Electrochemical Performance Evaluations of Spinel LiAl0.15Mn1.85O4 Cathode Materials Prepared by a Solution Combustion Technique for Lithium-Ion Batteries

LiAl 0.15 Mn 1.85 O 4 cathode materials have been rapidly synthesized by a solution combustion technique at various heat treatment time to investigate the crystal morphological change and evaluate the electrochemical performances. The structures of as-prepared samples were characterized by X-ray diffraction (XRD), which demonstrates that all the samples present the typically characteristic diffraction peaks of spinel LiMn 2 O 4 . The crystal morphological changes of the samples were observed by field emission scanning electron microscope (FESEM), which confirms that with the increase of heat treatment time, crystal morphology gradually grows to regular octahedron morphology, the average particle size becomes bigger, homogeneity of particle size distribution increases and agglomeration phenomenon is alleviated. Galvanostatic charge-discharge tests show that LiAl 0.15 Mn 1.85 O 4 sample sintered at 9 h exhibits the optimal cycling stability and rate performance, which delivers a capacity retention rate of 84.3 % after 500 cycles with an initial discharge specific capacity of 110.5 mAh g -1 at 1 C (1 C=148 mAh g -1 ) and 25 °C. At the higher rate of 5 C, a capacity retention rate of 82.1 % can be obtained after 500 cycles with an initial discharge specific capacity 103.2 mAh g -1 at 5 C and 25 °C. The elevated-temperature cycling stability of the sample at calcination of 9 h is also optimal, which shows a capacity retention rate of 90.1 % after 100 cycles with an initial discharge specific capacity of 105.3 mAh g -1 at 1 C and 55 °C. Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) tests prove that the sample at calcination of 9 h presents the better electrode reversibility, the lowest apparent activation energy, more rapidly charge-transfer and Li + diffusion kinetics processes.