(777d) Improved Cycle Life Performance of MnO2 Cathode and Zn Anode for Secondary Rechargeable Alkaline Batteries

Primary alkaline manganese dioxide batteries have been widely used in a variety of consumer applications and devices. Alkaline manganese dioxide batteries use manganese dioxide (MnO₂) as cathode and zinc (Zn) as anode material. As both zinc and manganese dioxide are abundant in nature and inexpensive, this battery has much potential in the rechargeable battery market, and may be able to compete with lead-acid and nickel-cadmium cells due to its low cost.

The cycle life of alkaline manganese dioxide rechargeable batteries has been limited to 20-30 cycles due to irreversibility associated with MnO₂ upon deep discharge and formation of electrochemically inactive phases. Thus the commercialization of this battery has been limited.  Also, formation of a haeterolite (ZnO:Mn₂O₃) phase during discharge, when Zn penetrates into the lattice structure of MnO₂, has made battery cycling irreversible. The Zn anode also has limitations on cycle life due to the redistribution of Zn active material and formation of dendrites during recharge, causing short-circuits.

In order to design a predictable, inexpensive Zn-MnO₂ battery, we access a fraction of one electron capacity of the MnO₂ during each cycle. However, MnO₂ being inexpensive and abundant, low cost alkaline batteries based on MnO₂ cathodes can be developed by accessing only this fraction of the 1-eletron capacity of MnO₂. In the present work, we have demonstrated more than 1500 cycles of a MnO₂ cathode coupled with various anodes such as Zn and Cd with more than 80% energy efficiency. This demonstrates the possibility of making inexpensive secondary rechargeable batteries with long cycle life based on MnO₂. The problems associated with Zn anode has been taken care of with the help of strategy used in the present work.