Study On Preparation Of Battery Grade Lithium Carbonate By Lithium Carbonate Produced From Salt Lake

In recent years, high quality lithium carbonate, with an increasing demand in energy and materials fields, especially in the field of electric vehicles, it has a bright prospects. The products of lithium are mainly originated from salt lake in the world. Currently there are several companies could produce lithium carbonate in Qinghai province, however, their products have some differences with battery grade lithium carbonate. There are very important significance on deepening development of salt lake lithium resources, improving the level of comprehensive utilization of salt lake resources and completing the industrial chain of Qinghai Salt Lake resources by study on the preparation of battery grade lithium carbonate.In this work, carbonization of lithium carbonate, ion exchange, decomposition, and the reaction crystallization process of lithium chloride（LiCl） and sodium carbonate（Na2CO3） were studied. The optimum conditions of the carbonization process are as follows: carbonization temperature is 20℃, the ratio of liquid to solid is 20: 1, stirring speed is 400 rpm, flow rate of CO₂ gas is 1.0L / min. D751 ion exchange resin has a better effect on purification of carbonation solution. In the reactive crystallization, Optimal conditions are as follows: reaction temperature is 70℃, Li+ concentration of carbonization solution is 8.5g/L, stirring speed is 500 rpm, and add seeds before reaction.Under these conditions, the purified lithium carbonate can achieve to the battery grade. On the other hand, stirring speed, add seed and additives can reduce the phenomenon of sticky wall. The reactive crystallization of Na2CO3 and LiCl was studied. Polyacrylic acid as, the reaction temperature and feeding mode could change crystal morphology; external field, add seed or add polyacrylic acid as an additive could reduce the agglomeration of lithium carbonate. The optimum conditions are obtained: reverse feeding, the additional amount of Na2CO3 is 110% of the theoretical amount, stirring speed is 600 rpm, the reaction temperature is 80℃, concentration of LiCl is 3.2mol/L. The purity of lithium carbonate, which are produced by salt lake brine under the optimal conditions of reactive crystallization, closed to the battery grade.