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

Abstract

To improve the reversible capacity of TiO2(B) negative electrode close to the theoretical one, some preparation and experimental conditions such as the precursor (Na2Ti3O7, K2Ti4O9 and Cs2Ti5O11), the co-solvent in ethylene carbonate-based electrolyte solutions, and homogeneity of the composite electrode were optimized. TiO2(B) powder samples were successfully prepared from K2Ti4O9 and Cs2Ti5O11 precursors, but not from Na2Ti3O7. The sample prepared from Cs2Ti5O11 gave a higher discharge capacity (185.5 mAh g−1) than that prepared from K2Ti4O9 (156.6 mAh g−1). The reversible capacity of TiO2(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 LiPF6 dissolved EC+DMC (1:2 by volume). Furthermore, improvement of the homogeneity of the composite electrode by premixing the TiO2(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).