Synergistic improvements on capacity and Coulombic efficiency of lithium-sulfur batteries with NiSe-Ni2P/C modification on PP separators

Abstract

Lithium-sulfur batteries (LSBs) emerge as promising energy storage devices due to their high theoretical energy density. So far, there are constrained issues that need to be urgently addressed, such as the shuttle effect of lithium polysulfides (LiPS) and the sluggish kinetics of redox reactions. Herein, NiSe-Ni2P/C composite was synthesized and casted on the cathode side of polypropylene (PP) separator. This investigation reveals that the adsorption-catalysis synergistic effect of NiSe-Ni2P/C composite, accelerates the reduction of LiPS to lithium sulfide (Li2S) as well as the oxidation of Li2S. The synergistic effect effectively mitigates the shuttle effect of LiPS, reduces concentration polarization, and improves Coulombic efficiency (CE) throughout the entire lifespan. At a current density of 0.05 C, LSBs with NiSe-Ni2P/C modified PP separators exhibit a remarkable high initial CE of 97.0% and a substantial discharge specific capacity of 1205.4 mAh gs−1. Even under conditions of a high sulfur loading (4.3 mg cm−2) and a limited electrolyte dosage (10 μL mgs−1), the LSBs maintained a reversible specific capacity of 804 mAh gs−1, a CE of 94%, and an energy density of 1232.1 Wh kgs−1 after 720 h of continuous cycling at 0.05 C. This work provides a solution for achieving long-time, high-capacity, and high-CE electrochemical performance in LSBs with a high sulfur loading and a limited electrolyte dosage.