Improvement of the Reversible Capacity of TiO2(B) High Potential Negative Electrode

To improve the reversible capacity of TiO 2 (B) negative electrode close to the theoretical one, some preparation and experimental conditions such as the precursor (Na 2 Ti 3 O 7 , K 2 Ti 4 O 9 and Cs 2 Ti 5 O 11 ), the co-solvent in ethylene carbonate-based electrolyte solutions, and homogeneity of the composite electrode were optimized. TiO 2 (B) powder samples were successfully prepared from K 2 Ti 4 O 9 and Cs 2 Ti 5 O 11 precursors, but not from Na 2 Ti 3 O 7 . The sample prepared from Cs 2 Ti 5 O 11 gave a higher discharge capacity (185.5 mAh g −1 ) than that prepared from K 2 Ti 4 O 9 (156.6 mAh g −1 ). The reversible capacity of TiO 2 (B) was significantly influenced by the kind of co-solvent in the electrolyte solutions. The presence of dimethyl carbonate (DMC) as a co-solvent drastically improved the capacity, and the highest discharge capacity of 235.3 mAh g −1 was obtained in 1 M LiPF 6 dissolved EC+DMC (1:2 by volume). Furthermore, improvement of the homogeneity of the composite electrode by premixing the TiO 2 (B) and Ketjen Black conductor was effective to improve the discharge capacity. The optimized electrode gave an initial discharge capacity of 314.4 mAh g −1 , which reached 93.9% of the theoretical capacity (335 mAh g −1 ). It also exhibited a good cycleability (287.9 mAh g −1 after 50 cycles) and a high rate capability (118.5 mAh g −1 at 10 C rate).