Effects of a dopant on the electrochemical properties of Li4Ti5O12 as a lithium-ion battery anode material

Li4Ti5O12 and Al3+ doped Li(4-x/3)AlxTi(5-2x/3)O12 (x = 0, 0.01, 0.05, 0.1, 0.15, 0.2) are synthesized at 750, 850, 950 degrees C via solid state reaction using TiO2-rutile, Li2CO3 and Al2O3 as precursors. The samples at 850, 950 degrees C have better phase purity than those at 750 degrees C. The preliminary charge-discharge cycling test of undoped and Al3+ doped Li4Ti5O12 reveals that the electrochemical performance of the electrode prepared at 850 degrees C is better than that at 750, 950 degrees C. Therefore, the optimum calcination temperature is found to be 850 degrees C. Li(4-x/3)AlxTi(5-2x/3)O12 (x = 0.01, 0.05, 0.1), which is the low Al-doped sample, exhibits a higher discharge capacity and rate performance than the high Al-doped Li4Ti5O12 (x = 0.15, 0.2) sample. The first discharge capacities at 0.2, 0.5, and 1 C are 174.4, 161.9, and 153.8 mAh g(-1), respectively for Li(4-x/3)AlxTi(5-2x/3)O12 (x = 0.1). These values are similar to those of Li(4-x/3)AlxTi(5-2x/3)O12 (x = 0.01, 0.05). The capacity retention ratio of Li(4-x/3)AlxTi(5-2x/3)O12 (x = 0.01, 0.05, 0.1) is over 99.3% after 30 cycles. The capacity increase and good rate performance in the optimum Al-doped Li4Ti5O12 are discussed in relation to the stability of the spinel structure and the resulting ease of lithium insertion. (C) 2013 Elsevier B.V. All rights reserved.