Effect of Calcination Temperature and Oxygen-Assisted Coprecipitation on the Structural and Electrochemical Properties of Li-Rich Lix[Ni0.8Mn0.1Co0.1]O2 Cathode Materials

Abstract

Abstract. Lithium-rich layered oxide cathodes, Lix[Ni0.8Mn0.1Co0.1]O2, were synthesized via an oxygen-assisted coprecipitation method followed by calcination at 720 °C, 750 °C, and 780 °C. The introduction of O2 during coprecipitation facilitates in situ oxidation of Mn2+ to higher valence states, leading to Mn-enriched regions within the hydroxide precursor that form Li2MnO3-like domains in the layered structure upon calcination. The primary objective of this study was to systematically investigate the effect of calcination temperature on crystal structure, Li/Ni cation ordering, microstructure, and electrochemical performance. Structural analysis revealed that the 750 °C annealed sample exhibits the lowest Li/Ni disorder, optimal hexagonal ordering, and a porous nanosheet-based morphology, which together promote rapid lithium-ion diffusion. Electrochemical testing shows that this sample achieves the highest initial discharge capacity (∼145 mAh/g), excellent capacity retention (85.4% after 100 cycles), and good rate capability (77.5% retention at 5C). Samples annealed at 720 °C and 780 °C showed reduced performance due to incomplete crystallization and microstructural collapse, respectively. This work demonstrates that optimizing calcination temperature in combination with O2-assisted coprecipitation provides a scalable route to structurally robust lithium-rich NMC cathodes. While the initial capacity is lower than that of commercial NMC811, the study provides valuable insights into the interplay between synthesis conditions, structural ordering, and electrochemical behavior, highlighting design strategies for stable and reversible lithium-ion cathodes.