Electrochemical reduction engineering for composite Sb/Cu₂Sb anodes toward high-efficiency potassium storage

Developing high-capacity anode materials with long-term cycling stability is a key challenge in enhancing potassium-ion batteries (PIBs) performance. Antimony (Sb)-based materials represent promising anode candidates for high-energy PIBs. However, their application is constrained by severe volume expansion leading to rapid capacity decay. Herein, we report a controlled synthesis of a composite anode material (Sb/Cu₂Sb/NC) incorporating Sb, Cu₂Sb, and nitrogen-doped carbon (NC) via a molten salt electrolytic method. The electrochemically inactive Cu component serves as an effective buffering matrix, modulating the evolution of lattice stress during potassiation/depotassiation processes. The NC network not only improves the overall electronic conductivity but also promotes efficient ion diffusion through its porous structure. Accordingly, the as-prepared Sb/Cu₂Sb/NC delivers a high capacity of 348.6 mAh g^-1 after 100 cycles at 0.1 A g^-1 and maintains 192.9 mAh g^-1 after 1000 cycles at 1.0 A g^-1. The assembled Sb/Cu₂Sb/NC//PTCDA full cell exhibited a capacity of 134.3 mAh g^-1 after 300 cycles at 0.1 A g^-1. This study not only provides a novel composite anode material for high-performance PIBs but also establishes a scalable and versatile approach for engineering next-generation alloy/carbon composite anodes through molten salt electrochemical reduction.