Method, device for continuous production of lithium difluorooxalato borate, lithium difluorooxalato borate solution

Abstract

The application discloses a method and device for continuously preparing bifluoride lithium oxalate, and a bifluoride lithium oxalate solution, and belongs to the technical field of electrolyte salt synthesis. The method comprises the following steps: continuously pumping a first mixed solution formed by oxalate and ester solvent and chlorosilane into a first dynamic micro-channel reactor to perform 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 ester solvent into the second dynamic micro-channel reactor, and performing 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 the reaction product in the mixed reaction solution to obtain the bifluoride lithium oxalate. The method for continuously preparing the bifluoride lithium oxalate can realize continuous production of the bifluoride lithium oxalate, and the quality of the bifluoride lithium oxalate is high.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of electrolyte salt synthesis, and particularly relates to a method and device for continuously preparing lithium difluoro(oxalato)borate and lithium difluoro(oxalato)borate solution. BACKGROUND

[0002] Lithium difluoro(oxalato)borate (LiODFB) is an important high-performance lithium ion battery electrolyte additive, which has the advantages of lithium bis(oxalato)borate and lithium tetrafluoroborate, has good electrochemical properties and thermal stability, and helps to form a more stable SEI film on the negative electrode surface, thereby improving the high-temperature cycle performance and high-temperature storage performance of the battery. In addition, the SEI film formed by LiODFB can prevent the co-intercalation of electrolyte solvents (especially propylene carbonate) on the negative electrode surface and prevent the destruction of the SEI film structure.

[0003] Currently, there is a related technology that uses oxalate such as sodium oxalate to react with chlorosilane to obtain oxalic acid silicon fat, and then the oxalic acid silicon fat reacts with lithium tetrafluoroborate to obtain a synthesis route of lithium difluoro(oxalato)borate. This route is generally divided into two steps. The first step is to react oxalate with chlorosilane to generate oxalic acid silicon fat. The second step is to react oxalic acid silicon fat and lithium tetrafluoroborate to generate lithium difluoro(oxalato)borate. After the synthesis of oxalic acid silicon fat, the generated chlorinated salt such as sodium chloride will undergo a double decomposition reaction with lithium tetrafluoroborate in the second step, resulting in high acidity of the reaction product and excessive chlorine ion content. Therefore, it is generally necessary to separate the solid chlorinated salt such as sodium chloride, otherwise continuous production of lithium difluoro(oxalato)borate cannot be achieved. SUMMARY

[0004] The present application aims to at least partially solve one of the technical problems in the related art. To this end, one object of the present application is to provide a method and device for continuously preparing lithium difluoro(oxalato)borate and lithium difluoro(oxalato)borate solution. The method for continuously preparing lithium difluoro(oxalato)borate proposed in the present application can achieve continuous production of lithium difluoro(oxalato)borate, improve production efficiency, and produce lithium difluoro(oxalato)borate with high quality.

[0005] The first aspect of the present application provides a method for continuously preparing lithium difluoro(oxalato)borate, comprising continuously pumping a first mixed solution formed by oxalate and ester solvent and chlorosilane into a first dynamic microchannel reactor to perform 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 microchannel reactor, and continuously pumping a second mixed solution formed by lithium tetrafluoroborate and ester solvent into the second dynamic microchannel reactor, and performing a second reaction at a temperature of 20-70℃ and a rotation speed of 200-400r / min to obtain a mixed reaction solution; and separating the reaction product in the mixed reaction solution to obtain lithium difluoro(oxalato)borate.

[0006] The method for continuously preparing lithium difluoro(oxalato)borate according to the embodiments of the present application uses a first dynamic microchannel reactor and a second dynamic microchannel reactor in combination, fully utilizes 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, the reaction time of the first reaction is relatively long, and the reaction time of the second reaction is relatively short, so that the reaction time of the two-step reaction is not matched, resulting in low production efficiency and poor quality of the product lithium difluoro(oxalato)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 realizes the matching of the reaction time of the two reactions in the first dynamic microchannel reactor and the second dynamic microchannel reactor. On the other hand, the temperature and the rotation speed of the second reaction are controlled. The rotation speed makes the solid chlorinated salt such as sodium chloride gather on the inner wall of the second dynamic microchannel reactor under the action of centrifugal force, so as to reduce the probability of the complex reaction of lithium tetrafluoroborate in the liquid material. The reaction temperature makes the main reaction of the second step quickly proceed in the central cavity and match the time of the first reaction. Further, the solid-containing reaction liquid obtained by the first reaction in the first dynamic microchannel reactor does not need to separate the chlorinated salt such as sodium chloride, and directly enters the second dynamic microchannel reactor for the second reaction. After the reaction, the separation is uniformly carried out, so as to ensure the quality of the obtained lithium difluoro(oxalato)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 difluoro(oxalato)borate, but is not easy to dissolve the by-products such as sodium chloride, lithium chloride and sodium tetrafluoroborate. Therefore, the solution of the ester solvent of the lithium difluoro(oxalato)borate with qualified acidity and chlorine ion content can be obtained. In summary, the method for continuously preparing lithium difluoro(oxalato)borate proposed in the present application can realize the continuous production of lithium difluoro(oxalato)borate, improve the production efficiency, and obtain lithium difluoro(oxalato)borate with 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. In this way, the continuous production of lithium difluoro(oxalato)borate can be realized, the production efficiency is improved, and the lithium difluoro(oxalato)borate with high quality and low impurity content can be obtained.

[0008] In some embodiments of the present application, the temperature of the first reaction is 50°C to 120°C. In this way, the continuous production of lithium difluoro(oxalato)borate can be realized, the production efficiency is improved, and the lithium difluoro(oxalato)borate with high quality and low impurity content can be obtained.

[0009] In some embodiments of the present application, the mass fraction of oxalate in the first mixed solution is less than or equal to 20%. Thus, continuous production of lithium difluoroboric oxalate can be realized, the production efficiency is improved, and the quality of the prepared lithium difluoroboric oxalate is high and the impurity content is low.

[0010] In some embodiments of the present application, the mass fraction of lithium tetrafluoroborate in the second mixed solution is less than or equal to 20%. Thus, continuous production of lithium difluoroboric oxalate can be realized, the production efficiency is improved, and the quality of the prepared lithium difluoroboric oxalate is high and the impurity content is low.

[0011] In some embodiments of the present application, the ratio of the amount of substance of oxalic acid silicon ester in the reaction product to the amount of substance of lithium tetrafluoroborate in the second mixed solution is 1: (1-1.05). Thus, continuous production of lithium difluoroboric oxalate can be realized, the production efficiency is improved, and the quality of the prepared lithium difluoroboric oxalate is high and the impurity content is low.

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

[0013] In some embodiments of the present application, the ester solvent includes at least one of dimethyl carbonate, methyl ethyl carbonate and diethyl carbonate. Thus, continuous production of lithium difluoroboric oxalate can be realized, the production efficiency is improved, and the quality of the prepared lithium difluoroboric oxalate is high and the impurity content is low.

[0014] In some embodiments of the present application, the stirring speed of the first reaction is 200 r / min-400 r / min. Thus, continuous production of lithium difluoroboric oxalate can be realized, the production efficiency is improved, and the quality of the prepared lithium difluoroboric oxalate is high and the impurity content is low.

[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 10,000. Thus, continuous production of lithium difluoroboric oxalate can be realized, the production efficiency is improved, and the quality of the prepared lithium difluoroboric oxalate is high and the impurity content is low.

[0016] In some embodiments of the present application, the reaction time of the first reaction is 1 min-30 min. Thus, continuous production of lithium difluoroboric oxalate can be realized, the production efficiency is improved, and the quality of the prepared lithium difluoroboric oxalate is high and the impurity content is low.

[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 difluoroboric acid oxalate can be achieved, the production efficiency is improved, and the quality of the lithium difluoroboric acid oxalate produced is high and the impurity content is low.

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

[0019] In some embodiments of the present application, the step of separating the reaction product in the mixed reaction solution comprises: flashing the mixed reaction solution to obtain a solid-liquid mixture and a gas; continuously centrifuging the solid-liquid mixture and removing the solid to obtain a solution of lithium difluoroboric acid oxalate and an ester solvent. Thus, continuous production of lithium difluoroboric acid oxalate can be achieved, the production efficiency is improved, and the quality of the lithium difluoroboric acid oxalate produced is high and the impurity content is low.

[0020] In some embodiments of the present application, the flashing temperature is 110°C to 120°C. Thus, continuous production of lithium difluoroboric acid oxalate can be achieved, the production efficiency is improved, and the quality of the lithium difluoroboric acid oxalate produced is high and the impurity content is low.

[0021] In some embodiments of the present application, the rotation speed of the continuous centrifugation is 60 r / min to 120 r / min. Thus, continuous production of lithium difluoroboric acid oxalate can be achieved, the production efficiency is improved, and the quality of the lithium difluoroboric acid oxalate produced is high and the impurity content is low.

[0022] In some embodiments of the present application, the flashing pressure is 0.5 MPa to 1 MPa. Thus, continuous production of lithium difluoroboric acid oxalate can be achieved, the production efficiency is improved, and the quality of the lithium difluoroboric acid oxalate produced is high and the impurity content is low.

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

[0024] The second aspect of the present application proposes a device for continuously preparing lithium difluoroboric acid oxalate, which is used to perform the method of the first aspect of the present application. Thus, continuous production of lithium difluoroboric acid oxalate can be achieved, the production efficiency is improved, and the quality of the lithium difluoroboric acid oxalate produced is high and the impurity content is low.

[0025] The third aspect of the present application provides a double lithium bifluoride solution, the double lithium bifluoride solution comprising double lithium bifluoride and an ester solvent, and the double lithium bifluoride solution is prepared by the method for continuously preparing double lithium bifluoride according to the first aspect of the present application. Thus, the production efficiency of the double lithium bifluoride solution is high, the quality of the double lithium bifluoride is high, and the impurity content is low.

[0026] In some embodiments of the present application, the mass percentage of the double lithium bifluoride is 10% to 35% based on the total mass of the double lithium bifluoride solution. Thus, the production efficiency of the double lithium bifluoride solution is high, the quality of the double lithium bifluoride is high, and the impurity content is low.

[0027] In some embodiments of the present application, the mass percentage of lithium chloride is less than or equal to 15 ppm based on the total mass of the double lithium bifluoride solution. Thus, the production efficiency of the double lithium bifluoride solution is high, the quality of the double lithium bifluoride is high, and the impurity content is low.

[0028] In some embodiments of the present application, the mass percentage of lithium chloride is less than or equal to 15 ppm based on the total mass of the double lithium bifluoride solution. Thus, the production efficiency of the double lithium bifluoride solution is high, the quality of the double lithium bifluoride is high, and the impurity content is low.

[0029] Additional aspects and advantages of the present application will be in part apparent and in part pointed out hereinafter. BRIEF DESCRIPTION OF DRAWINGS

[0030] The above and / or additional aspects and advantages of the present application will become apparent and be readily appreciated from the following description, including the appended drawings.

[0031] Figure 1 FIG. 1 is a flow chart of a method for continuously preparing double lithium bifluoride according to an embodiment of the present application.

[0032] Figure 2 FIG. 2 is a structural diagram of an apparatus for continuously preparing double lithium bifluoride according to an embodiment of the present application.

[0033] Figure 3 FIG. 3 is a chromatogram of a solution of double lithium bifluoride and an ester solvent obtained by the method according to Embodiment 1 of the present application.

[0034] DETAILED DESCRIPTION

[0035] 1 chlorosilane storage tank; 2 oxalate storage tank; 3 first feed pump; 4 second feed pump; 5 first dynamic micro-channel reactor; 6 lithium tetrafluoroborate tank; 7 third feed pump; 8 second dynamic micro-channel reactor; 9 flash tank; 10 continuous centrifuge. DETAILED DESCRIPTION

[0036] The embodiments of the present application are described in detail below, the embodiments described below are exemplary and are intended to explain the present application, and cannot be understood as a limitation of the present application.

[0037] Bifluoroboric lithium oxalate is an important high-performance lithium ion battery electrolyte additive, which has the advantages of both lithium oxalate and lithium tetrafluoroborate, and has good electrochemical properties and thermal stability.

[0038] The existing preparation method of bifluoroboric lithium oxalate mainly includes synthesizing lithium tetrafluoroborate from lithium oxalate and boron trifluoride, and then reacting lithium tetrafluoroborate with oxalic acid to obtain bifluoroboric lithium oxalate. In the production process, there are corrosive materials such as boron trifluoride and oxalic acid, which have high requirements for the reaction system, increase the cost of equipment and the difficulty of maintenance. In addition, this reaction route exists gas-liquid reaction, the reaction efficiency is low, and a large amount of corrosive tail gas is also produced, which is difficult to be continuous.

[0039] At present, there are related technologies that use oxalate such as sodium oxalate to react with chlorosilane to obtain oxalic acid silicon grease, and then oxalic acid silicon grease reacts with lithium tetrafluoroborate to obtain a synthesis route of bifluoroboric lithium oxalate. This route is generally divided into two steps. After the synthesis of oxalic acid silicon grease, solid chlorinated salt such as sodium chloride needs to be separated, otherwise sodium chloride and chlorosilane that does not participate in the reaction will undergo double decomposition reaction with lithium tetrafluoroborate, causing the reaction product to have high acidity and the chlorine ion content to exceed the standard. On the other hand, when the oxalic acid silicon grease is subjected to the second step reaction, lithium tetrafluoroborate and solvent are added, and after the reaction, evaporation separation is carried out again. This route has the problems of long first-step solid-liquid reaction time, complex post-treatment, and mismatch between the first-step and second-step reaction times, resulting in low process efficiency and unstable product quality.

[0040] Therefore, the first aspect of the present application proposes a method for continuously preparing bifluoroboric lithium oxalate. According to the embodiments of the present application, please refer to Figure 1 The above-mentioned method for continuously preparing bifluoroboric lithium oxalate comprises:

[0041] S1, continuously pumping a first mixed liquid formed by oxalate and ester solvent and chlorosilane into a first dynamic micro-channel reactor to carry out 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;

[0042] S2, continuously pumping the reaction product into a second dynamic micro-channel reactor, and continuously pumping a second mixed liquid formed by lithium tetrafluoroborate and ester solvent into the second dynamic micro-channel reactor, and carrying out a second reaction at 20-70°C to obtain a mixed reaction liquid;

[0043] S3, separating the reaction product in the mixed reaction solution to obtain lithium difluorooxalate borate.

[0044] The beneficial effects of the continuous preparation method of lithium difluorooxalate borate provided in the present application are described in detail as follows:

[0045] The present application provides a continuous preparation method of lithium difluorooxalate borate, which uses a first dynamic micro-channel reactor 5 and a second dynamic micro-channel reactor 8 in combination, fully utilizes the tolerance of the dynamic micro-channel reactor to solid substances, and has high heat and mass transfer efficiency, high safety, and high reaction efficiency. However, in the two dynamic micro-channel reactors, the reaction time of the first reaction is relatively long, and the reaction time of the second reaction is relatively short, which causes the reaction time of the two-step reaction to be mismatched, resulting in low production efficiency and poor quality of the product lithium difluorooxalate 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 realizes the matching of the reaction time of the two reactions in the first dynamic micro-channel reactor and the second dynamic micro-channel reactor. On the other hand, the temperature and the rotating speed of the second reaction are controlled. The above-mentioned rotating speed causes the solid-liquid layering of the reaction material of the second reaction under the action of centrifugal force, so that the solid salt such as sodium chloride is aggregated on the inner wall of the second dynamic micro-channel reactor, reducing the probability of the complex decomposition reaction of lithium tetrafluoroborate in the liquid material. The above-mentioned reaction temperature causes the main reaction of the second step to quickly proceed in the central cavity and match the time of the first reaction. Furthermore, the solid-containing reaction liquid obtained by the first reaction in the first dynamic micro-channel reactor 5 does not need to separate the salt such as sodium chloride, and directly enters the second dynamic micro-channel reactor 8 for the second reaction. After the reaction, the separation is uniformly carried out, 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 the by-products such as sodium chloride, lithium chloride and sodium tetrafluoroborate. Therefore, the solution of the ester solvent of the lithium difluorooxalate borate with qualified acidity and chlorine ion content can be obtained. In summary, the continuous preparation method of lithium difluorooxalate borate provided in the present application can realize the continuous production of lithium difluorooxalate borate, improve the production efficiency, and obtain lithium difluorooxalate borate with high quality and low impurity content.

[0046] It can be understood that for the reaction containing solid substances (such as oxalate, chloride, lithium tetrafluoroborate, etc.), the general micro-reactor or pipe reactor is easy to cause solid blockage and the like. Therefore, the dynamic micro-channel reactor is used in the present application, which is combined in the form of an outer jacket and an inner stirring, and has the functions of heat exchange and high-speed rotation of the built-in stirring shaft, which is a choice for solid-liquid continuous reaction and is not easy to cause solid blockage.

[0047] The temperature of the second reaction is 20-70°C. For example, it can be 20°C, 40°C, 50°C, 70°C, etc. The temperature of the second reaction is controlled in the above range, which has little effect on the main reaction rate, and the rate of the double decomposition reaction of chlorinated salt such as sodium chloride is extremely slow, the product selectivity is higher than 99%, which is beneficial to improve the quality of lithium bifluoride oxalate and reduce the impurity content; at the same time, the generation process of fluorosilane can be reduced, the generation of bubbles is reduced, the average residence time of the material is ensured, and the high efficiency of the reaction is ensured.

[0048] The mass flow ratio of the first mixed solution to the chlorosilane is (4-10):1, for example, it can be 4:1, 5:1, 7:1, 9:1, 10:1, etc. The mass flow ratio of the first mixed solution and chlorosilane is controlled in the above range, which can realize the molar ratio of oxalate such as sodium oxalate and chlorosilane to be 1:(1.01-1.05), promote the complete reaction of sodium oxalate after the reaction, and ensure the full reaction of the reaction, while avoiding the generation of by-products.

[0049] The stirring speed of the second reaction is 200-400 r / min, for example, it can be 200 r / min, 300 r / min, 400 r / min, etc. The stirring speed is controlled in the above range, which can make the fluid in the fluid be in a turbulent state, improve the mass transfer efficiency and reaction rate.

[0050] The following specifically details the advantages of the continuous preparation method of lithium bifluoride oxalate proposed in the present application:

[0051] High heat and mass transfer efficiency: The first dynamic micro-channel reactor 5 and the second dynamic micro-channel reactor 8 can perform efficient temperature control in the reaction cavity, and 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; The second mixed solution is added in the process of the two dynamic micro-channel reactors in series, the two-phase liquid realizes second-level mixing in the dynamic micro-channel reactor, the material reacts quickly according to the molar ratio, the reaction selectivity of lithium bifluoride oxalate is high, and the double decomposition reaction is less.

[0052] High safety: The first dynamic micro-channel reactor 5 and the second dynamic micro-channel reactor 8 have small liquid holding capacity and can withstand solid-liquid reaction conditions. After the reaction starts, the blade can force the solid to move, and there is no risk of overpressure caused by solid blocking the equipment; The heat exchange medium exists in the inner and outer sleeves of the stirring shaft of the first dynamic micro-channel reactor 5 and the second dynamic micro-channel reactor 8, the material temperature control is accurate, and the rapid flow of the material during stirring can avoid local overheating or hot spots.

[0053] High reaction efficiency: the ester solvent is used in the reaction raw material, and after the solid-liquid separation after the reaction, the solution of the lithium difluorooxalate borate dissolved in the ester solvent is directly produced, which is suitable for the electrolyte solvent, and no additional configuration process is needed, and the production efficiency is high; the reaction time of the lithium difluorooxalate borate is short, and the metathesis reaction of the chlorinated salt such as sodium chloride and lithium tetrafluoroborate occurs less.

[0054] High product purity: the inorganic by-products such as lithium chloride and ammonium tetrafluoroborate produced by the reaction of the chlorinated salt such as sodium chloride and lithium tetrafluoroborate have low solubility in the ester solvent, and the moisture-containing solid is simply dried to obtain industrial-grade by-product sodium chloride. The solubility of the product lithium difluorooxalate borate in the ester solvent is higher, so that when the solid-liquid separation is performed, the impurities enter the sodium chloride as the industrial-grade sodium chloride, and the insoluble matter, chloride ions and acidity of the lithium difluorooxalate borate solution in the ester solvent are controllable.

[0055] In addition, the reaction conditions can be optimized to further improve the purity and yield of the product. The reaction process has few steps, the chloride ions and acidity value in the lithium difluorooxalate borate solution product are controllable, and the quality is controllable.

[0056] Specifically, taking sodium oxalate as an example, the reaction equation in the first dynamic micro-channel reactor 5 is:

[0057] Na2C2O4+2Si(CH3)3Cl→(Si(CH3)3)2C2O4+2NaCl.

[0058] The reaction equation in the second dynamic micro-channel reactor 8 is:

[0059] (Si(CH3)3)2C2O4+LiBF4→LiC2O4BF2+2Si(CH3)3F.

[0060] According to some specific embodiments of the present application, the pressure of the first reaction and the second reaction is 0.5 MPa-1 MPa. As an example, the pressure of the first reaction and the second reaction can be 0.5 MPa, 0.6 MPa, 0.7 MPa, 0.8 MPa, 0.9 MPa, 1 MPa, etc. Specifically, nitrogen can be used to increase the pressure of the first reaction and the second reaction to 0.5 MPa-1 MPa, and the pressure of the first reaction and the second reaction is stabilized by a back pressure system, which ensures that the reaction process of the two dynamic micro-channel reactors is carried out under high pressure conditions, promotes the reaction in the first dynamic micro-channel reactor 5 and the second dynamic micro-channel reactor 8, and improves the reaction efficiency and product purity, and improves the stability of the whole continuous preparation device of lithium difluorooxalate borate.

[0061] According to some embodiments of the present application, the temperature of the first reaction is 50-120℃, for example, it can be 50℃, 70℃, 90℃, 100℃, 120℃, etc. Controlling the temperature of the first reaction in the above range, the reaction temperature is higher, which can promote the rapid reaction of oxalate such as sodium oxalate and chlorosilane, control the reaction time, match the fast reaction of the second dynamic microchannel reaction, realize the continuous production of bifluoro lithium oxalate borate, improve the production efficiency, and the quality of the prepared bifluoro lithium oxalate borate is high.

[0062] According to some embodiments of the present application, in the first mixed solution, the mass fraction of oxalate is less than or equal to 20%, for example, the mass fraction of oxalate can be 1%, 5%, 10%, 15%, 20%, etc. Controlling the mass fraction of oxalate in the above range can ensure that the reaction proceeds sufficiently while avoiding the generation of by-products.

[0063] According to some embodiments of the present application, the oxalate includes at least one of sodium oxalate and potassium oxalate, which is easy to react with chlorosilane under heating conditions and has less side reactions.

[0064] According to some embodiments of the present application, the ester solvent includes at least one of dimethyl carbonate (DMC), methyl ethyl carbonate (EMC) and diethyl carbonate (DEC), which can dissolve the product bifluoro lithium oxalate borate without easily dissolving by-products such as sodium chloride, lithium chloride and sodium tetrafluoroborate, so that a solution of ester solvent of bifluoro lithium oxalate borate with qualified acidity and chlorine ion content can be obtained, and the quality of the prepared bifluoro lithium oxalate borate is high with less impurities.

[0065] According to some embodiments of the present application, the ester solvent used in the first mixed solution and the second mixed solution is completely the same, for example, the first mixed solution uses dimethyl carbonate, and the second mixed solution also uses dimethyl carbonate, so that a solution of ester solvent of bifluoro lithium oxalate borate with high purity can be obtained.

[0066] According to some embodiments of the present application, the stirring speed of the first reaction is 200-400 r / min, for example, it can be 200 r / min, 300 r / min, 400 r / min, etc. Controlling the stirring speed in the above range can make the fluid in the stirring tank be in a turbulent flow state, improve the mass transfer efficiency and reaction rate.

[0067] According to some embodiments of the present application, the Reynolds number of the fluid in the first dynamic micro-channel reactor 5 is greater than or equal to 10000, for example, the Reynolds number can be 10000, 50000, 60000, 70000, 80000, 90000, 100000, 150000, etc. Controlling the Reynolds number of the fluid in the first dynamic micro-channel reactor 5 within the above range can make the fluid therein in a turbulent state, improve the mass transfer efficiency and reaction rate.

[0068] According to some 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 sufficient reaction, while avoiding the generation of by-products due to too long residence time, so that the quality of the prepared lithium bisfluorosulfoxylate borate is high and the impurity content is low.

[0069] According to some embodiments of the present application, in the second mixed solution, the mass fraction of lithium tetrafluoroborate is less than or equal to 20%, for example, it can be 1%, 5%, 10%, 15%, 20%, etc. Controlling the mass fraction of lithium tetrafluoroborate within the above range can ensure sufficient reaction, while avoiding the generation of by-products.

[0070] The ratio of the amount of substance of the silicic acid ester oxalate in the first dynamic micro-channel reactor to the amount of substance of lithium tetrafluoroborate in the second mixed solution is 1: (1-1.05). For example, the ratio of the amount of substance 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 amount of substance of the two within the above range can ensure sufficient reaction, while avoiding the generation of by-products.

[0071] According to some embodiments of the present application, the Reynolds number of the fluid in the second dynamic micro-channel reactor 8 is greater than or equal to 15000, for example, the Reynolds number can be 15000, 20000, 50000, 70000, 80000, 90000, 100000, 150000, etc. Controlling the Reynolds number of the fluid in the second dynamic micro-channel reactor 8 within the above range can make the fluid therein in a turbulent state, improve the mass transfer efficiency and reaction rate.

[0072] According to some embodiments of the present application, the time of the second reaction is 1 min to 10 min. For example, it can be 1 min, 5 min, 10 min, etc. Controlling the time of the second reaction within the above range can ensure sufficient reaction, while avoiding the generation of by-products due to too long residence time, so that the quality of the prepared lithium bisfluorosulfoxylate borate is high and the impurity content is low.

[0073] According to some embodiments of the present application, step S3 comprises:

[0074] S31, flash evaporating the mixed reaction solution to obtain a solid-liquid mixture and gas;

[0075] S32, continuously centrifuging the solid-liquid mixture and removing the solid to obtain a solution of lithium difluoroboric acid oxalate and ester solvent.

[0076] Specifically, the flash evaporation can use a flash evaporation tank, and the continuous centrifugation can use a continuous centrifuge. After the reaction, the material continuously enters the flash evaporation tank 9, the mixed gas of fluorosilane, chlorosilane and solvent volatilization gas is discharged from the gas phase, the liquid enters the continuous centrifuge 10, and the 15% moisture content of the chlorinated salt such as sodium chloride and the solution of the product lithium difluoroboric acid oxalate and ester solvent are formed. The 15% moisture content of the chlorinated salt solid is dried to obtain the chlorinated salt by-product.

[0077] According to some embodiments of the present application, the flash evaporation temperature is 110-120℃, for example, it can be 110℃, 112℃, 115℃, 117℃, 120℃, etc. Controlling the flash evaporation temperature in the above range can make the mixed gas of fluorosilane, chlorosilane and solvent volatilization gas in the product in the second dynamic micro-channel reactor 8 be discharged from the gas phase, realize the separation of impurities, facilitate the removal of fluorosilane, chlorosilane, etc. in the reaction product, make the quality of the prepared lithium difluoroboric acid oxalate high, and the impurity content low.

[0078] According to some embodiments of the present application, the flash evaporation pressure is 0.5-1 MPa, for example, it can be 0.5 MPa, 0.6 MPa, 0.7 MPa, 0.8 MPa, 0.9 MPa, 1 MPa, etc. Therefore, it is convenient to make the quality of the prepared lithium difluoroboric acid oxalate high, and the impurity content low.

[0079] According to some embodiments of the present application, the rotation speed of the continuous centrifugation is 60-120 r / min. For example, it can be 60 r / min, 80 r / min, 100 r / min, 120 r / min, etc. Controlling the rotation speed of the continuous centrifugation in the above range can not only ensure the separation of the solid chlorinated salt such as sodium chloride and the solution of lithium difluoroboric acid oxalate and ester solvent, but also can make the moisture content of the solid chlorinated salt be less than 15%, which is convenient for subsequent drying.

[0080] According to some embodiments of the present application, the continuous centrifugation pressure is 0.5-1 MPa, for example, it can be 0.5 MPa, 0.6 MPa, 0.7 MPa, 0.8 MPa, 0.9 MPa, 1 MPa, etc. Therefore, it is convenient to make the quality of the prepared lithium difluoroboric acid oxalate high, and the impurity content low.

[0081] In the second aspect of the present application, a device for continuously preparing lithium difluorooxalate borate is provided, which is used to perform the method of the first aspect of the present application. Thus, the continuous production of lithium difluorooxalate borate can be realized, the production efficiency is improved, and the prepared lithium difluorooxalate borate has high quality and low impurity content.

[0082] According to some embodiments of the present application, referring to Figure 2 The device for continuously preparing lithium difluorooxalate borate includes a first dynamic micro-channel reactor 5, a second dynamic micro-channel reactor 8, and a separation device. The first dynamic micro-channel reactor 5 continuously pumps a first mixed solution of oxalate and ester solvent and chlorosilane. The second dynamic micro-channel reactor 8 is located downstream of the first dynamic micro-channel reactor 5, and the reaction product in the first dynamic micro-channel reactor 5 is continuously pumped into the second dynamic micro-channel reactor 8. The second dynamic micro-channel reactor 8 continuously pumps a second mixed solution of lithium tetrafluoroborate and ester solvent. The separation device is located downstream of the second dynamic micro-channel reactor 8 and is used to separate the reaction product in the second dynamic micro-channel reactor 8 to obtain lithium difluorooxalate borate.

[0083] Referring to Figure 2 The device for continuously preparing lithium difluorooxalate borate further includes a chlorosilane storage tank 1, an oxalate storage tank 2, and a lithium tetrafluoroborate tank 6. The chlorosilane storage tank 1 is located upstream of the first dynamic micro-channel reactor 5, and the chlorosilane in the chlorosilane storage tank 1 is pumped into the first dynamic micro-channel reactor 5 through a first feeding pump 3. The oxalate storage tank 2 is located upstream of the first dynamic micro-channel reactor 5, and the first mixed solution of oxalate and ester solvent is stored in the oxalate storage tank 2 and pumped into the first dynamic micro-channel reactor 5 through a second feeding pump 4. The lithium tetrafluoroborate tank 6 is located upstream of the second dynamic micro-channel reactor 8, and the second mixed solution of lithium tetrafluoroborate and ester solvent is stored in the lithium tetrafluoroborate tank 6 and pumped into the second dynamic micro-channel reactor 8 through a third feeding pump 7. Thus, the continuous production of lithium difluorooxalate borate can be realized, the production efficiency is improved, and the prepared lithium difluorooxalate borate has high quality and low impurity content.

[0084] In summary, the device for continuously preparing lithium difluorooxalate borate provided in the present application uses two-stage dynamic micro-channel reactors to promote the rapid synthesis of solid chlorinated salt and silicofat in the first dynamic micro-channel reactor 5, reduces the separation process after synthesis, directly enters the second step of fast reaction, and the gas phase is subjected to rectification separation and reuse, the liquid is continuously separated, the impurities enter the solid industrial-grade sodium chloride, the liquid is the qualified product, and the solution of lithium difluorooxalate borate and ester solvent.

[0085] In a third aspect, the present application provides a lithium difluorooxalate borate solution, the lithium difluorooxalate borate solution comprising lithium difluorooxalate borate and ester solvent, the lithium difluorooxalate borate solution being prepared by the method for continuously preparing lithium difluorooxalate borate according to the first aspect of the present application. Thus, the lithium difluorooxalate borate solution provided by the present application can realize continuous production, improve production efficiency, and the lithium difluorooxalate borate prepared has high quality and low impurity content.

[0086] According to some embodiments of the present application, the mass fraction of lithium difluorooxalate borate is 10% to 35%, for example, it can be 10%, 15%, 16%, 17%, 18%, 19%, 20%, 30%, 35%, etc., based on the total mass of the lithium difluorooxalate borate solution. Thus, the continuous production of lithium difluorooxalate borate can be realized, the production efficiency is improved, and the lithium difluorooxalate borate prepared has high quality and low impurity content.

[0087] According to some embodiments of the present application, the mass fraction 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., based on the total mass of the lithium difluorooxalate borate solution. Thus, by controlling the mass fraction of impurity lithium chloride in the lithium difluorooxalate borate solution within the above range, the continuous production of lithium difluorooxalate borate can be realized, the production efficiency is improved, and the lithium difluorooxalate borate prepared has high quality and low impurity content.

[0088] According to some embodiments of the present application, the mass fraction 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., based on the total mass of the lithium difluorooxalate borate solution. Thus, by controlling the content of impurity tetrafluoroborate in the lithium difluorooxalate borate solution within the above range, the lithium difluorooxalate borate has high quality and low impurity content, and when used in a battery, it can better improve the high-temperature cycle performance and high-temperature storage performance of the battery.

[0089] The embodiments of the present application are described in detail below. It should be noted that the embodiments described below are exemplary and are used to explain the present application, and cannot be understood as a limitation of the present application. In addition, if not specifically stated, all reagents used in the following examples are commercially available or can be synthesized according to the methods described herein or known methods, and the reaction conditions not listed are also readily available to those skilled in the art.

[0090] Example 1

[0091] The entire system is pressurized to 0.6 MPa with high-pressure nitrogen, and the pressure of the entire device is stabilized at 0.8 MPa through the back pressure system.

[0092] 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 a speed of 90 r / min.

[0093] In the feeding system, sodium oxalate was stirred with DMC solvent in the kettle to form a uniform liquid with a sodium oxalate mass fraction of 10% (first mixed liquid), and then the first mixed liquid and chlorosilane were simultaneously introduced into the first dynamic microchannel reactor, with a mass flow ratio of 6:1, and a reaction residence time of 20 min. Then the reacted mixed liquid was introduced into the second dynamic microchannel reactor, and lithium tetrafluoroborate solution was simultaneously added into the second dynamic microchannel reactor, with a lithium tetrafluoroborate mass fraction of 9% in the DMC solution of lithium tetrafluoroborate, a molar ratio of silicon oxalate to lithium tetrafluoroborate of 1:1.02, and a reaction residence time of 5 min.

[0094] In the post-processing unit, the material from the second dynamic microchannel reactor was introduced into the flash tank, chlorosilane, fluorosilane and DMC mixed gas were discharged from the gas phase, and the liquid was introduced into the continuous centrifuge to form 15% moisture content of sodium chloride solid and product solution. The 15% moisture content of sodium chloride solid was dried to obtain sodium chloride by-product, with a mass fraction of 99.55% of sodium chloride, a mass fraction of 0.07% of lithium chloride, and a mass fraction of 0.38% of sodium tetrafluoroborate. The product solution was detected as 19.9% of lithium bisfluoroxalate borate, with a mass fraction of 4 ppm of lithium chloride, a mass fraction of 10 ppm of tetrafluoroborate (lithium tetrafluoroborate and sodium tetrafluoroborate), and the rest being solvent DMC.

[0095] Examples 2-36

[0096] The method for continuously preparing lithium bisfluoroxalate borate in Examples 2-36 was the same as in Example 1, and the differences are shown in Table 1. In Example 30, the tetrafluoroborate was lithium tetrafluoroborate and potassium tetrafluoroborate, and the by-product obtained was potassium chloride. That is, in Table 2, the chloride salt in Example 30 was potassium chloride, and the chloride salt in the remaining examples and comparative examples was sodium chloride.

[0097] Comparative Example 1

[0098] Sodium oxalate was stirred with DMC solvent in the kettle to form a uniform liquid with a sodium oxalate mass fraction of 10% (first mixed liquid), and then the first mixed liquid was mixed with chlorosilane, with a mass ratio of 6:1, at 90°C and 0.8 MPa for 20 min to obtain a mixed liquid.

[0099] The mixed solution is separated to obtain a sodium chloride solution, a silicofat oxalate solution, a lithium tetrafluoroborate DMC solution, and the mass ratio of lithium tetrafluoroborate in the lithium tetrafluoroborate DMC solution is 10%, and the molar ratio of silicofat oxalate to lithium tetrafluoroborate is 1:1.02, and the reaction is carried out at 40°C for 5 min to obtain a reaction solution.

[0100] The reaction solution is subjected to flash evaporation, the flash evaporation temperature is 110°C, chlorosilane, fluorosilane and DMC mixed gas are discharged from the gas phase, and the liquid enters a centrifuge at a speed of 90 r / min to form 15% sodium chloride solids and a product solution with a moisture content of 15%, and the 15% sodium chloride solids are dried to obtain sodium chloride by-products, and the product solution is a solution of difluoroboric lithium oxalate and ester solvent.

[0101] Comparative Examples 2-7

[0102] The method for continuously preparing difluoroboric lithium oxalate of Comparative Examples 2-7 is the same as that of Example 1, and the differences are shown in Table 1. Among them, the mass flow ratio of the first mixed solution to chlorosilane in Comparative Examples 2 and 3 is not within the range defined in the present application, the reaction temperature in the second dynamic microchannel reactor of Comparative Examples 4 and 5 is not within the range defined in the present application, and the rotation speed in the second dynamic microchannel reactor of Comparative Examples 6 and 7 is not within the range defined in the present application.

[0103]

[0104]

[0105] The chromatogram of the solution of difluoroboric lithium oxalate and ester solvent prepared in Example 1 is shown in Figure 3 It can be seen that the solution of difluoroboric lithium oxalate and ester solvent prepared in Example 1 of the present application has high quality.

[0106] The components of the sodium chloride by-products and the solution of difluoroboric lithium oxalate and ester solvent of Example 1-36 and Comparative Examples 1-7 are determined respectively, and the test results are shown in Table 2.

[0107] 1. Component determination of sodium chloride by-products:

[0108] Sample pretreatment (dilution / filtering with deionized water), and Li is detected by ICP (inductively coupled plasma) + (chromatographic column: CS12A), BF4 is detected in IC anion mode - (chromatographic column: AS11-HC), corresponding to the mass ratio of lithium chloride and the mass ratio of tetrafluoroborate.

[0109] 2. Component determination of the solution of difluoroboric lithium oxalate and ester solvent:

[0110] Sample pretreatment (deionized water dilution / filtering), using IC ion chromatograph to detect F-and oxalate content, corresponding to the conversion into lithium difluorooxalate borate mass ratio.

[0111] The test results are shown in Table 2.

[0112]

[0113]

[0114] Conclusion:

[0115] As can be seen from Table 2, in Examples 1-36, the continuous preparation method of lithium difluorooxalate borate is adopted, and the ratio of the reactants of the first reaction, the temperature and the rotation speed of the second reaction are controlled, so that the continuous production of lithium difluorooxalate borate can be realized, the production efficiency is improved, and the quality of the prepared lithium difluorooxalate borate is high, and sodium chloride or potassium chloride by-products can be obtained. Comparative Example 1 is not prepared by the continuous method, and the quality of the obtained lithium difluorooxalate borate is lower; Comparative Examples 2-7 do not simultaneously control the ratio of the reactants of the first reaction, the temperature and the rotation speed of the second reaction, and the quality of the obtained lithium difluorooxalate borate is lower and the impurity content is high.

[0116] Compared with Example 1, the first reaction time is shorter in Example 10, and the second reaction time is shorter in Example 23, so the reaction is insufficient, causing the first dynamic microchannel reactor and the second dynamic microchannel reactor to be mismatched in working hours, the content of lithium difluorooxalate borate in the solution of lithium difluorooxalate borate and ester solvent is reduced, the mass fraction of oxalate in Example 6 is reduced, and the mass fraction of lithium tetrafluoroborate in Example 19 is reduced, so the reaction is insufficient, causing the first dynamic microchannel reactor and the second dynamic microchannel reactor to be mismatched in working hours, the content of lithium difluorooxalate borate in the solution of lithium difluorooxalate borate and ester solvent is reduced.

[0117] Compared with Example 1, the first reaction time and the second reaction time are both longer in Example 25, causing the side reaction to increase, so that the content of by-products such as lithium fluoride and tetrafluoroborate in the solution of lithium difluorooxalate borate and ester solvent obtained is increased; in Example 35, the amount-of-substance ratio of oxalic acid silicon grease and lithium tetrafluoroborate is increased, the flash evaporation temperature is increased, and the rotation speed of continuous centrifugation is increased, causing the side reaction to increase, so that the content of by-products such as lithium fluoride and tetrafluoroborate in the solution of lithium difluorooxalate borate and ester solvent obtained is increased; in Example 36, the amount-of-substance ratio of oxalic acid silicon grease and lithium tetrafluoroborate is reduced, the flash evaporation temperature is reduced, and the rotation speed of continuous centrifugation is reduced, which also causes the side reaction to increase, so that the content of by-products such as lithium fluoride and tetrafluoroborate in the solution of lithium difluorooxalate borate and ester solvent obtained is increased.

[0118] In the description of the specification, the description of the terms "one embodiment", "some embodiments", "an example", "a specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in connection with the embodiment or example are contained in at least one embodiment or example of the present application. In the specification, the illustrative description of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any appropriate manner in any one or more embodiments or examples. In addition, the person skilled in the art can combine and combine the different embodiments or examples described in the specification and the features of the different embodiments or examples without contradiction.

[0119] Although the embodiments of the present application have been shown and described above, it is understood that the above-described embodiments are exemplary and are not to be construed as limiting the present application, and the person skilled in the art can make changes, modifications, replacements and variations to the above-described embodiments within the scope of the present application.

Claims

1. A method for continuous preparation of lithium difluorooxalate borate, characterized in that, include: A first mixture of oxalate and ester solvent and chlorosilane are continuously pumped into a first dynamic microchannel reactor to carry out a first reaction to obtain a reaction product, wherein the mass flow rate ratio of the first mixture to the chlorosilane is (4~10):1; The reaction product is continuously pumped into a second dynamic microchannel reactor, and a second mixture formed by lithium tetrafluoroborate and ester solvent is continuously pumped into the second dynamic microchannel reactor. The second reaction is carried out at a temperature of 20℃~70℃ and a rotation speed of 200r / min~400r / min to obtain a mixed reaction solution. The reaction products in the mixed reaction solution are separated to obtain lithium difluorooxalate borate; In the first mixture, the mass percentage of oxalate is less than or equal to 20%; In the second mixture, the mass percentage of lithium tetrafluoroborate is less than or equal to 20%; The ratio of the amount of oxalate silicone grease in the reaction product to the amount of lithium tetrafluoroborate in the second mixture is 1:(1~1.05).

2. The method for continuous preparation of lithium difluorooxalate borate 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 0.5 MPa to 1 MPa; The temperature of the first reaction is 50℃~120℃.

3. The method for continuous preparation of lithium difluorooxalate borate according to claim 1, characterized in that, The method satisfies at least one of the following conditions: The oxalate is selected from at least one of sodium oxalate and potassium oxalate; The ester solvent is selected from at least one of dimethyl carbonate, ethyl methyl carbonate, and diethyl carbonate; The stirring speed for the first reaction is 200 r / min to 400 r / min; The Reynolds number of the fluid in the first dynamic microchannel reactor is greater than or equal to 10,000; The reaction time for 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 takes 1 to 10 minutes.

4. The method for continuous preparation of lithium difluorooxalate borate according to any one of claims 1 to 3, characterized in that, The step of separating the reaction products in the mixed reaction solution includes: The mixed reaction solution was flash evaporated 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 difluorooxalate borate and an ester solvent.

5. The method for continuous preparation of lithium difluorooxalate borate according to claim 4, characterized in that, The method satisfies at least one of the following conditions: The flash evaporation temperature is 110℃~120℃; The rotation speed of the continuous centrifugation is 60 r / min to 120 r / min; The flash evaporation pressure is 0.5 MPa to 1 MPa; The pressure of the continuous centrifugation is 0.5MPa~1MPa.

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