Hierarchical porous carbon nanofibers with ultrasmall-sized cobalt disulfide/tungsten disulfide hybrid composites for high-rate lithium storage kinetics

Recently, transition metal dichalcogenides (TMDs) have attracted considerable attention as anode materials in ultrafast lithium ion batteries because of their high theoretical capacity and outstanding ion diffusion kinetics. Despite these remarkable properties, TMDs exhibit fast capacity fading and insufficient Li storage kinetics, owing to the excessive volume expansion and low electric/ionic transfer rate. The aim of this study is to reinforce the structural stability and Li storage kinetics of TMDs through the use of well-dispersed CoS₂ and WS₂ ultrasmall particles (USPs) embedded in hierarchical porous carbon nanofibers, including micro/mesoporous composite sturctures. As expected, this architecture offers a high specific capacity (718.0 mAh g⁻¹) with the capacity retention of 93.4% after 100 cycles at 0.1 A g⁻¹ owing to increased Li storage sites and prevention of volume expansion of CoS₂ and WS₂ USPs. In particular, a remarkable fast discharge capacity (444.5 mAh g⁻¹) with the capacity retention of 90.2% after 1000 cycles are noted. These results are related to the high number of Li ion storage sites, effective prevention of volume expansion of well-dispersed CoS₂ and WS₂ USPs, short Li ion diffusion length, and favorable Li ion acceptability, which is caused by the hierarchical porous structure containing meso/micropores.