Solid electrolyte

Details Solid electrolyte Solid electrolyte

1986-08-25

1987-10-13

Skapars, Anthony

Chemistry: electrical current producing apparatus, product, and

With pressure equalizing means for liquid immersion operation

429191, H01M 810

Patent

active

046998519

DESCRIPTION:

BRIEF SUMMARY
TECHNICAL FIELD

The present invention relates to a hydrogen ion (generally its hydrate)-conductive solid electrolyte. Particularly, it relates to a solid electrolyte which is suitably used in electrochemical equipment such as hydrogen-oxygen fuel cell, hydrogen sensor or pH sensor.


BACKGROUND ART

It has been reported by, for example, O. Nakamura et al. in Materials Research Bulletin 17, 231 (1982) that a heteropoly-acid (solid) such as dodecatungstophosphate (H.sub.3 PW.sub.12 O.sub.40.nH.sub.2 O) is a proton-conductive solid electrolyte. However, no heteropolyacids containing carbon as a heteroatom have been known as yet.


DISCLOSURE OF INVENTION

An object of the present invention is to provide a novel solid electrolyte which is suitably used in fuel cells, various sensors, electrochromic display elements or the like.
It has been found that the heteropolyacid containing carbon as a heteroatom to be used in the present invention exhibits a remarkable proton conductivity, that is, it is a proton-conductive solid electrolyte. The heteropolyacid has advantages in that its preparation is simple and that it can be molded more easily than other heteropolyacids. Further, the heteropolyacid is still advantageous in that a firm thin film can be produced from an aqueous solution thereof.
A heteropolyacid solid electrolyte is a solid comprising a heteropolyanion represented by the general formula, M'.sub.x M.sub.y O.sub.z.sup.m-, and a hydrated proton represented by the general formula, H(m' H.sub.2 O).sup.+, wherein proton is conducted. M is generally tungsten(W) or molybdenum(Mo) and P,Si,As and the like are known as the heteroatom M'. The solid electrolyte according to the present invention is represented by the above formula wherein M' is carbon (C) and is a novel electrolyte which has not been known up to this time. Further, though the heteropolyacids of the prior art have been prepared by liquid phase reaction between polytungstic acid (or polymolybdic acid) and an acid containing a heteroatom (for example, dodeca acid), the solid electrolyte of the present invention is prepared by the reaction between tungsten carbide and a solution of hydrogen peroxide.
The heteropolyacid of the present invention is a solid heteropolyacid containing carbon as a heteroatom
which comprises a heteropolyanion represented by the general formula, M'.sub.x M.sub.y O.sub.z m.sup.- (wherein the ratio of x to y is between 1:12 and 4:12) and a hydrated proton represented by the formula, H(m' H.sub.2 O).sup.+. In the above general formula, M' is C and M is at least one element selected from the group consisting of W and Mo. Further, the above formula can be also represented by the formula: WO.sub.3.aCO.sub.2.bH.sub.2 O.sub.2 cH.sub.2 O (wherein 0.083.ltoreq.a.ltoreq.0.25, 0.05.ltoreq.b.ltoreq.1 and 0.16.ltoreq.c.ltoreq.4).


BRIEF DESCRIPTION OF DRAWING

FIG. 1 shows a cross-sectional view of a cell produced by using a solid electrolyte of the present invention.


BEST MODE FOR CARRYING OUT THE INVENTION

Examples of the present invention will now be described.


EXAMPLE 1

100 ml of a 15% aqueous solution of hydrogen peroxide (H.sub.2 O.sub.2) was added to 16 g of tungsten carbide (WC) powder. When gas evolution was reduced, an additional 5 ml of 3% H.sub.2 O.sub.2 was further added. This procedure was repeated 5 times. The resulting mixture was allowed to stand at a room temperature for 24 hours or over to dissolve the WC, thus obtaining a pale yellow strongly acid solution. This solution was filtered to remove sooty carbon. The excess H.sub.2 O.sub.2 contained in the solution was removed by decomposition with a platinum gauze having adherent platinum black. The obtained solid electrolyte stock solution was placed in a flat-bottomed glass vessel, heated until just before its solidification and allowed to stand at a room temperature. By allowing to stand for 24 hours or over, a glassy plate was obtained. This solid did not exhibit any X-ray diffraction pattern, that is, it was amorphous. Further, the solid had a molar ratio of C t

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