Modulating p-d orbital hybridization by CuO/Cu nanoparticles enables carbon nanofibers high cycling stability as anode for sodium storage

Carbon nanofibers (CNFs) have been extensively studied as anode materials for sodium-ion batteries due to their high conductivity, large aspect ratio and good electrochemical stability. The low specific capacity and low first cycle efficiency of CNFs, however, have hindered its practical application. Herein, we present a facile strategy to synthesize a novel CNFs decorated with Cu/CuO nanoparticles (Cu-CNFs) using magnetron sputtering method. Cu/CuO nanoparticles were uniformly distributed on the surface of CNFs. According to the density functional theory (DFT) calculation, Cu/CuO nanoparticles d-orbitals and CNFs p-orbitals present hybridization states, and the Na + adsorption energy of the modified CNFs decreases from − 2.14 to − 2.97 eV. The Cu-CNFs composites exhibit excellent sodium storage properties, presenting a desirable initial Coulombic efficiency of 76% and a high specific reversible capacity of 300 mAh·g −1 at 0.1 A·g −1 after 400 cycles. Cu-CNFs anode has excellent cycling stability under high current density, maintaining a high capacity of 150 mAh·g −1 at 1 A·g −1 after 6000 cycles. Using magnetron sputtering to regulate the electronic structure provides a new thought for improving the electrochemical performance of carbon materials. Graphical abstract