2D Amorphous Mo-Doped CoB for Bidirectional Sulfur Catalysis in Lithium Sulfur Batteries

The amorphous metal boride materials are attractive catalyst for advanced lithium sulfur batteries, but their catalytic mechanism remains unclear. Herein, 2D amorphous Mo-doped cobalt boride (Co₇Mo₃B) is designed for the first time as bidirectional sulfur catalysis by rapid chemical reduction. The atom cluster structure of Co₇Mo₃B is revealed by theoretical calculation. Electron paramagnetic resonance test further confirms that Co₇Mo₃B has interstitial compound structure characteristics. Experimental results show that the porous 2D nanosheets structure and the interaction of Mo, B, Co atoms contribute to enhanced conductivity, high long-chain lithium polysulfides affinity, and reversible Li₂S nucleation and dissociation, thus accelerating LiPSs reduction and Li₂S oxidation kinetics. In addition, the interstitial Co₇Mo₃B enables intercalation of Li and B during charging–discharging while keeping the structure stable. As a result, the S cathode with Co₇Mo₃B catalyst delivers good life (1000 cycles at 5 C), superior rate performance (10 C). Even at high sulfur areal loading of 6.79 mg cm^–2 and electrolyte/sulfur ratio of 5 μL mg^–1, the Co₇Mo₃B/S composite cathode still exhibits good areal capacity and capacity retention rate.