Li4Ti4.94Tb0.06O12-δ has been synthesized via a facile co-precipitation method. The structure and morphology of the as-prepared sample have been characterized by X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy, and particle size distribution analysis. The results show that Tb3+ is successfully doped into the Li4Ti5O12 structure and that the average particle size is about 111 nm. Li4Ti4.94Tb0.06O12-δ exhibits a high initial discharge capacity of 166.5 mAh g-1 at 20 C, and the discharge capacity retention is nearly 93% after 500 cycles. In addition, the sample shows much improved rate capability at 20 C compared with pure Li4Ti5O12. Tb3+ doping not only enhances the electronic conductivity, but also improves the Li+ ion diffusivity in Li4Ti5O12, which indicates that Tb3+ doping is beneficial for promoting the electrochemical performance of Li4Ti5O12.