Rational cooperativity of nanospace confinement and rapid catalysis via hollow carbon nanospheres@Nb-based inorganics for high-rate Li-S batteries

Abstract The sluggish redox kinetics and shuttling behaviors of intermediate polysulfides are dominant obstacles that hamper the practical applications of Li-S battery. In this work, two types of niobium (Nb)-based inorganics, semiconductive Nb2O5 and conductive NbC, are implanted into hollow carbon nanospheres (HCN) hosts, which can realize the cooperativity of nanospace confinement and high-efficiency catalytic Nb-based inorganics for high-rate Li-S batteries. The initial HCN have adequate hollow space achieving high sulfur loading, interpenetrated mesoporous channels for rapid ion transfer, and developed microporous carbon framework blocking the polysulfides shuttling. While Nb-based inorganics are uniformly located in the mesoporous channels, they can accelerate the conversion kinetics of the polysulfides by strong chemical interaction and high catalytic effect. Furthermore, we demonstrate that the conductive NbC performs much better catalytic activity than the Nb2O5, with significantly improved redox kinetic and cycling performance. The optimized HCN@NbC/S cathode delivers a preeminent reversible capacity of 500 mAh g−1 with a low capacity decay of 0.05% per cycle over 800 cycles at 3 C and a high rate capacity of 752 mAh g−1 under a high current density of 5 C. This work provides a novel strategy to construct desirable multifunctional host favoring cooperative polysulfides interactions via rational integration of physical confinement and high-effective catalytic inorganics for long-cycling stable sulfur cathode.