Preparation method of sodium difluoro (oxalato) borate

Abstract

The invention provides a preparation method of sodium difluoro (oxalato) borate. The method at least comprises a reaction step of reacting sodium oxalate with boron trifluoride or a boron trifluoride complex to obtain the sodium difluoro (oxalato) borate. In the preparation method provided by the invention, the production process is simple, the utilization rate of production raw materials is high, large-scale mass production is facilitated, and the production cost is reduced.

Description

Preparation method of sodium difluorooxalatoborate Technical Field

[0001] The present application relates to the technical field of chemical synthesis, and in particular to a method for preparing sodium difluorooxalatoborate. Background Art

[0002] Sodium-ion batteries have advantages such as energy storage principles and process technologies similar to those of lithium-ion batteries. At the same time, sodium resources are abundant, so sodium-ion batteries have very broad application prospects. Electrolyte salts, as an important component of batteries, are one of the research focuses of sodium-ion batteries. Sodium difluorooxalatoborate (NaODFB) is a new type of sodium-ion battery electrolyte salt with the characteristics of compatibility with a variety of solvents and good cycle stability of the prepared electrolyte. However, in the synthesis of sodium difluorooxalatoborate, when lithium difluorooxalatoborate is used as the reaction raw material, there is a problem of high raw material cost, which is not conducive to the industrial production of sodium batteries. Therefore, it is still necessary to develop a new preparation method of sodium difluorooxalatoborate.

[0003] Summary of the Invention

[0004] The present application is made in view of the above-mentioned problems, and its purpose is to provide a method for preparing sodium difluorooxalatoborate, which comprises at least step (1): reacting sodium oxalate with boron trifluoride or a boron trifluoride complex to obtain sodium difluorooxalatoborate. The method has a simple preparation process and can synthesize sodium difluorooxalatoborate in one step.

[0005] In some embodiments, step (1) comprises reacting sodium oxalate with boron trifluoride or a boron trifluoride complex in a solvent, separating a reaction solution containing sodium difluorooxalatoborate from the product; and recrystallizing the reaction solution to obtain sodium difluorooxalatoborate. The sodium difluorooxalatoborate prepared by the method has good purity, is industrially feasible, and is easily scalable.

[0006] In some embodiments, the insoluble matter in the reaction solution is removed by a method selected from centrifugation and filtration to obtain a reaction solution containing sodium difluorooxalatoborate.

[0007] In some embodiments, the boron trifluoride complex comprises boron trifluoride etherate or boron trifluoride acetonitrile.

[0008] In some embodiments, the molar ratio of sodium oxalate to boron trifluoride or boron trifluoride in a boron trifluoride complex in step (1) is 1:1-1:2.5, and can be optionally 1:1.5-1:2.5. A suitable molar ratio of the reaction raw materials helps to increase the yield of the synthetic product and reduce the synthesis cost of sodium difluorooxalatoborate.

[0009] In step (1) of the present application, in some embodiments, the reaction temperature is -20° C. to 100° C., optionally 0° C. to 45° C. The temperature is conducive to obtaining a suitable reaction rate and making the chemical reaction process controllable.

[0010] In some embodiments, the reaction time of step (1) is 0.5 h to 10 h, optionally 0.5 h to 5 h, and further optionally 0.5 h to 2 h. The reaction time is conducive to the full progress of the reaction and the improvement of the yield of the synthetic product.

[0011] In some embodiments, the reaction solvent of step (1) comprises a polar solvent, and optionally, the polar solvent comprises one or more of acetonitrile, methanol, diethyl ether, N,N-dimethylformamide, dimethyl sulfoxide, tetrahydrofuran, ethylene glycol dimethyl ether, and ethylene glycol diethyl ether; in some embodiments, the polar solvent may be one or more of ethylene glycol dimethyl ether and ethylene glycol diethyl ether. The reaction solvent is stable and has excellent solubility.

[0012] In some embodiments, the recrystallization is carried out in dichloromethane.

[0013] The preparation method provided in this application comprises at least steps (1) and (2):

[0014] Step (1): reacting sodium oxalate with boron trifluoride or a boron trifluoride complex to obtain sodium difluorooxalatoborate and sodium tetrafluoroborate;

[0015] Step (2): decomposing the sodium tetrafluoroborate obtained in step (1) into boron trifluoride or a boron trifluoride complex and then adding the resultant to step (1) as a raw material.

[0016] The preparation method can decompose the reaction by-products into raw materials and then continue to feed them into the synthesis reaction, thereby reducing the raw material consumption caused by side reactions and improving the utilization rate of the reaction raw materials.

[0017] In some embodiments, the sodium difluorooxalatoborate and sodium tetrafluoroborate obtained in step (1) are separated. In some embodiments, the separated sodium tetrafluoroborate is subjected to thermal decomposition to obtain boron trifluoride or a boron trifluoride complex. Alternatively, the separated sodium tetrafluoroborate is thermally decomposed at 600° C. to 800° C. Through the thermal decomposition treatment, the fluorine atoms in the byproduct sodium tetrafluoroborate can be put back into the reaction and utilized, which helps to improve the yield and utilization rate of the fluorine atoms.

[0018] In some embodiments, boron trifluoride produced by thermal decomposition of sodium tetrafluoroborate is added to step (1). In some embodiments, the boron trifluoride produced by thermal decomposition of sodium tetrafluoroborate is absorbed by diethyl ether or acetonitrile and then fed back into the reaction as a reaction raw material. By thermally decomposing sodium tetrafluoroborate, the utilization rate of boron trifluoride or boron trifluoride complex is increased by recycling the thermal decomposition product.

[0019] The second aspect of the present application provides a method for preparing sodium difluorooxalatoborate, comprising the following steps:

[0020] (1) reacting sodium oxalate with boron trifluoride or a boron trifluoride complex in a solvent to obtain a reaction product comprising a reaction solution containing sodium difluorooxalatoborate solute and sodium tetrafluoroborate solid;

[0021] (2) separating the reaction product to obtain a solution containing sodium difluorooxalatoborate and a sodium tetrafluoroborate solid;

[0022] (3) recrystallizing the solution containing sodium difluorooxalatoborate to obtain sodium difluorooxalatoborate;

[0023] (4) Thermally decomposing sodium tetrafluoroborate solid to generate boron trifluoride or a boron trifluoride complex, and recycling the generated boron trifluoride or boron trifluoride complex into step (1) as a raw material.

[0024] The preparation method of sodium difluorooxalatoborate provided in the present application has a simple process and a high utilization rate of reaction raw materials, which helps to reduce the synthesis cost of sodium difluorooxalatoborate and reduce environmental hazards. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] FIG1 shows the ion chromatogram of sodium difluorooxalatoborate prepared in Example 1. DETAILED DESCRIPTION

[0026] Below, the embodiments of the binder, preparation method, electrode, battery, and electrical device of the present application are described in detail with appropriate reference to the accompanying drawings. However, there may be cases where unnecessary detailed descriptions are omitted. For example, there may be cases where detailed descriptions of well-known matters and repeated descriptions of actually the same structures are omitted. This is to avoid the following description from becoming unnecessarily lengthy and to facilitate understanding by those skilled in the art. In addition, the drawings and the following description are provided to enable those skilled in the art to fully understand the present application and are not intended to limit the subject matter described in the claims.

[0027] " range " disclosed in the present application is limited in the form of lower limit and upper limit, and given range is limited by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundary of special range. The scope limited in this way can be to include end value or not include end value, and can be arbitrarily combined, that is, any lower limit can form a range with any upper limit combination. For example, if the scope of 60-120 and 80-110 is listed for specific parameters, it is understood that the scope of 60-110 and 80-120 is also expected. In addition, if the minimum range value 1 and 2 are listed, and if the maximum range value 3,4 and 5 are listed, then the following range can all be expected: 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5. In this application, unless otherwise specified, the numerical range " ab " represents the abbreviation of any real number combination between a and b, wherein a and b are all real numbers. For example, a numerical range of "0-5" indicates that all real numbers between "0-5" are listed herein, and "0-5" is simply an abbreviation for these numerical combinations. Furthermore, when a parameter is expressed as an integer ≥ 2, this is equivalent to disclosing that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0028] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0029] Unless otherwise specified, all technical features and optional technical features of this application can be combined with each other to form a new technical solution.

[0030] Unless otherwise specified, all steps of the present application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially. For example, the method may further include step (c), indicating that step (c) may be added to the method in any order, for example, the method may include steps (a), (b) and (c), or may include steps (a), (c) and (b), or may include steps (c), (a) and (b), etc.

[0031] Unless otherwise specified, the terms "include" and "comprising" used in this application may be open-ended or closed-ended. For example, "include" and "comprising" may mean that other components not listed may also be included or that only the listed components are included.

[0032] Unless otherwise specified, the term "or" is used in this application to be inclusive. For example, the phrase "A or B" means "A, B, or both A and B." More specifically, the condition "A or B" is satisfied if any of the following conditions are met: A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or both A and B are true (or exist).

[0033] Sodium difluorooxalatoborate has good application prospects in sodium ion batteries. The electrolyte prepared using it has the advantages of good compatibility and enhanced electrochemical oxidation stability. At present, sodium difluorooxalatoborate is often obtained by chemical synthesis. In general, the yield of directly preparing sodium difluorooxalatoborate using lithium difluorooxalatoborate as a reaction raw material is not high. In order to improve the yield, it is necessary to select special reaction raw materials (for example, sodium bis(trifluoromethylsulfonyl imide)) for reaction. Due to the high cost of the reaction raw materials, the cost of sodium batteries is increased.

[0034] Based on this, in the first aspect, the present application proposes a method for preparing sodium difluorooxalatoborate, which at least comprises step (1): sodium oxalate reacts with boron trifluoride or a boron trifluoride complex to obtain sodium difluorooxalatoborate.

[0035] In some embodiments, the boron trifluoride complex comprises boron trifluoride ethyl etherate, boron trifluoride acetonitrile, or a combination thereof. Alternatively, the boron trifluoride complex is boron trifluoride ethyl etherate; alternatively, the boron trifluoride complex is boron trifluoride acetonitrile.

[0036] The preparation method provided in the present application can produce sodium difluorooxalatoborate in a one-step process, and the reaction raw materials are low-cost and easily available, which is conducive to controlling or reducing the preparation cost of sodium difluorooxalatoborate.

[0037] In some embodiments, in step (1), the molar ratio of the sodium oxalate to the boron trifluoride or the boron trifluoride in the boron trifluoride complex is 1:1-1:2.5, optionally 1:1.5-1:2.5, 1:2-1:2.5, 1:2.2-1:2.5, or 1:1.5-1:2.2. The molar ratio of the sodium oxalate to the boron trifluoride or the boron trifluoride in the boron trifluoride complex can also be 1:1.1, 1:1.3, 1:1.7, 1:1.8, 1:1.9, 1:2.1, 1:2.3, 1:2.4, or a range between any two ratios.

[0038] Based on the molar amount of boron trifluoride, when the molar ratio of sodium oxalate to boron trifluoride or the boron trifluoride complex is within the above range, sodium oxalate and boron trifluoride or the boron trifluoride complex can fully react, which helps to improve the reaction yield / yield.

[0039] In step (1), sodium oxalate reacts with boron trifluoride or a boron trifluoride complex in a solvent (reaction solvent). In some embodiments, the solvent comprises a polar solvent, which comprises one or more of acetonitrile, methanol, diethyl ether, N,N-dimethylformamide, dimethyl sulfoxide, tetrahydrofuran, ethylene glycol dimethyl ether, and ethylene glycol diethyl ether.

[0040] In some embodiments, the solvent comprises one or more of ethylene glycol dimethyl ether, ethylene glycol diethyl ether, acetonitrile, and dimethyl sulfoxide.

[0041] Alternatively, the solvent in step (1) is ethylene glycol dimethyl ether and / or ethylene glycol diethyl ether. In some embodiments, the solvent in step (1) is ethylene glycol dimethyl ether, or ethylene glycol diethyl ether. In some embodiments, the solvent in step (1) is acetonitrile or dimethyl sulfoxide.

[0042] Without being bound by any theory, the solvent (reaction solvent) can adjust the polarity of the reaction raw materials, promote the reaction toward product formation, and enable the reaction raw materials to generate reaction products under relatively mild reaction conditions.

[0043] In some embodiments, the reaction temperature of step (1) is -20°C to 100°C. Alternatively, the reaction temperature of step (1) is 0°C to 100°C, 0°C to 80°C, 0°C to 45°C, 0°C to 25°C, 5°C to 25°C, 5°C to 45°C, 5°C to 80°C, 25°C to 45°C, or 25°C to 80°C. The reaction temperature of step (1) can also be 10°C, 15°C, 20°C, 30°C, 35°C, 40°C, 50°C, 55°C, 60°C, 65°C, 70°C, 75°C, 85°C, 90°C, or a range between any two temperatures.

[0044] The relatively mild reaction conditions facilitate the expansion of the preparation scale of sodium difluorooxalatoborate. For example, the scale of industrial mass production can produce at least 500 g, 1 kg, 5 kg, 10 kg, 50 kg, or 100 kg of sodium difluorooxalatoborate, depending on the quality requirements of the sodium difluorooxalatoborate.

[0045] In some embodiments, the reaction time of step (1) is 0.5h-10h. Alternatively, the reaction time of step (1) is 0.5h-5h, 0.5h-3h, 0.5h-2h, 1h-10h, 1h-5h, 1h-3h, 2h-10h, 2h-5h, 2h-3h, 3h-10h, or 3h-5h. The reaction time of step (1) can also be 1.5h, 2.5h, 3.5h, 4h, 4.5h, 5.5h, 6h, 7h, 8h, 9h, or a range between any two reaction times.

[0046] The appropriate reaction time helps to increase the synthesis yield of sodium difluorooxalatoborate, and has improved production efficiency and reduced energy consumption and carbon emissions.

[0047] In the preparation method provided herein, the reaction solution containing sodium difluorooxalatoborate is collected after the reaction is completed. In some embodiments, the reaction solution containing sodium difluorooxalatoborate is removed by removing insoluble matter. Alternatively, the reaction solution containing sodium difluorooxalatoborate is separated from the product by filtration, precipitation, or centrifugation.

[0048] In some embodiments, the reaction solution is recrystallized to obtain sodium difluorooxalatoborate. Through recrystallization, the purity of sodium difluorooxalatoborate is significantly improved, and the content of impurities (e.g., byproduct sodium tetrafluoroborate) in sodium difluorooxalatoborate is significantly reduced.

[0049] In some embodiments, the reaction solution is concentrated, for example, by using vacuum rotary evaporation to concentrate the reaction solution.

[0050] In some embodiments, the recrystallization is carried out in dichloromethane, which is volatile and the recrystallized product is easy to dry.

[0051] During the reaction of sodium oxalate with boron trifluoride or a boron trifluoride complex, sodium tetrafluoroborate is generated as a byproduct, which consumes the fluorine atoms in boron trifluoride or the boron trifluoride complex, reduces the utilization rate of fluorine atoms, and is not conducive to controlling the preparation cost of sodium difluorooxalatoborate.

[0052] The second aspect of the present application provides a method for preparing sodium difluorooxalatoborate, which comprises at least the following steps (1) and (2):

[0053] Step (1): reacting sodium oxalate with boron trifluoride or a boron trifluoride complex to obtain sodium difluorooxalatoborate and sodium tetrafluoroborate;

[0054] Step (2): decomposing the sodium tetrafluoroborate obtained in step (1) into boron trifluoride or a boron trifluoride complex and then adding the resultant to step (1) as a raw material.

[0055] In the preparation method provided herein, the byproduct sodium tetrafluoroborate is decomposed and then reintroduced into the reaction as a reaction raw material, thereby increasing the utilization rate of the fluorine atoms in the reaction raw material boron trifluoride or boron trifluoride complex, thereby helping to control the production cost of sodium difluorooxalatoborate. Furthermore, the preparation method reduces the emission of fluorine atoms, thereby reducing environmental hazards and promoting environmental protection.

[0056] In step (1), the boron trifluoride complex comprises boron trifluoride ethyl ether, boron trifluoride acetonitrile, or a combination thereof. Alternatively, the boron trifluoride complex is boron trifluoride ethyl ether or boron trifluoride acetonitrile.

[0057] In the method, the reaction raw materials are cheap and easily available, which helps to further control the preparation cost of sodium difluorooxalatoborate and improve the feasibility of large-scale mass production.

[0058] In some embodiments, the molar ratio of the sodium oxalate to the boron trifluoride or the boron trifluoride in the boron trifluoride complex is 1:1-1:2.5, optionally 1:1.5-1:2.5, 1:2-1:2.5, 1:2.2-1:2.5, or 1:1.5-1:2.2.

[0059] The molar ratio of the sodium oxalate to the boron trifluoride or the boron trifluoride in the boron trifluoride complex may also be 1:1.1, 1:1.3, 1:1.7, 1:1.8, 1:1.9, 1:2.1, 1:2.3, 1:2.4, or a range between any two ratios.

[0060] When the molar ratio of the sodium oxalate to the boron trifluoride or the boron trifluoride in the boron trifluoride complex is within the above range, the sodium oxalate and the boron trifluoride or the boron trifluoride complex can fully react, thereby improving the reaction yield / yield of sodium difluorooxalatoborate.

[0061] In some embodiments, the sodium oxalate reacts with the boron trifluoride or boron trifluoride complex in a solvent (reaction solvent). In some embodiments, the solvent comprises a polar solvent, which comprises one or more of acetonitrile, methanol, ether, N,N-dimethylformamide, dimethyl sulfoxide, tetrahydrofuran, ethylene glycol dimethyl ether, and ethylene glycol diethyl ether.

[0062] In some embodiments, the solvent comprises one or more of ethylene glycol dimethyl ether, ethylene glycol diethyl ether, acetonitrile, and dimethyl sulfoxide.

[0063] Alternatively, the solvent is ethylene glycol dimethyl ether and / or ethylene glycol diethyl ether. In some embodiments, the solvent is ethylene glycol dimethyl ether, or ethylene glycol diethyl ether. In some embodiments, the solvent is acetonitrile or dimethyl sulfoxide.

[0064] Without being bound by any theory, the solvent (reaction solvent) can adjust the polarity of the reaction raw materials, promote the reaction toward product formation, and enable the reaction raw materials to generate reaction products under relatively mild reaction conditions.

[0065] In some embodiments, the reaction temperature of step (1) is -20°C-100°C. Alternatively, the reaction temperature of step (1) is 0°C-100°C, 0°C-80°C, 0°C-45°C, 0°C-25°C, 5°C-25°C, 5°C-45°C, 5°C-80°C, 25°C-45°C, or 25°C-80°C.

[0066] The reaction temperature of step (1) can also be 10°C, 15°C, 20°C, 30°C, 35°C, 40°C, 50°C, 55°C, 60°C, 65°C, 70°C, 75°C, 85°C, 90°C, or a range between any two temperatures.

[0067] The relatively mild reaction conditions facilitate the scale-up of the preparation of sodium difluorooxalatoborate.

[0068] In some embodiments, the reaction time of step (1) is 0.5h-10h. Alternatively, the reaction time of step (1) is 0.5h-5h, 0.5h-3h, 0.5h-2h, 1h-10h, 1h-5h, 1h-3h, 2h-10h, 2h-5h, 2h-3h, 3h-10h, or 3h-5h.

[0069] The reaction time of step (1) may also be 1.5 h, 2.5 h, 3.5 h, 4 h, 4.5 h, 5.5 h, 6 h, 7 h, 8 h, 9 h, or a range between any two reaction times.

[0070] The appropriate reaction time helps to increase the synthesis yield of sodium difluorooxalatoborate, and has improved production efficiency and reduced energy consumption and carbon emissions.

[0071] In the preparation method provided herein, the sodium difluorooxalatoborate and sodium tetrafluoroborate obtained in step (1) are separated. Alternatively, the sodium tetrafluoroborate solid and the reaction solution containing sodium difluorooxalatoborate are separated from the product by filtration, precipitation or centrifugation.

[0072] In some embodiments, the reaction solution is recrystallized to obtain sodium difluorooxalatoborate. Through recrystallization, the purity of sodium difluorooxalatoborate is significantly improved, and the content of impurities (e.g., byproduct sodium tetrafluoroborate) in sodium difluorooxalatoborate is significantly reduced.

[0073] In some embodiments, the reaction solution is concentrated, for example, by using vacuum rotary evaporation to concentrate the reaction solution.

[0074] In some embodiments, the recrystallization is carried out in dichloromethane, which is volatile and the recrystallized product is easy to dry.

[0075] In some embodiments, in step (2), the separated sodium tetrafluoroborate is subjected to thermal decomposition to obtain boron trifluoride or a boron trifluoride complex. After the thermal decomposition treatment, the byproduct sodium tetrafluoroborate decomposes into boron trifluoride gas and sodium fluoride solid, and the boron trifluoride gas can be easily separated and collected.

[0076] In some embodiments, diethyl ether or acetonitrile is used to absorb boron trifluoride produced by thermal decomposition of sodium tetrafluoroborate to obtain boron trifluoride diethyl ether or boron trifluoride acetonitrile complex.

[0077] In some embodiments, boron trifluoride produced by thermal decomposition of sodium tetrafluoroborate is added as a reaction raw material to step (1). In some embodiments, boron trifluoride produced by thermal decomposition of sodium tetrafluoroborate is absorbed by diethyl ether or acetonitrile, and the absorbed product is added as a reaction raw material to step (1).

[0078] Boron trifluoride or a boron trifluoride complex produced by the decomposition of sodium tetrafluoroborate can be reused in the preparation of sodium difluorooxalatoborate, reducing the consumption of boron trifluoride or a boron trifluoride complex and fluorine atoms due to side reactions, thereby improving the utilization rate of boron trifluoride or a boron trifluoride complex and the fluorine atoms therein. Furthermore, the sodium fluoride product of thermal decomposition is a solid, making it easy to collect and presenting relatively minimal environmental hazards, thus reducing environmental hazards during the preparation of sodium difluorooxalatoborate.

[0079] In some embodiments, the separated sodium tetrafluoroborate is thermally decomposed at 600° C. to 1100° C., alternatively, 600° C. to 800° C. It will be appreciated that the thermal decomposition can be carried out at any temperature or temperature range within the range of 600° C. to 1100° C., for example, 600° C. to 1000° C., 600° C. to 800° C., 600° C. to 700° C., 700° C. to 800° C., 650° C. to 800° C., 600° C. to 750° C., 650° C. to 700° C., 625° C., 675° C., or 725° C.

[0080] Sodium tetrafluoroborate can be fully thermally decomposed within the temperature range, which helps to improve the yield of boron trifluoride in the thermal decomposition, thereby further improving the utilization rate of the reaction raw material boron trifluoride or boron trifluoride complex and the fluorine atoms therein, and better controlling energy consumption and carbon emissions.

[0081] In some embodiments, the preparation method of sodium difluorooxalatoborate provided herein comprises the following steps:

[0082] (1) reacting sodium oxalate with boron trifluoride or a boron trifluoride complex in a solvent to obtain a reaction product comprising a reaction solution containing sodium difluorooxalatoborate solute and sodium tetrafluoroborate solid;

[0083] (2) separating the reaction product to obtain a solution containing sodium difluorooxalatoborate and a sodium tetrafluoroborate solid;

[0084] (3) recrystallizing the solution containing sodium difluorooxalatoborate to obtain sodium difluorooxalatoborate;

[0085] (4) Thermally decomposing sodium tetrafluoroborate solid to generate boron trifluoride or a boron trifluoride complex, and recycling the generated boron trifluoride or boron trifluoride complex into step (1) as a raw material.

[0086] In the preparation method, the reaction raw materials sodium oxalate and boron trifluoride or a boron trifluoride complex are low in cost and widely available; the synthesis process is simple and feasible, which is conducive to the realization of industrial mass production; and by decomposing and recycling the reaction by-products, the utilization rate of the reaction raw materials is improved and the environmental harm is reduced.

[0087] The sodium difluorooxalatoborate prepared according to the method provided in the present application can be used as an electrolyte salt to prepare secondary batteries, optionally, to prepare sodium ion secondary batteries.

[0088] The present application provides sodium difluorooxalatoborate, which is prepared by the preparation method provided in the present application.

[0089] The present application provides a use of sodium difluorooxalatoborate in a secondary battery (eg, a sodium ion battery), wherein the sodium difluorooxalatoborate is prepared by the preparation method provided in the present application.

[0090] The above embodiments can be combined with each other as needed, as long as they do not contradict each other.

[0091] Example

[0092] Below, the embodiment of the present application is described. The embodiment described below is exemplary and is only used to explain the present application, and is not to be construed as limiting the present application. Where specific techniques or conditions are not specified in the embodiments, the techniques or conditions described in the literature in this area or the product specifications are used. Reagents or instruments used that do not specify the manufacturer are conventional products that can be obtained commercially.

[0093] 1. Preparation method

[0094] Example 1

[0095] 134g of dry sodium oxalate (purity 98%) and 600ml of anhydrous glycol dimethyl ether are put into a 1000ml three-necked flask, 135g of boron trifluoride gas is introduced, and the reaction is stirred at 25 ℃ for 5h. The reacted solution is filtered to obtain 90g of sodium tetrafluoroborate and the glycol dimethyl ether solution containing difluoro sodium oxalate borate. The glycol dimethyl ether solution containing difluoro sodium oxalate borate is rotary evaporated to concentrate the glycol dimethyl ether concentrated solution of difluoro sodium oxalate borate. Dichloromethane is added to the glycol dimethyl ether concentrated solution of difluoro sodium oxalate borate and recrystallized to obtain 155.6g of difluoro sodium oxalate borate. According to the consumption of sodium oxalate and the ion chromatography purity calculation of difluoro sodium oxalate borate, the actual yield of difluoro sodium oxalate borate is 95.99%.

[0096] 90g of sodium tetrafluoroborate was placed in a tube furnace and cracked at 600°C for 8h. Nitrogen was used to blow out boron trifluoride gas, which was then absorbed by ether to obtain 37g of sodium fluoride and 52g of boron trifluoride gas. The recovery rate of boron trifluoride was 93.55%, and the utilization rate of fluorine atoms was 59.86%.

[0097] The prepared sodium difluorooxalatoborate was detected by ion chromatography to obtain chromatogram 1 and the following test results:

[0098] Among them, the substance with a retention time of 6.6 minutes is fluoride ion, and the substance with a retention time of 26.49 minutes is oxalate ion. The sum of the area ratios of fluoride ion and oxalate ion is the detection purity of sodium difluorooxalatoborate. The results show that the prepared sodium difluorooxalatoborate has a good purity of 96.73%.

[0099] In Examples 2 to 24, the reaction reagents and preparation parameters were adjusted. For details, see Table 1 below.

[0100] Table 1

[0101] Comparative Example 1

[0102] Dissolve 1 mol of lithium difluorooxalatoborate in 600 g of dimethyl carbonate to prepare a solution. Dissolve 1 mol of sodium bis(trifluoromethylsulfonylimide) in 300 g of dimethyl carbonate to prepare a solution. Mix and stir the two salt solutions, then heat to 50°C and allow to react for 3 hours. Filter the reaction solution to obtain a crude sodium difluorooxalatoborate and a solution of lithium bis(trifluoromethylsulfonylimide) in dimethyl carbonate. Wash the crude sodium difluorooxalatoborate with 3 times the mass of dimethyl carbonate, filter, and vacuum dry at 130°C for 12 hours to obtain pure sodium difluorooxalatoborate.

[0103] 2. Test Method

[0104] 1. Calculation method of product yield and fluorine atom utilization rate

[0105] The actual yield of sodium difluorooxalatoborate is calculated according to the following formula:

[0106] The yield of boron trifluoride is calculated according to the following formula:

[0107] Fluorine atom utilization rate = theoretical utilization rate 66.6% × actual yield of sodium difluorooxalatoborate × boron trifluoride yield

[0108] 2. Ion chromatography detection method of sodium difluorooxalatoborate

[0109] Device Model:

[0110] Host: 930 Compact IC Flex, Brand: Metrohm

[0111] Autosampler: 919 IC Autosampler plus, brand: Metrohm

[0112] Eluent: 3.2mmol / L Na2CO3+1.0mmol / L NaHCO3 (reagent purity: AR grade or above)

[0113] Regeneration solution: 0.5% H2SO4 + 0.1mol / L H2C2O4 + 3% acetone (reagent purity: AR grade or above)

[0114] Chromatographic column model: Metrosep A Supp5-250 / 4.0

[0115] Flow rate: 0.7 ml / min, conductivity detector

[0116] The mass and actual yield of sodium difluorooxalatoborate obtained in Examples 1 to 24, the mass of sodium tetrafluoroborate, the mass and yield of recovered boron trifluoride, and the utilization rate of fluorine atoms are shown in Table 2.

[0117] Table 2

[0118] As can be seen from Table 2, Examples 1-7 show that the preparation method provided in the present application can be carried out smoothly in the reaction temperature range of -20°C to 100°C, and the actual yield of sodium difluorooxalatoborate is at least 70% or more; Example 1 and Examples 3-6 show that when the reaction temperature is in the range of 0°C to 100°C, an actual yield of sodium difluorooxalatoborate of at least 90% can be obtained; the actual yield of the product in Example 1, Example 3, Example 4 and Example 5 is at least 94%, indicating that a reaction temperature in the range of 0°C to 45°C is conducive to obtaining a higher product yield of sodium difluorooxalatoborate.

[0119] Examples 1 and 8-12 demonstrate that the preparation method provided herein achieves an actual yield of sodium difluorooxalatoborate of no less than 93% within a reaction time range of 0.5 to 10 hours. This range is advantageous for saving reaction time and achieving suitable production efficiency. A reaction time range of 0.5 to 2 hours is advantageous for achieving a balanced balance between production efficiency and product yield.

[0120] Examples 13-15 show that the preparation method provided by this application can also be carried out in a reaction solvent of acetonitrile, ethylene glycol diethyl ether, or dimethyl sulfoxide, wherein Example 14 has the highest product yield. In conjunction with Examples 1-12 and Examples 16-24, using ethylene glycol diethyl ether or ethylene glycol dimethyl ether as the reaction solvent facilitates the reaction and can improve the product yield.

[0121] In Example 16 and Example 17, boron trifluoride etherate and boron trifluoride acetonitrile were used as reaction raw materials to prepare sodium difluorooxalatoborate, and both achieved a product yield of at least 92%.

[0122] In Examples 18-21, the molar ratio of sodium oxalate to boron trifluoride was adjusted. As the amount of boron trifluoride increased, the yield of sodium difluorooxalatoborate significantly increased and remained essentially stable. When the molar ratio of sodium oxalate to boron trifluoride was between 1:1.5 and 1:2.5, the actual yield of sodium difluorooxalatoborate reached over 95%.

[0123] Examples 22 and 23, respectively, investigated the yield of boron trifluoride and the utilization rate of fluorine atoms during the thermal decomposition of the byproduct sodium tetrafluoroborate at reaction temperatures of 700°C and 800°C. Combined with Example 1, it can be seen that within the reaction temperature range of 600°C to 800°C, by recycling the thermal decomposition products of the byproduct sodium tetrafluoroborate, a boron trifluoride recovery rate of over 92% and a fluorine atom utilization rate of not less than 59% were achieved. Compared to Example 24, in which the byproduct sodium tetrafluoroborate was not recycled, recycling the byproduct sodium tetrafluoroborate after thermal decomposition and reuse in the reaction significantly improved the utilization rate of fluorine atoms.

[0124] Examples 1-24 of the present application all adopt a completely different synthesis route from Comparative Example 1, and the reaction by-products are recycled and utilized, thereby improving the utilization rate of fluorine atoms and reducing the raw material cost and environmental pollution of sodium difluorooxalatoborate.

[0125] It should be noted that the present application is not limited to the above-mentioned embodiments. The above-mentioned embodiments are merely examples, and within the scope of the technical solution of the present application, embodiments having substantially the same structure as the technical concept and exerting the same effects are all included in the technical scope of the present application. In addition, within the scope of the subject matter of the present application, various modifications that can be conceived by those skilled in the art to the embodiments, and other methods constructed by combining some of the constituent elements in the embodiments are also included in the scope of the present application.

Claims

1. A method for preparing sodium difluorooxalatoborate, characterized in that: The method at least comprises the step (1): reacting sodium oxalate with boron trifluoride or a boron trifluoride complex to obtain sodium difluorooxalatoborate.

2. The preparation method according to claim 1, characterized in that: The step (1) comprises reacting sodium oxalate with boron trifluoride or a boron trifluoride complex in a solvent, separating a reaction solution containing sodium difluorooxalatoborate from the product; and obtaining sodium difluorooxalatoborate by recrystallization of the reaction solution.

3. The preparation method according to claim 2, characterized in that: The reaction solution containing sodium difluorooxalatoborate was separated from the product by filtration.

4. The preparation method according to any one of claims 1 to 3, characterized in that The boron trifluoride complex in step (1) includes boron trifluoride ether or boron trifluoride acetonitrile.

5. The preparation method according to any one of claims 1 to 4, characterized in that: In the step (1), the molar ratio of the sodium oxalate to the boron trifluoride or the boron trifluoride in the boron trifluoride complex is 1:1-1:2.5, and can be optionally 1:1.5-1:2.

5.

6. The preparation method according to any one of claims 1 to 5, characterized in that The reaction temperature of step (1) is -20°C-100°C, and can be optionally 0°C-45°C.

7. The preparation method according to any one of claims 1 to 6, characterized in that The reaction time of step (1) is 0.5h-10h, optionally 0.5h-5h, further optionally 0.5h-2h.

8. The preparation method according to any one of claims 2 to 7, characterized in that: The solvent of step (1) comprises a polar solvent, and the polar solvent comprises one or more of acetonitrile, methanol, diethyl ether, N,N-dimethylformamide, dimethyl sulfoxide, tetrahydrofuran, ethylene glycol dimethyl ether, and ethylene glycol diethyl ether. Optionally, the polar solvent is selected from one or more of ethylene glycol dimethyl ether and ethylene glycol diethyl ether.

9. The preparation method according to any one of claims 2 to 8, characterized in that: The recrystallization was carried out in dichloromethane.

10. The preparation method according to any one of claims 1 to 9, characterized in that: It at least includes the following steps (1) and (2): Step (1): reacting sodium oxalate with boron trifluoride or a boron trifluoride complex to obtain sodium difluorooxalatoborate and sodium tetrafluoroborate; Step (2): The sodium tetrafluoroborate obtained in step (1) is decomposed into boron trifluoride or a boron trifluoride complex and then added to step (1) as a raw material.

11. The preparation method according to claim 10, characterized in that: The sodium difluorooxalatoborate and sodium tetrafluoroborate obtained in step (1) are separated, and the separated sodium tetrafluoroborate is thermally decomposed to obtain boron trifluoride or a boron trifluoride complex.

12. The preparation method according to claim 11, characterized in that: The separated sodium tetrafluoroborate is thermally decomposed at 600°C-1100°C, optionally 600°C-800°C.

13. The preparation method according to claim 11 or 12, characterized in that: Use ether or acetonitrile to absorb the boron trifluoride produced by the thermal decomposition of sodium tetrafluoroborate.

14. A method for preparing sodium difluorooxalatoborate, characterized in that: Includes steps: (1) sodium oxalate is reacted with boron trifluoride or a boron trifluoride complex in a solvent to obtain a reaction product comprising a reaction solution containing sodium difluorooxalatoborate solute and sodium tetrafluoroborate solid. thing; (2) separating the reaction product to obtain a solution containing sodium difluorooxalatoborate and a sodium tetrafluoroborate solid; (3) recrystallizing the solution containing sodium difluorooxalatoborate to obtain sodium difluorooxalatoborate; (4) Thermally decomposing solid sodium tetrafluoroborate to generate boron trifluoride or a boron trifluoride complex, and recycling the generated boron trifluoride or boron trifluoride complex into step (1) as a raw material.

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