KR102212995B1 - Preparation method and application of high-purity and proportional-mixed lithium salt - Google Patents

Abstract

The present invention provides a method for preparing a high-purity direct proportional mixed lithium salt and its application, including the following steps: purifying industrial lithium oxalate; Synthesis reaction: synthesis reaction of lithium oxalate and boron trifluoride to obtain a mixed reaction solution of lithium difluoro oxalate borate and lithium tetrafluoroborate, and purifying through a secondary purification filtration membrane; Concentration and crystallization of the reaction solution; Purifying and drying the mixed lithium salt. The product of the present invention is a positively mixed lithium salt in which the molar ratio of lithium difluoro oxalate borate and lithium tetrafluoroborate is 1:1, and can be used to prepare a non-aqueous electrolyte solution for lithium ion batteries, and further to manufacture a lithium ion battery. It is possible to avoid the complicated process of recrystallization of the prior art and the solid-liquid separation (filtration) operation after crystallization, improve product production rate and purity, simplify technical processes, and reduce production costs. have.

Description

Preparation method and application of high-purity and proportional-mixed lithium salt

The present invention relates to a technology for manufacturing a lithium ion battery, and more particularly, to a method for producing a high-purity direct proportional mixed lithium salt and its application.

The lithium battery electrolyte is a carrier for transporting ions in the battery. It is generally composed of a lithium salt and an organic solvent. The electrolyte acts to conduct ions between the positive electrode and the negative electrode of the lithium battery, and ensures that the lithium ion battery acquires advantages such as high voltage and high performance. The electrolyte is generally composed of raw materials such as high purity organic solvents, lithium electrolyte salts, and necessary additives, and is prepared under certain conditions and according to a certain ratio. Currently, the most frequently used electrolyte lithium salt is lithium hexafluorophosphate (LiPF ₆ ), and during the manufacturing process of the electrolyte solution, lithium hexafluorophosphate accounts for 50% to 70% of the electrolyte cost, mainly lithium ion. It is used for power batteries and lithium ion storage batteries, has advantages of good circulation efficiency, relatively good thermal stability, and high conductivity.

However, as an electrolyte lithium salt, lithium hexafluorophosphate still has disadvantages of relatively low anti-high temperature and hydrolysis properties, and the hydrogen fluoride it produces can damage battery components such as electrode materials and SEI membranes. And a decrease in the capacity of the lithium battery and a shortening of the service life. Using all the different physicochemical properties of different lithium salts, different types of lithium salt combinations can effectively improve the performance of lithium batteries by combining the advantages of each lithium salt.

Compared to lithium hexafluorophosphate, lithium tetrafluoroborate (LiBF ₄ ) has a relatively wider operating temperature range and stronger hydrolysis resistance; At the same time, the ion transition rate is relatively low, and the ability to form a membrane alone is relatively inferior. On the other hand, lithium difluorooxalate borate (LiODFB) is a new type of lithium salt, has excellent film-forming ability, has excellent thermal stability, high-low temperature performance, and electrochemical stability.

CN107698611A discloses a method for synthesizing an electrolyte lithium salt lithium difluoro oxalate borate, the method comprising: 1) reacting a silane compound with oxalic acid to obtain a condensate of silane oxalic acid; 2) reacting lithium tetrafluoroborate with a condensate of silane oxalic acid in a solvent to obtain a crude product; 3) Crude is recrystallized to obtain lithium difluoro oxalate borate.

CN101648963A discloses a synthetic process for simultaneously obtaining lithium difluoro oxalate borate and lithium tetrafluoroborate with excellent performance. The method includes: 1) a compound containing fluorine, a compound containing boron. A compound, a lithium-containing compound, and an oxalic acid group-containing compound are reacted in a reaction medium at 0 to 100°C and a reaction pressure of 0.1 to 1 MPa, among which lithium element, fluorine element, boron element and oxalic acid radical ion Make the molar ratio of 2～3:5～6:2:1; Producing a reaction solution containing lithium difluoro oxalate borate and lithium tetrafluoroborate; 2) After preliminary separation for lithium difluoro oxalate borate and lithium tetrafluoroborate in the reaction solution, lithium difluoro oxalate borate and lithium tetrafluoroborate can be extracted. Performing additional extraction and separation using a solvent; 3) performing recrystallization and vacuum drying, respectively, to obtain battery grade lithium difluoro oxalate borate and lithium tetrafluoroborate.

In the existing process, lithium tetrafluoroborate has a structure similar to lithium difluoro oxalate borate, and the two solutions have a relatively high viscosity, making it relatively difficult to separate them, and for equipment and technology. The required value is relatively high, the purity of both mixed salts obtained by production is relatively low, and this parameter greatly increases the cost of the mixed salt electrolyte. Therefore, there is a need to improve the prior art.

An object of the present invention is to provide a method for preparing a high-purity direct proportional mixed lithium salt and its application, employing industrial grade lithium oxalate as a raw material, and including processes such as purification, synthesis, and concentration. , The product is a positively mixed lithium salt in which the molar ratio of lithium difluoro oxalate borate and lithium tetrafluoroborate is 1:1, and can be used in the manufacture of lithium ion batteries, a complicated process of recrystallization by the prior art, and The solid-liquid separation (filtration) operation after crystallization can be avoided, the product production rate and purity can be improved, the process process can be simplified, and the production cost can be lowered.

In order to achieve the above object, the technical solution adopted by the present invention is as follows.

In a method for producing a high-purity direct proportional mixed lithium salt, the method comprises:

(1) Purification of lithium oxalate:

Pure water was added to industrial lithium oxalate and stirred to prepare a lithium oxalate suspension; An aqueous solution of a metal chelating agent was added to the lithium oxalate suspension, stirred for 30 minutes, and filtered to obtain a lithium oxalate solid; Washing with ultra-pure water, filtering the lithium oxalate solid 3-5 times, washing, filtering, and drying with ethanol to obtain a purified lithium oxalate solid white powder. step;

(2) synthesis reaction:

During stirring, lithium oxalate was added to an organic solvent (manufactured lithium oxalate suspension), and boron trifluoride was added dropwise to the prepared lithium oxalate suspension, so that the prepared lithium oxalate suspension was transparent. To obtain a mixed reaction solution of lithium difluoro oxalate borate and lithium tetrafluoroborate by continuously stirring until the reaction is completed, and a secondary purification filtration membrane Performing purification through the process;

(3) Concentration and crystallization of the reaction solution:

After concentrating a mixed reaction solution of purified lithium difluoro oxalate borate and lithium tetrafluoroborate in vacuo, crystallization was performed, and a crystal crude product of the mixed lithium salt (crude product) Obtaining a;

(4) Purification and drying of mixed lithium salt:

After washing the crystallized crude product using a poor solvent such as lithium difluoro oxalate borate and lithium tetrafluoroborate, the upper layer or the lower layer ( Remove the brown solution of the lower layer), continuously add the poor solvent, repeat this 3-4 times, vacuum-dry the solid until the upper or lower layer solution becomes transparent, and dry the solid in direct proportion to the high purity lithium salt ( Obtaining a molar ratio of lithium difluoro oxalate borate and lithium tetrafluoroborate of 1:1); Includes.

During the washing process, the crystallized solid gradually changes from a viscous state to a fluffy state, and the color gradually changes from light brown to white.

Based on the above solution, when purifying the lithium oxalate, the metal chelating agent is ethylenediaminetetraacetic acid (EDTA), and the drying temperature is 120°C.

Based on the above solution, in the synthesis reaction, the solvent is dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, acetonitrile, tetrahydrofuran ( tetrahydrofuran), toluene, ethyl acetate, ethylene glycol dimethyl ether, ether, dimethylformamide or acetone, and the reaction temperature is 70 -90°C and reaction time is 10-24 hours.

Based on the above solution, the process of manufacturing the secondary purification filtration membrane is: ethanol, polyethylene glycol diacrylate, 1'-(methylene-di-4,1-phenylene)bis[2 -Hydroxy-2-methyl-1-propanone], trifluoromethanesulfonic acid scandium (III) (Scandium (III) trifluoromethanesulfonate), 2- (3-nitro-2-pyridine) dimethyl malonate (Dimethyl malonate) , Potassium benzofuran-2-trifluoroborate was added to the reactor in proportion to the mass ratio 100:100-150:4-10:0.1-0.3:0.1-0.4:0.2-0.5, and , Stirring for 60-150 minutes to allow nitrogen to pass through at a constant temperature of 60-80°C, and after dropping the mixture on a glass plate, a quartz glass plate was covered above the mixture, and the thickness of the mixture was controlled to be 100-300 μm, After 30-120 seconds of UV irradiation, 6-24 hours of acetone washing, and static drying, an auxiliary purification filtration membrane was obtained.

Based on the above measures, the degree of vacuum when concentrating the above-described reaction solution is -0.01 MPa, and the temperature is 60-90°C; The temperature at the time of crystallization is -20°C.

Based on the above solution, when purifying the mixed lithium salt, the defective solvent is a halogenated alkane having a low boiling point, a non-polar to weak polar organic solvent, or a mixed organic solvent of both; During vacuum drying, the degree of vacuum is -0.01 MPa and the temperature is 80-100°C.

Based on the above solution, the halogenated alkane having a low boiling point is carbon tetrachloride, trichloromethane, dichloromethane, dichloroethane, or chloropropane. And, the non-polar to weakly polar organic solvent is cyclohexane, nucleic acid (N-hexane), benzene (benzene), pentane (pentane) or petroleum ether (Petroleum ether).

A kind of non-hydrolyzed electrolyte for a lithium ion battery contains a high-purity positively proportional mixed lithium salt having a mass content of 0.5%-20%.

A kind of lithium ion battery is a non-hydrolyzed electrolyte for lithium ion batteries containing a high-purity positively proportional mixed lithium salt with a mass content of 0.5%-20%, and dried 4.2v nickel: cobalt: manganese. ) In an NCM/graphite soft pack battery with a molar ratio of 6:2:2, and the existing lithium ion manufacturing technology (45℃ shelf, high temperature fixture) It is manufactured through formation and secondary sealing process).

The present invention employs industrial grade lithium oxalate as a raw material to reduce industrial production cost, and for this reason, purification of lithium oxalate is required. If the metal ions in industrial grade lithium oxalate exceed the standard, soluble metal ions (e.g. Na ⁺ , K ^+, etc.) can be washed with ethanol, and other soluble metal ions can be removed during the subsequent cleaning process. ; However, insoluble metal ions (eg, Ca ²⁺ ) need to be removed by washing with a chelating agent (eg, EDTA, etc.).

Advantageous effects of the present invention are as follows.

1) The present invention reduces the separation and purification process of lithium difluoro oxalate borate and lithium tetrafluoroborate, greatly reducing the production process and reducing cost;

2) The present invention provides a method of purifying a kind of mixed lithium salt, thereby improving the purity and production rate of the mixed lithium salt, allowing the prepared mixed lithium salt to be directly applied in lithium ion batteries, and reducing the cost. ;

3) 1:1 positively proportional mixed lithium salt of the present invention greatly improves the room temperature and high temperature circulation performance of lithium ion batteries, and has very excellent application potential in the field of replacing lithium hexafluorophosphate; Furthermore, by adding LiODFB or LiBF ₄ alone, mixed lithium salts of different ratios can be prepared, and costs can be reduced by applying various electrolyte combinations;

4) The present invention adopts industrial grade lithium oxalate and, through purification, prepares a mixed lithium salt, satisfies the electrical properties, and further reduces the cost.

1 is an ¹¹ B NMR spectrogram of a mixed lithium salt according to a method for preparing Example 1 of the present invention.
Figure 2 is a ¹⁹ F NMR spectrogram of the mixed lithium salt of the manufacturing method of Example 1 of the present invention.
3 is a ¹³ C NMR spectrogram of a mixed lithium salt in the preparation method of Example 1 of the present invention.
FIG. 4 is a performance diagram of a normal temperature (25° C.) circulation (100 cycles) of an electrolyte solution containing a mixed lithium salt according to the manufacturing method of Example 1 of the present invention.
5 is a high temperature (45° C.) circulation (100 cycles) performance diagram of an electrolyte solution containing a mixed lithium salt according to the manufacturing method of Example 1 of the present invention.
6 is an IR spectrogram of an auxiliary purification filtration membrane of the manufacturing method of Example 1 of the present invention.

Hereinafter, a technical solution of the present invention will be described with reference to the drawings and embodiments.

See Example 1, FIGS. 1-6:

The present invention provides a method for preparing a high-purity direct proportional mixed lithium salt, the manufacturing method,

(1) Purification of lithium oxalate:

Into 150 g of industrial lithium oxalate, ultra-pure water was added and stirred to prepare a lithium oxalate suspension; 0.4 g of ethylenediaminetetraacetic acid (EDTA) was weighed and dissolved in a small amount of ultrapure water; The EDTA aqueous solution was added to the lithium oxalate suspension, stirred for 30 minutes, and then filtered to obtain a lithium oxalate solid; Washing with ultrapure water, filtering the lithium oxalate solid three times, and finally washing with ethanol, filtering, and drying at 120°C to obtain a purified lithium oxalate solid white powder (96wt%) ;

(2) Synthesis reaction:

500 mL of dimethyl carbonate (DMC) was added to a three neck reaction flask, and 102 g of lithium oxalate was added while stirring strongly; The temperature was raised to 85° C. and stirred for 1 hour to prepare a lithium oxalate suspension; 284 g of boron trifluoride was weighed and gradually dropped into the lithium oxalate suspension by one drop during stirring, so that the dropping time was 2 hours; After the dropping operation was completed, the suspension was changed to be transparent, and stirred for 22 hours to react, obtaining a mixed reaction solution of lithium difluoro oxalate borate and lithium tetrafluoroborate, and then passed through an auxiliary purification filtration membrane. Performing purification;

(3) Concentration and crystallization of the reaction solution:

Purified lithium difluoro oxalate borate and lithium tetrafluoroborate mixture reaction solution was concentrated in vacuum under conditions of -0.01 MPa at a vacuum level and a temperature of 80°C, and then crystallized by placing a reaction bottle at -20°C. Proceeding to, obtaining a crystallization crude product (crude product) of the mixed lithium salt;

(4) Purification and drying of mixed lithium salt:

The reaction bottle after crystallization was obtained, for a viscous solid-liquid system, 200 mL of carbon tetrachloride was added to the reaction bottle, thoroughly stirred, and then the lower layer brown carbon tetrachloride solution was removed, and repeated. Washing 4 times and repeating until the lower carbon tetrachloride solution becomes a transparent solution.At this time, the upper crystallization solid changes from brown to a pure white solid, and carbon tetrachloride is removed by filtration, and a vacuum degree of -0.01 MPa, And drying for 24 hours under conditions of 100° C. to obtain a high-purity positively proportional mixed lithium salt (a molar ratio of lithium difluoro oxalate borate and lithium tetrafluoroborate is 1:1).

The obtained solid product was subjected to ¹⁹ F NMR, ¹¹ B NMR, and ¹³ C NMR analysis (refer to FIGS. 1 to 3, respectively), and the final product had a molar ratio of lithium difluoro oxalate borate and lithium tetrafluoroborate. It is a 1: 1 mixed lithium salt (NMR integral area calculation). The production rate is 85.6%, the purity is 99.1% (NMR characteristic), the moisture is 120ppm, the acidity is 200ppm, the insoluble matter is 102ppm, and the turbidity is 1.5.

Further, the manufacturing process of the secondary purification filtration membrane is: ethanol, polyethylene glycol diacrylate, 1,1'-(methylene-di-4,1-phenylene)bis[2-hydroxy-2-methyl-1- Propanone], trifluoromethanesulfonic acid scandium (III), 2-(3-nitro-2-pyridine)dimethyl malonate, potassium benzofuran-2-trifluoroborate in a mass ratio of 100:100:7:0.1: Into the reactor at a ratio of 0.1:0.2, stir for 100 minutes to allow nitrogen to pass under a constant temperature of 70°C, drop the mixture on a glass plate, cover the upper part of the mixture with a quartz glass plate, and control the mixture to a thickness of 100 μm. , UV irradiation for 75 seconds, acetone washing for 15 hours, and static drying to obtain the secondary purification filtration membrane.

For related features of the product of this example, refer to Figs. 1 to 6 together: Fig. 1 is an ¹¹ B NMR spectrogram of the mixed lithium salt prepared by this example; 2 is a ¹⁹ F NMR spectrogram of the mixed lithium salt prepared by this example; 3 is a ¹³ C NMR spectrogram of a mixed lithium salt prepared by this example; Figure 4 is a room temperature (25 ℃) circulation (100 cycles) performance of the electrolyte solution containing the mixed lithium salt prepared by the present embodiment; 5 is a high temperature (45° C.) circulation (100 cycles) performance diagram of an electrolyte solution containing a mixed lithium salt prepared by the present example; 6 is an IR spectrogram of the auxiliary purification filtration membrane prepared in Example 1. Based on the results, the following conclusions can be drawn.

And 1,: (1) ₄ LiODFB and LiBF there is only one boron atom is present, and thus ¹¹ B NMR spectrogram appear, but only a single peak is formed on an area ratio of the two peaks in the ¹¹ B NMR spectrogram 1 It can be determined that the molar ratio of LiODFB and LiBF ₄ is 1:1; According to the same principle, the chemical environment of the boron atoms in LiODFB is the same, and therefore, the chemical shifts indicated by the ¹⁹ F NMR spectrogram are the same, but the chemical environments of the boron atoms in LiBF ₄ are also the same. Peaks appear on the same chemical shift, and through the ¹⁹ F NMR spectrogram, there is a chemical shift ratio of the two positions, which can prove that the molar ratio of LiODFB and LiBF ₄ is 1:1. This is the molar ratio of the reaction is generated LiODFB and LiBF ₄ 1: LiODFB and LiBF ₄ ratio of but one, the poor solvent used in the purification process does greenery for LiODFB and LiBF _4, This mixed salt after purification is not changed .

(2) There is only one peak in the ¹³ C NMR spectrogram, and for the peak of the carbon atom in LiODFB, the carbon atom in LiBF ₄ is not included, and thus the peak does not appear in the ¹³ C NMR spectrogram.

(3) As shown in FIG. 4, the mixed salt can greatly increase the circulation performance of the lithium ion battery at room temperature (25° C.), and when the added amount is 1.5% and 3%, the effect is best.

(4) As shown in Fig. 5, the mixed salt can greatly increase the high-temperature (45° C.) circulation performance of the lithium ion battery, and when the addition amount is 1.5% and 0.5%, the effect is best; The results of storage at 60°C for 9 days show that the addition of mixed salt effectively suppresses gas formation, and the addition of 1.5% can improve the capacity retention rate from 79.8% to 86.67%, and the corresponding capacity recovery rate from 82.04% to 88.88% Indicates that it can be improved.

This kind of mixed lithium salt has a very great advantage in terms of cost and effect, and has a very great application potential in the field of a major salt of an electrolytic nucleus replacing lithium hexafluorophosphate.

(5) Figure 6 shows the chemical composition of the secondary purification filtration membrane, 907 and 1030 are the characteristic rods of the sulfuric acid group, 1260 is the characteristic rod of the CS key, and trifluoromethanesulfonic acid scandium (III) participates in the reaction Explain that it entered the absorption film, and 1500-1650 are the characteristic rods of the nitro group, 1576, 1468, and 1434 are the characteristic absorption rods of pyridine rings, 994 are the pyridine ring curved vibration absorption rods, and 1700 is O= C-0 strong absorption rod, explaining that 2-(3-nitro-2-pyridine)dimethyl malonate participated in the reaction and entered the absorption film, 1600 is a benzene ring skeleton characteristic rod, 900 Is a benzene ring CH curved vibration rod, 1000 is a CF key characteristic rod, explain that potassium benzofuran-2-trifluoroborate participated in the reaction and entered the absorption film.

Using the mixed lithium salt prepared in this example, a lithium ion battery non-aqueous electrolyte was prepared: in a glove box, vinyl carbonate (EC), ethyl methyl carbonate (EMC) ) And diethyl carbonate (DEC) in a mass ratio of 30:45:25, lithium hexafluorophosphate was added to dissolve it, and an electrolyte solution having a lithium hexafluorophosphate concentration of 1M was prepared. do. Thereafter, the mixed lithium salt samples prepared in Examples having mass values of 0.5%, 1.0%, 1.5% and 3%, respectively, are added to the electrolyte.

The mixed non-aqueous electrolytic nucleus for lithium ion batteries was injected into a sufficiently dried 4.2V NCM (nickel: cobalt: manganese = 6:2:2)/graphite soft pack battery, placed at 45°C, high temperature immobilized formation and secondary Through processes such as sealing, the battery performance is measured.

1) Room temperature circulation performance:

Under room temperature (25°C) conditions, the lithium ion battery is charged to 4.2V at 1C constant flow and constant pressure, and then discharged to 3.0V under 1C constant current conditions. After 100 cycles of charge and discharge, the capacity retention rate after 100 cycles is calculated.

2) High temperature circulation performance

Under high temperature (45°C) conditions, the lithium ion battery is charged to 4.2V at 1C constant current and constant voltage, and discharged to 3.0V at 1C constant current condition. After 100 cycles of charge and discharge, the capacity retention rate after 100 cycles is calculated.

Example 2:

The present invention provides a method for producing a high-purity direct proportional mixed lithium salt,

(1) Purification of lithium oxalate:

This step is the same as in Example 1;

(2) Synthesis reaction:

500 mL of ethyl acetate (EA) was added to a three-necked reaction flask, and 102 g of lithium oxalate was added while stirring strongly; The temperature was raised to 85° C. and stirred for 1 hour to prepare a lithium oxalate suspension; 284 g of boron trifluoride was weighed and gradually dropped into the lithium oxalate suspension by one drop during stirring, so that the dropping time was 2 hours; After the dropping operation was completed, the suspension was changed violently, and stirred for 22 hours to react, obtaining a mixed reaction solution of lithium difluoro oxalate borate and lithium tetrafluoroborate, and then passed through an auxiliary purification filtration membrane. Performing purification;

(3) concentration and crystallization of the reaction solution;

The purified lithium difluoro oxalate borate and lithium tetrafluoroborate mixture reaction solution was concentrated in vacuum under vacuum conditions of -0.01 MPa and a temperature of 60°C, and then crystallization proceeded by placing the reaction bottle under the conditions of -20°C, Obtaining a crystallization crude product of the mixed lithium salt;

(4) Purification and drying of mixed lithium salt:

Obtain the reaction bottle after crystallization, and add 200 mL of dichloromethane to the reaction bottle for a viscous solid-liquid system, and after sufficiently stirring, remove the upper brown dichloromethane solution, and repeat 4 Washed twice, and until the dichloromethane solution in the upper layer becomes a transparent solution, at this time, the crystallized solid in the lower layer changes from brown to a pure white solid, and dichloromethane is removed by filtration, and a vacuum degree of -0.01 MPa, 100° C. And drying for 24 hours under the conditions of to obtain a high purity mixed lithium salt (a molar ratio of lithium difluoro oxalate borate and lithium tetrafluoroborate is 1:1).

Further, the manufacturing process of the secondary purification filtration membrane is: ethanol, polyethylene glycol diacrylate, 1,1'-(methylene-di-4,1-phenylene)bis[2-hydroxy-2- Methyl-1-propanone], trifluoromethanesulfonic acid scandium (III), 2-(3-nitro-2-pyridine) dimethyl malonate, potassium benzofuran-2-trifluoro borate, Into the reactor at a mass ratio of 100:125:7:0.2:0.25:0.35, stir for 120 minutes to allow nitrogen to pass through at a constant temperature of 80°C, drop the mixture onto a glass plate, and cover a quartz glass plate above the mixture, The thickness of the mixture is controlled to be 200 μm, UV irradiation is performed for 120 seconds, acetone washing is performed for 20 hours, and the auxiliary purification filtration membrane can be obtained after static drying.

The obtained solid was subjected to ¹⁹ F NMR, ¹¹ B NMR, and ¹³ C NMR analysis, and the final product was a mixed lithium salt in which the molar ratio of lithium difluoro oxalate borate and lithium tetrafluoroborate was 1:1 (NMR integral Area calculation). The production rate is 87.6%, the purity is 99.9% (NMR characteristic), the moisture is 112 ppm, the acidity is 148 ppm, the insolubles are 95 ppm, and the turbidity is 1.5.

Example 3:

The present invention provides a method for preparing a high-purity direct proportional mixed lithium salt,

(1) Purification of lithium oxalate:

This step is the same as in Example 1;

(2) Synthesis reaction:

500 mL of acetonitrile was added to a three-necked reaction flask, and 102 g of lithium oxalate was added while stirring strongly; The temperature was raised to 85° C. and stirred for 1 hour to prepare a lithium oxalate suspension; 284 g of boron trifluoride was weighed and gradually dropped into the lithium oxalate suspension by one drop during stirring, so that the dropping time was 2 hours; After the dropping operation was completed, the suspension was changed to be transparent, and stirred for 22 hours to react, obtaining a mixed reaction solution of lithium difluoro oxalate borate and lithium tetrafluoroborate, and then passed through an auxiliary purification filtration membrane. Performing purification;

(3) Concentration and purification of the reaction solution:

The purified lithium difluoro oxalate borate and lithium tetrafluoroborate mixture reaction solution was concentrated in vacuum under vacuum conditions of -0.01 MPa and a temperature of 70° C., and then crystallization proceeded with the reaction bottle under the conditions of -20° C., Obtaining a crystallization crude product of the mixed lithium salt;

(4) Purification and drying of mixed lithium salt:

Obtain the reaction bottle after crystallization, add 200 mL of cyclohexane to the reaction bottle for a viscous solid-liquid system, thoroughly stir, remove the upper brown cyclohexane solution, and wash repeatedly 4 times. And, until the upper brown cyclohexane solution becomes a transparent solution, at this time, the lower crystallization solid changes from brown to a pure white solid, and the cyclohexane is removed by filtration, and dried for 24 hours under conditions of -0.01 MPa vacuum and 100°C. And obtaining a high-purity positively proportional mixed lithium salt (a molar ratio of lithium difluoro oxalate borate and lithium tetrafluoroborate is 1:1).

Further, the manufacturing process of the secondary purification filtration membrane is: ethanol, polyethylene glycol diacrylate, 1,1'-(methylene-di-4,1-phenylene)bis[2-hydroxy-2- Methyl-1-propanone], trifluoromethanesulfonic acid scandium (III), 2-(3-nitro-2-pyridine) dimethyl malonate, potassium benzofuran-2-trifluoro borate, Into the reactor at a mass ratio of 100:150:10:0.3:0.4:0.5, stir for 150 minutes to allow nitrogen to pass through at a constant temperature of 78°C, drop the mixture on a glass plate, and cover a quartz glass plate above the mixture, The thickness of the mixture is controlled to be 300 μm, UV irradiation is performed for 120 seconds, acetone washing is performed for 24 hours, and the auxiliary purification filtration membrane is obtained after static drying.

The obtained solid was subjected to ¹⁹ F NMR, ¹¹ B NMR, and ¹³ C NMR analysis, and the final product was a mixed lithium salt in which the molar ratio of lithium difluoro oxalate borate and lithium tetrafluoroborate was 1:1 (NMR integral Area calculation). The production rate is 85.4%, the purity is 99.9% (NMR characteristic), the moisture is 65 ppm, the acidity is 127 ppm, the insoluble matter is 78 ppm, and the turbidity is 1.5.

Example 4:

The present invention provides a method of preparing a high-purity direct proportional mixed lithium salt, and is basically the same as Example 3, but differs in that all organic solvents are tetrahydrofuran during the synthesis reaction.

The obtained solid was subjected to ¹⁹ F NMR, ¹¹ B NMR, and ¹³ C NMR analysis, and the final product was a mixed lithium salt in which the molar ratio of lithium difluoro oxalate borate and lithium tetrafluoroborate was 1:1 (NMR integral Area calculation). The production rate is 86.2%, the purity is 98.4% (NMR characteristic), the moisture is 98 ppm, the acidity is 239 ppm, the insoluble matter is 184 ppm, and the turbidity is 1.5.

Example 5:

The present invention provides a method of preparing a high-purity direct proportional mixed lithium salt, and is basically the same as in Example 3, but the method of manufacturing an auxiliary purification filtration membrane is: ethanol, polyethylene glycol diacrylate, 1,1'-( Methylene-di-4,1-phenylene)bis[2-hydroxy-2-methyl-1-propanone], trifluoromethanesulfonic acid scandium (III), 2-(3-nitro-2-pyridine) di Methyl malonate and potassium benzofuran-2-trifluoroborate were added to the reactor in a mass ratio of 100:150:10:0.4:0.5, and stirred for 130 minutes to allow nitrogen to pass under a constant temperature of 75°C. , After dropping the mixture on a glass plate, a quartz glass plate was covered above the mixture, the thickness of the mixture was controlled to be 300 μm, UV irradiation was performed for 100 seconds, acetone washing was performed for 20 hours, and the auxiliary purification filtration membrane was obtained after static drying. The difference is that you can do it.

The obtained solid was subjected to ¹⁹ F NMR, ¹¹ B NMR, and ¹³ C NMR analysis, and the final product was a mixed lithium salt in which the molar ratio of lithium difluoro oxalate borate and lithium tetrafluoroborate was 1:1 (NMR integral Area calculation). The production rate is 86.1%, the purity is 98.7% (NMR characteristic), the moisture is 81 ppm, the acidity is 174 ppm, the insolubles are 91 ppm, and the turbidity is 1.5.

Example 6:

The present invention provides a method of preparing a high-purity direct proportional mixed lithium salt, and is basically the same as in Example 3, but the method of manufacturing an auxiliary purification filtration membrane is: ethanol, polyethylene glycol diacrylate, 1,1'-( Methylene-di-4,1-phenylene)bis[2-hydroxy-2-methyl-1-propanone], trifluoromethanesulfonic acid scandium (III), 2-(3-nitro-2-pyridine) di Methyl malonate and potassium benzofuran-2-trifluoroborate were added to the reactor in a mass ratio of 100:150:10:0.3:0.5, and stirred for 150 minutes to allow nitrogen to pass at a constant temperature of 78°C. , After dropping the mixture on a glass plate, a quartz glass plate was covered above the mixture, the thickness of the mixture was controlled to be 300 μm, UV irradiation was performed for 120 seconds, acetone washing was performed for 20 hours, and the auxiliary purification filtration membrane was obtained after static drying. The difference is that you can do it.

The obtained solid was subjected to ¹⁹ F NMR, ¹¹ B NMR, and ¹³ C NMR analysis, and the final product was a mixed lithium salt in which the molar ratio of lithium difluoro oxalate borate and lithium tetrafluoroborate was 1:1 (NMR integral Area calculation). The production rate is 85.6%, the purity is 98.9% (NMR characteristic), the moisture is 77 ppm, the acidity is 145 ppm, the insoluble matter is 91 ppm, and the turbidity is 1.5.

Example 7:

The present invention provides a method of preparing a high-purity direct proportional mixed lithium salt, and is basically the same as in Example 3, but the method of manufacturing an auxiliary purification filtration membrane is: ethanol, polyethylene glycol diacrylate, 1,1'-( Methylene-di-4,1-phenylene)bis[2-hydroxy-2-methyl-1-propanone], trifluoromethanesulfonic acid scandium (III), 2-(3-nitro-2-pyridine) di Methyl malonate and potassium benzofuran-2-trifluoroborate were added to the reactor in a mass ratio of 100:150:10:0.3:0.4, and stirred for 150 minutes to allow nitrogen to pass under a constant temperature of 75°C. , After dropping the mixture on a glass plate, a quartz glass plate was covered above the mixture, the thickness of the mixture was controlled to be 300 μm, UV irradiation was performed for 120 seconds, acetone washing was performed for 24 hours, and the auxiliary purification filtration membrane was obtained after static drying. The difference is that you can do it.

The obtained solid was subjected to ¹⁹ F NMR, ¹¹ B NMR, and ¹³ C NMR analysis, and the final product was a mixed lithium salt in which the molar ratio of lithium difluoro oxalate borate and lithium tetrafluoroborate was 1:1 (NMR integral Area calculation). The production rate is 85.6%, the purity is 98.8% (NMR characteristic), the moisture is 81 ppm, the acidity is 194 ppm, the insoluble matter is 93 ppm, and the turbidity is 1.5.

Comparative Example 1:

In a method for producing a high-purity direct proportional mixed lithium salt,

(1) Synthesis reaction:

500 mL of acetonitrile was added to a three-necked reaction flask, and 102 g of lithium oxalate was added while stirring strongly; The temperature was raised to 85° C. and stirred for 1 hour to prepare a lithium oxalate suspension; 284 g of boron trifluoride was weighed and gradually dropped into the lithium oxalate suspension by one drop during stirring, so that the dropping time was 2 hours; After the dropping operation is completed, the suspension is changed to be transparent, followed by stirring to react for 22 hours, and obtaining a mixed reaction solution of lithium difluoro oxalate borate and lithium tetrafluoroborate;

(2) Concentration and crystallization of the reaction solution:

Lithium difluoro oxalate borate and lithium tetrafluoroborate mixed reaction solution was concentrated in vacuum under vacuum conditions of -0.01 MPa and temperature of 70° C., and then crystallization was performed under conditions of -20° C. and mixed lithium Obtaining a salt crystallization crude product;

(3) Purification and drying of mixed lithium salt:

Obtain the reaction bottle after crystallization, add 200 mL of cyclohexane to the reaction bottle for a viscous solid-liquid system, thoroughly stir, remove the upper brown cyclohexane solution, and wash repeatedly 4 times. And, until the upper brown cyclohexane solution becomes a transparent solution, at this time, the lower crystallization solid changes from brown to a pure white solid, and the cyclohexane is removed by filtration, and dried for 24 hours under conditions of -0.01 MPa vacuum and 100°C. And obtaining a mixed lithium salt (a molar ratio of lithium difluoro oxalate borate and lithium tetrafluoroborate is 1:1).

The obtained solid was subjected to ¹⁹ F NMR, ¹¹ B NMR, and ¹³ C NMR analysis, and the final product was a mixed lithium salt in which the molar ratio of lithium difluoro oxalate borate and lithium tetrafluoroborate was 1:1 (NMR integral Area calculation). The production rate is 77.4%, and the purity is 85.1% (NMR characteristic).

The above embodiments are for illustrative purposes only, and do not limit the technical solutions of the present invention, and even though the above embodiments have been described in detail with respect to the present invention, those skilled in the art will respond: Modifications or equivalent substitutions of the present invention It will be understood that it is possible, but any modifications and local substitutions not departing from the spirit and scope of the present invention should be regarded as falling within the scope of the present invention.

Claims (9)

In a method for producing a high-purity direct proportional mixed lithium salt,
(1) Purification of lithium oxalate:
Pure water was added to industrial lithium oxalate and stirred to prepare a lithium oxalate suspension; An aqueous solution of a metal chelating agent was added to the lithium oxalate suspension, stirred for 30 minutes, and filtered to obtain a lithium oxalate solid; Washing with ultra-pure water, filtering the lithium oxalate solid 3-5 times, washing, filtering, and drying with ethanol to obtain a purified lithium oxalate solid white powder. step;
(2) synthesis reaction:
During stirring, lithium oxalate was added to an organic solvent (manufactured lithium oxalate suspension), and boron trifluoride was added dropwise to the prepared lithium oxalate suspension, so that the prepared lithium oxalate suspension was transparent. To obtain a mixed reaction solution of lithium difluoro oxalate borate and lithium tetrafluoroborate by continuously stirring until the reaction is completed, and a secondary purification filtration membrane Performing purification through the process;
(3) Concentration and crystallization of the reaction solution:
After concentrating a mixed reaction solution of purified lithium difluoro oxalate borate and lithium tetrafluoroborate in vacuo, crystallization was performed, and a crystal crude product of the mixed lithium salt (crude product) Obtaining a;
(4) Purification and drying of mixed lithium salt:
After washing the crystallized crude product by using a poor solvent such as lithium difluoro oxalate borate and lithium tetrafluoroborate, the upper layer ) Remove the brown solution of the lower layer or the lower layer, continuously add a poor solvent, wash 3-4 times, and vacuum dry the solid until the upper or lower layer solution becomes transparent, and the high purity is directly proportional. Obtaining a mixed lithium salt (the molar ratio of lithium difluoro oxalate borate and lithium tetrafluoroborate is 1:1);
Including,
The manufacturing process of the secondary purification filtration membrane is:
Ethanol, polyethylene glycol diacrylate, 1,1'-(methylene-di-4,1-phenylene)bis[2-hydroxy-2-methyl-1-propanone], Scandium (III) trifluoromethanesulfonate, 2- (3-nitro-2-pyridine) dimethyl malonate, potassium benzofuran-2- trifluoroborate (Potassium benzofuran) -2-trifluoroborate) was added to the reactor in proportion to the mass ratio of 100:100-150:4-10:0.1-0.3:0.1-0.4:0.2-0.5, and nitrogen was passed under a constant temperature of 60-80℃. After stirring for 60-150 minutes, the mixture was dropped on a glass plate, and the quartz glass plate was covered above the mixture, the thickness of the mixture was controlled to be 100-300 μm, UV irradiation was performed for 30-120 seconds, and acetone washing was performed 6- 24 hours, characterized in that to obtain a secondary purification filtration membrane after static drying,
Method for producing high purity positively proportional mixed lithium salt. The method of claim 1,
When the lithium oxalate is purified, the metal chelating agent is ethylenediaminetetraacetic acid, and the drying temperature is 120°C,
Method for producing high purity positively proportional mixed lithium salt. The method of claim 1,
In the synthesis reaction, the solvent is dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, acetonitrile, tetrahydrofuran, and toluene. , Ethyl acetate, ethylene glycol dimethyl ether, ether, dimethylformamide or acetone, the reaction temperature is 70-90°C, and the reaction time Characterized in that it is 10-24 hours,
Method for producing high purity positively proportional mixed lithium salt. delete The method of claim 1,
The degree of vacuum when the reaction solution is concentrated is -0.01 MPa, and the temperature is 60-90°C; The temperature at the time of crystallization is characterized in that -20 ℃,
Method for producing high purity positively proportional mixed lithium salt. The method of claim 1,
In the purification of the mixed lithium salt, the defective solvent is a halogenated alkane having a low boiling point, a non-polar to weak polar organic solvent, or a mixed organic solvent of both; The vacuum degree during vacuum drying is -0.01 MPa, and the temperature is 80-100°C,
Method for producing high purity positively proportional mixed lithium salt. The method of claim 6,
The halogenated alkane having a low boiling point is carbon tetrachloride, trichloromethane, dichloromethane, dichloroethane, or chloropropane,
The non-polar to weakly polar organic solvent, characterized in that cyclohexane (Cyclohexane), nucleic acid (N-hexane), benzene (benzene), pentane (pentane) or petroleum ether (Petroleum ether),
Method for producing high purity positively proportional mixed lithium salt. In a kind of non-hydrolyzed electrolyte for lithium ion batteries,
It is characterized in that it contains a high-purity direct proportional mixed lithium salt prepared by the method of any one of claims 1 to 3 and 5 to 7 having a mass content of 0.5%-20%,
Non-hydrolyzed electrolyte for lithium ion batteries. In a kind of lithium ion battery,
A non-hydrolyzed electrolyte for a lithium ion battery containing a high-purity direct proportional mixed lithium salt prepared by the method of any one of claims 1 to 3 and 5 to 7 having a mass content of 0.5%-20%, The dried 4.2v nickel: cobalt: manganese (molar ratio) of 6:2:2 was injected into an NCM/graphite soft pack battery, Characterized in that produced through the lithium ion manufacturing technology of,
Lithium ion battery.

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