JPH11126515A - High polymer solid electrolyte - Google Patents

Abstract

PROBLEM TO BE SOLVED: To increase transporting number of cations by composing the electrolyte of ion-property high polymer complex which is provided by a reaction between a solid electrolyte having two or more cationic terminal groups such as N,N-dimethylamino groups and a polyhalide compound such as ethylene dibromide. SOLUTION: The electrolyte is composed of ion-property high polymer complex which is provided by a reaction between a solid electrolyte having cationic terminal groups and a polyhalide compound. As cationic terminal groups, for example, cationic groups which can form fourth grade ammonium salt, for example, N,N-dimethylamino groups, pyridine groups, phosphonium groups, diazole groups, or imidazole groups are used, and the number of cationic terminal groups is two or more. As the polyhalide compound, bifunctional aliphatic polyhalide compound such as ethylene dibromide, or hexamethylene dibromide, or bifunctional aromatic polyhalide such as 1,4-dibromobenzene, or 1,3- dichlorobenzene is used.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solid polymer electrolyte applied to thin batteries, fuel cells, and the like.

[0002]

2. Description of the Related Art A polymer solid electrolyte is an ion-conductive polymer, in which an inorganic salt is dissolved in a solid polymer, and the inorganic salt dissociates into ions. It is a material through which the ions can conduct. Such a polymer solid electrolyte is a material which has been recently attracting attention because it has been applied to a thin, light, large-capacity battery, a display utilizing an electrochromic phenomenon, or a fuel cell.

[0003] Among the applications of these solid polymer electrolytes,
In particular, attention has been paid to the development of lithium or lithium ion batteries. In a conventional lithium or lithium ion battery, a liquid organic solvent such as ethylene carbonate or propylene carbonate is used as an electrolyte. However, since the electrolyte is a liquid electrolyte, problems such as liquid leakage or ignition from the battery have been a problem. . In this case, when a polymer solid electrolyte is used instead of a liquid electrolyte, an extremely thin battery can be produced, and further, there is an advantage that an accident such as liquid leakage does not occur.

[0004]

However, the ionic conductivity of the solid polymer electrolyte is generally disadvantageous in that it is lower than that of the liquid electrolyte because the ion conductivity is low because it is a solid. For example, polymers well known as polymer solid electrolytes include poly (ethylene oxide), poly (propylene oxide), and aliphatic polyesters. The lithium ion conductivity of these polymer solid electrolytes is determined by the supporting electrolyte. For example, when lithium perchlorate is used, it is about 10 ⁻⁵ to 10 ⁻⁶ S / cm at room temperature, which is considerably lower than that of a liquid electrolyte.

[0005] Among these polymer solid electrolytes, a material having the highest ionic conductivity is a polymer which partially cross-links poly (ethylene oxide) and has a relatively short poly (ethylene oxide) side chain. Although a material is known, its lithium ion conductivity is 10 ⁻⁴ S / c at room temperature.
m. For practical application to batteries, the lithium ion conductivity is desirably 10 ^-3 S / cm or more, but it is extremely difficult to exceed this value in practice.

Furthermore, the conduction of cations such as lithium ions in the solid polymer electrolyte is greatly affected by the viscoelastic properties of the polymer material because it is related to the molecular motion of the polymer chain. As a result, the ion conductivity is significantly reduced, so that the battery or the display does not operate when the temperature decreases in winter.

Further, since the conductivity of a cation such as lithium ion is related to the interaction with a polymer, its mobility is lower than that of a counter anion, and the transport number of the cation is generally 0.1. 2 to 0.4. Achieving a higher cation transport number, even though higher cation transport numbers on the electrodes are desirable, as they are related to the electrochemical reaction of cations in battery and display applications Is difficult with a general polymer solid electrolyte.

Therefore, an object of the present invention is to provide a novel polymer solid electrolyte which solves various problems of the conventional polymer solid electrolyte.

[0009]

In order to solve the above-mentioned problems, the present invention provides a polymer solid comprising an ionic polymer complex obtained by reacting a solid electrolyte having two or more cationic terminal groups with a polyhalide compound. Provide electrolyte.

Here, the cationic terminal group includes, for example, a cationic group capable of forming a quaternary ammonium salt, for example, N, N-dimethylamino group, pyridyl group, phosphonium group, diazole group, imidazole group, benzimidazole. Examples thereof include, but are not limited to, an N, N-dibutylamino group.

The number of cationic terminal groups is preferably 2 or more, and more preferably 2 to 4. This is to prevent the formation of a linear polymer and excessive occurrence of a crosslinking reaction.

Examples of the solid electrolyte having a cationic terminal group include, for example, poly (ethylene oxide), poly (propylene oxide), polyacetaldehyde, polyformaldehyde, and polyoxyethylene having a terminal group such as N, N-dimethylamino group. Polyethers such as decamethylene and poly (cyclohexyl ether); aliphatic polyesters such as poly (β-propiolactone), poly (ethylene succinate) and poly (ε-caprolactone);
Alternatively, a (phosphazene) derivative and the like can be mentioned, but it is not limited to these. Among these solid electrolytes, a combination of poly (ethylene oxide) having a terminal group such as N, N-dimethylamino group and dibromoethane is preferably used. This is because it forms linear polybrene.

The molecular weight of the solid electrolyte is generally from 2,000 to 100,000, preferably from 5,000 to 5,000.
Although it is in the range of 10,000, it does not particularly limit the molecular weight.

Examples of the polyhalide compound which is a partner of the solid polymer electrolyte include bifunctional aliphatic polyhalide compounds such as ethylene dibromide, hexamethylene dibromide, 1,4-cyclohexyl dibromide, and 1,4-dibromobenzene. Bifunctional aromatic polyhalides such as 1,1,3-dichlorobenzene and 1,4-dibromomethylbenzene can be used, but not limited thereto. For example, monofunctional monohalides may be used.

The number and type of the halogen functional groups are not particularly limited, but preferably, the halogen functional groups are Br, Cl, F, I, and the number of halogen functional groups is 2 to 2.
4.

By reacting the above-mentioned solid electrolyte having a cationic functional group at the terminal with a polyhalide compound, polybrene which is an ionic polymer complex can be obtained. A preferred structural formula of the ionic polymer complex is

[0017]

(Equation 1) It is represented by In the above structural formula, X represents a halogen group, and is preferably Br, Cl, F, or I. R ₁ to R ₅ are a hydrocarbon group having 1 to 5 carbon atoms, preferably 1 to 3 carbon atoms.
Is an alkyl group. R ₁ and R ₂ may be the same or different, preferably, R ₁ is CH ₃ , R ₂ is CH ₃ , R ₃
Is CH ₂ CH ₂ , R ₄ is CH ₂ , and R ₅ is CH ₂ CH ₂ . M is 2 to 100, preferably 5 to 10, and n is 2 to 50, preferably 5 to 20.

The reaction between the solid electrolyte and the polyhalide compound is carried out by dissolving these substances in an organic solvent, heating and distilling off the solvent under reduced pressure. As the organic solvent, dimethylformamide (DMF), dimethylsulfonamide (DMSO), acetonitrile, and the like can be used. However, the organic solvent is not limited to these, and may be anything that dissolves the substance. The heating temperature depends on the type of the substance, but is generally 50 to 150 ° C., and the heating time is 5 to 10 ° C.
Time. The distillation under reduced pressure is performed at 1 to 0.1 torr.

When polybrene, which is an ionic polymer complex, is used as a polymer solid electrolyte, not only inorganic salts such as lithium perchlorate dissolve, but also polyethers having cationic groups by applying an electric field, It can quickly move to the negative electrode while holding a cation such as lithium. Therefore, the electrochemical reaction of the cation at the negative electrode occurs promptly, and the mobility of the cation is remarkably improved, so that not only the ionic conductivity is greatly increased, but also the cation transport number can be increased.

The inorganic salt dissolved in the ionic polymer complex of the present invention includes, for example, lithium salts such as lithium perhydrochloride, lithium chloride and lithium trifluoromethanedisulfonate. Without limitation, metal salts such as potassium salts and calcium salts can be used. As the potassium salt, for example, potassium perchlorate, potassium chloride can be used,
As the calcium salt, for example, calcium acetate can be used, but is not limited thereto. The polymer conductive material in which an inorganic salt is dissolved can be applied to films, thin batteries, fuel cells, display materials, and the like.

[0021]

【Example】

(Example 1) 2 having N, N-dimethylamino group at both ends
Functional poly (ethylene oxide) (molecular weight 5,000
0) and ethylene dibromide at 1 mol / l each
And dissolved in dimethylformamide (DMF). After heating this solution at 100 ° C. for 1 day, DMF was distilled off under reduced pressure (0.1 torr) to obtain a solid quaternary chloride ionic polymer complex almost quantitatively. This complex polymer did not show a constant melting point and decomposed at about 250 ° C.

This complex polymer was dissolved again in DMF at a concentration of 10% and cast to obtain a thin film having a thickness of 0.15 mm. 10 in acetone
% Of lithium perchlorate at room temperature for 1 day in a solution of lithium perchlorate dissolved in
A film containing 5 wt% (0.1 mol / unit) was obtained. The ionic conductivity of this film was measured by the complex impedance method and found to be 3 × 10 ⁻³ S at 25 ° C.
/ Cm. Further, when the ionic conductivity of this film was measured at -20 ° C., it was 5 × 10 ⁻⁴ S / cm.
, Indicating high conductivity even at low temperatures. The transport number of lithium ions in this film is
When measured by the Flight method, it was found to be 0.
It turned out to be a high transit rate of 7.

Example 2 Poly (ethylene oxide (EO))-co having N, N-dimethylamino groups at both ends
An ionic polymer complex was obtained by reacting propylene oxide (PO) (the ratio of EO to PO was 7: 3) with ethylene dibromide according to the method described in Example 1. A film having a thickness of 0.1 mm was obtained from the ionic polymer complex by the method described in Example 1. This film was impregnated with 25% by weight of lithium perchlorate. The ionic conductivity of this film is 5 × at 25 ° C.
It was 10 ⁻³ S / cm, 6 × 10 ⁻⁶ S / cm at −20 ° C., and the transport number of lithium ion was 0.7.

Example 3 A film having a thickness of 0.1 mm was obtained by the method of Example 1 comprising poly (ethylene oxide) having a molecular weight of 5,000 having pyridyl groups at both ends and ethylene dibromide. . The film obtained by impregnating this film with 25% by weight of lithium perchlorate has an ionic conductivity of 4 × 10 ⁻³ S / cm at 25 ° C. and 3 × at −20 ° C.
10 ⁻⁴ S / cm and the transport number of lithium ions were 0.7.

[0025]

By applying an electric field, the solid polymer electrolyte of the present invention can quickly move to the negative electrode while holding cations such as lithium. Therefore, the electrochemical reaction of the cation at the negative electrode occurs promptly, and the mobility of the cation is remarkably improved, so that not only the ionic conductivity is greatly increased, but also the cation transport number can be increased.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI H01M 8/10 H01M 8/10 10/40 10/40 B

Claims (7)

[Claims] 1. A polymer solid electrolyte comprising an ionic polymer complex obtained by reacting a solid electrolyte having two or more cationic terminal groups with a polyhalide compound. 2. The polymer solid electrolyte according to claim 1, wherein the cationic terminal group is an N, N-dimethylamino group, a pyridyl group, a diazole group, an imidazole group, or a benzimidazole group. 3. The polymer solid electrolyte according to claim 1, wherein the polyhalide compound is an aliphatic or aromatic polyhalide. 4. The method according to claim 1, wherein the aliphatic or aromatic polyhalide is ethylene dibromide, hexamethylene dibromide,
4. The polymer solid electrolyte according to claim 1, which is 1,4-dibromobenzene or 1,3-dichlorobenzene. 5. The polymer solid electrolyte according to claim 1, represented by the formula 1. 6. A polymer conductive material obtained by dissolving an inorganic salt in the polymer solid electrolyte according to claim 1. 7. The polymer conductive material according to claim 6, wherein the inorganic salt is lithium perchlorate, lithium chloride, or lithium trifluoromethane disulfonate.