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

Du, Jingwei; Zhao, Yirong; Chu, Xingyuan; Wang, Gang; Neumann, Christof; Xu, Hao; Li, Xiaodong; Löffler, Markus et al. · Adv Mater · 2024

basic_science · Level V

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Abstract

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<sub>Te</sub> <sup>-1</sup> and a high energy density of 1028.0 Wh kg<sub>Te</sub> <sup>-1</sup>. A highly concentrated electrolyte (30 mol kg<sup>-1</sup> ZnCl<sub>2</sub>) is revealed crucial for initiating the Te redox-amphoteric conversion as it suppresses the H<sub>2</sub>O reactivity and inhibits undesirable hydrolysis of the Te<sup>4+</sup> product. By carrying out multiple operando/ex situ characterizations, the reversible six-electron Te<sup>2-</sup>/Te<sup>0</sup>/Te<sup>4+</sup> conversion with TeCl<sub>4</sub> 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.