Water-Modulated Electrolyte Enables Advanced Low-Temperature Zn-ion Battery

Abstract

Aqueous Zn-ion batteries face huge challenges at sub-zero temperatures due to electrolyte freezing and parasitic side reactions. Here, we present a low-temperature Zn-ion battery with a water-modulated Zn(BF4)2 electrolyte consisting of 1,3-dioxolane (DOL) and water in a 95:5 volume ratio. DOL was selected due to its low freezing point and ability to dissolve Zn(BF4)2 at high concentrations. A minimal water content is maintained to suppress ring-opening polymerisation of DOL., which prevents viscosity increment and conductivity losses, thereby preserves the electrolyte stability. Combining the computational simulations with experiments, results show that DOL molecules disrupt the H-bond network of the remaining water and alter the Zn2+ solvation structure, which suppresses the hydrogen evolution reaction and facilitates dendrite-free Zn deposition even under low temperature. The water-modulated electrolyte exhibits excellent low-temperature performance. Specifically, the Zn||MgVO full cell operates at –30 °C with over 90% capacity retention after 300 cycles at 1 C, and it sustains over 2000 cycles at a high rate of 10 C. This study confirms DOL modulation’s key role in achieving hydrogen-free and dendrite-free Zn anodes, advancing understanding of intermolecular interactions in low-temperature electrolyte design.