Effect of Isovalent Doping by Zr4+ Ions on the Electrochemical Behavior of TiO2(B)

In this study, TiO2(B) metastable β-TiO2 or bronze TiO2 was doped with Zr4+ (Zr/Ti = 0.03; 0.06) through hydrothermal approach. The materials were shown to be nanobelts (thickness: 10–l5 nm, width: 50–100 nm, length: several micrometers, and specific surface area: 72–76 m2/g). Doping the TiO2(B) structure with Zr4+ was found to be accompanied by the formation of Ti1−xZrxO2(B) (x = 0.03; 0.06) solid solutions, where the unit cell volume increases as the zirconium content rises. For doped TiO2(B), electrical conductivity increased by two order of magnitude, from 1.6 × 10−11 in an undoped sample to 8.2 × 10−10 S/cm for Zr/Ti = 0.06. After 90 charge/discharge cycles at the C/10-rate, Ti0.94Zr0.06O2(B) electrode had a capacity of 165 (mA h)/g. For undoped TiO2(B), this parameter was only 135 (mA h)/g. Moreover, Ti0.94Zr0.06O2(B) retained a reversible capacity of about 107 (mA h)/g even under an increased current load (5C). The major factors influencing the electrochemical behavior of Ti0.94Zr0.06O2(B) are the enhanced stability of the structure to lithiation/delithiation and an improved electrical conductivity.