| With the rapid development of society and technology,people’s demand for clean energy and portable and mobile energy is increasing.As a new type of energy,lithium-ion battery is more and more important in our daily life and industrial applications.The rapid development of the lithium battery industry makes the demand quantity and quality of the battery-grade lithium carbonate increasing.Our country has abundant lithium resources in salt lakes,and developing and optimizing the salt lake lithium extraction technology will promotes the high-value utilization of salt lake resources and satisify the quantity and quality needs of lithium carbonate.The reactive crystallization process of lithium carbonate prepared by precipitation method contains two major processes:nucleation and growth.The nucleation and growth of lithium carbonate are difficult to control due to the fast reaction rate,resulting to the large particle size,non-uniformly dispersed particle size,and high impurity content of the obtained lithium carbonate,which cannot meet the demands of battery-grade lithium carbonate.Therefore,this thesis uses optimize the crystallization conditions and morphology control of the lithium carbonate using stepwise regulation,in order to meet the quality requirements of battery-grade lithium carbonate.That’s to use the lithium carbonate crystal metastable area obtained by the online measurement technology as a guide,the high gravity technology is used to strengthen the lithium carbonate reaction crystallization process,and PAT（Process Analytical Technology）monitors the growth process of the lithium carbonate crystal.After ultrasonic enhanced washing,it’s filtered and dried.Using stepwise regulation to prepare battery-grade lithium carbonate,the obtained lithium carbonate has small particle size,uniform particle size distribution,low impurity content,strong experimental operation,short cycle,The data is accurate and reliable.The detailed research results are as follows:1.Use real-time and online infrared and Raman analyzer to measure the solubility of lithium carbonate in salt solution,and use focused beam reflection measuring instrument to measure the super solubility of lithium carbonate in salt solution in real time.It is found that the small reactant feed rate,high reaction temperature,and suitable stirring rate will benefit to the formation of lithium carbonate nuclation during the reaction.2.High gravity technology was used to strengthen the reaction crystallization process,it is found that the the small particle size lithium carbonate with uniform distribution was obtained in the optimum reaction condition:reaction stability time is 100 s,the reaction temperature is 90℃,the high gravity field is 45 Hz,the feed rate is 345 m L·min-1,and the liquid concentration is 19.87 g·L-1.The lithium carbonate prepared by using sodium dodecylbenzene sulfonate（SDBS）as an additive is irregular flake agglomerates in microscopic appearance.3.Using PAT technology to monitor the growth process of lithium carbonate crystals in real time,it is found that when the stirring rate is 600 rpm,the aging temperature is 40°C,and the aging time is 1.0 h,the prepared lithium carbonate has a smaller particle size and a uniform particle size distribution.The microscopic morphology is irregular flake agglomerates.4.After washing 3 times with ultrasonic technology the particle size and purity of the prepared lithium carbonate can meet the standard requirements of battery-grade lithium carbonate.The d50is 7.21μm,the purity is 99.92%,the contents of impurity ions Na+,Cl-,Mg2+and K+are 248 ppm,28 ppm,21 ppm and 9 ppm,respectively;the finally obtained lithium carbonate has a uniformly distributed flake microscopic morphology. |
