Research on the Electrochemical Performance of Rutile and Anatase Composite TiO2 Nanotube Arrays in Lithium-Ion Batteries.

Titanium dioxide is considered as an ideal anode material for lithium-ion batteries. It has many different polymorphs such as anatase and rutile, etc. Both nano-scale rutile and anatase exhibit large potential in accommodating Li ions. Although the electrochemical performance of the rutile or anatase has been studied very well, their combined effect in lithium battery is still unclear at present. In our work, a kind of rutile and anatase composite TiO2 nanotube arrays was synthesized by two steps: anodization and heat treatment. The characteristics of the composite arrays were examined by XRD, SEM, and TEM. The first discharge capacity and charge capacity at 0.1 C (1C = 335 mA h g(-1)) of the composite is about 230 mA h g(-1), and 210 mA h g(-1), which are higher than pure anatase of 180 mA h g(-1) and 173 mA h g(-1). The composite remain about 80% of its initial capacities (185 mA h g(-1)) after 100 cycles. Two anodic peaks around 1.8 V and 2.2 V can be found in the composite in the cyclic voltammetry curves, while there is only one anodic peak in anatase. The separation of anodic and cathodic peak potentials of composite is less than that of anantase, indicating a better charge/discharge reversibility. The electrochemical impedance spectrum test shows the resistance of the composite is larger than that of pure anatase due to that the composite have more grain boundaries. The higher specific capacities of composite arrays may ascribe to the rutile's larger amount of lithium ions insertion and the defects facilitate lithium ions migration. Our work demonstrates that a better electrochemical performance of TiO2 can be achieved by synthesizing the composite material.