Hongjie Peng1 Jiaqi Huang1 Qiang Zhang1

1, Tsinghua University, Beijing, , China

Lithium–sulfur (Li–S) battery is one of the most promising candidates for next-generation secondary batteries. However, the practical application of Li–S battery is hindered by many scientific and technical obstacles. Many of them originate from the well-known shuttle effect induced by lithium polysulfides (LiPSs). LiPSs, as naturally produced intermediates, are prone to dissolve in organic electrolytes. Their polar nature prevents not only effective entrapment of LiPSs within the cathode but also efficient charge transfer between them and conductive scaffolds, which are normally nonpolar carbon. Thus, one of the most formidable challenges is the sluggish kinetics of LiPS redox reactions, which further results in low sulfur utilization and capacity fading.

To overcome the challenge, rational design of sulfur hosts emerges as one of the most effective approaches, which simultaneously enables strong LiPS adsorption, fast interfacial charge transfer, enhanced electrochemical kinetics, and/or efficient electrocatalysis. In this contribution, we start with a concept of self-healing Li–S batteries, by which the underlying mechanism based on solution–solid nucleation/growth theory and its correlation to spatial homogeneity of LiPS concentration are revealed. Guided by this understanding, we demonstrate a variety of nanocarbon (i.e., graphene and carbon nanotubes)-supported hybrid materials, including transition metal carbides, borates, hydroxides, and sulfides, as well as nanostructured polymer, to realize fast LiPS redox reactions and controlled nucleation/growth of solid products. These rationally designed sulfur hosts render Li–S batteries with superb electrochemical performance. We believe that the understanding of LiPS-involving reactions and design principles will create considerable opportunities to develop high-performance Li–S batteries.

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