Tellurium with Reversible Six-Electron Transfer Chemistry for High-Performance Zinc Batteries

Chalcogens, especially tellurium (Te), as conversion-type cathodes possess promising prospects for zinc batteries (ZBs) with potential rich valence supply and high energy density. However, the conversion reaction of Te is normally restricted to the Te^2-/Te⁰ redox with a low voltage plateau at ∼0.59 V (vs Zn²⁺/Zn) rather than the expected positive valence conversion of Te⁰ to Teⁿ⁺, inhibiting the development of Te-based batteries toward high output voltage and energy density. Herein, the desired reversible Te^2-/Te⁰/Te²⁺/Te⁴⁺ redox behavior with up to six-electron transfer was successfully activated by employing a highly concentrated Cl^--containing electrolyte (Cl^- as strong nucleophile) for the first time. Three flat discharge plateaus located at 1.24, 0.77, and 0.51 V, respectively, are attained with a total capacity of 802.7 mAh g^-1. Furthermore, to improve the stability of Teⁿ⁺ products and enhance the cycling stability, a modified ionic liquid (IL)-based electrolyte was fabricated, leading to a high-performance Zn∥Te battery with high areal capacity (7.13 mAh cm^-2), high energy density (542 Wh kg_Te^-1 or 227 Wh L_{cathdoe+anode}^-1), excellent cycling performance, and a low self-discharge rate based on 400 mAh-level pouch cell. The results enhance the understanding of tellurium chemistry in batteries, substantially promising a remarkable route for advanced ZBs. © 2023 American Chemical Society.