Coral‐like cobalt selenide/carbon nanosheet arrays attached on carbon nanofibers for high‐rate sodium‐ion storage

Abstract Cobalt selenide (CoSe 2 ) has become a promising anode material for sodium‐ion batteries (SIBs) due to its stable chemical properties, environmental friendliness, and high theoretical capacity. However, the undesirable rate capacity and cycle stability of the anode materials largely limit its applications for SIBs due to the relatively low electronic conductivity and huge volume change during the Na + insertion/extraction. In this study, electrostatic spinning combined with a wet chemical method is employed to synthesize coral‐like composite material (CNF@c‐CoSe 2 /C), which is composed of CoSe 2 /carbon nanosheet arrays (CoSe 2 /C) and carbon nanofibers (CNFs). CoSe 2 /C nanoflakes derived from metal‐organic frameworks (MOFs) with high surface area and the porous structure can inhibit the pulverization and amorphization of CoSe 2 during charge and discharge processes, thus significantly keeping the stability of the microstructure. CNF can limit the overgrowth of nanosheets and serve as a conductive skeleton. Compared to two‐dimensional CoSe 2 /C nanoflakes and pure CoSe 2 nanoparticles, the composite can expose more active sites and effectively accelerate the diffusion of Na + , which displays enhanced rate capability (266.5 mAh·g −1 at 5.0 A·g −1 ) and cycling stability (268.3 mAh·g −1 after 100 cycles at 1.0 A·g −1 ). Moreover, the rational preparation strategy for metal selenide‐based heterostructure material presents a new way for high‐performance SIBs.