A durable rechargeable zinc-air battery via self-supported MnOx-S air electrode

Abstract

The durability and performance of an air electrode can have a crucial impact on rechargeable zinc-air batteries (ZABs). A typical air electrode fabricated using conductive carbon and a polymeric binder suffers rapid degradation during charging, stemming from oxygen bubbles erosion and carbon corrosion. This work presents a durable air electrode having a self-supported sulfur-doped manganese oxides (MnOx-S) electrocatalyst prepared through hydrothermal process followed by ambient temperature sulfurization. Upon sulfurization, MnO2 nanoflakes are transformed into MnOx-S having a heterostructure of Mn3O4, MnO2 and MnSx. MnOx-S provided superior electrochemical properties for both oxygen reduction reaction (Tafel slope of 68 mV/dec) and oxygen evolution reaction (Tafel slope of 80 mV/dec). Self-supported electrodes using MnOx-S and MnO2 electrocatalysts were scrutinized in a bi-electrode rechargeable ZAB having a stagnant electrolyte. In the ZAB using the self-supported MnOx-S electrode, both significant discharge peak power density (74 mW/cm2 at 135 mA/cm2) as well as low voltage difference between charge and discharge processes (0.75 V) were observed. In addition, for charge-discharge cycling at 20 mA/cm2, the ZAB using the self-supported MnOx-S electrode achieved stable cycling through 2000 cycles without apparent degradation. The air electrode having the self-supported MnOx-S paves the way for a more durable and higher performance favoring practical application for rechargeable ZABs.