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