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 ZnCl 2 ) is revealed crucial for initiating the Te redox-amphoteric conversion as it suppresses the H 2 O reactivity and inhibits undesirable hydrolysis of the Te 4+ product. By carrying out multiple operando/ex situ characterizations, the reversible six-electron Te 2- /Te 0 /Te 4+ conversion with TeCl 4 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.