Localized Anion‐Cation Aggregated Aqueous Electrolytes with Accelerated Kinetics for Low‐Temperature Zinc Metal Batteries

Abstract

AbstractAqueous zinc metal batteries hold great promise for large‐scale energy storage because of their high safety, rich material resources and low cost. However, the freeze of aqueous electrolytes hinders low‐temperature operation of the batteries. Here, aqueous localized anion‐cation aggregated electrolytes composed of Zn(BF4)2 as the salt and tetrahydrofuran (THF) as the diluent, are developed to improve the low‐temperature performance of the Zn anode. THF promotes the inclusion of BF4− in the solvation sheath of Zn2+, facilitating the formation of ZnF2‐rich solid‐electrolyte‐interphase. THF also affects the hydrogen bonding between neighboring H2O molecules, effectively lowering the freezing point. Therefore, the full cells of Zn||polyaniline (PANI) exhibit an ultralong cycle life of 8000 cycles with an average Coulombic efficiency of 99.99 % at −40 °C. Impressively, the pouch cells display a high capacity retention of 86.2 % after 500 cycles at −40 °C, which demonstrates the great prospect of such electrolytes in cold regions. This work provides new insights for the design of low‐temperature aqueous electrolytes.