Exploring the Impact of Aluminum Substitution on the Structural Stability of LiMn₂O₄/C Cathode Materials for Lithium-Ion Batteries

Aluminum is substituted for manganese in spinel LiMn2O4 (LMO) materials to enhance their structural and electrochemical properties as cathodes for next-generation Li-ion batteries (LIBs). The computation method, in conjunction with the effect of aluminum (Al) substitution, performed a basic optimization of the initial step of this report. The phase purity and Al substitution in the Mn sites were confirmed using powder X-ray diffraction and X-ray photoelectron spectroscopy. Utilizing electron microscopy, we established that the agglomeration of nanosized Al-doped LMO particles with improved grain distribution is dependent on the Al content (X), respectively. The prepared Al-doped LMO cathode exhibited outstanding electrochemical properties depending on the amount of Al substitution. In detail, LiMn1.975Al0.025O4 shows a superior high rate performance of 109.5 mAh g(-1 )at 10C, which corresponds to 81.1% initial capacity retention at 0.1C within the 3.3-4.3 V potential window. LiMn1.95Al0.05O4, a higher Al composition material, shows excellent cycle performance of 93.3% capacity retention after 100 cycles at 0.1C when compared to the initial capacity within the same potential window. The remarkable cycle and rate performance of the Al-doped LMO cathodes can be ascribed to the combined effect of the enhanced structural properties and the well-distributed grains resulting from Mn3+/Mn4+ substitution with Al3+ ions. Furthermore, from the cyclic voltammetry and impedance characterizations, we identified a highly stable electrochemical reaction and high rate performance in the LMO electrode with 0.025 Al content.