Preparation and re‐examination of Li 4 Ti 4.85 Al 0.15 O 12 as anode material of lithium‐ion battery

Spinel‐type Al 3+ ‐doped Li 4 Ti 5 O 12 oxide with the nominal composition of Li 4 Ti 4.85 Al 0.15 O 12 was synthesized by a cellulose‐assisted glycine–nitrate combustion process at reduced temperatures. X‐ray diffraction characterization demonstrated that all Al 3+ was successfully incorporated into the spinel lattice structure after calcination at 700°C. The Al 3+ doping did not have obvious effect on the phase formation and phase structure while it led to an increase in surface area and a decrease in crystallite size of the oxide. The discharge capacity, the rate performance and the cycling stability were all slightly improved after the Al 3+ doping. First discharge capacity ∼221 mAh g −1 was achieved for the as‐synthesized Li 4 Ti 4.85 Al 0.15 O 12 from calcination at 700°C, higher than 189 mAh g −1 for the pristine Li 4 Ti 5 O 12 prepared by the same way. Al 3+ was likely incorporated into both Li + tetrahedral site and Ti 4+ octahedral site with the majority into the Ti 4+ site. Al 3+ doping into the Li + tetrahedral site increased the reducibility of Ti 4+ ; consequently comparable electronic conductivity was observed for Li 4 Ti 5 O 12 and Li 4 Ti 4.85 Al 0.15 O 12 after the reduction. However, it also induced a decrease of lithium‐ion diffusion coefficient and a transition of rate‐limiting step of the electrode reaction from electron charge transfer for Li 4 Ti 5 O 12 to Li + diffusion for Li 4 Ti 4.85 Al 0.15 O 12 . The improved performance from the Al 3+ doping was mainly attributed to the increased surface area of the oxide. Copyright © 2010 John Wiley & Sons, Ltd.