Nitrogen, Oxygen-Codoped Vertical Graphene Arrays Coated 3D Flexible Carbon Nanofibers with High Silicon Content as an Ultrastable Anode for Superior Lithium Storage.

Free-standing and foldable electrodes with high energy density and long lifespan have recently elicited attention on the development of lithium-ion batteries (LIBs) for flexible electronic devices. However, both low energy density and slow kinetics in cycling impede their practical applications. In this work, a free-standing and binder-free N, O-codoped 3D vertical graphene carbon nanofibers electrode with ultra-high silicon content (VGAs@Si@CNFs) is developed via electrospinning, subsequent thermal treatment, and chemical vapor deposition processes. The as-prepared VGAs@Si@CNFs electrode exhibits excellent conductivity and flexibility because of the high graphitized carbon nanofiber network and abundant vertical graphene arrays. Such 3D all-carbon architecture can be fabulous for providing a conductive and mechanically robust network, further improving the kinetics and restraining the volume expansion of Si NPs, especially with an ultra-high Si content (>90 wt%). As a result, the VGAs@Si@CNFs composite demonstrates a superior specific capacity (3619.5 mAh g at 0.05 A g ), ultralong lifespan, and outstanding rate capability (1093.1 mAh g after 1500 cycles at 8 A g ) as a free-standing anode for LIBs. It is believed that this work offers an exciting method for developing free-standing and high-energy-density electrodes for other energy storage devices.