Trade-off effect of 3d transition metal doped boron nitride on anchoring polysulfides towards application in lithium-sulfur battery

Abstract

Sulfur cathodes in lithium-sulfur batteries (LSBs) suffer from the notorious "shuttle effect", low sulfur use ratio, and tardy transformation of lithium polysulfides (LiPSs), while using two-dimensional (2D) polar anchoring materials combined with single-atom catalysis is one of the promising methods to address these issues. Herein, the 3d transition metal (TM) doped 2D boron nitrides (BN), labeled as TM-BN, are studied for the anchoring and redox kinetics of LiPSs using first principles calculations. From the simulated results, the TM atom and adjacent N atoms are active adsorption sites for binding S atoms in LiPSs/S₈ and Li atoms in LiPSs, respectively. A negative d-band center closer to the Fermi level of TM-BN is key for enhancing the binding strength of TM-S and lowering the Li₂S decomposition energy barrier, while it deteriorates the activity of adjacent N atoms. Fortunately, the electrolyte environment has little effect on the superiority of the TM-BN for binding polysulfides/S₈, guaranteeing the sturdy anchor of polysulfides/S₈ in realistic conditions. The trade-off effect on the activities of TM and adjacent N atom sites in TM-BN for binding LiPSs highlights the excellence of Ti/V/Cr-BN as modification materials for LSB.

Keywords: 3d transition metal doping; Boron nitride; First principles theory; Lithium-sulfur battery; Trade-off effect.