The commercial application of lithium-sulfur batteries (LSB) is still limited by the irreversible capacity fading caused by the shuttle of lithium polysulfides (LIPS). To address this issue, a bimetal (nickel, cobalt)-organic framework (MOF) derived carbon, (Ni, Co)/C, was prepared to modify the separator. The multifunctionally modified separator effectively captures LIPS, ensuring the stability and reversibility of sulfur fixation, while providing catalytic activity and improving ionic conductivity. The cobalt metal has a larger coordination number, more pore structure distribution, larger specific surface area, more surface C=O, and smaller particle size to achieve a large and rapid chemical sulfur fixation. The high conductivity provided by nickel, and the catalytic activity and the ability to block LIPS shuttling enabled the reversibility of sulfur inhibition. The synergistic effect of cobalt-nickel bimetals significantly improves the cycling stability and rate capability of LSB. At a current density of 1 C, the capacity of the (Ni, Co)/C modified separator battery could reach 1035.6 mAh·g^-1 in the first cycle, the capacity remained at 662.2 mAh·g^-1 after 500 cycles, and the capacity retention rate was 63.9%.

Practical applications of lithium-sulfur (Li-S) batteries are hindered mainly by the low sulfur utilization and severe capacity fading derived from the polysulfide shuttling. Catalysis is an effective remedy to those problems by promoting the conversion of polysulfides to reduce their accumulation in the electrolyte, which needs the catalyst to have efficient adsorption ability to soluble polysulfides and high activity for their conversion. In this work, we have proposed a bimetallic compound of NiCo₂S₄ anchored onto sulfur-doped graphene (NCS@SG) to fabricate a catalytic interlayer for Li-S batteries. Compared to CoS, the NiCo₂S₄ demonstrated much higher catalytic activity toward sulfur reduction reaction due to its multiple anchoring and catalytic active sites derived from the coordination of the bimetallic centers. As a result, the NCS@SG interlayer dramatically improved the specific capacity, rate performance, and cycling stability of Li-S batteries. Especially, when the areal sulfur loading of the NCS@SG battery increased to 15.3 mg·cm^-2, the high-capacity retention of 93.9 % could be achieved over 50 cycles.

All solid-state lithium-sulfur batteries (ASSLSBs) are considered to be one of the most promising next-generation energy storage systems, due to the promises of high energy density and safety. Although the use of solid-state electrolytes could effectively suppress the "shuttle effect" and self-discharge of the conventional liquid lithium-sulfur (Li-S) battery, the commercialization of ASSLSBs has been seriously hampered by the electrolyte degradation, electrode/electrolyte interfacial deterioration, electrochemo-mechanical failure, lithium dendrite growth and electrode pulverization, etc. This paper provides a comprehensive review of recent research progresses on the solid-state electrolytes, sulfur-containing composite cathodes, lithium metal and lithium alloy anodes, and electrode/electrolyte interfaces in ASSLSBs. Specifically, lithium sulfide and metal sulfide as new active cathode materials, and lithium alloy as new anode materials are overviewed and analyzed. In addition, some newly developed interfacial modification strategies for addressing the electrode/electrolyte interfacial challenges are also outlined. Furthermore, an outlook on the future research and development of high-performance ASSLSBs are also presented.

Lithium-sulfur (Li-S) batteries attract sustained attention because of their ultrahigh theoretical energy density of 2567 Wh·kg^-1 and the actual value over 600 Wh·kg^-1. Solid-state Li-S batteries (SSLSBs) emerge in the recent two decades because of the enhanced safety when compared to the liquid system. As for the SSLSBs, except for the difference in the conversion mechanism induced by the cathode materials themselves, the physical-chemical property of solid electrolytes (SEs) also significantly affects their electrochemical behaviors. On account of various reported Li-S batteries, the advantages and disadvantages in performance and the failure mechanism are discussed in this review. Based on the problems of the reported SSLSBs such as lower energy density and faster capacity fading, the strategies of building high-performance SSLSBs are classified. The review aims to afford fundamental understanding on the conversion mechanism of sulfur and engineering design at full-cell level, so as to promote the development of SSLSBs.