Self-templated synthesis of Co9S8@C nanosheets for high-performance sodium-ion batteries
摘要
Co9S8 has gained widespread recognition as a potential anode material for sodium-ion batteries (SIBs) due to its excellent theoretical capacity and economic viability. Nevertheless, the significant volume expansion, insufficient electron conductivity, and sluggish sodium ion transport kinetics of Co9S8 restrict its further practical application of SIBs. Herein, a novel composite of Co9S8@C nanosheets has been successfully synthesized via a self-template strategy combined with a subsequent multi-step phase transformation process. The Co9S8@C nanosheets comprise a heterostructure featuring ultrafine Co9S8 nanoparticles uniformly encapsulated in carbon nanosheets, which effectively mitigates the large volume expansion and aggregation of Co9S8 nanoparticles during electrochemical processes. When tested as anode material for SIBs, the Co9S8@C nanosheets exhibit a high reversible capacity of 631.8 mAh g−1 at 0.1 A g−1, outstanding rate capability (529.8 mAh g−1 at 5 A g−1), and exceptional cycle stability (with a capacity retention of 81.1% at 1 A g−1 and 85.9% at 10 A g−1 after 1000 cycles). Density functional theory (DFT) calculations reveal that the incorporation of carbon not only significantly enhances the Na+ absorption and Na+ diffusion kinetics, but also facilitates electron transfer. This work provides a viable approach to construct Co9S8@C nanosheets toward high-performance SIBs.