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.