Highly pseudocapacitive Nb-doped TiO2 high power anodes for lithium-ion batteries

Abstract

Nb-doped TiO₂ (anatase) nanoparticles were synthesized using a continuous hydrothermal flow synthesis reactor using a supercritical water flow as a reagent and crystallizing medium. The as-prepared nano-powders with ca. 25 at% Nb⁵⁺ (<6 nm diameter) were used as possible anodes for lithium-ion batteries without any further heat-treatment. Cyclic voltammetry and galvanostatic charge/discharge cycling tests were performed in the range of 1.2 to 3.0 V vs. Li/Li⁺. The Nb-doped TiO₂ samples showed superior capacity retention at high current rates compared to the corresponding undoped nano-TiO₂. The superior performance of the doped samples (at specific currents up to 15 A g⁻¹) was attributed to higher electronic conductivity and a greater charge storage contribution from surface effects like pseudocapacitance (Faradaic processes) as well as Helmholtz double layer charge storage.