(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.
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