Reversible Insertion of [AlCl4]− Superhalides in Graphite

Abstract

AbstractGraphite‐based dual‐ion batteries are with potential higher energy density, making them a unique candidate in energy storage systems. However, anion insertion into graphite in aqueous environment remains a significant challenge. Herein, we report that the reversible insertion of Al‐Cl superhalide into expanded graphite (EG) delivers an ultrahigh specific capacity of ~171 mAh g−1 from an aqueous deep eutectic solvent (DES) gel electrolyte of 50 m ChCl+5 m AlCl3. High‐resolution transmission electron microscopy (HRTEM), Raman spectra and X‐ray diffraction (XRD) show that the EG generates turbostratic structure during Al‐Cl superhalide (de)insertion instead of presenting typical graphite intercalation compounds (GIC), thus attributing to the high capacity during Al‐Cl superhalide insertion.