High‐Efficiency and Stable Zn−Na3V2(PO4)3 Aqueous Battery Enabled by Electrolyte‐Induced Interphasial Engineering

Abstract Aqueous zinc batteries have been regarded as a promising energy storage technology due to their high energy, high material abundance, low toxicity, and intrinsic safety. NASICON‐type materials have been proposed as efficient cathodes for rechargeable batteries, yet they suffer from fast degradation and low Coulombic efficiency in aqueous batteries. Here we demonstrate that a rationally designed aqueous electrolyte containing a supporting Na salt and polymer additive can efficiently suppress the water activity through hydrogen bonding and facilitate the anion involvement in interfacial reactions, thus enabling the stable operation of sodium superionic conductor (NASICON) cathodes in aqueous zinc batteries. As exemplified by a Na 3 V 2 (PO 4 ) 3 cathode, the cell with zinc metal anode exhibits high cycling Coulombic efficiencies (around 99.9 % in average) with a steady output voltage and capacity retention for 300 cycles. This work addresses the potential issues with NASICON‐type cathodes in aqueous zinc batteries and proposes an effective solution via fundamental interphasial chemistry to design efficient and sustainable aqueous electrolytes.