Preparation Of Battery Grade Lithium Carbonate By Hydrogenation And Decomposition

Lithium carbonate as an important basic raw material,has been widely used in the fields of energy,ceramics,medicine,metallurgy,etc.However,due to different uses,the purity of lithium carbonate should meet different requirements.The purity of lithium carbonate used in the cathode material of lithium ion battery must be greater than 99.5%and the contents of Ca and Mg in it should be less than 50 ppm.Therefore,it is of great significance to develop the low-cost preparation technology of battery-grade lithium carbonate.In this paper,battery-grade lithium carbonate was prepared by hydrogenation decomposition from industrial lithium carbonate,and its technological conditions and processes were discussed.The results are as follows:?1?For the commercial lithium carbonate with high contents of Ca and Mg,the complexation method was used to remove impurities.The suitable complexing agent was screened,and the optimal dosage,reaction time and temperature of the complexing agent was investigated.The contents of Ca and Mg decreased from 0.0129%and 0.0455%to 0.0054%and 0.0257%,respectively,and the removal rates were 58%%and 44%,respectively.?2?The effects of liquid-solid ratio,hydrogenation reaction conditions,impurity removing reagent,thermal decomposition reaction conditions and washing process on the purity and yield of lithium carbonate were studied.The optimized process conditions were obtained.The results show that the purity of lithium carbonate could be improved by increasing the liquid-solid ratio or adding EDTA complexing agent,and the thermal decomposition efficiency could be improved by increasing the thermal decomposition temperature or adding ethanol.At the optimum technological conditions,the purity of lithium carbonate reached 99.58%,and the contens of Ca and Mg were 0.0002%and0.0012%,respectively,which meet the requirements for the preparation of cathode materials of lithium ion batteries.?3?The circulating hydrogenation process of mother liquor was studied.The results show that the purity of lithium carbonate from the mother liquor with 7 hydrogenation circulation reached 99.52%,and the contents of Ca and Mg were 0.0001%and 0.0006%,which meet the requirements.By using circulating hydrogenation process,the liquid to solid ratio was reduced from 25:1 to 10:1 and the yield was increased from 71.70%to 92.10%,as compared to the single hydrogenation decomposition process.?4?Lithium salt was recovered from the tail liquid after circulating hydrogenation process.The effects of different precipitators and precipitation conditions on the recovery rate of lithium were investigated.The results showed that the recovery rate of lithium from tail liquid could reach more than 85%by using?NH₄?₃PO₄ precipitator.