Surface engineering activation of mixed valence copper selenide: A high-performance anode for long life zinc-ion...

Rechargeable aqueous zinc-ion batteries (AZIBs) are an attractive alternative to lithium-ion batteries (LIBs) for large-scale energy storage, which offer high ionic conductivity and environmental advantages. However, challenges such as dendrite growth and limited coulombic efficiency (CE) limit electrochemical performance of AZIBs thus hindering their practical application. This study designs a polypyrrole (PPy)-coated copper selenide composite (Cu_xSe_y@PPy) that works via Zn²⁺ insertion/extraction mechanism. Density Functional Theory (DFT) calculations reveal the PPy layer modifies the surface charge distribution of Cu_xSe_y, introducing additional electrochemical active sites. Consequently, the novel composite anode achieving specific capacity of 308.2 mAh g^-1 at 100 mA g^-1 and capacity retain of 96 %after 10,000 cycles at 2000 mA g^-1, in half cell configuration. In full cell configuration, the rock-chair batteries with a ZnMn₂O₄ cathode retained 65.4 % capacity after 20,000 cycles, maintaining a CE consistently above 99 %.