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

摘要

The amorphous metal boride materials are attractive catalyst for advancedlithium sulfur batteries, but their catalytic mechanism remains unclear.Herein, 2D amorphous Mo-doped cobalt boride (Co_7Mo_3B) is designed forthe first time as bidirectional sulfur catalysis by rapid chemical reduction.The atom cluster structure of Co_7Mo_3B is revealed by theoretical calculation.Electron paramagnetic resonance test further confirms that Co_7Mo_3B hasinterstitial compound structure characteristics. Experimental results showthat the porous 2D nanosheets structure and the interaction of Mo, B,Co atoms contribute to enhanced conductivity, high long-chain lithiumpolysulfides affinity, and reversible Li_2S nucleation and dissociation, thusaccelerating LiPSs reduction and Li2S oxidation kinetics. In addition, theinterstitial Co_7Mo_3B enables intercalation of Li and B during charging–discharging while keeping the structure stable. As a result, the S cathodewith Co_7Mo_3B catalyst delivers good life (1000 cycles at 5 C), superior rateperformance (10 C). Even at high sulfur areal loading of 6.79 mg cm~(–2) andelectrolyte/sulfur ratio of 5 μL mg~(–1), the Co_7Mo_3B/S composite cathode stillexhibits good areal capacity and capacity retention rate.