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

Аннотация

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 Ti_1−xZr_xO₂(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, Ti_0.94Zr_0.06O₂(B) electrode had a capacity of 165 (mA h)/g. For undoped TiO₂(B), this parameter was only 135 (mA h)/g. Moreover, Ti_0.94Zr_0.06O₂(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 Ti_0.94Zr_0.06O₂(B) are the enhanced stability of the structure to lithiation/delithiation and an improved electrical conductivity.