Niobium Boride/Graphene Directing High-Performance Lithium–Sulfur Batteries Derived from Favorable Surface Passivation
Yanjuan Li, Zhanzhan Wang, Hongfei Gu, Hongpeng Jia, Zhouyang Long, Xiao Yan
Abstract
Efficient catalysts are needed to accelerate the conversion and suppress the shuttling of polysulfides (LiPSs) to promote the further development of lithium–sulfur (Li–S) batteries. Intermetallic niobium boride (NbB 2 ) has indefinite potential due to superior catalytic activity. Nonetheless, the lack of a rational understanding of catalysis creates a challenge for the design of catalysts. Herein, a NbB 2 /reduced graphene oxide-modified PP separator (NbB 2 /rGO/PP) is rationally designed. Essential, an in-depth insight into the catalysis mechanism of NbB 2 toward LiPSs is established based on experiments and multiperspective measurement characterization, ab initio molecular dynamics (AIMD), and density functional theory (DFT). It has been uncovered that the actual catalyst that interacts with LiPSs in NbB 2 is the passivated surface with an oxide layer (O 2 –NbB 2 ), which occurs through B–O–Li and Nb–O–Li bonds, rather than the clean NbB 2 surface. And the decomposition barrier of Li 2 S is greatly reduced by a substantial margin, dropping from 3.390 to 0.93 and 0.85 eV on the Nb–O and B–O surfaces, respectively, with fast Li + diffusivity. Consequently, the cell with NbB 2 /rGO/PP as a functional separator achieves a high discharge capacity of 873 mAh g –1 at 1C after 100 cycles. Moreover, the benefits of NbB 2 /rGO/PP can be effectively maintained even at a high sulfur loading of 7.06 mg cm –2 without significant reduction and with a low electrolyte/sulfur ratio of 8 μL mg –1 s . This study enhances our understanding of the catalytic mechanism of Li–S systems and presents a promising approach for developing electrocatalysts that are resilient to poisoning.