An in situ constructed VO2–VN binary host was realized to accomplish smooth immobilization–diffusion–conversion of polysulfides, targeting high-sulfur-load Li–S batteries.

The lithium–sulfur (Li–S) battery is regarded as a next‐generation energy storage system due to its conspicuous merits in high theoretical capacity (1672 mAh g−1), overwhelming energy density (2600 Wh kg−1), and the cost‐effectiveness of sulfur. However, the practical application of Li–S batteries is still handicapped by a multitude of key challenges, mainly pertaining to fatal lithium polysulfide (LiPS) shuttling and sluggish sulfur redox kinetics. In this respect, rationalizing electrocatalytic processes in Li–S chemistry to synergize the entrapment and conversion of LiPSs is of paramount significance. This review summarizes recent progress and well‐developed strategies of the mediator design toward promoted Li–S chemistry. The current advances, existing challenges, and future directions are accordingly highlighted, aiming at providing in‐depth understanding of the sulfur reaction mechanism and guiding the rational mediator design to realize high‐energy and long‐life Li–S batteries.

The ever-growing demand for high-energy and long-life energy storage devices has spurred extensive research beyond conventional lithium-ion battery systems. Amongst these, rechargeable lithium-sulfur (Li-S) batteries, as a promising next-generation energy storage technology, have captured vast interest because of the high capacity (1672 mAh g −1 ), large abundance of sulfur, and environmental compatibility. [1][2][3][4] Although there has been significant advance by far in designing state-of-theart Li-S batteries, their practical utilization and large-scale commercialization are still impeded by a multitude of technological obstacles, namely, i) the insulating nature of S/Li 2 S that would jeopardize the overall conductivity of the electrode and hence affect the utilization of sulfur; ii) the shuttle effect induced by the dissolution and diffusion of lithium polysulfide that could lead to a rapid capacity fading; and iii) the considerable volume expansion of the sulfur cathode upon cycling. [5,6] To tackle these issues, great efforts have been devoted to developing appropriate host materials in combination with optimizing the cathode architectures toward advanced Li-S batteries. A ubiquitously employed strategy is to encapsulate sulfur and/or polysulfides with the aid of porous carbonaceous materials, such as carbon nanotubes, [1,[7][8][9][10] hollow carbon spheres, [11,12] and graphene, [13][14][15] aiming to attain enhanced electrode conductivity, improved sulfur utilization, and buffered volume change. However, this has been proved to be far from ideal, owing to weak van der Waals (vdW) interaction between nonpolar carbon and polar polysulfide species that only gives rise to a physical confinement, insufficient to alleviate the polysulfide shuttle over a long lifespan. In this regard, the introduction of polar nanomaterials (e.g., transition metal oxides, [16][17][18] sulfides, [19][20][21] and nitrides [22,23] ) within the sulfur host has witnessed an efficient suppression of shuttle effect, where polysulfides are chemically anchored onto these polar species. Nevertheless, the limited electrical conductivity of most metal oxides/sulfides would otherwise result in sluggish kinetics of polysulfide redox reactions, inevitably causing poor rate capability and fast capacity decay. Latest investigations have revealed that the integration of polar nanocrystals/nanosheets Lithium-sulfur (Li-S) batteries are deemed to be one of the most promising energy storage technologies because of their high energy density, low cost, and environmental benignancy. However, existing drawbacks including the shuttling of intermediate polysulfides, the insulating nature of sulfur, and the considerable volume change of sulfur cathode would otherwise result in the capacity fading and unstable cycling. To overcome these challenges, herein an in situ assembly route is presented to fabricate VS 2 /reduced graphene oxide nanosheets (G-VS 2 ) as a sulfur host. Benefiting from the 2D conductive and polar VS 2 interlayered within a graphene fra...