Influence of air electrode electrocatalysts on performance of air-MH cells

Ni-MH battery system has been in limelight recently because of its inherent advantages like high-energy density, eco-friendly nature, devoid of memory effect, etc. Replacement of the heavy nickel oxide electrode with lighter air electrode is expected to improve its energy density further by 20% and also to bring down the cost. Hence some studies have appeared in literature on the development of air-MH system. But the main problem is to have an adequate bifunctional electrode with suitable electrocatalyst. Several materials are available for use in air electrodes. A detailed study is required to identify the best catalytic material and optimize the battery activity. Hence, air-MH cells using different oxides like Ag2OAg2O, LaMnO3LaMnO3 and La0.65Sr0.30MnO3La0.65Sr0.30MnO3 as catalysts for air electrode have been investigated in the present study with MmNi3.5Co0.8Mn0.4Al0.3MmNi3.5Co0.8Mn0.4Al0.3 metal hydride negative electrode. Life cycling along with charge and discharge characteristics was studied in detail. The air-MH cells assembled with Ag2OAg2O and LaMnO3LaMnO3 as catalysts in the air electrode gave encouraging performance. LaMnO3LaMnO3 when incorporated as electrocatalyst delivered stable cycle life whereas incorporation of Sr resulted in inferior performance in the studied composition range.