Intercalated Co(OH)2-derived flower-like hybrids composed of cobalt sulfide nanoparticles partially embedded in nitrogen-doped carbon nanosheets with superior lithium storage

Abstract

Cobalt sulfides are considered as one of the most promising alternative anode materials for high-performance lithium-ion batteries by virtue of their remarkable electrical conductivity and high theoretical capacity. However, the volume expansion of cobalt sulfides and polysulfide shuttling effect during the discharge/charge process result in a poor cycling stability and low rate capability. Herein, we report the designed synthesis of a flower-like structure, including cobalt sulfide nanoparticles with a small particle size partially embedded within the nitrogen-doped carbon nanosheets and few-layer graphene covering the external surface of cobalt sulfides (Co₉S₈/Co_1−xS@NC), by simultaneous decomposition and sulfidation of a metanilic anion intercalated Co(OH)₂ precursor. Through adjusting the annealed temperature and the mass ratio of the precursor and S powders, the composition of cobalt sulfides could be easily controlled. Co₉S₈/Co_1−xS@NC prepared under optimized conditions exhibits a high reversible capacity of 1230 mA h g⁻¹ after 110 cycles, excellent rate capability (≈1016, 979, 931, 813 mA h g⁻¹ at the current densities of 200, 500, 1000, and 2000 mA g⁻¹, respectively), and stable cycling performance (≈98.4% capacity retention after 110 cycles). Significantly, this intercalated Co(OH)₂-derived strategy can be expanded to the preparation of other metal sulfides and carbon composites for application in other energy conversion and storage devices.