JPH0195117A - Solid polyelectrolyte - Google Patents

Abstract

PURPOSE:To provide the title polyelectrolyte having high ion conductivity at room temp. and excellent moldability, by crosslinking a polymer having ionizable groups and groups reactive with an energy ray by irradiating with an energy ray and using it as a matrix. CONSTITUTION:A crosslinked polymer is prepd. by irradiating a polymer having ionizable groups and groups reactive with an energy ray is its main chain or side chains (e.g., cinnamoylated polyethylene oxide, or polyethylene oxide acrylate) with an energy ray (e.g., electron beam). A solid polyelectrolyte is constituted of the crosslinked polymer thus obtd. as a matrix and an electrolyte salt (e.g., LiClO4) as a carrier. The solid polyelectrolyte thus obtd. is useful for an org. solid secondary battery, an electrochromic element, a wholly solid capacitor, etc.

Description

[Detailed description of the invention] [Technical field] The present invention relates to solid polymer electrolytes.

[Prior Art] Since it was reported that polyethylene oxide (PEO) and certain alkali metal salts form a crystalline complex and exhibit high ionic conductivity ("Fast Ion T
``Transport in 5old'', P.

Vanishlsta, et, al, Eds, P 13
1 (1979) Northlolland Pub
lishlng, Co1. ) Polymer solid electrolytes have been actively researched, centering on P E O-alkali metal salt complexes.

Compared to inorganic solid electrolytes, polymer solid electrolytes are lightweight, flexible, have high energy density, and have excellent moldability. It is desirable to obtain a solid polymer electrolyte having high ionic conductivity while maintaining this excellent moldability and flexibility. However, among the currently reported materials, for example, polyphosphazene, which has a bright ionic conductivity of 10' S/affl at room temperature, has poor film forming properties.
C3old 5tate Ion is a urethane crosslinked product of polyethylene oxide that has problems with mechanical strength and also has excellent strength and has 10°5S/c111 at room temperature.
lcs.

1B & 19,338 (198B)] forms an insoluble and infusible film, so it is necessary to form a film at the same time as the reaction, and there is a problem in moldability. As described above, at present, a solid polymer electrolyte that has high ionic conductivity at room temperature and has excellent film formability and processability has not been obtained.

[Purpose] In view of this situation, the present invention has high ionic conductivity,
Another object of the present invention is to provide a solid polymer electrolyte that has excellent film-forming properties and processability.

[Structure] The present invention relates to a novel solid polymer electrolyte that has high ionic conductivity at room temperature and is excellent in moldability and processability. It is also characterized by the use of a polymer matrix that has a functional group in its molecules that generates a new crosslinked structure through reactions such as trimerization and addition when irradiated with energy rays such as light, electron beams, and γ:X rays. It is something.

That is, the present invention has an ion dissociative group in the main chain or side chain, and an energy ray-reactive group (hereinafter simply referred to as a photosensitive group).
This is a solid polymer electrolyte characterized by having a matrix of polymers having the following properties.

The present invention will be explained in more detail below.

A solid polymer electrolyte, ie, an ion-conducting polymer, is composed of at least a polymer serving as a matrix and an electrolyte salt serving as a carrier.

The electrolyte salt dissociated into the polymer matrix forms an association with the polymer and becomes solvated, and when an electric field is applied,
Ions are diffusely transported between polymer chains while repeatedly associating and dissociating, thereby achieving electrical conductivity. The ion conduction mechanism in amorphous parts of polymers is generally explained using a free volume model (J, Appl, Phys, 44.537
2 (1973) Ko. That is, ion conduction is caused by the movement of vacancy ions in a volume greater than that required for ion movement, and vacancies (free volume spaces) are produced by polymer chains constantly changing their local arrangement due to thermal motion. Through such vacancies, ions can associate with polymers.
It is thought that it moves by repeating the process of movement and dissociation due to thermal motion. Assuming that ion migration occurs with the movement of polymer chains, in order to obtain a highly ionically conductive polymer, the matrix polymer must be one in which the thermal movement of the polymer chains is intense at room temperature, that is, a material with a glass transition temperature (Tg). Just choose the lower one.

PEO, polyethyleneimine, and the like, which are typical solid polymer electrolytes, have a low Tg and have excellent ionic conductivity in their amorphous portions. However, near room temperature, some of the ionically dissociated groups crystallize, resulting in a rapid decrease in ionic conductivity. In order to compensate for such drawbacks, it is effective to crosslink some of the crystalline ion dissociative groups to make them amorphous.

Furthermore, creating a crosslinked structure not only solves the above problems but also provides strength to the membrane.

The PEO crosslinked products reported to date include a polyfunctional ionically dissociable polymer and a crosslinking agent, such as diisocyanate,
It is obtained by reacting triisocyanate, etc., and is a solid polymer electrolyte that has high ionic conductivity at room temperature and excellent mechanical strength and flexibility due to its crosslinked structure.

However, since the above-mentioned crosslinked product becomes insolubilized as the reaction progresses, it is necessary to proceed with the crosslinking reaction at the same time as film formation, but since the crosslinking reaction is carried out above the melting point of PEO, it is difficult to control the film thickness and the operability is poor. . In the present invention, the crosslinking reaction process has been improved in order to improve film forming processability, which is one of the drawbacks of crosslinked products. That is, we investigated a system in which a photosensitive group is used as a crosslinking agent and the crosslinking reaction proceeds after film formation.

As a result, a solid polymer electrolyte with excellent ionic conductivity and film formation/processability properties was obtained.

This will be explained in more detail below.

The matrix polymer constituting the solid polymer electrolyte consists of at least a portion that promotes ion dissociation (ion dissociation group) and a photosensitive group. Examples of the ionically dissociable group include l -CH2CH2NH-1-C-O-1. Among these, particularly excellent properties were obtained when ethylene oxide was used as the ion dissociative group.

Examples of the photosensitive group include (R:NO2, CI, OCH3). Among these, particularly excellent effects were obtained with the cinnamoyl group and its derivatives.

Methods for introducing photosensitive groups into ionically dissociable polymer chains include, for example, esterification reactions, urethanization reactions, ureaization reactions, addition reactions from epoxy, etc., but are not particularly limited to these. However, the method of introducing esterification from acid chloride and alcohol had high reactivity and a high introduction rate.

The content of photosensitive groups is preferably 60% or more, preferably 8026 or more.

Electrolyte salts that serve as carriers include SCN'''', CI'
'', Br-1I-1BF4, PF5-1AsFs-
1C104-1B (C6H5)4-1CF3SO3'
Anions such as ``, and alkali metal cations such as Lt'', Na '', K+, (C4H9)4N'',
5) Examples include electrolyte salts consisting of cations such as organic cations such as 4N+.

In order to produce a polymer solid electrolyte, that is, a composite of a polymer matrix and an electrolyte salt, a method of immersing a photo-crosslinked polymer matrix film in a solution in which the electrolyte salt is dissolved and the crosslinked polymer is insoluble; Examples include a method of forming a film using a casting method from a solution containing a polymer and an electrolyte salt. In the present invention, the latter is preferable.

The method for forming a polymer solid electrolyte film is preferably carried out by the following steps: (1) casting a polymer by a melting method or solution method, and (2) irradiating it with light or energy rays. Here, the melting method is a method in which the polymer is directly applied to the substrate at a temperature higher than the melting point of the polymer. The solution method is a method in which a polymer is dissolved in an appropriate solvent, applied from the solution, and the solvent is removed by drying to obtain a film. Good results were obtained with both methods.

Since the polymer solid electrolyte before crosslinking has high viscosity in a molten state, it is preferable to cast it from a solution in order to obtain a uniform film. Examples of casting solvents used include alcohols such as ethanol, propatool and butanol, ketones such as methyl ethyl ketone and methyl isobutyl ketone, esters such as isopropyl acetate, and halogens such as dichloroethane. Uniform casting was achieved by using an applicator or by spin coating. The cast film was dried by heating below its melting point to remove the solvent.

The light sources that carry out the photocrosslinking reaction are visible light, ultraviolet light, X-rays, γ-rays,
An electron beam is used. The irradiation amount is 60% or more for the crosslinking reaction,
Preferably 80% or more of the total need occurs. As a photoreaction sensitizer, for example, in the case of a polymer having a cinnamoyl group as a photosensitive group, a triplet sensitizer was effective, and the photoreaction rate was more than doubled. As a sensitizer, one having absorption at a longer wavelength than the absorption wavelength of the photosensitive group or matching the maximum wavelength of the light source, such as 5-nitroacenaphthene, N
-Acetyl-4-nitro-1-naphthylamine and the like were effective.

The present invention will be explained in more detail with reference to Examples below.

Example 1 Polyethylene oxide triol (average molecular weight 3000
) IOg and pyridine 1.16g to benzene 300
1.96 g of cinnamic acid chloride dissolved in CC and 20 cc of benzene was added dropwise at room temperature under an inert gas atmosphere, and the reaction was continued for 6 hours to obtain cinnamoylated PEO with a substitution rate of 85%. The obtained polymer was dissolved in methyl ethyl ketone to a concentration of 20 vt%, and 0.02 mol of LiClO per ethylene oxide unit was added thereto.
4 and 5-nitroacenaphthene, which is a sensitizer, were dissolved at 5 mol % relative to the photosensitive group, and cast using a 50 μι applicator. The cast film is 30
Dry at ℃ for 20 minutes, then use a high pressure mercury lamp.
Irradiated with light for 10 minutes, gelation rate 90%
A crosslinked product was obtained.

The ionic conductivity of the obtained solid polymer electrolyte was measured by the complex impedance method by sandwiching the sample between platinum plates, and a high value of 1.7×10→S/cm was obtained at room temperature.

Example 2 In Example 1, acrylic acid chloride was used instead of cinnamoyl chloride, and the reaction was carried out in the same manner as in Example 1 to obtain an acrylic ester of PEO (esterification rate: 90%). The obtained polymer was dissolved in dichloroethane to a concentration of 20 vt%, and 0% per ethylene oxide unit was dissolved therein.
．． 02 mol of LiCl0+ and sensitizer CuEt3N
was dissolved in a catalytic amount and cast using a 50 μm applicator. The obtained film was dried at room temperature for 20 minutes and photocrosslinked in the same manner as in Example 1. The ionic conductivity at room temperature was 3.2 x 10 = 370 m.

Example 3 Synthesis was carried out in the same manner as in Example 1 except that P-nitrocinnamic acid was used instead of cinnamic acid chloride.

Crosslinking was carried out without using a sensitizer during light irradiation.

Ionic conductivity at room temperature is 2.8X 10″Slam
Met.

[Effect] As is clear from the above explanation, the polymer solid electrolyte of the present invention has high ionic conductivity at room temperature, and has good moldability and
It has excellent processability and is useful for organic solid secondary batteries, electrochromic cables, all-solid capacitors, etc.

Claims (1)

[Claims] A polymer solid electrolyte characterized in that the matrix is a crosslinked polymer obtained by irradiating a polymer having an ion dissociative group in the main chain or side chain and an energy ray-reactive group with the energy ray. .