High-performance alkaline hybrid zinc batteries with heterostructure nickel/cobalt sulfide

Despite their high energy density, great safety, and environmental friendliness, zinc-air batteries (ZABs) has insufficient energy efficiency and low discharge voltage for wide application. Constructing alkaline hybrid zinc battery (AHZB) by coupling ZABs with alkaline zinc-transition metal batteries can effectively address these issues. Herein, we report a nickel/cobalt sulfide heterostructure supported on nickel foam (Ni 3 S 4 @CoS x -NF), which exhibits excellent redox properties and high bifunctional oxygen catalytic activities. The aqueous AHZB with Ni 3 S 4 @CoS x -NF cathode demonstrates unprecedented energy efficiency (∼90%), high discharge voltage (1.70 V at 50 mA cm −2 ), and outstanding cycling stability. The evolution of valence states and phases of key materials observed through ex-situ characterizations suggests that Ni 4+ and Co 4+ contribute to the high redox activity. The solid-state AHZB with polyacrylamide-based gel electrolyte and Ni 3 S 4 @CoS x -NF cathode shows high power density over 100 mW cm −2 , preceding that of self-supported solid ZAB. Importantly, it can operate at temperatures between −40 and 80 °C. • A novel heterostructure of Ni 3 S 4 @CoS x -NF is developed by a facile method. • Ni 3 S 4 @CoS x -NF shows remarkable ORR/OER bifunctional catalytic properties. • AHZB with Ni 3 S 4 @CoS x -NF exhibits unprecedented energy efficiency (∼90%). • Flexible AHZB with PAM@A electrolyte can operate at −40 and 80 °C.