JPH0753785B2 - Polymer solid electrolyte - Google Patents

Description

TECHNICAL FIELD The present invention relates to a solid polymer electrolyte.

[Prior Art] Since it was reported that polyethylene oxide (PEO) and certain alkali metal salts form a crystalline complex and show high ionic conductivity, (“Fast Ion Transport in Sodium
lid ", P.Vanishista, et.al, Eds.P 131 (1979) North Hol
land Publishing.Co.,) PEO-alkaline metal salt composites have been the focus of research on solid polymer electrolytes.

Compared to inorganic solid electrolytes, polymer solid electrolytes have lower ionic conductivity at room temperature (10 ^-4 S / cm to 10 ^-5 S / cm), but are lightweight, flexible, have high energy density, and have good moldability. It has the advantage of being excellent. It is desirable to obtain a polymer solid electrolyte having a high ionic conductivity while maintaining the excellent moldability and flexibility. However, of the materials currently reported, for example, polyphosphazene, which has a high ionic conductivity of 10 ⁻⁴ S / cm at room temperature, has a poor film-forming property, has a problem in mechanical strength, and has excellent strength. Having, at room temperature 10 ^-5
The urethane cross-linked product of polyethylene oxide having S / cm [Solid State Ionics, 18 & 19 , 338 (1986)] is an insoluble and infusible film, so that it needs to be formed at the same time as the reaction, and there is a problem in moldability. As described above, at present, a polymer solid electrolyte having a high ionic conductivity at room temperature and excellent film forming properties and processability has not been obtained.

[Objective] In view of such a situation, the present invention has high ionic conductivity,
Moreover, it is an object of the present invention to provide a polymer solid electrolyte having excellent film forming properties and processability.

[Composition] The present invention relates to a novel polymer solid electrolyte having high ionic conductivity at room temperature and excellent in moldability and processability. Further, the invention is characterized by using a polymer matrix having a functional group in the molecule in which a crosslinked structure is newly generated by a reaction such as dimerization or addition by irradiation with light or an electron beam, energy rays such as γ: X-rays. It is a thing.

That is, the present invention provides a high polymer solid electrolyte comprising an electrolyte salt and a matrix, which has an ion-dissociative group in the main chain or side chain as the matrix and an energy ray-reactive group having an aromatic ring or a heterocycle. It is a polymer fixed electrolyte characterized by using a crosslinked polymer obtained by irradiating a molecule with the energy beam.

Hereinafter, the present invention will be described in more detail.

The polymer solid electrolyte, that is, the ion conductive polymer, is composed of at least an electrolyte salt that serves as a polymer carrier that serves as a matrix. Then, the electrolyte salt dissociated into the polymer matrix forms an association with the polymer and is solvated, and when an electric field is applied, the ions are diffused and transported between the polymer chains while repeating association and dissociation, and conductivity is realized. It The ion conduction mechanism in the amorphous part of polymers is generally explained by the free volume model (J.Appl.Phys., 44 ,
5372 (1973)]. In other words, ionic conduction is caused by the transfer of ions to vacancies larger than the volume required for ion migration, and vacancies (free volume space) are caused by the polymer chains constantly changing their local arrangement due to thermal motion. . It is considered that the ions move through these vacancy by repeating the process of association with the polymer → transfer by thermal motion → dissociation. If ion movement occurs along with the movement of the polymer chain, in order to obtain a high ion conductive polymer,
As the matrix polymer, one having a high thermal motion of polymer chains at room temperature, that is, one having a low glass transition temperature (Tg) may be selected.

PEO, polyethyleneimine, etc., which are one of the typical polymer solid electrolytes, have a low Tg and have excellent ionic conductivity in the amorphous portion. However, in the vicinity of room temperature, a part of the ion dissociative group is crystallized, so that the ionic conductivity is rapidly lowered. In order to make up for such drawbacks, it is effective to crosslink some of the crystalline ion dissociative groups to form an amorphous state.

In addition to solving the above problems, the crosslinked structure also gives the film strength.

The cross-linked PEO reported so far is obtained by reacting a cross-linking agent of polyfunctional ion-dissociative polymer, such as diisocyanate and triisocyanate, and has excellent ionic conductivity at room temperature and excellent cross-linking structure. It is a polymer solid electrolyte having excellent mechanical strength and flexibility.
However, since the cross-linked product is insolubilized at the same time as the reaction proceeds, it is necessary to advance the cross-linking reaction at the same time as the film formation, but since the cross-linking reaction is performed at the melting point of PEO or higher, it is difficult to control the film thickness and the operability is poor. . In the present invention, the process of the crosslinking reaction is improved in order to improve the film forming processability, which is one of the drawbacks of the crosslinked product. That is, a system in which a crosslinking reaction proceeds after film formation using a photosensitive group as a crosslinking agent was examined. As a result, a polymer solid electrolyte having excellent ionic conductivity and film-forming / workability properties has been obtained.

Hereinafter, it will be described more specifically.

The matrix polymer that constitutes the solid polymer electrolyte is at least a part that promotes ionic dissociation (ion dissociative group).
And a photosensitive group. Examples of the ion dissociative group include -CO ₂ CH ₂ O-, -CH ₂ CH ₂ NH-, Is mentioned. Out of these, particularly excellent properties were obtained when ethylene oxide was used as the ion dissociative group.

Examples of the photosensitive group Etc. Out of these, excellent effects were obtained especially with the cinnamoyl group and its derivatives.

Examples of the method for introducing the photosensitive group into the ion dissociative polymer chain include esterification reaction, urethanization reaction, urea formation reaction, addition reaction from epoxy, etc., but are not particularly limited to these. However, the method of introducing from acid chloride and alcohol by esterification gave high reactivity and a high introduction rate.

The content of the photosensitive group is 60% or more, preferably 80% or more.

As an electrolyte salt serving as a ^{carrier, SCN -, Cl -, Br} -,
_{^{I -, BF 4 -, PF}} 6 -, AsF 6 -, ClO 4 -, B (C 6 H 5) 4 -, CF 3 SO 3
^- and an anion such ^{as, Li +, Na +, K} + such as an alkali metal cation or ^{_{(C 4 H 9) N +}} , an electrolyte salt consisting of _{(C 2 H 5) 4 N} + of the organic cation, such as cations Is mentioned.

In order to prepare a polymer solid electrolyte, that is, a composite of a polymer matrix and an electrolyte salt, a method in which a polymer matrix film after photocrosslinking is immersed and impregnated in a solution in which a crosslinked polymer in which an electrolyte salt is dissolved is insoluble; Examples include a method of forming a film from a solution in which a polymer and an electrolyte salt are dissolved by a casting method. The latter is more preferable in the present invention.

The polymer solid electrolyte film formation method is preferably performed by a procedure of casting a polymer by a melting method or a solution method and irradiating with light or energy rays. Here, the melting method is a method of directly coating the substrate at a melting point of the polymer or higher. The solution method is a method in which a polymer is dissolved in a suitable solvent, the solution is applied, and the solvent is dried and removed to obtain a film.

Since the solid polymer electrolyte before cross-linking has a high viscosity in a molten state, it is preferable to cast it from a solution in order to obtain a uniform film. Ethanol as casting solvent,
Alcohol such as propanol and butanol, ketone such as methyl ethyl ketone and methyl isobutyl ketone, ester such as isopropyl acetate and halogen such as dichloroethane are used. Uniform casting was realized by a method using an applicator or a spin coating method. The cast film was heated and dried below the melting point to remove the solvent.

The light source for photo-crosslinking reaction is visible light, ultraviolet light, X-ray, γ-ray,
An electron beam is used. The irradiation dose is required so that the crosslinking reaction is 60% or more, preferably 80% or more. As a photoreaction sensitizer, for example, in the case of a polymer having a cinnamoyl group as a photosensitive group, a triplet sensitizer is effective, and the photoreaction rate is more than doubled. As the sensitizer, those having absorption on the longer wavelength side than the absorption wavelength of the photosensitive group or in accordance with the maximum wavelength of the light source, such as 5-nitroacenaphthene and N-acetyl-4-nitro-1-naphthylamine, are It was effective.

Hereinafter, the present invention will be described in more detail with reference to examples.

Example 1 Polyethylene oxide triol (average molecular weight 3000) 10
g and pyridine 1.16 g were dissolved in benzene 300 cc, cinnamic acid chloride 1.96 g dissolved in benzene 20 cc 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%. Obtained. The obtained polymer was dissolved in methyl ethyl ketone to a concentration of 20 wt%, and 0.02 mol of ethylene oxide unit was added thereto.
LiClO ₄ and 5-nitroacenaphthene as a sensitizer were dissolved in 5 mol% with respect to the photosensitive group, and casting was performed using an applicator of 50 μm. 30 cast films
Dry for 20 minutes at ℃, 10mW / c using a high pressure mercury lamp
Irradiation was carried out at m ² for 10 minutes to obtain a crosslinked product having a gelation rate of 90%.

The ionic conductivity of the obtained solid polymer electrolyte was sandwiched between platinum plates and measured by the complex impedance method. As a result, a high value of 1.7 × 10 ^-4 S / cm was obtained at room temperature.

Example 2 P-nitrocinnamic acid was used in place of cinnamic acid chloride in Example 1, and the same synthesis was carried out. Upon light irradiation, crosslinking was performed without using a sensitizer. The ionic conductivity at room temperature is
It was 2.8 × 10 ^-4 S / cm.

[Effect] As is clear from the above description, the solid polymer electrolyte of the present invention has high ionic conductivity at room temperature, moldability, and
It has excellent workability and is useful for organic solid secondary batteries, electrochromic devices, all-solid-state capacitors, and the like.

Claims (1)

[Claims] 1. A polymer-immobilized electrolyte comprising an electrolyte salt and a matrix, wherein the matrix has an ion-dissociating group in the main chain or side chain and an energy ray-reactive group having an aromatic ring or a heterocycle. A polymer solid electrolyte comprising a crosslinked polymer obtained by irradiating a molecule with the energy beam.