Improvement of the Reversible Capacity of TiO 2 (B) High Potential Negative Electrode

Abstract

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 2Ti 3O 7, K 2Ti 4O 9 and Cs 2Ti 5O 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 2Ti 4O 9 and Cs 2Ti 5O 11 precursors, but not from Na 2Ti 3O 7. The sample prepared from Cs 2Ti 5O 11 gave a higher discharge capacity (185.5 mAh g -1) than that prepared from K 2Ti 4O 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). © 2011 The Electrochemical Society.