Lithium–sulfur (Li–S) battery is one of the promising energy storage systems due to its high theoretical energy density with low cost. The main challenge at present for its commercialization is the polysulfides shuttling, leading to poor cycling performance. Here, we report a facilely prepared metal-organic framework (MOF)-derived nanoporous carbon with embedded cobalt nanoparticles (NPCo/C) for alleviating the polysulfides shuttling. The NPCo/C with large surface area and abundant Co nanoparticles is simply prepared by direct carbonization of a Co-based MOF material, which is combined with graphene to construct a robust membrane as the interlayer (NPCo/C@G) to modify the pristine separator. The NPCo/C@G-modified separator gives the battery good cycling stability (707 mAh g−1 after 300 cycles at 0.5 C) and rate performance (capacity decay rate of 0.18% in 300 cycles at 2 C). Excellent battery performance (620 mAh g−1 after 100 cycles at 0.5 C) is exhibited even under ultra-low loading of NPCo/C@G (0.08 mg cm−2). The superior electrochemical performance is mainly attributed to abundant exposed Co active sites in NPCo/C to immobilize polysulfides and accelerate sulfur redox kinetics as well as excellent electrical conductivity of NPCo/C@G for improved sulfur utilization. This study provides a guidance for designing functional separators for Li–S battery application in the near future.
Li-S batteries are considered as promising energy storage devices for future applications due to the high theoretical energy density. The “shuttle effect” is a fundamental problem that limits the practical...
Owing to high theoretical energy density (2600 W h kg −1 ), a lithium−sulfur (Li−S) battery is considered as one of the most promising next-generation energy storage systems. The "shuttle effect" of soluble polysulfides brings a series of negative problems and seriously hinders its practical application. In this work, a mesoporous alumina (MA) with a large surface area (598 m 2 g −1 ) was combined with graphene (G) to construct a functional interlayer for separator coating in a Li−S battery to suppress the "shuttle effect". As demonstrated by DFT calculation and experimental investigation, the mesoporous structure and the large surface area of MA are beneficial to provide abundant exposed adsorption sites for polysulfides capture and meanwhile facilitate the migration of polysulfides to the conductive substrate surface for the electrochemical reaction conversion. The strong interaction between polysulfides and MA can reduce energy barriers of electrochemical polysulfide intermediate conversions, leading to enhanced sulfur redox reaction kinetics. The MA@G interlayer enables outstanding Li−S battery performance including large initial discharge capacity (1414 mA h g −1 at 0.5 C), good cycling stability (808 mA h g −1 at 0.5 C after 100 cycles), and rate performance (initial discharge capacity 1056 and 636 mA h g −1 after 300 cycles at 2 C). This work provides guidance for future design of functional separators for high-performance Li−S batteries.
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