Storage characteristics of mercury-free alkaline manganese batteries

The amount and distribution of additive species in zinc alloy particles con taining 0.025 wt % bismuth modified with 0.10 wt % indium for mercury-free alkaline manganese batteries were examined after storage at various dischar ging levels at 60 degrees C. The amount of hydrogen gas evolution due to th e self-discharging reactions of zinc and the internal cell impedance were a lso evaluated. The amount of additive species in the zinc alloy particles w as found to increase with increasing depth of discharge. Indium was homogen eously distributed on the surface even after partial discharge and also aft er storage for 1200 h at 60 degrees C. This behaviour is considered to cont ribute to the suppression of hydrogen gas evolution and increase in the int ernal cell impedance to the same level as when mercury is employed. As a re sult, mercury-free alkaline manganese batteries showed the same storage cha racteristics as conventional batteries containing mercury.