JP2002298844A - Vanadium-based composite positive electrode for solid-state lithium polymer battery and lithium polymer battery using the same - Google Patents

Abstract

(57) Abstract: A composite positive electrode for a lithium polymer battery capable of providing a small and lightweight lithium polymer battery having a large charge / discharge capacity and a lithium polymer battery using the positive electrode. SOLUTION: A lithium salt as an electrolyte salt is added to a copolymer having a weight average molecular weight of 1,000,000 or more (which may contain allyl glycidyl ether) composed of ethylene oxide and a glycidyl ether having a side chain of ethylene oxide units having a polymerization degree of 1 to 12 (which may contain allyl glycidyl ether). A dissolved solid polymer electrolyte, a composite positive electrode comprising a vanadium-based oxide and conductive particles as a positive electrode active material or a weight average molecular weight of 500
A composite positive electrode to which 2000 or less polyethylene glycol is added is used. Negative electrode made of lithium metal or lithium metal alloy, ethylene oxide, degree of polymerization in side chain
A lithium polymer battery comprising a membrane obtained by crosslinking a solid polymer electrolyte obtained by dissolving a lithium salt in a copolymer having a weight average molecular weight of 1,000,000 or more and consisting of glycidyl ether having 1 to 12 ethylene oxide units and allyl glycidyl ether.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a composite positive electrode for a lithium polymer battery, a lithium polymer battery using the positive electrode, and a method for using the same.

[0002]

2. Description of the Related Art Recently, active research has been made on lithium secondary batteries, and many proposals have been made on battery constituent materials and assembly. For example, as a positive electrode active material
LiCoO ₂ , LiNiO ₂ , LiMn ₂ O ₄ , V ₂ O ₅ , V ₆ O ₁₃ , TiS ₂ etc. are used, and lithium, lithium-aluminum alloy, carbon (hard carbon, natural graphite, mesophase carbon micro Secondary batteries using beads, mesophase carbon fibers) and the like have been proposed.
In these lithium secondary batteries, as the electrolyte,
Propylene carbonate capable of moving lithium ions,
One or more aprotic organic solvents such as ethylene carbonate, diethyl carbonate, 1,2-dimethoxyethane, etc.
iClO ₄ , LiBF ₄ , LiAsF ₆ , LiPF ₆ , LiCF ₃ SO ₃ , LiN (CF ₃ SO ₂ )
An electrolyte in which a lithium salt such as ₂ is dissolved is used. However, since these electrolytes are flammable, lithium secondary batteries using these electrolytes have a risk of ignition or explosion. Further, when lithium metal or lithium alloy is used as the negative electrode, there is a risk that the lithium dendrites generated on the negative electrode reach the positive electrode and short-circuit. These problems result from using an organic solvent for the electrolyte.

[0003] In order to solve these problems, development of a lithium polymer battery in which an electrolytic solution is gelled with a polymer and fixed has been advanced, but there is still a problem of electrolyte leakage and a problem in a high temperature environment of 60 ° C or more. It is not something that can be used. Therefore, research on a solid-state lithium battery using a completely solid electrolyte polymer has been advanced. According to Natsu et al., A lithium polymer battery combining a positive electrode using polyethylene glycol with a molecular weight of about 2,000 as a binder and ionic conductor for the positive electrode, a polymer solid electrolyte, and lithium metal exhibits excellent battery characteristics at 60 ° C. Is J. Electorchem. So
c., 147, 2050 (2000). However, lithium polymer batteries using polyethylene glycol with a molecular weight of about 2,000 as the positive electrode have higher temperatures (80 ° C or higher).
In this case, the battery has a disadvantage that the cycle characteristics of the battery are greatly deteriorated. Further, at a high temperature of 60 ° C. or higher, since polyethylene glycol is a liquid, it has a weak binding force with the positive electrode active material and the conductive agent, and it is necessary to add a large amount to the positive electrode. 50 parts by weight or more is required for 100 parts by weight. For this reason, the ratio of the active material in the composite positive electrode decreases, and the energy density of the composite positive electrode decreases. Due to such drawbacks, a positive electrode for a lithium polymer battery that can withstand practical use has not yet been developed. Further, Japanese Patent Application No. 10-85890 discloses a patent on a positive electrode for a lithium polymer battery using V ₂ O ₅ as a positive electrode active material. In this patent, the battery using a positive electrode with V ₂ O ₅ as the active material has an upper limit voltage of 3.0 V during charging.
The discharge capacity of the battery at this time is small for a battery using V ₂ O ₅ .

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to provide a composite positive electrode for a lithium polymer battery capable of providing a lithium polymer battery which is small and lightweight and has a large charge / discharge capacity, and a lithium polymer battery using the positive electrode. .

[0005]

[Means for Solving the Problems] In order to obtain a small and lightweight lithium polymer battery having a large charge / discharge capacity, it is desirable to be able to charge at a high voltage.
Although the upper limit was 5 V, we found a composite positive electrode that can be charged to 4.2 V.

That is, the present invention relates to a copolymer comprising 30 to 95 mol% of ethylene oxide and 5 to 70 mol% of glycidyl ether having an ethylene oxide unit having a degree of polymerization of 1 to 12 in a side chain and having a weight average molecular weight of 1,000,000 or more. A composite consisting of a polymer solid electrolyte in which a lithium salt was dissolved as a salt, a vanadium-based oxide V _X O ₅ (X = 2 to 2.5) as positive electrode active material particles, and conductive particles was coated on a current collector. It is a composite positive electrode characterized by the above. Further, the present invention provides a composite positive electrode and a negative electrode composed of lithium metal or a lithium metal alloy, ethylene oxide of 30 to 94 mol%, and a side chain having a polymerization degree of 1 to 1
Glycidyl ether 5 having 2 ethylene oxide units
To provide a lithium polymer battery comprising a membrane obtained by cross-linking a polymer solid electrolyte obtained by dissolving a lithium salt in a copolymer having a weight average molecular weight of 1,000,000 or more consisting of 6969 mol% and allyl glycidyl ether 1-5 mol%, The charging method is provided.

The solid polymer electrolyte preferably used in the composite cathode of the present invention is a copolymer having a weight average molecular weight of 1,000,000 or more consisting of ethylene oxide and a glycidyl ether having an ethylene oxide unit having a degree of polymerization of 1 to 12 in a side chain. It is a polymer solid electrolyte to which a lithium salt is added as an electrolyte salt. Since this solid electrolyte has a higher molecular weight than polyethylene glycol having a molecular weight of about 2,000, it has excellent mechanical strength. Further, since the melting point is high, the adhesiveness to the positive electrode active material particles and the conductive particles is excellent even at a high temperature of 60 ° C. or higher. By using this polymer solid electrolyte having excellent binding properties for the composite positive electrode, the amount of the polymer solid electrolyte in the composite positive electrode can be reduced. Thereby, the energy density of the composite positive electrode can be improved. Further, since it is a solid even at a high temperature of 80 ° C. or higher, deterioration of the positive electrode is less likely to occur than a composite positive electrode prepared using polyethylene glycol having an average molecular weight of about 2,000. Therefore, the lithium polymer battery of the positive electrode using this polymer is not only at 60 ° C, but also at a higher temperature (80 ° C).
Above), high battery performance can be exhibited. In the present invention, the composite positive electrode is produced by applying a composite of a solid polymer electrolyte, positive electrode active material particles, and conductive particles onto a current collector. Aluminum, platinum,
Carbon foils, meshes, foams and other shapes can be used.

A polymer solid electrolyte in which a lithium salt is dissolved as an electrolyte salt in a copolymer obtained by copolymerizing ethylene oxide and a glycidyl ether having an ethylene oxide unit having a polymerization degree of 1 to 12 in a side chain and further allyl glycidyl ether is crosslinked. This can further increase the strength of the solid polymer electrolyte. For this reason, after the composite of the solid polymer electrolyte, the positive electrode active material particles, and the conductive particles is coated on the current collector, when the crosslinking is performed, the solid polymer electrolyte, the positive electrode active material particles, and the conductive particles are mixed. It is possible to further improve the binding property. As a crosslinking method at this time,
A radical initiator selected from organic peroxides, azo compounds and the like, and active energy rays such as ultraviolet rays and electron beams can be used. Polyethylene glycol having an average molecular weight of 500 or more and 2000 or less or an ether compound thereof can be added to the composite positive electrode. As the ether compound of polyethylene glycol, mono or dimethyl ether and mono or diethyl ether are preferable. By cross-linking the solid polymer electrolyte in the composite positive electrode, the binding property between the positive electrode active material particles and the conductive particles is enhanced. For this reason, even if polyethylene glycol or its ether compound having poor binding properties is added to the composite positive electrode, deterioration of the positive electrode due to repeated charge / discharge cycles can be reduced. In addition, polyethylene glycol having an average molecular weight of 500 or more and 2000 or less or its ether compound has excellent ionic conductivity at high temperatures (60 ° C. or more). It can be improved.

A vanadium-based oxide has been widely used as a 3V-class positive electrode material for a lithium polymer secondary battery. As the vanadium-based oxide is charged, the battery voltage monotonically increases. A lithium polymer battery uses a solid polymer electrolyte as an electrolyte, but has poor ionic conductivity as compared with an organic electrolyte, and has a large voltage polarization during charge and discharge. For this reason,
The chargeable capacity will decrease due to polarization during charging. In a conventional battery using polyethylene oxide as a polymer solid electrolyte, the limit of the charging voltage was 3.5 V due to decomposition of the polymer solid electrolyte. Also, in the above-mentioned patent (Japanese Patent Application No. 10-85890), the upper limit of the charging voltage is 3.
It was 0V. In the present invention, ethylene oxide (30 to 94
Mol%), and a weight average molecular weight of 10% by weight of glycidyl ether (5 to 69 mol%) and allyl glycidyl ether (1 to 5 mol%) having an ethylene oxide unit having a degree of polymerization of 1 to 12 in the side chain.
A lithium polymer battery using a polymer solid electrolyte membrane in which a polymer solid electrolyte obtained by dissolving a lithium salt as an electrolyte salt in more than 100,000 copolymers as a polymer solid electrolyte membrane has a higher voltage
(4.2 V), which allows the battery to have a higher capacity than conventional lithium polymer batteries. Further, when the battery is fully charged, the voltage rises sharply, so that the charge control can be easily performed by setting the charge end voltage.

As electrolyte salts, LiClO ₄ , LiBF ₄ , LiAs
Lithium salts such as F ₆ , LiPF ₆ , LiCF ₃ SO ₃ , and LiN (CF ₃ SO ₂ ) ₂ can be used. Among these, LiN (CF ₃ S) is used as the lithium salt used for the polymer solid electrolyte in the positive electrode.
O ₂ ) ₂ can be used more easily. This is for the following reasons. Lithium salts such as LiPF ₆ widely used in lithium secondary batteries are easily hydrolyzed by moisture to generate HF. The generated HF decomposes the solid polymer electrolyte. Alternatively, it reacts with lithium metal to generate lithium fluoride. On the other hand, LiN (CF ₃ SO ₂ ) ₂ hardly hydrolyzes with water and does not generate HF. Also, LiN (C added to 100 parts by weight of the copolymer)
If the amount of F ₃ SO ₂ ) ₂ is less than 5 parts by weight, the lithium ion concentration in the solid polymer electrolyte is too low to obtain sufficient lithium ion conductivity. Also, 50 to 100 parts by weight of the copolymer
If the amount is more than part by weight, the lithium salt cannot be completely dissolved in the copolymer and cannot be added. For this reason, as the lithium salt in the solid polymer electrolyte, LiN (CF ₃ SO ₂ ) ₂ is preferable, and its amount is preferably 5 to 50 parts by weight based on 100 parts by weight of the copolymer.

The positive electrode active material particles and the solid polymer electrolyte contained in the composite positive electrode have no electronic conductivity. Therefore, in order for the oxidation-reduction reaction to occur in the positive electrode active material particles in the composite positive electrode, it is essential to add conductive particles to the composite positive electrode. Ketjen black or acetylene black, which gives high electron conductivity to the composite positive electrode with a small addition amount, is suitable as the conductive particles. The conductive particles in the composite positive electrode are preferably 5 to 20 parts by weight based on 100 parts by weight of the positive electrode active material. This is because if the amount of the conductive particles is less than 5 parts by weight based on 100 parts by weight of the positive electrode active material particles, the composite positive electrode cannot be given sufficient electronic conductivity, and the positive electrode active material particles in the composite positive electrode Redox reaction does not occur sufficiently. As a result, the utilization rate of the positive electrode active material particles decreases, and the charge / discharge capacity decreases significantly from the theoretical value. On the other hand, when 20 parts by weight or more are added to 100 parts by weight of the positive electrode active material particles, the electronic conductivity of the composite positive electrode can be secured, but the ratio of the positive electrode active material in the composite positive electrode decreases. As a result, the capacity of the composite positive electrode decreases.

The composite positive electrode preferably contains 5-35 parts by weight of a solid polymer electrolyte per 100 parts by weight of positive electrode active material particles. When the amount of the polymer solid electrolyte is 5 parts by weight or less, the binding force to the positive electrode active material particles is weak, and a composite positive electrode cannot be produced. If the amount is 35 parts by weight or more, the binding force is sufficient, but the number of the positive electrode active material particles in the composite positive electrode decreases, and the capacity of the composite positive electrode decreases. The weight average molecular weight of the copolymer used in this example was calculated by gel permeation chromatography in terms of standard polystyrene. Gel permeation chromatography is measured by Shimadzu Corporation RID-6
A, Showdex KD column manufactured by Showa Denko KK
806, KD-806M, KD-803, and solvent DM
Performed at 60 ° C. using F.

[0013]

EXAMPLES The present invention will now be described specifically with reference to examples.
I do. Example 1 V_TwoO_Five1.0 g of powder and 0.15 g of Ketjen Black
Take and mix well in a mortar. On the other hand, ethylene oxide (8
8 mol%) and 2- (2-methoxyethoxy) ethyl glycidyl
(12 mol%) copolymer (weight average molecular weight: 1.5 million)
 0.15g, LiN (CF _ThreeSO_Two)_Two Dissolve 0.033g in acetonitrile
I let it. V_TwoO_FiveThe above solution in Ketjen black mixed powder
Was added and mixed well in a mortar to obtain a positive electrode slurry. this
After applying the slurry to a 20μm thick aluminum foil,
Was removed in an oven at 80 ° C. Roll press this
This produces a composite positive electrode with a total positive electrode thickness of 40 μm.
did. The obtained composite cathode and polymer solid electrolyte membrane
Tylene oxide (80.6 mol%) and 2- (2-methoxyethoxy)
Ethyl glycidyl ether (17.7 mol%) and allyl glycidyl
LiN (CF) was added to 100 parts by weight of a copolymer of zyl ether (1.7 mol%)._Three
SO_Two)_Two30 parts by weight dissolved and crosslinked polymer solid
Electrolyte formed into a film with a thickness of 50 μm.
A coin-shaped cell is fabricated by laminating μm Li metal foil.
Was. Constant current charging at 0.5C, upper limit voltage 4.1V in 60 ℃ constant temperature bath
A constant current discharge was performed at a voltage of 0.2 C and a lower limit voltage of 2.0 V. Charge and discharge
FIG. 1 shows the discharge capacity when this was repeated. This figure
Showed a high initial discharge capacity of about 300 mAh / g of positive electrode active material.
(Hereafter, mAh / g is the charge per 1 g of positive electrode active material.)
Discharge capacity). High discharge of 200mAh / g even after 80 cycles
Maintains capacity and prototype battery is high at 60 ° C
It was found that it exhibited cycle characteristics.

Example 2 1.0 g of V ₂ O ₅ powder and 0.15 g of Ketjen Black were collected and mixed well in a mortar. On the other hand, ethylene oxide (8
(8 mol%) and 2- (2-methoxyethoxy) ethyl glycidyl ether (12 mol%) copolymer (weight average molecular weight: 1.5 million)
0.20 g and 0.067 g of LiN (CF ₃ SO ₂ ) ₂ were dissolved in acetonitrile. The above solution was added to V ₂ O ₅ and Ketjen Black mixed powder and mixed well in a mortar to obtain a positive electrode slurry. After applying this slurry to a 20 μm thick aluminum foil, the solvent was removed.
Removed in an oven at 80 ° C. This was roll-pressed to produce a composite positive electrode having a total thickness of 40 μm for the positive electrode. The obtained composite positive electrode, 100 wt.% Of a copolymer of ethylene oxide (80.6 mol%) and 2- (2-methoxyethoxy) ethyl glycidyl ether (17.7 mol%) and allyl glycidyl ether (1.7 mol%) as a polymer solid electrolyte membrane LiN (CF ₃ SO
₂ ) 30 parts by weight of ₂ were dissolved and crosslinked, and a polymer solid electrolyte was formed into a film having a thickness of 50 μm.
The m-type Li metal foils were bonded together to produce a coin cell. 6
In a constant temperature bath at 0 ° C. and 80 ° C., constant current charging was performed at 0.2 C and an upper limit voltage of 4.1 V, and constant current discharging was performed at 0.2 C and a lower limit voltage of 2.0 V. When the battery test temperature was 80 ° C, the same high cycle characteristics as when the battery test temperature was 60 ° C were exhibited.

Comparative Example 1 1.0 g of V ₂ O ₅ powder and 0.13 g of Ketjen black were collected and mixed well in a mortar. On the other hand, 0.53 g of polyethylene glycol monomethyl ether having an average molecular weight of about 2000, Li
0.177 g of N (CF ₃ SO ₂ ) ₂ was dissolved in acetonitrile. V ₂ O
_{5. The} above solution was added to Ketjen Black mixed powder and mixed well in a mortar to obtain a positive electrode slurry. After this slurry was applied to an aluminum foil having a thickness of 20 μm, the solvent was removed in a dryer at 80 ° C. This was roll-pressed to produce a composite positive electrode having a total thickness of 40 μm for the positive electrode. The obtained composite positive electrode, 100 wt.% Of a copolymer of ethylene oxide (80.6 mol%) and 2- (2-methoxyethoxy) ethyl glycidyl ether (17.7 mol%) and allyl glycidyl ether (1.7 mol%) as a polymer solid electrolyte membrane 30 parts LiN (CF ₃ SO ₂ ) ₂
A coin-shaped cell was prepared by dissolving parts by weight of a polymer solid electrolyte having been subjected to a cross-linking treatment to a film thickness of 50 μm, and then bonding a 100 μm-thick Li metal foil as a negative electrode. Constant current charging at 0.2C and upper limit voltage 4.1V in a thermostat at 60 ℃ and 80 ℃
Constant current discharge was performed at 0.2 C and a lower limit voltage of 2.0 V. When the battery test temperature was 80 ° C, the deterioration of the cycle characteristics was greater than when the battery test temperature was 60 ° C.

[0016]

[Table 1]

Example 3 1.0 g of V ₂ O ₅ powder and 0.15 g of Ketjen black were collected and mixed well in a mortar. On the other hand, ethylene oxide (8
(8 mol%) and 2- (2-methoxyethoxy) ethyl glycidyl ether (12 mol%) copolymer (weight average molecular weight: 1.5 million)
0.15 g and LiN (CF ₃ SO ₂ ) ₂ 0.05 g were dissolved in acetonitrile. The above solution was added to V ₂ O ₅ and Ketjen Black mixed powder and mixed well in a mortar to obtain a positive electrode slurry. After applying this slurry to a 20 μm thick aluminum foil, the solvent was removed.
Removed in an oven at 80 ° C. This was roll-pressed to produce a composite positive electrode having a total thickness of 40 μm for the positive electrode. The obtained composite positive electrode, 100 wt.% Of a copolymer of ethylene oxide (80.6 mol%) and 2- (2-methoxyethoxy) ethyl glycidyl ether (17.7 mol%) and allyl glycidyl ether (1.7 mol%) as a polymer solid electrolyte membrane LiN (CF ₃ SO
₂ ) 30 parts by weight of ₂ were dissolved and crosslinked, and a polymer solid electrolyte was formed into a film having a thickness of 50 μm.
The m-type Li metal foils were bonded together to produce a coin cell. 6
0.2C in a constant temperature bath at 0 ℃, the upper limit voltage is 3.2, 3.5, 3.8, 4.
1, constant current charging by changing to 4.4V, 0.2C, lower limit voltage 2.0V
At a constant current. Even when the upper limit voltage was 3.6 V or more, charging could be performed without any problem. FIG. 2 shows the discharge capacity at each upper limit voltage. From this, it was possible to increase the discharge capacity of the battery by charging it to a high voltage. FIG. 3 shows the relationship between the charge / discharge capacity and the battery voltage at the 10th charge / discharge cycle. From this figure, it can be seen that the battery voltage sharply rises near a capacity of 270 mAh / g, which corresponds to full charge. It was found that charging can be easily controlled by setting the charging end voltage to 4.0 to 4.2V.

Example 4 1.0 g of V ₂ O ₅ powder and 0.15 g of Ketjen black were collected and mixed well in a mortar. On the other hand, ethylene oxide (8
(8 mol%) and 2- (2-methoxyethoxy) ethyl glycidyl ether (12 mol%) copolymer (weight average molecular weight: 1.5 million)
0.10 g and LiN (CF ₃ SO ₂ ) ₂ 0.033 g were dissolved in acetonitrile. The above solution was added to V ₂ O ₅ and Ketjen Black mixed powder and mixed well in a mortar to obtain a positive electrode slurry. After applying this slurry to a 20 μm thick aluminum foil, the solvent was removed.
Removed in an oven at 80 ° C. This was roll-pressed to produce a composite positive electrode having a total thickness of 40 μm for the positive electrode. The obtained composite positive electrode, 100 wt.% Of a copolymer of ethylene oxide (80.6 mol%) and 2- (2-methoxyethoxy) ethyl glycidyl ether (17.7 mol%) and allyl glycidyl ether (1.7 mol%) as a polymer solid electrolyte membrane LiN (CF ₃ SO
₂ ) 30 parts by weight of 2 and a crosslinked polymer solid electrolyte formed into a film having a thickness of 50 μm, and a negative electrode having a thickness of 100 μm
The m-type Li metal foils were bonded together to produce a coin cell. 6
Constant current charging at the upper limit voltage of 4.1 V in a constant temperature bath at 0 ° C, lower limit voltage
A constant current discharge was performed at 2.0V. 200 charge / discharge with 0.2C current
After repeated cycles, battery capacity is 76% of initial capacity
It became. When charging and discharging were performed at 0.5 C, the capacity when charging and discharging was performed at 0.2 C was about 68%.

Example 5 1.0 g of V ₂ O ₅ powder and 0.15 g of Ketjen black were collected and mixed well in a mortar. On the other hand, ethylene oxide (8
2 mol%) and 2- (2-methoxyethoxy) ethyl glycidyl ether (18 mol%) and allyl glycidyl ether (1.7 mol
%) Copolymer (weight average molecular weight: 1.5 million) 0.10 g, LiN (CF
0.033 g of ₃ SO ₂ ) _{2 and} 0.005 g of benzoyl peroxide were dissolved in acetonitrile. The above solution was added to V ₂ O ₅ and Ketjen Black mixed powder and mixed well in a mortar to obtain a positive electrode slurry. After this slurry was applied to an aluminum foil having a thickness of 20 μm, the solvent was removed in a dryer at 80 ° C. This was roll-pressed to produce a composite positive electrode having a total thickness of 40 μm for the positive electrode. This composite positive electrode was placed in argon gas for 100
The polymer in the composite positive electrode was crosslinked by performing a heat treatment at a temperature of 3 ° C. for 3 hours. As a polymer solid electrolyte membrane, ethylene oxide (80.6 mol%) and 2- (2-methoxyethoxy) ethyl glycidyl ether (17.7 mol%) and allyl glycidyl ether (1.7 mol%) 100 parts by weight of a copolymer of LiN (CF ₃ SO ₂ ) ₂
Was prepared by dissolving 30 parts by weight of a polymer solid electrolyte having been subjected to crosslinking treatment to a film thickness of 50 μm.
A coin-shaped cell was produced by bonding metal foils. 60 ℃
Constant-current charging with an upper limit voltage of 4.1 V in a constant temperature bath, lower limit voltage of 2.0 V
At a constant current. When charging and discharging were repeated 200 times at a current of 0.2 C, the capacity of the battery was 81% of the initial capacity. When charging and discharging were performed at 0.5C, the capacity when charging and discharging was performed at 0.2C was about 63%. This is because the polymer in the composite positive electrode is crosslinked to increase the binding life between the positive electrode active material particles and the conductive particles, thereby extending the cycle life of the battery. It is considered that the decrease in capacity at 0.5 C was large due to the decrease in ionic conductivity.

Example 6 1.0 g of V ₂ O ₅ powder and 0.15 g of Ketjen black were collected and mixed well in a mortar. On the other hand, ethylene oxide (8
2 mol%) and 2- (2-methoxyethoxy) ethyl glycidyl ether (18 mol%) and allyl glycidyl ether (1.7 mol
%) Copolymer (weight average molecular weight: 1.5 million) 0.10 g, polyethylene glycol dimethyl ether having a molecular weight of about 2000 0.0
5 g, LiN (CF ₃ SO ₂ ) ₂ 0.033 g and benzoyl peroxide 0.005 g were dissolved in acetonitrile. The above solution was added to V ₂ O ₅ and Ketjen Black mixed powder and mixed well in a mortar to obtain a positive electrode slurry. After this slurry was applied to an aluminum foil having a thickness of 20 μm, the solvent was removed in a dryer at 80 ° C. This is roll-pressed to obtain a total positive electrode thickness of 40μ.
m composite positive electrode was produced. The polymer in the composite positive electrode was crosslinked by subjecting the composite positive electrode to a heat treatment at 100 ° C. for 3 hours in an argon gas. Ethylene oxide (80.6 mol%) and 2- (2-methoxyethoxy) as polymer solid electrolyte membrane
100 parts by weight of a copolymer of ethyl glycidyl ether (17.7 mol%) and allyl glycidyl ether (1.7 mol%) was mixed with LiN (CF ₃
SO ₂ ) ₂ dissolved in 30 parts by weight of a crosslinked polymer solid electrolyte was formed into a film having a thickness of 50 μm, and a negative electrode having a thickness of 100 μm.
A coin-shaped cell was produced by bonding together a μm Li metal foil. Constant current charging was performed at an upper limit voltage of 4.1 V and constant current discharging was performed at a lower limit voltage of 2.0 V in a 60 ° C. constant temperature bath. Charge and discharge with 0.2C current
After 200 cycles, the battery capacity is 7
9%. When charging and discharging were performed at 0.5 C, the capacity when charging and discharging was performed at 0.2 C was about 72%. This is because, by cross-linking the polymer in the composite positive electrode, the binding life with the positive electrode active material particles and the conductive particles is increased, so that the cycle life of the battery is extended, and the polyethylene glycol dimethyl ether added in the composite positive electrode causes It is considered that the decrease in capacity at 0.5 C was reduced due to the improved ionic conductivity.

[0021]

[Table 2]

[0022]

According to the present invention, there can be obtained a composite positive electrode for providing a lithium polymer battery which is small and lightweight and has a large charge / discharge capacity, and a lithium polymer battery using the positive electrode.
The batteries of the present invention can be charged to high voltages, which can achieve high capacities. Since the battery of the present invention operates stably even at a high temperature, it can be used as an electric vehicle, a hybrid vehicle, a battery for road leveling, and the like in which the battery temperature easily rises.

[Brief description of the drawings]

FIG. 1 shows the relationship between the discharge capacity and cycle characteristics of an all-solid lithium polymer battery using a V ₂ O ₅ composite positive electrode.

FIG. 2 shows the relationship between the upper limit voltage and the discharge capacity during charging of a lithium polymer battery using a V ₂ O ₅ composite positive electrode.

FIG. 3 shows a relationship between charge / discharge capacity and battery voltage of a lithium polymer battery using a V ₂ O ₅ composite positive electrode.

 ────────────────────────────────────────────────── ─── Continuing from the front page (72) Inventor Tetsuo Sakai 1-38 Midorioka, Ikeda-shi, Osaka Prefecture F-term (reference) 5H029 AJ01 AJ05 AK02 AL06 AM16 DJ16 EJ12 HJ01 HJ02 HJ11 5H050 AA05 AA07 BA17 CA02 CB07 FA17 GA22 HA01 HA02 HA11

Claims (10)

[Claims] 1. A copolymer having 30 to 95 mol% of ethylene oxide and 5 to 70 mol% of a glycidyl ether having an ethylene oxide unit having a degree of polymerization of 1 to 12 in a side chain and having a weight average molecular weight of 1,000,000 or more. A composite consisting of a solid polymer electrolyte in which salts are dissolved, a vanadium-based oxide V _X O ₅ (X = 2 to 2.5) as positive electrode active material particles, and conductive particles is coated on a current collector. Composite positive electrode. 2. A copolymer comprising 30 to 95 mol% of ethylene oxide and 5 to 70 mol% of a glycidyl ether having an ethylene oxide unit having a degree of polymerization of 1 to 12 in a side chain and having a weight average molecular weight of 1,000,000 or more is lithium as an electrolyte salt. A solid polymer electrolyte in which salts are dissolved, polyethylene glycol having an average molecular weight of 500 or more and 2000 or less, or an ether compound thereof, and a vanadium-based oxide V _X O ₅ (X = 2 to 2.
5) and a composite positive electrode, wherein a composite comprising conductive particles is coated on a current collector. 3. A glycidyl ether having 30 to 94 mol% of ethylene oxide, an ethylene oxide unit having a polymerization degree of 1 to 12 in a side chain, and 5 to 69 mol% of allyl glycidyl ether.
Mol% of a copolymer having a weight average molecular weight of 1,000,000 or more and a lithium salt dissolved as an electrolyte salt in a copolymer, and a vanadium-based oxide V _X O ₅ (X = 2
To 2.5), and a composite comprising conductive particles coated on a current collector. 4. A glycidyl ether having 30 to 94 mol% of ethylene oxide and an ethylene oxide unit having a degree of polymerization of 1 to 12 in a side chain, and 5 to 69 mol% of allyl glycidyl ether.
As a solid polymer electrolyte in which a lithium salt is dissolved as an electrolyte salt in a copolymer having a weight-average molecular weight of 1,000,000 or more consisting of polyethylene glycol or an ether compound having a weight-average molecular weight of 500 to 2,000, or a positive electrode active material particle. vanadium oxide _{V X O 5 (X = 2~2.5} ), and a composite positive electrode, characterized in that the complex consisting of the conductive particles was coated on a current collector. 5. The composite positive electrode according to claim 3, wherein the solid polymer electrolyte in the composite positive electrode is cross-linked. 6. The lithium salt used for the polymer solid electrolyte is LiN (CF ₃ SO ₂ ) ₂ , and the lithium salt is used as a copolymer 100
6. The composite positive electrode according to claim 1, wherein the composite positive electrode is used in an amount of 5 to 50 parts by weight based on parts by weight. 7. The method according to claim 1, wherein the conductive particles are Ketjen black or acetylene black, and the conductive particles are used in an amount of 5 to 20 parts by weight based on 100 parts by weight of the positive electrode active material particles. Item 6. The composite positive electrode according to any one of items 5. 8. The composite positive electrode according to claim 1, wherein the polymer solid electrolyte is used in an amount of 5 to 35 parts by weight based on 100 parts by weight of the positive electrode active material particles. 9. The composite positive electrode according to claim 1, a negative electrode comprising lithium metal or a lithium metal alloy, and ethylene oxide units having 30 to 94 mol% of ethylene oxide and a degree of polymerization of 1 to 12 in a side chain. Glycidyl ether having 5 to 69 mol% and allyl glycidyl ether
A lithium polymer battery comprising a membrane in which a polymer solid electrolyte in which a lithium salt is dissolved in a copolymer having a weight average molecular weight of 1,000,000 or more and comprising 1 to 5 mol% is crosslinked. 10. The method for charging a lithium polymer battery according to claim 9, wherein the charging is completed in a range of 3.6 to 4.2V.