A method for one-pot preparation of (difluorophosphoryloxy)trifluoroborate

Abstract

The application discloses a one-pot method for preparing (difluorophosphoryloxy) trifluoroborate, which comprises the following steps: adding hexafluorophosphate, a siloxane compound, boron trifluoride or a boron trifluoride complex and a reaction solvent into a reactor at one time, or adding the hexafluorophosphate, the boron trifluoride or the boron trifluoride complex and the reaction solvent into the reactor at one time and then adding the siloxane compound in the form of dropwise addition, and obtaining a (difluorophosphoryloxy) trifluoroborate reaction solution through reaction; and the reaction solution is subjected to reduced-pressure distillation to remove the reaction solvent and fluorosilane gas, so as to obtain a (difluorophosphoryloxy) trifluoroborate product containing at least 75 wt% of (difluorophosphoryloxy) trifluoroborate. The application has the advantages of high product purity, good quality, high raw material utilization rate and low cost.

Description

Technical Field

[0001] This invention relates to the field of synthesis, and in particular to a one-pot method for preparing electrolyte additives lithium (difluorophosphoryloxy)trifluoroborate or sodium (difluorophosphoryloxy)trifluoroborate. Background Technology

[0002] Electrolyte additives are an indispensable component of lithium-ion or sodium-ion batteries. They are mainly responsible for building a stable electrode / electrolyte interface film to achieve electronic insulation and facilitate the transport of lithium or sodium ions. Under the influence of different additives and functional groups, the composition and structure of the battery interface film are changed, which ultimately affects the battery's cycle life, high-temperature storage, and low-temperature discharge performance.

[0003] Boron-containing additives, due to the electron-deficient effect of boron atoms, can dissolve inorganic lithium salts such as LiF on the surface of the interfacial film, thereby reducing the battery's internal resistance and improving its low-temperature performance. Phosphorus-containing additives, such as phosphate esters and phosphates, have strong interactions between their "P=O" functional groups and transition metal elements on the positive electrode surface, thus forming a stable positive electrode interfacial film. This improves the battery's storage and cycle performance. Furthermore, phosphorus-containing additives also have a certain flame-retardant effect in the electrolyte. When both phosphorus and boron are present in an additive, they can simultaneously possess the aforementioned advantages.

[0004] Patent CN102414902A discloses an electrolyte salt containing both boron and phosphorus and its synthesis method. The method involves dissolving a boron trifluoride diethyl ether complex in dimethyl carbonate, followed by the addition of lithium difluorophosphate to obtain a dimethyl carbonate solution containing LiBF3 (PO2F2). According to its spectral data, the product also contains lithium bis(difluorophosphoryloxy)difluoroborate. The resulting product is a mixture of lithium (difluorophosphoryloxy)trifluoroborate and lithium bis(difluorophosphoryloxy)difluoroborate. Repeated experiments show that the mixture contains approximately one-third lithium bis(difluorophosphoryloxy)difluoroborate. However, in the electrolyte formulation process of the lithium battery industry, single substances are usually added, and mixtures are limited in many applications. Therefore, a higher purity lithium (difluorophosphoryloxy)trifluoroborate product is needed. Furthermore, the stability of disubstituted novel fluorinated lithium salt compounds is worse than that of monosubstituted novel fluorinated lithium salt compounds, which affects battery performance.

[0005] Patent CN115441052A also discloses a method for preparing lithium (difluorophosphoryloxy)trifluoroborate, using lithium difluorophosphate, boron trifluoride, or a boron trifluoride complex as raw materials. During the reaction, lithium tetrafluoroborate, as an additive promoter, removes disubstituted bis(difluorophosphoryloxy)difluoroborate, yielding a mixture of lithium (difluorophosphoryloxy)trifluoroborate and lithium tetrafluoroborate. While this method removes bis(difluorophosphoryloxy)difluoroborate, it introduces a new impurity, lithium tetrafluoroborate. Lithium tetrafluoroborate has low conductivity, which degrades the battery's low-temperature performance and cycle performance.

[0006] Both methods use lithium difluorophosphate as a raw material, regardless of whether the slightly less stable lithium bis(difluorophosphoryloxy)difluoroborate is removed. However, lithium difluorophosphate has low solubility in most solvents, which will result in high turbidity of the prepared lithium (difluorophosphoryloxy)trifluoroborate solution. When its addition amount in the electrolyte is high, the quality of the electrolyte will not meet industry standards.

[0007] Sodium salt additives play a crucial role in constructing a robust electrode / electrolyte interface film for sodium-ion batteries, ultimately affecting battery cycle life, high-temperature storage, and low-temperature discharge performance. The preparation of high-purity sodium trifluoroborate (difluorophosphoryloxy) also has significant commercial value.

[0008] Therefore, a method for preparing high-purity, high-quality (difluorophosphoryloxy)trifluoroborate is proposed, which is beneficial to improving the quality of electrolytes and further improving the performance of lithium-ion batteries or sodium-ion batteries. Summary of the Invention

[0009] To address the aforementioned technical problems, this invention proposes a one-pot method for preparing (difluorophosphoryloxy)trifluoroborate products that improves purity, reduces turbidity, and enhances product quality. This method is also simple to operate, avoids crystallization processes, increases raw material utilization, reduces costs, and is suitable for industrial application.

[0010] The objective of this invention is achieved through the following technical solution:

[0011] A one-pot method for preparing (difluorophosphoryloxy)trifluoroborate, wherein the method involves a one-step reaction in the same reactor, specifically:

[0012] The method includes: adding hexafluorophosphate, a siloxane compound, boron trifluoride or a boron trifluoride complex, and a reaction solvent into a reactor at one time, and reacting to obtain (difluorophosphoryloxy)trifluoroborate as shown in formula (I):

[0013]

[0014] In formula (I), M is lithium or sodium.

[0015] The siloxane compound can be added to the reaction all at once, or it can be added to the reactor dropwise. That is, the method can be: adding hexafluorophosphate, boron trifluoride or boron trifluoride complex and reaction solvent to the reactor all at once, and then adding the siloxane compound dropwise to obtain (difluorophosphoryloxy)trifluoroborate.

[0016] The reaction equation is as follows:

[0017]

[0018] The hexafluorophosphate is lithium hexafluorophosphate or sodium hexafluorophosphate.

[0019] The siloxane compound is any one of the following general structural formulas (II):

[0020]

[0021] In formula (II), Y1, Y2, Y3, Y4, Y5, and Y6 are independently selected from C1-C4 hydrocarbon groups, C1-C4 hydrocarbon groups with any substituents, or groups represented by formula (A) below; any two groups among Y1, Y2, Y3, Y4, Y5, and Y6 can combine with each other to form a cyclic structure.

[0022]

[0023] In formula (A), Z1, Z2, and Z3 are independently selected from C1-C4 hydrocarbon groups, C1-C4 hydrocarbon groups with any substituents, or further replaced by groups shown in formula (A) to form groups having multiple structures of formula (A).

[0024] Preferably, Y1, Y2, Y3, Y4, Y5, and Y6 are independently selected from methyl, ethyl, vinyl, propenyl, methoxy, ethoxy, fluoroethyl, phenyl, or groups represented by formula (A) above; any two groups among Y1, Y2, Y3, Y4, Y5, and Y6 can be combined to form a cyclic structure.

[0025] In formula (A), Z1, Z2, and Z3 are independently selected from methyl, ethyl, vinyl, propenyl, methoxy, ethoxy, fluoroethyl, phenyl, or further substituted by the groups shown in formula (A) to form groups having multiple structures of formula (A).

[0026] More preferably, the siloxane compound is selected from at least one of the compounds shown in the following structures:

[0027]

[0028] Most preferably, the siloxane compound is selected from at least one of the compounds shown in the following structures:

[0029]

[0030] The reaction temperature and reaction time of this invention only need to meet the requirements of the reaction. Preferably, the reaction temperature is 10-90°C and the reaction time is 1-24 hours. More preferably, the reaction temperature is 30-70°C and the reaction time is 3-12 hours.

[0031] In the one-pot preparation process described in this invention, the molar ratio of hexafluorophosphate, siloxane compound, boron trifluoride or boron trifluoride complex is 1:(1.9-3.0):(1-1.5), preferably 1:(2.0-2.5):(1-1.2).

[0032] The reaction solvent of the present invention is selected from at least one of ethylene carbonate, propylene carbonate, dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, methyl acetate, ethyl acetate, methyl propionate, γ-butyrolactone, diethyl ether, ethylene glycol dimethyl ether, acetonitrile, phenylacetonitrile, or propionitrile.

[0033] Preferably, the reaction solvent is selected from commonly used reaction solvents in electrolytes, such as one, two or more of dimethyl carbonate, ethyl methyl carbonate, and diethyl carbonate.

[0034] The boron atom-providing raw material of this invention can be boron trifluoride (gas) or a boron trifluoride complex. The boron trifluoride complex is selected from at least one of the following: boron trifluoride diethyl ether complex, boron trifluoride ethylene glycol dimethyl ether complex, boron trifluoride dimethyl carbonate complex, boron trifluoride pyridine complex, boron trifluoride ethylamine complex, boron trifluoride butyl ether complex, boron trifluoride methyl ether complex, boron trifluoride acetonitrile complex, boron trifluoride piperidine complex, boron trifluoride phenol complex, boron trifluoride tetrahydrofuran complex, boron trifluoride dimethyl sulfide complex, and boron trifluoride morpholine complex. Preferably, the boron trifluoride complex is selected from at least one of boron trifluoride dimethyl carbonate complex, boron trifluoride diethyl ether complex, or boron trifluoride acetonitrile complex.

[0035] The present invention provides a one-pot method for preparing (difluorophosphoryloxy)trifluoroborate, which specifically includes the following steps:

[0036] (A1) In the presence of the above reaction solvent, hexafluorophosphate, siloxane compound, boron trifluoride or boron trifluoride complex are reacted in one pot to prepare (difluorophosphoryloxy)trifluoroborate reaction solution;

[0037] (A2) The reaction solution is subjected to vacuum distillation to remove the reaction solvent and fluorosilane gas, and a (difluorophosphoryloxy)trifluoroborate product containing at least 75 wt% (difluorophosphoryloxy)trifluoroborate is obtained based on a total fluorine-containing lithium salt or fluorine-containing sodium salt of 100 wt%.

[0038] Furthermore, in step (A2), the distillation temperature is 40–90°C and the distillation time is 0.2–24 h.

[0039] The (difluorophosphoryloxy)trifluoroborate reaction solution obtained in this invention is subjected to vacuum distillation to remove the reaction solvent and fluorosilane gas, resulting in a concentrated (difluorophosphoryloxy)trifluoroborate solution, which is the (difluorophosphoryloxy)trifluoroborate product. Since the concentrated solution is in a solvated state, it contains the reaction solvent and a solute consisting of (difluorophosphoryloxy)trifluoroborate, bis(difluorophosphoryloxy)trifluoroborate, and a small amount of byproducts, with a solute content of 10 wt% to 80 wt%. As the distillation time in step (A2) increases, the solvent content in the concentrated solution decreases, while the solute content increases, reaching a maximum of 80 wt%. When the solvent in the concentrated solution is a commonly used solvent in electrolytes, there is no need to consume excessive distillation time to increase the solute content; the concentrated solution with low solute content can be used directly as an additive. The content of (difluorophosphoryloxy)trifluoroborate and (difluorophosphoryloxy)trifluoroborate in the product described in this invention is calculated as 100 wt% of the fluorinated lithium salt excluding the solvent and a small amount of byproducts in the concentrated solution.

[0040] The (difluorophosphoryloxy)trifluoroborate product prepared by the one-pot method of this invention eliminates the need for the preparation and crystallization process of difluorophosphate, avoiding the problem of low solubility of difluorophosphate during the reaction. It also solves the turbidity problem of (difluorophosphoryloxy)trifluoroborate products prepared using the difluorophosphate (solid) raw material route. Furthermore, it ensures that the prepared (difluorophosphoryloxy)trifluoroborate product contains at least 75 wt% (difluorophosphoryloxy)trifluoroborate, and may even contain up to nearly 90 wt% (difluorophosphoryloxy)trifluoroborate.

[0041] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0042] 1. This invention uses hexafluorophosphate, siloxane compounds, boron trifluoride or boron trifluoride complexes as raw materials to prepare (difluorophosphoryloxy)trifluoroborate in a one-pot process via a single reaction. This avoids the product turbidity problem caused by the solubility of difluorophosphate in the difluorophosphate raw material route, thus improving product quality. At the same time, it avoids the difluorophosphate crystallization process, making the operation simple, improving raw material utilization, increasing production efficiency, and reducing costs, making it very suitable for industrial application.

[0043] 2. The lithium or sodium salt products prepared by the one-pot method of the present invention contain at least 75 wt% (difluorophosphoryloxy) trifluoroborate, and up to nearly 90 wt%. Compared with the traditional preparation method using difluorophosphate as raw material, the products obtained have the advantages of high purity and good quality. Attached Figure Description

[0044] Figure 1 Product 1# prepared in Example 1 of this invention 19 F-NMR spectrum;

[0045] Figure 2 Product 1# prepared in Example 1 of this invention 31 p-NMR spectrum;

[0046] Figure 3 The control sample 1# prepared for Comparative Example 1 of this invention 19 F-NMR spectrum;

[0047] Figure 4 The control sample 1# prepared for Comparative Example 1 of this invention 31 P-NMR image. Detailed Implementation

[0048] The present invention will be further described below with reference to specific embodiments, but the invention is not limited to these specific embodiments. Those skilled in the art should recognize that the present invention covers all alternatives, improvements, and equivalents that may be included within the scope of the claims.

[0049] The structure and content of the products and control samples obtained in Examples 1-13 and Comparative Examples 1-3 of this invention were determined by 400M nuclear magnetic resonance fluorine spectroscopy (NMR spectroscopy). 19 F-NMR) and 400M nuclear magnetic resonance phosphorus spectrum (F-NMR) 31 Characterization was performed using P-NMR. The method involved adding a small amount of product to an NMR tube and diluting it with an appropriate amount of diethyl carbonate, ensuring the solution height did not exceed one-third of the NMR tube height. Since the NMR spectra of the same substance are essentially consistent and the peak position shifts are minimal under the same solvent conditions, detailed NMR spectra and results are only described in Example 1 and Comparative Example 1. Furthermore, the NMR spectrum of the sodium salt is essentially consistent with the corresponding lithium salt NMR spectrum, showing only a slight overall shift; therefore, the NMR results for the sodium salt are simply described in Example 13.

[0050] Example 1

[0051] This embodiment provides a one-pot method for preparing (difluorophosphoryloxy)trifluoroborate lithium, specifically including the following steps:

[0052] S1. In a drying room with a dew point of -40°C, add 0.2 mol lithium hexafluorophosphate (99% purity), 0.4 mol hexamethyldisiloxane (99% purity), 0.2 mol boron trifluoride diethyl carbonate complex, and 200 mL diethyl carbonate to a reaction flask. Start stirring to mix the system evenly and react at 45°C for 5 h to obtain a reaction solution of (difluorophosphoryloxy)trifluoroborate.

[0053] S2. The reaction solvent and residual fluorosilane gas in the reaction solution are removed by vacuum distillation. The vacuum distillation temperature is controlled at 60℃ and the time is controlled at 0.5h to obtain a concentrated solution of (difluorophosphoryloxy)trifluoroborate, which is designated as product 1#.

[0054] The product is colorless and transparent, and its turbidity is 3.85 NTU when analyzed by a turbidimeter.

[0055] Appendix Figure 1 and attached Figure 2 Product #1 is given separately. 19 F-NMR and 31 p-NMR spectrum, from Figure 1 , Figure 2 It can be known that:

[0056] The NMR F-spectrum of Product 1# is shown below:

[0057] Lithium trifluoroborate (difluorophosphoryloxy): δ = -92.46 ppm (d, J = 958.8 Hz), δ = -157.61 ppm (s)

[0058] Lithium bis(difluorophosphoryloxy)trifluoroborate: δ = -92.05 ppm (d, J = 963.5 Hz), δ = -151.95 ppm (s)

[0059] The NMR P-spectrum of product #1 is shown below:

[0060] (Difluorophosphoryloxy)trifluoroborate: δ=-27.94ppm(t,J=958.8Hz)

[0061] Lithium bis(difluorophosphoryloxy)trifluoroborate: δ = -29.30 ppm (t, J = 963.5 Hz)

[0062] Integrating the peak area of ​​the NMR P-spectrum, the byproduct peak (marked with the symbol "Δ") occupies a low integrated area (<2%) and its composition is unknown, making it impossible to calculate and convert it into a mass percentage; therefore, it is ignored in this embodiment. By comparing the integrated areas of lithium (difluorophosphoryloxy)trifluoroborate (marked with the symbol "■") and bis(difluorophosphoryloxy)trifluoroborate (marked with the symbol "●") in the P-spectrum and converting them into mass percentages, based on a total fluorinated lithium salt content of 100 wt%, product 1# is found to contain 87.0 wt% (difluorophosphoryloxy)trifluoroborate and 13.0 wt% bis(difluorophosphoryloxy)trifluoroborate. Further area integration conversion using the F-spectrum showed consistent results and high calculation reliability.

[0063] Example 2

[0064] The operation in this embodiment is the same as in embodiment 1, except that the amount of hexamethyldisiloxane added in step S1 is increased to 0.5 mol, and a concentrated solution of lithium trifluoroborate (difluorophosphoryloxy) is obtained, which is designated as product 2#.

[0065] The product contains a small amount of turbidity, which may be a byproduct of the reaction between lithium (difluorophosphoryloxy)trifluoroborate and excess hexamethyldisiloxane. The turbidity was 5.33 NTU when analyzed by a turbidimeter.

[0066] After filtering out the turbidity from product #2, proceed with... 19 F-NMR and 31 P-NMR analysis, based on a total fluorinated lithium salt content of 100 wt%, showed that the product contained 84.3 wt% (difluorophosphoryloxy)trifluoroborate and 15.7 wt% bis(difluorophosphoryloxy)trifluoroborate.

[0067] Example 3

[0068] The operation in this embodiment is the same as in embodiment 1, except that the amount of boron trifluoride diethyl carbonate complex added in step S1 is increased to 0.25 mol, and a concentrated solution of (difluorophosphoryloxy)trifluoroborate is obtained, which is designated as product 3#.

[0069] The product is colorless and transparent, and its turbidity, as analyzed by a turbidimeter, is 3.87 NTU.

[0070] Product #3 was processed 19 F-NMR and 31 P-NMR analysis, based on a total fluorinated lithium salt content of 100 wt%, showed that the product contained 86.9 wt% (difluorophosphoryloxy)trifluoroborate and 13.1 wt% bis(difluorophosphoryloxy)trifluoroborate.

[0071] Example 4

[0072] The operation of this embodiment is the same as that of Embodiment 1, except that: in step S1, the amount of hexamethyldisiloxane added is increased to 0.6 mol, and the amount of boron trifluoride diethyl carbonate complex added is increased to 0.3 mol, to obtain a concentrated solution of (difluorophosphoryloxy)trifluoroborate, which is designated as product 4#.

[0073] The product contains a small amount of turbidity, which was analyzed by a turbidimeter and the turbidity was 8.16 NTU.

[0074] After removing turbidity by filter #4 of product, proceed with... 19 F-NMR and 31 P-NMR analysis, based on a total fluorinated lithium salt content of 100 wt%, showed that the product contained 81.5 wt% (difluorophosphoryloxy)trifluoroborate and 18.5 wt% bis(difluorophosphoryloxy)trifluoroborate.

[0075] Example 5

[0076] The operation in this embodiment is the same as in embodiment 1, except that the reaction temperature in step S1 is increased to 60°C to obtain a concentrated solution of lithium trifluoroborate (difluorophosphoryloxy)trifluoroborate, which is designated as product 5#.

[0077] The product is colorless and transparent, and its turbidity, as analyzed by a turbidimeter, is 3.82 NTU.

[0078] Product #5 was processed 19 F-NMR and 31 P-NMR analysis, based on a total fluorinated lithium salt content of 100 wt%, showed that the product contained 85.4 wt% (difluorophosphoryloxy)trifluoroborate and 14.6 wt% bis(difluorophosphoryloxy)trifluoroborate.

[0079] Example 6

[0080] The operation in this embodiment is the same as in embodiment 1, except that the reaction temperature in step S1 is increased to 80°C to obtain a concentrated solution of lithium trifluoroborate (difluorophosphoryloxy)trifluoroborate, which is designated as product 6#.

[0081] The product is colorless and transparent, and its turbidity, as analyzed by a turbidimeter, is 3.84 NTU.

[0082] Product #6 was processed 19 F-NMR and 31 P-NMR analysis, based on a total fluorinated lithium salt content of 100 wt%, showed that the product contained 79.3 wt% (difluorophosphoryloxy)trifluoroborate and 20.7 wt% bis(difluorophosphoryloxy)trifluoroborate.

[0083] Example 7

[0084] The operation in this embodiment is the same as in embodiment 1, except that the reaction time in step S1 is increased to 10 hours to obtain a concentrated solution of lithium trifluoroborate (difluorophosphoryloxy)trifluoroborate, which is designated as product 7#.

[0085] The product is colorless and transparent, and its turbidity, as analyzed by a turbidimeter, is 3.82 NTU.

[0086] Product #7 was processed 19 F-NMR and 31 P-NMR analysis, based on a total fluorinated lithium salt content of 100 wt%, showed that the product contained 78.0 wt% (difluorophosphoryloxy)trifluoroborate and 22.0 wt% bis(difluorophosphoryloxy)trifluoroborate.

[0087] Example 8

[0088] The operation of this embodiment is the same as that of Embodiment 1, except that in step S1, 0.2 mol of lithium hexafluorophosphate (99% purity), 0.2 mol of boron trifluoride diethyl carbonate complex and 200 mL of diethyl carbonate are added to the reaction flask first. Then, 0.4 mol of hexamethyldisiloxane (99% purity) is added to the reaction flask dropwise through a constant pressure dropping funnel to obtain a concentrated solution of (difluorophosphoryloxy)trifluoroborate, which is designated as product 8#.

[0089] The product is colorless and transparent, and its turbidity, as analyzed by a turbidimeter, is 3.80 NTU.

[0090] Product #8 was processed 19 F-NMR and 31 P-NMR analysis, based on a total fluorinated lithium salt content of 100 wt%, showed that the product contained 83.8 wt% (difluorophosphoryloxy)trifluoroborate and 16.2 wt% bis(difluorophosphoryloxy)trifluoroborate.

[0091] Example 9

[0092] The operation of this embodiment is the same as that of embodiment 4, except that in step S1, 0.2 mol of lithium hexafluorophosphate (99% purity), 0.3 mol of boron trifluoride diethyl carbonate complex and 200 mL of diethyl carbonate are added to the reaction flask first. Then, 0.6 mol of hexamethyldisiloxane (99% purity) is added to the reaction flask dropwise through a constant pressure dropping funnel to obtain a concentrated solution of (difluorophosphoryloxy)trifluoroborate, which is designated as product 9#.

[0093] The product contains a small amount of turbidity, which was analyzed by a turbidimeter and the turbidity was 8.12 NTU.

[0094] After removing turbidity by filter #9 of the product, proceed with... 19 F-NMR and31 P-NMR analysis, based on a total fluorinated lithium salt content of 100 wt%, showed that the product contained 75.2 wt% (difluorophosphoryloxy)trifluoroborate and 24.8 wt% bis(difluorophosphoryloxy)trifluoroborate.

[0095] Example 10

[0096] The operation of this embodiment is the same as that of embodiment 1, except that: in step S1, hexamethyldisiloxane is replaced with octamethyltrisiloxane and the amount added is reduced to 0.2 mol, and lithium trifluoroborate concentrate (difluorophosphoryloxy) is obtained, which is denoted as product 10#.

[0097] The product is colorless and transparent, and its turbidity, as analyzed by a turbidimeter, is 3.81 NTU.

[0098] Product #10 was processed 19 F-NMR and 31 P-NMR analysis, based on a total fluorinated lithium salt content of 100 wt%, showed that the product contained 83.2 wt% (difluorophosphoryloxy)trifluoroborate and 16.8 wt% bis(difluorophosphoryloxy)trifluoroborate.

[0099] Example 11

[0100] The operation of this embodiment is the same as that of embodiment 1, except that: in step S1, hexamethyldisiloxane is replaced with hexamethylcyclotrisiloxane and the amount added is reduced to 0.14 mol, and lithium trifluoroborate concentrate (difluorophosphoryloxy) is obtained, which is denoted as product 11#.

[0101] The product is colorless and transparent, and its turbidity, as analyzed by a turbidimeter, is 3.78 NTU.

[0102] Product #11 was processed 19 F-NMR and 31 P-NMR analysis, based on a total fluorinated lithium salt content of 100 wt%, showed that the product contained 80.8 wt% (difluorophosphoryloxy)trifluoroborate and 19.2 wt% bis(difluorophosphoryloxy)trifluoroborate.

[0103] Example 12

[0104] The operation in this embodiment is the same as in embodiment 1, except that: in step S1, hexamethyldisiloxane is replaced with octamethylcyclotetrasiloxane and the amount added is reduced to 0.10 mol to obtain a concentrated solution of (difluorophosphoryloxy)trifluoroborate, which is designated as product 12#.

[0105] The product is colorless and transparent, and its turbidity, as analyzed by a turbidimeter, is 3.75 NTU.

[0106] Product #12 was processed 19 F-NMR and 31 P-NMR analysis, based on a total fluorinated lithium salt content of 100 wt%, showed that the product contained 78.9 wt% (difluorophosphoryloxy)trifluoroborate and 21.1 wt% (bis(difluorophosphoryloxy)trifluoroborate).

[0107] Example 13

[0108] The operation in this embodiment is the same as in embodiment 1, except that in step S1, lithium hexafluorophosphate is replaced with sodium hexafluorophosphate to obtain sodium trifluoroborate concentrate, which is designated as product 13#.

[0109] The product is colorless and transparent, and its turbidity was measured to be 3.61 NTU using a turbidimeter.

[0110] The NMR F-spectrum of product 13# is shown below:

[0111] Sodium trifluoroborate (difluorophosphoryloxy): δ = -92.48 ppm (d, J = 958.8 Hz), δ = -162.61 ppm (s)

[0112] Sodium bis(difluorophosphoryloxy)trifluoroborate: δ = -92.07 ppm (d, J = 963.5 Hz), δ = -156.95 ppm (s)

[0113] The NMR P-spectrum of product 13# is shown below:

[0114] Sodium trifluoroborate (difluorophosphoryloxy): δ = -27.88 ppm (t, J = 958.8 Hz)

[0115] Sodium bis(difluorophosphoryloxy)trifluoroborate: δ = -29.24 ppm (t, J = 963.5 Hz)

[0116] The area of ​​the P-spectrum NMR peak was integrated and converted to a mass percentage. Assuming a total sodium fluoride content of 100 wt%, product #1 contained 88.2 wt% sodium (difluorophosphoryloxy)trifluoroborate and 11.8 wt% sodium bis(difluorophosphoryloxy)trifluoroborate. Further area integration using the F-spectrum revealed consistent results and high reliability of the calculation.

[0117] Comparative Example 1

[0118] S1. In a drying room with a dew point of -40°C, add 0.2 mol lithium difluorophosphate (99% purity), 0.2 mol boron trifluoride diethyl carbonate complex and 200 ml diethyl carbonate to a reaction flask, turn on the stirrer to mix the system evenly, and react at 45°C for 5 h to obtain the reaction solution of (difluorophosphoryloxy)trifluoroborate.

[0119] S2. The reaction solvent in the reaction solution was removed by vacuum distillation. The vacuum distillation temperature was controlled at 60℃ and the time was controlled at 0.5h to obtain a concentrated solution of lithium (difluorophosphoryloxy)trifluoroborate, which was designated as control sample 1#.

[0120] The control sample contained a small amount of turbidity, and the turbidity was 12.35 NTU when analyzed by a turbidimeter.

[0121] Appendix Figure 3 and attached Figure 4 The results for control sample 1# are given respectively. 19 F-NMR and 31 p-NMR spectrum, from Figure 3 , Figure 4 It can be seen that the peak positions of the substances are the same, which confirms that the product contains lithium (difluorophosphoryloxy)trifluoroborate and lithium bis(difluorophosphoryloxy)trifluoroborate.

[0122] By integrating the peak areas of the NMR spectrum and calculating, it was found that, based on a total fluorinated lithium salt content of 100 wt%, the control sample contained 63.4 wt% lithium (difluorophosphoryloxy)trifluoroborate and 36.6 wt% lithium bis(difluorophosphoryloxy)trifluoroborate.

[0123] Comparative Example 2

[0124] S1. In a drying room with a dew point of -40℃, add 0.2 mol lithium hexafluorophosphate (99% purity), 0.4 mol hexamethyldisiloxane (99% purity), and 200 ml diethyl carbonate to a reaction flask, start stirring to mix the system evenly, and react at 45℃ for 5 h to obtain lithium difluorophosphate reaction solution.

[0125] S2. Add 0.2 mol of diethyl boron carbonate complex to the lithium difluorophosphate reaction solution, turn on the stirrer to mix the system evenly, and react at 45°C for 1 h to obtain the reaction solution of lithium (difluorophosphoryloxy)trifluoroborate.

[0126] S3. The reaction solvent in the reaction solution was removed by vacuum distillation. The vacuum distillation temperature was controlled at 60℃ and the time was controlled at 0.5h to obtain a concentrated solution of lithium trifluoroborate (difluorophosphoryloxy) and it was designated as control sample 2#.

[0127] The control sample contained a small amount of turbidity, and the turbidity was 13.12 NTU when analyzed by a turbidimeter.

[0128] After filtering control sample #2, proceed with... 19 F-NMR and 31P-NMR analysis, based on a total fluorinated lithium salt content of 100 wt%, showed that the control sample contained 64.3 wt% (difluorophosphoryloxy)trifluoroborate and 35.7 wt% (bis(difluorophosphoryloxy)trifluoroborate).

[0129] Comparative Example 3

[0130] The procedure for this comparative example is the same as that for comparative example 1, except that lithium difluorophosphate is replaced with sodium difluorophosphate to obtain a concentrated solution of sodium trifluoroborate (difluorophosphoryloxy)trifluoroborate, which is designated as control sample 3#.

[0131] The product contains a small amount of turbidity, which was analyzed by a turbidimeter and found to be 10.14 NTU.

[0132] After filtering out turbidity from control sample #3, proceed with... 19 F-NMR and 31 P-NMR analysis, based on a total fluorinated lithium salt content of 100 wt%, showed that the product contained 64.5 wt% sodium (difluorophosphoryloxy)trifluoroborate and 35.5 wt% sodium bis(difluorophosphoryloxy)trifluoroborate.

[0133] Comparing the reaction results of Example 1 and Comparative Examples 1 and 2, and Example 13 and Comparative Example 3, it can be seen that the (difluorophosphoryloxy)trifluoroborate prepared by the one-pot method of the present invention has lower turbidity and higher product purity compared with the (difluorophosphoryloxy)trifluoroborate prepared by conventional methods using difluorophosphate or difluorophosphate reaction solution as raw materials. The product purity is significantly improved. It is speculated that the reason may be that difluorophosphate has low solubility in common organic solvents (≤1wt%). Therefore, when difluorophosphate is used as a raw material, it is not evenly dispersed in organic solvents, which greatly increases the probability of multiple difluorophosphates around a single boron trifluoride molecule. As a result, the content of bis(difluorophosphoryloxy)trifluoroborate in the product is higher, that is, the content of monosubstituted (difluorophosphoryloxy)trifluoroborate is lower. When hexafluorophosphate is used as a raw material, it has high solubility (≥30wt%) and uniform dispersion in conventional organic solvents. Therefore, it can be combined with siloxane compounds and boron trifluoride to obtain high-purity (difluorophosphoryloxy)trifluoroborate products according to the theoretical route.

[0134] Comparing Examples 1-4, it can be seen that when the amount of hexamethyldisiloxane added to the reaction raw materials is high, the turbidity of the product will increase slightly. It is speculated that this may be a reaction byproduct of lithium (difluorophosphoryloxy)trifluoroborate and hexamethyldisiloxane, which will reduce the content of lithium (difluorophosphoryloxy)trifluoroborate in the product.

[0135] Comparing Examples 1, 5, and 6 reveals that when the reaction temperature is too high, the content of lithium (difluorophosphoryloxy)trifluoroborate in the product decreases. Comparing Examples 1 and 7 reveals that when the reaction time is longer, the two molecules of lithium (difluorophosphoryloxy)trifluoroborate react to form bis(difluorophosphoryloxy)trifluoroborate, thus reducing the content of lithium (difluorophosphoryloxy)trifluoroborate in the product.

[0136] Therefore, the one-pot process for preparing (difluorophosphoryloxy)trifluoroborate using the present invention, compared with the traditional process using difluorophosphate or difluorophosphate reaction solution as raw materials, can not only obtain a higher content of (difluorophosphoryloxy)trifluoroborate and improve product purity, but also avoid the difluorophosphate crystallization process, improve raw material utilization, increase production efficiency, and reduce costs, making it very suitable for industrial application.

Claims

1. A one-pot method for preparing (difluorophosphoryloxy)trifluoroboron salt, characterized in that: The method includes: adding hexafluorophosphate, a siloxane compound, boron trifluoride or a boron trifluoride complex, and a reaction solvent into a reactor at one time, and reacting to obtain (difluorophosphoryloxy)trifluoroborate as shown in formula (I): （I） In formula (I), M is lithium or sodium; The hexafluorophosphate is lithium hexafluorophosphate or sodium hexafluorophosphate; The siloxane compound is selected from at least one of the following structures: The reaction temperature is 10–90℃, and the reaction time is 1–24 h; The molar ratio of the amount of hexafluorophosphate, siloxane compound, boron trifluoride or boron trifluoride complex added is 1:(1.9 to 3.0):(1 to 1.5).

2. The method for preparing (difluorophosphoryloxy)trifluoroborate in a one-pot process according to claim 1, characterized in that: Hexafluorophosphate, boron trifluoride or boron trifluoride complex, and reaction solvent are added to a reactor, and a siloxane compound is added dropwise to obtain (difluorophosphoryloxy)trifluoroborate.

3. The method for preparing (difluorophosphoryloxy)trifluoroborate in a one-pot process according to claim 1 or 2, characterized in that: The reaction solvent is selected from at least one of ethylene carbonate, propylene carbonate, dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, methyl acetate, ethyl acetate, methyl propionate, γ-butyrolactone, diethyl ether, ethylene glycol dimethyl ether, acetonitrile, phenylacetonitrile, or propionitrile.

4. The method for preparing (difluorophosphoryloxy)trifluoroborate in a one-pot process according to claim 3, characterized in that: The reaction solvent is selected from at least one of dimethyl carbonate, ethyl methyl carbonate, and diethyl carbonate.

5. The method for preparing (difluorophosphoryloxy)trifluoroborate in a one-pot process according to claim 1 or 2, characterized in that: The boron trifluoride complex is selected from at least one of the following: boron trifluoride diethyl ether complex, boron trifluoride ethylene glycol dimethyl ether complex, boron trifluoride dimethyl carbonate complex, boron trifluoride pyridine complex, boron trifluoride ethylamine complex, boron trifluoride butyl ether complex, boron trifluoride methyl ether complex, boron trifluoride acetonitrile complex, boron trifluoride piperidine complex, boron trifluoride phenol complex, boron trifluoride tetrahydrofuran complex, boron trifluoride dimethyl sulfide complex, and boron trifluoride morpholine complex.

6. The method for preparing (difluorophosphoryloxy)trifluoroborate in a one-pot process according to claim 1 or 2, characterized in that, The method specifically includes: (A1) In the presence of a reaction solvent, a reaction solution of (difluorophosphoryloxy)trifluoroborate is prepared by one-pot reaction of hexafluorophosphate, siloxane compound, boron trifluoride or boron trifluoride complex; (A2) The reaction solution is subjected to vacuum distillation to remove the reaction solvent and fluorosilane gas, and the total amount of fluorinated lithium salt or fluorinated sodium salt is 100wt% to obtain a (difluorophosphoryloxy)trifluoroborate product containing at least 75wt% (difluorophosphoryloxy)trifluoroborate.

7. The method for preparing (difluorophosphoryloxy)trifluoroborate in a one-pot process according to claim 6, characterized in that: In step (A2), the distillation temperature is 40–90℃ and the distillation time is 0.2–24h.

8. The method for preparing (difluorophosphoryloxy)trifluoroborate in a one-pot process according to claim 6, characterized in that: Based on a total of 100 wt% of fluorinated lithium salt or fluorinated sodium salt, the (difluorophosphoryloxy)trifluoroborate product obtained in step (A2) contains at least 85 wt% (difluorophosphoryloxy)trifluoroborate.

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