Preparation of nano-TiO2/activated carbon composite and its electrochemical characteristics in non-aqueous electrolyte

The composite of nano-TiO2/activated carbon (ACT) was prepared by hydrolytic precipitation of TiO2 from TiCl4 in a mixed aqueous solution containing activated carbon and followed by calcination at 450 °C. The physical characteristics of the activated carbon and ACT composite have been studied by X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectronic spectroscopy (XPS) and nitrogen adsorption–desorption measurements at 77 K. Three electrode systems with lithium metal as reference electrode were assembled to study the electrochemical performance of ACT composite and the activated carbon. It is found from galvanostatic charge–discharge tests that the mass specific capacitance and the area specific capacitance of ACT composite in the electrolyte of 1 M LiPF6–ethylene carbonate (EC)/diethyl carbonate (DEC)/dimethyl carbonate (DMC) increase by 20% and 50%, respectively compared to the pure activated carbon on average. The a.c. impedance spectra show that the ACT composite electrode has higher interfacial electron transfer resistance (Rt) but lower equivalent series resistance (Rs) than the pure activated carbon electrode has. Therefore ACT composite is a promising electrode active material for electrochemical capacitors.