Topological insulator bismuth selenide with a unique cloud-like hollow structure as a bidirectional electrocatalyst for robust lithium–sulfur batteries

Abstract

Lithium–sulfur (Li–S) batteries have attracted widespread attention because of their high energy density, low cost and environmentally friendly nature. Unfortunately, the practical applicability of Li–S batteries is seriously restricted by the shuttle effect and sluggish reaction kinetics of soluble lithium polysulfides (LiPSs). Herein, strong topological insulator (TI) Bi₂Se₃ and weak TI BiSe with unique cloud-like hollow structures have been rationally synthesized and employed as separator modifiers for Li–S batteries. The strong TI Bi₂Se₃ possesses abundant active sites, high electrical conductivity, strong chemical adsorption, superior catalytic activity and robust surface states, which significantly accelerates the redox conversion kinetics, mitigates the shuttle effect of LiPSs and improves the sulfur utilization. Consequently, Li–S batteries with strong TI Bi₂Se₃ modified separators demonstrate impressive practical prospects in terms of high discharge capacity (1568.8 mA h g⁻¹ at 0.1C), remarkable rate capability (866.3 mA h g⁻¹ at 5.0C) and a stable capacity of 524.3 mA h g⁻¹ over 500 cycles at 1C (corresponding to a capacity decay rate of 0.086%). The performance enhancements are further supported by theoretical calculations. This work might provide valuable insights into the delicate design and synthesis of TI materials with desired morphology and structure to boost their performance for energy storage.