PURPOSE: To make bromine permeability smaller as well as to improve the extent of coulombic efficiency by forming a separator with a polyolefine fine porous film containing polyolefine and silica, and specifying the ratio of a silicon atomic number to a carbon atomic number coming to the surface.
CONSTITUTION: A separator 12 separating a positive electrode side liquid chamber 10a from a negative electrode side liquid chamber 10b is formed with a polyolefine fine porous film containing polyolefine and silica, and the ratio Si/C of a silicon atomic number (Si) to a carbon atomic number (C) coming to the surface should be set to be more than 0.2. With this constitution, hydrophile property on the surface increases, and any sticking of a bromine complex onto the surface is prevented from occurring, so that bromine permeability in the separator 12 is made reducible, and thus a coulombic effect is improved.
Kawahara, Kazuo
Saeki, Toru
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