A method for continuous production of lithium difluorooxalate borate using a microchannel reactor

Abstract

This invention discloses a method for the continuous production of lithium difluorooxalate borate using a microchannel reactor, comprising the following steps: lithium fluoride is added to a solvent, the temperature is maintained at 10-20°C, and the mixture is stirred until homogeneous to obtain a lithium fluoride solution; the lithium fluoride solution, boron trifluoride gas, oxalic acid, boron trichloride gas, and silicon tetrachloride are respectively introduced into the microchannel reactor; the gas at the top is absorbed by a multi-stage falling film to form a hydrochloric acid solution, and the silicon tetrafluoride gas reacts with the hydrofluoric acid solution to generate hexafluorosilicic acid; the solution leaving the bottom of the reactor is degassed by negative pressure heating, cooled for crystallization, filtered, and dried to obtain a qualified product. The reaction of this invention occurs continuously in the microchannel reactor, which, compared to intermittent reactions, significantly reduces energy consumption and raw material consumption for the same production capacity, eliminates many intermediate equipment, and lowers investment costs.

Description

Technical Field

[0001] This invention relates to the field of chemical production technology, and in particular to a method for the continuous production of lithium difluorooxalate borate using a microchannel reactor. Background Technology

[0002] In lithium-ion batteries, commonly used electrolyte lithium salts include lithium hexafluorophosphate (LiPF6) and lithium tetrafluoroborate (LiBF4). While LiPF6 is commercially available, it is sensitive to temperature and moisture; the decomposition products generated by heating can corrode the cathode material. Although LiBF4 exhibits good performance at low temperatures, its ionic conductivity is low at high temperatures, and it is difficult to form a stable SEI at the interface, limiting the application of these two lithium salts. Therefore, there is a need to develop a lithium salt with stable high and low temperature performance and good compatibility with both cathode and anode materials. Lithium difluorooxalate borate (LiBF2C2O4) has a structure that is half lithium tetrafluoroborate and half lithium dioxalate borate, combining the advantages of good film-forming properties of lithium dioxalate borate and good low-temperature performance of lithium tetrafluoroborate. It is a promising lithium salt that could replace lithium hexafluorophosphate, with huge market potential.

[0003] CN202211073466.5 discloses a method for preparing lithium difluorooxalate borate, belonging to the field of lithium difluorooxalate borate production. This invention synthesizes lithium difluorooxalate borate by reacting lithium fluoride with hydrogen fluoride solution, oxalic acid, and boron trichloride gas. The reaction has a high conversion rate, high product yield, does not introduce new impurities, is easy to purify, and yields high-purity lithium difluorooxalate borate. The process is short and has low industrial production costs. However, this reaction is intermittent, resulting in low production efficiency, and the investment cost is also relatively high. Summary of the Invention

[0004] This invention provides a method for the continuous production of lithium difluorooxalate borate using a microchannel reactor, which solves the problem of low production efficiency in existing lithium difluorooxalate borate production.

[0005] To solve the above-mentioned technical problems, the technical solution provided by the present invention is as follows:

[0006] A method for the continuous production of lithium difluorooxalate borate using a microchannel reactor includes the following steps:

[0007] (1) Take lithium fluoride, add it to the solvent, keep the temperature at 10-20℃, stir evenly to obtain lithium fluoride solution;

[0008] (2) Lithium fluoride solution, boron trifluoride gas, oxalic acid, boron trichloride gas and silicon tetrachloride are respectively introduced into the microchannel reactor. The microchannel reactor is provided with a first-stage microchannel tube, a second-stage microchannel tube, a third-stage microchannel tube and a fourth-stage microchannel tube connected in sequence from top to bottom. Lithium fluoride solution is introduced into the top of the first-stage microchannel tube, boron trifluoride gas is introduced into the top of the second-stage microchannel tube and the third-stage microchannel tube respectively, oxalic acid is introduced into the top of the third-stage microchannel tube, boron trichloride gas is introduced into the top and bottom of the fourth-stage microchannel tube respectively, and silicon tetrachloride is introduced into the top of the fourth-stage microchannel tube.

[0009] (3) The gas at the top is absorbed by a multi-stage falling film to form a hydrochloric acid solution, and the silicon tetrafluoride gas reacts with the hydrofluoric acid solution to generate hexafluorosilicic acid.

[0010] (4) The solution leaving the bottom of the reactor is degassed by heating under negative pressure, then cooled to crystallize, filtered and dried to obtain a qualified product.

[0011] The main chemical reaction formulas of this invention are as follows:

[0012] BF3 + LiF = LiBF4

[0013] 2 / 3BCl3+H2C2O4+LiBF4=LiBC2O4F2+2 / 3BF3+2HCl

[0014] 1 / 2SiCl4+H2C2O4+LiBF4= LiBC2O4F2+1 / 2SiF4+2HCl

[0015] BF3 + LiF = LiBF4

[0016] In step (1), the solvent is dimethyl carbonate, and the mass percentage concentration of the lithium fluoride solution is 4-6%.

[0017] In step (2), the flow rate ratio of boron trifluoride gas introduced into the top of the secondary microchannel tube to lithium fluoride solution introduced into the top of the primary microchannel tube is 1:(12-14).

[0018] In step (2), the flow rate ratio of boron trifluoride gas introduced into the top of the third-stage microchannel tube to lithium fluoride solution introduced into the top of the first-stage microchannel tube is 1:(15-18).

[0019] In step (2), the flow rate ratio of oxalic acid to lithium fluoride solution introduced into the top of the primary microchannel tube is 1:(6-7).

[0020] In step (2), the flow rate ratio of silicon tetrachloride to lithium fluoride solution introduced into the top of the primary microchannel tube is 1:(12-14).

[0021] In step (2), the flow ratio of boron trichloride introduced into the microchannel reactor to lithium fluoride solution introduced into the top of the first-stage microchannel tube is 1:(12-14), and the flow ratio of boron trichloride introduced into the top and bottom of the fourth-stage microchannel tube is 3:1.

[0022] The reaction temperature of the primary and secondary microchannel tubes is 15-30℃, and the reaction temperature of the tertiary and quaternary microchannel tubes is 30-50℃.

[0023] The secondary, tertiary, and quaternary microchannel tubes are equipped with a first gas distribution mechanism at their tops. Boron trifluoride gas and boron trichloride gas delivery pipes are respectively connected to the first gas distribution mechanism. The first gas distribution mechanism includes a first gas distribution tube with a downward-opening gas delivery port. A secondary gas distribution mechanism is provided below the gas delivery port. The longitudinal section of the secondary gas distribution mechanism is an inverted frustum-shaped cone.

[0024] The fourth-stage microchannel tube is provided with a second gas distribution mechanism at the top. The second gas distribution includes a second gas distribution tube, which is connected to a delivery tube. A gas distribution plate in the shape of an inverted cone is provided below the delivery tube.

[0025] The technical solution provided by this invention has the following advantages compared with the prior art:

[0026] 1. The reaction of this invention occurs continuously in a microchannel reactor. Compared with intermittent reactions, the same production capacity is achieved by significantly reducing energy consumption and raw material consumption. It also eliminates the need for many intermediate equipment and reduces investment costs.

[0027] 2. No other impurities are generated during the reaction process of this invention. At the same time, both boron trichloride and boron trifluoride are gases, which can easily leave the reaction system and will not have an adverse effect on product quality, thus improving product purity from the source. During the reaction process, the amount of oxalic acid added is controlled to be slightly less than the equilibrium amount to ensure that the reaction is complete, which will also not have an adverse effect on product quality.

[0028] 3. The microchannel reactor in this invention can achieve continuous reaction, and the reaction tube is surrounded by a heat-removing medium, which can effectively remove the heat generated by the reaction, resulting in high safety.

[0029] 4. The present invention simultaneously adds silicon tetrachloride and boron trichloride, which enhances the reaction and reduces the reaction time. Attached Figure Description

[0030] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other embodiments can be obtained based on these drawings without creative effort.

[0031] Figure 1 This is a schematic diagram of the microchannel reactor of the present invention;

[0032] Figure 2 for Figure 1 Enlarged view of part A in the middle;

[0033] Figure 3 This is a schematic diagram of the structure of the second gas distribution mechanism in this invention.

[0034] In the diagram, 1. Reactor shell, 2. Primary microchannel tube, 3. Secondary microchannel tube, 4. Tertiary microchannel tube, 5. Quaternary microchannel tube, 6. Gas exhaust tube, 7. Reaction product outlet tube, 8. First gas distribution tube, 9. Secondary gas distribution mechanism, 10. Secondary gas distribution tube, 11. Gas distribution plate, 12. Delivery tube, 13. Connecting column. Detailed Implementation

[0035] The technical solution of the present invention will be clearly and completely described below with reference to specific embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Example 1

[0036] This embodiment provides a method for the continuous production of lithium difluorooxalate borate using a microchannel reactor, comprising the following steps:

[0037] (1) Take lithium fluoride, add it to dimethyl carbonate, keep the temperature at 15°C, stir until homogeneous, and obtain a lithium fluoride solution with a mass percentage concentration of 5%;

[0038] (2) Lithium fluoride solution, boron trifluoride gas, oxalic acid, boron trichloride gas and silicon tetrachloride are respectively introduced into the microchannel reactor. The microchannel reactor is provided with a first-stage microchannel tube, a second-stage microchannel tube, a third-stage microchannel tube and a fourth-stage microchannel tube connected in sequence from top to bottom. Lithium fluoride solution is introduced into the top of the first-stage microchannel tube, boron trifluoride gas is introduced into the top of the second-stage microchannel tube and the third-stage microchannel tube respectively, oxalic acid is introduced into the top of the third-stage microchannel tube, boron trichloride gas is introduced into the top and bottom of the fourth-stage microchannel tube respectively, and silicon tetrachloride is introduced into the top of the fourth-stage microchannel tube.

[0039] (3) The gas at the top is absorbed by a multi-stage falling film to form a hydrochloric acid solution, and the silicon tetrafluoride gas reacts with the hydrofluoric acid solution to generate hexafluorosilicic acid.

[0040] (4) The solution leaving the bottom of the reactor is depressurized by a vacuum pump and heated by a temperature regulating tank for degassing and concentration. The temperature is controlled at about 60°C. About 40% of the dimethyl carbonate is removed and recovered and reused by a condenser. The remaining gas enters the tail gas treatment device for concentration by activated carbon adsorption. After desorption, it is outsourced for processing. Then, it is cooled and crystallized at about 10°C for 5 hours to obtain lithium difluorooxalate borate filtrate. The crystallized solution is filtered by a two-in-one filter press to obtain crude lithium difluorooxalate borate. The dimethyl carbonate filtrate after filtration is transferred to a solvent recovery storage tank for recycling. The semi-finished crude lithium difluorooxalate borate is placed in a vacuum rake dryer at 130°C and vacuum-dried under absolute negative pressure for 10 hours to obtain finished lithium difluorooxalate borate. The organic gas is first deeply condensed and recovered. The remaining gas enters the tail gas treatment device for concentration by activated carbon adsorption. After desorption, it is outsourced for processing.

[0041] In step (2), the flow ratio of boron trifluoride gas introduced into the top of the secondary microchannel tube to lithium fluoride solution introduced into the top of the primary microchannel tube is 1:13; the flow ratio of boron trifluoride gas introduced into the top of the tertiary microchannel tube to lithium fluoride solution introduced into the top of the primary microchannel tube is 1:17; the flow ratio of oxalic acid introduced into the primary microchannel tube to lithium fluoride solution introduced into the top of the primary microchannel tube is 1:6.5; in step (2), the flow ratio of silicon tetrachloride introduced into the primary microchannel tube to lithium fluoride solution introduced into the top of the primary microchannel tube is 1:13; the flow ratio of boron trichloride introduced into the microchannel reactor to lithium fluoride solution introduced into the top of the primary microchannel tube is 1:13; and the flow ratio of boron trichloride introduced into the top and bottom of the quaternary microchannel tube is 3:1.

[0042] The reaction temperature of the first-stage and second-stage microchannel tubes is 21°C, and the reaction temperature of the third-stage and fourth-stage microchannel tubes is 40°C.

[0043] The microchannel reactor in this embodiment is as follows: Figures 1-3As shown, the reactor includes a reactor shell 1. Inside the reactor shell 11, from top to bottom, there are sequentially connected primary microchannel tubes 2, secondary microchannel tubes 3, tertiary microchannel tubes 4, and quaternary microchannel tubes 5. A gas discharge pipe 6 is provided at the top of the reactor shell 1, and a reaction product outflow pipe 7 is provided at the bottom of the reactor shell 1. A first gas distribution mechanism is provided at the top of the secondary microchannel tubes 3, tertiary microchannel tubes 4, and quaternary microchannel tubes 5. Boron trifluoride gas and boron trichloride gas delivery pipes 12 are respectively connected to the first gas distribution mechanism. The first gas distribution mechanism includes a first gas distribution tube 8, which has a downward-opening gas delivery port. A secondary gas distribution mechanism 9 is provided below the gas delivery port. The longitudinal section of the secondary gas distribution mechanism 9 is an inverted frustum-shaped cone with a channel that is wider at the top and narrower at the bottom, which improves the gas inflow speed and further avoids channel blockage.

[0044] The top of the fourth-stage microchannel tube 5 is provided with a second gas distribution mechanism. The second gas distribution includes a second gas distribution tube 10, which is connected to a delivery tube 12. Below the delivery tube 12 is a gas distribution plate 11 in the shape of an inverted cone. A connecting column 13 is provided between the gas distribution plate 11 and the delivery tube 12, which prolongs the residence time of the BCl3 gas introduced into the bottom of the microchannel reactor in the reactor.

[0045] In this embodiment, the reaction to generate lithium tetrafluoroborate is a gas-solid reaction, which takes place in the primary microchannel tube 2 and the secondary microchannel tube 3 at the top of the reactor. The reaction to generate the target product takes place in the tertiary microchannel tube 4 and the quaternary microchannel tube 5 at the bottom of the reactor. Both reactions can take place in the intermediate transition region.

[0046] In addition, the organic gases in the separation process of the product of this invention are recovered through multi-stage condensation, and the residual gas enters the tail gas treatment device for adsorption by activated carbon before being discharged in an environmentally friendly manner; the filtrate is directly returned to the system for reuse. Example 2

[0047] This embodiment provides a method for the continuous production of lithium difluorooxalate borate using a microchannel reactor, comprising the following steps:

[0048] (1) Take lithium fluoride, add it to dimethyl carbonate, keep the temperature at 10°C, stir until homogeneous, and obtain a lithium fluoride solution with a mass percentage concentration of 6%;

[0049] (2) Lithium fluoride solution, boron trifluoride gas, oxalic acid, boron trichloride gas and silicon tetrachloride are respectively introduced into the microchannel reactor. The microchannel reactor is provided with a first-stage microchannel tube, a second-stage microchannel tube, a third-stage microchannel tube and a fourth-stage microchannel tube connected in sequence from top to bottom. Lithium fluoride solution is introduced into the top of the first-stage microchannel tube, boron trifluoride gas is introduced into the top of the second-stage microchannel tube and the third-stage microchannel tube respectively, oxalic acid is introduced into the top of the third-stage microchannel tube, boron trichloride gas is introduced into the top and bottom of the fourth-stage microchannel tube respectively, and silicon tetrachloride is introduced into the top of the fourth-stage microchannel tube.

[0050] (3) The gas at the top is absorbed by a multi-stage falling film to form a hydrochloric acid solution, and the silicon tetrafluoride gas reacts with the hydrofluoric acid solution to generate hexafluorosilicic acid.

[0051] (4) The solution leaving the bottom of the reactor is depressurized by a vacuum pump and heated by a temperature regulating tank for degassing and concentration. The temperature is controlled at about 60°C. About 40% of the dimethyl carbonate is removed and recovered and reused by a condenser. The remaining gas enters the tail gas treatment device for concentration by activated carbon adsorption. After desorption, it is outsourced for processing. Then, it is cooled and crystallized at about 10°C for 5 hours to obtain lithium difluorooxalate borate filtrate. The crystallized solution is filtered by a two-in-one filter press to obtain crude lithium difluorooxalate borate. The dimethyl carbonate filtrate after filtration is transferred to a solvent recovery storage tank for recycling. The semi-finished crude lithium difluorooxalate borate is placed in a vacuum rake dryer at 130°C and vacuum-dried under absolute negative pressure for 10 hours to obtain finished lithium difluorooxalate borate. The organic gas is first deeply condensed and recovered. The remaining gas enters the tail gas treatment device for concentration by activated carbon adsorption. After desorption, it is outsourced for processing.

[0052] In step (2), the flow ratio of boron trifluoride gas introduced into the top of the secondary microchannel tube to lithium fluoride solution introduced into the top of the primary microchannel tube is 1:12; the flow ratio of boron trifluoride gas introduced into the top of the tertiary microchannel tube to lithium fluoride solution introduced into the top of the primary microchannel tube is 1:18; the flow ratio of oxalic acid introduced into the primary microchannel tube to lithium fluoride solution introduced into the top of the primary microchannel tube is 1:6; in step (2), the flow ratio of silicon tetrachloride introduced into the primary microchannel tube to lithium fluoride solution introduced into the top of the primary microchannel tube is 1:14; the flow ratio of boron trichloride introduced into the microchannel reactor to lithium fluoride solution introduced into the top of the primary microchannel tube is 1:12; and the flow ratio of boron trichloride introduced into the top and bottom of the quaternary microchannel tube is 3:1.

[0053] The reaction temperature of the first-stage and second-stage microchannel tubes is 15°C, and the reaction temperature of the third-stage and fourth-stage microchannel tubes is 50°C.

[0054] The microchannel reactor in this embodiment is the same as that in Example 1. Example 3

[0055] This embodiment provides a method for the continuous production of lithium difluorooxalate borate using a microchannel reactor, comprising the following steps:

[0056] (1) Take lithium fluoride, add it to dimethyl carbonate, keep the temperature at 20°C, stir until homogeneous, and obtain a lithium fluoride solution with a mass percentage concentration of 4%;

[0057] (2) Lithium fluoride solution, boron trifluoride gas, oxalic acid, boron trichloride gas and silicon tetrachloride are respectively introduced into the microchannel reactor. The microchannel reactor is provided with a first-stage microchannel tube, a second-stage microchannel tube, a third-stage microchannel tube and a fourth-stage microchannel tube connected in sequence from top to bottom. Lithium fluoride solution is introduced into the top of the first-stage microchannel tube, boron trifluoride gas is introduced into the top of the second-stage microchannel tube and the third-stage microchannel tube respectively, oxalic acid is introduced into the top of the third-stage microchannel tube, boron trichloride gas is introduced into the top and bottom of the fourth-stage microchannel tube respectively, and silicon tetrachloride is introduced into the top of the fourth-stage microchannel tube.

[0058] (3) The gas at the top is absorbed by a multi-stage falling film to form a hydrochloric acid solution, and the silicon tetrafluoride gas reacts with the hydrofluoric acid solution to generate hexafluorosilicic acid.

[0059] (4) The solution leaving the bottom of the reactor is depressurized by a vacuum pump and heated by a temperature regulating tank for degassing and concentration. The temperature is controlled at about 60°C. About 40% of the dimethyl carbonate is removed and recovered and reused by a condenser. The remaining gas enters the tail gas treatment device for concentration by activated carbon adsorption. After desorption, it is outsourced for processing. Then, it is cooled and crystallized at about 10°C for 5 hours to obtain lithium difluorooxalate borate filtrate. The crystallized solution is filtered by a two-in-one filter press to obtain crude lithium difluorooxalate borate. The dimethyl carbonate filtrate after filtration is transferred to a solvent recovery storage tank for recycling. The semi-finished crude lithium difluorooxalate borate is placed in a vacuum rake dryer at 130°C and vacuum-dried under absolute negative pressure for 10 hours to obtain finished lithium difluorooxalate borate. The organic gas is first deeply condensed and recovered. The remaining gas enters the tail gas treatment device for concentration by activated carbon adsorption. After desorption, it is outsourced for processing.

[0060] In step (2), the flow ratio of boron trifluoride gas introduced into the top of the secondary microchannel tube to lithium fluoride solution introduced into the top of the primary microchannel tube is 1:14; the flow ratio of boron trifluoride gas introduced into the top of the tertiary microchannel tube to lithium fluoride solution introduced into the top of the primary microchannel tube is 1:15; the flow ratio of oxalic acid introduced into the primary microchannel tube to lithium fluoride solution introduced into the top of the primary microchannel tube is 1:7; in step (2), the flow ratio of silicon tetrachloride introduced into the primary microchannel tube to lithium fluoride solution introduced into the top of the primary microchannel tube is 1:12; the flow ratio of boron trichloride introduced into the microchannel reactor to lithium fluoride solution introduced into the top of the primary microchannel tube is 1:14; and the flow ratio of boron trichloride introduced into the top and bottom of the quaternary microchannel tube is 3:1.

[0061] The reaction temperature of the first-stage microchannel tube and the second-stage microchannel tube is 30°C, and the reaction temperature of the third-stage microchannel tube and the fourth-stage microchannel tube is 30°C.

[0062] The microchannel reactor in this embodiment is the same as that in Example 1.

[0063] Comparative Example 1

[0064] This embodiment provides a method for the continuous production of lithium difluorooxalatoborate using a microchannel reactor. In this embodiment, boron trichloride gas is introduced only at the top of the four-stage microchannel tube. All other steps are the same as in Embodiment 1, and the microchannel reactor used is also the same as in Embodiment 1.

[0065] The flow rate ratio of boron trichloride introduced into the microchannel reactor to lithium fluoride solution introduced into the top of the primary microchannel tube is 1:9.7.

[0066] Comparative Example 2

[0067] This embodiment provides a method for the continuous production of lithium difluorooxalatoborate using a microchannel reactor. In this embodiment, silicon tetrachloride is introduced only at the top of the four-stage microchannel tube. All other steps are the same as in Example 1, and the microchannel reactor used is also the same as in Example 1.

[0068] The flow rate ratio of silicon tetrachloride introduced into the microchannel reactor to lithium fluoride solution introduced into the top of the primary microchannel tube is 1:6.7.

[0069] Performance testing

[0070] The performance of lithium difluorooxalate borate prepared in Examples 1-3 and Comparative Examples 1 and 2 was tested, and the results are as follows.

[0071]

[0072] Purity was tested using ion chromatography, free acid was tested using potentiometric titration, and the content of metal impurities was tested using inductively coupled plasma atomic emission spectrometry.

[0073] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for continuous production of lithium difluorooxalate borate using a microchannel reactor, characterized in that... Includes the following steps: (1) Take lithium fluoride, add it to the solvent, keep the temperature at 10-20℃, stir evenly to obtain lithium fluoride solution; (2) Lithium fluoride solution, boron trifluoride gas, oxalic acid, boron trichloride gas and silicon tetrachloride are respectively introduced into the microchannel reactor. The microchannel reactor is provided with a first-stage microchannel tube, a second-stage microchannel tube, a third-stage microchannel tube and a fourth-stage microchannel tube connected in sequence from top to bottom. Lithium fluoride solution is introduced into the top of the first-stage microchannel tube, boron trifluoride gas is introduced into the top of the second-stage microchannel tube and the third-stage microchannel tube respectively, oxalic acid is introduced into the top of the third-stage microchannel tube, boron trichloride gas is introduced into the top and bottom of the fourth-stage microchannel tube respectively, and silicon tetrachloride is introduced into the top of the fourth-stage microchannel tube. (3) The gas at the top is absorbed by a multi-stage falling film to form a hydrochloric acid solution, and the silicon tetrafluoride gas reacts with the hydrofluoric acid solution to generate hexafluorosilicic acid. (4) The solution leaving the bottom of the reactor is degassed by heating under negative pressure, then cooled to crystallize, filtered and dried to obtain a qualified product.

2. The method for continuous production of lithium difluorooxalate borate using a microchannel reactor according to claim 1, characterized in that: In step (1), the solvent is dimethyl carbonate, and the mass percentage concentration of the lithium fluoride solution is 4-6%.

3. A method for continuous production of lithium difluorooxalate borate using a microchannel reactor according to claim 1, characterized in that: In step (2), the flow rate ratio of boron trifluoride gas introduced into the top of the secondary microchannel tube to lithium fluoride solution introduced into the top of the primary microchannel tube is 1:(12-14).

4. A method for continuous production of lithium difluorooxalate borate using a microchannel reactor according to claim 1, characterized in that: In step (2), the flow rate ratio of boron trifluoride gas introduced into the top of the third-stage microchannel tube to lithium fluoride solution introduced into the top of the first-stage microchannel tube is 1:(15-18).

5. A method for continuous production of lithium difluorooxalate borate using a microchannel reactor according to claim 1, characterized in that: In step (2), the flow rate ratio of oxalic acid to lithium fluoride solution introduced into the top of the primary microchannel tube is 1:(6-7).

6. A method for continuous production of lithium difluorooxalate borate using a microchannel reactor according to claim 1, characterized in that: In step (2), the flow rate ratio of the silicon tetrachloride introduced to the lithium fluoride solution introduced to the top of the primary microchannel tube is 1:(12-14).

7. A method for continuous production of lithium difluorooxalate borate using a microchannel reactor according to claim 1, characterized in that: In step (2), the flow ratio of boron trichloride introduced into the microchannel reactor to lithium fluoride solution introduced into the top of the first-stage microchannel tube is 1:(12-14), and the flow ratio of boron trichloride introduced into the top and bottom of the fourth-stage microchannel tube is 3:

1.

8. A method for continuous production of lithium difluorooxalate borate using a microchannel reactor according to claim 1, characterized in that: The reaction temperature of the first-stage and second-stage microchannel tubes is 15-30℃, and the reaction temperature of the third-stage and fourth-stage microchannel tubes is 30-50℃.

9. A method for continuous production of lithium difluorooxalate borate using a microchannel reactor according to claim 1, characterized in that: The top of the secondary, tertiary, and quaternary microchannel tubes is provided with a first gas distribution mechanism, and the delivery pipes for boron trifluoride gas and boron trichloride gas are respectively connected to the first gas distribution mechanism; the first gas distribution mechanism includes a first gas distribution tube, which has a downward-opening gas delivery port, and a secondary gas distribution mechanism is provided below the gas delivery port; the longitudinal section of the secondary gas distribution mechanism is an inverted frustum-shaped cone.

10. A method for continuous production of lithium difluorooxalate borate using a microchannel reactor according to claim 1, characterized in that: The top of the four-stage microchannel tube is provided with a second gas distribution mechanism, which includes a second gas distribution tube connected to a delivery tube, and a gas distribution plate in the shape of an inverted cone is provided below the delivery tube.

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