CoS2 nanoparticles encapsulation promotes stable MoS2@CoS2@CNFs heterostructure and durable sodium-ion storage

Abstract

Layered MoS2 are promising anode materials due to the applicable interlayer spacing (0.62 nm) and high theoretical specific capacity (669mAh g−1). Nevertheless, the low electric conductivity, large structure variation and sluggish ionic kinetics result in rapid capacity decay and suboptimal cycle performance of MoS2-based sodium-ion batteries (SIBs). Here, the two-step methodology was used to grow MoS2 sheets on the surface of N-doped carbon fibers with CoS2 nanoparticles encapsulated in. The obtained MoS2@CoS2@CNFs exhibit a distinctive hierarchical structure, which increases the electrode-electrolyte interface, thereby minimizing the diffusion distance of Na+. Experiment and calculation results demonstrates that the incorporation of CoS2 not only enhances the ion mobility and pseudocapacitance contribution of the electrode material, but also amplifies its conductivity and adsorption energy of Na+, ultimately elevating the rate performance and ensuring long cycle stability of SIBs. Consequently, the MoS2@CoS2@CNFs composite enabled a commendable capacity of 494.5 mAh g−1 after 700 cycles at 0.5 A g−1. Impressively, when the current density was increased to 2 A g−1, it reserved a capacity of 310 mAh g−1 for 2000 cycles. To encapsulation of CoS2 nanoparticles in the MoS2@CoS2@CNFs composite promotes the stability of the anodes and boosts durable Na+ storage, making it a promising method for designing high performance SIBs.