Lithium hexafluorophosphate solution, and preparation method therefor and device therefor

Abstract

The present application relates to the technical field of chemical engineering, and provides a lithium hexafluorophosphate solution, and a preparation method therefor and a device therefor. The method comprises: performing a first contact reaction on a first phosphorus pentafluoride gas and a lithium fluoride solution to obtain a first reaction product; performing a second contact reaction on the first reaction product and a second phosphorus pentafluoride gas to obtain a second reaction product; and performing a third contact reaction on the second reaction product and a third phosphorus pentafluoride gas to obtain the lithium hexafluorophosphate solution. The phosphorus pentafluoride gas is step-fed, such that the feeding ratio of phosphorus pentafluoride to lithium fluoride can be dynamically and accurately controlled; and according to the reaction kinetic characteristics, the reaction process is optimized, and the chemical reaction speed between phosphorus pentafluoride and lithium fluoride is accelerated, so the lithium hexafluorophosphate solution can be efficiently synthesized in a short time, and the purity and the yield of the lithium hexafluorophosphate solution are improved.

Description

Lithium hexafluorophosphate solution and its preparation method and apparatus

[0001] Priority information

[0002] This application claims priority and benefits to patent application No. 202411024282.9, filed with the China National Intellectual Property Administration on July 29, 2024, the entire contents of which are incorporated herein by reference. Technical Field

[0003] This application relates to the field of chemical technology, specifically to lithium hexafluorophosphate solution and its preparation method and apparatus, and more specifically, to a process for preparing lithium hexafluorophosphate solution. Background Technology

[0004] Lithium-ion batteries possess advantages such as high plateau voltage, good cycle performance, wide operating temperature range, high energy density, and no memory effect, making them widely used in mobile communications, portable electronic products, power tools, and weaponry. They also show great promise for application in electric vehicles. The electrolyte and its constituent electrolytes are key raw materials for lithium batteries and directly affect the performance of the manufactured batteries. Therefore, the electrolyte must meet the following requirements: high conductivity, stable chemical and electrochemical properties, wide operating temperature range, and low price. Lithium hexafluorophosphate meets these requirements and can be used as an excellent electrolyte; however, lithium hexafluorophosphate products are subject to strict requirements and limitations regarding purity, moisture content, and free acid content.

[0005] Currently, the industrial production of lithium hexafluorophosphate mainly relies on the chemical reaction between phosphorus pentafluoride (PF5) and lithium fluoride (LiF), especially in the presence of anhydrous hydrofluoric acid. This strategy greatly promotes the efficient conversion of lithium fluoride to the target product, lithium hexafluorophosphate. However, this existing method has significant limitations: First, while anhydrous hydrofluoric acid helps accelerate the reaction process and increase the effective utilization rate of lithium fluoride, it leads to excessively high concentrations of acid radicals in the final crystallized product and increases the content of insoluble matter. This not only reduces product stability and increases potential corrosivity but may also affect its practical application in fields such as lithium battery electrolytes. Second, the traditional batch reactor operation method makes it difficult to achieve precise control of the reaction process, easily generating side reactions and further exacerbating problems with product purity and yield.

[0006] In addition, the insoluble content in the lithium hexafluorophosphate currently prepared is all above 30 ppm. The presence of a large amount of insoluble matter will have a certain impact on the batteries prepared in the subsequent process. For example, it may clog the battery separator, increase the resistance to ion migration, and thus reduce the power performance and rate performance of the battery. Furthermore, if the content of insoluble matter is too high, it may increase the risk of internal short circuits in the battery and reduce the safety performance of the battery.

[0007] Therefore, it is urgent to develop, design, and implement a completely new process that eliminates the use of anhydrous hydrofluoric acid, effectively regulates the acid-base balance of the reaction system, and significantly reduces the content of insoluble matter and residual acidity in lithium hexafluorophosphate crystals, thereby obtaining high-quality products. Summary of the Invention

[0008] This application aims to address at least one of the technical problems existing in the prior art, to at least some extent.

[0009] In a first aspect, this application discloses a method for preparing a lithium hexafluorophosphate solution. According to an embodiment of this application, the method includes: subjecting a first phosphorus pentafluoride gas to a lithium fluoride solution in a first contact reaction to obtain a first reaction product; subjecting the first reaction product to a second phosphorus pentafluoride gas in a second contact reaction to obtain a second reaction product; and subjecting the second reaction product to a third phosphorus pentafluoride gas in a third contact reaction to obtain the lithium hexafluorophosphate solution; wherein the first contact reaction, the second contact reaction, and the third contact reaction are carried out in a microchannel reactor; and the lithium fluoride solution comprises lithium fluoride and a carbonate solvent.

[0010] This application achieves dynamic and precise control of the feed ratio of phosphorus pentafluoride and lithium fluoride by segmented feeding of phosphorus pentafluoride gas. The reaction process is optimized based on the reaction kinetics characteristics, which accelerates the chemical reaction rate between phosphorus pentafluoride and lithium fluoride. This enables the efficient synthesis of lithium hexafluorophosphate solution in a short time and improves the purity and yield of the lithium hexafluorophosphate solution.

[0011] According to embodiments of this application, the method further includes at least one of the following additional technical features:

[0012] According to an embodiment of this application, the molar ratio of the first phosphorus pentafluoride gas, the second phosphorus pentafluoride gas, and the third phosphorus pentafluoride gas is 1:(2-4):(5-8).

[0013] According to an embodiment of this application, the total time of the first contact reaction time, the second contact reaction time, and the third contact reaction time is not less than 0.2 min.

[0014] According to the embodiments of this application, the total time of the first contact reaction time, the second contact reaction time, and the third contact reaction time is 0.2 min to 7 min.

[0015] According to an embodiment of this application, the temperature of the first contact reaction is 20–70°C.

[0016] According to an embodiment of this application, the temperature of the second contact reaction is 30–80°C.

[0017] According to an embodiment of this application, the temperature of the third contact reaction is 40–90°C.

[0018] According to an embodiment of this application, the content of lithium fluoride in the lithium fluoride solution is less than 20%.

[0019] According to an embodiment of this application, the diameter of the lithium fluoride is less than 200 μm.

[0020] According to embodiments of this application, the carbonate solvent includes at least one of methyl ethyl carbonate, dimethyl carbonate, diethyl carbonate, ethyl acetate, butyl acetate, ethyl propionate, ethyl butyrate, and ethyl benzoate.

[0021] According to an embodiment of this application, the lithium fluoride solution is obtained by: mixing lithium fluoride to be mixed with a carbonate solvent to obtain a mixed product; and subjecting the mixed product to a first filtration process to obtain the lithium fluoride solution.

[0022] According to an embodiment of this application, the Dv50 of the lithium fluoride to be mixed is less than 200 μm.

[0023] According to an embodiment of this application, the first filtration process is performed in a metal filter.

[0024] According to an embodiment of this application, after the third contact reaction, the process further includes: aging the product of the third contact reaction, performing a second filtration process, and purifying the product to obtain the lithium hexafluorophosphate solution.

[0025] According to an embodiment of this application, the aging process is carried out in an aging reactor.

[0026] According to an embodiment of this application, the second filtration process is performed in a precision filter.

[0027] According to an embodiment of this application, the purification process is carried out in an ion exchange resin.

[0028] In a second aspect, this application provides an apparatus for preparing lithium hexafluorophosphate solution. According to an embodiment of this application, the apparatus includes: a reactor having a plurality of reaction plates connected in sequence; each of the plurality of reaction plates includes at least one inlet and at least one outlet.

[0029] The apparatus described in this application overcomes the shortcomings of traditional batch reactors. This apparatus not only enables precise control of reaction conditions but also allows for dynamic adjustment of the ratio of phosphorus pentafluoride gas to lithium fluoride through segmented feeding based on reaction kinetics. This improves the controllability of the entire synthesis process, enhances raw material utilization and product quality consistency, and achieves efficient, continuous, and green synthesis of lithium hexafluorophosphate. Therefore, this apparatus significantly improves product quality and yield, reduces overall production costs, and increases production efficiency. Simultaneously, it balances economic and environmental benefits, playing a crucial role in promoting the sustainable development of the new energy battery industry.

[0030] According to embodiments of this application, the device may further include at least one of the following additional technical features:

[0031] According to an embodiment of this application, it further includes: a mixing unit for mixing lithium fluoride with a carbonate solvent, the mixing unit being connected to the inlet of one of the plurality of reaction plates.

[0032] According to an embodiment of this application, it further includes: a first filtration unit, the first filtration unit being disposed between the mixing unit and the reactor, the mixing unit being in communication with the first filtration unit, and the first filtration unit being in communication with the inlet of one of the plurality of reaction plates.

[0033] According to an embodiment of this application, a plurality of reaction plates are arranged sequentially in the same direction, and the mixing unit or the first filtering unit is connected to the inlet of the reaction plate located at the end.

[0034] According to an embodiment of this application, it further includes: a segmented temperature control unit, the segmented temperature control unit being used to control the temperature of the reaction plate.

[0035] According to an embodiment of this application, it further includes: an aging unit, the aging unit being connected to the outlet of the reaction plate located at the other end.

[0036] According to an embodiment of this application, it further includes: a second filtering unit, which is connected to the aging unit.

[0037] According to an embodiment of this application, it further includes: a purification unit, which is connected to the second filtration unit.

[0038] In a third aspect, this application discloses a lithium hexafluorophosphate solution. According to embodiments of this application, the lithium hexafluorophosphate solution is prepared using the method described in the first aspect or the apparatus described in the second aspect. As previously stated, the method of this application can improve the purity and yield of the lithium hexafluorophosphate solution, effectively enhance the mass transfer effect and reaction rate between solid and liquid, improve raw material utilization and reaction efficiency, and achieve continuous and rapid generation of lithium hexafluorophosphate solution for industrial production. Therefore, the lithium hexafluorophosphate solution obtained by this method has high purity and does not require subsequent separation and purification; it can be directly used as a product for further processing.

[0039] According to the embodiments of this application, the content of insoluble matter in the solution is not higher than 10 ppm. The lithium hexafluorophosphate solution of this application has high purity and can meet the stringent requirements of high-end lithium battery electrolytes for the purity of lithium hexafluorophosphate.

[0040] According to embodiments of this application, the lithium hexafluorophosphate solution may further include at least one of the following additional technical features:

[0041] According to an embodiment of this application, the acidity of the lithium hexafluorophosphate solution is less than 100 ppm.

[0042] According to embodiments of this application, the content of non-lithium ion metal impurities is no higher than 5 ppm.

[0043] According to an embodiment of this application, the insoluble substance is lithium fluoride.

[0044] In a fourth aspect, this application discloses a lithium hexafluorophosphate. According to an embodiment of this application, the lithium hexafluorophosphate is obtained by crystallizing the lithium hexafluorophosphate solution described in the third aspect. The lithium hexafluorophosphate of this application has high purity, is suitable for preparing high-end lithium battery electrolytes, and can meet the high standards demanded by the market.

[0045] Additional aspects and advantages of this application will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of this application. Attached Figure Description

[0046] The above and / or additional aspects and advantages of this application will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, in which:

[0047] Figure 1 is a flowchart of the preparation of lithium hexafluorophosphate solution according to an embodiment of this application;

[0048] Figure 2 is a flowchart of the preparation of lithium hexafluorophosphate solution according to an embodiment of this application;

[0049] Figure 3 is a flowchart of the preparation of lithium hexafluorophosphate solution according to an embodiment of this application;

[0050] Figure 4 is a flowchart of the preparation of lithium hexafluorophosphate solution according to an embodiment of this application;

[0051] Figure 5 is a schematic diagram of a reactor for preparing lithium hexafluorophosphate solution according to an embodiment of this application;

[0052] Figure 6 is a schematic diagram of the reaction plate in the reactor for preparing lithium hexafluorophosphate solution according to an embodiment of this application;

[0053] Figure 7 is a schematic diagram 1 of an apparatus for preparing lithium hexafluorophosphate solution according to an embodiment of this application;

[0054] Figure 8 is a schematic diagram of an apparatus for preparing lithium hexafluorophosphate solution according to an embodiment of this application;

[0055] Figure 9 is a schematic diagram of an apparatus for preparing lithium hexafluorophosphate solution according to an embodiment of this application;

[0056] Figure 10 is a schematic diagram of an apparatus for preparing lithium hexafluorophosphate solution according to an embodiment of this application;

[0057] Figure 11 is a schematic diagram of an apparatus for preparing lithium hexafluorophosphate solution according to an embodiment of this application;

[0058] Figure reference numerals: 01 Reactor; 001 Reaction plate; 002 Heat exchange layer; 003 Reaction layer; 02 Mixing unit; 03 First filtration unit; 04 Aging unit; 05 Second filtration unit; 06 Purification unit. Detailed Implementation

[0059] The embodiments of the technical solution of this application are described in detail below. The following embodiments are only used to illustrate the technical solution of this application more clearly, and are therefore only examples, and should not be used to limit the scope of protection of this application.

[0060] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0061] For the sake of brevity, this article only discloses some specific numerical ranges. However, any lower limit can be combined with any upper limit to form an unspecified range; and any lower limit can be combined with other lower limits to form an unspecified range, just as any upper limit can be combined with any other upper limit to form an unspecified range. Furthermore, each individually disclosed point or single value can itself serve as a lower or upper limit and be combined with any other point or single value or with other lower or upper limits to form an unspecified range.

[0062] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the application; the terms “comprising” and “having”, and any variations thereof, in the specification, claims, and foregoing description of the drawings are intended to cover non-exclusive inclusion.

[0063] In this document, it should be understood that the terms “center,” “longitudinal,” “lateral,” “length,” “width,” “thickness,” “upper,” “lower,” “front,” “rear,” “left,” “right,” “vertical,” “horizontal,” “top,” “bottom,” “inner,” “outer,” “clockwise,” “counterclockwise,” “axial,” “radial,” and “circumferential” indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application.

[0064] In this document, unless otherwise expressly specified and limited, terms such as "installation," "connection," "joining," and "fixing" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components, unless otherwise expressly limited. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0065] In this document, unless otherwise expressly specified and limited, "above" or "below" the second feature can mean that the first and second features are in direct contact, or that the first and second features are in indirect contact through an intermediate medium. Furthermore, "above," "on top of," and "over" the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0066] In this document, the terms “comprising” or “including” are open-ended expressions, meaning that they include the contents specified in this application but do not exclude other contents.

[0067] It should be noted that the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. Furthermore, in the description of this application, unless otherwise stated, "multiple" means two or more.

[0068] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0069] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0070] Method for preparing lithium hexafluorophosphate solution

[0071] In one aspect of this application, a method for preparing the lithium hexafluorophosphate solution described in the first aspect is provided. According to an embodiment of this application, referring to Figure 1, the method includes:

[0072] S100: First contact reaction

[0073] In this step, phosphorus pentafluoride gas is reacted with a lithium fluoride solution to obtain a first reaction product. The lithium fluoride solution comprises lithium fluoride and a carbonate solvent.

[0074] In some embodiments of this application, the content of lithium fluoride in the lithium fluoride solution is less than 20%. For example, it can be, but is not limited to, 5%–20% or 10%–20%, specifically 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, or 20%. By controlling the ratio of lithium fluoride to carbonate solvent, the mass transfer effect and reaction rate between solid and liquid can be effectively enhanced, and the utilization rate of raw materials and reaction efficiency can be improved.

[0075] In some embodiments of this application, the diameter of the lithium fluoride is less than 200 μm. Therefore, it is possible to reduce solid accumulation in subsequent reactions and improve product quality.

[0076] S200: Second contact reaction

[0077] In this step, the first reaction product is reacted with a second phosphorus fluoride gas in a second contact reaction to obtain a second reaction product.

[0078] S300: Third Contact Reaction

[0079] In this step, the second reaction product is reacted with a third phosphorus pentafluoride gas in a third contact reaction to obtain the lithium hexafluorophosphate solution.

[0080] This application achieves dynamic and precise control of the feed ratio of phosphorus pentafluoride and lithium fluoride solution by segmented feeding of phosphorus pentafluoride gas. The reaction process is optimized based on the reaction kinetics characteristics, which accelerates the chemical reaction rate between phosphorus pentafluoride and lithium fluoride solution. This enables efficient synthesis of lithium hexafluorophosphate solution in a short time and improves the purity and yield of lithium hexafluorophosphate solution.

[0081] In some embodiments of this application, the molar ratio of the first, second, and third phosphorus pentafluoride gases is 1:(2-4):(5-8). For example, but not limited to, ratios of 1:2:5, 1:2:6, 1:2:7, 1:2:8, 1:3:5, 1:3:6, 1:3:7, 1:3:8, 1:4:6, 1:4:7, and 1:4:8 are possible. The same phosphorus pentafluoride gas is introduced into three spaces of equal volume. By controlling the molar ratio of the three phosphorus pentafluoride gases, different concentrations of phosphorus pentafluoride gas are achieved in the three spaces. Because there is a violent exothermic reaction between phosphorus pentafluoride gas and lithium fluoride, improper control of the reaction conditions may lead to runaway reaction, affecting not only the reaction yield and product purity but also posing safety hazards to the production process. To avoid this situation, the applicant adopted a more refined reaction control strategy: in the initial stage of the reaction, a lithium fluoride solution required for the entire reaction is introduced, meaning the lithium fluoride concentration is relatively high, thereby reducing the concentration of phosphorus pentafluoride gas. This imbalance in reactant concentrations helps to suppress the rapid progress of the reaction. Because under these conditions, there is a large amount of lithium fluoride and relatively little phosphorus pentafluoride gas, the reaction tends to proceed slowly and steadily. As the reaction proceeds, the applicant gradually adjusts the proportions of reactants, increasing the amount of phosphorus pentafluoride gas added while correspondingly decreasing the concentration of the lithium fluoride solution. The purpose of this is to promote the smooth completion of the entire reaction process. When the reactant concentrations are closer to the stoichiometric ratio, the reaction rate also increases accordingly, thereby improving the overall reaction efficiency and reducing the content of insoluble matter.

[0082] The reaction between phosphorus pentafluoride gas and lithium fluoride solution takes place within the channels of the reaction plates in a microchannel reactor, thus enabling a continuous reaction. The first, second, and third phosphorus pentafluoride gases refer to the phosphorus pentafluoride gases introduced into the channels of different reaction plates, respectively. Since the channel volume in each reaction plate is the same, by controlling their molar ratio, the concentration of phosphorus pentafluoride gas introduced into the channels of different reaction plates can be varied.

[0083] A microchannel reactor, also known as a microreactor, is a miniature reactor manufactured using precision machining technology, containing numerous micrometer-sized microchannels. Essentially, a microchannel reactor is a continuous-flow tubular reactor, including mixers, heat exchangers, reactors, and controllers required in chemical processing units. This application does not strictly limit the specific type of microchannel reactor; it can be any conventional type disclosed in the art, such as the Corning G3 / G4 / G5 dynamic microchannel reactor or the Guizhou Microchemical HL-300 microchannel reactor.

[0084] In some embodiments of this application, the total time of the first contact reaction, the second contact reaction, and the third contact reaction is not less than 0.2 min. Therefore, it is possible to ensure sufficient contact and efficient conversion between phosphorus pentafluoride and lithium fluoride solutions, and to reduce the content of insoluble matter.

[0085] In some embodiments of this application, the total time for the first contact reaction time, the second contact reaction time, and the third contact reaction time is 0.2 min to 7 min, for example, but not limited to 0.2 min, 1 min, 1.5 min, 2 min, 2.5 min, 3 min, 3.5 min, 4 min, 4.5 min, 5 min, etc. Therefore, it is possible to ensure sufficient contact and efficient conversion between phosphorus pentafluoride and lithium fluoride solutions, and to reduce the content of insoluble matter. Since the phosphorus pentafluoride and lithium fluoride solutions react in the channels of the reaction plates in the microchannel reactor, the first contact reaction time, the second contact reaction time, and the third contact reaction time refer to the time it takes for the phosphorus pentafluoride gas to flow through the reaction plates after the first, second, and third phosphorus pentafluoride gases are introduced into the channels of different reaction plates, respectively. The total time refers to the total time it takes for the phosphorus pentafluoride gas to flow from the first reaction plate to the twelfth reaction plate.

[0086] To avoid the use of hydrogen fluoride in subsequent processes and to simplify the subsequent separation process, the applicant introduced an organic solvent strategy in which lithium fluoride is insoluble and the organic solvent is not acidic. Therefore, the reaction process can avoid creating an excessively acidic environment and can simplify the solid-liquid separation process in the post-reaction processing stage through physical separation. Excessive insoluble by-products can be removed through efficient filtration, thereby substantially improving the purity and yield of lithium hexafluorophosphate.

[0087] Therefore, the organic solvent is selected from carbonate solvents. The lithium fluoride solution is obtained as follows (referring to Figure 2): the lithium fluoride to be mixed is pre-treated with a carbonate solvent (S400) to obtain a mixed product; the mixed product is then subjected to a first filtration process (S500) to obtain the lithium fluoride solution. The choice of carbonate avoids the use of anhydrous hydrofluoric acid, a strong acid, thus effectively avoiding potential problems caused by an excessively acidic environment, such as equipment corrosion and safety hazards. Secondly, lithium fluoride itself is insoluble in carbonates, while the final product, lithium hexafluorophosphate, is soluble in carbonates. This difference in solubility allows for subsequent separation and purification. Specifically, after the reaction, insoluble impurities generated during the reaction, such as unreacted lithium fluoride, can be easily removed using a simple solid-liquid separation process, especially high-efficiency filtration technology. This not only reduces the content of insoluble matter but also significantly improves the purity and yield of lithium hexafluorophosphate, allowing the final product to be directly used as a solution for further processing. In addition, solid-liquid separation is performed through the first filtration process to ensure that the diameter of solid particles in the filtered solution is below 200 micrometers, thereby reducing the accumulation of solids in subsequent reactions and improving product quality.

[0088] In some embodiments of this application, the Dv50 of the lithium fluoride to be mixed is less than 200 μm. By controlling the particle size of the lithium fluoride, the mass transfer between the solid and liquid phases and the reaction rate can be effectively enhanced, thereby improving the utilization rate of raw materials and the reaction efficiency.

[0089] In this application, the volume average particle size Dv50 refers to the particle size corresponding to a cumulative volume distribution percentage of 50%. For example, the volume average particle size Dv50 test method can refer to the standard GB / T 19077-2016 and be measured using a laser particle size analyzer (e.g., Malvern Master Size 3000).

[0090] In some embodiments of this application, before mixing lithium fluoride with carbonate solvents, the process further includes: drying the lithium fluoride for S600 (as shown in Figure 3) to remove moisture from the lithium fluoride. The drying process is carried out in a drying kettle for 0.1–10 hours at a temperature of 100–140°C.

[0091] In some embodiments of this application, the carbonate solvents include, but are not limited to, at least one of methyl ethyl carbonate, dimethyl carbonate, diethyl carbonate, ethyl acetate, butyl acetate, ethyl propionate, ethyl butyrate, and ethyl benzoate.

[0092] In some embodiments of this application, the first contact reaction, the second contact reaction, and the third contact reaction are carried out in a microchannel reactor. By combining continuous reactor technology and a segmented feed operation mode, replacing the traditional batch reactor, dynamic and precise control of the feed ratio of phosphorus pentafluoride and lithium fluoride solutions can be achieved, and the reaction process can be optimized based on reaction kinetics. This method ensures the continuity and stability of the synthesis process, not only improving the efficiency of the synthesis process but also significantly improving the consistency and quality of the product and reducing the content of insoluble matter.

[0093] In some embodiments of this application, the temperature of the first contact reaction is 20–70°C. For example, but not limited to, it can be 20°C, 25°C, 30°C, 35°C, 40°C, 45°C, 50°C, 55°C, 60°C, 65°C, or 70°C.

[0094] In some embodiments of this application, the temperature of the second contact reaction is 30–80°C. For example, it can be, but is not limited to, 30°C, 35°C, 40°C, 45°C, 50°C, 55°C, 60°C, 65°C, 70°C, 75°C, or 80°C.

[0095] In some embodiments of this application, the temperature of the third contact reaction is 40–90°C. For example, but not limited to, it can be 40°C, 45°C, 50°C, 55°C, 60°C, 65°C, 70°C, 75°C, 80°C, 85°C, or 90°C.

[0096] By controlling the temperature of the contact reactions at different stages, the temperatures of the first, second, and third contact reactions are gradually increased. This method is beneficial for activating the reaction kinetics and promoting the reaction in the forward direction. Specifically, in the initial stage of the reaction, the required lithium fluoride solution for the entire reaction is introduced, meaning the lithium fluoride feed concentration is relatively high. At this time, phosphorus pentafluoride gas is introduced. Due to the advantage of the reactant concentration, the reaction can proceed at a relatively fast rate without the need to increase the temperature further. As the reaction proceeds, the concentration of the lithium fluoride solution gradually decreases. To ensure the smooth completion of the reaction, the applicant adopts a temperature-increasing strategy. By adjusting the temperature in a timely manner, the reaction can be effectively promoted in the forward direction, preventing the reaction from stalling due to the decrease in the feed concentration.

[0097] In some embodiments of this application, the first filtration process is performed in a metal filter. Therefore, it is possible to reduce the diameter of lithium fluoride in the solution to less than 200 μm.

[0098] In some embodiments of this application, after the third contact reaction, the process further includes: aging the product of the third contact reaction S700, second filtration S800, and purification S900 (as shown in Figure 4) to obtain the lithium hexafluorophosphate solution. The aging treatment allows unreacted phosphorus pentafluoride gas and lithium fluoride solution to continue reacting, thereby increasing product yield and reducing the generation of insolubles. The second filtration treatment removes insolubles from the product, reducing their content. The purification treatment allows the product to pass through an ion exchange resin, reducing the content of non-lithium ion metal impurities. Therefore, the final product has an acidity of less than 100 ppm, lithium fluoride insolubles of no more than 10 ppm, and non-lithium ion metal impurities of no more than 5 ppm. The prepared lithium hexafluorophosphate solution can be directly used as a product for further preparation, meeting the stringent purity requirements of high-end lithium battery electrolytes for lithium hexafluorophosphate.

[0099] In some embodiments of this application, the aging process is carried out in an aging reactor. The back pressure of the gas phase in the aging reactor is between 0.2 and 2 MPa, the aging time is between 0.2 and 200 min, and the aging temperature is between 20 and 80°C. Therefore, the unreacted phosphorus pentafluoride gas and lithium fluoride can continue to react fully.

[0100] In some embodiments of this application, the back pressure of the gas phase in the aging vessel may be, but is not limited to, 0.2 MPa, 0.5 MPa, 0.7 MPa, 0.9 MPa, 1 MPa, 1.2 MPa, 1.4 MPa, 1.5 MPa, 1.6 MPa, 1.8 MPa, or 2 MPa.

[0101] In some embodiments of this application, the aging treatment time may be, but is not limited to, 0.2 min, 1 min, 10 min, 20 min, 30 min, 40 min, 50 min, 60 min, 70 min, 80 min, 90 min, 100 min, 110 min, 120 min, 130 min, 140 min, 150 min, 160 min, 170 min, 180 min, 190 min, or 200 min.

[0102] In some embodiments of this application, the aging treatment temperature may be, but is not limited to, 20°C, 25°C, 30°C, 35°C, 40°C, 45°C, 50°C, 55°C, 60°C, 65°C, 70°C, 75°C, or 80°C.

[0103] In some embodiments of this application, the second filtration process is performed in a precision filter. Therefore, the content of insoluble matter can be reduced, enabling the parameters of the target product to meet or exceed market requirements, thereby satisfying the stringent purity requirements of high-end lithium battery electrolytes for lithium hexafluorophosphate.

[0104] In some embodiments of this application, the purification process is carried out in an ion exchange resin. Therefore, by passing the product through an ion exchange resin for ion exchange, the content of non-lithium ion metal impurities in the product can be reduced.

[0105] The preparation method of this application, in the raw material pretreatment stage, effectively enhances the mass transfer effect and reaction rate between solid and liquid by strictly controlling key parameters such as the ratio of lithium fluoride to carbonate solvent and the particle size of lithium fluoride powder, thereby improving raw material utilization and reaction efficiency. In the reaction stage, by combining a continuous flow microchannel reactor and segmented feeding operation, the molar ratio of phosphorus pentafluoride gas in each segment can be precisely controlled. The reaction kinetics are simultaneously optimized by utilizing concentration gradients and temperature gradients, accelerating the chemical reaction rate between phosphorus pentafluoride and lithium fluoride, and efficiently synthesizing lithium hexafluorophosphate in a short time. Therefore, this process realizes the direct synthesis of solid, liquid, and gas phases in the reaction system, avoiding the intermediate steps and energy consumption that may exist in traditional methods, and directly generating liquid lithium salt, which is conducive to reducing overall production costs and improving production efficiency.

[0106] Apparatus for preparing lithium hexafluorophosphate solution

[0107] This application discloses an apparatus for preparing lithium hexafluorophosphate solution. According to an embodiment of this application, referring to FIG5, the apparatus includes: a reactor 01 having a plurality of reaction plates 001 connected in sequence, each of the reaction plates including at least one inlet and at least one outlet. The reactor 01 is adapted to perform a first contact reaction between a first phosphorus pentafluoride gas and a lithium fluoride solution to obtain a first reaction product; to perform a second contact reaction between the first reaction product and a second phosphorus pentafluoride gas to obtain a second reaction product; and to perform a third contact reaction between the second reaction product and a third phosphorus pentafluoride gas to obtain the lithium hexafluorophosphate solution.

[0108] The structure of reaction plate 001, as shown in Figure 6, consists of two heat exchange layers 002 and a reaction layer 003. The reaction layer 003 has channels with two inlets and one outlet. The inlets and outlets of the reaction layer 003 are used to introduce reactants. Adjacent reaction plates 001 are connected to the inlets of the other reaction plate via the outlet on one reaction layer 003. When the other inlet on the reaction layer 003 is not in use, it can be blocked with a plug. When it is necessary to introduce other substances into the reaction layer, a pipe can be connected to introduce the required substances.

[0109] The apparatus described in this application overcomes the shortcomings of traditional batch reactors. This apparatus not only enables precise control of reaction conditions but also allows for dynamic adjustment of the phosphorus pentafluoride to lithium fluoride ratio based on reaction kinetics through segmented feeding. This improves the controllability of the entire synthesis process, enhances raw material utilization and product quality consistency, and achieves efficient, continuous, and green synthesis of lithium hexafluorophosphate. Therefore, this apparatus significantly improves product quality and yield, reduces overall production costs, and increases production efficiency.

[0110] In some embodiments of this application, a mixing unit 02, referring to FIG. 7, is further included for mixing lithium fluoride with a carbonate solvent. The mixing unit 02 is connected to the inlet of one of the plurality of reaction plates 001. The mixing unit 02 is not specifically limited, as long as it can achieve sufficient mixing of lithium fluoride and carbonate solvent. For example, the mixing unit 02 can be a mixing device consisting of a static mixer and a kettle-type agitator. The static mixer is internally configured with special structural elements such as SK, SX, and SY types to promote sufficient dispersion of materials. The kettle-type agitator is used for slurry preparation, ensuring that the lithium fluoride particles are uniformly dispersed in the carbonate solvent while the lithium fluoride is also wetted by the carbonate solvent.

[0111] In some embodiments of this application, the system further includes a first filtration unit 03. Referring to FIG8, the first filtration unit 03 is disposed between the mixing unit 02 and the reactor 01. The mixing unit 02 is connected to the first filtration unit 03, and the first filtration unit 03 is connected to the inlet of one of the plurality of reaction plates. The first filtration unit 03 is not specifically limited, as long as it can separate the solid and liquid components of the product mixed by the mixing unit 02, ensuring that the diameter of the solid particles in the filtered solution is all below 200 micrometers. For example, the first filtration unit 03 can be a metal filter.

[0112] In some embodiments of this application, a plurality of reaction plates 001 are arranged sequentially in the same direction, and the mixing unit 02 or the first filtering unit 03 is connected to the inlet of the reaction plate 001 located at the end.

[0113] In some embodiments of this application, a segmented temperature control unit is further included. This segmented temperature control unit is located outside or inside the reaction plate 001 and is used to control the temperature of the channels within the reaction plate. Through the segmented temperature control unit, independent temperature control of each reaction plate can be achieved, allowing different stages of the contact reaction to occur at different temperatures. This achieves a progressively increasing heating method to meet the temperature requirements of the reaction, promoting the forward reaction, and improving reaction efficiency and product quality.

[0114] It should be noted that the segmented temperature control unit can be controlled by one instrument to control the temperature of multiple reaction plates, or by multiple instruments to control the temperature of each reaction plate, as long as the segmented temperature control unit can control the temperature of each reaction plate individually.

[0115] In some embodiments of this application, an aging unit 04 is further included. Referring to FIG. 9, the aging unit 04 is connected to the outlet of the reaction plate 001 located at the other end. The aging unit 04 is not specifically limited, as long as it can mature the product. Exemplarily, the aging unit 04 is selected from an aging reactor.

[0116] In some embodiments of this application, a second filtration unit 05 is further included. Referring to FIG10, the second filtration unit 05 is connected to the aging unit 04. The second filtration unit 05 is not specifically limited, as long as it can reduce the content of insoluble matter in the product. Exemplarily, the second filtration unit 05 is selected from a precision filter.

[0117] In some embodiments of this application, a purification unit 06 is further included, referring to FIG11, wherein the purification unit is connected to the second filtration unit 05. The purification unit 06 is not specifically limited, as long as it can reduce the content of non-lithium ion metal impurities in the product. Exemplarily, the purification unit 06 is selected from ion exchange resins.

[0118] Lithium hexafluorophosphate solution, lithium hexafluorophosphate

[0119] This application discloses a lithium hexafluorophosphate solution. According to embodiments of this application, the lithium hexafluorophosphate solution is prepared using the aforementioned method. As described above, the method described in this application can effectively enhance the mass transfer between solid and liquid phases and the reaction rate, improve raw material utilization and reaction efficiency, and enable the continuous and rapid generation of lithium hexafluorophosphate solution for industrial production. Therefore, the lithium hexafluorophosphate solution obtained by this method has high purity, low insoluble matter and acidity, facilitating subsequent separation and purification.

[0120] In some embodiments of this application, the insoluble content in the solution is no higher than 10 ppm. The lithium hexafluorophosphate solution of this application has a low insoluble content. By controlling the insoluble content in the lithium hexafluorophosphate solution, the quality of the lithium hexafluorophosphate product is improved, ensuring the performance of subsequent batteries, reducing the risk of internal short circuits in the battery, and improving the battery's safety performance.

[0121] It should be noted that "insoluble matter" refers to lithium fluoride.

[0122] In some embodiments of this application, the lithium hexafluorophosphate solution may further include at least one of the following additional technical features:

[0123] In some embodiments of this application, the acidity of the lithium hexafluorophosphate solution is below 100 ppm. Therefore, the stability of the lithium hexafluorophosphate solution can be improved, its corrosiveness reduced, thereby improving product quality.

[0124] In some embodiments of this application, the content of non-lithium-ion metal impurities is no higher than 5 ppm. These non-lithium-ion metal impurities refer to sodium ions, potassium ions, iron ions, magnesium ions, calcium ions, or nickel ions, etc. Therefore, reducing impurity ions can improve the performance of lithium hexafluorophosphate solution in the electrolyte, preventing impurity ions from participating in electrochemical reactions, forming an inactive layer within the battery that reduces battery capacity and efficiency, and interfering with lithium-ion conduction, thus affecting battery charge and discharge performance.

[0125] This application discloses a lithium hexafluorophosphate. According to an embodiment of this application, the lithium hexafluorophosphate is obtained by crystallizing the aforementioned lithium hexafluorophosphate solution. As mentioned above, the lithium hexafluorophosphate solution has high purity, and after crystallization, the lithium hexafluorophosphate also has high purity, making it suitable for preparing high-end lithium battery electrolytes and meeting the high standards demanded by the market.

[0126] The embodiments of this application are described in detail below. The embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application. Where specific techniques or conditions are not specified in the embodiments, they are performed in accordance with the techniques or conditions described in the literature in this field or according to the product instructions. Reagents or instruments used, unless otherwise specified, are all conventional products that can be obtained commercially.

[0127] Example 1

[0128] 30 kg of commercially available high-surface-area porous lithium fluoride (Dv50) with a particle size less than 200 μm was taken. Using a solid-liquid mixing pump, the lithium fluoride was drawn into the pump's suction port and uniformly mixed with 350 kg of diethyl carbonate within the pump. Primary mixing was then performed using a high-efficiency static mixer equipped with special structural elements such as SK, SX, and SY types to promote thorough material dispersion. The material was then fed into a reactor (with a stirred tank) and stirred for 1 hour before being discharged. The material subsequently passed through a metal filter with a pore size of 150 micrometers, yielding a mother liquor. This mother liquor entered a buffer tank and was then pumped into a microchannel reactor at a flow rate maintained at 200 L / h. PF5 was then introduced into the first, fourth, and eighth plates of the microchannel reactor using a gas flow meter, with feed flow rates of 2.9 m³ / h for each plate. 3 / h, 8.75m 3 / h and 17.5m 3The reaction time was 3.2 min, with a total residence time of 3.2 min. The first, second, and third plates were maintained at 50°C; the fourth, fifth, sixth, and seventh plates at 60°C; and the eighth, ninth, tenth, eleventh, and twelfth plates at 75°C. The reacted material was then transferred to an aging reactor with a back pressure of 1.5 MPa, where it remained for 100 min at a controlled temperature of 85°C. The reaction solution was then filtered through a precision filter to obtain a clear lithium hexafluorophosphate solution at 80°C.

[0129] Example 2

[0130] Lithium hexafluorophosphate solution was prepared according to the method described in Example 1, except that in Example 2, a gas flow meter was used to introduce PF5 into the first, fourth, and eighth plates of the microchannel reactor, respectively, with feed flow rates of 2.9 m³ / s into the first, fourth, and eighth plates. 3 / h, 11.6m 3 / h and 23.2m 3 / h.

[0131] Example 3

[0132] Lithium hexafluorophosphate solution was prepared according to the method described in Example 1, except that in Example 3, a gas flow meter was used to introduce PF5 into the first, fourth, and eighth plates of the microchannel reactor, respectively, with feed flow rates of 2.9 m³ / s into the first, fourth, and eighth plates. 3 / h, 5.8m 3 / h and 14.5m 3 / h.

[0133] Example 4

[0134] Lithium hexafluorophosphate solution was prepared according to the method described in Example 1, except that in Example 4, a gas flow meter was used to introduce PF5 into the first, fourth, and eighth plates of the microchannel reactor, respectively, with feed flow rates of 2.9 m³ / s into the first, fourth, and eighth plates. 3 / h, 5.8m 3 / h and 23.2m 3 / h.

[0135] Example 5

[0136] Lithium hexafluorophosphate solution was prepared according to the method described in Example 1, except that in Example 5, a gas flow meter was used to introduce PF5 into the first, fourth, and eighth plates of the microchannel reactor, respectively, with feed flow rates of 2.9 m³ / s into the first, fourth, and eighth plates. 3 / h, 11.6m 3 / h and 14.5m3 / h.

[0137] Example 6

[0138] Lithium hexafluorophosphate solution was prepared according to the method described in Example 1, except that in Example 6, a gas flow meter was used to introduce PF5 into the first, fourth, and eighth plates of the microchannel reactor, respectively, with feed flow rates of 2.9 m³ / s into the first, fourth, and eighth plates. 3 / h, 2.9m 3 / h and 2.9m 3 / h.

[0139] Example 7

[0140] Lithium hexafluorophosphate solution was prepared according to the method described in Example 1, except that in Example 7, a gas flow meter was used to introduce PF5 into the first, fourth, and eighth plates of the microchannel reactor, respectively, with feed flow rates of 2.9 m³ / s into the first, fourth, and eighth plates. 3 / h, 2.9m 3 / h and 29m 3 / h.

[0141] Example 8

[0142] The lithium hexafluorophosphate solution was prepared according to the method described in Example 1, except that the total residence time of the reaction after PF5 was introduced into the microchannel reactor in Example 8 was 0.2 min.

[0143] Example 9

[0144] The lithium hexafluorophosphate solution was prepared according to the method described in Example 1, except that the total residence time of the reaction after PF5 was introduced into the microchannel reactor in Example 9 was 2.5 min.

[0145] Example 10

[0146] The lithium hexafluorophosphate solution was prepared according to the method described in Example 1, except that the total residence time of the reaction after PF5 was introduced into the microchannel reactor in Example 10 was 5 min.

[0147] Example 11

[0148] The lithium hexafluorophosphate solution was prepared according to the method described in Example 1, except that the total residence time of the reaction after PF5 was introduced into the microchannel reactor in Example 11 was 7 min.

[0149] Example 12

[0150] The lithium hexafluorophosphate solution was prepared according to the method described in Example 1, except that the total residence time of the reaction after PF5 was introduced into the microchannel reactor in Example 12 was 0.1 min.

[0151] Example 13

[0152] The lithium hexafluorophosphate solution was prepared according to the method described in Example 13, except that the maintenance temperature of the first, second, and third plates was 20°C, the maintenance temperature of the fourth, fifth, sixth, and seventh plates was 30°C, and the maintenance temperature of the eighth, ninth, tenth, eleventh, and twelfth plates was 40°C.

[0153] Example 14

[0154] The lithium hexafluorophosphate solution was prepared according to the method described in Example 14, except that the maintenance temperature of the first, second, and third plates in Example 14 was 70°C, the maintenance temperature of the fourth, fifth, sixth, and seventh plates was 80°C, and the maintenance temperature of the eighth, ninth, tenth, eleventh, and twelfth plates was 90°C.

[0155] Example 15

[0156] The lithium hexafluorophosphate solution was prepared according to the method described in Example 1, except that in Example 15, the maintenance temperature of the first, second, and third plates was 50°C, the maintenance temperature of the fourth, fifth, sixth, and seventh plates was 50°C, and the maintenance temperature of the eighth, ninth, tenth, eleventh, and twelfth plates was 75°C.

[0157] Example 16

[0158] The lithium hexafluorophosphate solution was prepared according to the method described in Example 16, except that the maintenance temperature of the first, second, and third plates was 30°C, the maintenance temperature of the fourth, fifth, sixth, and seventh plates was 60°C, and the maintenance temperature of the eighth, ninth, tenth, eleventh, and twelfth plates was 75°C.

[0159] Example 17

[0160] The lithium hexafluorophosphate solution was prepared according to the method described in Example 17, except that the maintenance temperature of the first, second, and third plates in Example 17 was 10°C, the maintenance temperature of the fourth, fifth, sixth, and seventh plates was 20°C, and the maintenance temperature of the eighth, ninth, tenth, eleventh, and twelfth plates was 30°C.

[0161] Example 18

[0162] The lithium hexafluorophosphate solution was prepared according to the method described in Example 18, except that the maintenance temperature of the first, second, and third plates in Example 18 was 80°C, the maintenance temperature of the fourth, fifth, sixth, and seventh plates was 90°C, and the maintenance temperature of the eighth, ninth, tenth, eleventh, and twelfth plates was 100°C.

[0163] Example 19

[0164] The lithium hexafluorophosphate solution was prepared according to the method described in Example 1. The difference is that in Example 19, lithium fluoride was drawn into the pump chamber through the pump suction port and mixed uniformly with 350 kg of methyl ethyl carbonate in the pump.

[0165] Example 20

[0166] The lithium hexafluorophosphate solution was prepared according to the method described in Example 1. The difference was that in Example 20, lithium fluoride was drawn into the pump chamber through the pump suction port and mixed uniformly with 350 kg of ethyl acetate in the pump.

[0167] Example 21

[0168] The lithium hexafluorophosphate solution was prepared according to the method described in Example 1. The difference is that in Example 21, lithium fluoride was drawn into the pump chamber through the pump suction port and mixed uniformly with 350 kg of ethyl benzoate in the pump.

[0169] Comparative Example 1

[0170] Lithium hexafluorophosphate solution was prepared according to the method described in Example 1, except that in Comparative Example 1, PF5 gas was only introduced into the first plate. The specific method is as follows:

[0171] The lithium fluoride slurry was prepared according to the method described in Example 1, except that a gas flow meter was used to introduce PF5 into the first plate of the microchannel reactor, and the feed flow rate into the first plate was 29.2 m³ / s. 3 / h. The reaction residence time is 3.2 min. The maintenance temperature of the first, second, and third plates is 50℃, the maintenance temperature of the fourth, fifth, sixth, and seventh plates is 60℃, and the maintenance temperature of the eighth, ninth, tenth, eleventh, and twelfth plates is 75℃. The reacted material enters the aging reactor, with a back pressure of 1.5 MPa, and remains in the reactor for 100 min, controlling the temperature at 85℃. Subsequently, the reaction solution is filtered to obtain a clear lithium hexafluorophosphate solution at 80℃. The reaction solution is then filtered through a precision filter to obtain a clear lithium hexafluorophosphate solution at 80℃.

[0172] Comparative Example 2

[0173] 30 kg of high-surface-area porous lithium fluoride was weighed and added to a reactor, followed by the addition of 350 kg of diethyl carbonate and stirring. After stirring for 1 hour, the mixture was discharged. Then, a 29.2 m³ flow path was introduced into the reactor through a bottom tube. 3 PF5 gas was introduced at a rate of 1.5 MPa / h, and the mixture was held in the reactor for 120 minutes at a controlled temperature of 85°C. The reaction solution was then filtered to obtain a clear lithium hexafluorophosphate solution at 80°C.

[0174] Comparative Example 3

[0175] Lithium hexafluorophosphate solution was prepared according to the method described in Example 1, except that hydrofluoric acid was used as the solvent in Comparative Example 3. The specific method is as follows:

[0176] 30 kg of commercially available high-surface-area porous lithium fluoride (Dv50) with a particle size less than 200 μm was taken. Using a solid-liquid mixing pump, the lithium fluoride was drawn into the pump's suction port and uniformly mixed with 350 kg of hydrofluoric acid within the pump. Primary mixing was then performed using a high-efficiency static mixer equipped with special structural elements such as SK, SX, and SY types to promote thorough dispersion. The material was then fed into a reactor (with a stirred tank) and stirred for 1 hour before being discharged. The material was subsequently filtered through a metal filter with a pore size of 150 micrometers, yielding a mother liquor. This mother liquor entered a buffer tank and was then pumped into a microchannel reactor at a flow rate maintained at 200 L / h. PF5 was then introduced into the first, fourth, and eighth plates of the microchannel reactor using a gas flow meter, with feed flow rates of 2.9 m³ / h for each plate. 3 / h, 8.75m 3 / h and 17.5m 3 The reaction time was 3.2 min, with a total residence time of 3.2 min. The first, second, and third plates were maintained at 50°C; the fourth, fifth, sixth, and seventh plates at 60°C; and the eighth, ninth, tenth, eleventh, and twelfth plates at 75°C. The reacted material was then transferred to an aging reactor with a back pressure of 1.5 MPa, where it remained for 100 min at a controlled temperature of 85°C. The reaction solution was then filtered through a precision filter to obtain a clear lithium hexafluorophosphate solution at 80°C.

[0177] The differences between Examples 1-21 and Comparative Examples 1-3 are shown in Table 1. The lithium hexafluorophosphate solutions of Examples 1-21 and Comparative Examples 1-3 were tested respectively. The acidity was detected by potentiometric titration, the content of non-lithium ion metal impurities was detected by inductively coupled plasma (ICP) test, and the content of lithium fluoride insoluble matter was detected by gravimetric method. The test results are shown in Table 2.

[0178] The gravimetric method is as follows: Take 100g of liquid sample in a glove box, then dilute the liquid sample with 1000g of ethyl methyl carbonate (EMC) as a solvent. Filter the solution using a 0.45μm polytetrafluoroethylene (PTFE) filter membrane (the weight of which is recorded as membrane empty). Add another 1000g of EMC as a detergent and pass it through the filter membrane. Then, vacuum dry the filter membrane at 50℃ and -0.05MPa for 2 hours. Weigh the filter membrane and record the weight as membrane dryness. The lithium fluoride insoluble content = (membrane dryness - membrane emptyness) / 100g of liquid sample.

[0179] The results of Examples 1-18, compared to Comparative Examples 1 and 2, show that the segmented introduction of PF5 and segmented temperature control in these examples resulted in lithium hexafluorophosphate solutions with lower contents of lithium fluoride insolubles, lower acidity, and lower contents of non-lithium ion metal impurities obtained from the reaction of PF5 and LiF. The results of Examples 1 and 19-21, compared to Comparative Example 3, show that using carbonate solvents as solvents, compared to using hydrofluoric acid, resulted in lower contents of lithium fluoride insolubles, lower acidity, and lower contents of non-lithium ion metal impurities in the prepared lithium hexafluorophosphate solutions. Specifically, the lithium hexafluorophosphate solutions prepared using the method of this application all had acidity below 50 ppm, lithium fluoride insolubles all below 10 ppm, and Na... + K + Fe + The content of all samples was less than 5 ppm.

[0180] Examples 1-5, 8-11, and 13-16, compared to Examples 6-7, 12, and 17-18, demonstrate that the ratio of the molar amounts of PF5 gas introduced in the three stages, the total residence time of the reaction, and the reaction temperature need to meet certain conditions in order to obtain a lithium hexafluorophosphate solution with better quality, suitable for preparing high-end lithium battery electrolytes, and meeting the high standards required by the market.

[0181] Table 1

[0182] Table 2

[0183] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0184] Although embodiments of this application have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting this application. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of this application.

Claims

1. A method of preparing a solution of lithium hexafluorophosphate, characterized in that, The method comprises: carrying out a first contact reaction of first phosphorus pentafluoride gas and a lithium fluoride solution to obtain a first reaction product; carrying out a second contact reaction of the first reaction product and second phosphorus pentafluoride gas to obtain a second reaction product; carrying out a third contact reaction of the second reaction product and third phosphorus pentafluoride gas to obtain the lithium hexafluorophosphate solution; wherein the first contact reaction, the second contact reaction and the third contact reaction are carried out in a micro-channel reactor; the lithium fluoride solution comprises lithium fluoride and a carbonate solvent.

2. The method of claim 1, wherein, The molar ratio of the first phosphorus pentafluoride gas, the second phosphorus pentafluoride gas and the third phosphorus pentafluoride gas is 1:(2-4):(5-8). The total time of the first contact reaction time, the second contact reaction time and the third contact reaction time is not less than 0.2 min.

3. The method of claim 2, wherein, The total time of the first contact reaction time, the second contact reaction time and the third contact reaction time is 0.2 min-7 min.

4. The method of claim 1, wherein, The temperature of the first contact reaction is 20-70 ℃. The temperature of the second contact reaction is 30-80 ℃. The temperature of the third contact reaction is 40-90 ℃.

5. The method of claim 1, wherein, The content of the lithium fluoride in the lithium fluoride solution is less than 20%. The diameter of the lithium fluoride is less than 200 μm. The carbonate solvent comprises at least one of methyl ethyl carbonate, dimethyl carbonate, diethyl carbonate, ethyl acetate, butyl acetate, ethyl propionate, ethyl butyrate and ethyl benzoate.

6. The method of claim 5, wherein, The lithium fluoride solution is obtained by: mixing the lithium fluoride to be mixed with the carbonate solvent to obtain a mixing product; carrying out a first filtration treatment on the mixing product to obtain the lithium fluoride solution.

7. The method of claim 6, wherein, The Dv50 of the lithium fluoride to be mixed is less than 200 μm. The first filtration treatment is carried out in a metal filter.

8. The method of claim 1, wherein, After the third contact reaction, further comprising: carrying out an aging treatment, a second filtration treatment and a purification treatment on the third contact reaction product to obtain the lithium hexafluorophosphate solution.

9. The method of claim 8, wherein, The aging treatment is carried out in an aging kettle. The second filtration treatment is carried out in a precision filter. The purification treatment is carried out in an ion exchange resin.

10. An apparatus for preparing a solution of lithium hexafluorophosphate, characterized in that, The method comprises: a reactor having a plurality of reaction plates connected in sequence; each of the plurality of reaction plates comprises at least one inlet and at least one outlet.

11. The apparatus of claim 10, wherein, Further comprising: a mixing unit for mixing lithium fluoride with a carbonate solvent, the mixing unit being in communication with the inlet of one of the plurality of reaction plates.

12. The apparatus of claim 11, wherein, Further comprising: a first filtration unit arranged between the mixing unit and the reactor, the mixing unit being in communication with the first filtration unit, and the first filtration unit being in communication with the inlet of one of the plurality of reaction plates.

13. The apparatus of claim 12, wherein, The plurality of reaction plates are arranged in sequence in the same direction, and the mixing unit or the first filtration unit is in communication with the inlet of the reaction plate located at the end.

14. The apparatus of claim 13, wherein, Further comprising: A segmented temperature control unit for controlling the temperature of the reaction plate.

15. The apparatus of claim 14, wherein, Further comprising: An aging unit in communication with the outlet of the reaction plate at the other end.

16. The apparatus of claim 15, wherein, Further comprising: A second filtration unit in communication with the aging unit.

17. The apparatus of claim 16, wherein, Further comprising: A purification unit in communication with the second filtration unit.

18. A solution of lithium hexafluorophosphate, characterized in that, Obtained by the method of any one of claims 1-9 or the apparatus of any one of claims 10-17.

19. The solution of lithium hexafluorophosphate according to claim 18, characterized in that, The content of insoluble substances in the solution is not higher than 10 ppm; And / or, the acidity of the solution is lower than 100 ppm; And / or, the content of non-lithium ion metal impurities in the solution is not higher than 5 ppm; And / or, the insoluble substance in the solution is lithium fluoride.

20. Lithium hexafluorophosphate characterized in that, Is obtained by crystallizing the lithium hexafluorophosphate solution of claim 18 or 19.

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