JPH0335761B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an organic solid electrolyte having high ionic conductivity. Conventionally, inorganic crystals and ceramics such as RbAg ₄ I ₅ or stabilized zirconia are well known as solid electrolytes having ionic conductivity. On the other hand, research on solid electrolytes using organic polymers has recently become active. For example, it has been reported that by blending LiClO ₄ , NaSCN, or KSCN into polypropylene oxide, it exhibits ionic conductivity of 10 ^-4 to 10 ^-9 S cm ^-1 (Watanabe, Ikeda,
Shinohara, Polymer Journal, 15 , 65 (1983). Watanabe,
Nagaoka, Kanba, Shinohara, Polymer Journal, 14 , 877
(1982). ). However, since polypropylene is poorly soluble or insoluble in water and its melting point (softening point) is below room temperature, it is difficult to make an electrolyte using polypropylene oxide as a polymer into a solid film or sheet. It is also used as a solution in the above literature. Polyacrylonitrile or polyvinylidene fluoride, which can be formed into a film, is also used as a solid electrolyte, but since these are insoluble in water, they need to be dissolved in an organic solvent such as methanol. Therefore, the metal salt that serves as the electrolyte must also be soluble in the organic solvent.
Metal salts that are insoluble in organic solvents cannot be used. On the other hand, a solid electrolyte using water-soluble polyethylene oxide has been reported by P. V. Wright (Br. Polymer Journal, 7 , 319).
(1975). ), polyethylene oxide needs to have a molecular weight of several million when it is made into a film or sheet, and the film surface remains sticky even after forming. P, V, and Wright use polyethylene oxide with a molecular weight of 4 million, pelletized, and used as an electrolyte. On the other hand, it has been reported that the conductivity generally decreases as polymers with higher molecular weights are used (Watanabe, Ikeda, Shinohara, Polymer
Journal, 15 , 175 (1983). ), Therefore, if a polyethylene oxide with a lower molecular weight, excellent film-forming ability, and no stickiness on the film surface could be found, it would be possible to improve the above-mentioned drawbacks. As a result of intensive research in view of the above circumstances, the present inventors succeeded in obtaining a high molecular weight compound that is water-soluble and has excellent film-forming ability or sheet-forming ability, and has developed an organic solid electrolyte with high ionic conductivity. This is what we have come to offer. That is, a polyoxyalkylene glycol with an average molecular weight of 5000 or more and an ethylene oxide unit content of 70% or more (wt%, the same applies hereinafter),
Average molecular weight prepared by reacting polyhydric carboxylic acid, its anhydride or its lower alkyl ester
This is an ionic conductive organic solid electrolyte characterized by a combination of a high molecular weight compound of 50,000 or more and one or more metal salts of the group and/or group. The organic solid electrolyte produced in this way is
Excellent film forming ability, especially elongation and tear strength,
Since there is no stickiness on the film surface and furthermore, the film forming ability is excellent, it becomes possible to increase the amount of metal salt to be distributed. In the present invention, a polymer compound having an average molecular weight of 50,000 or more is produced from the polyoxyalkylene glycol (hereinafter referred to as POAG) and a polyhydric carboxylic acid, its anhydride, or its lower alkyl ester. The POAG preferably has an average molecular weight of 5000 or more and an ethylene oxide unit content of 70% or more. When the molecular weight is less than 5000, the solvent solubility and film-forming ability of the polymer compound produced using it tend to be insufficient, and therefore, the ionic conductive organic solid electrolyte produced using the polymer compound tends to be insufficient. Film properties, especially physical strength, also tend to be insufficient. on the other hand,
When the ethylene oxide unit content of POAG is less than 70%, the condensation reaction when producing a high molecular weight compound by reacting POAG with a polycarboxylic acid, its anhydride, or its lower alkyl ester becomes slow, and the reaction time becomes slower. They tend to lengthen, become insoluble in water, and have a lower melting point, making it difficult to solidify at room temperature. The POAG can be obtained by addition polymerizing an alkylene oxide containing ethylene oxide to a compound having two active hydrogen atoms. Examples of the active hydrogen group include hydroxyl groups such as water and alcohol, amino acids, and phenolic hydroxyl groups. Specific examples of the compound having two active hydrogen groups (hereinafter referred to as starting material) include water, ethylene glycol, propylene glycol, dipropylene glycol, 1,4-butanediol, 1,6-hexanediol, Neopentyl glycol, bisphenol A, polyethylene glycol, polytetramethylene glycol, polypropylene glycol, methylamine,
Examples include ethylamine, aniline, butylamine, octylamine, laurylamine, and cyclohexylamine. As the alkylene oxide used in the addition polymerization, ethylene oxide is used as an essential component in an amount of about 70% or more, and in addition, prolepine oxide, butylene oxide, styrene oxide, etc. can be used in a total amount of about 30% or less. When the alkylene oxides are copolymerized, block copolymerization, random copolymerization, or a combination of these may be copolymerized. Preferably. Such addition polymerization is carried out by a conventional method, for example, using a caustic alkali such as sodium hydroxide or potassium hydroxide as a catalyst at a temperature of about 90 DEG to 200 DEG C. for about 2 to 30 hours. In the present invention, the polycarboxylic acids, their anhydrides, or their lower alkyl esters to be reacted with the POAG include, for example, (a) malonic acid, succinic acid, maleic acid, fumaric acid, adipic acid, sebacic acid, phthalic acid; , isophthalic acid, terephthalic acid, itaconic acid, trimellitic acid, pyromellitic acid or dimer acid; (b) monomethyl ester, dimethyl ester, monoethyl ester, diethyl ester of (a);
Monopropyl ester, dipropyl ester,
Examples include monobutyl esters, dibutyl esters, and (c) acid anhydrides of the acids listed in (a). By reacting the POAG with a polyhydric carboxylic acid, its anhydride or its lower alkyl ester,
A high molecular weight compound for use in the present invention is obtained. For example, the POAG and a polyvalent carboxylic acid, its anhydride, or its lower alkyl ester are mixed in equal amounts in terms of the functional group ratio for esterification or transesterification, and the conditions are 120 to 250°C and 10 ^-4 to 10 torr. The high molecular weight compound used in the present invention can be obtained by the reaction. The average molecular weight of the high molecular weight compound is preferably 50,000 or more. When the molecular weight is less than 50,000, the ionic conductive organic solid electrolyte of the present invention produced using the high molecular weight compound has low mechanical strength and becomes brittle. Next, the metal salts used in the present invention include group or group metal salts, and among them, Li, Na, and K metal salts having a small cation radius are preferred. These metal salts contain halogen ions as anions,
Compounds having a pair of thiocyanate ion and perchlorate ion are preferred. The reason why Li, Na, and K metals with small ionic radii are preferred as cations is largely due to the structure of the polyalkylene oxide, and the cations need to be trapped in the hexagonal structure surrounded by ether oxygen. . The proportion of the metal salt used in the above-mentioned high molecular weight compound is preferably 2% or more and 20% or less. If it is less than 2%, the ionic conductivity will be low, and if it is more than 20%, the film forming property or sheet forming ability will tend to be poor. Adding one or more compounds with a high dielectric constant that are effective in promoting dissociation of electrolytes, such as dimethylformamide, ethylene carbonate, propylene carbonate, or γ-butyrolactone, to the system will reduce ionization as long as film-forming properties are not lost. It is useful in increasing electrical conductivity. The ion-conductive organic solid electrolyte of the present invention utilizes high ionic conductivity to prevent static electricity on recording paper that requires low resistance, such as electrostatic recording paper and facsimile paper.
It is thought that it will be useful in many fields, such as solid-state battery diaphragms with little self-discharge, various sensors that utilize permeation ion selectivity, large-capacity capacitors, electrolytic application devices, and display devices. Next, the ionically conductive organic solid electrolyte of the present invention will be explained based on Examples. Production example 1 Diethylene glycol 106 in autoclave
and 20 parts of flaked caustic potash and heated to 130°C.
Ethylene oxide at less than 2Kg/cm ²・G under heating of
The reaction was carried out while gradually adding 12,000 parts. The weight average molecular weight of the product (intermediate) was determined by measuring the hydroxyl value and alkali value and was found to be approximately 10,000 parts. dimethyl terephthalate to 100 parts of the product obtained.
After adding 1.94 parts of the mixture and raising the temperature to 200°C, the mixture was reacted for 3 hours while removing methanol under a reduced pressure of 1 Torr to obtain a high molecular weight compound. The obtained high molecular weight compound has a weight average molecular weight (measured by high performance liquid chromatography) of approximately 200,000.
It was hot. Examples 1 to 5 18 parts of the high molecular weight compound obtained in Production Example 1 was dissolved in 62 parts of distilled water, and this aqueous solution was mixed with 10% by weight of LiClO ₄
The mixture was added to 20 parts of an aqueous solution and stirred for 2 hours at room temperature to obtain an aqueous solution with a LiClO ₄ content of 10.0% by weight based on the high molecular weight compound. Cast 5g of this in a Teflon shear with an outer diameter of 90mm, and leave it at 50℃ for a day and night.
A solid electrolyte film was prepared by drying under vacuum for a day and a night. After this film was left in a constant temperature and humidity room at 25° C. and 30% RH for 4 days, the conductivity was measured. For the measurement, a tungsten electrode and a four-terminal method Taikuun resistance measuring machine were used. Similarly, films having the LiClO ₄ concentrations shown in Table 1 were prepared and measured. These results are shown in Table 1.

[Table] Production Examples 2 to 5 The high molecular weight compounds shown in Table 2 were obtained in the same manner as Production Example 1.

[Table] Examples 6 to 9 The same procedure as in Example 1 was carried out using the high molecular weight compounds obtained in Production Examples 2 to 5. The results are shown in Table 3.

[Table] Examples 10 to 15 Using various metal salts instead of LiClO ₄ in Examples,
The rest was carried out in the same manner as in Example 1. The results are shown in Table 4.

【table】

Claims (1)

[Claims] 1 Polyoxyalkylene glycol with an average molecular weight of 5,000 or more and an ethylene oxide unit content of 70% by weight or more, and a polycarboxylic acid, its anhydride, or its lower alkyl ester prepared by reacting with an average molecular weight of 50,000 or more. An ionic conductive organic solid electrolyte characterized by combining a high molecular weight compound with one or more metal salts of the group and/or group.