Investigation of Cathode Structure and Electrolyte Chemistry for Emerging Metal-Tellurium Batteries

Abstract

Tellurium (Te) has received rising attention as electrode materials in next-generation high-energy-density rechargeable batteries due to its superior electronic conductivity and comparable specific volumetric capacity compared to conversion-type sulfur or selenium. To date, there is a lack of comprehensive understanding regarding the fundamental electrochemistry, structure design and electrolyte chemistry in emerging metal-Te battery systems. Herein, extensive efforts have been made in our group to figure out the role of carbon host in Te/C cathode architecture and construct highly stable Te/C cathodes. Our finding is that an ideal porous carbon is required to possess a majority of micropores to confine Te active materials and a small portion of mesopores to facilitate electrolyte wetting and Li-ion transport. Importantly, a durable Li-Te battery over 1,000 cycles at 2C was achieved with microporous carbon as Te host to constrain volume change of Te. A quasi-solid-state Li-Te is also constructed and demonstrates superior cycling and rate performance than Li-S/Se batteries with the same cell configuration. Moreover, the electrolyte chemistry and reaction mechanism in K-Te battery system are comprehensively revealed from the aspects of redox kinetics and surface chemistry. The two electrolyte salts (potassium hexafluorophosphate, KPF6 and potassium bis(fluorosulfonyl)imide, KFSI) induce similar phase transformation but different specific capacity, reaction kinetics, and SEI composition on the Te/C cathode. These findings are expected to promote the development of Te-based next-generation energy storage systems.