Engineering cobalt phosphide with anion vacancy and carbon shell for kinetically enhanced lithium-sulfur batteries.

The widespread adoption of lithium-Sulfur (Li-S) batteries is significantly hindered by the well-known "shuttle effect" and the sluggish conversion kinetics of sulfur species. In this study, cobalt phosphide (CoP) nanoparticles are engineered with phosphorus vacancies (P) and a carbon shell (CoP@C) to effectively anchor polysulfides (LiPSs) and promote their conversion. The introduction of P notably enhances the binding energy between CoP and LiPSs, facilitating the subsequent cleavage of the SS bond in the LiS molecule. The carbon shell further aids in the chemical adsorption of LiPSs by generating a space charge region, while simultaneously shielding CoP nanoparticles from direct exposure to oxidative conditions during charge/discharge cycles. On the surface of CoP@C nanofibers, the nucleation of LiS exhibits rapid liquid-solid conversion dynamics, adhering to a three-dimensional progressive nucleation model. Consequently, in our case, Li-S batteries assembled with CoP@C-modified separators exhibit an initial capacity of 1,536 mAh g at 0.1 C. Significantly, Li-S batteries can afford 4 C discharge/charge along with a superior 0.019 % decline rate. These findings position CoP@C nanofibers as a promising material for advanced Li-S batteries and offer novel insights into the design of electrocatalysts and separator engineering for high-performance Li-S batteries.