An Energetic CuS–Cu Battery System Based on CuS Nanosheet Arrays

The development of low-cost and high-energy aqueous battery technologies is of significance for renewable and stationary energy applications. However, this development has been bottlenecked by poor conductivity, low capacity, and limited cycling stability of existing electrode materials. In this work, we report on an energetic aqueous copper ion system based on CuS nanosheet arrays, taking profit of high conductivity of CuS and efficient charge carrier of copper ions. Electrochemical results reveal a high capacity of 510 mAh g^–1, robust rate capability of 497 mAh g^–1 at a high rate of 7.5 A g^–1, and ultrastable cycling by retaining 91% of the initial capacity over 2500 cycles. The charge-storage mechanism was systematically investigated by ex situ and in situ techniques involving a reversible transition from CuS to Cu₇S₄ and to Cu₂S through the redox of Cu²⁺/Cu⁺. Moreover, we demonstrate a hybrid ion battery consisting of CuS positive electrode and Zn negative electrode, which affords an energy and power of 286 Wh kg^–1 and 900 W kg^–1, respectively, on the basis of both electrodes, exceeding many aqueous battery systems.