Free-Standing Three-Dimensional CuCo 2 S 4 Nanosheet Array with High Catalytic Activity as an Efficient Oxygen Electrode for Lithium–Oxygen Batteries

In this work, a novel free-standing CuCo 2 S 4 nanosheet cathode (CuCo 2 S 4 @Ni) with high catalytic activity is fabricated for aprotic lithium–oxygen (Li–O 2 ) battery. This deliberately designed oxygen electrode is found to yield lower overpotential (0.82 V), improved specific capacity (9673 mA h g –1 at 100 mA g –1 ), and enhanced cycle life (164 cycles) as compared to the traditional carbonaceous electrode. The improved performance can be ascribed to the superb spinel structure of CuCo 2 S 4, in which both Cu and Co exhibit more abundant redox properties, improving oxygen reduction reaction and oxygen evolution reaction kinetics effectively and boosting the electrochemical reactions. Furthermore, the well-designed architecture also plays a critical role in the improved performance. Encouraged by the excellent catalytic activity of this free-standing cathode, large-scale pouch-type Li–O 2 cell based on CuCo 2 S 4 @Ni cathode is fabricated and can work under different bending and twisting conditions. This free-standing electrode provides a new strategy for developing Li–O 2 batteries with excellent performance and flexible wearable devices.