Improvement of tap density of TiO2(B) powder as high potential negative electrode for lithium ion batteries

•The morphology of TiO2(B) powder were controlled using large-size Nb-doped rutile TiO2.•The tap density of Nb-doped samples was improved by a factor of 2.•The discharge capacity per electrode volume was significantly improved by Nb-doping.

To improve the tap density of TiO2(B) as a high potential negative electrode for lithium-ion batteries, the particle size and the shape of the TiO2(B) were controlled by a new synthetic method using large-size Nb-doped rutile TiO2 as a starting material. The Nb-doped TiO2(B) particles, Ti0.93Nb0.07O2(B) and Ti0.90Nb0.10O2(B), were much smaller (diameter: ca. 100 nm, length: ca. 800 nm) than the conventional TiO2(B) prepared using fine anatase TiO2 particles as a starting material, and were agglomerated to form secondary particles with a diameter of 3–30 μm. The tap densities of Ti0.93Nb0.07O2(B) and Ti0.90Nb0.10O2(B) were successibly high (0.77 and 0.66 g cm−3, respectively), which were ca. 2-fold higher than that of the conventional TiO2(B) (0.30 g cm−3). As a result, the discharge capacity per electrode volume was significantly improved for both Nb-doped samples without sacrificing the cycleability. Non-doped TiO2(B) was prepared from large-size rutile TiO2 by a similar method, but it deteriorated upon cycling, accompanied by the formation of the anatase phase. It was shown that Nb-doping not only improves the discharge capacity per electrode volume, but also effectively stabilizes the TiO2(B) crystal structure of the small particles.