Dynamics and mechanisms of flame spray pyrolysis of LiMn2O4 nanoparticles: A reactive molecular dynamics study

• Developed the first ReaxFF MD model for the entire FSP synthesis of LiMn 2 O 4 . • Revealed temperature-dependent divergence in Li and Mn behaviors during FSP. • Identified Mn-driven nucleation and Li’s passive incorporation into Mn-rich clusters. • Introduced iterative oxidative annealing to replicate post-FSP refinement processes. • Provided a computational approach to optimize scalable high-voltage cathodes. LiMn 2 O 4 is a promising cathode material for lithium-ion batteries. In this study, the synthesis of LiMn 2 O 4 nanoparticles via flame spray pyrolysis (FSP) is investigated using reactive force-field (ReaxFF) molecular dynamics simulations. The study provides a detailed atomic-level view of the reaction pathways throughout the FSP process, from precursor droplet evaporation to nucleation and the growth mechanisms of nanoparticles. Based on temperature and oxygen content profiles, the FSP process is divided into four distinct stages: evaporation and initial decomposition, combustion-driven oxidation, nucleation, and particle growth through accretion and agglomeration. In an oxidizing atmosphere, precursor evaporation occurs alongside oxidation reactions, with Li-containing precursors decomposing and diffusing more rapidly than Mn-containing precursors due to Li’s lower atomic mass and valence. At higher combustion temperatures ( T c ), Mn-containing species exhibit temperature-dependent reaction pathways, favoring oxidized intermediates such as MnO 2 and MnO 2 H, whereas Li follows a consistent reaction pathway across different T c values, with T c primarily affecting the intermediate concentrations. Nucleation is Mn-dominated, with Mn x O y H z (x, y, z > 0) frameworks forming and merging preferentially at higher T c , while Li is passively incorporated into Mn clusters or organic fragments. Early-stage clusters grow by molecular accretion before transitioning to agglomeration, where organic bonds facilitate the formation of soft agglomerates. By the end of the FSP process, nanoparticles containing Li and Mn oxides form, serving as precursors for crystallized LiMn 2 O 4 . Iterative oxidative annealing refines these amorphous nanoparticles into Li/Mn oxides, which contain local LiMn 2 O 4 spinel crystallites, consistent with experimental TEM observations.