Method and device for continuously preparing lithium difluoro (oxalato) borate and lithium difluoro (oxalato) borate solution

Abstract

The invention discloses a method and device for continuously preparing lithium difluoro (oxalato) borate and a lithium difluoro (oxalato) borate solution, and belongs to the technical field of electrolyte salt synthesis, the method comprises the following steps: continuously pumping chlorosilane and a first mixed solution formed by oxalate and an ester solvent into a first dynamic microchannel reactor, and carrying out a first reaction to obtain a reaction product, wherein the mass flow ratio of the first mixed solution to the chlorosilane is (4-10): 1; continuously pumping the reaction product into a second dynamic micro-channel reactor, continuously pumping a second mixed solution formed by lithium tetrafluoroborate and an ester solvent into the second dynamic micro-channel reactor, and carrying out a second reaction at a temperature of 20-70 DEG C and a rotating speed of 200-400 r / min to obtain a mixed reaction solution; and separating a reaction product in the mixed reaction liquid to obtain the lithium bis (fluoro) oxalato borate. According to the method for continuously preparing the lithium difluoro (oxalato) borate, the continuous production of the lithium difluoro (oxalato) borate can be realized, and the quality of the lithium difluoro (oxalato) borate is high.

Description

Technical Field

[0001] The present application belongs to the technical field of electrolyte salt synthesis, and specifically relates to a method, an apparatus, and a lithium difluorooxalatoborate solution for continuously preparing lithium difluorooxalatoborate. Background Art

[0002] Lithium bis(oxalato)borate (LiODFB) is an important, high-performance electrolyte additive for lithium-ion batteries. It combines the advantages of lithium bis(oxalato)borate and lithium tetrafluoroborate, exhibiting excellent electrochemical properties and thermal stability. It helps form a more stable SEI film on the anode surface, thereby improving the battery's high-temperature cycling and storage performance. Furthermore, the SEI film formed by LiODFB prevents the co-intercalation of electrolyte solvents (especially propylene carbonate) on the anode surface, preventing damage to the SEI film structure.

[0003] Currently, relevant technologies have proposed a synthetic route that uses oxalates, such as sodium oxalate, to react with chlorosilane to obtain oxalate silicone grease, and then reacts the oxalate silicone grease with lithium tetrafluoroborate to obtain lithium difluorooxalatoborate. This route is generally divided into two steps. In the first step, oxalate reacts with chlorosilane to generate oxalate silicone grease. In the second step, oxalate silicone grease reacts with lithium tetrafluoroborate to generate lithium difluorooxalatoborate. After the synthesis of oxalate silicone grease, the generated chloride salt, such as sodium chloride, will undergo a double decomposition reaction with the lithium tetrafluoroborate in the second step, resulting in high acidity of the reaction product and excessive chloride ion content. Therefore, it is generally necessary to separate the solid chloride salt, such as sodium chloride, otherwise the continuous production of lithium difluorooxalatoborate cannot be achieved. Summary of the Invention

[0004] The present application aims to address, at least to some extent, one of the technical problems in the related art. To this end, one object of the present application is to provide a method and apparatus for continuously preparing lithium difluorooxalatoborate, as well as a lithium difluorooxalatoborate solution. The method for continuously preparing lithium difluorooxalatoborate proposed in this application can achieve continuous production of lithium difluorooxalatoborate, improve production efficiency, and produce high-quality lithium difluorooxalatoborate.

[0005] In a first aspect, the present application proposes a method for continuously preparing lithium tetrafluoroborate oxalate, comprising continuously pumping a first mixed liquid formed by oxalate and an ester solvent and chlorosilane into a first dynamic microchannel reactor, performing a first reaction to obtain a reaction product, wherein the mass flow ratio of the first mixed liquid to the chlorosilane is (4-10):1; continuously pumping the reaction product into a second dynamic microchannel reactor, and continuously pumping a second mixed liquid formed by lithium tetrafluoroborate and an ester solvent into the second dynamic microchannel reactor, performing a second reaction at a temperature of 20°C-70°C and a rotation speed of 200 r / min-400 r / min to obtain a mixed reaction liquid; and separating the reaction product in the mixed reaction liquid to obtain lithium tetrafluoroborate oxalate.

[0006] According to the method for continuously preparing lithium bisfluorooxalate borate in an embodiment of the present application, a first dynamic microchannel reactor and a second dynamic microchannel reactor are used in combination, fully utilizing the tolerance of the dynamic microchannel reactor to solid substances, and the two dynamic microchannel reactors have high heat and mass transfer efficiency, high safety, and high reaction efficiency. However, in the two dynamic microchannel reactors, since the reaction time of the first reaction is longer and the reaction time of the second reaction is shorter, the reaction time of the two-step reaction is not matched, resulting in low production efficiency and poor quality of the product lithium bisfluorooxalate borate. Therefore, on the one hand, the present application controls the ratio of the reaction raw materials of the first reaction, shortens the reaction time of the first reaction, and achieves matching of the two reaction times in the first dynamic microchannel reactor and the second dynamic microchannel reactor. On the other hand, the temperature and speed of the second reaction are controlled. The above speed causes the reaction materials of the second reaction to separate into solid and liquid layers under the action of centrifugal force, so that solid chloride salts such as sodium chloride accumulate on the inner wall of the second dynamic microchannel reactor, reducing the probability of lithium tetrafluoroborate in the liquid material undergoing a double decomposition reaction with it, and the above reaction temperature causes the main reaction of the second step to proceed rapidly in the central cavity and match the working time of the first reaction. Furthermore, the solid-containing reaction liquid obtained by the first reaction in the first dynamic microchannel reactor does not need to separate chloride salts such as sodium chloride, and directly enters the second dynamic microchannel reactor for the second reaction. After the reaction, the separation is carried out uniformly, which can ensure the quality of the obtained lithium difluorooxalate borate; on the other hand, since the solvent used in the two-step reaction is an ester solvent, the ester solvent can dissolve the product lithium difluorooxalate borate, but is not easy to dissolve by-products such as sodium chloride, lithium chloride and sodium tetrafluoroborate, so an ester solvent solution of lithium difluorooxalate borate with qualified acidity and chloride ion content can be obtained. In summary, the method for continuous preparation of lithium difluorooxalate borate proposed in this application can realize the continuous production of lithium difluorooxalate borate, improve production efficiency, and the obtained lithium difluorooxalate borate is of high quality and low impurity content.

[0007] In some embodiments of the present application, the pressure of the first reaction and the second reaction is 0.5 MPa to 1 MPa. This allows for continuous production of lithium bis(fluorooxalatoborate), improves production efficiency, and produces lithium bis(fluorooxalatoborate) of high quality and low impurity content.

[0008] In some embodiments of the present application, the temperature of the first reaction is 50° C. to 120° C. Thus, continuous production of lithium bifluorooxalatoborate can be achieved, production efficiency is improved, and the obtained lithium bifluorooxalatoborate is of high quality and low impurity content.

[0009] In some embodiments of the present application, the mass proportion of oxalate in the first mixed solution is less than or equal to 20%. This allows for continuous production of lithium bifluorooxalatoborate, improves production efficiency, and produces lithium bifluorooxalatoborate of high quality and low impurity content.

[0010] In some embodiments of the present application, the mass proportion of lithium tetrafluoroborate in the second mixed solution is less than or equal to 20%. This allows for continuous production of lithium tetrafluoroborate, improves production efficiency, and produces lithium tetrafluoroborate of high quality and low impurity content.

[0011] In some embodiments of the present application, the ratio of the amount of oxalate silicone grease in the reaction product to the amount of lithium tetrafluoroborate in the second mixed solution is 1:(1-1.05). This allows for continuous production of lithium tetrafluoroborate oxalate, improving production efficiency and ensuring high-quality, low-impurity lithium tetrafluoroborate.

[0012] In some embodiments of the present application, the oxalate comprises at least one of sodium oxalate and potassium oxalate. Thus, continuous production of lithium bifluorooxalatoborate can be achieved, production efficiency is improved, and the produced lithium bifluorooxalatoborate is of high quality and low impurity content.

[0013] In some embodiments of the present application, the ester solvent includes at least one of dimethyl carbonate, ethyl methyl carbonate, and diethyl carbonate. This allows for continuous production of lithium bis(fluorooxalatoborate), improving production efficiency and ensuring high-quality lithium bis(fluorooxalatoborate) with low impurity content.

[0014] In some embodiments of the present application, the stirring speed of the first reaction is 200 rpm to 400 rpm. This allows for continuous production of lithium bis(fluorooxalatoborate), improves production efficiency, and produces lithium bis(fluorooxalatoborate) of high quality and low impurity content.

[0015] In some embodiments of the present application, the Reynolds number of the fluid in the first dynamic microchannel reactor is greater than or equal to 10000. Thus, continuous production of lithium bisfluorooxalatoborate can be achieved, production efficiency is improved, and the obtained lithium bisfluorooxalatoborate is of high quality and low impurity content.

[0016] In some embodiments of the present application, the first reaction time is 1 min to 30 min. Thus, continuous production of lithium bifluorooxalatoborate can be achieved, production efficiency is improved, and the obtained lithium bifluorooxalatoborate is of high quality and low impurity content.

[0017] In some embodiments of the present application, the Reynolds number of the fluid in the second dynamic microchannel reactor is greater than or equal to 15000. Thus, continuous production of lithium bisfluorooxalatoborate can be achieved, production efficiency is improved, and the prepared lithium bisfluorooxalatoborate is of high quality and low impurity content.

[0018] In some embodiments of the present application, the second reaction time is 1 min to 10 min. Thus, continuous production of lithium bifluorooxalatoborate can be achieved, production efficiency is improved, and the obtained lithium bifluorooxalatoborate is of high quality and low impurity content.

[0019] In some embodiments of the present application, the step of separating the reaction products from the mixed reaction liquid includes: flashing the mixed reaction liquid to obtain a solid-liquid mixture and a gas; and continuously centrifuging the solid-liquid mixture and separating and removing the solid to obtain a solution of lithium bifluorooxalatoborate and an ester solvent. This enables continuous production of lithium bifluorooxalatoborate, improves production efficiency, and produces high-quality lithium bifluorooxalatoborate with low impurity content.

[0020] In some embodiments of the present application, the flash evaporation temperature is 110° C. to 120° C. Thus, continuous production of lithium difluorooxalatoborate can be achieved, production efficiency is improved, and the obtained lithium difluorooxalatoborate is of high quality and low impurity content.

[0021] In some embodiments of the present application, the rotation speed of the continuous centrifugation is 60 rpm to 120 rpm. This allows for continuous production of lithium bifluorooxalatoborate, improves production efficiency, and produces lithium bifluorooxalatoborate of high quality and low impurity content.

[0022] In some embodiments of the present application, the flash evaporation pressure is 0.5 MPa to 1 MPa. This allows for continuous production of lithium bifluorooxalatoborate, improves production efficiency, and produces lithium bifluorooxalatoborate of high quality and low impurity content.

[0023] In some embodiments of the present application, the pressure of the continuous centrifugation is 0.5 MPa to 1 MPa. Thus, continuous production of lithium bifluorooxalatoborate can be achieved, production efficiency is improved, and the obtained lithium bifluorooxalatoborate is of high quality and low impurity content.

[0024] In a second aspect, the present application provides an apparatus for continuously preparing lithium difluorooxalatoborate, which is used to perform the method described in the first aspect of the present application. This apparatus enables continuous production of lithium difluorooxalatoborate, improves production efficiency, and produces high-quality lithium difluorooxalatoborate with low impurity content.

[0025] In a third aspect, the present application provides a lithium difluorooxalate borate solution, comprising lithium difluorooxalate borate and an ester solvent. The lithium difluorooxalate borate solution is prepared using the continuous preparation method for lithium difluorooxalate borate described in the first aspect of the present application. As a result, the lithium difluorooxalate borate solution has high production efficiency, high quality lithium difluorooxalate borate, and low impurity content.

[0026] In some embodiments of the present application, the mass of the lithium bis(fluorooxalatoborate) borate accounts for 10% to 35% of the total mass of the lithium bis(fluorooxalatoborate) borate solution. Thus, the production efficiency of the lithium bis(fluorooxalatoborate) borate solution is high, the lithium bis(fluorooxalatoborate) borate is high, and the impurity content is low.

[0027] In some embodiments of the present application, the mass proportion of lithium chloride based on the total mass of the lithium bis(fluorooxalatoborate) solution is less than or equal to 15 ppm. Thus, the production efficiency of the lithium bis(fluorooxalatoborate) solution is high, the lithium bis(fluorooxalatoborate) solution is high, and the impurity content is low.

[0028] In some embodiments of the present application, the mass proportion of tetrafluoroborate based on the total mass of the lithium bisfluorooxalatoborate solution is less than or equal to 15 ppm. As a result, the production efficiency of the lithium bisfluorooxalatoborate solution is high, the lithium bisfluorooxalatoborate is of high quality, and the impurity content is low.

[0029] Additional aspects and advantages of the present application will be given in part in the description below, and in part will become obvious from the description below, or will be learned through practice of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] The above and / or additional aspects and advantages of the present application will become apparent and easily understood from the description of the embodiments in conjunction with the following drawings, in which: Figure 1 This is a flow chart of a method for continuously preparing lithium difluorooxalatoborate according to one embodiment of the present application.

[0031] Figure 2 This is a structural diagram of an apparatus for continuously preparing lithium difluorooxalatoborate according to an embodiment of the present application.

[0032] Figure 3 This is a chromatographic detection chart of a solution of lithium difluorooxalatoborate and an ester solvent obtained according to the method of Example 1 of the present application.

[0033] Description of Figure Numbers: 1. Chlorosilane storage tank; 2. Oxalate storage tank; 3. First feed pump; 4. Second feed pump; 5. First dynamic microchannel reactor; 6. Lithium tetrafluoroborate tank; 7. Third feed pump; 8. Second dynamic microchannel reactor; 9. Flash tank; 10. Continuous centrifuge. DETAILED DESCRIPTION

[0034] The embodiments of the present application are described in detail below. The embodiments described below are exemplary and are intended to be used to explain the present application, but should not be understood as limiting the present application.

[0035] Lithium bis(oxalato)borate is an important high-performance electrolyte additive for lithium-ion batteries. It combines the advantages of lithium bis(oxalato)borate and lithium tetrafluoroborate, and has good electrochemical properties and thermal stability.

[0036] Existing methods for preparing lithium bis(fluorooxalatoborate) primarily involve synthesizing lithium tetrafluoroborate from lithium oxalate and boron trifluoride, followed by reacting lithium tetrafluoroborate with oxalic acid to obtain lithium bis(fluorooxalatoborate). This method involves the presence of corrosive materials such as boron trifluoride and oxalic acid during production, placing high demands on the reaction system, increasing equipment costs and maintenance difficulties. Furthermore, this reaction route involves a gas-liquid reaction, resulting in low reaction efficiency and the generation of large amounts of corrosive tail gas, making continuous production difficult.

[0037] Currently, related technologies have proposed a synthetic route that uses oxalates, such as sodium oxalate, to react with chlorosilanes to obtain oxalate silicone grease, which is then reacted with lithium tetrafluoroborate to obtain lithium difluorooxalatoborate. This route is generally divided into two steps. After synthesizing the oxalate silicone grease, it is necessary to separate solid chloride salts, such as sodium chloride. Otherwise, the sodium chloride and unreacted chlorosilanes will undergo a double decomposition reaction with the lithium tetrafluoroborate, resulting in high acidity and excessive chloride ion content in the reaction product. On the other hand, during the second step of the oxalate silicone grease reaction, lithium tetrafluoroborate and solvent are added, and after the reaction, they are evaporated and separated again. This route has the problems of a long solid-liquid reaction time in the first step, complex post-processing, and a mismatch between the working hours of the first and second fast reactions, resulting in low process efficiency and unstable product quality.

[0038] In view of this, the first aspect of this application proposes a method for continuously preparing lithium bifluorooxalatoborate. Figure 1 The above-mentioned method for continuously preparing lithium difluorooxalatoborate comprises: S1. Continuously pumping a first mixed solution formed by oxalate and an ester solvent and chlorosilane into a first dynamic microchannel reactor to perform a first reaction to obtain a reaction product, wherein the mass flow rate ratio of the first mixed solution to the chlorosilane is (4-10):1; S2, continuously pumping the reaction product into a second dynamic microchannel reactor, and continuously pumping a second mixed solution formed by lithium tetrafluoroborate and an ester solvent into the second dynamic microchannel reactor, and performing a second reaction at 20° C. to 70° C. to obtain a mixed reaction solution; S3. Separating the reaction product in the mixed reaction solution to obtain lithium difluorooxalatoborate.

[0039] The beneficial effects that can be achieved by the continuous preparation method of lithium difluorooxalatoborate proposed in this application are described in detail below: The present application provides a method for continuously preparing lithium tetrafluoroborate oxalocyanate, which uses a first dynamic microchannel reactor 5 and a second dynamic microchannel reactor 8 in combination, fully utilizing the tolerance of the dynamic microchannel reactor to solid substances, and the two dynamic microchannel reactors have high heat and mass transfer efficiency, high safety, and high reaction efficiency. However, in the two dynamic microchannel reactors, due to the long reaction time of the first reaction and the short reaction time of the second reaction, the reaction time of the two-step reaction is not matched, resulting in low production efficiency and poor quality of the product lithium tetrafluoroborate oxalocyanate. Therefore, the present application controls the ratio of the reaction raw materials of the first reaction, shortens the reaction time of the first reaction, and achieves matching of the reaction times of the two reactions in the first dynamic microchannel reactor and the second dynamic microchannel reactor. On the other hand, the temperature and speed of the second reaction are controlled. The above speed causes the reaction materials of the second reaction to separate into solid and liquid layers under the action of centrifugal force, so that solid chloride salts such as sodium chloride accumulate on the inner wall of the second dynamic microchannel reactor, reducing the probability of lithium tetrafluoroborate in the liquid material undergoing a double decomposition reaction with it. The above reaction temperature allows the main reaction of the second step to proceed rapidly in the central cavity and match the working time of the first reaction. Furthermore, the solid-containing reaction liquid obtained by the first reaction in the first dynamic microchannel reactor 5 does not need to separate chloride salts such as sodium chloride, and directly enters the second dynamic microchannel reactor 8 for the second reaction. After the reaction, the separation is carried out uniformly to ensure the quality of the obtained lithium difluorooxalate borate; on the other hand, since the solvent used in the two-step reaction is an ester solvent, the ester solvent can dissolve the product lithium difluorooxalate borate, but is not easy to dissolve by-products such as sodium chloride, lithium chloride and sodium tetrafluoroborate, so an ester solvent solution of lithium difluorooxalate borate with qualified acidity and chloride ion content can be obtained. In summary, the method for continuous preparation of lithium difluorooxalate borate proposed in this application can realize the continuous production of lithium difluorooxalate borate, improve production efficiency, and the obtained lithium difluorooxalate borate is of high quality and low impurity content.

[0040] It is understandable that for reactions containing solids (such as oxalates, chlorides, lithium tetrafluoroborate, etc.), general microreactors or pipeline reactors are prone to solid blockage and other problems. Therefore, the present application adopts a dynamic microchannel reactor, which is combined with an external jacket and internal stirring. The built-in stirring shaft rotates at high speed and has a heat exchange function. It is an option for continuous solid-liquid reactions and is not prone to solid blockage.

[0041] The temperature of the second reaction is 20°C to 70°C. For example, it can be 20°C, 40°C, 50°C, 70°C, etc. The temperature of the second reaction is controlled within the above range. The main reaction rate is not significantly affected within this temperature range, while the double decomposition reaction rate of chloride salts such as sodium chloride is extremely slow, and the product selectivity is higher than 99%, which is beneficial to improving the quality of lithium bifluorooxalatoborate and reducing the impurity content. At the same time, it can reduce the generation process of fluorosilanes, reduce the generation of bubbles that affect the average residence time of the materials, and ensure the efficient progress of the reaction.

[0042] The mass flow rate ratio of the first mixed liquid to the chlorosilane is (4~10):1, for example, it can be 4:1, 5:1, 7:1, 9:1, 10:1, etc. By controlling the mass flow rate ratio of the first mixed liquid to the chlorosilane within the above range, the molar ratio of oxalate such as sodium oxalate and chlorosilane can be achieved to be 1:(1.01~1.05), which promotes the complete reaction of sodium oxalate after the reaction, leaving a small amount of chlorosilane, and can ensure the full progress of the reaction while avoiding the formation of by-products.

[0043] The stirring speed of the second reaction is 200r / min~400r / min, for example, it can be 200r / min, 300r / min, 400r / min, etc. By controlling the stirring speed within the above range, the fluid therein can be in a turbulent state, thereby improving the mass transfer efficiency and reaction rate.

[0044] The advantages of the continuous preparation method of lithium difluorooxalatoborate proposed in this application are described in detail below: High heat and mass transfer efficiency: the first dynamic microchannel reactor 5 and the second dynamic microchannel reactor 8 can perform efficient temperature control in the reaction chamber, keep the liquid and solid moving in one direction under the high-speed rotation of the stirring paddle, reduce the back-mixing phenomenon, and ensure the average residence time of the reaction; when the second mixed liquid is added to the two dynamic microchannel reactors in series, the two-phase liquid is mixed in seconds in the dynamic microchannel reactor, the materials react quickly according to the molar ratio, the reaction selectivity for synthesizing lithium difluorooxalatoborate is high, and the double decomposition reaction is less.

[0045] High safety: The first and second dynamic microchannel reactors 5 and 8 have low liquid holding capacity and are capable of withstanding solid-liquid reaction conditions. Once the reaction begins, the blades force the solids into motion, eliminating the risk of solids clogging the equipment and causing overpressure. Heat exchange medium is present inside and outside the agitator shafts of the first and second dynamic microchannel reactors 5 and 8, ensuring precise material temperature control. Rapid material flow during agitation prevents localized overheating or hot spots.

[0046] High reaction efficiency: ester solvents are used in the reaction raw materials, and after the reaction, solid-liquid separation is performed to directly produce a solution of lithium difluorooxalatoborate dissolved in the ester solvent. The solution is compatible with the electrolyte solvent and does not require an additional configuration process, resulting in high production efficiency. The reaction time is short when synthesizing lithium difluorooxalatoborate, and the occurrence of double decomposition reactions between chloride salts such as sodium chloride and lithium tetrafluoroborate is low.

[0047] High product purity: Inorganic byproducts such as lithium chloride and ammonium tetrafluoroborate, produced by the reaction of chloride salts such as sodium chloride with lithium tetrafluoroborate, have low solubility in ester solvents. Simply drying the wet solids yields industrial-grade sodium chloride. However, the product, lithium difluorooxalateborate, has high solubility in ester solvents. Therefore, during solid-liquid separation, impurities enter the sodium chloride and are treated as industrial-grade sodium chloride. The lithium difluorooxalateborate solution dissolves in the ester solvent, leaving insoluble matter and chloride ions, and the acidity can be controlled.

[0048] In addition, the present invention can optimize the reaction conditions and further improve the purity and yield of the product. The reaction process has fewer steps, and the chloride ion and acidity of the lithium bifluorooxalatoborate solution product are controllable, thereby controlling the quality.

[0049] Specifically, taking sodium oxalate as an example, the reaction equation in the first dynamic microchannel reactor 5 is: Na2C2O4+2Si(CH3)3Cl→(Si(CH3)3)2C2O4+2NaCl.

[0050] The reaction equation in the second dynamic microchannel reactor 8 is: (Si(CH3)3)2C2O4+LiBF4→LiC2O4BF2+2Si(CH3)3F.

[0051] According to some specific embodiments of the present application, the pressure of the first reaction and the second reaction is 0.5MPa~1MPa. As an example, the pressure of the first reaction and the second reaction can be 0.5MPa, 0.6MPa, 0.7MPa, 0.8MPa, 0.9MPa, 1MPa, etc. Specifically, nitrogen can be used to increase the pressure of the first reaction and the second reaction to 0.5MPa~1MPa, and the pressure of the first reaction and the second reaction can be stabilized by a back pressure system to ensure that the reaction process of the two dynamic microchannel reactors is carried out under high pressure conditions, so as to promote the first dynamic microchannel reactor 5 and the second dynamic microchannel reactor 8 to react thoroughly, so as to improve the reaction efficiency and product purity, and improve the stability of the entire continuous preparation device for lithium bis(fluorooxalate)borate.

[0052] According to some specific embodiments of the present application, the temperature of the first reaction is 50°C to 120°C, for example, 50°C, 70°C, 90°C, 100°C, 120°C, etc. By controlling the temperature of the first reaction within the above range, the reaction temperature is relatively high, which can promote the rapid reaction of oxalates such as sodium oxalate and chlorosilane, control and shorten the reaction time, and can match the fast reaction of the second dynamic microchannel reaction, thereby achieving continuous production of lithium difluorooxalatoborate, improving production efficiency, and the quality of the obtained lithium difluorooxalatoborate is high.

[0053] According to some specific embodiments of the present application, in the first mixed liquid, the mass proportion of oxalate is less than or equal to 20%. For example, the mass proportion of oxalate can be 1%, 5%, 10%, 15%, 20%, etc. Controlling the mass proportion of oxalate within the above range can ensure the sufficient progress of the reaction while avoiding the formation of by-products.

[0054] According to some specific embodiments of the present application, the oxalate includes at least one of sodium oxalate and potassium oxalate. The above oxalate is easy to react with chlorosilane under heating conditions and has few side reactions.

[0055] According to some specific embodiments of the present application, the ester solvent includes at least one of dimethyl carbonate (DMC), ethyl methyl carbonate (EMC) and diethyl carbonate (DEC). The above ester solvent can dissolve the product lithium difluorooxalatoborate, but is not easy to dissolve by-products such as sodium chloride, lithium chloride and sodium tetrafluoroborate. Therefore, a solution of lithium difluorooxalatoborate in an ester solvent with qualified acidity and chloride ion content can be obtained. The obtained lithium difluorooxalatoborate has high quality and low impurity content.

[0056] According to some specific embodiments of the present application, the ester solvents used in the first mixed liquid and the second mixed liquid are exactly the same. For example, the first mixed liquid uses dimethyl carbonate and the second mixed liquid also uses dimethyl carbonate. In this way, a high-purity solution of lithium difluorooxalatoborate in an ester solvent can be obtained.

[0057] According to some specific embodiments of the present application, the stirring speed of the first reaction is 200r / min~400r / min, for example, it can be 200r / min, 300r / min, 400r / min, etc. By controlling the stirring speed within the above range, the fluid therein can be in a turbulent state, thereby improving the mass transfer efficiency and reaction rate.

[0058] According to some specific embodiments of the present application, the Reynolds number of the fluid in the first dynamic microchannel reactor 5 is greater than or equal to 10,000. For example, the Reynolds number can be 10,000, 50,000, 60,000, 70,000, 80,000, 90,000, 100,000, 150,000, etc. By controlling the Reynolds number of the fluid in the first dynamic microchannel reactor 5 within the above range, the fluid therein can be in a turbulent state, thereby improving the mass transfer efficiency and reaction rate.

[0059] According to some specific embodiments of the present application, the time of the first reaction is 1 min to 30 min, for example, it can be 1 min, 5 min, 10 min, 20 min, 30 min, etc. Controlling the time of the first reaction within the above range can ensure the sufficient progress of the reaction, while avoiding the formation of by-products caused by excessive residence time, so that the obtained lithium difluorooxalatoborate has high quality and low impurity content.

[0060] According to some specific embodiments of the present application, in the second mixed liquid, the mass proportion of lithium tetrafluoroborate is less than or equal to 20%, for example, it can be 1%, 5%, 10%, 15%, 20%, etc. Controlling the mass proportion of lithium tetrafluoroborate within the above range can ensure the sufficient progress of the reaction while avoiding the formation of by-products.

[0061] The ratio of the amount of oxalate silicone grease in the first dynamic microchannel reactor to the amount of lithium tetrafluoroborate in the second mixed solution is 1:(1-1.05). For example, the ratio of the amount of the two can be 1:1.01, 1:1.02, 1:1.03, 1:1.04, 1:1.05, etc. Controlling the ratio of the two within the above range can ensure sufficient reaction while avoiding the formation of by-products.

[0062] According to some specific embodiments of the present application, the Reynolds number of the fluid in the second dynamic microchannel reactor 8 is greater than or equal to 15,000. For example, the Reynolds number can be 15,000, 20,000, 50,000, 70,000, 80,000, 90,000, 100,000, 150,000, etc. By controlling the Reynolds number of the fluid in the second dynamic microchannel reactor 8 within the above range, the fluid therein can be in a turbulent state, thereby improving the mass transfer efficiency and reaction rate.

[0063] According to some specific embodiments of the present application, the second reaction time is 1 min to 10 min. For example, it can be 1 min, 5 min, 10 min, etc. Controlling the second reaction time within the above range can ensure that the reaction proceeds fully while avoiding the formation of by-products caused by excessive residence time, thereby ensuring that the prepared lithium bifluorooxalatoborate has high quality and low impurity content.

[0064] According to some specific embodiments of the present application, step S3 includes: S31, flash evaporating the mixed reaction liquid to obtain a solid-liquid mixture and gas; S32. Continuously centrifuging the solid-liquid mixture and separating and removing the solid to obtain a solution of lithium difluorooxalatoborate and an ester solvent.

[0065] Specifically, a flash tank can be used for flash evaporation, and a continuous centrifuge can be used for continuous centrifugation. After the reaction, the material continuously enters the flash tank 9, and the mixed gas of fluorosilane, chlorosilane and solvent volatilization is discharged from the gas phase. The liquid enters the continuous centrifuge 10 to form a chloride salt solid with a moisture content of 15%, such as sodium chloride, and a solution of the product lithium bifluorooxalate borate and an ester solvent. The chloride salt solid with a moisture content of 15% is dried to obtain a chloride salt by-product.

[0066] According to some specific embodiments of the present application, the flash evaporation temperature is 110°C~120°C, for example, it can be 110°C, 112°C, 115°C, 117°C, 120°C, etc. By controlling the flash evaporation temperature within the above range, the mixed gas of fluorosilane, chlorosilane and solvent volatilization gas in the product of the second dynamic microchannel reactor 8 can be discharged from the gas phase, thereby realizing the separation of impurities, facilitating the removal of fluorosilane, chlorosilane, etc. in the reaction product, and making the obtained lithium difluorooxalatoborate high in quality and low in impurity content.

[0067] According to some specific embodiments of the present application, the flash evaporation pressure is 0.5 MPa~1 MPa, for example, it can be 0.5 MPa, 0.6 MPa, 0.7 MPa, 0.8 MPa, 0.9 MPa, 1 MPa, etc., thereby making it easy to make the prepared lithium difluorooxalatoborate have high quality and low impurity content.

[0068] According to some specific embodiments of the present application, the rotation speed of the continuous centrifugation is 60 r / min to 120 r / min. For example, it can be 60 r / min, 80 r / min, 100 r / min, 120 r / min, etc. By controlling the rotation speed of the continuous centrifugation within the above range, it is possible to ensure the separation of solid chloride salts such as sodium chloride from a solution of lithium bifluorooxalatoborate and an ester solvent, and to reduce the moisture content of the solid chloride salts to less than 15%, facilitating subsequent drying.

[0069] According to some specific embodiments of the present application, the pressure of the continuous centrifugation is 0.5 MPa~1 MPa, for example, it can be 0.5 MPa, 0.6 MPa, 0.7 MPa, 0.8 MPa, 0.9 MPa, 1 MPa, etc., thereby making it easier to obtain lithium difluorooxalatoborate with high quality and low impurity content.

[0070] In a second aspect of the present application, a device for continuously preparing lithium difluorooxalatoborate is provided, wherein the device is configured to perform the method described in the first aspect of the present application. This device enables continuous production of lithium difluorooxalatoborate, improves production efficiency, and produces lithium difluorooxalatoborate of high quality and low impurity content.

[0071] According to some specific embodiments of this application, please refer to Figure 2 The above-mentioned device for continuously preparing lithium tetrafluoroborate oxalate includes a first dynamic microchannel reactor 5, a second dynamic microchannel reactor 8 and a separation device, wherein a first mixed liquid formed by oxalate and an ester solvent and chlorosilane are continuously pumped into the first dynamic microchannel reactor 5; the second dynamic microchannel reactor 8 is arranged downstream of the first dynamic microchannel reactor 5, and the reaction product in the first dynamic microchannel reactor 5 is continuously pumped into the second dynamic microchannel reactor 8, and a second mixed liquid formed by lithium tetrafluoroborate and an ester solvent is continuously pumped into the second dynamic microchannel reactor 8; the separation device is arranged downstream of the second dynamic microchannel reactor 8, for separating the reaction product in the second dynamic microchannel reactor 8 to obtain lithium tetrafluoroborate oxalate.

[0072] See also Figure 2 The device for continuously preparing lithium bisfluorooxalatoborate further includes a chlorosilane storage tank 1, an oxalate storage tank 2, and a lithium tetrafluoroborate tank 6, wherein the chlorosilane storage tank 1 is located upstream of the first dynamic microchannel reactor 5, and the chlorosilane in the chlorosilane storage tank 1 is pumped into the first dynamic microchannel reactor 5 by a first feed pump 3; the oxalate storage tank 2 is located upstream of the first dynamic microchannel reactor 5, and the oxalate storage tank 2 stores a first mixed liquid formed by oxalate and an ester solvent, and the first mixed liquid is pumped into the first dynamic microchannel reactor 5 by a second feed pump 4; the lithium tetrafluoroborate tank 6 is located upstream of the second dynamic microchannel reactor 8, and the lithium tetrafluoroborate tank 6 stores a second mixed liquid formed by lithium tetrafluoroborate and an ester solvent, and the second mixed liquid is pumped into the second dynamic microchannel reactor 8 by a third feed pump 7. In this way, continuous production of lithium bisfluorooxalatoborate can be achieved, production efficiency is improved, and the obtained lithium bisfluorooxalatoborate is of high quality and low impurity content.

[0073] In summary, the device for continuously preparing lithium difluorooxalatoborate proposed in this application utilizes a two-stage dynamic microchannel reactor to promote the rapid synthesis of solid chloride salt and oxalic acid silicone grease in the first dynamic microchannel reactor 5, reduce the post-synthesis separation process, and directly enter the second step of fast reaction. The gas phase is subjected to distillation separation and application, the liquid is continuously separated, and impurities enter solid industrial-grade sodium chloride. The liquid is a qualified product, a solution of lithium difluorooxalatoborate and an ester solvent.

[0074] In a third aspect of the present application, a lithium difluorooxalate borate solution is provided. The lithium difluorooxalate borate solution comprises lithium difluorooxalate borate and an ester solvent. The lithium difluorooxalate borate solution is prepared using the continuous preparation method for lithium difluorooxalate borate described in the first aspect of the present application. Thus, the lithium difluorooxalate borate solution provided in the present application can achieve continuous production, improving production efficiency, and the prepared lithium difluorooxalate borate is high-quality and low in impurities.

[0075] According to some specific embodiments of the present application, based on the total mass of the lithium bifluorooxalatoborate solution, the mass proportion of the lithium bifluorooxalatoborate is 10% to 35%, for example, 10%, 15%, 16%, 17%, 18%, 19%, 20%, 30%, 35%, etc. In this way, continuous production of lithium bifluorooxalatoborate can be achieved, production efficiency is improved, and the obtained lithium bifluorooxalatoborate is of high quality and low impurity content.

[0076] According to some specific embodiments of the present application, based on the total mass of the lithium difluorooxalate borate solution, the mass proportion of lithium chloride is less than or equal to 15 ppm, for example, it can be 0, 1 ppm, 5 ppm, 10 ppm, 15 ppm, etc., thereby controlling the mass proportion of impurity lithium chloride in the lithium difluorooxalate borate solution within the above range, thereby achieving continuous production of lithium difluorooxalate borate, improving production efficiency, and the obtained lithium difluorooxalate borate is of high quality and low impurity content.

[0077] According to some specific embodiments of the present application, based on the total mass of the lithium bisfluorooxalatoborate solution, the mass proportion of tetrafluoroborate is less than or equal to 15 ppm. For example, it can be 0, 1 ppm, 5 ppm, 10 ppm, 15 ppm, etc. By controlling the content of tetrafluoroborate as an impurity in the lithium bisfluorooxalatoborate solution within the above range, the lithium bisfluorooxalatoborate has high quality and low impurity content. When used in a battery, it can better improve the high-temperature cycling performance and high-temperature storage performance of the battery.

[0078] The following examples of the present application are described in detail. It should be noted that the following examples are illustrative and are intended only to explain the present application and are not to be construed as limiting the present application. In addition, unless otherwise expressly stated, all reagents used in the following examples are commercially available or can be synthesized according to methods described herein or known methods. Reaction conditions not listed are also readily available to those skilled in the art.

[0079] Example 1 Use high-pressure nitrogen to increase the pressure of the entire system to 0.6MPa, and stabilize the pressure of the entire device at 0.8Mpa through the back pressure system.

[0080] The temperature of the first dynamic microchannel reactor was raised to 90°C, and the stirring speed was 300 r / min. The temperature of the second dynamic microchannel reactor was raised to 40°C, the temperature of the flash tank was set to 110°C, and the continuous centrifuge was kept at 90 r / min.

[0081] In the feeding system, sodium oxalate and DMC solvent were stirred in a kettle to form a uniform liquid (first mixed liquid) with a sodium oxalate mass ratio of 10%. The first mixed liquid and chlorosilane then simultaneously entered the first dynamic microchannel reactor. The mass flow ratio of the two groups was 6:1, and the reaction residence time was 20 minutes. The reacted mixed liquid then entered the second dynamic microchannel reactor, to which lithium tetrafluoroborate solution was simultaneously added. The mass ratio of lithium tetrafluoroborate to the lithium tetrafluoroborate DMC solution was 9%, the molar ratio of oxalic acid silicone grease to lithium tetrafluoroborate was 1:1.02, and the reaction residence time was 5 minutes.

[0082] In the post-processing unit, the material from the second dynamic microchannel reactor enters a flash tank, and the mixed gas of chlorosilane, fluorosilane, and DMC is discharged from the gas phase. The liquid enters a continuous centrifuge, forming a 15% moisture content sodium chloride solid and a product solution. The 15% moisture content sodium chloride solid is dried to obtain sodium chloride as a by-product, with sodium chloride accounting for 99.55% by weight, lithium chloride accounting for 0.07% by weight, and sodium tetrafluoroborate accounting for 0.38% by weight. The product solution is tested to be 19.9% ​​by weight of lithium difluorooxalatoborate, 4 ppm by weight of lithium chloride, 10 ppm by weight of tetrafluoroborate (lithium tetrafluoroborate and sodium tetrafluoroborate), and the remainder is the solvent DMC.

[0083] Examples 2 to 36 The methods for continuously preparing lithium bifluorooxalatoborate in Examples 2-36 are the same as in Example 1, with the differences shown in Table 1. The tetrafluoroborate in Example 30 is lithium tetrafluoroborate and potassium tetrafluoroborate, and the byproduct is potassium chloride. That is, in Table 2, the chloride salt in Example 30 is potassium chloride, while the chloride salt in the remaining Examples and Comparative Examples is sodium chloride.

[0084] Comparative Example 1 Sodium oxalate and DMC solvent were stirred in a kettle to form a uniform liquid (first mixed liquid) with a sodium oxalate mass ratio of 10%. The first mixed liquid was then mixed with chlorosilane in a mass ratio of 6:1. The mixture was reacted at 90°C and 0.8 MPa for 20 minutes to obtain a mixed liquid.

[0085] The sodium chloride was separated from the mixed solution to obtain an oxalic acid silicone grease solution. The mass proportion of lithium tetrafluoroborate in the DMC solution of lithium tetrafluoroborate was 10%. The oxalic acid silicone grease and lithium tetrafluoroborate were mixed in a molar ratio of 1:1.02, and the mixture was reacted at 40° C. for 5 minutes to obtain a reaction solution.

[0086] The reaction liquid is flash evaporated at a temperature of 110°C. The mixed gas of chlorosilane, fluorosilane and DMC is discharged from the gas phase, and the liquid enters a centrifuge at a speed of 90 r / min to form a sodium chloride solid with a moisture content of 15% and a product solution. The sodium chloride solid with a moisture content of 15% is dried to obtain sodium chloride as a by-product. The product solution is a solution of lithium difluorooxalatoborate and an ester solvent.

[0087] Comparative Examples 2 to 7 The continuous preparation methods of lithium bifluorooxalatoborate in Comparative Examples 2 to 7 are the same as those in Example 1, with the differences shown in Table 1. In Comparative Examples 2 and 3, the mass flow rate ratio of the first mixed liquid to the chlorosilane is not within the range defined in this application, the reaction temperature in the second dynamic microchannel reactor in Comparative Examples 4 and 5 is not within the range defined in this application, and the rotation speed in the second dynamic microchannel reactor in Comparative Examples 6 and 7 is not within the range defined in this application.

[0088]

[0089]

[0090] The chromatogram of the solution of lithium bifluorooxalate borate and ester solvent prepared in Example 1 is as follows: Figure 3 As shown, it can be seen that the solution of lithium difluorooxalatoborate and ester solvent prepared in Example 1 of the present application is of high quality.

[0091] The components of the sodium chloride byproduct and the solutions of lithium bifluorooxalatoborate and ester solvents in Examples 1 to 36 and Comparative Examples 1 to 7 were respectively measured. The test results are shown in Table 2.

[0092] 1. Determination of the composition of sodium chloride by-product: Sample pretreatment (deionized water dilution / filtration) and Li detection using ICP inductively coupled plasma + (Chromatographic column: CS12A), IC negative ion mode detection of BF4 - (Chromatographic column: AS11-HC), converted into the mass proportion of lithium chloride and the mass proportion of tetrafluoroborate.

[0093] 2. Determination of the composition of the solution of lithium difluorooxalatoborate and ester solvents: The samples were pretreated (dilution / filtration with deionized water) and the F- and oxalate contents were detected using an IC ion chromatograph, which was then converted into the corresponding mass percentage of lithium difluorooxalatoborate.

[0094] The test results are shown in Table 2.

[0095]

[0096]

[0097] in conclusion: As can be seen from Table 2, in Examples 1-36, the continuous preparation method of lithium bis(fluorooxalatoborate) according to the embodiments of the present application is adopted, and the ratio of the reaction materials of the first reaction and the temperature and speed of the second reaction are controlled simultaneously. Continuous production of lithium bis(fluorooxalatoborate) can be achieved, production efficiency is improved, and the obtained lithium bis(fluorooxalatoborate) is of high quality, and sodium chloride or potassium chloride can be obtained as a by-product. Comparative Example 1 does not adopt a continuous preparation method, and the quality of the obtained lithium bis(fluorooxalatoborate) is low. Comparative Examples 2-7 do not simultaneously control the ratio of the reaction materials of the first reaction and the temperature and speed of the second reaction. The obtained lithium bis(fluorooxalatoborate) is of low quality and has a high impurity content.

[0098] Compared with Example 1, the first reaction time in Example 10 is shorter, and the second reaction time in Example 23 is shorter, so the reaction is insufficient, resulting in a mismatch between the working hours of the first dynamic microchannel reactor and the second dynamic microchannel reactor, and the content of lithium difluorooxalatoborate in the solution of lithium difluorooxalatoborate and ester solvents is reduced. The mass proportion of oxalate in Example 6 is reduced, and the mass proportion of lithium tetrafluoroborate in Example 19 is reduced. Therefore, the reaction is insufficient, resulting in a mismatch between the working hours of the first dynamic microchannel reactor and the second dynamic microchannel reactor, and the content of lithium difluorooxalatoborate in the solution of lithium difluorooxalatoborate and ester solvents is reduced.

[0099] Compared with Example 1, the first reaction time and the second reaction time in Example 25 are both longer, resulting in an increase in side reactions, and thus the content of by-products such as lithium fluoride and tetrafluoroborate in the obtained solution of lithium bifluoro oxalate borate and ester solvents increases; in Example 35, the amount ratio of oxalate silicone grease and lithium tetrafluoroborate increases, the flash evaporation temperature increases, and the speed of continuous centrifugation increases, resulting in an increase in side reactions, and thus the content of by-products such as lithium fluoride and tetrafluoroborate in the obtained solution of lithium bifluoro oxalate borate and ester solvents increases; in Example 36, the amount ratio of oxalate silicone grease and lithium tetrafluoroborate decreases, the flash evaporation temperature decreases, and the speed of continuous centrifugation decreases, which also causes an increase in side reactions, and thus the content of by-products such as lithium fluoride and tetrafluoroborate in the obtained solution of lithium bifluoro oxalate borate and ester solvents increases.

[0100] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present application. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art can combine and combine different embodiments or examples described in this specification and features of different embodiments or examples without contradiction.

[0101] Although the embodiments of the present application have been shown and described above, it can be understood that the above embodiments are exemplary and cannot be understood as limitations on the present application. Ordinary technicians in this field can change, modify, replace and modify the above embodiments within the scope of the present application.

Claims

1. A method for continuously preparing lithium difluorooxalatoborate, characterized in that: include: A first mixed solution formed by oxalate and an ester solvent and chlorosilane are continuously pumped into a first dynamic microchannel reactor to perform a first reaction to obtain a reaction product, wherein the mass flow rate ratio of the first mixed solution to the chlorosilane is (4-10):1; continuously pumping the reaction product into a second dynamic microchannel reactor, and continuously pumping a second mixed solution formed by lithium tetrafluoroborate and an ester solvent into the second dynamic microchannel reactor, and performing a second reaction at a temperature of 20° C. to 70° C. and a rotation speed of 200 rpm to 400 rpm to obtain a mixed reaction solution; The reaction product in the mixed reaction liquid is separated to obtain lithium difluorooxalatoborate.

2. The method for continuously preparing lithium bifluorooxalatoborate according to claim 1, characterized in that: The method satisfies at least one of the following conditions: The pressure of the first reaction and the second reaction is 0.5MPa~1MPa; The temperature of the first reaction is 50°C to 120°C.

3. The method for continuously preparing lithium bifluorooxalatoborate according to claim 1, characterized in that: The method satisfies at least one of the following conditions: In the first mixed solution, the mass proportion of oxalate is less than or equal to 20%; In the second mixed solution, the mass proportion of lithium tetrafluoroborate is less than or equal to 20%; The ratio of the amount of oxalic acid silicone grease in the reaction product to the amount of lithium tetrafluoroborate in the second mixed solution is 1:(1-1.05).

4. The method for continuously preparing lithium bifluorooxalatoborate according to claim 1, characterized in that: The method satisfies at least one of the following conditions: The oxalate comprises at least one of sodium oxalate and potassium oxalate; The ester solvent includes at least one of dimethyl carbonate, ethyl methyl carbonate and diethyl carbonate; The stirring speed of the first reaction is 200r / min~400r / min; The Reynolds number of the fluid in the first dynamic microchannel reactor is greater than or equal to 10,000; The time of the first reaction is 1 min to 30 min; The Reynolds number of the fluid in the second dynamic microchannel reactor is greater than or equal to 15000; The second reaction time is 1 min to 10 min.

5. The method for continuously preparing lithium bifluorooxalatoborate according to any one of claims 1 to 4, characterized in that: The step of separating the reaction products in the mixed reaction liquid comprises: flash evaporating the mixed reaction liquid to obtain a solid-liquid mixture and a gas; The solid-liquid mixture is continuously centrifuged, and the solid is separated and removed to obtain a solution of lithium difluorooxalatoborate and an ester solvent.

6. The method for continuously preparing lithium bifluorooxalatoborate according to claim 5, characterized in that: The method satisfies at least one of the following conditions: The flash evaporation temperature is 110°C to 120°C; and / or, The continuous centrifugation speed is 60 r / min to 120 r / min; and / or, The flash evaporation pressure is 0.5 MPa to 1 MPa; and / or, The pressure of the continuous centrifugation is 0.5 MPa to 1 MPa.

7. A device for continuously preparing lithium difluorooxalatoborate, characterized in that: The device is used to perform the method according to any one of claims 1 to 6.

8. A lithium difluorooxalate borate solution, characterized in that: The method comprises lithium difluorooxalatoborate and an ester solvent, wherein the lithium difluorooxalatoborate solution is prepared by the continuous preparation method of lithium difluorooxalatoborate according to any one of claims 1 to 6.

9. The lithium bifluorooxalate borate solution according to claim 8, characterized in that Based on the total mass of the lithium difluorooxalatoborate solution, the mass proportion of the lithium difluorooxalatoborate is 10% to 35%.

10. The lithium bifluorooxalate borate solution according to claim 8, characterized in that Based on the total mass of the lithium difluorooxalatoborate solution, the mass proportion of lithium chloride is less than or equal to 15 ppm.

11. The lithium bifluorooxalate borate solution according to claim 8, characterized in that Based on the total mass of the lithium difluorooxalatoborate solution, the mass proportion of tetrafluoroborate is less than or equal to 15 ppm.

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