Accelerating lithium storage capability of cobalt sulfide encapsulated within anion dual-doped mesoporous carbon nanofibers

Metal sulfide materials are promising for the anodes of ultrafast lithium ion batteries (LIBs) for many potential high-technology devices because of their high electrical conductivity, high theoretical capacity, and chemical/electrochemical stability resulting from their unique crystal structures. Despite their significant advantages, these materials face an important challenge related to structural degradation, owing to the significant volume expansion of metal sulfide under ultrafast cycling conditions. This phenomenon leads to rapid capacity fading and must be improved for the practical application of ultrafast LIBs. In the present study, a unique architecture of cobalt sulfide encapsulated within anion dual (nitrogen and sulfur)-doped mesoporous carbon nanofibers (referred to as CoS-NS-PCNF) was fabricated via electrospinning and carbonization. The CoS-NS-PCNF exhibited superb ultrafast cycling performance including outstanding cycling stability (748.6 mAh g⁻¹ with capacity retention of 96.5% at 100 mA g⁻¹ after 100 cycles), a superb ultrafast cycling capacity (550.1 mAh g⁻¹ at 2000 mA g⁻¹), and excellent ultrafast cycling stability (514.6 mAh g⁻¹ with capacity retention of 93.5% at 2000 mA g⁻¹ after 500 cycles). Thus, the novel architecture has significant advantages for ultrafast lithium storage kinetics including a short lithium-ion diffusion length, a high ion/electron transfer rate, and effective prevention of volume expansion.