MBene promoted Zn peroxide chemistry in rechargeable near-neutral Zn-air batteries

Abstract

Highly reversible Zn-air batteries (ZABs) in near-neutral aqueous electrolytes can suppress the formation of Zn dendrites and carbonates. However, near-neutral ZABs (NNZABs) based on Zn peroxide (ZnO<inf>2</inf>) chemistry are challenging to build due to the air circulation requirement and the Swagelok structure. To achieve cost-effective NNZABs in a coin-cell configuration, it is essential to explore air-breathing cathodes with high catalytic activity for near-neutral systems. Previous studies focused on catalysts for alkaline ZABs, which are usually not suitable for near-neutral batteries. Here, Mo<inf>4/3</inf>B<inf>2−x</inf>T<inf>z</inf> MBene with ordered vacancies is for the first time exploited as a high-performance catalyst for NNZABs. Interestingly, a stable lifecycle for 380 h under a current density of 2 mA cm⁻² and a 5 h cycling period was achieved, which is attributed to the high O<inf>2</inf>-adsorbability and air stock capacity of Mo<inf>4/3</inf>B<inf>2−x</inf>T<inf>z</inf> MBene. We also demonstrate that the vacancies at the Y sites of Mo<inf>4/3</inf>B<inf>2−x</inf>T<inf>z</inf> MBene are active sites for boosting the sluggish kinetics of ZnO<inf>2</inf> chemistry. This work highlights the significance of introducing highly efficient cathode catalysts for NNZABs and the high efficiency of MBenes as catalysts in near-neutral systems.