Interfacial coordination reconstruction via electrochemical phase transformation for stable zinc powder anodes

The practical development of aqueous zinc-ion batteries is hampered by the intrinsic thermodynamic instability of zinc powder anodes, where uncontrolled parasitic reactions and dendritic growth lead to rapid capacity decay. Conventional interfacial protection layers, whether pre-fabricated or in-situ formed, suffer from mechanical and chemical degradation under dynamic cycling conditions. Here, we report an interface regulation strategy based on an electrochemically driven phase transformation of copper oxalate (CuC2O4) embedded in the zinc powder electrode. Upon discharge, the CuC2O4 undergoes a structural reconstruction involving the conversion of C=O to C-O coordination environments and the partial reduction of Cu2+ to Cu+, as evidenced by multi-modal spectroscopy and X-ray photoelectron spectroscopy. This reconstructed interface, enriched with C-O groups and Cu+ sites, exhibits enhanced zinc affinity and water confinement, as quantified by density functional theory calculations, thereby suppressing parasitic hydrogen evolution and guiding uniform zinc deposition. As a result, the modified zinc powder anode (ZP@CuC2O4) delivers a stable cycling lifetime of approximately 600 h under high-rate conditions (7 mA cm-2/1 mAh cm-2) in symmetric cells and enables pouch-type full cells to deliver a cumulative capacity of 11.7 Ah after 1,000 cycles at 7 A g-1. This work demonstrates a paradigm of dynamic interfacial engineering through intrinsic phase-transition-induced coordination reconstruction, addressing a key barrier for practical zinc powder anodes.