Self-supported metal sulfide electrode for flexible quasi-solid-state zinc-air batteries

Abstract

Adopting self-supported electrodes with oxygen catalysts directly growing on the electrode support affords an available solution to improve the performance of zinc-air batteries (ZABs). Herein, we firstly fabricate a self-supported air electrode with manganese (Mn) doping nickel sulfide growing on the nickel foam (Mn–Ni3S2/NF) for ZABs via a facile approach. The optimized Mn–Ni3S2/NF electrode (S6M8) demonstrates an overpotential of 347 mV at 100 mA cm−2 toward oxygen evolution reaction (OER), being lowest among those of the most of reported metal sulfides. Also, S6M8 shows an improved catalytic activity toward oxygen reduction reaction (ORR) with the half-wave potential (E1/2) of 0.63 V, compared with the pristine sample (0.61 V). The self-supported electrode of S6M8 can directly serve as the air cathode of the flexible quasi-solid-state ZAB after a facile hydrophobic treatment, which exhibits the high maximum power density (Pmax = 75.8 mW cm−2), excellent charge-discharge property with a narrow charge-discharge voltage gap (0.86 V at 60 mA cm−2) and superior stability after 100 cycles. Moreover, the flexible ZAB with the self-supported electrode of S6M8 shows a superior charge-discharge reversibility among most of ZABs with the self-supported electrode. Our work sheds a light on the development of the low-cost self-supported air electrode for ZABs.