Protective Solid Interphase via Composite Additives for Long-Life Aqueous Zinc Batteries

Here, we report a composite additive strategy that integrates sodium hexametaphosphate (SHMP) and sodium molybdate (NMO) to achieve cooperative regulation of the electrolyte bulk chemistry and the Zn–electrolyte interface. SHMP reconstructs the Zn 2+ solvation structure through controlled coordination, while NMO mitigates overchelation via pH buffering and preferential interfacial adsorption. Their cooperation induces the in situ formation of a chemically coupled Mo/P-rich interphase, which regulates ion flux, limits proton-driven side reactions, and maintains Zn deposition kinetics. Comprehensive experiments and theoretical calculations elucidate the bulk–interface coupling governing Zn 2+ transport and reversibility. Consequently, the resulting electrolyte enables 3700 h reversible cycling in Zn||Zn cells, 99.85% average Coulombic efficiency over 5100 cycles in Zn||Cu cells, and 78.9% capacity retention after 2500 cycles in Zn||MnO 2 cells. This work presents a general dual-regulation paradigm for Zn electrolyte design and provides mechanistic insights into developing aqueous zinc-ion batteries.