JPH1097858A - Lithium battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a lithium battery having great charge/discharge cycle durability by a method wherein the matrix of an electrolyte is formed by specifying the composition of a copolymer, and the polymer electrolyte contains lithium salt and a solvent capable of dissolving the lithium salt. SOLUTION: A lithium battery having a positive electrode, a negative electrode and an electrolyte includes the matrix of the electrolyte formed from copolymer containing each polymerization unit expressed by the formula I and II, or copolymer containing each polymerization unit expressed by the formula I, II and III. Moreover, lithium salt and the polymer electrolyte capable of dissolving the lithium salt are included. In the formula I, X is a fluorine atom, a chlorine atom, a perfluoroalkyl group or a perfluoroalkoxyl group. In the formula II, R<1> is a hydrogen atom or a methyl group, and R<2> is a straight chain alkyl group, a branch alkyl group or a cycloalkyl group. In the formula III, R<3> is a hydrogen atom or a methyl group, and R<4> is a straight chain alkyl group, a branch alkyl group or a cycloalkyl group.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lithium battery using a polymer electrolyte, and more particularly to a lithium secondary battery having excellent cycle life.

[0002]

2. Description of the Related Art A battery using a material capable of occluding and releasing an alkali metal and an alkali metal ion as an electrode active material has been developed.
Attracting attention as having a high energy density,
Among them, lithium secondary batteries have been particularly widely used as power supplies for electronic devices because of their particularly high energy density.

In recent years, measures have been taken to prevent liquid leakage by using liquid electrolytes for primary and secondary batteries, to reduce ignitability of flammable electrolytes, to improve the ease of incorporation into electronic equipment by forming batteries into films, and to reduce space. Polymer electrolytes have been proposed from the standpoint of effective utilization of the polymer (Japanese Patent Application Laid-Open No. 8-50740).
7, Tokiohei 4-506726, etc.).

[0004] Polyethylene oxide-based polymer electrolytes are electrochemically stable, but have the drawback that the solvent retention of the organic electrolyte is low. The polyacrylate-based polymer electrolyte having a three-dimensional structure has good solvent retention, but is electrochemically unstable and is not suitable for a 4V class battery. The polymer electrolyte made of polyvinylidene fluoride is electrochemically stable and has a feature that the polymer is hardly burned because it contains fluorine atoms. However, when the temperature of the polymer electrolyte is increased, the electrolyte oozes out of the polymer. In contrast, vinylidene fluoride /
Attempts have been made to solve this problem by using hexafluoropropylene copolymers.

Further, the conventional lithium secondary battery using a polymer electrolyte has a drawback that the charge / discharge cycle durability is inferior to that of a battery using a liquid electrolyte.

[0006]

DISCLOSURE OF THE INVENTION The present invention provides a lithium battery having a good electrolyte retention and a high stability by examining a new composition of a polymer electrolyte. I do.

[0007]

According to the present invention, there is provided a lithium battery having a positive electrode, a negative electrode and an electrolyte, wherein the electrolyte comprises a copolymer containing each polymerized unit represented by the general formulas (a) and (b). A polymer electrolyte containing a lithium salt and a solvent capable of dissolving the lithium salt as a matrix with a copolymer containing the respective polymerized units represented by the general formulas (a), (b) and (c) as a matrix; To provide a lithium battery.

[0008]

Embedded image (—CF ₂ —CFX—) (a)

(Where X is a fluorine atom, a chlorine atom, a perfluoroalkyl group having 1 to 3 carbon atoms or a 1 to 3 carbon atom)
Is a perfluoroalkoxyl group. )

[0010]

Embedded image

(Where R ¹ is a hydrogen atom or a methyl group; R ² is a linear alkyl group, a branched alkyl group or a cycloalkyl group, having 1 to 12 carbon atoms and a hydrogen atom Part or all may be substituted by a fluorine atom. Q is 0 or 1.)

[0012]

Embedded image

(Where R ³ is a hydrogen atom or a methyl group; R ⁴ is a linear alkyl group, a branched alkyl group or a cycloalkyl group, which has 1 to 12 carbon atoms and a hydrogen atom A part or the whole may be substituted by a hydroxyl group, p is 0 or 1, and in the general formula (b), q
When = 0, p = 1. )

The matrix of the polymer electrolyte in the present invention may be a copolymer containing the polymerized units represented by the general formulas (a) and (b) as essential components or the general formulas (a), (b) and (c) Is a copolymer containing each polymerized unit represented by the following as an essential component, but the polymerized unit as an essential component and a polymer unit based on another monomer capable of forming a copolymer do not exceed 30 mol%. May be used as appropriate.

As other monomers, for example, propylene, isobutylene, acrylic acid and its alkyl ester, methacrylic acid and its alkyl ester, vinyl fluoride, hexafluoropropylene, chloroethyl vinyl ether and the like can be mentioned.

The molar ratio of the polymer units of the general formulas (a) and (b) or the polymer unit of the general formulas (a), (b) and (c) constituting the matrix of the polymer electrolyte of the battery of the present invention. The molar ratio, and also the molar ratio of other components added as necessary, the molecular weight of the copolymer, and the like, depend on the solubility or dispersion of the matrix in the organic solvent used for mixing with the electrolytic solution when forming the polymer electrolyte. Can be arbitrarily selected depending on the properties, miscibility of the matrix with the electrolyte and retention of the electrolyte, adhesion of the polymer electrolyte to the current collector metal, strength, moldability, handleability, availability of the matrix, and the like. .

In the present invention, the polymerization unit represented by the general formula (a) is a polymerization unit based on a perhalogenated olefin, and among them, a polymerization unit based on chlorotrifluoroethylene or tetrafluoroethylene is particularly preferably employed. You.

In the present invention, as the polymerized unit represented by the general formula (b), a polymerized unit based on a vinyl ether having a linear or branched alkyl group having 2 to 4 carbon atoms, a polymerized unit based on cyclohexyl vinyl ether or Polymerized units based on vinyl esters of carboxylic acids having 2 to 4 carbon atoms are preferred. Among the polymerization units based on vinyl carboxylate, a polymerization unit based on vinyl acetate and a polymerization unit based on vinyl propionate are particularly preferably employed.

In the present invention, among the polymer units represented by the general formula (c), particularly preferable polymer units are the following 1) to 3).
Of each polymerization unit. 1) An alkyl group having 2 to 4 carbon atoms different from the general formula (b) (however, it may be linear or branched)
Polymerized unit based on vinyl ether having 2) Polymerized units based on a vinyl ether having a cyclohexyl group. 3) A polymerized unit based on an alkyl allyl ether (where the alkyl group has 1 to 4 carbon atoms and may be linear or branched). Further, since the polymerization unit based on hydroxyalkyl vinyl ether has a cross-linking site, when used together with butylated melamine, epoxy-modified melamine, methylated urea, long-chain aliphatic dicarboxylic acid, and polyvalent isocyanates, they are cross-linked and cured. Therefore, it is a preferred polymerized unit.

In the case of the copolymer containing the polymer units represented by the general formulas (a) and (b), the matrix of the polymer electrolyte in the present invention is a polymer unit based on chlorotrifluoroethylene and a polymer unit based on an alkyl vinyl ether. It is preferably a copolymer containing a unit. Further, in the case of a copolymer containing each of the polymerization units represented by the general formulas (a), (b) and (c), the copolymer is based on a polymerization unit based on chlorotrifluoroethylene, a polymerization unit based on cyclohexyl vinyl ether, and an alkyl vinyl ether. It is preferably a copolymer containing a polymerized unit.

When the matrix used to hold the electrolytic solution used in the present invention is a copolymer containing each of the polymer units represented by the general formulas (a) and (b), the composition is represented by the general formula ( It is preferable that the copolymer contains 40 to 60 mol% and 40 to 60 mol% of each of the polymer units of a) and (b).

If the content of the polymerized unit represented by the general formula (a) is more than 60% by mole, the crystallinity of the polymer becomes high and the electrolyte does not easily penetrate into the polymer. It is not preferable because the degree becomes low. On the other hand, if it is less than 40 mol%, the strength of the polymer electrolyte is undesirably reduced. A more preferred content of the polymerized unit represented by the general formula (a) is 45 to 55 mol%.

When the content of the polymerized unit represented by the general formula (b) is less than 40 mol%, the solubility of the copolymer in an organic solvent decreases, and it becomes difficult to uniformly mix the copolymer with an electrolytic solution. It is not preferable because electric conductivity is lowered. On the other hand, if it exceeds 60 mol%, the polymer electrolyte strength is undesirably reduced. A more preferred content of the polymerized unit represented by the general formula (b) is 45 to 55 mol%.

When the matrix to be used for holding the electrolytic solution used in the present invention is a copolymer containing the polymerized units represented by the general formulas (a), (b) and (c), the composition is as follows: It is preferable to contain 40-60 mol%, 5-55 mol%, and 5-45 mol% of each polymerization unit represented by general formula (a), (b), and (c), respectively.

When the content of the polymerized unit represented by the general formula (a) is more than 60% by mole, the crystallinity of the polymer becomes high and the electrolyte does not easily penetrate into the polymer. It is not preferable because the degree becomes low. On the other hand, if it is less than 40 mol%, the strength of the polymer electrolyte is undesirably reduced. A more preferred content of the polymerized unit represented by the general formula (a) is 45 to 55 mol%.

When the content of the polymerized unit represented by the general formula (b) is less than 5 mol%, the solubility of the copolymer in an organic solvent is reduced, and it becomes difficult to uniformly mix the copolymer with an electrolytic solution. It is not preferable because electric conductivity is lowered. In addition, 55 mol%
If it is more than 10%, the polymer electrolyte strength is undesirably reduced. The more preferable content of the polymerization unit represented by the general formula (b) is 10 to 40 mol%.

When the content of the polymerized unit represented by the general formula (c) is less than 5 mol%, the polymer electrolyte becomes brittle,
It is not preferable because the flexibility of the polymer electrolyte is insufficient.
On the other hand, if it exceeds 45 mol%, the self-sustainability of the film is undesirably reduced. The more preferred content of the polymerized unit represented by the general formula (c) is 10 to 30 mol%.

The intrinsic viscosity reflecting the molecular weight of the copolymer which is the matrix of the polymer electrolyte used in the present invention is as follows:
When measured at 30 ° C. using tetrahydrofuran (hereinafter referred to as THF) as a solvent, it is preferably 0.01 to 2 dl / g. When it is more than 2 dl / g, it becomes difficult to uniformly mix the electrolyte and the electrolyte, and the amount of the electrolyte held is reduced.
It is not preferable because the electric conductivity of the polymer electrolyte decreases. If it is less than 0.01 dl / g, the strength of the polymer electrolyte is undesirably reduced. More preferably, 0.
03 to 1 dl / g.

The negative electrode active material in the present invention is a material capable of releasing lithium ions in the case of a primary battery, and a material capable of absorbing and releasing lithium ions in the case of a secondary battery. The material forming these negative electrode active materials is not particularly limited, for example, lithium metal, a lithium alloy, a carbon material, an oxide mainly containing a semimetal of Group 14, 15 of the periodic table,
Examples thereof include carbon compounds, silicon carbide compounds, silicon oxide compounds, titanium sulfide, and boron carbide compounds. As the carbon material, those obtained by thermally decomposing organic substances under various thermal decomposition conditions, artificial graphite, natural graphite, soil graphite, expanded graphite, flaky graphite, and the like can be used. As the oxide, a compound mainly composed of tin oxide can be used.

In the present invention, the positive electrode active material is a material capable of occluding lithium ions in the case of a primary battery, and a material capable of occluding and releasing lithium ions in the case of a secondary battery. For example, Ti, Zr, Hf of Group 4 of the periodic table, V, Nb, Ta of Group 5, Cr, Mo, W of Group 6, Mn of Group 7,
Group 8 Fe, Ru, Group 9 Co, Group 10 Ni, Group 11 Cu, Group 12 Zn, Cd, Group 13 Al, Ga, I
n, Group 14 Sn, Pb, Group 15 Sb, Bi and 16
Oxides and composite oxides containing a metal such as group Te as a main component, chalcogenides such as sulfides, oxyhalides,
A composite oxide of the metal and lithium can be used. Further, a conductive polymer material such as a polyaniline derivative, a polypyrrole derivative, a polythiophene derivative, a polyacene derivative, a polyparaphenylene derivative, or a copolymer thereof can also be used.

In the present invention, when a secondary battery using a material capable of occluding and releasing lithium as a negative electrode active material is used, lithium is contained in the negative electrode and / or the positive electrode. Generally, a lithium-containing compound is used at the time of synthesis of the positive electrode active material, and lithium is contained in the solid matrix of the positive electrode active material.
Further, lithium can be contained in the negative electrode by a chemical or electrochemical method before assembling the battery, or lithium can be incorporated by bringing lithium metal into contact with the negative electrode and / or the positive electrode when assembling the battery. As the lithium-containing compound used for the positive electrode active material, a composite oxide of lithium and manganese, a composite oxide of lithium and cobalt, and a composite oxide of lithium and nickel are particularly preferable.

As the solvent of the electrolytic solution in the present invention, a carbonate ester is preferable. Carbonate can be used either cyclic or chain. Examples of the cyclic carbonate include propylene carbonate and ethylene carbonate. Examples of the chain carbonate include dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, methyl propyl carbonate, methyl isopropyl carbonate and the like.

In the present invention, the above-mentioned carbonates can be used alone or in combination of two or more. It may be used by mixing with other solvents. Further, depending on the material of the negative electrode active material, the combined use of a chain carbonate and a cyclic carbonate may improve the discharge characteristics, cycle durability, and charge / discharge efficiency.

The solutes of the electrolytic solution used in the present invention include ClO ₄ ⁻ , CF ₃ SO ₃ ⁻ , BF ₄ ⁻ , PF ₆ ⁻ , AsF
^{_{6 -, SbF 6 -, CF}} 3 CO 2 -, (CF 3 SO 2) 2 N -
It is preferable to use any one or more of lithium salts having, for example, an anion.

In the electrolytic solution of the present invention, the solute is preferably dissolved in the solvent at a concentration of 0.2 to 2.0 mol / l. Outside this range, the ionic conductivity decreases and the electrical conductivity of the polymer electrolyte decreases. More preferably, it is 0.5 to 1.5 mol / l.

In the present invention, a polymer electrolyte in which the electrolyte is uniformly distributed in a matrix is used. The content of the electrolytic solution in the polymer electrolyte is preferably from 30 to 80% by weight. If the content is less than 30% by weight, the electric conductivity is undesirably low. On the other hand, if it exceeds 80% by weight, the polymer electrolyte cannot be maintained in a solid state, which is not preferable. Particularly preferably, 40 to 65% by weight is employed.

The polymer electrolyte of the present invention can be prepared by various methods. For example, the copolymer is dissolved or uniformly dispersed in an organic solvent. Next, an electrolytic solution in which a lithium salt is dissolved in a solvent is prepared. Mix the two solutions,
After coating, casting or spin coating on a glass plate with a bar coater or a doctor blade, it is heated and dried to remove mainly the organic solvent in which the copolymer is dissolved or dispersed, thereby obtaining a polymer electrolyte film. When the solvent used in the electrolyte partially evaporates during heating and drying, the film is newly impregnated with the solvent or the film is exposed to the solvent vapor to obtain a desired composition.

As the organic solvent for dissolving or dispersing the copolymer, THF, methyl ethyl ketone, benzene,
Toluene, xylene, N-methylpyrrolidone, acetone, acetonitrile and the like can be used. In order to selectively remove this organic solvent by heating and drying, a volatile organic solvent having a boiling point of 100 ° C. or lower such as THF and acetone is preferable.

The positive electrode and the negative electrode in the present invention are preferably obtained by kneading an active material with an organic solvent to form a slurry, applying the slurry to a metal foil current collector, and drying. More preferably, the positive electrode and the negative electrode are impregnated or coated with a liquid obtained by mixing an electrolytic solution and a solution or dispersion of the copolymer, so that the polymer electrolyte penetrates into the electrode layer. Also,
A liquid obtained by mixing an electrolyte and a solution or dispersion of the copolymer may be mixed with the slurry and then applied to the metal foil current collector.

In the present invention, the copolymer is formed into a porous film without being dissolved or dispersed in an organic solvent, and a slurry containing an active material is applied to a metal foil current collector and dried. Alternatively, the battery element can be formed by sandwiching between the positive electrode and the negative electrode, and then absorbing the organic electrolyte solution.

The shape of the lithium battery of the present invention is not particularly limited. A sheet shape (a so-called film shape), a folded shape, a wound-type cylindrical shape with a bottom, a button shape, and the like are selected according to the application.

The lithium battery according to the present invention has good charge / discharge cycle durability because the polymer electrolyte has good retention of the electrolyte and good electrical conductivity, and also has good adhesion between the polymer electrolyte and the electrode active material. improves. Therefore,
The lithium battery of the present invention can be applied to both primary batteries and secondary batteries depending on the selection of the positive electrode active material and the negative electrode active material.

[0043]

EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples.

Example 1 Using a stainless steel autoclave with an internal volume of 200 ml and equipped with a stirrer, t-butanol was used as a solvent, cyclohexyl vinyl ether, ethyl vinyl ether and azobisisobutyronitrile were charged, followed by solidification with liquid nitrogen and degassing. After removing the dissolved air,
Polymerization was performed by raising the temperature while introducing chlorotrifluoroethylene. Thereafter, the unreacted monomer was purged, and the autoclave was opened. The obtained polymer solution was poured into water to precipitate a polymer, which was then washed and dried to recover the polymer.

The obtained polymer was a chlorotrifluoroethylene / cyclohexyl vinyl ether / ethyl vinyl ether copolymer (52/25/23 in molar ratio). The intrinsic viscosity of this copolymer was 0.39 dl / g at 30 ° C. in THF.

In an argon atmosphere, 10 parts by weight of the polymer was dissolved in a mixed solvent of 8 parts by weight of xylene and 24 parts by weight of methyl ethyl ketone while heating with stirring. Next, LiPF ₆ was dissolved in a solvent in which ethylene carbonate and propylene carbonate were mixed at a volume ratio of 1: 1 at a concentration of 1 mol / l under an argon atmosphere to prepare an electrolytic solution. 5 parts by weight of this electrolytic solution was added to 21 parts by weight of the copolymer solution,
The mixture was heated to 60 ° C. and stirred. This solution was applied on a glass plate with a bar coater, and dried at 40 ° C. for 1 hour to remove methyl ethyl ketone and xylene, to obtain a 100 μm thick transparent polymer electrolyte film. The composition of this film was such that the copolymer, ethylene carbonate / propylene carbonate mixed solvent, and LiPF ₆ were 50/44.
3 / 5.7.

Next, the film was peeled off from the glass substrate, and the electric conductivity was adjusted to 25 ° C. by the AC impedance method.
The measurement was performed under an argon atmosphere. Electric conductivity is 4 × 10 ^-4
S / cm.

As a positive electrode active material, LiCoO ₂ powder
Parts by weight, 1.5 parts by weight of acetylene black as a conductive material, 6 parts by weight of the copolymer, 11 parts by weight of the electrolytic solution, and 70 parts by weight of methyl ethyl ketone were mixed under an argon atmosphere and heated with stirring. Thus, a slurry was obtained.
The slurry was applied to a 20 μm-thick aluminum foil having a roughened surface by a bar coater and dried to obtain a positive electrode.

Mesophase carbon fiber powder (average diameter 8 μm, average length 50 μm, (0
02) A spacing of 0.336 nm) 12 parts by weight of the copolymer, 6 parts by weight of the copolymer, 11 parts by weight of the electrolytic solution, and 70 parts by weight of methyl ethyl ketone were mixed in an argon atmosphere, and heated with stirring to obtain a slurry. Was. Thick this slurry 2
A copper foil having a surface roughened at 0 μm was applied with a bar coater and dried to obtain a negative electrode.

The polymer electrolyte film was 1.5 cm
The positive electrode and the negative electrode having an effective electrode of 1 cm × 1 cm are opposed to each other, and are sandwiched and fastened between two 1.5 cm-thick 3 cm square polytetrafluoroethylene back plates. By covering, the lithium ion secondary battery element was assembled under an argon atmosphere.

A charge / discharge cycle test was performed under the conditions of charge / discharge at a constant current of 0.5 C, a charge voltage up to 4.2 V, and a discharge voltage up to 2.5 V. As a result, the capacity retention after 500 cycles was 94%.

Example 2 Polymerization was carried out in the same manner as in Example 1 except that vinyl acetate and propyl vinyl ether were charged instead of cyclohexyl vinyl ether and ethyl vinyl ether.
Propyl vinyl ether copolymer (50/37 in molar ratio)
/ 13). The intrinsic viscosity of this copolymer in THF is
It was 0.25 dl / g at 30 ° C.

Except that this copolymer was used, the thickness was 100 μm in the same manner as in Example 1, and the copolymer, ethylene carbonate / propylene carbonate mixed solvent, and LiPF ₆ were in a weight ratio of 50 / 44.3 / 5.7. Was obtained. When the electric conductivity of this film was measured in the same manner as in Example 1, it was 4 × 10 ⁻⁴ S / cm.

A battery element was assembled in the same manner as in Example 1 except that this polymer electrolyte was used, and a charge / discharge cycle test was performed in the same manner as in Example 1. The capacity retention after 500 cycles was 88%.

[Example 3] Polymerization was carried out in the same manner as in Example 1 except that isobutyl vinyl ether and ethyl allyl ether were charged instead of cyclohexyl vinyl ether and ethyl vinyl ether.
An isobutyl vinyl ether / ethyl allyl ether copolymer (50/22/28 in molar ratio) was obtained. The intrinsic viscosity of this copolymer was 0.42 dl / g at 30 ° C. in THF.

Except that this copolymer was used, the thickness was 100 μm in the same manner as in Example 1, and the copolymer, a mixed solvent of ethylene carbonate / propylene carbonate and LiPF ₆ were in a weight ratio of 50 / 44.3 / 5.7. Was obtained. When the electric conductivity of this film was measured in the same manner as in Example 1, it was 3 × 10 ⁻⁴ S / cm.

A battery element was assembled in the same manner as in Example 1 except that this polymer electrolyte was used, and a charge / discharge cycle test was performed in the same manner as in Example 1. The capacity retention after 500 cycles was 90%.

Example 4 A lithium secondary battery element was assembled and subjected to a charge / discharge cycle test in the same manner as in Example 1, except that a lithium / aluminum alloy foil having a thickness of 100 μm was used as a negative electrode. The capacity retention rate after 500 cycles was 82%.

Example 5 Polymerization was carried out in the same manner as in Example 1 except that cyclohexyl vinyl ether was not charged.
A chlorotrifluoroethylene / ethyl vinyl ether copolymer (47/53 in molar ratio) was obtained. The intrinsic viscosity of this copolymer was 0.42 dl / g at 30 ° C. in THF.

Except that this copolymer was used, the thickness was 100 μm in the same manner as in Example 1, and the copolymer, ethylene carbonate / propylene carbonate mixed solvent, and LiPF ₆ were 58.8 / 36.5 / 4 by weight. A polymer electrolyte film having a composition of 0.7 was obtained. The electrical conductivity of this film was measured in Example 1.
^Was 1 × 10 ⁻⁴ S / cm.

A battery element was assembled in the same manner as in Example 1 except that this polymer electrolyte was used, and a charge / discharge cycle test was performed in the same manner as in Example 1. The capacity retention rate after 500 cycles was 82%.

[0062]

As is clear from the results of the examples, according to the present invention, a secondary battery using a polymer electrolyte having excellent cycle characteristics can be obtained.

Continued on the front page (51) Int.Cl. ⁶ Identification symbol FI H01M 10/40 H01M 10/40 AB (72) Inventor Katsuharu Ikeda 1150 Hazawacho, Kanagawa-ku, Kanagawa-ku, Yokohama-shi, Kanagawa Prefecture Asahi Glass Co., Ltd. Central Research Laboratory

Claims (7)

[Claims] 1. A lithium battery having a positive electrode, a negative electrode and an electrolyte, wherein the electrolyte comprises a copolymer containing each polymerized unit represented by the general formulas (a) and (b) or a general formula (a):
A lithium battery, comprising a polymer electrolyte containing a lithium salt and a solvent capable of dissolving the lithium salt, using a copolymer containing each of the polymerized units represented by (b) and (c) as a matrix. Embedded image (—CF ₂ —CFX—) (a) (where X is a fluorine atom, a chlorine atom, a perfluoroalkyl group having 1 to 3 carbon atoms, or a perfluoroalkoxyl group having 1 to 3 carbon atoms) (2) (However, R ¹ is a hydrogen atom or a methyl group. R ² is a linear alkyl group, a branched alkyl group, or a cycloalkyl group, and has 1 to 12 carbon atoms and a part of a hydrogen atom or All may be substituted with a fluorine atom.
Is 0 or 1. ) (However, R ³ is a hydrogen atom or a methyl group. R ⁴ is a linear alkyl group, a branched alkyl group, or a cycloalkyl group, and has 1 to 12 carbon atoms and a part of a hydrogen atom or All may be substituted with a hydroxyl group, p is 0
Or 1, when p = 0 in the general formula (b), p = 1. ) 2. A copolymer wherein the matrix of the polymer electrolyte contains 40 to 60 mol% of the polymerized unit represented by the general formula (a) and 40 to 60 mol% of the polymerized unit represented by the general formula (b). The lithium battery according to claim 1, wherein 3. A polymer electrolyte matrix comprising 40 to 60 mol% of a polymer unit represented by the general formula (a), 5 to 55 mol% of a polymer unit represented by the general formula (b), The lithium battery according to claim 1, which is a copolymer containing 5 to 45 mol% of the polymerized unit represented by c). 4. The polymerization unit represented by the general formula (a) is a polymerization unit based on chlorotrifluoroethylene or tetrafluoroethylene, and the polymerization unit represented by the general formula (b) is a vinyl ester or cyclohexyl vinyl ether. 4. The lithium battery according to claim 1, wherein the polymer unit is a polymer unit based on alkyl vinyl ether, diallyl ether or alkyl allyl ether. 5. The lithium battery according to claim 1, wherein the solvent contained in the polymer electrolyte is a carbonate ester. 6. The lithium battery according to claim 1, wherein the polymer electrolyte contains 30 to 80% by weight of a solution in which lithium is dissolved. 7. A polymer electrolyte comprising a matrix of 30
° C, intrinsic viscosity in tetrahydrofuran is 0.01
1, 2, 3, 4, or 4 dl / g of a copolymer.
7. The lithium battery according to 5 or 6.