JPH03196408A - Ion conductive 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 [Industrial Field of Application] The present invention relates to an ionically conductive solid electrolyte composition. The ion conductive solid electrolyte composition of the present invention can be used as an electrolyte for secondary batteries, secondary batteries, electrochromic display elements, etc.

[Conventional technology]

BACKGROUND ART Liquid electrolytes have conventionally been used as electrolytes for primary batteries, secondary batteries, electrochromic display (hereinafter simply referred to as ECD) elements, and the like.

However, liquid electrolytes have problems with long-term reliability because they tend to leak to the outside of the component or elute electrode materials.

On the other hand, solid electrolytes do not have the above-mentioned problems, can simplify the configuration of parts in each device, and have the advantage of being thinner, allowing parts to be lighter and smaller. .

Conventionally, inorganic substances such as β-alumina, silver oxide, rubidium, and lithium iodide have been used as materials for these solid electrolytes, but inorganic substances are sometimes difficult to form into arbitrary shapes and form films. There are many problems and there are many problems in practical use because they are generally expensive.

On the other hand, solid polymer electrolytes (hereinafter referred to simply as SPE), which are based on polymers instead of inorganic substances, have the advantage of being a uniform thin film that can be easily processed into any shape.
SPEs using various polymers as bases have been studied, and batteries or ECD devices using them have been proposed.

A conventionally well-known SPE is a composite of a base polymer of high molecular weight polyethylene oxide (hereinafter simply referred to as PEO) and an inorganic ionic salt.

Since this PEO-based SPE has crystallinity at room temperature, it does not show good ion conductivity, and various improvements have been made. Many SPEs have been proposed that use difficult polymers as base polymers and aim to improve and improve ion conductivity.

For example, as a base polymer, JP-A-58-82477
In JP 58-188062, a blend of a conversational polymer and a network-structured polymer is described; in JP 58-188062, a blend of PEO and polymethacroyloxybenzoate is used;
Publication No. 216462 discloses a copolymer of dimethylsiloxane and PEO, Publication No. 61-47113 discloses a composite of polyethylene oxide methacryloyl polymer and metal salt of polymethacrylate, Publication No. 61-260557 discloses a phosphate ester macromer, Publication No. 285954 discloses a cured product of a composition containing polyethylene glycol diacrylate, Publication No. 63-136408 discloses a cured product of a composition containing polyethylene glycol diacrylate, Publication No. 63-136408 discloses a cured product of a composition containing polyethylene glycol diacrylate, Publication No. 63-136409 discloses a modified polysiloxane with ethylene oxide, and Publication No. 1-10747 discloses a cured product of a composition containing polyethylene glycol diacrylate. Allylated polyether glycol polymers have been proposed.

Furthermore, SPE in which low molecular weight polyethylene oxide is blended with other base polymers to improve ionic conductivity has been disclosed, for example, in U.S. Pat. No. 4,654,279 and JP-A-63
This method has been proposed in JP-A-139226, JP-A-1-107470, and the like.

However, this method of adding low molecular weight polyethylene oxide to improve ionic conductivity may deteriorate the mechanical properties of the solid electrolyte depending on the amount added.

[Problem to be solved by the invention]

When SPE is used in batteries, electrochromics, etc., in addition to ionic conductivity, its mechanical properties are also important factors. For example, focusing on the film-forming ability of polymers, development is underway to apply them to ion-conducting diaphragms for ultra-thin lithium batteries, but in this case, the mechanical strength of the SPE film is insufficient. It is easily damaged during the lamination process with the negative electrode, positive electrode sheet, etc. during battery manufacturing, and if damage occurs, the negative electrode and positive electrode will short-circuit, resulting in a significant drop in battery performance. Furthermore, during discharging in a lithium battery, lithium metal in the negative electrode active material is eluted as lithium ions, and the volume of the negative electrode decreases, while lithium ions are incorporated into the positive electrode active material, increasing the volume of the positive electrode. Therefore, the ion conductive diaphragm is required to have mechanical properties that can accommodate these deformations.

Furthermore, when SPE is applied not only to the ion-conductive diaphragm of ultra-thin lithium batteries but also to the separator of spiral-shaped lithium batteries for cameras, even stricter mechanical properties such as strength are required.

As mentioned above, there is currently a demand for SPE not only to improve its ionic conductivity but also to improve its mechanical properties such as strength. In order to meet these demands, all of the SPEs that have been proposed in the past still have insufficient ionic conductivity, or do not necessarily have satisfactory properties in terms of mechanical strength, stability, etc. .

An object of the present invention is to improve the drawbacks of conventional solid polymer electrolytes and to provide an ion-conductive solid electrolyte set/paraboloid having both excellent ion conductivity and mechanical properties.

[Means to solve the problem]

According to the present invention, there is provided an ion conductive solid electrolyte composition comprising a block copolymer containing polyalkylene glycol and polystyrene or a polystyrene derivative, and an inorganic ionic salt.

Furthermore, there is provided an ion conductive solid electrolyte composition in which the above ion conductive solid electrolyte composition further contains a polyalkylene glycol represented by the following general formula (1) or a derivative thereof.

R' 0-(CHICHRO), l-R"...
-(1) (However, R, R' and R# represent hydrogen or a lower alkyl group, and n represents an integer of 3 to 30.) Hereinafter, the composition of the present invention will be explained in detail.

The polyalkylene glycol constituting the copolymer containing polyalkylene glycol, which is the base polymer of the solid electrolyte composition of the present invention, and polystyrene or a polystyrene derivative block has the following general formula +(0-(-
CI (2-C1 (R-0-), -H, R is hydrogen or a lower alkyl group, a polymer of alkylene glycol such as ethylene glycol, propylene glycol, l, 3-butylene glycol, etc., with a degree of polymerization n is 5 to 100
0, preferably 10 to 750.

The polyalkylene glycol/polyvinyl chloride block copolymer of the present invention can generally be obtained by reacting polyalkylene glycol with a styrene monomer or styrene derivative, or by reacting polystyrene or polystyrene derivative R form with alkylene glycol. can. For example, a styrene derivative monomer is polymerized using azobiscyanobencuonic acid chloride as an initiator,
Furthermore, a method of polycondensing terminal-reactive acid chloride and polyethylene glycol, or alternatively, using an azo group-containing polyethylene glycol obtained by polycondensing polyethylene glycol and azobiscyanobenconic acid chloride as an initiator, styrene monomer or styrene A block copolymer containing polyethylene glycol and polystyrene or a polystyrene derivative can be obtained by radical polymerizing derivative monomers.

The styrene derivative monomer used here is 2 (here, R,, R,, R3 represents a substituent such as hydrogen, lower alkyl, halogen, alkoxy, etc.) Examples: Eva, methylstyrene, α-methylstyrene dichlorostyrene etc. can be given.

Examples of the polystyrene derivative include polymers of the above-mentioned styrene derivative monomers, copolymers of two or more of these, and the like.

In addition, the inorganic ionic salt constituting the solid electrolyte composition of the present invention is not particularly limited, but for example, [,1Cj2
04, Li5CN, LiBF4, LiAsF5, L
iCF+SOz, LiPF6, Nal, Na5CN
,,NaBr,,KI Cs5CN ,,AgN0*C
uCj! z, Mg(C120t) 2nd class Li,
Na, K, Cs, Ag.

It is preferable to use an inorganic ionic salt containing at least one of Cu and Mg as a metal ion.

Moreover, two or more types of inorganic ionic salts may be used in combination.

The inorganic ionic salt is preferably in the range of 0.05 to 50 mol%, more preferably 0 to the alkylene oxide unit (hereinafter simply referred to as EO) in the polyalkylene glycol of the block copolymer.
．． The content is preferably in the range of 1 to 30 mol%.

If the content of the inorganic ionic salt is too large, the excess inorganic ionic salt will not dissociate and will simply coexist, which will reduce ionic conductivity, which is not preferable. Moreover, if the content is too small, the number of dissociated ions will be small and the ionic conductivity will be reduced, so the content is preferably within the above range.

The ion conductive solid electrolyte composition of the present invention is formed by adding and mixing the above block copolymer as a pace polymer with an inorganic ionic salt.

In the present invention, it is possible to further add and contain polyalkylene glycol represented by the general formula (1) or a derivative thereof to the composition consisting of the block copolymer and inorganic ionic salt to enhance ionic conductivity. can.

Examples of the polyalkylene glycol represented by the general formula (I) and its derivatives include tetraethylene glycol, hexaethylene glycol, octaethylene glycol and their mono- or dimethyl ether derivatives,
Also included are compounds in which the above ethylene glycol structure is replaced with propylene glycol or a copolymer structure of ethylene oxide and propylene oxide. Two or more types of these poly0 alkylene glycols may be used in combination.

In this case, the molecular weight of the polyalkylene glycol and its derivatives is preferably about 100 to 2,000. If this molecular weight is too high, ionic conductivity will decrease. On the other hand, if this molecular weight is too low, it is undesirable because it becomes easy to vaporize and may gradually vaporize from the composition.

Further, the content of polyalkylene glycol and its derivatives in the composition is 5% relative to the block copolymer.
The content is preferably 00% by weight or less, more preferably 400% by weight or less.

If this content is too large, the mechanical strength of the composition decreases, which is not practically desirable.

The solid electrolyte composition of the present invention can be obtained by adding and mixing an inorganic ionic salt to the block copolymer, or an inorganic ionic salt and the polyalkylene glycol or its derivative. Addition and mixing can be performed using any known method and is not particularly limited. For example, the mixture may be uniformly mixed using a solvent such as tetrahydrofuran, 1 dimethylacetamide, dimethyl sulfoxide, acetonitrile, or the like, or may be uniformly kneaded by mechanical kneading at room temperature or under heating.

The solid electrolyte composition of the present invention obtained as described above may be used after being molded into a film, fiber, pipe, or tube, or these molded products may be further processed and used. For the molding process, any molding method such as a press method, an extrusion method, a casting method, etc. may be used.

〔Example〕

Examples of the present invention will be described in detail below. However, the present invention is not limited to this example.

Example 1 [Synthesis of polystyrene/polyethylene glycol block copolymer] Using azobiscyanopenconic acid chloride as a polymerization initiator, a predetermined amount of styrene monomer was added in a nitrogen-sealed tube for 60 min.
Polystyrene was polymerized at 0°C to obtain polystyrene having reactive acid esters at the ends.

This was mixed with polyethylene glycol and polycondensed by heating under reflux in a benzene solvent to obtain a polystyrene/polyethylene glycol block copolymer having a molecular weight of about 100,000.

[Production of ion-conductive solid electrolyte composition] 1 g of the block copolymer obtained by the above method and 0.05 g of lithium perchlorate (LiCβ04) as an inorganic ionic salt were dissolved in 10 mA of tetrahydrofuran. Thereafter, the solution was cast into an aluminum petri dish, the solvent was removed by evaporation, and the solution was dried to obtain a film-like composition.

The ionic conductivity (σ) of the obtained film was measured at room temperature using a complex impedance method. As a result, the obtained film-like composition exhibited an ionic conductivity of 2.9 x 10-'S/am.

In addition, in order to measure the mechanical strength characteristics of the obtained film, a test piece was punched out with a width of 0.4 G and a thickness of 0.04 mark, and the tensile strength of the test piece was measured using an autograph (manufactured by Shimadzu Corporation). D-5000). As a result, the tensile strength was 120 kg/-.

Example 2 Polyethylene glycol dimethyl ether (molecular weight 400, Asahi Denka ■) was added to the block copolymer obtained in Example 1.
A film-like composition was obtained in the same manner as in Example 1, except that 100% by weight of 0LE-400) was added to the block copolymer.

The ionic conductivity and tensile strength of the obtained film were measured in the same manner as in Example 1. As a result, the ionic conductivity was 9.3
X 10-5S/am, and the tensile strength was 64 kg/d.

Comparative Example 1 A film-like composition was obtained in exactly the same manner as in Example 1, except that polyethylene oxide having an average molecular weight of about 100,000 was used instead of the polyethylene glycol polystyrene block copolymer, and the ionic conductivity and tensile strength were also measured in the same manner.

As a result, the ionic conductivity σ is 9.5 x 10-”S/
(up to), and the tensile strength was 250 kg/ai.

4 Comparative Example 2 A film-like composition was obtained in exactly the same manner as in Example 2, except that polyethylene oxide having an average molecular weight of about 100,000 was used instead of the polyethylene glycol/polystyrene block copolymer, and ion conductive The strength and tensile strength were also measured in the same manner.

As a result, the ionic conductivity σ is 7.5
/ mark, and the tensile strength was 10 kg/cnT.

Comparative Example 3 In Example 2, when a composition was produced by adding 1000% by weight of polyethylene glycol dimethyl ether OLE-400, the resulting film was in a swollen state and had extremely low tensile strength.

As is clear from the above Examples and Comparative Examples, a composition comprising an inorganic ionic salt or an inorganic ionic salt and a polyalkylene glycol or a derivative thereof using the polyalkylene glycol/polystyrene block copolymer of the present invention as a pace polymer. It can be seen that this material has both excellent ionic conductivity and mechanical strength.

〔Effect of the invention〕

The ion conductive solid electrolyte composition of the present invention has higher ionic conductivity than conventional ones, and has excellent moldability and mechanical properties, and can be used in secondary batteries, secondary batteries, and fuel cells. It is suitable for use in electrochromic display elements, etc., has particularly high tensile strength, and is less prone to breakage even when made into a film, and is also excellent for application to ion conductive membranes in ultra-thin lithium batteries, making it extremely useful industrially. be.

Claims (2)

[Claims] (1) An ion conductive solid electrolyte composition comprising a block copolymer containing polyalkylene glycol and polystyrene or a polystyrene derivative, and an inorganic ionic salt. (2) A claim further containing a polyalkylene glycol represented by the following general formula (I) or a derivative thereof (
1) The ionically conductive solid electrolyte composition described above. R'O-(CH_2CHRO)_n-R″...( I
) (However, R, R' and R'' are hydrogen or a lower alkyl group, and n is an integer from 3 to 30.)