A Reversible Six-Electron Transfer Cathode for Advanced Aqueous Zinc Batteries

The electrochemical reactions for the storage of Zn2+ while embracing more electron transfer is a foundation of the future high-energy aqueous zinc batteries. Herein, we report a six-electron transfer electrochemistry of nano-sized TeO2 /C (n-TeO2 /C) cathode by facilitating the reversible conversion of TeO2 ↔Te and Te↔ZnTe. Benefitting from the integrated conductive nanostructure and the proton-rich environment in providing optimized electrochemical kinetics (facilitated Zn2+ uptake and high electronic conductivity) and feasible thermodynamic process (low Gibbs free energy change), the as-prepared n-TeO2 /C with stable cycling performance exhibits a superior reversible capacity of over 800 mAh g-1 at 0.1 A g-1 . A precise understanding of the reaction mechanism via ex situ and in situ characterizations presents that the reversible six-electron transfer reaction is proton-dependent, and a proton generating and consuming mechanism of three-phase conversion n-TeO2 /C in the weakly acidic electrolyte is thoroughly revealed.