A novel composite of SnO_x nanoparticles and SiO₂@N-doped carbon nanofibers with durable lifespan for diffusion-controlled lithium storage

Carbon group materials, such as Si, SiO₂, Sn and SnO₂, with high theoretical capacity as anodes for lithium ion batteries (LIBs), suffer from the poor cycling stability resulting from the huge volume variation. To overcome the defects, a novel composite of hydrothermally synthesized ultrafine SnO_x nanoparticles and SiO₂@one-dimensional (1D) N-doped carbon nanofibers (SnO_x/SiO₂@N-CNF) is fabricated by electrospinning technique. Benefiting from the unique structure design that the SnO_x and SiO₂ nanoparticles are firmly encapsulated in the N-doped carbon nanofibers (N-CNFs), the SnO_x/SiO₂@N-CNF electrode exhibits not only excellent rate performance (434 mAh/g at 2 A/g), but also remarkable long-term cycling performance (754 mAh/g at 1 A/g after 1000 cycles) as the anode of LIBs. The N-CNFs can efficiently prevent the volume expansion and the direct contact with electrolyte of SnO_x and SiO₂, as well as shorten the diffusion path of lithium ions to improve the electrical conductivity. Interestingly, owing to the synergistic effect of SnO_x and SiO₂, the diffusion-controlled redox reaction dominates the charge transfer during charge-discharge process. As a consequence, the SnO_x/SiO₂@N-CNF could be a promising anode material with the extraordinary long-term cycling performance at high current densities, and provide a novel alternative anode material for LIBs quick-acting charging technology.