Cu-supported nitrogen-doped carbon nanofibers with hierarchical three-dimensional net structure as binder-free anodes for enhanced lithium-ion batteries.

Cu-supported nitrogen-doped carbon nanofibers (NCNFs) were fabricated via electrospinning and subsequent activation treatment with poly vinylpyrrolidone as both carbon and nitrogen sources. The NCNFs are firmly adhered to Cu foil without any additional binder and form a hierarchical three-dimensional net structure, which could effectively shorten the diffusion paths for electrons and lithium ions, thus resulting in lower impedance and superior electrochemical properties. Additionally, NCNFs feature a amorphous carbon structure, N-rich carbon lattice and wide pore distribution, not only ensuring fast ions/electrons transport, but also giving rise to the higher energy density. When directly used as a binder-free electrode, NCNFs deliver a high reversible capacity of 617.8 mAh g at 200 mA g after 100 cycles and maintain a superior capacity of 274.1 mAh g at 1.44 A g even after 500 cycles. Besides, the reversible capacity up to 216.5 mAh g can be still obtained at a high current density of 6 A g, demonstrating the excellent high-rate cyclability. The facile synthesis approach and superior electrochemical properties make NCNFs electrodes an alternative anode candidate for lithium-ion batteries.