JPH09324114A - High-polymer solid electrolyte - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a high-polymer solid electrolyte that is composed of a polyether copolymer of a specific side-chain length and specific percentage composition, and has increased ionic conductivity and suitability as a material for electrochemical devices by compounding the copolymer with a soluble electrolytic salt compound. SOLUTION: This high-polymer solid electrolyte comprises (A) a solid random copolymer whose main chain is composed of 5-30mol% of a structural unit shown by formula I [(n) is a polymerization degree of 1-12] and 95-70mol% of a structural unit shown by formula II, and (B) an electrolytic salt compound soluble in the above-mentioned component (A). The polyether copolymer of component (A) has characteristics of number-average molecular weight in the range of from 100,000 to 2 millions, glass transition point of -60 deg.C when determined with a differential scanning calorimeter(DSC), and heat of fusion of 70 J/g or less. Component B is preferably a compound composed of a cation, such as a metal cation (e.g. such a cation as Li, Na, K, or Rb), ammonium ion, or the like, and an anion, such as chloride ion, nitrate ion, or the like. From this composition an electrolyte having excellent ion conductivity in addition to excellent processability and moldability is obtained.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a polymer solid electrolyte, and more particularly to a polymer solid electrolyte suitable as a material for electrochemical devices such as batteries, capacitors and sensors.

[0002]

2. Description of the Related Art
Electrolytes for electrochemical devices such as batteries, capacitors, and sensors are used in the form of solutions or pastes because of their ionic conductivity. It requires a separator impregnated with, so that problems have been pointed out, such as limitations on ultra-miniaturization and thinning of devices.
On the other hand, solid electrolytes such as inorganic crystalline substances, inorganic glass, and organic polymer substances have been proposed. Organic polymer-based materials are generally excellent in processability and moldability, and the resulting solid electrolyte has flexibility and bendability, and its progress has been made in terms of increasing the degree of freedom in the design of applied devices. Expected. However, at present, it is inferior to other materials in terms of ion conductivity.

For example, an attempt to incorporate a specific alkali metal salt into a mixture of epichlorohydrin rubber and a polyethylene glycol derivative having a low molecular weight and apply it to a polymer solid electrolyte is proposed in Japanese Patent Application Laid-Open No. 2-235957 including the present applicant. However, practically sufficient conductivity values have not been obtained. Further, JP-A-3-47833 and 4-
68064, average molecular weight 1,000 to 20,0
The polymer solid electrolyte obtained by crosslinking the polymer compound of No. 00 exhibits relatively good ionic conductivity in the practical temperature range, but improved ionic conductivity is still required.

Applicant's Japanese Patent Laid-Open Nos. 63-154736 and 63-241026, and European Patent Publication No. 43.
The polyether copolymer having an oligooxyethylene side chain described in No. 4011 suggests application to a polymer solid electrolyte or an antistatic material for plastics, but a polymer having a specific side chain length and a specific copolymer composition is suggested. There is no description or suggestion that the ion-conductive solid electrolyte has uniquely excellent properties.

[0005]

DISCLOSURE OF THE INVENTION The inventors of the present invention have found that a polyale copolymer having a specific composition ratio, in which oligoethylene glycol glycidyl ether having a specific side chain length is combined with ethylene oxide as a copolymerization component, is soluble in an electrolyte. It has been found that by incorporating a salt compound, a solid electrolyte having significantly increased ionic conductivity can be obtained as compared with a combination of other epoxides such as propylene oxide and epichlorohydrin.
That is, in the present invention, the main chain structure is 5 to 30 mol% of structural units of the following formula (1) and 95 to 70 mol% of structural units of the formula (2).
A solid random copolymer consisting of (1)
The degree of polymerization n of the oxyethylene unit in the side chain portion of the formula is 1 to 1
2, a polyether having an oligooxyethylene side chain having a number average molecular weight of 100,000 to 2,000,000, a glass transition point of −60 ° C. or less measured by a differential scanning calorimeter (DSC), and a heat of fusion of 70 J / g or less. A polymer solid electrolyte comprising a polymer and an electrolyte salt compound soluble in the copolymer, and a battery using the same.

[0006]

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[0007]

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The method for producing a polyether copolymer having an oligooxyethylene side chain (hereinafter abbreviated as a polyether copolymer) used in the present invention is described in the above-mentioned JP-A-63.
No. 154736. That is, using the catalyst system mainly composed of organoaluminum, the catalyst system mainly composed of organozinc, the organotin-phosphate ester condensate catalyst system, etc. as the ring-opening polymerization catalyst, the above formulas (1) and (2) are used. It can be obtained by reacting each monomer corresponding to the formula in the presence or absence of a solvent at a reaction temperature of 10 to 80 ° C. under stirring.

In the polyether copolymer used in the present invention, the molar ratio of the structural units (1) and (2) is 5 to 30 mol%, preferably 10 to 30 mol% and (2). ) Formula 95-70 mol%, preferably 90-70 mol% are suitable. When the molar ratio of the formula (2) exceeds 95 mol%, the glass transition point is increased and the structural unit of the formula (2) is crystallized, and the glass transition point is -60 ° C or lower and the heat of fusion is 70 J.
/ G or less cannot be maintained, and as a result, the ionic conductivity of the solid electrolyte is significantly deteriorated. It is generally known that the ionic conductivity is improved by lowering the crystallinity of polyethylene oxide, but it has been found that the polyether copolymer of the present invention has a significantly large effect of improving the ionic conductivity. . On the other hand, when the molar ratio of the formula (2) is less than 70 mol%, the softening temperature of the copolymer is lowered, and it becomes difficult to obtain a solid electrolyte at room temperature (for example, 20 ° C.). The glass transition point and the heat of fusion are measured by a differential scanning calorimeter (DSC). In the present invention, the glass transition point of the polyether copolymer is -60 ° C.
Or less, preferably −65 ° C. or less, heat of fusion 70 J / g
The following, preferably 50 J / g or less are suitable for use. When the glass transition point and the heat of fusion exceed the above values, the ionic conductivity is lowered.

In the present invention, the degree of polymerization n of the oxyethylene unit in the side chain portion of the formula (1) of the polyether copolymer is preferably 1 to 12, and when it exceeds 12, the ion conductivity of the solid electrolyte obtained is high. It is not preferable because it decreases. The molecular weight of the polyether copolymer is 100,000 to 200,000 in order to obtain processability, moldability, mechanical strength and flexibility.
100,000, preferably 200,000 to 1,500,000 are suitable. If the number average molecular weight is less than 100,000, the obtained electrolyte becomes liquid and liquid leakage occurs, which is not preferable for practical use.
If it exceeds 10,000, problems occur in workability and moldability.

The electrolyte salt compound used in the present invention may be any as long as it is soluble in the polyether copolymer of the present invention, but the following compounds are preferably used in the present invention. That is, metal cations, ammonium ions, amidinium ions, and cations selected from guanidinium ions, chloride ions, bromine ions, iodine ions, perchlorate ions, thiocyanate ions, tetrafluoroborate ions, Nitrate ion, As
F ₆ ^-, PF ₆ ^-, stearyl sulfonate ion, octylsulfonate ion, dodecylbenzenesulfonate ion, naphthalenesulfonate ion, dodecyl naphthalenesulfonate ion, tetracyano -p- quinodimethane ^{_{ion, R 1 SO 3 -, (}} R 1 SO 2) (R 2 S
O ₂ ) N ⁻ , (R ₁ SO ₂ ) (R ₂ SO ₂ ) (R ₃ SO
₂ ) C ⁻ and an anion selected from (R ₁ SO ₂ ) (R ₂ SO ₂ ) YC ⁻ . However, R ₁ , R ₂ , R ₃ , and Y are electron withdrawing groups.
Preferably, R ₁ , R ₂ and R ₃ are each independently a perfluoroalkyl group or a perfluoroaryl group having 1 to 6 carbon atoms, Y is a nitro group, a nitroso group, a carbonyl group, a carboxyl group, A cyano group or a trialkylammonium group. R ₁ , R ₂ and R ₃ may be the same or different. As the metal cation, a transition metal cation can be used. Preferably, a cation of a metal selected from Mn, Fe, Co, Ni, Cu, Zn and Ag metals is used. Also, Li,
Preferred results are also obtained using cations of metals selected from the Na, K, Rb, Cs, Mg, Ca and Ba metals. It is free to use two or more of the above-mentioned compounds in combination as the electrolyte salt compound.

In the present invention, the amount of the soluble electrolyte salt compound used is such that the total number of moles of ethylene oxide units including the main chain and side chains of the polyether copolymer is the number of moles of soluble electrolyte salt compound / ethylene oxide unit. The total number of moles of is 0.0001-5, preferably 0.001-
A range of 0.5 is good. If this value exceeds 5, the processability, moldability, and mechanical strength and flexibility of the obtained solid electrolyte will deteriorate, and the ion conductivity will also decrease.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The method for producing a solid polymer electrolyte according to the present invention is not particularly limited, but usually the respective components are mixed mechanically or dissolved in a solvent and mixed, and then the solvent is removed. It is manufactured by such a method. Various kneaders, open rolls,
An extruder or the like can be used arbitrarily. When produced using a solvent, various polar solvents, for example, tetrahydrofuran, acetone, acetonitrile, dimethylformamide, dimethyl sulfoxide, dioxane, methyl ethyl ketone,
Methyl isobutyl ketone or the like is used alone or as a mixture. The concentration of the solution is not particularly limited, but is 1 to 50% by weight.
Is preferred. Further, the solid electrolyte may be crosslinked if necessary. As a crosslinking agent at the time of crosslinking the copolymer, 2-4-tolylene diisocyanate, 2-6-tolylene diisocyanate, 4-4-diphenylmethane diisocyanate,
An isocyanate compound such as hexamethylene diisocyanate can be exemplified.

When the polymer solid electrolyte shown in the present invention is used, a solid electrolyte in the form of a large-area thin film can be easily obtained with the flexibility, which is an advantage of the polymer. For example, it is possible to manufacture a battery using the polymer electrolyte shown in the present invention.
In this case, examples of the positive electrode material include lithium-manganese composite oxide, lithium cobalt oxide, vanadium pentoxide, polyacene, polypyrene, polyaniline, polyphenylene, polyphenylene sulfide, polyphenylene oxide, polypyrrole, polyfuran, and polyazulene. Examples of the negative electrode material include an intercalation compound in which lithium is intercalated between graphite or carbon layers, lithium metal, and a lithium-lead alloy. Example 8 shows an example of the battery. In addition, utilization of a cation such as an alkali metal ion, a Cu ion, a Ca ion, and a Mg ion as a diaphragm of an ion electrode using high electric conductivity can be considered.

[0015]

【Example】

Examples 1 to 4 Comparative Examples 1 to 5 1 g of the polyether copolymer shown in Tables 1 and 2 (polyethylene oxide in Comparative Example 3) was added to 20 g of tetrahydrofuran.
A solution of lithium perchlorate in tetrahydrofuran was mixed so as to be dissolved in ml and the total number of moles of the soluble electrolyte salt compound / the total number of ethylene oxide units was 0.005.
This mixture was cast on a polytetrafluoroethylene mold and dried sufficiently to obtain a film. The results of Examples and Comparative Examples are summarized in Tables 1 and 2, respectively. In Tables 1 and 2, the glass transition point and the heat of fusion were measured by using a differential scanning calorimeter DSC8230B manufactured by Rigaku Denki Co., Ltd., in a nitrogen atmosphere, in a temperature range of −100 to 80 ° C., and a heating rate of 10 ° C.
/ Min. The conductivity σ was measured by a complex impedance method using platinum as an electrode and an AC method with a voltage of 0.5 V and a frequency range of 5 Hz to 1 MHz.

Example 5 1 g of a polyether copolymer having 5 mol% of the structural unit of the formula (1) and 95 mol% of the structural unit of the formula (2) was dissolved in 20 ml of acetonitrile, and lithium bistrifluoromethanesulfonylimide ( Hereinafter, the acetonitrile solution of LiTFSI was mixed so that the total number of moles of ((hereinafter referred to as LiTFSI)) / the total number of moles of ethylene oxide units was 0.005. This mixture was cast on a polytetrafluoroethylene mold and dried sufficiently to obtain a film. The characteristics of the film were measured in the same manner as in Examples 1 to 4. 3
The conductivity of the solid electrolyte at 0 ° C. is 4.0 × 10 ⁻⁴ S /
cm.

Example 6 1 g of a polyether copolymer having 12 mol% of the structural unit of the formula (1) and 88 mol% of the structural unit of the formula (2) was dissolved in 20 ml of acetonitrile, and the mol number of LiTFSI / ethylene oxide unit was dissolved. L so that the total number of moles of
A mixture of iTFSI in acetonitrile was mixed. This mixture was cast on a polytetrafluoroethylene mold and dried sufficiently to obtain a film. The characteristics of the film were measured in the same manner as in Examples 1 to 4.

Example 7 A film was obtained in the same manner as in Example 6 except that the number of moles of LiTFSI / the total number of moles of ethylene oxide units was 0.05. The characteristics of the film were measured in the same manner as in Examples 1 to 4. It is clear that the electrolyte of the present invention has particularly excellent ionic conductivity in comparison with Comparative Examples.

Example 8 A secondary battery was constructed by using the polymer solid electrolyte obtained in Example 3 as an electrolyte, a lithium metal foil as a negative electrode, and lithium cobalt oxide (LiCoO ₂ ) as a positive electrode.
The size of the polymer solid electrolyte is 10 mm × 10 mm × 1 mm. The size of the lithium foil is 10 mm X 10 mm X 0.1 mm. Lithium cobaltate was prepared by mixing predetermined amounts of lithium carbonate and cobalt carbonate powder and then firing at 900 ° C. for 5 hours. Next, this was crushed, and an appropriate amount of acetylene black was added, and then press-molded to a pressure of 300 Kgw / cm ² to 10 mm X 10 mm X 2 mm to obtain a battery positive electrode. The polymer solid electrolyte obtained in Example 3 was sandwiched between a lithium metal foil and a lithium cobaltate plate, and the charge / discharge characteristics of the battery were examined while applying a pressure of 10 Kgw / cm ² so that the interface was in close contact. The initial discharge voltage is 3.2 V and the discharge current is 0.4.
It was mA / cm ² and could be charged at 0.3 mA / cm ² . Since the battery of this embodiment can be easily manufactured to be thin, it is lightweight and has a large capacity.

[0020]

[Table 1]

[0021]

[Table 2]

[0022]

The polymer solid electrolyte of the present invention is excellent in workability, moldability, mechanical strength, flexibility and the like, and its ionic conductivity is remarkably improved. Therefore, application to electronic devices such as solid-state batteries, large-capacity capacitors, and display devices such as electrochromic displays is expected.

[Procedure amendment]

[Submission date] May 1, 1997

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Claim 5

[Correction method] Change

[Correction contents]

[Procedure amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0011

[Correction method] Change

[Correction contents]

The electrolyte salt compound used in the present invention may be any as long as it is soluble in the polyether copolymer of the present invention, but the following compounds are preferably used in the present invention. That is, metal cations, ammonium ions, amidinium ions, and cations selected from guanidinium ions, chloride ions, bromine ions, iodine ions, perchlorate ions, thiocyanate ions, tetrafluoroborate ions, Nitrate ion, As
F ₆ ⁻ , PF ₆ ⁻ , stearyl sulfonate ion, octyl sulfonate ion, dodecylbenzene sulfonate ion, naphthalene sulfonate ion, dodecyl naphthalene sulfonate ion, 7,7,8,8-tetracyano-
p-quinodimethane ion, R ₁ SO ₃ ⁻ , (R ₁ S
O ₂ ) (R ₂ SO ₂ ) N ⁻ , (R ₁ SO ₂ ) (R ₂ SO
_{2) (R 3 SO 2)} C -, and _{(R 1 SO 2) (R} 2 S
O ₂₎ YC ^- compound comprising the selected anions from the like. However, R ₁ , R ₂ , R ₃ , and Y are electron withdrawing groups. Preferably, R ₁ , R ₂ and R ₃ are each independently a perfluoroalkyl group or a perfluoroaryl group having 1 to 6 carbon atoms, Y is a nitro group, a nitroso group, a carbonyl group, a carboxyl group or Cyano group
It is. R ₁ , R ₂ , and R ₃ are the same,
It may be different. As the metal cation, a transition metal cation can be used. Preferably Mn, Fe,
A cation of a metal selected from Co, Ni, Cu, Zn and Ag metals is used. In addition, Li, Na, K, Rb,
Preferred results are also obtained using cations of metals selected from the Cs, Mg, Ca and Ba metals. It is free to use two or more of the above-mentioned compounds in combination as the electrolyte salt compound.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Reference number within the agency FI Technical indication location H01M 10/40 H01G 9/02 331G (72) Inventor Yasuo Matoba 9 Kashido-cho, Nishinomiya-shi, Hyogo Prefecture 8-104 (72) Inventor Masayoshi Watanabe 3-401 30 Oromatsu-cho, Nishi-ku, Yokohama-shi Kanagawa Prefecture 3-401 (72) Inventor Naohiko Sakashita 2-chome, Higashi-Mikuni 2-chome, 18-204, Yodogawa-ku, Osaka

Claims (10)

[Claims] The main chain structure is represented by the following structural unit (1):
A solid random copolymer comprising 30 mol% and structural units of the formula (2) of 95 to 70 mol%, wherein the degree of polymerization n of the oxyethylene unit of the side chain portion of the formula (1) is 1 to 12, Number average molecular weight of 100,000 to 2,000,000, differential scanning calorimeter (DS
It comprises a polyether copolymer having an oligooxyethylene side chain having a glass transition point of −60 ° C. or less and a heat of fusion of 70 J / g or less measured in C), and an electrolyte salt compound soluble in the copolymer. Characteristic polymer solid electrolyte. Embedded image Embedded image 2. The solid polymer electrolyte according to claim 1, wherein a polyether copolymer having a structural unit of the formula (1) of 10 to 30 mol% and a structural unit of the formula (2) of 90 to 70 mol% is used. 3. The polymer solid electrolyte according to claim 1, wherein a polyether copolymer having a glass transition point of −65 ° C. or lower and a heat of fusion of 50 J / g or lower is used. 4. The electrolyte salt compound is a cation selected from metal cations, ammonium ions, amidinium ions, and guanidinium ions, and chloride ions, bromine ions, iodine ions, perchlorate ions, and thiocyanate ions. , Tetrafluoroborate ion, nitrate ion, As
F ₆ ^-, PF ₆ ^-, stearyl sulfonate ion, octylsulfonate ion, dodecylbenzenesulfonate ion, naphthalenesulfonate ion, dodecyl naphthalenesulfonate ion, tetracyano -p- quinodimethane ^{_{ion, R 1 SO 3 -, (}} R 1 SO 2) (R 2 S
O ₂ ) N ⁻ , (R ₁ SO ₂ ) (R ₂ SO ₂ ) (R ₃ SO
_{2. A} compound consisting of ₂ ) C ⁻ and an anion selected from (R ₁ SO ₂ ) (R ₂ SO ₂ ) YC ⁻ .
3. The polymer solid electrolyte according to any one of 3 above. Where R ₁ ,
R ₂ , R ₃ , and Y are electron withdrawing groups. 5. R ₁ , R ₂ , and R ₃ are each independently a perfluoroalkyl group or a perfluoroaryl group having 1 to 6 carbon atoms, and Y is a nitro group, a nitroso group, a carbonyl group, The polymer solid electrolyte according to claim 4, which is a carboxyl group, a cyano group, or a trialkylammonium group. 6. The metal cation is Li, Na, K, Rb,
The solid polymer electrolyte according to claim 4, which is a cation of a metal selected from Cs, Mg, Ca, and Ba metals. 7. The solid polymer electrolyte according to claim 4, wherein the metal cation is a cation of a transition metal. 8. The metal cation is Mn, Fe, Co, N.
The solid polymer electrolyte according to claim 4, which is a cation of a metal selected from i, Cu, Zn, and Ag metals. 9. The compounding ratio of the electrolyte salt compound and the polyether copolymer is such that the value of the number of moles of the electrolyte salt compound / the total number of moles of ethylene oxide units is 0.0001 to 5. The polymer solid electrolyte described. 10. A battery using the polymer solid electrolyte according to claim 1.