CN110964045A - Method for reducing acid value of lithium bis (oxalato) borate and lithium bis (oxalato) borate with low acid value - Google Patents
Method for reducing acid value of lithium bis (oxalato) borate and lithium bis (oxalato) borate with low acid value Download PDFInfo
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- CN110964045A CN110964045A CN201911292032.2A CN201911292032A CN110964045A CN 110964045 A CN110964045 A CN 110964045A CN 201911292032 A CN201911292032 A CN 201911292032A CN 110964045 A CN110964045 A CN 110964045A
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- borate
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- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07F—ACYCLIC, CARBOCYCLIC OR HETEROCYCLIC COMPOUNDS CONTAINING ELEMENTS OTHER THAN CARBON, HYDROGEN, HALOGEN, OXYGEN, NITROGEN, SULFUR, SELENIUM OR TELLURIUM
- C07F5/00—Compounds containing elements of Groups 3 or 13 of the Periodic System
- C07F5/02—Boron compounds
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Abstract
The invention discloses a method for reducing the acid value of lithium bis (oxalato) borate and lithium bis (oxalato) borate with low acid value, which is characterized in that a crude lithium bis (oxalato) borate is dissolved in a polar solvent, an acid chelating agent is added into the polar solvent, the mixture is stirred and reacts for 10-180 min, after the reaction is finished, the mixture is filtered, and after the solvent is removed from filtrate by evaporation, the filtrate is dried under reduced pressure to obtain the lithium bis (oxalato) borate with low acid value; the acid chelating agent is anhydrous inorganic calcium salt. The technical scheme provided by the invention has the beneficial effects that the defect of high acid value residue of the lithium bis (oxalato) borate product prepared by a conventional method is effectively overcome, and the water content and free acid residue in the product can be remarkably reduced.
Description
Technical Field
The invention belongs to the technical field of lithium ion battery electrolyte, and particularly relates to a method for reducing the acid value of lithium bis (oxalato) borate and lithium bis (oxalato) borate with a low acid value prepared by the method.
Background
The lithium ion battery has the advantages of high energy density, high output voltage, long cycle life, no memory effect, small environmental pollution and the like, is the secondary battery with the greatest attraction and development potential, and is also the first choice of power supplies of hybrid electric vehicles and pure electric vehicles. The electrolyte is one of the basic key materials of the lithium ion battery, and the performance of the electrolyte plays a decisive role in the electrolyte and the lithium ion battery. Lithium bis (oxalato) borate (LiBOB) as a novel electrolyte lithium salt has good chemical properties and stability, and the thermal decomposition temperature of the lithium bis (oxalato) borate can reach 300 ℃. The addition of lithium bis (oxalato) borate (LiBOB) can form a stable SEI film on a carbon cathode, prevent solvent molecules from being embedded, has higher conductivity and wider electrochemical window, can improve the stability and safety of the lithium ion battery, and prolongs the service life of the lithium ion battery.
At present, the preparation method of lithium bis (oxalato) borate mainly comprises a solid phase method and a liquid phase method, wherein oxalic acid, a boron source and a lithium source are adopted as reaction raw materials to generate lithium bis (oxalato) borate and water. Oxalic acid has certain solubility in an organic solvent and begins to sublimate at 100 ℃, so that unreacted raw material oxalic acid is easily entrained in a lithium bis (oxalato) borate product; in the conventional preparation method, the reaction product contains water, the water in the product is difficult to completely remove, and the water content is usually in the order of hundreds of ppm. And the existence of higher water content can cause partial hydrolysis of the lithium bis (oxalato) borate product to generate lithium oxalate or lithium hydrogen oxalate, boric acid, oxalic acid and the like, and the reaction formula is as follows:
LiB(C2O4)2+3H2O→LiOOCCOOH+H3BO3+H2C2O4
due to the reasons, the lithium bis (oxalato) borate prepared by the conventional method has a high acid value (calculated by oxalic acid) and is easy to exceed the standard. Cell industry application standards typically require no more than 100ppm, with high end users requiring acid numbers below 50ppm, and some even less than 20 ppm. Due to the harsh requirements of the industry, the application of the product in the lithium ion battery industry is partially limited.
Disclosure of Invention
1. Technical problem to be solved
Aiming at the problems that in the prior art, unreacted raw material oxalic acid is carried into a lithium bis (oxalato) borate product or a conventional preparation method is difficult to completely remove water in the product, and when higher water exists, the lithium bis (oxalato) borate product is partially hydrolyzed to generate oxalic acid, so that the acid value (calculated by oxalic acid) in the lithium bis (oxalato) borate product is higher and the lithium bis (oxalato) borate product is easy to exceed the standard, the invention aims to provide a method for reducing the acid value of lithium bis (oxalato) borate and low-acid-value lithium bis (oxalato) borate prepared by using the method, and the method is mild in reaction, simple in process, low in cost, low in energy consumption and suitable for.
2. Technical scheme
In order to achieve the purpose, the invention adopts the following technical scheme:
dissolving a lithium bis (oxalato) borate crude product in a polar solvent, adding an acid chelating agent into the polar solvent, stirring and reacting for 10-180 min, filtering after the reaction is finished, concentrating the filtrate under reduced pressure, recrystallizing and filtering, and drying in vacuum to obtain the lithium bis (oxalato) borate with a low acid value; the acid chelating agent is anhydrous inorganic calcium salt.
In a specific embodiment of the invention, the crude lithium bis (oxalato) borate is prepared by a lithium bis (oxalato) borate preparation process route with raw materials related to oxalic acid.
In a specific embodiment of the present invention, the polar solvent is selected from any one of acetonitrile, propionitrile, methyl acetate, ethyl acetate, propyl acetate, acetone, methyl ethyl ketone, 1, 4-dioxane, 1, 4-butyrolactone or tetrahydrofuran, or a combination of two or more thereof.
In a specific embodiment of the invention, the amount of the polar solvent is 3-10 times of the mass of the lithium bis (oxalato) borate, and the polar solvent can be properly adjusted according to the solubility of the lithium bis (oxalato) borate in different solvents, so that a crude product of the lithium bis (oxalato) borate can be fully dissolved.
In one embodiment of the invention, the polar solvent has a moisture content of not more than 0.1%, preferably less than 500ppm, more preferably less than 200 ppm.
In one embodiment of the invention, the anhydrous inorganic calcium salt is selected from any one of calcium chloride, calcium bicarbonate, calcium oxide or calcium hydroxide or a combination of two or more thereof
In one embodiment of the invention, the anhydrous inorganic calcium is calcium chloride.
In a specific embodiment of the invention, the addition amount of the anhydrous inorganic calcium is 0.01-1% of the mass of the lithium bis (oxalato) borate crude product.
In a specific embodiment of the invention, the addition amount of the anhydrous inorganic calcium is 0.01-0.5% of the mass of the lithium bis (oxalato) borate crude product.
In a specific embodiment of the invention, the addition amount of the anhydrous inorganic calcium is 0.1-0.3% of the mass of the lithium bis (oxalato) borate crude product.
The invention also provides lithium bis (oxalato) borate with low acid value, which is characterized in that the lithium bis (oxalato) borate with low acid value is prepared by the method, and the acid value is less than or equal to 20ppm calculated by oxalic acid.
3. Advantageous effects
The technical scheme provided by the invention has the following beneficial effects: the defect of high acid value residue of the lithium bis (oxalato) borate product prepared by the conventional method is effectively overcome, the water content and free acid residue in the product can be remarkably reduced, the reaction is mild, the process is simple, the cost is low, the energy consumption is low, and the method is suitable for industrial production. The acid chelating agent anhydrous calcium salt adopted by the invention can form stable calcium oxalate salt with oxalic acid in the lithium bis (oxalato) borate crude product, so that the calcium oxalate salt is easy to crystallize out from a solvent and is removed by conventional filtration. Meanwhile, the inorganic anhydrous calcium salt also has dehydration property, can effectively adsorb free moisture in the lithium bis (oxalato) borate crude product, and further prevents the product from exceeding the acid value due to hydrolysis. By adopting the technical scheme provided by the invention, the obtained lithium bis (oxalato) borate product not only can reduce the acid value residue to below 20ppm, but also can effectively remove water in the product, obviously improve the quality of the lithium bis (oxalato) borate product and meet the high requirements of the lithium battery industry.
Detailed Description
The present invention will be described in further detail with reference to specific examples, so that the advantages of the present invention will be more apparent. It should be understood that the description is intended for purposes of illustration only and is not intended to limit the scope of the present disclosure. The experimental procedures, in which specific conditions are not specified, in the following examples are generally carried out according to conventional conditions or according to conditions recommended by the manufacturers. Unless otherwise indicated, all parts are parts by weight and all percentages are percentages by weight.
Example 1
194g of a crude lithium bis (oxalato) borate having a water content of 260ppm and an acid value of 145ppm in terms of oxalic acid was put into a dry three-necked flask with stirring under nitrogen atmosphere, followed by adding ethyl acetate having a water content of 4 times the mass of 180ppm, and stirring and dissolving for 30 minutes. Then adding 19.4g of granular anhydrous calcium chloride, stirring in a closed environment to react for 10min, filtering, concentrating the filtrate under reduced pressure, recrystallizing, filtering, and drying in vacuum to obtain 186g of lithium bis (oxalato) borate product. The acid value was measured to be 12ppm and the water content was measured to be 65 ppm.
Example 2
194g of a crude lithium bis (oxalato) borate product having a water content of 120ppm and an acid value of 86ppm in terms of oxalic acid was charged into a dry three-necked flask with stirring under nitrogen atmosphere, followed by adding acetonitrile having a water content of 6 times by mass and a water content of 350ppm, and stirring and dissolving for 60 minutes. Then adding 0.2g of calcium oxide, stirring in a closed state for reaction for 180min, filtering, concentrating the filtrate under reduced pressure, recrystallizing, filtering, and drying in vacuum to obtain 178g of lithium bis (oxalato) borate product. The acid value was measured to be 8ppm and the water content was measured to be 62 ppm.
Example 3
200g of a crude lithium bis (oxalato) borate having a water content of 85ppm and an acid value of 50ppm in terms of oxalic acid was put into a dry three-necked flask with stirring under nitrogen atmosphere, followed by adding acetone having a water content of 3 times the mass of 500ppm, and stirring and dissolving for 30 minutes. Then 10g of calcium bicarbonate is added, the mixture is stirred in a closed manner and reacts for 90min, then the mixture is filtered, the filtrate is concentrated under reduced pressure, recrystallized and filtered, and vacuum drying is carried out, thus 185g of lithium bis (oxalato) borate product is obtained. The acid value was 5ppm and the water content was 52 ppm.
It will be appreciated that various alterations and modifications of the invention will occur to those skilled in the art upon reading the above teachings, and that such equivalents are intended to fall within the scope of the invention as defined by the appended claims.
Claims (10)
1. A method for reducing the acid value of lithium bis (oxalato) borate is characterized by comprising the following steps: dissolving the lithium bis (oxalate) borate crude product in a polar solvent, adding an acid chelating agent into the polar solvent, stirring and reacting for 10-180 min, filtering after the reaction is finished, concentrating the filtrate under reduced pressure, recrystallizing and filtering, and drying in vacuum to obtain the lithium bis (oxalate) borate with a low acid value; the acid chelating agent is anhydrous inorganic calcium salt.
2. The method of claim 1 for reducing the acid value of lithium bis (oxalato) borate, wherein: the polar solvent is selected from any one of acetonitrile, propionitrile, methyl acetate, ethyl acetate, propyl acetate, acetone, methyl ethyl ketone, 1, 4-dioxane, 1, 4-butyrolactone or tetrahydrofuran or a combination of two or more of the above.
3. The method of claim 2, wherein the acid value of lithium bis (oxalato) borate is reduced by: the dosage of the polar solvent is 3-10 times of the mass of the lithium bis (oxalato) borate.
4. The method of claim 2, wherein the acid value of lithium bis (oxalato) borate is reduced by: the polar solvent has a water content of not more than 0.1%, preferably less than 500ppm, more preferably less than 200 ppm.
5. The method of claim 1 for reducing the acid value of lithium bis (oxalato) borate, wherein: the anhydrous inorganic calcium salt is selected from any one of calcium chloride, calcium bicarbonate, calcium oxide or calcium hydroxide or the combination of two or more of the calcium chloride, the calcium bicarbonate, the calcium oxide or the calcium hydroxide.
6. The method of claim 1 for reducing the acid value of lithium bis (oxalato) borate, wherein: the anhydrous inorganic calcium is calcium chloride.
7. The method of claim 5 or 6, wherein the acid value of lithium bis (oxalato) borate is reduced by: the addition amount of the anhydrous inorganic calcium salt is 0.01-1% of the mass of the lithium bis (oxalato) borate crude product.
8. The method of claim 5 or 6, wherein the acid value of lithium bis (oxalato) borate is reduced by: the adding amount of the anhydrous inorganic calcium salt is 0.01-0.5% of the mass of the lithium bis (oxalato) borate crude product.
9. The method of claim 5 or 6, wherein the acid value of lithium bis (oxalato) borate is reduced by: the adding amount of the anhydrous inorganic calcium salt is 0.1-0.3% of the mass of the lithium bis (oxalato) borate crude product.
10. A lithium bis (oxalato) borate with a low acid value, which is characterized in that: the lithium bis (oxalato) borate with low acid value is prepared by the method for reducing the acid value of the lithium bis (oxalato) borate, which is disclosed by any one of claims 1 to 9, and the acid value of the lithium bis (oxalato) borate is less than or equal to 20 ppm.
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| CN102010436A (en) * | 2010-11-10 | 2011-04-13 | 兰州理工大学 | Method for preparing lithium difluoro(oxalato)borate |
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| CN103483368A (en) * | 2013-09-17 | 2014-01-01 | 上海璞泰来新材料技术有限公司 | Method for preparing lithium oxalyldifluoroborate |
| CN104447828A (en) * | 2014-12-05 | 2015-03-25 | 北京蓝海黑石科技有限公司 | Method for synthesizing and purifying lithium bis(oxalato)borate |
| CN109053786A (en) * | 2018-09-18 | 2018-12-21 | 天津金牛电源材料有限责任公司 | A kind of preparation method of di-oxalate lithium borate |
| CN109503635A (en) * | 2018-12-06 | 2019-03-22 | 东营石大胜华新能源有限公司 | A kind of di-oxalate lithium borate purification process |
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