Modulating the p-band center of carbon nanofibers derived from Co spin state as anode for high-power sodium storage

Carbon nanofibers(CNFs)have received extensive and in-depth studied as anodes for sodium-ion batteries(SIBs),and yet their initial Coulombic efficiency and rate capability remain enormous challenge at practical level.Herein,CNFs anchored with cobalt nanocluster(CNFs-Co)were prepared using chemical vapor deposition and thermal reduction methods.The as-prepared CNFs-Co shows a high initial Coulombic efficiency of 91%and a high specific discharge capacity of 246 mAh/g at 0.1 A/g after 200 cycles as anode for SIBs.Meanwhile,the CNFs-Co anode still delivers a high cycling stability with 108 mAh/g after 1000 cycles at 10 A/g.These excellent electrochemical properties could be attributed to the involved spin state Co,which endows CNFs with large interplanar spacing(0.39 nm)and abundant vacancy defects.Importantly,the spin state Co downshifts the p-band center of carbon and strengthens the Na+adsorption energy from-2.33 eV to-2.64 eV based on density functional theory calculation.This novel strategy of modulating the carbon electronic structure by the spin state of magnetic metals provides a reference for the development of high-performance carbon-based anode materials.