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Lithium‐sulfur (Li−S) batteries are one of the most potential new energy storage systems due to their high theoretical capacity (1675 mAh g−1) and high energy density (2600 Wh kg−1). However, the application of Li−S batteries is currently restricted due to the dissolution of polysulfides in the electrolyte, which leads to the shuttle effect of lithium polysulfides (LiPSs). Here, we present a Co@MXene‐derived TiO2 heterostructure decorated on carbon sheets derived from folic acid (Co@M‐TiO2/C) as a functional separator coating to trap polysulfide and accelerate redox kinetics in Li−S batteries. The interconnected porous structure with good electrical conductivity of the heterostructure boasts rapid ion diffusion and efficient electron transfer within the battery. By attaching Co and MXene‐derived dual‐phased TiO2 to two‐dimensional carbon sheets, heterostructures are formed, ensuring complete exposure of the active sites. These heterostructures exhibit catalytic effects on LiPSs and excellent adsorption capabilities, effectively inhibiting the shuttle effect and accelerating the redox kinetics. Considering these advantages, the Li−S battery with the optimized Co@M‐TiO2/C modified separator demonstrates a high specific capacity of 1481.7 mAh g−1 at 0.2 C, superior rate performance of 855.5 mAh g−1 at 2 C, and excellent cycling performance under a high sulfur load of 4.4 mg cm−2. [ABSTRACT FROM AUTHOR]

Room temperature sodium sulfur (RT Na‐S) batteries with high theoretical energy density and low cost have recently gained extensive attention for potential large‐scale energy storage applications. However, the shuttle effect of sodium polysulfides is still the main challenge that leads to poor cycling stability, which hinders the practical application of RT Na‐S batteries. Herein, a multifunctional hybrid MXene interlayer is designed to stabilize the cycling performance of RT Na‐S batteries. The hybrid MXene interlayer comprises a large‐sized Ti3C2Tx nanosheets inner layer followed by a small‐sized Mo2Ti2C3Tx nanoflake outer layer on the surface of the glass fiber (GF) separator. The large‐sized Ti3C2Tx nanosheet inner layer provides an effective physical block and chemical confinement for the soluble polysulfides. The small‐sized Mo2Ti2C3Tx outer layer offers an excellent polysulfide trapping capability and accelerates the reaction kinetics of polysulfide conversion, due to its superior electronic conductivity, large specific surface area, and Mo‐rich catalytic surfaces. As a result, RT Na‐S batteries with this hybrid MXene interlayer modified glass fiber separator deliver a stable cycling performance over 200 cycles at 1 C with an enhanced capacity retention of 71%. This unique structure design provides a novel strategy to develop 2D material‐based functional interlayer for high‐performance metal‐sulfur batteries. [ABSTRACT FROM AUTHOR]

It is vital to dynamically regulate S activity to achieve efficient and stable room‐temperature sodium–sulfur (RT/Na−S) batteries. Herein, we report using cobalt sulfide as an electron reservoir to enhance the activity of sulfur cathodes, and simultaneously combining with cobalt single atoms as double‐end binding sites for a stable S conversion process. The rationally constructed CoS2 electron reservoir enables the straight reduction of S to short‐chain sodium polysulfides (Na2S4) via a streamlined redox path through electron transfer. Meanwhile, cobalt single atoms synergistically work with the electron reservoir to reinforce the streamlined redox path, which immobilize in situ formed long‐chain products and catalyze their conversion, thus realizing high S utilization and sustainable cycling stability. The as‐developed sulfur cathodes exhibit a superior rate performance of 443 mAh g−1 at 5 A g−1 with a high cycling capacity retention of 80 % after 5000 cycles at 5 A g−1. [ABSTRACT FROM AUTHOR]

Sodium and sulfur offer a promising application in rechargeable batteries due to their low cost, abundant resources and high energy density. Room‐temperature (RT) Na–S batteries have been proposed by paring S cathodes with Na anodes in non‐aqueous liquid electrolytes. Over decades, researchers have mainly focussed on the development of superior electrodes by nano‐engineering efficient S cathodes and stable Na anodes. These studies have effectively improved the electrochemical performance of RT Na–S batteries, validating their bright prospects as stationary energy storage devices for the modern renewable energy trajectory. In comparison, the research on electrolytes receives much less attention, and there is a lack of understanding regarding the impacts of different electrolytes on electrode interfaces and overall battery mechanisms. In this review, multiple‐kinds of electrolytes and the interfaces between electrolytes and electrodes in RT Na–S batteries are comprehensively discussed. Challenges and recent progress are presented in terms of the sulfur electrochemical mechanisms: The solid‐solid and solid‐liquid conversions. With the presentation of the S redox mechanism, future prospects of electrolyte optimizations, cathode, and anode as well as interfacial improvement are systematically discussed. [ABSTRACT FROM AUTHOR]

Room‐temperature sodium–sulfur (RT Na–S) batteries have attracted extensive attention because of their low cost and high specific energy. RT Na–S batteries, however, usually suffer from sluggish reaction kinetics, low reversible capacity, and short lifespans. Herein, it is shown that chain‐mail catalysts, consisting of porous nitrogen doped carbon nanofibers (PCNFs) encapsulating Co nanoparticles (Co@PCNFs), can activate sulfur via electron engineering. The chain‐mail catalysts Co@PCNFs with a micrograde hierarchical structure as a freestanding sulfur cathode (Co@PCNFs/S) can provide space for high mass loading of sulfur and polysulfides. The electrons can rapidly transfer from chain‐mail catalysts to sulfur and polysulfides during discharge–charge processes, therefore boosting its conversion kinetics. As a result, this freestanding Co@PCNFs/S cathode achieves a high sulfur loading of 2.1 ± 0.2 mg cm−2, delivering a high reversible capacity of 398 mA h g−1 at 0.5 C (1 C = 1675 mA g−1) over 600 cycles and superior rate capability of an average capacity of 240 mA h g−1 at 5 C. Experimental results, combined with density functional theory calculations, demonstrate that the Co@PCNFs/S can efficiently improve the conversion kinetics between the polysulfides and Na2S via transferring electrons from Co to them, thereby realizing efficient sulfur redox reactions. [ABSTRACT FROM AUTHOR]

Lithium sulfide (Li 2 S) is a promising cathode material with a high theoretical capacity (1166 mA h g−1) that can be paired with nonlithium-metal anodes, which can eliminate the safety issue related with lithium anode. Nevertheless, its poor electronic conductivity and low Li ion diffusion lead to the high activation barrier of Li 2 S and sluggish kinetic conversion to polysulfides, hindering its commercialization. Herein, Li 2 S particles coated by Co nanomaterial-decorated porous carbon shells (Li 2 S/Co@C) are catalytically synthesized in-situ as the Li 2 S-Co heterostructures to enhance Li 2 S reactivity and its kinetic conversion via a carbothermic reduction. This Li 2 S/Co@C shows an ultra-low activation potential of 3.12 V, smaller by 0.74 V compared with commercial Li 2 S. Significantly, it presents an initial reversible capacity of 1006 mA h g−1 and maintains a high reversible capacity of 335 mA h g−1 at 0.1 C (1 C = 1166 mA g−1) after 500 cycles. An outstanding rate capacity is also achieved with a reversible capacity of 148 mA h g−1 at 3 C. More importantly, in-/ex - situ characterizations underscore that Co nanomaterials can serve as an Li 2 S-Co heterostructure catalyst to enhance the reactivity of Li 2 S, lithium polysulfides, and sulfur, thereby achieving high performance in Li-S batteries. [ABSTRACT FROM AUTHOR]