtained without subjecting the
manganese dioxide to an additional pulverization process.
Therefore, it is estimated that the uniform distribution of
potassium can be facilitated by neutralization of the micronized
electrolyzed-manganese dioxide with a potassium salt.
[0021] The electrolyzed manganese dioxide pulverized into a desire
particle size is then neutralized with either a potassium salt or a
lithium salt, washed and followed by drying.
[0022] As the potassium salt used for the neutralization, any
potassium salts can be used, but it is particularly preferable to
use either potassium hydroxide or potassium carbonate.
Additionally, there is no limitation in order for the pulverization
and the neutralization, so the pulverization process may be carried
out following to the-neutralization process.
[0023] The pH of the electrolyzed manganese dioxide being
neutralized with the potassium salt is 2 or more, and is more
preferably in a range of from 2 to 5.5, and further preferable in a
range of from 2 to 4. If the pH is too high, though eluting amount
of manganese under high temperature can be reduced, the initial
discharge capacity decreases, whereas, when the pH is lower than 2,
the eluting amount of manganese cannot be lowered.
[0024] For the neutralization with a lithium salt, any lithium
salts can be preferably used, however, it is particularly
preferable to neutralize with lithium hydroxide.
[0025] There is no limitation in the order for the pulverization
and the neutralization, thus pulverization may be done after
completing the neutralization.
[0026] The amount of lithium contained in the electrolyzed
manganese dioxide being neutralized with the lithium salt is
preferably in a range of from 0.02 to 0.5% by weight. Though
eluting amount of manganese at a high temperature may decrease, but
the initial discharge capacity may be reduced when the lithium
amount is more than 0.5% by weight, while the performance of the
electrolyzed manganese dioxide may be insufficient when the lithium
amount is less than 0.02% by weight.
[0027] In the process described above, the same sintering process
as described in the process where employing the neutralization with
a potassium salt as described above.
[0028] In the present invention, the spinel-type lithium manganate
is obtained by admixing the electrolyzed manganese dioxide, which
has been neutralized with either a potassium salt or a lithium salt
beforehand, and the lithium material and subsequently sintering the
resulting mixture. As the lithium material, lithium carbonate
(Li2CO.sub.3), lithium sulfate (LiNO.sub.3), lithium hydroxide
(LiOH) and the like can be used, for example. The Li/Mn molar ratio
for the electrolyzed manganese dioxide and the lithium material is
preferably in a range of from 0.50 to 0.60.
[0029] For acquiring larger reaction area, it is also preferable to
pulverize the electrolyzed manganese dioxide and the lithium
material either before or after admixing them. The weighed and
admixed materials can be used either directly or after making them
into granules. The granulation may be done by either wet or dry
method, and a process, such as extruding granulation, rotary
granulation, fluid granulation, mixing granulation, spray drying
granulation, pressure molding granulation, and flake granulation
using rollers or the like, can be employed.
[0030] The materials obtained as described above are put into a
furnace for sintering and are sintered at a temperature of from 600
to 1,000.degree. C. to obtain the spinel-type lithiun manganate.
For obtaining spinel-type lithium manganate in monolayer, it is
sufficient to apply temperature around 600.degree. C., however, it
is preferable for the sintering to apply temperature higher than
750.degree. C.; and more preferably higher than 850.degree. C.,
since the granule growth does not proceed when the temperature for
sintering is lower than such range. As the furnace for sintering
used in the process, rotary kiln, stationary furnace and the like
can be given as the example. Time for the sintering should be more
than 1 hour, and preferably 5 to 20 hours, in order to make the
reaction uniform.
[0031] As described above, the spinel-type lithium manganate
containing a certain amount of either potassium or lithium can be
obtained. The spinel-type lithium manganate containing potassium is
used as an anode material for the non-aqueous electrolyte
containing secondary battery.
[0032] For the non-aqueous electrolyte containing secondary battery
according to the present invention, a mixed material of the said
anode material, a conductive material, such as carbon black, and a
binding agent, such as teflon (Trade name for polytetrafluoro
ethylene), is provided as an anode, either a lithium alloy or a
material like carbon capable of occluding and de-occluding lithium
is used as a cathode, and a mixture of lithium hexafluorophosphate
(LiPF.sub.6) and a mixed solvent of ethylene carbonate and
dimethylcarbonate or the like, or the one prepared into an
electrolyte in gel, is used as the non-aqueous electrolyte,
however, there is no limitation to such materials exemplified
above.
[0033] Since the non-aqueous electrolyte containing secondary
battery according to the present invention can control the elution
of manganese at charging condition, it can improve battery
performance under high temperature, such as preservation property
under high temperature and cycle property under high
temperature.
EXAMPLES
[0034] Now, the present invention is definitely explained with
referring the examples described below, however, it should be noted
that the scope of the present invention shall not be limited to the
description in the following examples.
Examples for Employing Neutralization with Potassium Salt
Example 1
[0035] As an electrolyte for manganese, aqueous solution of
manganese sulfate containing sulfuric acid at a concentration of 50
g/L and manganese at a concentration of 40 g/L was prepared.
Heating was applied to the electrolyte so as to raise the
temperature thereof to 95.degree. C., and electrolysis was carried
out by using a carbon plate as a cathode and a titanium plate as an
anode at current density of 60 A/m.sup.2. Then, manganese dioxide
electrically precipitated onto the anode was exfoliated and was
crashed into chips with a size of less than 7 mm, and the chips
were further pulverized into particles with an average particle
size of 20 .mu.m.
[0036] The manganese dioxide in an amount of 20 kg was washed with
20 liters water, then the water was removed, and another 20 liters
water was added to the manganese dioxide. Then, potassium hydroxide
in an amount of 75 g was dissolved in the manganese dioxide
solution, then the solution was subjected to neutralization for 24
hours while stirring, and the solution was then washed with water,
filtrated and dried at 50.degree. C. for 12 hours. The pH and
potassium content of the obtained powder were measured according to
the method of JIS K-1467-1984, and the results are shown in Table 1
below.
[0037] The manganese dioxide with the average particle size of 20
.mu.m in an amount of 1 kg was added with lithium carbonate so as
to adjust Li/Mn molar ratio in the mixture at 0.54, and the mixture
was then mixed and subjected to sintering process in a box-type
furnace at 800.degree. C. for 20 hours to obtain the spinel-type
lithium manganate.
[0038] An anode complex material was prepared by admixing the
spinel-type lithium manganate in an amount of 80 parts by weight
obtained as described above, carbon black in an amount of 15 parts
by weight as a conductive agent and polytetrafluoro ethylene in an
amount of 5 parts by weight as a binding agent.
[0039] By using the anode complex material, a coin-type non-aqueous
electrolyte containing secondary battery shown in FIG. 1 was
prepared. As shown in FIG. 1, a current collector 3 made of
stainless steel is attached by means of spot welding onto the
interior wall of an anode case 1 made of stainless steel, which is
resistant to an organic electrolyte. An anode 5 composed of the
said anode complex material is sealed with pressure onto the upper
side of the current collector 3. On the upper side of the anode 5,
a separator 6 made of microporous polypropyrene resin being sopped
in the electrolyte is located. At the opening part of the anode
case 1, a closing cap 2, of which lower side a cathode 4 composed
of metal lithium is attached, is located in between the anode case
and a gasket 7 made of polypropyrene. The closing cap 2 is also
functioning as a cathode terminate and is made of stainless steel
as well as the anode case 1. The diameter of the battery is 20 mm,
and the height is 1.6 mm. As the electrolyte, a solution prepared
by equivalently mixing ethylene carbonate and 1,3-dimethoxy ethane
in volume was used as a solvent, and lithium hexafluorophosphate
was used as a solute and was added into the solvent at a rate of 1
mol/liter to obtain the electrolyte.
[0040] The battery obtained as describe above was subjected to
charging tests. The charging test was carried out under a
temperature of 20.degree. C. at a voltage ranging from 4.3 to 3.0
V, and the current density was fixed at 0.5 mA/cm.sup.2. Further,
the battery was charged at a voltage of 4.3 V and was stored for 3
days at 80.degree. C., and the preservation property of the battery
was checked based on capacity preserving rate, which is calculated
from the discharging capacity of the battery. The results of the
initial discharging capacity and the preservation capacity
maintaining rate are shown in Table 1 below.
Example 2
[0041] According to the same process described in the Example 1
except changing the adding amount of potassium hydroxide to 110 g
at the neutralization of the electrolyzed manganese dioxide,
synthesis for the spinel-type lithium manganate was carried out.
The pH and the potassium content after the neutralization is shown
in Table 1. Also, a coin-type non-aqueous electrolyte containing
secondary battery was prepared by using the spinel-type lithium
manganate as the anode material according to the process disclosed
in the Example 1. Then, the initial discharging capacity and the
preservation capacity maintaining rate under high temperature of
the secondary battery was measured, and the results are shown in
Table 1 presented below.
Example 3
[0042] According to the same process described in the Example 1
except changing the adding amount of potassium hydroxide to 140 g
at the neutralization of the electrolyzed manganese dioxide,
synthesis for the spinel-type lithium manganate was carried out.
The pH and the potassium content after the neutralization is shown
in Table 1. Also, a coin-type non-aqueous electrolyte containing
secondary battery was prepared by using the spinel-type lithium
manganate as the anode material according to the process disclosed
in the Example 1. Then, the initial discharging capacity and the
preservation capacity maintaining rate under high temperature of
the secondary battery was measured, and the results are shown in
Table 1 presented below.
Example 4
[0043] According to the same process described in the Example 1
except changing the adding amount of potassium hydroxide to 200 g
at the neutralization of the electrolyzed manganese dioxide,
synthesis for the spinel-type lithium manganate was carried out.
The pH and the potassium content after the neutralization is shown
in Table 1. Also, a coin-type non-aqueous electrolyte containing
secondary battery was prepared by using the spinel-type lithium
manganate as the anode material according to the process disclosed
in the Example 1. Then, the initial discharging capacity and the
preservation capacity maintaining rate under high temperature of
the secondary battery was measured, and the results are shown in
Table 1 presented below.
Example 5
[0044] According to the same process described in the Example 1
except changing the adding amount of potassium hydroxide to 280 g
at the neutralization of the electrolyzed manganese dioxide,
synthesis for the spinel-type lithium manganate was carried out.
The pH and the potassium content after the neutralization is shown
in Table 1. Also, a coin-type non-aqueous electrolyte containing
secondary battery was prepared by using the spinel-type lithium
manganate as the anode material according to the process disclosed
in the Example 1. Then, the initial discharging capacity and the
preservation capacity maintaining rate under high temperature of
the secondary battery was measured, and the results are shown in
Table 1 presented below.
Example 6
[0045] According to the same process described in the Example 2
except changing the temperature applied for the sintering to
900.degree. C., synthesis for the spinel-type lithium manganate was
carried out. The pH and the potassium content after the
neutralization is shown in Table 1. Also, a coin-type non-aqueous
electrolyte containing secondary battery was prepared by using the
spinel-type lithium manganate as the anode material according to
the process disclosed in the Example 1. Then, the initial
discharging capacity and the preservation capacity maintaining rate
under high temperature of the secondary battery was measured, and
the results are shown in Table 1 presented below.
Example 7
[0046] According to the same process described in the Example 2
except changing the temperature applied for the sintering to
700.degree. C., synthesis for the spinel-type lithium manganate was
carried out. The pH and the potassium content after the
neutralization is shown in Table 1. Also, a coin-type non-aqueous
electrolyte containing secondary battery was prepared by using the
spinel-type lithium manganate as the anode material according to
the process disclosed in the Example 1. Then, the initial
discharging capacity and the preservation capacity maintaining rate
under high temperature of the secondary battery was measured, and
the results are shown in Table 1 presented below.
Comparative Example 1
[0047] According to the same process described in the Example 1
except omitting the neutralization process for the electrolyzed
manganese dioxide, namely the adding amount of potassium hydroxide
is 0 g, synthesis for the spinel-type lithium manganate was carried
out. The pH and the potassium content after the neutralization is
shown in Table 1. Also, a coin-type non-aqueous electrolyte
containing secondary battery was prepared by using the spinel-type
lithium manganate as the anode material according to the process
disclosed in the Example 1. Then, the initial discharging capacity
and the preservation capacity maintaining rate under high
temperature of the secondary battery was measured, and the results
are shown in Table 1 presented below.
1 TABLE 1 Preservation Capacity Initial Maintaining K Discharging
Rate under High JIS (% by Capacity Temperature pH weight) (mAh/g)
(%) Example 1 2.5 0.17 121 72 Example 2 3.5 0.35 118 78 Example 3
4.5 0.60 115 81 Example 4 5.0 0.70 113 84 Example 5 6.0 1.00 108 86
Example 6 3.5 0.35 115 87 Example 7 3.5 0.35 118 71 Comparative 1.7
0 124 64 Example 1
Example 8
[0048] According to the same process described in the Example 1
except changing the average particle size of the electrolyzed
manganese dioxide at the pulverization to 5 .mu.m, synthesis of the
spinel-type lithium manganate was carried out. A coin-type
non-aqueous electrolyte containing secondary battery was prepared
by using the spinel-type lithium manganate as the anode material
according to the process disclosed in the Example 1. Then, the
performance of the secondary battery was checked based on two
current densities, 0.5 mA/cm.sup.2 and 1.0 mA/cm.sup.2. The
discharging capacity at the current density of 0.5 mA/cm2 is fixed
to 100, and the discharging capacity rate at the current density of
1.0 mA/cm.sup.2 is represented as current load rate. The obtained
current load rates are shown in Table 2 presented below.
Example 9
[0049] The same examination as done in the Example 8 was carried
out for the coin-type non-aqueous electrolyte containing secondary
battery prepared in the Example 1. The current load rate obtained
is shown in Table 2 below.
Example 10
[0050] According to the same process described in the Example 1
except changing the average particle size of the electrolyzed
manganese dioxide at the pulverization to 30 .mu.m, synthesis of
the spinel-type lithium manganate was carried out. A coin-type
non-aqueous electrolyte containing secondary battery was prepared
by using the spinel-type lithium manganate as the anode material
according to the process disclosed in the Example 1, and the same
examination as done in the Example 8 was carried out for the
obtained secondary battery. The current load rate obtained is shown
in Table 2 below.
Example 11
[0051] According to the same process described in the Example 1
except changing the average particle size of the electrolyzed
manganese dioxide at the pulverization to 35 .mu.m, synthesis of
the spinel-type lithium manganate was carried out. A coin-type
non-aqueous electrolyte containing secondary battery was prepared
by using the spinel-type lithium manganate as the anode material
according to the process disclosed in the Example 1, and the same
examination as done in the Example 8 was carried out for the
obtained secondary battery. The current load rate obtained is shown
in Table 2 below.
2 TABLE 2 Average Particle Current Load Rate Size (.mu.m) (%)
Example 8 5 93 Example 9 20 88 Example 10 30 85 Example 11 35
74
Example 12
[0052] As an electrolyte for manganese, aqueous solution of
manganese sulfate containing sulfuric acid at a concentration of 50
g/L and manganese at a concentration of 40 g/L was prepared.
Heating was applied to the electrolyte so as to raise the
temperature thereof to 95.degree. C., and electrolysis was carried
out by using a carbon plate as a cathode and a titanium plate as an
anode at current density of 60 A/m.sup.2. Then, manganese dioxide
electrically precipitated onto the anode was exfoliated and was
crashed into chips with a size of less than 7 mm, and the chips
were further pulverized into particles with an average particle
size of 20 .mu.m.
[0053] The manganese dioxide in an amount of 20 kg was washed with
20 liters water, then the water was removed, and another 20 liters
water was added to the manganese dioxide. Then, lithium hydroxide
in an amount of 35 g was dissolved in the manganese dioxide
solution, then the solution was subjected to neutralization for 24
hours while stirring, then the solution was washed with water,
filtrated and dried at 50.degree. C. for 12 hours. The lithium
content in the obtained powder was measured and the results are
shown in Table 3 below.
[0054] The manganese dioxide with the average particle size of 20
.mu.m in an amount of 1 kg was added with lithium carbonate so as
to adjust Li/Mn molar ratio in the mixture at 0.54, and the mixture
was then mixed and subjected to sintering process in a box-type
furnace at 800.degree. C. for 20 hours to obtain the spinel-type
lithium manganate.
[0055] An anode complex material was prepared by admixing the
spinel-type lithium manganate in an amount of 80 parts by weight
obtained as described above, carbon black in an amount of 15 parts
by weight as a conductive agent and polytetrafluoro ethylene in an
amount of 5 parts by weight as a binding agent.
[0056] By using the anode complex material, a coin-type non-aqueous
electrolyte containing secondary battery shown in FIG. 1 was
prepared. As shown in FIG. 1, a current collector 3 made of
stainless steel is attached by means of spot welding onto the
interior wall of an anode case 1 made of stainless steel, which is
resistant to an organic electrolyte. An anode 5 composed of the
said anode complex material is sealed with pressure onto the upper
side of the current collector 3. On the upper side of the anode 5,
a separator 6 made of microporous polypropyrene resin being sopped
in the electrolyte is located. At the opening part of the anode
case 1, a closing cap 2, of which lower side a cathode 4 composed
of metal lithium is attached, is located in between the anode case
and a gasket 7 made of polypropyrene. The closing cap 2 is also
functioning as a cathode terminate and is made of stainless steel
as well as the anode case 1. The diameter of the battery is 20 mm,
and the height is 1.6 mm. As the electrolyte, a solution prepared
by equivalently mixing ethylene carbonate and 1,3-dimethoxy ethane
in volume was used as a solvent, and lithium hexafluorophosphate
was used as a solute and was added into the solvent at a rate of 1
mol/liter to obtain the electrolyte.
[0057] The battery obtained as describe above was subjected to
charging tests. The charging test was carried out under a
temperature of 20.degree. C. at a voltage ranging from 4.3 to 3.0
V, and the current density was fixed at 0.5 mA/cm.sup.2. Further,
the battery was charged at a voltage of 4.3 V and was stored for 3
days at 80.degree. C., and the preservation property of the battery
was checked based on capacity preserving rate, which is calculated
from the discharging capacity of the battery. The results of the
initial discharging capacity and the preservation capacity
maintaining rate are shown in Table 3 below.
Example 13
[0058] According to the same process described in the Example 1
except changing the adding amount of lithium hydroxide to 55 g at
the neutralization of the electrolyzed manganese dioxide, synthesis
for the spinel-type lithium manganate was carried out. The lithium
content in the spinel-type lithium manganate is shown in Table 3.
Also, a coin-type non-aqueous electrolyte containing secondary
battery was prepared by using the spinel-type lithium manganate as
the anode material according to the process disclosed in the
Example 1. Then, the initial discharging capacity and the
preservation capacity maintaining rate under high temperature of
the secondary battery was measured, and the results are shown in
Table 3 presented below.
Example 14
[0059] According to the same process described in the Example 1
except changing the adding amount of lithium hydroxide to 85 g at
the neutralization of the electrolyzed manganese dioxide, synthesis
for the spinel-type lithium manganate was carried out. The lithium
content in the spinel-type lithium manganate is shown in Table 3.
Also, a coin-type non-aqueous electrolyte containing secondary
battery was prepared by using the spinel-type lithium manganate as
the anode material according to the process disclosed in the
Example 1. Then, the initial discharging capacity and the
preservation capacity maintaining rate under high temperature of
the secondary battery was measured, and the results are shown in
Table 3 presented below.
Example 15
[0060] According to the same process described in the Example 1
except changing the adding amount of lithium hydroxide to 130 g at
the neutralization of the electrolyzed manganese dioxide, synthesis
for the spinel-type lithium manganate was carried out. The lithium
content in the spinel-type lithium manganate is shown in Table 3.
Also, a coin-type non-aqueous electrolyte containing secondary
battery was prepared by using the spinel-type lithium manganate as
the anode material according to the process disclosed in the
Example 1. Then, the initial discharging capacity and the
preservation capacity maintaining rate under high temperature of
the secondary battery was measured, and the results are shown in
Table 3 presented below.
Example 16
[0061] According to the same process described in the Example 1
except changing the adding amount of lithium hydroxide to 180 g at
the neutralization of the electrolyzed manganese dioxide, synthesis
for the spinel-type lithium manganate was carried out. The lithium
content in the spinel-type lithium manganate is shown in Table 3.
Also, a coin-type non-aqueous electrolyte containing secondary
battery was prepared by using the spinel-type lithium manganate as
the anode material according to the process disclosed in the
Example 1. Then, the initial discharging capacity and the
preservation capacity maintaining rate under high temperature of
the secondary battery was measured, and the results are shown in
Table 3 presented below.
Example 17
[0062] According to the same process described in the Example 2
except changing the temperature applied for the sintering to
900.degree. C., the synthesis for the spinel-type lithium manganate
was carried out. The lithium content in the spinel-type lithium
manganate is shown in Table 3. Also, a coin-type non-aqueous
electrolyte containing secondary battery was prepared by using the
spinel-type lithium manganate as the anode material according to
the process disclosed in the Example 1. Then, the initial
discharging capacity and the preservation capacity maintaining rate
under high temperature of the secondary battery was measured, and
the results are shown in Table 3 presented below.
Example 18
[0063] According to the same process described in the Example 2
except changing the temperature applied for the sintering to
700.degree. C., the synthesis for the spinel-type lithium manganate
was carried out. The lithium content in the spinel-type lithium
manganate is shown in Table 3. Also, a coin-type non-aqueous
electrolyte containing secondary battery was prepared by using the
spinel-type lithium manganate as the anode material according to
the process disclosed in the Example 1. Then, the initial
discharging capacity and the preservation capacity maintaining rate
under high temperature of the secondary battery was measured, and
the results are shown in Table 3 presented below.
3 TABLE 3 Initial Preservation Li Discharging Capacity (% by
Capacity Maintaining Rate weight) (mAh/g) Under High Temp. (%)
Example 12 0.02 123 69 Example 13 0.09 121 75 Example 14 0.13 118
78 Example 15 0.17 115 81 Example 16 0.23 110 84 Example 17 0.09
116 85 Example 18 0.09 121 68
Example 19
[0064] According to the same process described in the Example 1
except changing the average particle size of the electrolyzed
manganese dioxide at the pulverization to 5 .mu.m, synthesis of the
spinel-type lithium manganate was carried out. A coin-type
non-aqueous electrolyte containing secondary battery was prepared
by using the spinel-type lithium manganate as the anode material
according to the process disclosed in the Example 1. Then, the
performance of the secondary battery was checked based on two
current densities, 0.5 mA/cm.sup.2 and 1.0 mA/cm.sup.2. The
discharging capacity at the current density of 0.5 mA/cm.sup.2 is
fixed to 100, and the discharging capacity rate at the current
density of 1.0 mA/cm.sup.2 is represented as current load rate. The
current load rates obtained are shown in Table 4 presented
below.
Example 20
[0065] The same examination as done in the Example 8 was carried
out for the coin-type non-aqueous electrolyte containing secondary
battery prepared in the Example 1. The current load rate obtained
is shown in Table 2 below.
Example 21
[0066] According to the same process described in the Example 1
except changing the average particle size of the electrolyzed
manganese dioxide at the pulverization to 30 .mu.m, synthesis of
the spinel-type lithium manganate was carried out. A coin-type
non-aqueous electrolyte containing secondary battery was prepared
by using the spinel-type lithium manganate as the anode material
according to the process disclosed in the Example 1, and the same
examination as done in the Example 8 was carried out for the
obtained secondary battery. The current load rate obtained is shown
in Table 4 below.
Example 22
[0067] According to the same process described in the Example 1
except changing the average particle size of the electrolyzed
manganese dioxide at the pulverization to 35 .mu.m, synthesis of
the spinel-type lithium manganate was carried out. A coin-type
non-aqueous electrolyte containing secondary battery was prepared
by using the spinel-type lithium manganate as the anode material
according to the process disclosed in the Example 1, and the same
examination as done in the Example 8 was carried out for the
obtained secondary battery. The current load rate obtained is shown
in Table 4 below.
4 TABLE 4 Average Particle Current Load Rate Size (.mu.m) (%)
Example 19 5 94 Example 20 20 89 Example 21 30 86 Example 22 35
76
INDUSTRIAL USE
[0068] As described above, by using the spinel-type lithium
manganate obtained according to the process specified in the
present invention as the anode material for the non-aqueous
electrolyte containing secondary battery, control of manganese
elution from the battery at charging, improvement of high
temperature battery property, such as preservation property under
high temperature and cycle property under high temperature, and
improvement of the current load rate of the secondary battery can
be achieved.
* * * * *