Achieving Bichelating Solvation Structure toward Fast Charging and Long Lifespan Aqueous Zn-Ion Batteries

Design optimized solvation structure of hydrated Zn²⁺ is an effective strategy for stabilizing Zn anodes and achieving decent performance for practical aqueous Zn-ion batteries (AZIBs). However, the mechanism for precise targeted design of solvation structures remains unclear. This study employs a space-confined regulation strategy through carbon chain shortening and amino migration to unveil the correlation between molecular conformation evolution and solvent sheath design. The findings demonstrate that carbon chain shortening and amino migration synergistically induce steric hindrance decrement, driving the transition from monopolar configuration to bisolvation-sheath-bichelation (BSB) configuration. The BSB structure facilitates Zn²⁺ migration through electrostatic repulsion induced by dual Zn²⁺ coordination, while enhancing Zn deposition/stripping kinetics via competitive anion desolvation. As a result, the Zn//Zn symmetric cell exhibits decent rate capability up to 30 mA cm^-2 and remarkable stability for 3600 hours under 5 mA cm^-2 and 5 mAh cm^-2. Moreover, the BSB structure has shown substantial enhancement in the cycling stability of Zn//V₂O₅ cells with 80% capacity retention after 1800 cycles at 2 A g^-1. This work not only offers a new bichelation solvation structure design strategy, but also provides insights for​ electrolyte engineering in the related energy storage and conversion area.