Electrospun Ta-doped TiO/C nanofibers as a high-capacity and long-cycling anode material for Li-ion and K-ion batteries

Ta-doped TiO 2 /C nanofibers are synthesized by an electrospinning method. First-principles calculations reveal that the Ta dopant can lower the Li/K diffusion barrier, which is beneficial for improving the rate capability. According to the electronic structure analysis, the dopant can obviously shift the conduction band of TiO 2 downward, resulting in significantly improved electronic conductivity. Ta doping causes phase transformation from anatase to rutile, and increases the specific surface area. The well-designed rutile Ta-doped TiO 2 /C nanofibers show outstanding electrochemical properties in both Li-metal half cells and K-metal half cells, which are much better than those of pristine anatase TiO 2 /C nanofibers. At 2 A g −1 , 5% rutile Ta-doped TiO 2 /C nanofibers could deliver high reversible specific capacities of 399 mA h g −1 in Li-ion batteries after 1000 cycles whereas deliver 148 mA h g −1 in K-ion batteries after 800 cycles. When assembled, the full cells with 5% rutile Ta-doped TiO 2 /C nanofibers as the anode and commercial LiFePO 4 /perylene-3,4,9,10-tetracarboxylic dianhydride as the cathode show excellent cycling performance and can light up more than 18 LEDs. These results demonstrate that Ta-doped TiO 2 /C nanofibers are a promising anode material for Li/K ion batteries. Ta-doped TiO 2 /C nanofibers can enhance the electrical conductivity, shorten the ion transport distance. Thus it shows outstanding electrochemical performance in both Li/K-metal half cells and Li/K full cells..