Lithium-Excess Research of Cathode Material Li₂MnTiO₄ for Lithium-Ion Batteries

Lithium-excess and nano-sized Li_2+xMn₁_-/2TiO₄ (x = 0, 0.2, 0.4) cathode materials were synthesized via a sol-gel method. The X-ray diffraction (XRD) experiments indicate that the obtained main phases of Li_2.0MnTiO₄ and the lithium-excess materials are monoclinic and cubic, respectively. The scanning electron microscope (SEM) images show that the as-prepared particles are well distributed and the primary particles have an average size of about 20-30 nm. The further electrochemical tests reveal that the charge-discharge performance of the material improves remarkably with the lithium content increasing. Particularly, the first discharging capacity at the current of 30 mA g^-1 increases from 112.2 mAh g^-1 of Li_2.0MnTiO₄ to 187.5 mAh g^-1 of Li_2.4Mn_0.8TiO₄. In addition, the ex situ XRD experiments indicate that the monoclinic Li₂MnTiO₄ tends to transform to an amorphous state with the extraction of lithium ions, while the cubic Li₂MnTiO₄ phase shows better structural reversibility and stability.