Crystallization of Lithium Carbonate from Aqueous Solution: New Insights into Crystal Agglomeration

In this work, crystal agglomeration of lithium carbonate has been studied from a new point of view. During an in situ crystallization experiment of lithium carbonate, a continuous structural transition from aggregate of precursors to pseudo-3-fold hexagram morphology of lithium carbonate was observed. It is proposed that the crystal agglomeration mainly results from these aggregates of precursors rather than collisions of well-formed crystals. Based on this especial agglomeration mechanism, some methods to prevent or promote agglomeration as required were investigated. Based on knocking experiments, the mass ratio of lithium carbonate spherulite was first proposed to quantify the degree of agglomeration. In addition, it was found that sodium hexametaphosphate can modify the morphology of the subunit of lithium carbonate, promote branching, and inhibit secondary nucleation, all of which greatly help to increase the degree of agglomeration. The results have implications for the production of battery-grade lithium carbonate and shed new light on other agglomeration mechanisms during industrial crystallization.