Electrochemical properties of Li4Ti5−2xNixMnxO12 compounds synthesized by sol–gel process

Ni and Mn co-doped spinel Li4Ti5O12 materials in the form of Li4Ti5−2xNixMnxO12 (x = 0.000, 0.050, 0.075, 0.100, 0.125) were prepared by sol–gel route and following calcination in an air atmosphere, and were used as anode materials of Li-ion battery. The structures, morphologies and electrochemical properties of the as-prepared materials were characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), charge/discharge cycling, cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The results showed that Ni and Mn co-doping did not change the electrochemical reaction mechanism of Li4Ti5O12, but can clearly influence its morphology and particle size. Besides, the Li4Ti5O12 samples co-doped with different molar fractions of Ni and Mn exhibited an enhanced electrochemical performance even at high current rate. It has been found that the spinel Li4Ti5−2xNixMnxO12 delivered a high reversible capacity and showed excellent cycling performance, especially Li4Ti4.8Ni0.1Mn0.1O12 exhibited a relatively good rate capability and excellent cycling stability. The initial discharge capacity of Li4Ti4.8Ni0.1Mn0.1O12 sample was 172.41 mAh g−1 at a current of 0.5 C, which was nearly close to the theoretic specific capacity of LiTi5O12; furthermore, a high discharge specific capacity of 142.53 mAh g−1 was still kept after 100 cycles.