Encapsulating Nanoscale Silicon inside Carbon Fiber as Flexible Self-Supporting Anode Material for Lithium-Ion Battery

At present, the main limitations for the practical application of silicon (Si) as an anode material of a lithium-ion battery are huge volume variation and low electrical conductivity. Core–shell silicon/carbon (Si/C) composites can greatly relieve the Si large volume change and accelerate the low Li+ conductivity; however, cracking of carbon shell and the failure of the electrode structure still limit the lithium storage capability and cyclic life. Herein, a flexible freestanding N-doped core–shell Si/C nanofiber (SC-NF) anode is prepared by the double-nozzle electrospinning technique. It has been found that in such fibers, Si particles are encapsulated by the carbon shell of fibers, which can settle the shortcomings of pulverization and volume variation of Si. Furthermore, the highly conductive N–C shell derived from carbonized PAN can accelerate the diffusion of Li+ and charge transport. As a result, the as-prepared core–shell SC-NF-0.24 electrode exhibits an initial specific discharge capacity of 1441 mAh g–1 with a high capacity retention of 76.9% at 0.5 A g–1, and the capacity decay rate of per cycle is only 0.1% (starting on the third cycle), showing a good cycle property. Therefore, the as-prepared freestanding core–shell SC-NF material is a prospective anode material for high-performance lithium-ion batteries.