Silicon difluorophosphate and preparation method thereof

Abstract

The invention belongs to the technical field of batteries, and particularly discloses silicon difluorophosphate and a preparation method thereof.Under the conditions that the pressure ranges from 0.01 MPa to 0.6 MPa and the temperature ranges from 5 DEG C to 80 DEG C, organic silicon alkoxide in the formula I reacts with POF3 gas, and silicon difluorophosphate in the formula II is obtained; in the formula I # imgabs 1 # and the formula II, R1, R2 and R3 respectively and independently comprise any one of a C1-C6 alkyl group, a C2-C6 alkenyl group, a C2-C6 alkynyl group and a substituted or unsubstituted phenyl group; m comprises any one of lithium, sodium and potassium; the POF3 gas is excessive by 5%-30% according to the stoichiometric ratio. In the method, the organic silicon alkoxide shown in the formula I and POF3 gas are extremely easy to react, the reaction rate is high, the reaction condition is mild, the reaction time is short, the reaction yield is high, the generated fluoride salt can be recycled, and the atom utilization rate is high.

Description

Technical Field

[0001] This application belongs to the technical field of batteries, and specifically relates to silicon difluorophosphate and its preparation method. Background Art

[0002] With the rapid development of markets such as electronic devices, electric vehicles, smart homes, power tools, and intelligent transportation, the demand for batteries is also continuously increasing. Currently, basically all commercialized batteries are liquid batteries, that is, the batteries contain electrolytes, and the performance of the batteries can be improved by adding additives to the electrolytes.

[0003] When silicon difluorophosphate is used as an electrolyte additive in batteries, it has the effects of reducing the initial impedance and the impedance after storage, and improving the cycling performance. However, the current preparation conditions for silicon difluorophosphate with low impurity content, high purity, and high yield are harsh and not conducive to mass production. Therefore, the related technologies for the method of preparing silicon difluorophosphate still need to be improved. Summary of the Invention

[0004] This application aims to solve at least one of the technical problems in the related technologies to some extent. For this purpose, this application proposes a method for preparing silicon difluorophosphate with a fast reaction rate, mild reaction conditions, short reaction time, high reaction yield, or high atom utilization rate, and the silicon difluorophosphate prepared by this method.

[0005] The first aspect of this application proposes a method for preparing silicon difluorophosphate, including: Under the conditions of a pressure of 0.01 MPa to 0.6 MPa and a temperature of 5 °C to 80 °C, reacting an organosilicate shown by Formula I with POF3 gas to obtain a silicon difluorophosphate shown by Formula II; Formula I Formula II Wherein, R1, R2, and R3 each independently include any one of C1-C6 alkyl, C2-C6 alkenyl, C2-C6 alkynyl, and substituted or unsubstituted phenyl; M includes any one of lithium, sodium, and potassium; Calculated according to the stoichiometric ratio of the reaction of the organosilicate and the POF3 gas, the POF3 gas is in an excess of 5% to 30%.

[0006] The preparation method of the first aspect of this application has at least the following beneficial effects: fast reaction rate, mild reaction conditions, short reaction time, high reaction yield (such as a yield ≥ 80%), the generated fluoride salts can be recycled, and the atom utilization rate is relatively high.

[0007] In addition, according to the preparation method of the above embodiments of this application, the following additional technical features may also be possessed: In some embodiments, the reaction of the organosilicate and the POF3 gas includes: Mix the organosilicate and an organic solvent to obtain a first mixture; Introduce the POF3 gas into the first mixture.

[0008] Mixing the organosilicate and the organic solvent can, on the one hand, effectively dissolve the organosilicate, making the reaction easier to proceed and smoothly obtaining the target product, silicon difluorophosphate ester. On the other hand, after the reaction, the organic solvent helps to separate the product from the solvent by conventional means such as distillation and rectification, simplifying the subsequent treatment process.

[0009] In some embodiments, the reaction temperature of the organosilicate and the POF3 gas can specifically be 20°C to 40°C. Thus, it is beneficial for the reaction to proceed smoothly and improve the reaction efficiency.

[0010] In some embodiments, the reaction pressure of the organosilicate and the POF3 gas can specifically be 0.2 MPa to 0.45 MPa. Thus, the reaction rate can be further increased and the impurities in the product can be reduced.

[0011] In some embodiments, the reaction time of the organosilicate and the POF3 gas is 1 h to 6 h, and specifically can be 2.5 h to 4 h. Thus, the reaction can be completed within the above time range, which is beneficial to reducing the reaction cost.

[0012] In some embodiments, the organosilicate and the POF3 gas are reacted under the condition that the water content ≤ 50 ppm. Thus, impurities generated by the hydrolysis of silicon difluorophosphate ester can be effectively reduced, and silicon difluorophosphate ester with higher purity can be obtained.

[0013] In some embodiments, calculated according to the stoichiometric ratio of the reaction of the organosilicate and the POF3 gas, the POF3 gas is in an excess of 20%. Thus, the reaction can be promoted to be more complete, and at the same time, the reaction rate can be increased, raw materials can be saved, and the cost can be reduced.

[0014] In some embodiments, the mass ratio of the organosilicate to the organic solvent is 1:2 to 1:8. Thus, it helps to reduce the moisture in the reaction system and does not cause waste of the organic solvent.

[0015] In some embodiments, the organic solvent includes at least one of dichloromethane, dichloroethane, ethyl acetate, acetonitrile, ether, ethylene glycol dimethyl ether, and dimethyl carbonate. The above organic solvents have excellent solubility, stable chemical properties, are not prone to side reactions with raw materials, and are easy to separate from the product.

[0016] In some embodiments, during the reaction between the organosilicate and the POF3 gas, the reaction process is monitored by 19F NMR spectroscopy, and the reaction is stopped after the content of the POF3 gas and / or the silicon difluorophosphate ester remains unchanged. This is conducive to a more complete reaction between the organosilicate and the POF3 gas and avoids waste of raw materials.

[0017] In some embodiments, after the reaction between the organosilicate and the POF3 gas is completed, at least one of the following post-treatment steps is further included: Purging with nitrogen to remove the POF3 gas; Filtering to remove the metal fluoride precipitate to obtain a filtrate; Rectifying the filtrate under the conditions of 10°C to 60°C and -0.09 MPa to 0.098 MPa.

[0018] After the above post-treatment steps, it is beneficial to remove the unreacted POF3 gas and the product metal fluoride precipitate and improve the purity of the silicon difluorophosphate ester.

[0019] In some embodiments, each of R1, R2, and R3 independently includes any one of methyl and ethyl.

[0020] In some embodiments, the organosilicate includes , , , and at least one of lithium triethylsilanolate, sodium triethylsilanolate, and potassium triethylsilanolate.

[0021] In some embodiments, the silicon difluorophosphate ester includes and and at least one of them.

[0022] The second aspect of the present application provides a silicon difluorophosphate ester prepared by the method for preparing a silicon difluorophosphate ester described above. This silicon difluorophosphate ester has high purity and few impurities. When used as an electrolyte additive, it can effectively reduce side reactions and improve the electrochemical performance of the battery.

[0023] In some embodiments, the purity of the silicon difluorophosphate ester is ≥99.0%. Description of the Drawings

[0024] Figure 1 is the 31P NMR spectrum of the silicon difluorophosphate ester prepared in the examples of the present application.

[0025] Figure 2 is the 19F NMR spectrum of the silicon difluorophosphate ester prepared in the examples of the present application. Detailed Description of the Embodiments

[0026] Embodiments of the present application will be described in detail below, which are intended to explain the present application and should not be construed as limiting the present application.

[0027] The present application is completed based on the following discoveries and understandings of the inventors: When silicofluorophosphate is applied to a battery, it has the effects of reducing the initial impedance and the impedance after storage and improving the cycling performance. However, the inventors found that the preparation conditions for silicofluorophosphate with low impurity content, high purity and high yield are harsh and not conducive to mass production. For example, in the related art, phosphorus oxyfluoride and hexamethyldisiloxane are reacted at a molar ratio of 1:1 at room temperature for 10 days, and then silicofluorophosphate and trimethylfluorosilane are separated by distillation to obtain silicofluorophosphate. It can be seen that the preparation method in the related art is time-consuming and laborious and not conducive to mass production. In this regard, the inventors of the present application have conducted in-depth exploration on the preparation method of silicofluorophosphate and found that organosilanolate is a nucleophile, and the central metal atom forms a bond with the siloxy part. The electropositivity of the metal atom is relatively strong, so that the siloxy anion part has a relatively high electron cloud density, and thus the siloxy anion has a strong electron-donating ability and tends to attack an electron-deficient atom or group. For POF3, the phosphorus atom is connected to oxygen atoms and fluorine atoms with strong electronegativity. Oxygen and fluorine strongly attract electrons, reducing the electron cloud density around the phosphorus atom, and the phosphorus atom has a partial positive charge, becoming an electron-deficient atom, so that POF3 has electrophilicity and tends to react with an electron-rich nucleophile. Therefore, the inventors have developed a method for preparing silicofluorophosphate by reacting a nucleophile with an electrophile. The preparation method is simple, mild, has high reaction efficiency, high product yield and is suitable for mass production.

[0028] The first aspect of the present application provides a method for preparing silicofluorophosphate, including: Under the conditions of a pressure of 0.01 MPa to 0.6 MPa and a temperature of 5 °C to 80 °C, reacting an organosilanolate shown in Formula I with POF3 gas to obtain a silicofluorophosphate shown in Formula II; Formula I Formula II Wherein, R1, R2, and R3 each independently include any one of C1-C6 alkyl, C2-C6 alkenyl, C2-C6 alkynyl, and substituted or unsubstituted phenyl; M includes any one of lithium, sodium, and potassium; Calculated according to the stoichiometric ratio of the reaction of the organosilanolate and the POF3 gas, the POF3 gas is in an excess of 5% to 30%.

[0029] The raw materials used in this application are organosilicon alkoxides and POF3, which are nucleophiles and electrophiles respectively. The silicon oxyanion (nucleophilic part) in the organosilicon alkoxide shown in Formula I will use its lone pair of electrons to attack the electron-deficient phosphorus atom in POF3, causing one P-F bond in POF3 to break. At the same time, the ionic bond between the oxygen atom and the metal ion in the organosilicon alkoxide also breaks. The oxygen atom in the silicon oxyanion uses its lone pair of electrons to form a bond with the phosphorus atom in POF3, forming a new P-O bond, thereby obtaining the product silicon difluorophosphate ester. And the fluoride anion (F - ), which breaks off from POF3, combines with the free metal ion (M + ), forming a metal fluoride (MF). Thus, the two react quickly to reach a more stable electronic structure state, so that silicon difluorophosphate ester can be prepared efficiently under mild conditions, and the reaction rate is fast, the reaction time is short, the product yield is high, and the generated fluoride salt can be recycled, with a relatively high atom utilization rate.

[0030] It should be noted that the term "C1-C6 alkyl" used in this application represents a saturated straight-chain or branched-chain monovalent hydrocarbon group containing 1-6 carbon atoms. Examples of C1-C6 alkyl include, but are not limited to, methyl (-CH3), ethyl (-CH2CH3), n-propyl (-CH2CH2CH3), isopropyl (-CH(CH3)2), n-butyl (-CH2CH2CH2CH3), isobutyl (-CH2CH(CH3)2), sec-butyl (-CH(CH3)CH2CH3), tert-butyl (-C(CH3)3), n-pentyl (-CH2CH2CH2CH2CH3), etc.

[0031] The term "C2-C6 alkenyl" represents a straight-chain or branched-chain monovalent hydrocarbon group containing 2-6 carbon atoms, with at least one unsaturated site, that is, there is a carbon-carbon sp2 double bond. Examples of C2-C6 alkenyl include, but are not limited to, vinyl (-CH=CH2), allyl (-CH2CH=CH2), 1-propenyl (-CH=CH-CH3), and so on.

[0032] The term "C2-C6 alkynyl" represents a straight-chain or branched-chain monovalent hydrocarbon group containing 2-6 carbon atoms, with at least one unsaturated site, that is, there is a carbon-carbon sp triple bond. Examples of C2-C6 alkynyl include, but are not limited to, ethynyl (-C≡CH), propargyl (-CH2C≡CH), 1-propynyl (-C≡C-CH3), and so on.

[0033] The term "substituted or unsubstituted phenyl" means that the phenyl is unsubstituted or substituted by one or more substituents. Substituted phenyl includes, but is not limited to, o-methylphenyl, m-methylphenyl, p-methylphenyl, o-ethylphenyl, m-ethylphenyl, p-ethylphenyl, o-dimethylphenyl, etc.

[0034] In some embodiments, each of R1, R2, and R3 in the organosilicate independently includes any one of methyl and ethyl. Correspondingly, each of R1, R2, and R3 in the prepared silicon difluorophosphate independently includes any one of methyl and ethyl. Thus, when the silicon difluorophosphate is used as an additive for the battery electrolyte, the impedance of the battery after initial charging and storage can be reduced, and the effect of improving the battery cycle performance can be effectively enhanced.

[0035] In some embodiments, the organosilicate includes , , , lithium triethylsilanolate, sodium triethylsilanolate, potassium triethylsilanolate, or at least one of them.

[0036] In some embodiments, the silicon difluorophosphate includes and or at least one of them. When the above specific compounds are used in the battery, the impedance of the battery after initial charging and storage can be reduced, and the effect of improving the battery cycle performance can be effectively enhanced.

[0037] In some embodiments, reacting the organosilicate with POF3 gas includes: mixing the organosilicate with an organic solvent to obtain a first mixture. On the one hand, the organosilicate has a high solubility in the organic solvent and is chemically stable, which is beneficial to the reaction with POF3 gas and basically does not cause side reactions, thus facilitating the smooth progress of the reaction; on the other hand, the organic solvent is easily separated from the product, which can further reduce the impurities in the silicon difluorophosphate and obtain a higher purity silicon difluorophosphate.

[0038] In some embodiments, the organic solvent includes at least one of dichloromethane, dichloroethane, ethyl acetate, acetonitrile, diethyl ether, ethylene glycol dimethyl ether, and dimethyl carbonate.

[0039] In some embodiments, the mass ratio of the organosilicate to the organic solvent is 1:2 to 1:8. Specifically, it can be 1:2, 1:3, 1:4, 1:5, 1:6, 1:7, 1:8, etc. Thus, it helps to reduce the moisture in the reaction system and does not cause waste of the organic solvent.

[0040] In some embodiments, reacting the organosilicate with POF3 gas includes: introducing POF3 gas into the first mixture for reaction. The reaction formula for the whole process is as follows:

[0041] In some embodiments, POF3 gas is introduced into the first mixture for reaction, and the reaction temperature is 5°C to 80°C. Specifically, it can be 5°C, 10°C, 15°C, 20°C, 25°C, 30°C, 35°C, 40°C, 45°C, 50°C, 55°C, 60°C, 65°C, 70°C, 75°C, 80°C, etc. In some other embodiments, the reaction temperature between the organosilicate and POF3 gas is 20°C to 40°C. Under the above temperature conditions, the reaction efficiency can be further improved, the conditions are mild, the side reactions are few, the requirements for equipment are low, and it is easy to realize industrial production. Therefore, problems such as too low temperature affecting the reaction rate and too high temperature having high requirements for equipment will not occur.

[0042] In some embodiments, POF3 gas is introduced into the first mixture for reaction, and the reaction pressure is 0.01 MPa to 0.6 MPa. Specifically, it can be 0.01 MPa, 0.05 MPa, 0.1 MPa, 0.15 MPa, 0.2 MPa, 0.25 MPa, 0.3 MPa, 0.35 MPa, 0.4 MPa, 0.45 MPa, 0.5 MPa, 0.55 MPa, 0.6 MPa, etc. In some other embodiments, the reaction pressure between the organosilicate and POF3 gas can be 0.2 MPa to 0.45 MPa. Under the above pressure conditions, the reaction activity can be significantly improved, the reaction can be promoted, increasing the pressure will increase the concentration of gas molecules, reduce the distance between gas molecules, and increase the collision frequency, thereby accelerating the reaction rate, and silicon difluorophosphate can be efficiently prepared under mild conditions.

[0043] In some embodiments, POF3 gas is introduced into the first mixture for reaction, and the reaction time is 1 h to 6 h. Specifically, it can be 1 h, 2 h, 3 h, 4 h, 5 h, 6 h, etc. In some other embodiments, the reaction time between the organosilicate and POF3 gas is 2.5 h to 4 h. Within the above reaction time, the reaction can be basically ensured to proceed completely, the reaction efficiency is high, there will be no time waste, and the cost is low.

[0044] In some embodiments, when the organosilicate and POF3 gas react, the water content in the system ≤ 50 ppm. Specifically, the water content in the system can be 50 ppm, 45 ppm, 40 ppm, 35 ppm, 30 ppm, 25 ppm, 20 ppm, 15 ppm, 10 ppm, 5 ppm, 1 ppm, etc. Thus, impurities generated by the hydrolysis of silicon difluorophosphate can be effectively reduced, and silicon difluorophosphate with higher purity can be obtained.

[0045] In some embodiments, POF3 gas is introduced into the first mixture for reaction. Calculated according to the stoichiometric ratio of the reaction between the organosilicate and the POF3 gas, the POF3 gas is in an excess of 5% to 30%. Specifically, it can be 5%, 10%, 15%, 20%, 25%, 30%, etc. Calculated according to the stoichiometric ratio of the reaction between the organosilicate and the POF3 gas, the excess of the POF3 gas can be 20%. Thereby, the reaction rate can be further increased, raw materials can be saved, and the reaction cost can be reduced at the same time.

[0046] Specifically, the excess of POF3 is beneficial to the forward progress of the reaction, greatly improving the reaction efficiency, ensuring that the organosilicate in the reaction reacts completely, increasing the reaction conversion rate, and enabling the generated fluoride salt to be clean and recyclable.

[0047] In some embodiments, during the reaction between the organosilicate and the POF3 gas, the reaction process is monitored by 19F NMR spectroscopy, and the reaction is stopped after the content of the POF3 gas and / or the silicon difluorophosphate ester remains unchanged. This is beneficial to the more complete reaction between the organosilicate and the POF3 gas, will not cause waste of raw materials and time, and is conducive to improving efficiency.

[0048] In some embodiments, after the reaction between the organosilicate and the POF3 gas is completed, at least one of the following post-treatment steps is further included: Nitrogen purging to remove POF3 gas; Filtering to remove metal fluoride precipitates to obtain a filtrate; Rectifying the filtrate under the conditions of 10°C to 60°C and -0.09 MPa to 0.098 MPa.

[0049] Specifically, by nitrogen purging the mixture directly obtained after the reaction between the organosilicate and the POF3 gas, the residual POF3 gas can be removed; the generated metal fluoride precipitates are filtered off to obtain a filtrate containing silicon difluorophosphate ester, and rectification under the above conditions can separate the silicon difluorophosphate ester from the organic solvent. Through the above operations, the purity of the obtained silicon difluorophosphate ester can be effectively improved, and the yield is relatively high.

[0050] In some embodiments, after the reaction between the organosilicate and the POF3 gas is completed, the following steps are further included in sequence: nitrogen purging the mixture directly obtained after the reaction between the organosilicate and the POF3 gas; filtering the mixture after nitrogen purging; rectifying the filtrate obtained by filtration under the conditions of 10°C to 60°C and -0.09 MPa to 0.098 MPa.

[0051] It is understandable that since the product prepared in this reaction system only contains excessive POF3 and organic solvents, the above post-treatment steps can be used to remove them. This method is not only simple in operation, but also can effectively remove impurities, resulting in a high-purity and high-yield product after treatment.

[0052] In some embodiments, after the reaction is completed, nitrogen purging, filtration, and rectification are carried out in sequence. The yield of the obtained product is ≥80%. Specifically, it can be 80.0%, 85.0%, 88.0%, 90.0%, 92.0%, 95.0%, etc. Therefore, this preparation method is suitable for mass production.

[0053] In the second aspect of this application, a silicon difluorophosphate prepared by the method for preparing silicon difluorophosphate described above is proposed. This silicon difluorophosphate has high purity and few impurities. When used as an electrolyte additive, it can effectively reduce side reactions and improve the electrochemical performance of the battery.

[0054] In some embodiments, the purity of the silicon difluorophosphate is ≥99.0%. Specifically, it can be 99.0%, 99.1%, 99.2%, 99.3%, 99.4%, 99.5%, 99.6%, 99.7%, 99.8%, 99.9%, etc. Therefore, when this silicon difluorophosphate is used in a battery, there are fewer side reactions, and the electrochemical performance of the battery can be effectively improved.

[0055] The embodiments of this application will be described in detail below.

[0056] Example 1: 1. Nitrogen was introduced into the high-pressure reactor for purging to maintain an anhydrous nitrogen atmosphere. A certain mass of organosilicon alkoxide and ethyl acetate were added and stirred until dissolved and mixed evenly. The water content in the high-pressure reactor was measured to be 5 ppm. Phosphorus oxytrifluoride gas was introduced, and the reaction was carried out at a temperature of 30 °C, a pressure of 0.4 MPa, and with an excess of 20% phosphorus oxytrifluoride. 2. During the reaction between the organosilicon alkoxide and phosphorus oxytrifluoride gas, the reaction process was monitored by 19F NMR. The reaction was stopped and the pressure was released after the content of the silicon difluorophosphate remained unchanged. 3. Nitrogen was used to purge and remove the phosphorus oxytrifluoride gas, followed by filtration to remove metal fluorides. Then, the filtrate was rectified at 25 °C and -0.092 MPa to separate the organic solvent in the filtrate, obtaining the product silicon difluorophosphate.

[0057] Examples 2 - 50 The method is the same as that of Example 1, and the specific parameter differences are shown in Table 1.

[0058] Comparative Example 1 To a 200 mL eggplant-shaped flask containing a magnetic stir bar, chlorotrimethylsilane (48.7 g, 448 mmol, manufactured by TCI) as a silicon compound was added, and then difluorophosphoric acid (45.7 g, 448 mmol) as a phosphoric acid compound was added dropwise at room temperature. The mixed solution was stirred at 50 °C for 6 hours under a nitrogen stream. Trimethylsilyl difluorophosphate, a colorless liquid as a phosphate ester, was obtained by atmospheric distillation of the reaction mixture (49.0 g, yield 62.7%). The purity of trimethylsilyl difluorophosphate was 95.6%.

[0059] Performance testing: 1. Structure test of silicon difluorophosphate ester: The structure of the product was tested by nuclear magnetic resonance.

[0060] 2. Product purity and yield test: It was determined by gas chromatography (GC method). Specifically, acetonitrile was used as the solvent, the tester was an Agilent 7890B gas chromatograph equipped with an FID detector, the gas chromatography column was Restek® RTX-65, the inlet temperature was 120 °C, the detector temperature was 150 °C, the column temperature programming was (initial 50 °C, hold for 1 min, rise to 120 °C at 5 °C / min, hold for 1 min), and the column flow rate was 1 mL / min. The test results are shown in Table 1.

[0061] Table 1

[0062] From the above test results, it can be seen that by reacting organosilicate with POF3 gas to prepare silicon difluorophosphate ester, the reaction rate is fast, the reaction conditions are mild, the reaction time is short and the reaction yield is high (yield ≥ 80%), the product purity is high, and the generated fluoride salt can be recycled, with a relatively high atom utilization rate.

[0063] In the description of this specification, the descriptions with reference to terms such as "one embodiment", "some embodiments", "example", "specific example", or "some examples" mean that the specific features, structures, materials, or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described can be combined in a suitable manner in any one or more embodiments or examples. In addition, without contradiction, those skilled in the art can combine and combine the different embodiments or examples described in this specification and the features of different embodiments or examples.

[0064] Although the embodiments of the present invention have been shown and described above, it can be understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those of ordinary skill in the art can make changes, modifications, substitutions, and variations to the above embodiments within the scope of the present invention.

Claims

1. A method for preparing silicon difluorophosphate ester, characterized in that, Comprising: Under the conditions of a pressure of 0.01 MPa to 0.6 MPa and a temperature of 5 °C to 80 °C, reacting an organosilicon alkoxide shown by Formula I with POF3 gas to obtain a silicon difluorophosphate shown by Formula II; Formula I Formula II Wherein, each of R1, R2, and R3 independently comprises any one of C1-C6 alkyl, C2-C6 alkenyl, C2-C6 alkynyl, and substituted or unsubstituted phenyl; M comprises any one of lithium, sodium, and potassium; Calculated according to the stoichiometric ratio of the reaction between the organosilicon alkoxide and the POF3 gas, the POF3 gas is in excess by 5% to 30%.

2. The method according to claim 1, characterized in that, The reaction between the organosilicon alkoxide and the POF3 gas comprises: Mixing the organosilicon alkoxide and an organic solvent to obtain a first mixture; Introducing the POF3 gas into the first mixture.

3. The method according to claim 1, wherein The reaction between the organosilicon alkoxide and the POF3 gas satisfies at least one of the following conditions: The temperature of the reaction is 20 °C to 40 °C; The pressure of the reaction is 0.2 MPa to 0.45 MPa; The time of the reaction is 1 h to 6 h.

4. The method according to claim 1, wherein Under the condition that the water content ≤ 50 ppm, reacting the organosilicon alkoxide with the POF3 gas.

5. The method according to claim 1, wherein Calculated according to the stoichiometric ratio of the reaction between the organosilicon alkoxide and the POF3 gas, the POF3 gas is in excess by 20%.

6. The method according to claim 2, wherein The mass ratio of the organosilicon alkoxide to the organic solvent is 1:2 to 1:

8.

7. The method according to claim 2, wherein The organic solvent comprises at least one of dichloromethane, dichloroethane, ethyl acetate, acetonitrile, diethyl ether, ethylene glycol dimethyl ether, and dimethyl carbonate.

8. The method according to claim 1, characterized in that During the reaction between the organosilicon alkoxide and the POF3 gas, monitoring the reaction process by 19F NMR, and stopping the reaction after the content of the POF3 gas and / or the silicon difluorophosphate remains unchanged.

9. The method according to any one of claims 1 to 8, characterized in that, After the reaction between the organosilicon alkoxide and the POF3 gas is completed, it further comprises at least one of the following steps: Purging with nitrogen to remove the POF3 gas; Filtering to remove metal fluoride precipitate to obtain a filtrate; Rectifying the filtrate under the conditions of 10 °C to 60 °C and -0.09 MPa to 0.098 MPa.

10. The method according to any one of claims 1 to 8, characterized in that, Each of R1, R2, and R3 independently comprises any one of methyl and ethyl.

11. The method according to claim 10, wherein The organosilicate includes , , and at least one of lithium triethylsilanolate, sodium triethylsilanolate, and potassium triethylsilanolate; The silicon difluorophosphate ester includes and at least one of them.

12. A silicon difluorophosphate ester, characterized in that, Prepared by the method according to any one of claims 1 to 11.

13. The silicon difluorophosphate according to claim 12, wherein The purity of the silicon difluorophosphate ≥ 99.0%.

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