PURPOSE: To enhance the rate of utilization and prolong the cycle lifetime of charging/discharging by changing the active substance density (porosity) across the thickness of the electrode plate, and making in multi-layer construction.

CONSTITUTION: A double construction is incorporated by laying positive electrode active substance in layers in the thickness direction of the electrode plate from its center toward outside with a lower density (higher porosity) layer 2 situated in the central part of the electrode and with a higher density (lower porosity) layer 3 situated in the part contacting separator of the electrode plate surface. Accordingly, even repetitive charging and discharging does not cause the active substance to be turned into fine particles at the layer in the electrode plate surface part. Also the central part of the electrode plate has high porosity, which facilitates dispersion of the electrolyte and enriches existence of the electrolyte. This enhances the rate of utilization of the active substance and accomplishes a battery with large capacity and an excellent cycle lifetime of charging and discharging.