Monitoring the morphology evolution of LiNi0.8Mn0.1Co0.1O2 during high-temperature solid state synthesis via in situ SEM

Abstract

The particle morphology determined by the sintering process is the director factor affecting the electrochemical performance of Ni-rich NMC cathode materials. To prepare the ideal NMC particles, it is of great significance to understand the morphological changes during sintering process. In this work, the morphology evolution of LiNi0.8Mn0.1Co0.1O2 (NMC811) synthesis at temperature ranging from 300–1080 °C were observed by in situ SEM. The uniform mixture of spherical Ni0.8Mn0.1Co0.1(OH)2 precursor and lithium sources (LiOH) was employed by high temperature solid-state process inside the SEM, which enables us to observe morphology changes in real time. The results show that synthetic reaction of LiNi0.8Mn0.1Co0.1O2 usually includes three processes: the raw materials’ dehydration, oxidation, and combination, accompanied by a significant reduction in particle size, which is important reference to control the synthesis temperature. As heating temperature rise, the morphology of mixture also changed from flake to brick-shaped. However, Ni nanoparticle formation is apparent at higher temperature ~1000 °C, suggesting a structural transformation from a layered to a rock-salt-like structure. Combining the in-situ observed changes in size and morphology, and with the premise of ensuring the morphology change from flakes to bricks, reducing the sintering temperature as much as possible to prevent excessive reduction in particle size and layered to a rock-salt structure transformation is recommended for prepare ideal NMC particles.