Synergistic modification of commercial TiO2 by combined carbon sources of citric acid and sodium carboxymethyl cellulose

Abstract

Commercial TiO₂ (c-TiO₂) has attracted growing attention as a promising negative electrode material for Li-ion batteries owing to its high theoretical capacity and low cost, but the impurities deteriorate its electrochemical performance. Herein, a synergistic modification was proposed to ameliorate the electrochemical performance of c-TiO₂ by adopting double carbon precursors of citric acid and sodium carboxymethyl cellulose (CMC-Na) to adjust the carbon- and Na⁺-doping contents. For the collocation of 15 wt% citric acid and 4 wt% CMC, the carbonized product at 750 °C achieved the optimized performance (166.2 mA h g⁻¹ after 900 cycles at 500 mA g⁻¹). Combining the structure and composition data with CV plots and electrochemical impedance spectra, the thin uniform carbon coating and Ti³⁺ induced by Na⁺-doping promoted the electrical conductivity among and inside the TiO₂ particles, while the augmented lattice constant of TiO₂ resulting from the Na⁺-doping also boosted the Li⁺-ion diffusion, thus leading to a distinct optimization of the performance.