Accelerating lithium polysulfides conversion kinetics with bimetallic phosphide Ni2P/CoP composite as a multifunctional separator in advanced lithium-sulfur batteries

Abstract

Lithium-sulfur (Li-S) batteries face challenges such as lithium polysulfides (LiPSs) shuttle, slow reaction kinetics, and volume expansion. Transition metal phosphides (TMPs) show great potential in effectively accelerating the conversion of LiPSs. In this study, we synthesize a bimetallic phosphide Ni2P/CoP composite supported on petal-like nitrogen-doped carbon nanosheets (Ni2P/CoP/NC) through a metal-chelate-assisted self-sacrificial template method, utilizing phytic acid as the phosphorus source and melamine as the carbon precursor. As a separator modifier, this petal-shaped Ni2P/CoP/NC has a stable structure and abundant active sites. Furthermore, the synergistic effect of Ni2P and CoP enhances the composite’s adsorption properties and catalytic activity, effectively suppressing LiPSs shuttle and improving electrochemical performance. The Ni2P/CoP/NC-modified separator demonstrates a high initial capacity of 1224.6 mAh g-1, excellent rate capability (482.4 mAh g-1 at 4 C), and good cycling stability with a low capacity decay of 0.056% per cycle over 800 cycles at 1 C. Additionally, a C/S cathode with high sulfur loading of 11.86 mg cm-2 is manufactured using 3D printing (3DP) technology, and the 3D printed battery assembled by Ni2P/CoP/NC-PP separator delivers an areal capacity of 11.69 mAh cm-2. This study presents a novel approach for developing multifunctional separators and high-performance Li-S batteries.