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

Abstract

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_v) and a carbon shell (CoP_v@C) to effectively anchor polysulfides (LiPSs) and promote their conversion. The introduction of P_v notably enhances the binding energy between CoP and LiPSs, facilitating the subsequent cleavage of the SS bond in the Li₂S₆ 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_v@C nanofibers, the nucleation of Li₂S exhibits rapid liquid–solid conversion dynamics, adhering to a three-dimensional progressive nucleation model. Consequently, in our case, Li-S batteries assembled with CoP_v@C-modified separators exhibit an initial capacity of 1,536 mAh g⁻¹ 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_v@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.