Lithium-sulfur batteries are recognized as one of the most promising next-generation energy storage devices, owing to the high theoretical energy density of 2600 Wh·kg^-1. However, their application has been seriously hindered by the sluggish electrochemical reaction kinetics of elemental sulfur and discharged products (Li₂S₂/Li₂S), and the notorious “shuttle effect” of soluble intermediate lithium polysulfide species, leading to poor cycle stability, low sulfur utilization and inferior coulombic efficiency. Introducing catalytic hosts into sulfur cathode is an efficient path to propel the conversion of sulfur-contained species, thus preventing the dissolution and loss of active-sulfur material in lithium-sulfur batteries. In this review, we summarize recent progresses on the uses of metals and alloys as the core catalytic host of sulfur, and demonstrate the catalytic mechanism in the conversion process of sulfur species with the help of metal and alloy hosts. Finally, future outlooks are proposed on the construction of catalytic hosts and the development of high-energy lithium-sulfur batteries.

Lithium-sulfur (Li-S) battery is one of the promising energy storage devices because of its high energy density. However, the sulfur cathode suffers from sluggish electrochemical reaction kinetics, slow charge transfer, large volume expansion and severe shuttle effect of lithium polysulfides inevitably resulting in low reversible capacity, poor rate performance and short cycle life, limiting its practical applications. Herein, the recent progress of cobalt/carbon composites, including cobalt nanoparticles and cobalt single atoms, as the sulfur host materials in Li-S batteries is overviewed. In general, cobalt plays the role of electrocatalyst, which inhibits the shuttle effect of lithium polysulfides, accelerates the electrochemical reaction kinetics, facilitates ion/electron transfer and alleviates volume expansion. Meanwhile, the prospects for the development of cobalt/carbon composites as sulfur hosts in Li-S batteries are proposed. It is expected to offer a whole blueprint and constructive suggestions for the cobalt/carbon composites as sulfur hosts for Li-S batteries, and these strategies can also be effective for other metal-sulfur batteries.

Lithium-sulfur (Li-S) batteries show attractive prospects owing to their high theoretical energy density, but their commercialization still faces such challenges as lithium polysulfides shuttling, severe volume change and considerable polarization. These stubborn issues place higher demands on each component in the battery, such as the development of multifunctional binders with superior mechanical properties. Herein, ethoxylated trimethylolpropane triacrylate was firstly introduced into sulfur cathodes, and in-situ cross-linked by ultraviolet (UV) curing combined with traditional polyvinylidene difluoride binder (i.e., forming a binary binder, denoted as c-ETPTA/PVDF) to construct high-loading and durable Li-S batteries. The covalently cross-linked ETPTA framework not only significantly enhances the mechanical strength of the laminate, but also offers a strong chemical affinity for lithium polysulfides due to the abundant oxygen-containing groups. Moreover, the moderate interaction force between ether oxygen bonds and Li⁺ further accelerates the Li⁺ transport. As such, the S-c-ETPTA/PVDF electrode exhibited an ultralow attenuation rate of 0.038% at 2 C over 1000 cycles. Even under a sulfur loading of 7.8 mg_S·cm^-2, an average areal capacity of 6.2 mAh·cm^-2 could be achieved after 50 cycles. This work indicates that light-assisted curing technology holds great promise in the fabrication of robust and high-energy-density Li-S batteries.

Lithium-sulfur (Li-S) batteries have become one of the most promising next-generation battery systems due to their high energy density and low cost. However, the application of Li-S batteries still faces critical challenges, such as the low conductivities of S and Li₂S, shuttle effect of polysulfides and dendrite growth of Li, etc. The optimization of the electrolyte can ameliorate the electrolyte|electrode interphase, conveniently regulating the parasitic reaction and improving the performance of the resultant batteries. The functional additives in electrolytes provide chances to tune the interphase and even the redox mechanism to improve the performance of the batteries. In this review, we systematically summarize the latest progresses of additives for Li-S batteries. The additives are classified according to the category that lies on the protection of Li metal anode or the stabilization of S cathode. The functions of additives on the S cathode such as the inhibitions of dissolution and shuttle of the polysulfides, the redox mediators, and the activation of Li₂S deposits are discussed in detail. Finally, the prospects of additives for Li-S batteries are supplied in brief. We hope that the review can provide a guidance in the design of electrolyte for high-performance Li-S batteries.