Improvement of tap density of TiO_2(B) powder as high potential negative electrode for lithium ion batteries

摘要

To improve the tap density of TiO_2(B) as a high potential negative electrode for lithium-ion batteries, the particle size and the shape of the TiO_2(B) were controlled by a new synthetic method using large-size Nb-doped rutile TiO_2 as a starting material. The Nb-doped TiO_2(B) particles, Ti_(0.93)Nb_(0.07)O_2(B) and Ti_(0.90)Nb_(0.10)O_2(B), were much smaller (diameter: ca. 100 nm, length: ca. 800 nm) than the conventional TiO_2(B) prepared using fine anatase TiO_2 particles as a starting material, and were agglomerated to form secondary particles with a diameter of 3-30 μm. The tap densities of Ti_(0.93)Nb_(0.07)O_2(B) and Ti_(0.90)Nb_(0.10)O_2(B) were successibly high (0.77 and 0.66 g cm~(-3), respectively), which were ca. 2-fold higher than that of the conventional TiO_2(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 TiO_2(B) was prepared from large-size rutile TiO_2 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 TiO_2(B) crystal structure of the small particles.