Amorphous/crystalline heterostructure design enables highly efficient adsorption–diffusion–conversion of polysulfides for lithium–sulfur batteries

Abstract

Electrocatalytic conversion of soluble lithium polysulfides (LiPSs) has been proposed as a crucial approach to address the drawbacks of lithium–sulfur (Li–S) batteries. However, it still remains a great challenge to realize the integration of strong adsorption and high catalytic activity within a single electrocatalyst. Herein, we conceptually demonstrate the rational design and synthesis of a crystalline Bi₂Se₃ and amorphous BiO_x heterostructure (denoted as c-Bi₂Se₃/a-BiO_x) as an advanced separator modifier for Li–S batteries. In such a heterostructure, a-BiO_x has strong chemical adsorption ability toward LiPSs and c-Bi₂Se₃ possesses high catalytic activity for LiPS conversion. Meanwhile, the heterointerface enables rapid diffusion of LiPSs from a-BiO_x to c-Bi₂Se₃, thus synergistically contributing to the highly efficient adsorption–diffusion–conversion process of LiPSs. Benefiting from these advantages, Li–S batteries using a c-Bi₂Se₃/a-BiO_x heterostructure modified separator exhibit excellent electrochemical performance in terms of high discharge capacity (1517.9 mA h g⁻¹ at 0.1C), outstanding rate capacity (873.1 mA h g⁻¹ at 4C) and long-term cycling stability with a low capacity decay rate of 0.041% per cycle over 1000 cycles at 1C. Furthermore, a remarkable areal capacity of 3.85 mA h cm⁻² can be achieved at a high sulfur loading of 5.5 mg cm⁻². This work provides valuable insight into the development of crystalline/amorphous heterostructures as robust and highly active electrocatalysts for high-performance Li–S batteries.