JPH1153937A - Polymer electrolyte and lithium battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrochemically and thermally stable polymer electrolyte, having high ion conductivity by containing a solution having a copolymer containing polymerization unit based on fluoroolefin and a polymerization unit, based on an alkylvinyl ether or alkylaryl ether having carbonate bond as a matrix and an electrolyte dissolved in a nonaqueous solvent. SOLUTION: A solution of an electrolyte dissolved in a nonaqueous solvent is included in a matrix to form a polymer electrolyte and to impart conductivity. In this case, an alkylvinyl ether or alkylaryl ether having a polymerization unit, based on fluoroolefin and a carbonate bond [-OC (=O)-], is used. In the formula, hydrogen atom of the vinyl group or aryl group may be substituted by fluorine or chlorine atom. The carbonate bond is present between C-C bond of the alkyl group. The alkyl group may be straight, branched, or cyclic, and etheric oxygen atom may be present between C-C bond of the alkyl group.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a polymer electrolyte for an electrochemical device such as a battery, an electrochromic device and a capacitor.

[0002]

2. Description of the Related Art Conventionally, a liquid electrolyte obtained by dissolving an electrolyte in an organic solvent has been used as an electrolyte for various electrochemical devices such as primary batteries, secondary batteries, electrochromic devices, aluminum electrolytic capacitors, and electric double layer capacitors. Have been. However, when using a liquid electrolyte,
There are issues such as low reliability due to leakage of electrolyte to the outside of the device, scattering of electrolyte at the time of sealing the case of the device, and necessity of advanced sealing technology. In order to further enhance the property, a gel polymer electrolyte having a high ionic conductivity has been developed.

[0003] In particular, for primary batteries and secondary batteries, measures are taken against leakage caused by using a liquid electrolyte, measures to reduce the ignitability of flammable electrolytes, and integration into electronic equipment by forming batteries into films. Various types of polymer electrolytes have been proposed from the viewpoints of improvement in performance and effective use of space (Japanese Patent Application Laid-Open Nos. 8-507407 and 4-506).
726).

Among them, polyethylene oxide-based polymer electrolytes are electrochemically stable, but have a drawback in that the solvent retention of the organic electrolyte is low. A polyacrylate-based polymer electrolyte having a three-dimensional structure has good solvent retention, but is electrochemically unstable and is not suitable for a battery with high electromotive force.

[0005] A polymer electrolyte made of polyvinylidene fluoride is electrochemically stable and has a characteristic that the polymer has high heat resistance because it contains fluorine atoms. However, when the temperature of the polymer electrolyte is raised, the electrolyte oozes out of the polymer. On the other hand, there is an attempt to solve this problem by using a vinylidene fluoride / hexafluoropropylene copolymer.

When a conventional polymer electrolyte is applied to a lithium secondary battery characterized by high energy density, the charge / discharge cycle durability is inferior to that of a lithium secondary battery using a liquid electrolyte. There were drawbacks.

[0007]

DISCLOSURE OF THE INVENTION The present invention has high ion conductivity, is electrochemically and thermally stable, and can be used for batteries, electrochromic devices, aluminum electrolytic capacitors, electric double layer capacitors and the like. Provided is a polymer electrolyte having a gel strength capable of coping with the reduction in thickness, size, and weight of various electrochemical elements.

[0008]

DISCLOSURE OF THE INVENTION The present invention relates to a polymerization unit based on fluoroolefin and a carbonate bond (-OC).
Alkyl vinyl ether or alkyl allyl ether having (＝ O) O— (where the hydrogen atom of the vinyl group or the allyl group may be substituted with a fluorine or chlorine atom. The carbonate bond is a C—C bond of the alkyl group) The alkyl group may be linear, branched or cyclic, and may have an etheric oxygen atom between the C-C bonds of the alkyl group.) Provided are a polymer electrolyte comprising a polymer as a matrix and a solution in which an electrolyte is dissolved in a non-aqueous solvent, and a lithium battery having the polymer electrolyte.

In the present specification, the “straight-chain, branched or cyclic alkyl group” includes a straight-chain or branched alkyl group partially having a cyclic structure. The same applies to the alkylene group.

In the present invention, the polymer electrolyte contains a solution of the electrolyte dissolved in a non-aqueous solvent in a matrix, and has a function of dissociating the electrolyte in the solvent to impart conductivity. Then, the matrix contains the electrolyte solution and swells to form a gel polymer electrolyte.

In the matrix of the polymer electrolyte of the present invention, the weight ratio of the polymerized unit based on fluoroolefin to the polymerized unit based on the alkyl vinyl ether or alkyl allyl ether having a carbonate bond, and further, if necessary, other The weight ratio of the components, the molecular weight of the copolymer, and the like, the miscibility with the electrolyte solution and the retention of the electrolyte solution, the adhesion of the polymer electrolyte to the current collector metal,
It can be appropriately selected depending on the strength, moldability, handleability, availability of the matrix, and the like. When the polymer electrolyte is formed into a film, the solubility or dispersibility of the matrix in the organic solvent used for the formation is also taken into consideration.

In the copolymer forming the matrix of the polymer electrolyte of the present invention, the content ratio of the polymerized unit based on fluoroolefin to the polymerized unit of alkyl vinyl ether or alkyl allyl ether having a carbonate bond is 10/90 by weight. ９７97/3 is preferred. When the polymerization unit based on fluoroolefin exceeds 97%, the crystallinity of the polymer increases, the flexibility is reduced, the solubility in the organic solvent used for molding is lost, the processability is reduced, and the electrolyte solution is reduced. Becomes difficult to penetrate into the polymer, and the electric conductivity of the polymer electrolyte decreases.

On the other hand, if it is less than 10%, the flexibility of the polymer electrolyte becomes too high or the strength is lowered, which is not preferable. In order to obtain a polymer electrolyte having particularly high strength, the content ratio of the polymerization unit based on the fluoroolefin and the polymerization unit based on the alkyl vinyl ether or alkyl allyl ether having a carbonate bond is 60/40 to 95/5 by weight ratio. Certain copolymers are preferred.

As the fluoroolefin in the present invention, various unsaturated compounds having a fluorine atom can be used, but tetrafluoroethylene and chlorotrifluoroethylene which are excellent in copolymerizability with the above-mentioned alkyl vinyl ether or alkyl allyl ether having a carbonate bond. Preferred are ethylene, vinylidene fluoride, 1,1-dichlorodifluoroethylene, 1,2-dichlorodifluoroethylene or hexafluoropropylene. Further, vinyl fluoride, trifluoroethylene, (perfluorobutyl) ethylene, (perfluorooctyl) propylene, or the like may be used in combination with these fluoroolefins.

Further, various types of polymer units based on the alkyl vinyl ether or alkyl allyl ether having a carbonate bond in the present invention can be used, but they are excellent in copolymerizability with the polymer units based on fluoroolefin. ,-(CXY-CZ ((CH
^{_{2) a OR 1 OC (=}} O) OR 2) - the polymerization unit represented by is preferably employed.

X, Y and Z are each independently hydrogen, fluorine or chlorine, and a is 0 or 1.
R ¹ represents a linear, branched or cyclic alkylene group, R ² represents a linear, branched or cyclic alkyl group, the total carbon number of R ¹ and R ² are 2 to 21, R ¹ May contain an etheric oxygen atom between the CC bonds. When R ² contains a cycloalkyl group, it may contain an etheric oxygen atom between the CC bonds of the cycloalkyl group. And R ¹
Alternatively, when R ² contains an etheric oxygen atom, the number of oxygen atoms is preferably 5 or less. Specific examples include a polymerized unit represented by the following formula.

[0017]

## STR1 ##-(CH ₂ —CH (OCH ₂ CH ₂ OCOOC)
_{H 3)) - - (CH} 2 -CH (OCH 2 CH (CH 3) OCOOC
_{H 3)) - - (CH} 2 -CH (OCH 2 CH 2 CH 2 CH 2 OCO
_{OCH 3)) - - (CH} 2 -CH (O (CH 2 CH 2 O) 2 COOCH
_{2 CH 3)) - - (} CH 2 -CH (O (CH 2 CH 2 O) 4 COOCH
₂ CH ₃₎₎ -

[0018]

## STR2 ##-(CH ₂ —CH (CH ₂ OCH ₂ CH ₂ OC
_{OOCH 3)) - - (CH} 2 -CH (CH 2 OCH 2 CH (CH 3) OC
_{OOCH 3)) - - (CH} 2 -CH (CH 2 OCH 2 CH 2 CH 2 CH 2
_{OCOOCH 3)) - - (CH} 2 -CH (CH 2 O (CH 2 CH 2 O) 2 CO
_{OCH 2 CH 3)) - -} (CH 2 -CH (CH 2 O (CH 2 CH 2 O) 4 CO
OCH ₂ CH ₃₎₎ -

[0019]

## STR3 ##-(CF ₂ —CF (OCH ₂ CH ₂ OCOOC)
_{H 3)) - - (CF} 2 -CF (OCH 2 CH (CH 3) OCOOC
_{H 3)) - - (CF} 2 -CF (OCH 2 CH 2 CH 2 CH 2 OCO
_{OCH 3)) - - (CF} 2 -CF (O (CH 2 CH 2 O) 2 COOCH
_{2 CH 3)) - - (} CF 2 -CF (O (CH 2 CH 2 O) 4 COOCH
₂ CH ₃₎₎ -

[0020]

## STR4 ##-(CHF-CF (OCH ₂ CH ₂ OCOOC)
_{H 3)) - - (CHF} -CF (O (CH 2 CH 2 O) 2 COOCH
_{3)) - - (CFCl-} CF (OCH 2 CH 2 OCOOCH
_{3)) - - (CFCl-} CF (O (CH 2 CH 2 O) 2 COOC
H ₂ CH ₃₎₎ -

The copolymer containing a polymerized unit based on a fluoroolefin and a polymerized unit based on an alkyl vinyl ether or an alkyl allyl ether having a carbonate bond contains a polymerized unit based on another monomer capable of forming a copolymer therewith. It may be a copolymer appropriately contained within a range not exceeding 40% by weight.

As other monomers, for example, hexafluoroacetone, perfluoro (methyl vinyl ether),
Perfluoro (propyl vinyl ether), ethylene,
Propylene, isobutylene, vinyl pivalate, vinyl acetate, vinyl benzoate, ethyl vinyl ether, butyl vinyl ether, cyclohexyl vinyl ether, ethyl allyl ether, cyclohexyl allyl ether, norbornadiene, crotonic acid and its esters, acrylic acid and its alkyl esters, methacrylic acid and And the alkyl esters thereof.

The number average molecular weight of the copolymer used in the present invention is preferably 10,000 to 1,000,000. When the molecular weight exceeds 1,000,000, the dissolution viscosity is extremely high, and it is difficult to uniformly mix the electrolyte with the solution in which the electrolyte is dissolved, or the holding amount of the solution in which the electrolyte is dissolved is reduced, and the electric conductivity of the polymer electrolyte is reduced. Not preferred. On the other hand, if it is less than 10,000, the mechanical strength of the polymer electrolyte is significantly reduced, which is not preferable. Particularly preferably, 30,000 to 500,000 is employed.

In the present invention, a polymer electrolyte in which a solution in which the above-mentioned electrolyte is dissolved in a matrix is used is used, but the content of the electrolyte solution in the polymer electrolyte is 30%.
~ 90% by weight is preferred. If the content is less than 30% by weight, the electric conductivity is undesirably low. If the content exceeds 90% by weight, the polymer electrolyte cannot maintain a solid state, which is not preferable. Particularly preferably, 40 to 80% by weight is employed.

When the polymer electrolyte of the present invention is applied to a battery, it can be suitably applied to a lithium battery in which the electrolyte solution is a solution comprising a solute of a lithium salt and a non-aqueous solvent capable of dissolving the lithium salt. The lithium battery having the polymer electrolyte of the present invention can be used as any of a primary battery and a secondary battery. In particular, when used as a secondary battery, a so-called lithium ion secondary battery using a lithium intercalation compound for the negative electrode is preferable, considering that lithium is not deposited on the negative electrode and safe.

In the lithium battery having the polymer electrolyte of the present invention, the solvent of the electrolyte solution is preferably a carbonate ester. 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.

As the electrolyte, ClO ₄ ⁻ , CF ₃ S
O ₃ ⁻ , BF ₄ ⁻ , PF ₆ ⁻ , AsF ₆ ⁻ , SbF ₆ ⁻ , CF ₃ C
It is preferable to use at least one of lithium salts having anions such as O ₂ ⁻ and (CF ₃ SO ₂ ) ₂ N ⁻ .

In the above-mentioned electrolyte solution, it is preferable that an electrolyte comprising a lithium salt is 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, 0.5 to 1.5 mol / l is selected.

The polymer electrolyte in the present invention can be prepared by various methods. For example, a copolymer forming a matrix is dissolved or uniformly dispersed in an organic solvent, and mixed with a solution in which a lithium salt is dissolved in a solvent (hereinafter, this mixed liquid is referred to as a mixed liquid for forming a polymer electrolyte). These two solutions are mixed, coated on a glass plate by a bar coater or a doctor blade, cast or spin-coated, and then dried to remove an organic solvent mainly dissolving or dispersing the copolymer, and a polymer electrolyte film. Get. If the solvent used for the lithium salt solution evaporates during drying,
The film is freshly impregnated with the solvent or the film is exposed to the solvent vapor to the desired composition.

As an organic solvent for dissolving or dispersing the copolymer, tetrahydrofuran (hereinafter referred to as THF), methyl ethyl ketone, methyl isobutyl ketone,
Toluene, xylene, N-methylpyrrolidone, acetone, acetonitrile, dimethyl carbonate, ethyl acetate, butyl acetate and the like can be used, but in order to selectively remove this organic solvent by drying, the boiling point of THF, acetone or the like is 100 ° C or less. Volatile organic solvents are preferred.

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 metals, lithium alloys, carbon materials, oxides mainly composed of metals of Groups 14 and 15 of the periodic table, carbon compounds, silicon carbide compounds, silicon oxide compounds , Titanium sulfide, boron carbide compounds and the like.

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 storing lithium ions in the case of a primary battery, and a material capable of storing 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 storing 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.
In addition, lithium can be contained in the negative electrode by a chemical or electrochemical method before the battery is assembled, or lithium can be contained by bringing lithium metal into contact with the negative electrode and / or the positive electrode when the battery is assembled.

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.

The positive and negative electrodes of 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 mixed solution for forming a polymer electrolyte is impregnated or applied to the positive electrode and the negative electrode so that the polymer electrolyte penetrates into the inside of the electrode layer. Alternatively, the electrode may be formed by mixing the mixed solution for forming a polymer electrolyte into a slurry and then applying the mixed solution to a 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,
A battery element can also be formed by applying a slurry containing an active material to a metal foil current collector, sandwiching it between a positive electrode and a negative electrode obtained by drying, and then absorbing a lithium salt 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.

When the polymer electrolyte of the present invention is used in an electrochromic device, for example, γ-butyrolactone, propylene carbonate, acetonitrile or the like is used as an organic solvent in the polymer matrix according to the present invention, and LiClO ₄ , LiBF ₄ or the like is used as an electrolyte. Is contained at a concentration of 0.2 to 1.5 mol / l to obtain a polymer electrolyte.

When the polymer electrolyte of the present invention is used for an aluminum electrolytic capacitor, for example, γ-butyrolactone, ethylene glycol, acetonitrile or the like is used as an organic solvent in the polymer matrix of the present invention.
For example, a salt composed of a base of R ¹ R ² R ³ R ⁴ NOH or R ⁵ R ⁶ R ⁷ N and an organic carboxylic acid (provided that R ¹ , R
² , R ³ , R ⁴ and R ⁵ , R ⁶ , R ⁷ are each independently an alkyl group having 1 to 5 carbon atoms, which may be the same or different), and 0.2 to 1.5 mol% By mixing the solutions, a polymer electrolyte can be obtained.

When the polymer electrolyte of the present invention is used for an electric double layer capacitor, the polymer matrix according to the present invention may contain, for example, γ-butyrolactone as an organic solvent.
Propylene carbonate, sulfolane, ethyl methyl carbonate, diethyl carbonate or the like is used alone or as a mixture, and is represented by, for example, a general formula R ¹ R ² R ³ R ⁴ N ⁺ or a general formula R ¹ R ² R ³ R ⁴ P ^+. Cation and Cl
O ₄ ⁻ , CF ₃ SO ₃ ⁻ , BF ₄ ⁻ , PF ₆ ⁻ , AsF ₆ ⁻ , Sb
_{^{F 6 -, CF 3 CO 2}} -, or _{(CF 3 SO 2) 2 N} - 4 quaternary onium salt having an anion such as (but, R ^1, R
² , R ³ and R ⁴ are each an alkyl group having 1 to 5 carbon atoms, which may be the same or different). Can be obtained.

[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 1 200 g of tert-butanol and CH ₂ ＣＨCHOCH ₂ CH ₂ OCOOCH _{3 were} placed in a stainless steel autoclave having an internal volume of 500 mL and equipped with a stirrer.
87.6 g and azobisisobutyronitrile 0.2 g
After charging and sufficiently replacing the gas phase with nitrogen, 68.7 g of chlorotrifluoroethylene was charged. Raise the temperature to 60 ° C,
Polymerized for 0 hours. The polymer solution obtained by purging the unreacted monomer is poured into water to precipitate the polymer, followed by washing and drying to recover the polymer, and polymerized units based on chlorotrifluoroethylene and CH ₂ ＣＨCHOCH ₂ CH
86 g of a copolymer (48/52 by weight) consisting of polymerized units based on ₂ OCOOCH ₃ was obtained. The intrinsic viscosity of the copolymer (in THF, 30 ° C .; the same applies hereinafter) is 0.40 d.
1 / g.

In an argon atmosphere, 10 parts by weight of the above copolymer was dissolved in 32 parts by weight of THF by heating while stirring. This is designated as solution 1. Next, LiPF ₆ was dissolved at a concentration of 1 mol / l in an argon atmosphere in a solvent in which ethylene carbonate and propylene carbonate were mixed at a volume ratio of 1/1. This is designated as solution 2.

5 parts by weight of solution 2 was added to 21 parts by weight of solution 1 and heated to 60 ° C. with stirring. This solution was applied on a glass plate with a bar coater, dried at 40 ° C. for 1 hour, and
F was removed to obtain a transparent polymer electrolyte film having a thickness of 100 μm. The composition of this film is a copolymer, a mixed solvent of ethylene carbonate / propylene carbonate,
LiPF ₆ was 50 / 44.3 / 5.7 by weight.

This film was peeled from the glass substrate, and the electrical conductivity was measured by an AC impedance method at 25 ° C. in an argon atmosphere. Electric conductivity is 6 × 10 ^-4 S / c
m.

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 above copolymer, 11 parts by weight of solution 2 and 70 parts by weight of THF were mixed in an argon atmosphere and heated with stirring. Got a slurry. This slurry has a thickness of 20
A bar coater was applied to an aluminum foil whose surface was roughened with a thickness of μm, followed by drying to obtain a positive electrode.

Mesophase carbon fiber powder (average diameter 8 μm, average length 50 μm, (0
02) 12 parts by weight of the spacing 0.336 nm), 6 parts by weight of the above copolymer, 11 parts by weight of solution 2 and 70 parts by weight of THF were mixed in an argon atmosphere and heated with stirring to obtain a slurry. . The slurry was applied to a copper foil having a thickness of 20 μm and the surface of which was roughened using a bar coater, and dried to obtain a negative electrode.

The above-mentioned polymer electrolyte film was 1.5 cm
Formed into corners, through which the effective electrode area 1 cm x 1 cm
The positive electrode and the negative electrode were opposed to each other, sandwiched and clamped between two 1.5 cm-thick 3 cm square polytetrafluoroethylene back plates, and the outside thereof was covered with an exterior film to assemble a lithium ion secondary battery element. This operation was all performed in an argon atmosphere.

The charge / discharge cycle test was performed under the conditions of 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 86%.

Example 2 Instead of charging tert-butanol and CH ₂ ＣＨCHOCH ₂ CH ₂ OCOOCH ₃ to a stainless steel autoclave with an internal volume of 500 mL and equipped with a stirrer, CHFCClCF ₂ CF ₂ Cl (manufactured by Asahi Glass Co., Ltd.)
Product Name: Asahi Clean AK-225cb) and a 200g and _{CF 2 = CFOCH 2 CH 2 OCOOCH} 3 120g
And a polymerized unit based on chlorotrifluoroethylene and CF ₂ ＣＦCFOCH ₂ were prepared in the same manner as in Example 1.
58 g of a copolymer composed of polymerized units based on CH ₂ OCH ₃ (63/37 by weight) was obtained. The intrinsic viscosity of this copolymer was 0.37 dl / g.

A polymer electrolyte film having a thickness of 100 μm was obtained in the same manner as in Example 1 except that this copolymer was used.
The electric conductivity of this film was measured in the same manner as in Example 1 and found to be 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 87%.

Example 3 CH ₂ ＣＨCHOCH ₂ CH ₂ OC
Instead of _{OOCH 3 CH 2 = CHOCH 2 CH} 2 CH 2
In the same manner as in Example 1 except that 73 g of CH ₂ OCOOCH ₃ was charged, a polymerization unit based on chlorotrifluoroethylene and CH ₂ ＣＨCHOCH ₂ CH ₂ CH ₂ CH ₂ OCOO
A copolymer comprising polymerized units based on CH ₃ (composition: 43/57 by weight, intrinsic viscosity: 0.3 dl / g) was obtained.

A polymer electrolyte film having a thickness of 100 μm was obtained in the same manner as in Example 1 except that this copolymer was used.
The electrical conductivity of this film was measured in the same manner as in Example 1 and found to be 8 × 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 85%.

Example 4 CH ₂ ＣＨCHOCH ₂ CH ₂ OC
CH ₂ ＣＨCHO (CH ₂ CH ₂ instead of OOCH ₃ )
O) ₂ COOCH ₃ Polymerized units based on chlorotrifluoroethylene and CH ₂ ＣＨCHO (CH ₂ CH ₂ O) ₂ COOCH ₃ were prepared in the same manner as in Example 1 except that 132 g of COOCH ₃ were charged.
(Polymer composition: 38/62 by weight, intrinsic viscosity: 0.3 dl / g).

A polymer electrolyte film having a thickness of 100 μm was obtained in the same manner as in Example 1 except that this copolymer was used.
The electrical conductivity of this film was measured in the same manner as in Example 1 and found to be 8 × 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 85%.

Example 5 A lithium secondary battery element was assembled 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, and a charge / discharge cycle test was performed as in Example 1. The capacity retention after 500 cycles was 84%.

[0062]

As is clear from the results of the examples, according to the present invention, a polymer electrolyte having high ionic conductivity can be obtained. When this polymer electrolyte is used, a lithium secondary battery having excellent cycle characteristics can be obtained. can get.

 ──────────────────────────────────────────────────の Continued on the front page (72) Inventor Katsuharu Ikeda 1150 Hazawa-cho, Kanagawa-ku, Yokohama-shi, Kanagawa Prefecture Inside the Central Research Laboratory of Asahi Glass Co., Ltd. (72) Inventor Kazuya Hiratsuka 1150 Hazawacho, Kanagawa-ku, Yokohama-shi, Kanagawa-ken Asahi Glass Co., Ltd.

Claims (6)

[Claims] An alkyl vinyl ether or an alkyl allyl ether having a carbonate unit (-OC (= O) O-) and a polymerization unit based on a fluoroolefin, wherein a hydrogen atom of the vinyl group or the allyl group is a fluorine atom or a chlorine atom. The carbonate bond is present between the C—C bonds of the alkyl group.The alkyl group may be linear, branched or cyclic,
An etheric oxygen atom may be present between the C bonds. )
A polymer electrolyte comprising a matrix containing a copolymer containing polymerized units based on a polymer and a solution in which the electrolyte is dissolved in a non-aqueous solvent. 2. The copolymer according to claim 1, wherein the weight ratio of the polymer units based on the fluoroolefin and the polymer units based on the alkyl vinyl ether or alkyl allyl ether is 10/20.
The polymer electrolyte according to claim 1, which has a molecular weight of 90 to 97/3. 3. The polymer electrolyte according to claim 1, wherein the fluoroolefin is tetrafluoroethylene, chlorotrifluoroethylene, vinylidene fluoride, dichlorodifluoroethylene or hexafluoropropylene. 4. The polymerization unit based on the alkyl vinyl ether or alkyl allyl ether is-(CXY-CZ).
((CH ₂ ) _a OR ¹ OC (＝ O) OR ² ) — (however, X, Y and Z are each independently a hydrogen atom, a fluorine atom or a chlorine atom, and a is 0 or 1. R ¹ is a linear, branched or cyclic alkylene group, R ² is a linear,
A branched or cyclic alkyl group, wherein the total number of carbon atoms of R ¹ and R ² is 2 to 21, R ¹ may contain an etheric oxygen atom between C—C bonds, and R ² is cycloalkyl When it contains a group, it may contain an etheric oxygen atom between CC bonds of the cycloalkyl group. ) Claim 1, 2 or 3
A polymer electrolyte as described in the above. 5. The polymer electrolyte according to claim 1, wherein the polymer electrolyte contains 30 to 90% by weight of a solution in which the electrolyte is dissolved. 6. A lithium battery having a positive electrode, a negative electrode and an electrolyte, wherein the electrolyte is the polymer electrolyte according to claim 1, 2, 3, 4 or 5.