Built-In Catalysis in Confined Nanoreactors for High-Loading Li-S Batteries

Theoretical investigation on lithium polysulfide adsorption and conversion for high-performance Li-S batteries

Lithium-sulfur (Li-S) batteries have shown great application prospects as next-generation energy storage systems due to their high theoretical capacity and high energy density. However, the practical application of Li-S batteries is still hindered by several challenges, such as their sluggish sulfur redox kinetics and shuttle effect of lithium polysulfides (LiPSs). To date, significant research has been focused on the confinement adsorption and catalytic conversion of LiPSs using theoretical or/and experimental methods. Among them, theoretical calculations are highly attractive to observe complex LiPS conversion reactions, which facilitate the rational design of S mediators for high-performance Li-S batteries. In this review, we summarize and discuss the recent advances in the adsorption and conversion of LiPSs from the viewpoint of theoretical calculations. Moreover, a set of theoretical principles to guide the screening of suitable host materials for Li-S batteries is presented and discussed. Finally, some personal insights about the future challenges and the focus of research in this field are presented, which will push a milestone step toward high-efficiency and long-life Li-S batteries.

Defective VSe2-Graphene Heterostructures Enabling In Situ Electrocatalyst Evolution for Lithium-Sulfur Batteries

Electrocatalysts remain vitally important for the rational management of intermediate polysulfides (LiPSs) in the realm of Li-S batteries. In terms of transition-metal-based candidates, in situ evolution of electrocatalysts in the course of an electrochemical process has been acknowledged; nevertheless, consensus has not yet been reached on their real functional states as well as catalytic mechanisms. Herein, we report an all-chemical vapor deposition design of the defective vanadium diselenide (VSe₂)-vertical graphene (VG) heterostructure on carbon cloth (CC) targeting a high-performance sulfur host. The electrochemistry induces the sulfurization of VSe₂ to VS₂ at Se vacancy sites, which propels the adsorption and conversion of LiPSs. Accordingly, the VSe₂-VG@CC/S electrode harvests an excellent cycling stability at 5.0 C with a capacity decay of only 0.039% per cycle over 800 cycles, accompanied by a high areal capacity of 4.9 mAh cm^-2 under an elevated sulfur loading of 9.6 mg cm^-2. Theoretical simulation combined with operando characterizations reveals the key role played by the Se vacancy with respect to the electrocatalyst evolution and LiPS regulation. This work offers insight into the rational design of heterostructure sulfur hosts throughout defect engineering.

Enhanced Multiple Anchoring and Catalytic Conversion of Polysulfides by Amorphous MoS3 Nanoboxes for High-Performance Li-S Batteries

The practical implementation of lithium-sulfur batteries is obstructed by poor conductivity, sluggish redox kinetics, the shuttle effect, large volume variation, and low areal loading of sulfur electrodes. Now, amorphous N-doped carbon/MoS₃ (NC/MoS₃ ) nanoboxes with hollow porous architectures have been meticulously designed as an advanced sulfur host. Benefiting from the enhanced conductivity by the N-doped carbon, reduced shuttle effect by the strong chemical interaction between unsaturated Mo and lithium polysulfides, improved redox reaction kinetics by the catalytic effect of MoS₃ , great tolerance of volume variation and high sulfur loading arising from flexible amorphous materials with hollow-porous structures, the amorphous NC/MoS₃ nanoboxes enabled sulfur electrodes to deliver a high areal capacity with superior rate capacity and decent cycling stability. The synthetic strategy can be generalized to fabricate other amorphous metal sulfide nanoboxes.