Unraveling H⁺/Zn²⁺ Sequential Conversion Reactions in Tellurium Cathodes for Rechargeable Aqueous Zinc Batteries

Abstract

Progress toward practical rechargeable aqueous zinc (Zn) batteries is impeded by the low energy density. The use of tellurium (Te) cathodes featuring multielectron redox reactions offers one possible approach to mitigating this dilemma. However, the corresponding energy-storage mechanisms in aqueous electrolytes are not established yet. Here, we uncover a H+/Zn2+-involved sequential conversion reaction with 6e– transfer for Te-based cathodes, which accounts for the outstanding capacity (over 460 mAh g–1 at 50 mA g–1). Two distinct redox processes, corresponding to TeO2 ↔ Te and Te ↔ ZnTe, are explicitly revealed within the electrochemical window of routine aqueous Zn electrolytes. The mechanism elucidated here complements the understanding of energy-dense Te centers and propels the exploration of high-capacity electrodes for multivalent battery chemistries.