Free-Standing Three-Dimensional CuCo₂S₄ Nanosheet Array with High Catalytic Activity as an Efficient Oxygen Electrode for Lithium-Oxygen Batteries

In this work, a novel free-standing CuCo₂S₄ nanosheet cathode (CuCo₂S₄@Ni) with high catalytic activity is fabricated for aprotic lithium-oxygen (Li-O₂) 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 CuCo₂S₄, 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-O₂ cell based on CuCo₂S₄@Ni cathode is fabricated and can work under different bending and twisting conditions. This free-standing electrode provides a new strategy for developing Li-O₂ batteries with excellent performance and flexible wearable devices.