Graphene-Wrapped Anatase TiO(2) Nanofibers as High-Rate and Long-Cycle-Life Anode Material for Sodium Ion Batteries

Anatase TiO(2) has been suggested as a potential sodium anode material, but the low electrical conductivity of TiO(2) often limits the rate capability, resulting in poor electrochemical properties. To address this limitation, we propose graphene-wrapped anatase TiO(2) nanofibers (rGO@TiO(2) NFs) through an effective wrapping of reduced graphene oxide (rGO) sheets on electrospun TiO(2) NFs. To provide strong electrostatic interaction between the graphene oxide (GO) sheets and the TiO(2) NFs, poly(allylamine hydrochloride) (PAH) was used to induce a positively charged TiO(2) surface by the immobilization of the -NH(3)(+) group and to promote bonding with the negatively charged carboxylic acid (-COO(−)) and hydroxyl (-O(−)) groups on the GO. A sodium anode electrode using rGO@TiO(2) NFs exhibited a significantly improved initial capacity of 217 mAh g(−1), high capacity retention (85% after 200 cycles at 0.2C), and a high average Coulombic efficiency (99.7% from the second cycle to the 200(th) cycle), even at a 5C rate, compared to those of pristine TiO(2) NFs. The improved electrochemical performances stem from highly conductive properties of the reduced GO which is effectively anchored to the TiO(2) NFs.