Development of MnO2 Based Cathodes for Alkaline Batteries via Combinatorial Approach

A combinatorial study is carried out to develop new cathode compositions in alkaline Zn-MnO2 secondary batteries. MnO2 is modified with ternary additions using Bi2O3, Na0.7MnO2, and NiO. A library of thick film cathodes over a wide compositional range is synthesized via sputter deposition. Thick film cathodes are investigated both electrochemically and structurally. Structural studies show that thick film cathodes are largely amorphous in the as-deposited state but upon charge-discharge cycling, are crystallized into delta-MnO2, i.e. layered polymorph of MnO2. The thick film cathodes are evaluated with cyclic voltammetry and charge-discharge cycling. Two compositional regions are noted as significant in terms of useful cathodes for rechargeable batteries. Compositions rich in NiO yield quite a reliable cell performance which might be considered as cathode material for Zn-NiO batteries. More importantly, there was also a region where Mn and Na had similar proportions doped by Bi and Ni, e.g. Bi0.08Na0.39Ni0.09Mn0.44Ox, which might be made the basis for improved cathode for Zn-MnO2 batteries.