Constructing a Multifunctional Sandwich-Structured Sulfur Host To Enhance Energy Density and Cycling Life in Lithium–Sulfur Battery

Abstract

Lithium–sulfur (Li–S) batteries are recognized as promising next-generation energy storage devices due to their high theoretical energy density (2600 Wh kg^–1). However, their practical applications still face challenges, such as low S utilization and short cycling life, primarily attributed to the notorious shuttle effect of lithium polysulfides (LiPSs) and sluggish redox kinetics. To address these issues, rationally designing and synthesizing a novel multifunctional S host that acts as a capturer, catalyst, and conductor is considered to be an effective strategy. Herein, we synthesized a unique sandwich-structured S host for the first time (designated as S/VS₂–NCNTs), where the network-like conductive nitrogen-doped carbon nanotubes (NCNTs) uniformly coat the surface of few-layer two-dimensional (2D) VS₂ nanosheets, preventing 2D VS₂ stacking. This sandwich structure exhibits excellent adsorptive, catalytic, and conductive properties toward LiPSs, enhancing redox kinetics via the rapid e^–/Li⁺ transfer/diffusion. Benefiting from these superior properties, the electrochemical performances of Li–S batteries are significantly improved. At a high rate of 2 C, after 1000 ultralong and stable cycles, the capacity remains at 805.9 mAh g^–1, with an ultralow decay rate of 0.021% per cycle in coin batteries. Notably, even under high S loading (7.2 mg cm^–2, S content of 89 wt %) and limited electrolyte (E/S ratio of 5.1 μL mg^–1), it achieves a high areal capacity of 4.76 mAh cm^–2 (specific capacity of 703.4 mAh g^–1, volume capacities of 719.6 mAh cm^–3) after 200 cycles at 0.5 C. More strikingly, for pouch batteries, it maintains a specific capacity of 614.6 mAh g^–1 after 200 cycles at 1 C. The design and development of a novel multifunctional S host represent a promising strategy to enhance S utilization and extend long-cycle life in high-energy-density Li–S battery