Cobalt nitride nanoparticle coated hollow carbon spheres with nitrogen vacancies as an electrocatalyst for lithium–sulfur batteries

Abstract

The development of high-capacity rechargeable lithium–sulfur batteries is an ongoing challenge because of the shuttle effect, which causes rapid capacity fade, limited rate capability, and slow kinetics. Herein, conductive hollow cobalt nitride/carbon (Co_5.47N_x–C) spheres with nitrogen vacancies are developed as a high-performance cathode material for use in lithium–sulfur batteries. Nitrogen vacancies are formed by annealing a zeolite imidazole framework (ZIF-67) precursor in ammonia. Benefiting from its Co–N bonds and nitrogen-vacancy sites, the Co_5.47N_x–C composite achieves strong anchoring of polysulfides, fast polysulfide conversion, and accelerated lithium-ion transport. The strong anchoring effect of Co_5.47N_x is confirmed by experimental measurements and density functional theory (DFT) calculations. Because of its high conductivity and nitrogen vacancies, the Co_5.47N_x cathode exhibits faster redox reaction kinetics and lower polarization than a Co_5.47N cathode without nitrogen vacancies, thus realizing promising rate and cycling performance. The optimized Co_5.47N_x–C electrode delivers a capacity of 850 mA h g⁻¹ at 0.5C and a rate performance of 320 mA h g⁻¹ at 10C. This high-performance, high-rate lithium–sulfur battery is promising for widespread application in electric vehicles and intelligent devices.