SnO2/h-BN nanocomposite modified separator as a high-efficiency polysulfide trap in lithium–sulfur batteries

Abstract

Lithium–sulfur batteries are one of the most promising alternatives to traditional lithium-ion batteries because of their exceptionally high theoretical energy density and low cost. However, the weak electrical conductivity of sulfur and capacity deterioration brought on by the shuttle effect of lithium polysulfides (LiPSs) limit the practical applications of Li–S batteries. Herein, we propose an efficient approach of using a two-dimensional material (h-BN) composite with SnO₂ in the separator to inhibit the mass transport of polysulfides from the cathode and subsequent parasitic reactions on the metallic lithium anode. The optimum concentration of 10 wt% h-BN was found to be sufficient to form SnO₂/h-BN with improved electrochemical behavior and induce a rapid conversion of trapped polysulfides. As a result, Li–S batteries with a separator modified with SnO₂/10% h-BN showed an improved specific capacity of 620 mA h g⁻¹ at 1C, which was maintained at 485 mA h g⁻¹ with a coulombic efficiency of 99% after 350 cycles. Furthermore, self-discharge studies suggest the feasibility of a modified separator for commercial applications.