JP3335665B2 - Solid electrolyte - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solid electrolyte having excellent ionic conductivity and suitable for forming a thin battery or the like.

[0002]

2. Description of the Related Art Heretofore, there has been known a solid electrolyte in which an alkali metal salt is contained in a film made of polymethylsiloxane having an oligomer of ethylene oxide introduced into a side chain. However, there is a problem that the ion conductivity is inferior.

[0003]

SUMMARY OF THE INVENTION An object of the present invention is to develop a solid electrolyte composed of a polysiloxane-based film having excellent ionic conductivity and stable quality.

[0004]

According to the present invention, there is provided a solid electrolyte characterized in that a film comprising a polysiloxane having a hydrophobic group and a hydrophilic group contains a hydrophilic ether oligomer containing an alkali metal salt. Is what you do.

[0005]

When a polysiloxane having a hydrophobic group and a hydrophilic group is formed into a film, the hydrophobic group and the hydrophilic group act to form a film having a microphase-separated structure, on which a hydrophilic ether oligomer containing an alkali metal salt is formed. When it is contained, a membrane having a hydrophilic ether oligomer containing an alkali metal salt in a hydrophilic phase in a microphase separation structure in the membrane can be formed, and this membrane constitutes a solid electrolyte having excellent ionic conductivity. The excellent ionic conductivity is due to the active segmental movement of polysiloxane as a matrix polymer, the promotion of ion transport by its hydrophilic group, and the continuous use of ether oligomers held in microdomains in a sufficient space for ion transport. It is thought that it is because it exists in.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The solid electrolyte of the present invention comprises a polysiloxane-based film having a hydrophilic ether-based oligomer containing an alkali metal salt. As the polysiloxane forming the film, a polysiloxane having a hydrophobic group and a hydrophilic group in a side chain is used.

Examples of the above polysiloxane include those having the structural units represented by the following general formulas (I) and (II). Such a polysiloxane can be formed by, for example, a chemical polymerization method or an electrolytic polymerization method, and the average molecular weight is generally 20,000 to 8,000,000, but is not limited thereto.

In the above general formula, R ¹ is a hydrophobic group comprising an alkyl group having 3 or more carbon atoms or a phenyl group. R ² represents a terminal methylated polyethylene oxide group, a terminal methylated polypropylene oxide group, a terminal methylated ethylene oxide / propylene oxide copolymer group (random copolymer, block copolymer), a hydroxyl group, a carboxyl group, an amino group, a sulfo group. It is a hydrophilic group consisting of a group or the like.

[0009] As the hydrophilic group, from the viewpoint of improving the ion conductivity by suppressing the crystallization of the ether-based polymer, -X-CH ₃ or -Y-CH ₃ (wherein X is (CH ₂ C
H ₂ O) _m, Y is _{(CH 2 CH (CH 3)} O) n. )
A terminal methylated polyethylene oxide group, a terminal methylated polypropylene oxide group, a terminal methylated ethylene oxide / propylene oxide copolymer group, and the like are preferable. The degree of polymerization m, n of polyethylene oxide or polypropylene oxide in the formula is 2 to 2
0 is common but not limited to this.

As an alkali metal salt-containing hydrophilic ether-based oligomer to be contained in a polysiloxane film, any suitable one can be used. For example,
Examples include an ethylene oxide oligomer, a propylene oxide oligomer, and an ethylene oxide / propylene oxide copolymerized oligomer. The average molecular weight of the hydrophilic ether oligomer used is generally from 100 to 2,000, but is not limited thereto.

Examples of the alkali metal salt include cations such as Li ion, Na ion and K ion, I ion,
CF ₃ SO ₃ ion, BF ₄ ion, ClO ₄ ion, AlC
l ₄ ion, PF ₆ ion, AsF ₆ ion, such as those comprising a combination of an anion such as SCN ions.

The solid electrolyte is formed, for example, by dissolving a polysiloxane having a hydrophobic group and a hydrophilic group, a hydrophilic ether oligomer and an alkali metal salt using a polar solvent such as dimethylacetamide, and casting the solution using the solution. The film formation can be carried out by an appropriate method. In this case, the alkali metal salt is dissolved in a hydrophilic ether oligomer in advance using an organic solvent as necessary, and the solution is mixed and dissolved in a polysiloxane solution. It is preferable from the point that it is aggregated in the oligomer.

The amount of the hydrophilic ether oligomer used is:
Although it may be appropriately determined according to the purpose of use, it is generally 10 to 200 parts by weight, preferably 20 to 100 parts by weight, per 100 parts by weight of polysiloxane. The amount of the alkali metal salt used can also be appropriately determined according to the intended ionic conductivity and the like.
1 to 50 parts by weight is used per part by weight. The film thickness to be formed is arbitrary, and is usually 10 to 500 μm. The obtained membrane can be used as a solid electrolyte for forming various products such as batteries.

Example 1 In the general formula (I), R ¹ is a phenyl group and R ²
Is the degree of polymerization (m) of the polyethylene oxide portion is 2, 4,
6 or 8 is terminated methylated polyethylene oxide groups, number of polymerized moieties having R ¹ (x) is 3, weight average molecular weight approximately 2 million of polymerization of the portion having a R ² (y) is 1 Was dissolved in dimethylacetamide, and 30 parts per 100 parts by weight of polysiloxane was added thereto.
A viscous solution of LiClO ₄ -containing ethylene oxide oligomer was stirred and mixed so as to have a mixing ratio of 60 parts by weight, 60 parts by weight, or 100 parts by weight of ethylene oxide oligomer (weight average molecular weight: about 400) to prepare a homogeneous solution, and the casting method was employed. A film having a thickness of 50 μm was formed to obtain a solid electrolyte. The amount of LiClO ₄ used was such that the atomic ratio of O / Li in the ethylene oxide oligomer was 10.

COMPARATIVE EXAMPLE In the above formula (I), the portion having R ¹ has a polymerization number (x) of 0, and therefore consists of only the portion having R ^2, and the degree of polymerization (m) of the polyethylene oxide portion is 2 A polysiloxane having a weight average molecular weight of about 2,000,000, which is a 4, 6 or 8 terminal methylated polyethylene oxide group, is dissolved in dimethylacetamide, and the atomic ratio of O / Li in the polyethylene oxide of R ² introduced into the polysiloxane is added thereto. The LiClO ₄ was stirred and mixed to obtain a homogeneous solution, and a solid electrolyte was obtained using the same solution as in Example 1. Thus, it does not contain ethylene oxide oligomers.

Evaluation Test The solid electrolytes obtained in Example 1 and Comparative Example were measured for ionic conductivity using an AC impedance analyzer.
The results are shown in Table 1. A / B in the table means the ratio of polysiloxane / ethylene oxide oligomer. The degree of polymerization of the introduced polyethylene oxide means the degree of polymerization of the polyethylene oxide portion in the terminal methylated polyethylene oxide group introduced into the polysiloxane.

[0017]

[Table 1]

[0018]

According to the present invention, a polysiloxane film having a microphase-separated structure can be formed, and an ether-based oligomer containing an alkali metal salt can be contained in the hydrophilic phase, and the quality is excellent in ionic conductivity. The obtained solid electrolyte can be obtained.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H01B 1/06 H01M 6/18

Claims (1)

(57) [Claims] 1. A solid electrolyte comprising a film made of polysiloxane having a hydrophobic group and a hydrophilic group, containing a hydrophilic ether oligomer containing an alkali metal salt.