Structural Underpinnings of the Enhanced Cycling Stability upon Al-Substitution in LiNi_0.45Mn_0.45Co_0.1–yAl_yO₂ Positive Electrode Materials for Li-ion Batteries

Single-phase LiNi_0.45Mn_0.45Co_0.1–yAl_yO₂ layered oxide materials with 0 ≤ y ≤ 0.10 were prepared using the glycine-nitrate combustion method. Al-substitution has a minimal effect on the defect concentration and rate capability of the materials, but raises the operating voltage and reduces the capacity fade of the materials during prolonged cycling compared to the unsubstituted system. In situ X-ray diffraction suggests the presence of Al has a significant structural impact during battery operation. It acts to limit the changes in lattice parameters observed during electrochemical charging and cycling of the materials. High-resolution X-ray diffraction reveals structural distortions in the transition metal layers of as-synthesized powders with high Al-contents, as well as a structural evolution seen in all materials after cycling.