The application of aqueous Zn-ion hybrid capacitors (AZHCs) at extreme temperatures is hindered by electrolyte freezing, sluggish cation de-solvation, and low power/energy densities. Herein, we propose a novel weakly-solvating “localized water-in-salt” (ws-LWIS) electrolyte strategy that synergizes the advantage of LWIS electrolytes and ws-electrolytes. The ws-LWIS electrolyte creates a simultaneous weak solvation structure and LWIS structure by introducing acetonitrile into the zinc perchlorate electrolyte. By optimizing the water content and solvation structure, the adverse impact of low temperature on diffusion and de-solvation kinetics of Zn2 + ions are mitigated. Consequently, a broad electrochemical stability window (0 −2.5 V) and boosted fast-charging/discharging cycling stability (88.2 % of initial capacity at 10 A/g after 3000 cycles) at −50 °C are achieved. AZHCs deliver a specific capacity of 165.1 F/g under a current density of 1.0 A/g at −50 °C, retaining 88.2 % of the capacity at 25 °C. Notably, the device achieves an energy density of 143.3 Wh/kg (2.6 times that of conventional WIS electrolytes) and a power density of 2.5 kW/kg at −50 °C. Even at a 10-fold higher power density, the energy density remains as high as 66.5 Wh/kg, superior to state-of-the-art performance of AZHCs under similar conditions.
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