TiO2 (B)/activated carbon non-aqueous hybrid system for energy storage

TiO2 (B) has been investigated as a possible candidate to replace Li4Ti5O12 as a negative electrode for Li-ion battery. The starting compound was synthesized by a simple solid state reaction followed by hydrolysis. Long term stability of the TiO2 (B) electrode can be obtained by limiting lithium intercalation between 0.25 and 0.35 Li+ per unit formula. High cycling rates (up to 24C) have been used without noticeable degradation of the electrode. A non-aqueous hybrid energy storage device using TiO2 (B) as the negative electrode and activated carbon as the positive was assembled. The maximum hybrid cell voltage can be set between 2.75 V and 3.5 V. The cells exhibit energy densities between 45 W kg−1 and 80 W kg−1 with power densities in the range 240–420 W kg−1 which is compatible with a fast charging/discharging storage device, intermediate between electrochemical double layer capacitor and Li-ion batteries.