Uncovering the Cu-driven electrochemical mechanism of transition metal chalcogenides based electrodes

Transition-metal chalcogenides (TMCs) have emerged as attractive anode materials for rechargeable batteries due to their excellent performance and abundant resources. Here, for the first time, we disclose a unique copper (Cu)-driven conversion process in TMC-based battery systems that involves classic Cu current collector and is considered to be an “activation process”. According to state-of-the-art characterization techniques, Cu was evidenced to gradually replace the transition-metal elements in TMCs to be the active material during cycling. Based on this unique Cu-driven conversion mechanism, we used a facile method to design a new type of sulfur-based battery that presents excellent performance: a reversible capacity of 1.045 mAh cm⁻² after 700 cycles at 2 A g⁻¹, and a good rate capability up to a capacity of 0.33 mAh cm⁻² at 20 A g⁻¹. With respect to the large family of TMC compounds, this study introduces a new direction for the design of high-performance energy storage systems.