Structure and high rate performance of Ni2+ doped Li4Ti5O12 for lithium ion battery

Li4−2xNi3xTi5−xO12 (0 ≤ x ≤ 0.25) has been synthesized via solid-state reaction. X-ray diffractions (XRD) demonstrate that all doped samples have a spinel structure with Fd 3 ¯ m space group without any impurities. Through further Rietveld refinements, it is shown that both lattice parameter and occupancy of non-Li+ ions in the 8a sites negligibly change with the amount of Ni2+ dopants. Scanning electron microscope reveals that Ni2+ doping does not change the morphology of Li4Ti5O12. The best electronic conductivity of Ni2+ doped Li4Ti5O12 is at least one order of magnitude higher than that of the pristine one, while all samples have similar Li+ ion diffusion coefficients. The electrochemical performance of Ni2+ doped Li4Ti5O12 shows good rate capability. The specific capacity of Li3.9Ni0.15Ti4.95O12 at 5 C is as high as 72 mAh g−1, while that of the pristine one can only achieve 33 mAh g−1. This improved rate performance can be ascribed to its enhanced electronic conductivity.