Boosting the rate capability of multichannel porous TiCh nanofibers with well-dispersed Cu nanodots and Cu^2+-doping derived oxygen vacancies for sodium-ion batteries

The use of TiO2 as an anode in rechargeable sodium-ion batteries(NIBs)is hampered by intrinsic low electronic conductivity of TiO2 and in ferior electrode kinetics.Here,a high-performa nee T1O2 electrode for NIBs is prese nted by desig ning a multicha rinel porous T1O2 nano fibers with well-dispersed Cu nan odots and Cu^2+-doping derived oxyge n vaca ncies(Cu-MPTO).The in-situ grow n well-dispersed copper nano dots of about 3 nm on TiO2 surface could significantly enhance electronic conductivity of the TiO2 fibers.The one-dimensional multichannel porous structure could facilitate the electrolyte to soak in,leadi ng to short tran sport path of Na^+through carb on toward the TiO2 nano particle.The Cu^2+-doping induced oxygen vacancies could decrease the bandgap of T1O2,resulting in easy electron trapping.With this strategy,the Cu-MPTO electrodes render an outstanding rate performance for NIBs(120 mAh·g^-1 at 20 C)and a superior cycling stability for ultralong cycle life(120 mAh·g^-1 at 20 C and 96.5%retention over 2,000 cycles).Density functional theory(DFT)calculations also suggest that Cu^2+doping can enhance the conductivity and electron transfer of T1O2 and lower the sodiation energy barrier.This strategy is confirmed to be a general process and could be extended to improve the performance of other materials with low electronic conductivity applied in energy storage systems.