Fe–Nb Co-Doped Rutile TiO2 for Anode Materials of Li-Ion Batteries

We attempted to improve electrochemical performances of a rutile TiO 2 electrode as a Li-ion battery anode by doping with two kinds of elements with different ionic sizes. When Nb 5+ and Fe 3+ were doped into TiO 2, the total doping amount could be increased up to 11 at.% because the doping amounts of Nb 5+ (9 at.%) and Fe 3+ (2 at.%) could exceed their solubility limits. It is considered that the compressive strain caused by the doping of larger Nb 5+ than Ti 4+ could be partially offset by the tensile strain induced by the doping of smaller Fe 3+ . The Fe–Nb-doped TiO 2 anode exhibited an excellent cycle performance and a good high-rate performance. We consider that these performances are attributed to the lattice parameter expansion and the electronic conductivity enhancement based on the increasing doping amount.