Controlled growth of Co9S8 nanoparticle-embedded carbon nanosheets/carbon nanofibers toward high-performance sodium storage

Transition metal sulfides (TMSs) are considered as promising anodes for sodium-ion batteries (SIBs) due to their high theoretical capacity and low cost. However, TMSs suffer from massive volume expansion, slow sodium-ion diffusion kinetics, and poor electrical conductivity, which severely restrict their practical application. Herein, we design self-supporting Co9S8 nanoparticles embedded carbon nanosheets/carbon nanofibers (Co9S8@CNSs/CNFs) as anode materials for SIBs. The electrospun carbon nanofibers (CNFs) provide continuous conductive networks to accelerate the ion and electron diffusion/transport kinetics, while MOFs-derived carbon nanosheets (CNSs) buffer the volume variation of Co9S8, consequently improving the cycle stability. Benefitting from the unique design and pseudocapacitive features, Co9S8@CNSs/CNFs deliver a stable capacity of 516 mAh g-1 at 200 mA g-1 and a reversible capacity of 313 mAh g-1 after 1500 cycles at 2 A g-1. Note that, it also displays excellent sodium storage performance when assembled into a full cell. The rational design and excellent electrochemical properties endow Co9S8@CNSs/CNFs with the potential stepping into commercial SIBs.