Integrating Sub-Nano Catalysts into Metal-Organic Framework toward Pore-Confined Polysulfides Conversion in Lithium-Sulfur Batteries

Shuttle effect and sluggish redox kinetics of sulfur species still hinder the practical application of lithium-sulfur batteries (LSBs). Herein, a strategy of integrating sub-nano catalysts into metal-organic framework (MOF) is proposed for developing efficient sulfur host to tackle these issues. The designed MOF host (MOF-TOC) endowed with sub-nano Ti-O clusters (TOCs) in the mesopores of MOF can act as an efficient reaction chamber in LSBs. Systematic electrochemical measurements and calculations demonstrate that MOF-TOC can trap and confine lithium polysulfides (LiPSs) via strong chemical interaction. Moreover, the highly active TOCs isolated in different nanopores can accelerate the bidirectional redox reaction of sulfur species through the d-p orbital hybridization with sulfur species. Benefiting from these merits, MOF-TOC delivers LSBs with remarkably improved areal capacity and cycling stability at high sulfur loadings and lean electrolytes. This work gives insight into the rational design of catalyst-containing MOF hosts and will shed light on the development of advanced catalytic hosts for high-performance LSBs.