Polyoxometalate-derived redox interphases suppress hydrogen evolution for highly reversible zinc-ion batteries

The practical deployment of aqueous zinc-ion batteries (AZIBs) is severely constrained by the intrinsic instability of the Zn anode, which primarily originates from detrimental dendrite growth and the parasitic hydrogen evolution reaction (HER). Here, we present a redox-mediated interfacial engineering strategy employing a polyoxovanadate ([(CH₃)₂NC₅H₄NH₄(NH₄)₂[V₁₀O₂₈]·8H₂O, DMAP-V₁₀) as a multifunctional electrolyte additive. Upon cycling, DMAP-V₁₀ spontaneously in-situ forms a dense and uniform protective interphase on the Zn surface. This redox-derived interphase markedly suppresses the HER, shifting its onset potential by 0.38 V, while simultaneously homogenizing Zn²⁺ flux to enable dendrite-free Zn deposition with a preferred (002) crystallographic orientation. As a result, Zn||Zn symmetric cells demonstrate exceptional cycling stability exceeding 2100 h at 1 mA cm^-2, and Zn||Cu half-cells deliver a high average Coulombic efficiency of 99.74% over 2500 cycles. In-situ electrochemical characterizations and finite element simulations reveal that the protective interphase regulates interfacial ion distribution and promotes a uniform 3D diffusion pathway. Moreover, Zn||NaV₃O₈·1.5H₂O (NVO) full battery with DMAP-V₁₀ electrolyte affords markedly enhanced rate capability and long-term cycling stability. This work demonstrates the effectiveness of redox-mediated interphase engineering for stabilizing Zn anodes and provides a viable pathway toward next-generation high-performance AZIBs.