JPH01169803A - Ionic conductive solid electrolytic composition - Google Patents

Abstract

PURPOSE:To enable the composition in the caption to have excellent ionic conductivity by incorporating a specific segmentalized polyetherurethaneurea and inorganic ionic salt into the composition as components. CONSTITUTION:The composition in the caption has as its components segmentalized polyetherurethaneurea including 75-95wt.% of a polyethylene oxide structure presented by a formula: (CH2-CH2O)n, and inorganic ionic salt. If the component consisting of the polyethylene oxide structure is less than 75wt.%, the ionic conductivity of the composition becomes insufficient, while if it exceeds 95wt.%, the mechanical strength of the composition deteriorates. With respect to the inorganic ionic salt, it is preferable to include, as a metallic ion, one of Li, Na, K, Cs, Ag, Cu and Mg. As a result, the composition has high ionic conductivity, excellent moldability and superior mechanical property.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an ion-conducting solid electrolyte composition, specifically,
The present invention relates to an ion-conducting solid electrolyte composition using a composition comprising a segmented polyether urethane urea and an inorganic ionic salt, or a composition further containing a polyalkylene glycol. The solid electrolyte composition can be used as an electrolyte for secondary batteries, secondary batteries, electrochromic display elements, and the like.

[Conventional technologies and their problems] Primary batteries, secondary batteries, electrochromink (ECD)
Liquid electrolytes have conventionally been used for display elements and the like. However, liquid electrolytes have problems in long-term reliability because they tend to leak to the outside of the component and elute electrode materials.

In contrast, solid electrolytes do not have such problems;
This has the advantage that the structure of the parts of each device can be simplified, and further, by making the film thinner, the parts can be made lighter and smaller. These features are due to the development of small size and
Since it meets the requirements for various types of lightweight and highly reliable electronic components, its development research is being actively conducted.

As solid electrolyte materials, mainly inorganic substances such as β-alumina, silver oxide, rubidium, lithium iodide, etc. have been known so far. However, since inorganic materials are often difficult to mold into arbitrary shapes and form into films, and are generally expensive, there are many practical problems.

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, polymers such as polyethylene oxide, polypropylene oxide, polyethyleneimine, polyepichlorohydrin, polyethylene succinate, Li,
Solid electrolyte compositions made in combination with inorganic ionic salts such as Na and batteries using these compositions have already been proposed (for example, Japanese Patent Application Laid-open Nos. 55-984806, 5B-75779, and 58-108667). No. 5B
-188062, 5B-188063, 59-
No. 71263, No. 60-212461, No. 60-47
No. 372 and US Pat. No. 4,576,882) 6 However, these compositions have not been put into practical use at the present stage because they do not have sufficient ionic conductivity.

In order to solve this problem, a method has been proposed in which an organic solvent is added to a polymer solid electrolyte composition to improve ionic conductivity while maintaining an apparently solid state (for example, JP-A-Sho et al. 59-149601, 5B-7577
(Refer to each bulletin No. 9).

However, since the boiling point of the organic solvent used in this method is not very high, it may gradually vaporize from the composition during use, resulting in a decrease in ionic conductivity, or the organic solvent may ooze out from the composition. There were problems with long-term reliability.

In addition, a composite solid electrolyte has been reported in which polyethylene glycol with a molecular weight of 400 is added to a system of polymethacrylic acid and lithium perchlorate (Solid 5ta).
te Ionics Vol, 11.227 pages, 198
(see 3rd year). Furthermore, Japanese Patent Application Laid-Open No. 71263/1983 proposes a solid electrolyte made of a composite consisting of polymethacrylate, lithium salt, and polyethylene glycol (or polypropylene oxide). However, these solid electrolytes have insufficient ionic conductivity, although the problems of vaporization and oozing in compositions containing the above-mentioned organic solvents are small.

Furthermore, Japanese Patent Application Laid-Open No. 58-82477 proposes a solid electrolyte having a network structure of a composition consisting of (1) polyethylene oxide, (2) an alkali salt, and (2) a polymer capable of forming a network structure. However, in this solid electrolyte, the molecular weight of polyethylene oxide (2), which is preferably used, is high.
(5,000 to 70,000), tends to form a crystalline complex with the alkali salt of (2), resulting in insufficient ionic conductivity.

In addition to ionic conductivity, mechanical properties are also important as properties of solid polymer electrolytes. That is, focusing on the film-forming ability of polymers, applications are being promoted, for example, to ion-conducting diaphragms for ultra-thin lithium batteries. In this case, if the mechanical strength of the solid polymer electrolyte film is insufficient, it will break during handling during the lamination process with the negative electrode and positive electrode sheets during battery manufacturing, resulting in a short circuit between the negative and positive electrodes. This will cause a significant drop in battery performance.

Furthermore, as the lithium battery discharges, lithium metal in the negative electrode active material is eluted as lithium ions, reducing the volume of the negative electrode, and lithium ions are incorporated into the positive electrode active material, increasing the volume of the positive electrode. Ion-conducting diaphragms are required to have properties that can accommodate these deformations.

The conventionally known solid polymer electrolyte film is
These mechanical properties are not necessarily satisfactory.

In order to improve this problem, Macromolec (
ules.

Vol, 18. Pages 1945-1950, (19
85) reported a composition consisting of a segmented polyurethaneurea synthesized from 4,4'-methylenebis(phenyl isocyanate), ethylenediamine and polypropylene oxide, and LiClO4.

The above document states that this composition exhibits ionic conductivity while retaining the mechanical properties of a thermoplastic elastomer. However, the ionic conductivity of the composition here is not satisfactory at around room temperature, making it practically difficult to apply it to lithium batteries or electrochromic devices.

Therefore, an object of the present invention is to improve the drawbacks of conventional solid electrolytes and to provide an ion conductive solid electrolyte composition having excellent ion conductivity.

[Means for Solving the Problems] As a result of various studies, the present inventors have developed an ion which has segmented polyether urethane urea containing a polyethylene oxide structure in a specific range and an inorganic ionic salt as essential components. It has been found that the above object can be achieved by a conductive solid electrolyte composition.

The present invention has been made based on the above findings, and has the following general formula:
(CH2tCHtO), a segmented polyether urethane urea containing 75 to 95-1% of the polyethylene oxide structure represented by l-, and This is what we provide.

Hereinafter, the ion conductive solid electrolyte composition of the present invention will be explained in detail.

The compound of component (1) constituting the composition of the present invention can be synthesized by a method similar to that of the generally known segmented polyether urethane urea.

(For example, Macromolecules+ Vol.
16+, pages 775-786 (1983)) That is, a prepolymer having isocyanate groups at both ends of a polyethylene glycol chain is synthesized by reacting polyethylene glycol with a diisocyanate compound,
Furthermore, it can be synthesized by reacting this with a diamine compound.

Among the raw materials used in the above synthesis reaction, polyethylene glycol is represented by the following general formula %, where n is 5 to 2501, preferably 10 to
125 are used. In addition, as the diisocyanate compound, 2,4-tolylene diisocyanate, 4-tolylene diisocyanate,
．． 4'-diphenylmethane diisocyanate, cyanidine diisocyanate, tridene diisocyanate, hexamethylene diisocyanate, metaxylylene diisocyanate, etc. can be used. Further, as the diamine compound, ethylene diamine, propylene diamine, tetramethylene diamine, etc. can be used.

In the present invention, in the structure of component (1) above, the portion constituted by the polyethylene oxide structure is 75 to 9
It is necessary to be in the range of 5-1%, and this 75wt
If it is less than 9%, the ionic conductivity is insufficient.
If the content is 5 wt% or more, the mechanical strength decreases, which is not preferable.

In addition, polytetraethylene glycol or polypropylene glycol is used as a glycol raw material for segmented polyether urethane urea, but in this case, the ionic conductivity is low and undesirable. Therefore, when using the above synthesis method, polyethylene It is important to use glycol as a raw material.

There are no particular restrictions on the inorganic ionic salt which is the component (2) constituting the composition of the present invention, but preferred ones include, for example, LiCl0. , LiI, Li5CN, LiBF,
, LiAsFa, LiChSOs, LiPF6
, Nal S Na5CN ,, NaBr.

Kl, Cs5CN, ^gNo, , CuC1g,
, Mg(CIOn)z, etc., at least Li, Na
, K, Cs, Ag, Cu and inorganic ionic salts containing one of the group G as metal ions can be used.

The content of the inorganic ionic salt is preferably mol% (inorganic ionic salt/EOX100) of the inorganic ionic salt to the alkylene oxide unit (hereinafter abbreviated as EO) in the segmented polyether urethane urea and polyalkylene glycol. is in the range of 0.05 to 50 mol%, more preferably in the range of 0.1 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 be mixed together, resulting in a decrease in ionic conductivity.

Furthermore, if the content is too low, the number of dissociated ions will be small, resulting in a decrease in ionic conductivity.

Furthermore, two or more of the above inorganic ionic salts can be used in combination.

In addition, the composition of the present invention contains component (1) of the general formula (
n) or a derivative thereof (hereinafter abbreviated as polyalkylene glycol etc. as appropriate), etc., and the component (1) may include, for example, tetraethylene glycol, hexaethylene glycol, octa Examples include ethylene glycol, mono- or dimethyl ethers thereof, and compounds in which the ethylene glycol structure of the above compounds is replaced with a propylene glycol structure or a copolymer structure of ethylene oxide and propylene oxide.

Two or more of the above polyalkylene glycols and the like can be used in combination.

The above polyalkyls, lengelicols, etc. have a molecular weight of 100.
2000 is preferred. If the molecular weight is too high,
Ionic conductivity decreases and battery performance deteriorates. Furthermore, if the molecular weight is too low, the boiling point will be low, causing the problem of gradual vaporization from the composition.

The content of the polyalkylene glycol and the like is preferably 500% by weight or less, particularly preferably 400% by weight or less, based on the segmented polyether urethane urea. If the content of the above-mentioned polyalkylene gellicol or the like is too large, the mechanical properties of the cured product will deteriorate, which is not preferred in practice.

There are no particular restrictions on the method of adding and mixing the above-mentioned inorganic ionic salt or polyalkylene glycol, but for example, segmented polyether urethane urea and inorganic ionic salt or polyalkylene glycol are mixed with dimethylacetamide, dimethyl sulfoxide, etc. Examples include a method of uniformly mixing using a solvent, or a method of mechanically kneading an inorganic ion salt or polyalkylene glycol into segmented polyether urethane urea at room temperature or under heating.

The composition of the present invention can be formed into a film, fiber, pipe, or tube, or can be put into practical use as a further processed product. For the molding process at that time, methods such as press, extrusion, and casting methods can be used without particular limitations.

[Example] The present invention will be described in further detail below by giving examples of the present invention together with comparative examples.

Example 1 (Synthesis of segmented polyether urethane uj/a) Polyethylene glycol (molecular weight 3000, manufactured by Asahi Denka)
4g and 0.862g of 4.4'-methylenebis(phenylisocyanate) (manufactured by Wako Pure Chemical Industries, Ltd.), and 80
The reaction was allowed to take place at °C for 10 hours. reaction? Add 30% of dimethylacetamide as a carrier overnight to make a homogenized liquid. Cool the homogeneous liquid to -5°C, and add a dimethylacetamide solution of ethylenediamine (10wt%, ethylenediamine) to the liquid. Add 1.38g (containing 0.138g), -5
The mixture was stirred at °C for 1.5 hours for further reaction. After the reaction was completed, the reaction mixture was poured into a large excess of methanol to precipitate the polymer, which was then dried to obtain a segmented polyether urethane urea as a component of the present invention.

In the segmented polyether urethane urea, the polyethylene oxide structure is 80 wt% of the total structure.

(Creation of composition film) 1 g of segmented polyurethane urea obtained by the above method
and lithium perchlorate (LiC10m) as an inorganic ionic salt.
) 0.05 g was dissolved in 10 mfl of dimethyl sulfoxide, cast in an aluminum petri dish, and the solvent was distilled off and dried to obtain a film (invention product 1) comprising the ion conductive solid electrolyte composition of the invention. Obtained.

The ionic conductivity (σ) of this film was measured by a complex impedance method (measured by the same method in the following Examples and Comparative Examples) and found to be 1.8×10 −′S/cm.

In addition, in order to measure the a-mechanical properties of the film of Invention Product 1, a test piece with a thickness of 0.04 c+++ was prepared by punching out the film into a shape with a width of 0.4 ctn, and an autograph was applied to the test piece. (D-5000' manufactured by Kaiho Seisakusho)
The tensile strength was measured using The result is 2
50 kg/crrr".

Example 2 The composition of Example 1 was further added with polyethylene glycol dimethyl ether (mine (11CLE-40)) as a third component.
00, molecular weight 400) was added in an amount of 50 wt% to the segmented polyurethane urea to prepare a film (invention product 2) comprising the ion conductive solid electrolyte composition of the invention.

Regarding the product 2 of the present invention, the electrical properties and mechanical properties were measured in the same manner as in Example 1, and σ was 5. OX 10-'S 7cm, tensile strength is 23
0 kg/c.

Comparative Example 1 Polypropylene glycol (manufactured by Mineka, 3000 in molecule f!) was used in place of polyethylene glycol as a raw material for polymer synthesis in Example 1, and the rest was as in Example 1.
A film (comparative product 1) was prepared in the same manner as above. Regarding this comparative product 1, the electrical properties and mechanical properties were measured in the same manner as in Example 1, and σ was 1.3
10-'S 7cm, tensile strength is 220kg/c
It was "m".

Comparative Example 2 Same as Example 1, except that the composition ratio in the raw material of polyethylene glycol, which is the raw material for synthesis of the polymer in Example 1, was 65 wt%, and a segmented polyether urethane urea containing about 65 wt% of polyethylene oxide structure was prepared. A film (comparative product 2) was prepared. Regarding this comparative product 2, the electrical and mechanical properties were measured in the same manner as in Example 1, and σ was 4.0X.
1.0-1'S/cm, tensile strength is 280 kg
/cm”.

As mentioned above, it is clear that both Inventive Products 1 and 2 have excellent performance in both electrical and mechanical properties.

〔Effect of the invention〕

Since the solid electrolyte composition of the present invention has high ionic conductivity, excellent moldability, and mechanical properties, it can be used in secondary batteries, secondary batteries, fuel cells, electrocomic display elements, etc. Extremely useful as a solid electrolyte.

Patent applicant: Ube Industries, Ltd.

Claims (2)

[Claims] (1) [1] General formula: -(CH_2-CH_2O)_n-[I] The polyethylene oxide structure represented by 75 to 95w
An ion conductive solid electrolyte composition comprising segmented polyether urethane urea containing t% and [2] an inorganic ionic salt. (2) [3] General formula: R'O(CH_2CHRO)_n-R'' [II] (However, R, R', R'' are hydrogen or lower alkyl groups,
(n is an integer of 3 to 30) The ion conductive solid electrolyte composition according to claim 1, which contains a polyalkylene glycol or a derivative thereof.