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

Abstract

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– /Te 0 redox with a low voltage plateau at ∼0.59 V (vs Zn 2+ /Zn) rather than the expected positive valence conversion of Te 0 to Te n +, inhibiting the development of Te-based batteries toward high output voltage and energy density. Herein, the desired reversible Te 2– /Te 0 /Te 2+ /Te 4+ 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 Te n + 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.