Ternary heterojunction nanobelts enable synergistic adsorption and catalytic conversion of polysulfide toward high-performance Li–S batteries

Abstract

Lithium–sulfur (Li–S) batteries have attracted extensive attention owing to their exceptionally high theoretical energy density. However, the shuttle effect and sluggish conversion kinetics of lithium polysulfide (LiPS) intermediates during the charge/discharge process severely hinder their practical application. Herein, ternary heterojunction nanobelts composed of MoO2, MoS2, and nitrogen-doped carbon (denoted as MoO2/MoS2@NC) are rationally designed as a separator modifier to simultaneously achieve strong chemical adsorption, enhanced catalytic activity, and high electrical conductivity. In this architecture, the three components are interconnected via Mo–N–C bridging pathways, which facilitate efficient electron transport among the MoO2 adsorbent, MoS2 catalyst, and nitrogen-doped carbon matrix. In situ Raman spectroscopy and electrochemical impedance spectroscopy reveal that the MoO2/MoS2@NC-modified separator enables rapid interfacial charge transfer, effectively suppresses the shuttle effect of LiPSs, and accelerates their catalytic conversion. As a result, the Li–S battery equipped with the modified separator delivers a high discharge capacity of 712 mAh g−1 at 5 C (1 C = 1675 mAh g−1), an ultralow capacity decay rate of 0.06% per cycle over 1000 cycles at 1 C, and a high initial areal capacity of 7.15 mAh cm−2 under harsh conditions, including a high sulfur loading of 7.28 mg cm−2 and a lean electrolyte with an E/S ratio of 8 μl mg−1.