Novel synthesis of CoS/C composite as an anode material for Li-ion batteries

Abstract

In this study, cobalt sulfide/carbon nanocomposites were successfully synthesized via a temperature-controlled pyrolysis method using cobalt salt and thiourea as precursors. The results demonstrate that the calcination temperature plays a key role in governing the phase structure and lithium-storage performance of the resulting materials. At a calcination temperature of 550 °C (sample CS-550), a cubic CoS₂ phase coexists with partially decomposed g-C₃N₄. Meanwhile, at 630 °C (sample CS-630), the material completely transforms into a highly crystalline hexagonal CoS phase encapsulated by a highly conductive graphitized carbon shell. The CS-630 electrode exhibits superiority over CS-550 in terms of both electrochemical kinetics and mechanical durability during the lithiation/delithiation processes. Specifically, CS-630 delivers a stable discharge capacity of approximately 358.51 mAh g^-1 after 200 cycles, which is higher than that of CS-550 (only ~69.64 mAh g^-1 after 180 cycles). Furthermore, the CS-630 anode possesses lower charge-transfer resistance, enhanced Li⁺ ion diffusion capabilities compared to CS-550. This superior performance is credited to the robust hexagonal CoS framework synergized with the conductive carbon network, which effectively accelerates electrochemical kinetics and buffers the volumetric strain induced during cycling. This work underscores that tailoring the calcination temperature is an effective strategy for enhancing the performance of cobalt sulfide anodes in lithium-ion batteries.