Effect of Ni Doping Content on Phase Transition and Electrochemical Performance of TiO(2) Nanofibers Prepared by Electrospinning Applied for Lithium-Ion Battery Anodes

Titanium dioxide (TiO(2)), as a potential anode material applied for lithium-ion batteries (LIBs), is constrained due to its poor theoretical specific capacity (335 mAh·g(−1)) and low conductivity (10(−7)-10(−9) S·cm(−1)). When compared to TiO(2), NiO with a higher theoretical specific capacity (718 mAh·g(−1)) is regarded as an alternative dopant for improving the specific capacity of TiO(2). The present investigations usually assemble TiO(2) and NiO with a simple bilayer structure and without NiO that is immersed into the inner of TiO(2), which cannot fully take advantage of NiO. Therefore, a new strategy was put forward to utilize the synergistic effect of TiO(2) and NiO, namely doping NiO into the inner of TiO(2). NiO-TiO(2) was fabricated into the nanofibers with a higher specific surface area to further improve their electrochemical performance due to the transportation path being greatly shortened. NiO-TiO(2) nanofibers are expected to replace of the commercialized anode material (graphite). In this work, a facile one-step electrospinning method, followed by annealing, was applied to synthesize the Ni-doped TiO(2) nanofibers. The Ni doping content was proven to be a crucial factor affecting phase constituents, which further determined the electrochemical performance. When the Ni doping content was less than 3 wt.%, the contents of anatase and NiO were both increased, while the rutile content was decreased in the nanofibers. When the Ni doping content exceeded 3 wt.%, the opposite changes were observed. Hence, the optimum Ni doping content was determined as 3 wt.%, at which the highest weight fractions of anatase and NiO were obtained. Correspondingly, the obtained electronic conductivity of 4.92 × 10(−5) S⋅cm(−1) was also the highest, which was approximately 1.7 times that of pristine TiO(2). The optimal electrochemical performance was also obtained. The initial discharge and charge specific capacity was 576 and 264 mAh·g(−1) at a current density of 100 mA·g(−1). The capacity retention reached 48% after 100 cycles, and the coulombic efficiency was about 100%. The average discharge specific capacity was 48 mAh·g(−1) at a current density of 1000 mA·g(−1). Approximately 65.8% of the initial discharge specific capacity was retained when the current density was recovered to 40 mA·g(−1). These excellent electrochemical results revealed that Ni-doped TiO(2) nanofibers could be considered to be promising anode materials for LIBs.