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 gTe-1 and a high energy density of 1028.0 Wh kgTe-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 Te2-/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. A tellurium redox-amphoteric conversion cathode chemistry is demonstrated for aqueous zinc batteries with a highly concentrated ZnCl2 electrolyte, achieving a specific capacity of 1223.9 mAh gTe-1 and an outstanding energy density of 1028.0 Wh kgTe-1. The reversible six-electron Te2-/Te0/Te4+ conversion is disclosed with TeCl4 as the fully charged product and ZnTe as the fully discharged product. image