Hollow Raspberry-like CoSx/C Sub-Microspheres as a Highly Active Air Cathode Catalyst for Rechargeable Zinc-Air Batteries

Rechargeable zinc-air batteries (ZABs) are considered one of the most promising energy devices owing to their high theoretical capacity, environmental friendliness, low cost, and high safety. However, their practical applications are still limited by the lack of low cost, high activity, and stable air cathode catalysts toward both the oxygen reduction reaction (ORR) and the oxygen evolution reaction (OER). In this study, hollow, raspberry-like CoSx/C sub-microspheres were designed and fabricated. The synthesized catalyst exhibited high catalytic performance toward both the ORR and OER, requiring a half-wave potential of 0.87 V for the ORR and an ultralow overpotential of 160 mV to achieve 10 mA cm–2 for the OER. When used as an air cathode catalyst, it provided a ZAB with a maximum power density of 341.9 mW cm–2 and exhibited excellent cycling stability. After continuous and steady operation for 1000 cycles (corresponding to 333.3 h) at 5 mA cm–2, no obvious decay in performance was observed. The catalyst's high performance and stability will make it find its potential use in practical and commercial applications. Also, the present strategy can be easily translated to the rational designing and fabrication of bifunctional oxygen catalysts with both high activity and stability for ZABs and other eco-friendly and future-oriented energy techniques.