Spinel based lithium manganese oxide is the most attractive cathodes for lithium-ion battery due to high capacity, low cost, and non-toxic. This material has a theoretical high capacity of 296 mAh g^-1 (2 Li⁺ ions) if Li⁺ ions are fully inserted/extracted into/from the spinel structure. However, it is well known that when LiMn₂O₄ is discharged to a low voltage, e.g., 2 V, high spin Mn³⁺ ions may induce severe Jahn-Teller distortion. Up to date, this material is only used in the 4 V region with a low capacity of 120 mAh g^-1. [1, 2]

Much effort has been made to enhance the cycle stability of such cathode materials in a wide voltage window (e.g., 2.0-4.8 V). The substitution of titanium for manganese can improve the cycle life of cathode materials but with a decrease in the capacity of material which restrict its usage in a broad application. [2, 3]

In this paper, Li_1+zMnTiO₄ (z = 0, 0.5, and 1) were developed to solve the problems of low capacity and short cycle life. Excess lithium material (z = 0.5 and 1) formed a solid-solution with notation (1-a)LiMn_2-xTi_xO₄.aLi₂Mn_yTi_1-yO₃, which improve the capacity of material up to 218 mAh g^-1, after 60 cycles with a capacity retention of 93 %. The structure and electrochemical properties were investigated carefully through X-ray diffraction, galvanostatic cycling, cyclic voltammetry (CV), galvanostatic intermittent titration technique (GITT) to understand the mechanism of the improvement in the capacity and cycle stability of material. We also analyzed the effect of impurity phase as a significant factor that affects the electrochemical performance of the cathodes.

References

1. Thackeray, M.M. Prog. Solid State Chem. 1997, 25 (1–2), 1-71
2. Wang, S.; Yang, J.; Wu, X.; Li, Y.; Gong, Z.; Wen, W.; Lin, M.; Yang, J.; Yang, Y. J. Power Sources. 2014, 245, 570-578.
3. Chen, R.; Knapp, M.; Yavuz, M.; Heinzmann, R.; Wang, D.; Ren, S.; Trouillet, V.; Lebedkin, S.; Doyle, S.; Hahn, H.; Ehrenberg, H.; Indris, S. J. Phys. Chem. C. 2014, 118 (24), 12608-12616.