Enhanced Zn2+ Transport in Ionic Liquid Electrolyte by Hydrofluoroether Dilution for High‐Power and Long‐Life Zn/Graphite Cells

Abstract

AbstractIonic liquid (IL) electrolytes have been widely used in high‐voltage Li‐based dual ion batteries (DIBs) due to their strong resistance against oxidation. However, their applications in Zn‐based DIBs are restricted because the high charge density of divalent Zn2+ aggravates the ionic interactions in ionic networks and leads to insufficient Zn2+ mobility. Herein, we introduce a hydrofluoroether diluent into a Zn‐based IL electrolyte to break down the larger ionic aggregates into smaller ones with weakened ionic interactions. This unique solvation structure reduces the Stokes radius of Zn2+ from 1.3 nm to 0.97 nm and increases its diffusion coefficient by ∼30 times while retaining the high oxidation stability, enabling the charge/discharge cycling of Zn/graphite DIBs at a high rate of 20 C. Moreover, the enhanced mobility of Zn2+ also promotes compact Zn deposition, which allows the operation of anode‐free Zn/graphite DIBs with 90 % capacity retention after 100 cycles.