Hydrated Intercalation for High-Performance Aqueous Zinc Ion Batteries

Abstract

Aqueous zinc ion batteries (AZIBs) are steadily gaining attention based on their attractive merits regarding cost and safety. However, there are many obstacles to overcome, especially in terms of finding suitable cathode materials and elucidating their reaction mechanisms. Here, a mixed-valence vanadium oxide, V6O13, that functions as a stable cathode material in mildly acidic aqueous electrolytes is reported. Paired with a zinc metal anode, this material exhibits performance metrics of 360 mAh g(-1) at 0.2 A g(-1), 92% capacity retention after 2000 cycles, and 145 mAh g(-1) at a current density of 24.0 A g(-1). A combination of experiments and density functional theory calculations suggests that hydrated intercalation, where water molecules are cointercalated with Zn ions upon discharge, accounts for the aforementioned electrochemical performance. This intercalation mechanism facilitates Zn ion diffusion throughout the host lattice and electrode-electrolyte interface via electrostatic shielding and concurrent structural stabilization. Through a correlation of experimental data and theoretical calculations, the promise of utilizing hydrated intercalation as a means to achieve high-performance AZIBs is demonstrated.