Improvement of Tap Density of TiO 2 (B) Powder as High Potential Negative Electrode

The shape and size of TiO 2 (B) particles were controlled by ball-milling K 2 Ti 4 O 9 , H 2 Ti 4 O 9 and TiO 2 (B) powders to improve the tap density of TiO 2 (B). It was found that only K 2 Ti 4 O 9 endured the ball-milling process and provided a fine TiO 2 (B) powder after the ion-exchange and dehydration processes. In contrast, ball-milling of H 2 Ti 4 O 9 and TiO 2 (B) powders resulted in a formation of a large amount of the rutile and anatase phase, respectively. In addition, a reduction of the spinning rate to 600 rpm suppressed the formation of the minor impurity of the anatase phase in the TiO 2 (B) sample prepared from the milled K 2 Ti 4 O 9 powder. The resulting TiO 2 (B) (M1-600) powder exhibited a high tap density of 0.71 g cm -3 and a high electrode density of 1.25 g cm -3 , which were 2.37 and 1.29 times, respectively, higher than those of the pristine TiO 2 (B). In charge/discharge tests, M1-600 exhibited a discharge of 213.1 mAh g -1 , which is higher than that of the pristine TiO 2 (B), with a good cycleability. It gave a discharge capacity of 80.1 mAh g -1 even at a high rate of 10 C.