Effects of crystal structure and plane orientation on lithium and nickel co-doped spinel lithium manganese oxide for long cycle life lithium-ion batteries

Various Li-rich spinel Li 1+ x Ni 0.05 Mn 1.95- x O 4 (0 ≤  x  ≤ 0.10) cathode materials with a truncated octahedron were synthesized by a solution combustion method. The relationship of crystalline structure, particles morphology and electrochemical properties of the as-prepared samples was investigated via a series of physicochemical characterizations. The Li-Ni co-doping changes the lattice parameters and atomic configuration, whilst resulting in a contraction of unit cell dimension and giving rise to a variation of bond length. In this regard, the shrinkage of octahedral MnO 6 provides a robust structure and the expansion of tetrahedral LiO 4 facilitates a fast electrochemical process. Additionally, the resulted polyhedral Li 1+ x Ni 0.05 Mn 1.95- x O 4 samples present the exposed (1   1   0), (1   0   0), and (1   1   1) crystal planes, which provide the favorable Li + ions diffusion/transmission channel and alleviate Mn dissolution. Owing to these merits of polyhedral structure and Li-Ni co-doping, the optimized Li 1.02 Ni 0.05 Mn 1.93 O 4 exhibits good electrochemical performance with high initial discharge capacity of 119.8, 107.1 and 97.9 mAh·g −1 at 1, 5 and 10 C, respectively. Even at a high current rate of 15 C, an excellent capacity retention of 91.7% is obtained after 1000 cycles, whilst the high temperature performance was also improved.