JPS62140306A - Solid electrolyte composition - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to an ionically conductive solid electrolyte composition.

[Background of the Invention] Liquid electrolytes have conventionally been used in primary batteries, secondary batteries, fuel cells, electrochromic (ECD) display elements, and the like. However, liquid electrolytes have problems with long-term reliability because liquid electrolytes tend to leak to the outside of components and elute electrode materials.

On the other hand, solid electrolytes have the advantage that they do not have such problems and can simplify the structure of the components of each device, and furthermore, can be made thinner, making it possible to reduce the weight and size of the components. These features meet the demands for various electronic components that are small, lightweight, and highly reliable as electronics advances, and research and development efforts are therefore being actively conducted.

As solid electrolyte materials, mainly inorganic materials such as β-alumina, silver rubidium oxide, lithium iodide, etc. have been known so far. However, inorganic materials can be formed into any shape,
Since it is often difficult to form a film and is generally expensive, there are many problems in practical use.

On the other hand, solid electrolytes using various polymers have been proposed since polymers have the advantage that a uniform thin film can be easily processed into any shape. That is, solid electrolyte compositions consisting of a combination of polymers such as polyethylene oxide, polyepichlorohydrin, polyethylene succinate, and inorganic ionic salts such as Li and Na, and batteries using these compositions have already been proposed ( Examples: JP-A No. 58-75.779, JP-A No. 58-108667, JP-A No. 58-188062, No. 5
No. 8-188063, No. 59-71263). However, since these compositions do not have sufficient ionic conductivity, they have not been put into practical use at the current stage.

In addition, as a method for increasing the electrical conductivity of a composition of a polymer and an inorganic ionic salt, a method has been proposed in which an appropriate amount of an organic solvent is added to the composition while maintaining an apparently solid state (e.g. , JP-A-57-137359, JP-A No. 57-13
No. 7360, No. 57-143355, No. 57-143
No. 356, No. 59-149601, No. 59-2300
31 etc.). However, compositions containing organic solvents have the disadvantage that even if the content of the organic solvent is small, the solvent evaporates little by little over a long period of time, resulting in deterioration of properties.

Furthermore, a solid electrolyte has been proposed in which a secondary polymer is added to a composition of a polymer and an alkali salt, and a network structure is formed by light irradiation or heat calendering (Japanese Patent Laid-Open No. 58
-82477).

Furthermore, it has been reported that a composition using linear polyethyleneimine as a polymer and an ionic salt such as an alkali metal is effective as a solid electrolyte (Macr.
Omolecules Vol, 18.825~B2
? (1985)). However, linear polyethyleneimine is crystalline, and the ionic conductivity of solid electrolyte compositions using it cannot be said to be sufficient.

[Objective and Structure of the Invention] The present inventor has conducted research with the aim of obtaining a solid electrolyte composition that uses polyethyleneimine as a polymer and has high ionic conductivity and excellent moldability, and has developed the present invention. invention has been achieved.

That is, the present inventor focused on the fact that linear polyethyleneimine is crystalline, whereas branched polyethyleneimine is woody and amorphous. We discovered that a composition of a crosslinked polymer formed by crosslinking with an epoxy compound and an inorganic electrolyte has high ionic conductivity and excellent moldability,
We have arrived at the present invention.

That is, the present invention resides in a solid electrolyte composition characterized by containing a crosslinked polymer formed by crosslinking branched polyethyleneimine with a polyfunctional epoxy compound and an inorganic electrolyte.

The branched polyethyleneimine in the solid electrolyte composition of the present invention has branches containing primary, secondary, and tertiary 7-mino groups, and is a polymer represented by the following general formula. .

H2 [cH2CH2Nh+CI2 CH2NM+-yN
- Branched polyethyleneimine having the general formula 1 is already known. The molecular weight can also be varied within a wide range from hundreds to millions. Preferred branched polyethyleneimines for use in the present invention have a molecular weight of 300 to 100,000, preferably 10
It is within the range of 00 to 100,000.

In addition, in a typical example of a branched polyethyleneimine represented by the general formula 1, the molar ratio of primary, secondary, and tertiary amine groups is approximately 1:2: It becomes 1.

The polyfunctional epoxy compound used for crosslinking the branched polyethyleneimine can be arbitrarily selected from known polyfunctional degradable epoxy compounds. Polyfunctional epoxy compounds particularly suitable for the purpose of crosslinking branched polyethyleneimines in the present invention include jepoxy alkanes (
(e.g., 1.3-jepoxybutane and 1.7-jepoxyoctane), polyalkylene glycol type epoxy resin (e.g., polyethylene glycol type epoxy resin), bispheno-1A type epoxy resin, bisphenol F type epoxy resin, Novolak epoxy resin obtained by the reaction of novolac resin and epihalohydrin, polyfunctional phenol type epoxy resin, glycidylamine type polyfunctional epoxy resin, diglycidyl ether compound obtained by the reaction of resorcinol and epihalohydrin, cycloaliphatic epoxy resin, Hydantoin type epoxy resins can be mentioned.

The polyfunctional epoxy compound is preferably used in an iM ratio of 1 to 50% by weight, and particularly preferably 2 to 20% by weight, based on the branched polyethyleneimine. preferable. In addition, the polyfunctional epoxy compound has a value of 0.1 to 5
It is preferably used in a proportion of 0 mol%, and particularly preferably in a proportion of 0.5 to 20 mol%. If the amount of the polyfunctional epoxy compound is too small, the composition becomes soft and, in some cases, becomes liquid (branched polyethyleneimine itself, which does not have a high molecular weight, is liquid at room temperature). Also, if the amount is too high, the composition will become brittle and the moldability will deteriorate.
This results in poor Jt film properties.

There are no particular limitations on the inorganic electrolyte contained in the electrolyte composition of the present invention, but examples include L i CI Oa, LiI,
Li5CN, LiBFa, LiAsF5, Li
CF:+ SO:+, LiPF6, NaI, Na5
CN, NaBr, KI, Cs5CN, AgNO3, Cu
Electrolytes such as C1, Mg (C, uoa)2 can be used.

The inorganic electrolyte is preferably used in an amount ranging from 0.1 to 100 mol%, more preferably from 0.5 to 20 mol%, per ethyleneimine monomer unit of polyethyleneimine.
It is particularly preferred to use amounts in the range of . If the amount of inorganic electrolyte used is too large, the excess inorganic electrolyte will not dissociate and will simply be mixed in the polyethyleneimine structure, resulting in a decrease in ionic conductivity.

The solid electrolyte composition of the present invention can be produced, for example, by first uniformly mixing a branched polyethyleneimine and an inorganic electrolyte, and then adding a polyfunctional epoxy compound to the resulting mixture to cause a crosslinking reaction. can do. In addition, in these steps, if necessary (for example,
When the branched polyethyleneimine is solid), a good solvent such as alcohol (eg, methanol) may be used.

The crosslinking reaction is preferably carried out under heating.

In addition, when it is desired to form the solid electrolyte composition of the present invention into a form such as a sheet, it is preferable to form the solid electrolyte composition into the desired form before the completion of the crosslinking reaction.

[Effects of the Invention] Since the solid electrolyte composition of the present invention has high ionic conductivity and excellent moldability, it is extremely suitable as a solid electrolyte for use in secondary batteries, secondary batteries, fuel cells, electrochromic display elements, etc. It is useful, and since it is a solid electrolyte that does not contain a liquid component, it has excellent storage stability and can be used for a long period of time.

[Example] [Example 1] Branched polyethyleneimine (trade name: Epomin 5P-3
00, manufactured by Nippon Shokubai Chemical Industry ■, molecular weight = 30000) I
g and LiC Oa 0, 123 g (5 mol % per monomer unit of polyethyleneimine) were dissolved in 4 cc of methanol, and a polyethylene glycol type epoxy compound (trade name: DER732, Dowban Chemical Co., Ltd.) was dissolved in the resulting solution. 0.056 g (per unit of polyethyleneimine monomer: 0.75 mol %) was added and mixed uniformly. This mixture was cast into a glass Petri dish, methanol was distilled off under a nitrogen stream, and the mixture was further dried under vacuum at 100° C. to obtain a transparent film having a thickness of 4001 Lm.

The above membrane was shaped into a disk with a diameter of 15 mm, conductive silver paste was applied on both sides to form electrodes, and an alternating current voltage was applied thereto to calculate the ionic conductivity using the complex impedance method. As a result, at 23℃, 0,25X 10-'S/
Cm(7) values were obtained. Note that S=Ω−゛.

[Example 2] A transparent film was obtained in the same manner as in Example 1 except that the amount of L i CI Oa was 2.5 mol %.

The conductivity of this film was measured in the same manner as in Example 1 and was 0.54X10-'S/cm (at 23°C).
obtained the value of

[Comparative Example 1] Example 1 except that inorganic salt (LiCuOa) was not used.
A transparent film was obtained in the same manner as above.

The conductivity of this film was measured in the same manner as in Example 1 and was found to be 0.42X 10-9S/cm (25°C).
obtained the value of

[Comparative Example 2] A transparent film was obtained in the same manner as in Example 1 except that linear polyethyleneimine was used instead of branched polyethyleneimine as the polymer material. In addition, linear polyethyleneimine is described in Macromolecules Vol. 5゜10.
It was synthesized with reference to p. 8 (1972), and its molecular weight was about 2,000.

The electrical conductivity of this film was measured in the same manner as in Example 1 and found to be 0.54 x 10-8 S/cm (30
℃) was obtained. In other words, the conductivity should increase if the measurement temperature is increased, but when linear polyethyleneimine is used instead of branched polyethyleneimine, the conductivity does not increase even though the measurement temperature increases. It is declining.

Claims (1)

[Scope of Claims] 1. A solid electrolyte composition comprising a crosslinked polymer obtained by crosslinking branched polyethyleneimine with a polyfunctional epoxy compound and an inorganic electrolyte. 2. Branched polyethyleneimine has the following general formula: ▲ Formula,
The solid electrolyte composition according to claim 1, characterized in that it has a chemical formula, table, etc. ▼. 3. Branched polyethyleneimine has a molecular weight of 300 to 10,000
3. The solid electrolyte composition according to claim 1 or 2, wherein the solid electrolyte composition has a molecular weight within a range of 0. 4. The solid electrolyte composition according to claim 1 or 2, wherein the polyfunctional epoxy compound is a diepoxy alkane or polyalkylene glycol type epoxy resin. 5. The solid electrolyte composition according to claim 1 or 2, wherein the polyfunctional epoxy compound is used in a proportion of 1 to 50 mol% relative to the branched polyethyleneimine. thing. 6. Inorganic electrolyte is LiClO_4, LiI, LiBF
_4, LiAsF_6, LiCF_3SO_3, LiP
F_6, LiSCN, NaI, NaSCN, NaBr,
3. The solid electrolyte composition according to claim 1 or 2, wherein the solid electrolyte composition is selected from the group consisting of KI, CsSCN, AgNO_3, CuCl_2, and Mg(ClO_4)_2. 7. Claim 1 or 2, characterized in that the inorganic electrolyte is contained in an amount ranging from 0.1 to 100 mol% per monomer unit of the branched polyethyleneimine. solid electrolyte composition.