PURPOSE: To improve liquid leakage-proofness by mixing the liquid leakage inhibitor which reacts with electrolyte and produces hydrate or hydroxide in a sealing member.

CONSTITUTION: For example, in Portland cement which reacts with electrolyte and solidifies this and zinc oxide, 40 parts by weight of wax are blended with 60 parts by weight of these chemical materials mentioned above, heated in some 120°C, mixed, and are impregnated in the paper with the brim 7 which has a thickness of 0.3mm and on air transmission of 0. 200 parts by weight of Portland cement are blended with 100 parts by weight of low density polyethylene. By mixing these, the polyethylene sealing body 13 is molded. This sealing body 13 is overlapped on the lower side of the sealing body 3 which faces the air chamber 5 and is heat- clamped. Thus the sealing body with double structure is obtained. This enables solidification of the electrolyte which transmits the sealing member and is leaked and improvement on liquid leakage-proofness.