Carbon-Free Reversible Air Electrodes based on Perovskite Oxide and Conductive Oxide for Rechargeable Zinc-Air Batteries

Abstract

Reversible air electrodes with high activity and durability during the discharge/charge processes are required for rechargeable zinc-air batteries. Although carbon materials are widely used as catalyst supports and conductive additives for metal oxide catalysts in the catalyst layer (CL) and as the main active constituent in the gas-diffusion layer (GDL), the carbon is oxidized during the charge step, causing degradation of the air electrode. In this study, carbon-free air electrodes were prepared using electro-conductive oxides, namely, indium tin oxide or antimony-doped tin oxide, as an alternative to carbon materials in both the CL and GDL to achieve reversibility and durability of the air electrode in zinc-air batteries. While the initial performance of the carbon-free air electrodes was inferior to that of the carbon-based air electrodes, the lifetime of the carbon-free air electrodes was remarkably longer. These results indicate a critical role of electro-conductive oxides in both the CL and GDL for durable air electrodes.