Despite the low price of commercial TiO2 (c-TiO2), the poor electrochemical performance restricts its practical application in Li-ion batteries, so clarifying the reasons and taking appropriate measures to improve the performance are of great significance. Herein, c-TiO2 was coated with carbon at 600 and 750°C using glucose as the carbon source. The product obtained at 750°C exhibits markedly enhanced reversible capacities and outstanding rate performance compared to that obtained at 600°C. In terms of the comparative experiments and detailed characterizations by several techniques, the SO4 2− remained in the c-TiO2 is the dominant impurity affecting the electrochemical performance mostly. The thorough decomposition of SO4 2− at 750°C and the formation of carbon coating give rise to the enhanced electronic and ionic conductivities of the c-TiO2, and thus are responsible for the significant improvement in the electrochemical performance. The easy fabrication and the low cost of the raw materials enable the carbon-coated c-TiO2 to industrially apply in the LIBs.