PURPOSE: To prevent deterioration of the battery performance by providing a water absorbing compound whose absorbing capacity depends on the pH in contact with an electrolyte layer to control the release of water in the electrolyte out of the battery in an overdischarge state at a high temperature.
CONSTITUTION: In a container 1 made of a material permeable to steam such as ABS resin an assembled element which comprises negative electrodes 2, positive plates 4, and separators 3 is inserted, and colloidal sulfuric acid eletrolyte 5 is poured. A layer 6 of a water absorbing compound whose water absorption property is high around pH7 of the electrolyte but it is little near pH1 is provided on the electrolyte 5. Starch graft polymerized with acrylic acid monomer or methacrylic acid monomer or the like may be used as said water absorbing compound.
FUKUDA SADAO
TAKAHASHI KATSUHIRO
| JP46026179U |