Chromium and molybdenum dual-metal nanoclusters: synergistic catalysis of sulfur redox for high performance Li–S batteries

Abstract

The practical applications of lithium–sulfur (Li–S) batteries are currently hindered by several obstacles, including the shuttle effect of lithium polysulfides (LiPSs) and the sluggish kinetics of sulfur redox reactions, especially the conversion of liquid LiPSs to solid Li₂S, which results in limited specific capacity and dramatic cyclic cycling capacity decay. To alleviate these limitations, a novel catalyst consisting of chromium and molybdenum transition metal nanoclusters embedded in nitrogen-doped graphene (Cr/Mo@N-C) is reported in this work. When this catalyst is used for Li–S batteries, the nitrogen-doped graphene provides strong adsorption sites for long-chain LiPSs; meanwhile, the Cr and Mo nanoclusters are segmented to facilitate the subsequent redox reactions: the Cr nanocluster governs the reversible phase transitions between elemental sulfur (S) and long-chain LiPSs and the Mo nanocluster expedites the reduction kinetics between short-chain LiPSs and solid Li₂S. As a result, Li–S batteries with this catalyst deliver exceptional electrochemical performance, achieving a specific capacity of 1431 mAh g⁻¹ at 0.1C, which is more than 85% of the theoretical capacity, and sustaining superior rate capabilities of 704 mAh g⁻¹ at 5C.