Spherulitic growth and morphology control of lithium carbonate: the stepwise evolution of core-shell structures

In this paper, we demonstrate morphologies, controlling factors (temperature, supersaturation and additives) and formation processes of lithium carbonate (Li2CO3) spherulites. Li2CO3 crystals were synthesized via a reaction crystallization and the effect of supersaturation was studied by changing temperature, adding antisolvent and altering Li+ ions concentration. Star-like and flower-like polycrystalline particles were produced without additives. By addition of sodium hexametaphosphate (SHMP), spherical particles could be obtained composed of radially arranged crystallites and core-shell structure was evolved at lower temperature. Time-resolved experiments were performed to detect the nucleation time and morphological changes. It was found that SHMP strongly inhibited nucleation and induced noncrystallographic branching. Two formation mechanisms were proposed to illustrate the stepwise evolution of core-shell spheres under different conditions. In addition, sodium tripolyphosphate exhibits similar effects with SHMP, while polymaleic acid modulates a different spherulitic growth mode. These findings provide new insights into spherulitic growth and fabrication of spherical particles.