Lithium Fluoride Crystallization via Purified Bicarbonate
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Solution Overview
Problem
The production of high-purity lithium electrolyte salts, such as LiPF6, LiFSI, and LiTFSI, is hindered by the need for high-purity lithium carbonate (Li2CO3) as a raw material, which is costly and requires extensive purification processes.
Innovation Solution
A method is disclosed for purifying lithium carbonate and controlling the particle size of lithium fluoride (LiF) produced from it. This involves converting lithium carbonate to lithium bicarbonate, performing ion exchange to remove impurities, and then reacting the purified lithium bicarbonate with hydrofluoric acid (HF) to yield LiF. The particle size of LiF is controlled by adjusting the addition rates and temperatures of the reactants.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional purification methods are used to produce high-purity Li2CO3, then the purity of lithium electrolyte salts is improved, but the production cost increases and the process complexity increases
Solution Approach 1:
The invention changes the chemical form of lithium from carbonate (Li2CO3) to bicarbonate (LiHCO3) through parameter change (adding CO2), which fundamentally alters the purification mechanism. LiHCO3 is soluble and forms a clear solution that can be filtered to remove insoluble impurities, whereas Li2CO3 is sparingly soluble and requires complex hot filtration. This parameter change enables purification of lower-grade Li2CO3 to achieve battery-grade purity without excessive cost increase
Solution Approach 2:
The invention extracts and removes insoluble impurities (such as aluminum, phosphorus, and other non-lithium contaminants) from the lithium bicarbonate solution through simple filtration. This extraction step occurs early in the process when impurities are still in the solid phase, separating them from the soluble LiHCO3. The filtered LiHCO3 solution is then concentrated and carbonated to produce high-purity Li2CO3, achieving purification without requiring the starting material to be initially high-purity
2Manufacturing precision
If conventional purification methods are used to produce high-purity Li2CO3, then the purity of lithium electrolyte salts is improved, but the process complexity increases
Solution Approach 1:
The invention changes the solubility parameter of lithium by converting Li2CO3 to LiHCO3 through carbonation. This parameter change transforms the system from a suspension (insoluble Li2CO3) to a clear solution (soluble LiHCO3), enabling simple filtration instead of complex hot filtration procedures. The clear LiHCO3 solution can be easily handled, concentrated, and converted back to Li2CO3, significantly simplifying the overall process flow
Solution Approach 2:
The invention establishes a continuous process where Li2CO3 is carbonated to LiHCO3, filtered to remove impurities, concentrated, and then carbonated again to regenerate high-purity Li2CO3. This continuous cycle of transformation and regeneration eliminates the need for batch-wise complex purification steps. The process maintains continuous flow of material through each stage, improving efficiency and reducing operational complexity compared to conventional batch methods
3Ease of manufacture
If lower-quality Li2CO3 is used as feedstock, then production cost is reduced, but the purity of lithium electrolyte salts deteriorates
Solution Approach 1:
The invention applies parameter change by converting Li2CO3 to LiHCO3, which fundamentally changes the purification mechanism. Lower-grade Li2CO3 containing insoluble impurities is carbonated to form soluble LiHCO3. The insoluble impurities remain as solids and are removed by simple filtration, while the soluble LiHCO3 passes through to subsequent purification and concentration steps. This parameter change enables the use of lower-cost feedstock while achieving battery-grade purity in the final product
Solution Approach 2:
The invention converts the harmful effect of insoluble impurities in lower-grade Li2CO3 into a beneficial separation mechanism. By carbonating Li2CO3 to LiHCO3, the desired lithium compound becomes soluble while the impurities remain insoluble. This reverses the typical problem where impurities are soluble and product is insoluble, allowing impurities to be easily removed by filtration. The insolubility of impurities, which is normally a problem, becomes the key to simple and effective purification
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The method enables the production of high-purity LiF with controlled particle sizes, which is essential for manufacturing high-purity lithium electrolyte salts. This approach allows the use of lower-quality lithium carbonate, reducing production costs while maintaining the required purity levels.
Implementation Method 1
Lithium carbonate (Li2CO3) is sparingly soluble in water (12.9 g/L at 20° C.) and so a slurry is first prepared. The slurry is then reacted in a continuous process with CO2 to generate lithium bicarbonate, LiHCO3
Implementation Method 2
Ion exchange is then used to remove heavier contaminating ions such as calcium and magnesium
Implementation Method 3
Finally, the LiHCO3 solution is decomposed to generate purified Li2CO3 solids that can be isolated by filtration
Implementation Method 4
The method comprises simultaneously adding aqueous LiHCO3 and HF to a reactor containing water. The method yields LiF crystals
Implementation Method 5
The method may further comprise centrifuging the aqueous LiHCO3 prior to the filtering, and adding a flocculant to the aqueous LiHCO3 prior to the centrifuging. The centrifugation and filtration process removes aluminium and phosphorus from the aqueous LiHCO3
Implementation Method 6
This includes filtering the aqueous LiHCO3 through a filter having a nominal pore size of about 1 μm or less prior to adding the aqueous LiHCO3 to the reactor. The centrifugation and filtration process removes aluminium and phosphorus from the aqueous LiHCO3
Data Source
AI summary
A method to make LiF crystals by simultaneously adding aqueous LiHCO3 and HF to a stirred reactor containing water or a solution of LiF. The method yields LiF crystals having a Dv50 particle size of from about 60 μm to about 90 μm.