MANGANESE-DIOXIDE RECHARGEABILITY IN AQUEOUS-MEDIA - THE COMBINATION OF OXYGEN-REGENERATION WITH ELECTROCHEMICAL REGENERATION

The common manganese dioxides IC2 and Tekkosha are rechargeable only f or 18 and 10 cycles, respectively, when the depth of discharge is simi lar to 0.5 e/Mn. This low cycle life is due to the production of Mn3O4 during cycling. When the oxygen evolution is combined with electroche mical oxidation, these samples become rechargeable for 60-70 cycles. T he increase in the cycle life is due to the oxidation of Mn3O4 to the initial MnO2 by oxidizing species generated near the Mn3O4 sites durin g oxygen evolution by overcharging. The overrecharging has a positive effect when the duration of the recharge stage does not exceed similar to 50% of that of the discharge stage. Beyond this value the cycle li fe decreases.