Morphology and electron regulation of B-WS2@MXene nanosheet array heterojunctions to upgrade the capacity and longevity of lithium–sulfur batteries

Abstract

Tailor-made separator modifiers for the interception and conversion of polysulfides are an effective approach to achieve high-performance lithium–sulfur (Li–S) batteries. Herein, a morphology and electron regulation strategy based on the nanosheet array structure of MXene and boron-doped WS₂ nanosheets has been proposed for polypropylene (PP) separator modification. The nanoarray architecture based on C–Ti–S covalent connections between MXene and boron-doped WS₂ significantly expedites electron transfer and optimizes mass transport dynamics. Concurrently, the activated WS₂ basal plane effectively inhibits the shuttle effect of polysulfides and expedites the electrocatalytic conversion of intercepted polysulfides. At a lean electrolyte of 5 μL mg⁻¹ and high sulfur loading of 6.5 mg cm⁻², the cell synchronously acquires high specific capacity of 1227 mA h g⁻¹, an areal capacity of 7.9 mA h cm⁻² and volumetric capacity of 1246 mA h cm⁻³. Moreover, the pouch cell assembled with the modified separator achieves a high capacity of 204 mA h g⁻¹ and a volumetric energy density of 400 W h L⁻¹. This work provides a facile and hopeful protocol toward separator modification to develop high-energy-density and long-lifetime Li–S batteries.