A High‐Energy Tellurium Redox‐Amphoteric Conversion Cathode Chemistry for Aqueous Zinc Batteries

Rechargeable aqueous zinc batteries are potential candidates for sustainable energy storage systems at a grid scale, owing to their high safety and low cost. However, the existing cathode chemistries exhibit restricted energy density, which hinders their extensive applications. Here, a tellurium redox-amphoteric conversion cathode chemistry is presented for aqueous zinc batteries, which delivers a specific capacity of 1223.9 mAh g_Te ^-1 and a high energy density of 1028.0 Wh kg_Te ^-1. A highly concentrated electrolyte (30 mol kg^-1 ZnCl₂) is revealed crucial for initiating the Te redox-amphoteric conversion as it suppresses the H₂O reactivity and inhibits undesirable hydrolysis of the Te⁴⁺ product. By carrying out multiple operando/ex situ characterizations, the reversible six-electron Te^2-/Te⁰/Te⁴⁺ conversion with TeCl₄ is identified as the fully charged product and ZnTe as the fully discharged product. This finding not only enriches the conversion-type battery chemistries but also establishes a critical step in exploring redox-amphoteric materials for aqueous zinc batteries and beyond.