Coaxial electrospinning synthesis free-standing Sn/TiO2 flexible carbon fibers with sheath/core structure for advanced flexible lithium/potassium-ion batteries

Flexible Sn/TiO 2 carbon nanofiber (ST-NCF) composites were constructed by doping TiO 2 into tin-based carbon nanofibers via coaxial electrospinning. Sn/TiO 2 carbon nanofiber was directly used as an anode for Lithium-ion Batteries (LIBs) and Potassium-ion Batteries (PIBs), which show exceptional electrochemical performances. The layered sheath/core structure of the material lead to its good electrochemical properties, where the core Sn carbon nanofiber was encapsulated by the sheath layer of TiO 2 nanoparticles. In addition to enhancing its electrical conductivity, the outer TiO 2 and N-doped carbon fiber matrix also provide a buffer zone for volumetric strain during charging and discharging. The fiber core Sn and sheath TiO 2 form a heterojunction interface on the two-dimensional tube surface, which increases the diffusion rate of ions and electrons. After 100 cycles, TiO 2 -NCF and ST-NCF-40%TBT (40% TBT indicates the percentage of TiO 2 in shell solution to the total composition of shell spinning solution) show capacities of 386.6 mAh g −1 and 1336 mAh g -1 , respectively, at 0.5A g -1 . After 2000 cycles, ST-NCF-40%TBT in LIBs displayed a high capacity of 299 mAh g -1 at 10 A g -1 . After 350 cycles at 1A g -1 , the capacity of ST-NCF-40%TBT in PIBs is reserved at 307 mA h g -1 . Due to the superior mechanical flexibility of ST-NCF-40%TBT films, it will be a promising anode candidate for flexible LIBs and PIBs.