The discovery of interfacial electronic interaction within cobalt boride@MXene for high performance lithium-sulfur batteries

Lithium-sulfur battery is strongly considered as the most promising next-generation energy storage system because of the high theoretical specific capacity. The serious “shuttle effect” and sluggish reaction kinetic limited the commercial application of lithium-sulfur battery. Many heterostructures were applied to accelerate polysulfides conversion and suppress their migration in lithium-sulfur batteries. Nevertheless, the effect of the interface in heterostructure was not clear. Here, the Co₂B@MXene heterostructure is synthesized through chemical reactions at room temperature and employed as the interlayer material for Li-S batteries. The theoretical calculations and experimental results indicate that the interfacial electronic interaction of Co₂B@MXene induce the transfer of electrons from Co₂B to MXene, enhancing the catalytic ability and favoring fast redox kinetics of the polysulfides, and the theoretical calculations also reveal the underlying mechanisms for the electron transfer is that the two materials have different Fermi energy levels. The cell with Co₂B@MXene exhibits a high initial capacity of 1577 mAh/g at 0.1 C and an ultralow capacity decay of 0.0088% per cycle over 2000 cycles at 2 C. Even at 5.1 mg/cm² of sulfur loading, the cell with Co₂B@MXene delivers 5.2 mAh/cm² at 0.2 C.