Effect of lithium content on spinel phase evolution in the composite material LixNi0.25Co0.10Mn0.65O(3.4 + x) / 2 (0.8 ≤ x ≤ 1.6) for Li-ion batteries

• LixNi0.25Co0.10Mn0.65O(3.4 + x) / 2 (x = 1.6, 1.4, 1.2, 1.0, 0.8) were well synthesized.
• The Rietveld refinement indicates the presence of Li2MnO3, LiMO2, and LiM2O4.
• Structural analysis reveals that the spinel phase is [Li+,Co2 +][Ni2 +,Co3 +,Mn4 +]2O4.
• A low Li level induces primary particle growth, as well as Co and Ni segregation.

The composite material LixNi0.25Co0.10Mn0.65O(3.4 + x) / 2 (x = 1.6, 1.4, 1.2, 1.0, 0.8) were synthesized and characterized for their structural, morphological, and performance as cathode materials in Li-ion batteries. The Rietveld refinement results indicate the presence of two phases at high lithium levels (x = 1.6 and 1.4): Li2MnO3 (C2/m) and LiMO2 (MNi, Co, Mn) (R3¯m); the latter contains Ni2 + and Ni3 +. At low lithium levels (x = 1.2, 1.0, and 0.8) an additional spinel phase LiM2O4 (Fd3¯m) emerges, which is known to affect the electrochemical performance of the oxide. Structural analysis reveals that the spinel phase contains mixed transition metals Ni, Co, and Mn as [Li+,Co2 +][Ni2 +,Co3 +,Mn4 +]2O4. A low lithium level is found to induce primary particle growth, as well as Co and Ni segregation within the secondary particles. These results are expected to contribute to material optimization and commercialization of lithium-rich oxide cathodes.