Size effects of precursor droplets on lithium-based nanomaterial synthesis using flame spray pyrolysis

The initial size of precursor droplets is one of the few control parameters in flame spray synthesis of energy nanomaterials with profound but poorly understood effects. This study unravels the influence of the initial lithium precursor droplet size on the reaction kinetics and formation mechanism of lithium nanoparticles. The reactive molecular dynamics simulations are performed, followed by comprehensive analyses of the droplet's morphology and kinetic and potential energy evolutions, bond kinetics, gas decomposition and reaction pathways of synthesized lithium nanoparticles. The droplet volume keeps rising over time, accompanied by the gradual formation of a hollow structure, which can be interpreted by the predominant role of gas decomposition in shaping the droplet's morphology. As the droplet size increases, however, the explosion behaviour becomes less intense. Besides, more lithium atoms agglomerate to form larger lithium nanoparticles, as evidenced by the increased lithium bond number and reduced atomic mean squared displacements. The reaction pathways also suggest that randomly dispersed small lithium nanoparticles ultimately aggregate to form larger lithium clusters. When the ambient temperature is decreased, the initial droplet size has a more pronounced effect on the size of synthesized lithium clusters, primarily attributed to the reduced reactivity and increased stability of lithium nanoparticles.