PURPOSE: To improve reliability by leading sulfuric acid or sulfuric acid root as guest between electrolytes at the different positions in a cell while placing a coupling member associated with a host layer for forming inter-layer compound, thereby suppressing unbalance of concentration which causes deterioration of service life.
CONSTITUTION: Coupling member 7 made of host material for the inter-layer compound employing sulfuric acid or sulfuric acid root as guest is placed between the electrolytes in region I above the plate group and region II below the plate group of a cell. Sintered graphite where lead powder is sintered integrally under the temperature of 900∼1,000°C is employed for said coupling member 7. Said coupling member is not required to be filled entirely with host material, and when the host layer in the inter-layer compound is laminated in plural layers intermittently, the host layer will sequentially correct the concentration against the liquid layer formed between the host layers and the differential liquid concentration between both ends is corrected to suppress local unbalance of liquid concentration resulting in improvement of service life.
WATANABE KEIICHI
JINBO HIROYUKI
IWAKI TSUTOMU
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