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...

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The practical application of lithium-sulfur (Li-S) batteries is hindered by their poor cycling stabilities that primarily stem from the "shuttle" of dissolved lithium polysulfides. Here, we develop a nepenthes-like N-doped hierarchical graphene (NHG)-based separator to realize an efficient polysulfide scavenger for Li-S batteries. The 3D textural porous NHG architectures are realized by our designed biotemplating chemical vapor deposition (CVD) approach via the employment of naturally abundant diatomite as the growth substrate. Benefiting from the high surface area, devious inner-channel structure, and abundant nitrogen doping of CVD-grown NHG frameworks, the derived separator favorably synergizes bifunctionality of physical confinement and chemical immobilization toward polysulfides, accompanied by smooth lithium ion diffusions. Accordingly, the batteries with the NHG-based separator delivers an initial capacity of 868 mAh g with an average capacity decay of only 0.067% per cycle at 2 C for 800 cycles. A capacity of 805 mAh g can further be achieved at a high sulfur loading of ∼7.2 mg cm. The present study demonstrates the potential in constructing high-energy and long-life Li-S batteries upon separator modification.

Despite the recent advancement in the in‐practical active materials (e.g., silicon, sulfur) in the rechargeable lithium‐ion energy storage systems, daunting challenges still remain for these high‐capacity electrode material candidates to overcome the severe volume changes associated with the repeated lithiation/delithiation process. Herein, developing a room‐temperature covalently cross‐linked polyacrylamide (c‐PAM) binder with high stretchability and abundant polar groups targeting the construction of high‐performance Si and sulfur electrodes is focused on. The robust 3D c‐PAM binder network enables not only significant enhancement of the strain resistance for working electrodes but also strong affinity to bonding with nano‐Si surface as well as effective capture of the soluble Li2Sn intermediates, thereby giving rise to remarkably improved cycling performances in both types of electrodes. This rational design of such an effective and multifunctional binder offers a pathway toward advanced energy storage implementations.

We reported a facile approach to fabricate graphene nanoplatelets (GNPs)/epoxy composites with a novel blend method. The influence of GNPs on the thermal and electrical properties was investigated. Compounds with different GNPs content (0-8 wt%) were mixed with a Flacktek speedmixer at a speed of 3000 rpm for 5 min. The thermal conductivity of the epoxy composites with 8 wt% GNPs was 1.181 W/m K, which is increased by 627% compared with those of the neat epoxy. It is found that the thermal stability and electrical property also have a certain degree of improvement. Scanning electron microscopy images demonstrate that the structures of the composites have a closed relationship with their properties. In addition, the incorporation of GNPs in epoxy matrix indicated excellent Vickers hardness at the low weight fractions of GNPs. POLYM. COMPOS., 36:556-565, 2015.