High electrochemical stability Al-doped spinel LiMn₂O₄ cathode material for Li-ion batteries

High electrochemical stability Al-doped LiMn₂O₄ (LMO) cathode materials for Li-ion batteries were synthesized using a simple combustion method with degreased cotton fiber as the carrier. The precursors of Mn, Li, and Al sources with different stoichiometric ratios were dissolved into alcohol, then a rapid combustion process was conducted to produce the Al-doped LiMn_2-xAl_xO₄ (x = 0.05, 0.10, and 0.16). The morphology and properties of the Al-doped LMOs were characterized by X-ray diffraction (XRD) analysis and scanning electron microscopy (SEM). Results indicated that both the particle size and lattice parameters of the Al-doped LMOs decreased with an increase in the Al doping ratio, as theoretically supported by the ab initio calculation. This phenomenon is conducive to full contact between the electrolyte and cathode materials, and so can shorten the diffusion distance between of Li⁺ ions in solid phase. Electrochemical characterization showed that Al doping can improve the cycle performance of LMO. A doping content of 16 at.% to LMO showed excellent electrochemical performance, with a first-charge specific capacity of 100.7mAh/g and a capacity retention rate of 93.9% after 400 cycles at a current rate of 0.5 C.