Promoting Zinc Plating and Silencing the Hydrogen Evolution Reaction through Spatial Decoupling for Durable Aqueous Zinc-Ion Batteries

An aqueous Zn-ion battery (AZIB), with its safety and cost benefits, is a promising technology for grid-scale energy storage applications. However, side reactions, such as the hydrogen evolution reaction (HER), occur synchronously with Zn plating, causing anode irreversibility and constituting a fundamental limitation of AZIBs. Herein, we propose a spatial decoupling strategy, using post-transition metal halide as an electrolyte additive to construct in situ microheterogeneity at the anode interface so as to decouple such synchronicity, promoting Zn plating while silencing the HER with solvating H 2 O “hopping” to the anchored halide anion. The work function of post-transitional metals and the polarizability of halide anions are key features in constructing such fast Zn 2+ conducting channels. As a result, using InBr 3 enhances the accumulated capacity of a Zn||Zn cell by 64 times from 0.074 to 4.8 Ah cm –2, the cycle life of a V 2 O 5 ||Zn battery by 100 times from 10 to >1000 cycles, and the stable capacity of a Mn 2 V 2 O 7 ||Zn battery by 70% from 83 to 141 mAh g –1 . We further introduce a feature matrix predicting efficient post-transitional metal cation and halide anion combinations to enhance the reversibility of metal deposition–dissolution reactions. This framework can be generalized to advance other battery chemistries both practically and mechanistically.