Hexafluorophosphate, phosphorus pentafluoride, a method for preparing the same, and uses thereof

Abstract

This application discloses hexafluorophosphate, phosphorus pentafluoride, and its preparation method and use. This application does not use phosphorus pentafluoride as raw material to prepare hexafluorophosphate, and does not use hydrogen fluoride as raw material to produce phosphorus pentafluoride, reducing the safety risk of production, and uses chemical reagents such as diphosphorus pentaoxide and sulfur trioxide, which have a wide supply source, as raw materials, reducing raw material costs and favoring industrial large-scale production. [Means] The method for preparing the hexafluorophosphate comprises mixing a phosphoric acid solution of diphosphorus pentoxide with sulfur trioxide and a fluoride in an inert gas atmosphere, and after the reaction, sequentially carrying out evaporation concentration, dissolution, filtration and drying to obtain the hexafluorophosphate. The method for preparing the phosphorus pentafluoride using the hexafluorophosphate obtained by the preparation method of the present application comprises mixing the hexafluorophosphate with a catalyst solution, and after the catalytic reaction, sequentially carrying out condensation, pressurization liquefaction and removal of impurities by adsorption to obtain the phosphorus pentafluoride.

Description

[Technical field]

[0001] The present application relates to the technical field of electrolyte additives for lithium-ion batteries, such as hexafluorophosphate, phosphorus pentafluoride, its preparation method and use. [Background technology]

[0002] As a new type of mobile power source, lithium ion batteries have higher specific capacity and discharge voltage than traditional lead-acid batteries and alkaline batteries, and are less polluting to the environment. At present, lithium ion batteries are widely used as batteries for mobile power sources and mobile phones, and as power batteries for electric vehicles, automobiles, etc. With the strong support of national policies and the accumulation of lithium ion battery technology in recent years, the lithium ion battery industry has made great progress, and with policy encouragement and technological progress, it is bound to experience sustained development.

[0003] Hexafluorophosphate and phosphorus pentafluoride are important raw materials in the field of lithium-ion batteries, and the requirements for their yield and quality are increasing day by day. At present, the methods for preparing hexafluorophosphate mainly include gas-solid reaction method, hydrogen fluoride solvent method, organic solvent method and ion exchange method. Usually, phosphorus pentafluoride needs to be used as a raw material, but phosphorus pentafluoride is toxic and easily decomposes and reacts with moisture in the environment to produce hydrogen fluoride, which is toxic and corrosive.

[0004] CN113353958A discloses a clean production process for hexafluorophosphate, which includes the steps of: reacting phosphorus pentafluoride with anhydrous hydrofluoric acid or hydrogen fluoride gas to prepare phosphorus pentafluoride; adsorbing the gas mixture obtained after the reaction with lithium fluoride; obtaining purified phosphorus pentafluoride gas after desorption; and further adsorbing and separating the unadsorbed hydrogen chloride and hydrogen fluoride gases by temperature and pressure swing to obtain hydrogen chloride gas and hydrogen fluoride gas, respectively; and for preparing hexafluorophosphate, the steps of reacting the obtained purified phosphorus pentafluoride with a lithium source or a sodium source to prepare hexafluorophosphate, and reusing the hydrogen fluoride separated in the step (1) as a raw material in the preparation step of phosphorus pentafluoride (step (3)).

[0005] CN105776168A discloses a method for preparing hexafluorophosphate, which includes the steps of: (1) gradually adding phosphorus trichloride and anhydrous hydrogen fluoride in excess of phosphorus trichloride to a gas-liquid mixer in a ratio of 50-60°C to generate phosphorus trifluoride and hydrogen chloride; (2) continuously introducing the phosphorus trifluoride, hydrogen chloride and excess hydrogen fluoride gas generated in (1) into a phosphorus pentafluoride reaction generator, and (3) continuously introducing chlorine gas into the phosphorus pentafluoride reaction generator. The method includes the steps of: (1) continuously introducing phosphorus pentafluoride gas into a fluoride salt at −10 to −30° C., maintaining the reaction system in a dry environment at 35 to 70° C., and continuously reacting phosphorus trifluoride, chlorine gas, and hydrogen fluoride gas in the reactor to generate phosphorus pentafluoride gas; and (2) introducing phosphorus pentafluoride gas into a fluoride salt at −10 to −30° C., reacting the salt to generate hexafluorophosphate, crystallizing the salt at −20 to −30° C. for 2 to 4 hours, concentrating, and drying to obtain a hexafluorophosphate product. Both of the above two methods use phosphorus pentafluoride as a raw material, and produce hydrogen fluoride that is toxic and corrosive, which places great demands on devices and processes.

[0006] Phosphorus pentafluoride (PF 5 PF is a colorless gas with a pungent odor at room temperature and pressure, with a melting point of -93.8°C and a boiling point of -84.6°C. 5is easily hydrolyzed when it comes into contact with water and alkali, emits strong smoke in wet air, does not corrode glass in dry conditions, can form complexes with amines, ethyl ethers, nitrates, sulfoxides, etc., and is expensive and difficult to obtain. In related technology, phosphorus pentafluoride is usually synthesized by reacting phosphorus pentachloride and anhydrous hydrogen fluoride as raw materials, but this reaction is very exothermic, has a low yield, and produces a by-product PF 3 Cl 2 It is prone to producing impurities.

[0007] CN104261369A discloses a method for preparing high-purity phosphorus pentafluoride, which includes step I of preparing an aqueous hexafluorophosphoric acid solution using polyphosphoric acid and anhydrous hydrogen fluoride as starting materials, step II of reacting the aqueous hexafluorophosphoric acid solution prepared in step I with sulfur trioxide to obtain a mixture of hexafluorophosphoric acid and sulfuric acid, step III of directly heating the mixture of hexafluorophosphoric acid and sulfuric acid obtained in step II without separation, condensing the generated phosphorus pentafluoride vapor to obtain crude phosphorus pentafluoride, and step IV of purifying the crude phosphorus pentafluoride to obtain high-purity phosphorus pentafluoride with a purity of >99.5%. Since hydrogen fluoride gas is used as the raw material, the raw material is expensive, and hydrogen fluoride gas is highly corrosive, which easily damages the reaction vessel and piping, etc., and the requirements for corrosion resistance and high-pressure sealing of the device are high, and the process is relatively complicated.

[0008] CN101353161A discloses a method for preparing phosphorus pentafluoride gas and a method for preparing lithium hexafluorophosphate with the gas, in which phosphorus pentafluoride is prepared by reacting phosphorus pentafluoride with anhydrous hydrogen fluoride in the presence of a solvent such as ether, acetonitrile, carbonate, or ethyl acetate, and lithium hexafluorophosphate is prepared by contacting solid lithium fluoride with phosphorus pentafluoride gas. Since hydrogen fluoride gas is used as the raw material, the raw material is expensive and highly corrosive, and such a reaction has a high heat dissipation, a low yield, and a by-product PF 3 Cl 2 It is prone to producing impurities.

[0009] Therefore, providing a green and safe method for preparing hexafluorophosphate and phosphorus pentafluoride has already become one of the urgent problems in the field. Summary of the Invention [Problem to be solved by the invention]

[0010] The following is a brief summary of the subject matter described in greater detail in the present text. This summary does not limit the scope of the claims.

[0011] The embodiment of the present application provides hexafluorophosphate, phosphorus pentafluoride, its preparation method and use, wherein in the preparation process of hexafluorophosphate, it is not necessary to use phosphorus pentafluoride as raw material, and it is also possible to avoid using hydrogen fluoride as raw material to produce phosphorus pentafluoride, thereby reducing the safety risk of production, and the supply source of raw materials is wide, reducing raw material cost, which is favorable for industrial large-scale production. [Means for solving the problem]

[0012] In aspect 1, the present application provides a method for preparing a hexafluorophosphate salt, comprising the steps of: (1) mixing a phosphoric acid solution of diphosphorus pentoxide with sulfur trioxide and a fluoride in an inert gas atmosphere to obtain a hexafluorophosphate precursor after reaction; and (2) sequentially subjecting the hexafluorophosphate precursor obtained in step (1) to evaporation, dissolution, filtration and drying to obtain the hexafluorophosphate. A method for preparing a hexafluorophosphate salt is provided.

[0013] The preparation method of hexafluorophosphate according to the present application uses diphosphorus pentaoxide and sulfur trioxide as raw materials, which have a wide supply source and low cost, which is favorable for industrial large-scale production.In addition, the preparation method avoids using phosphorus pentafluoride and hydrogen fluoride as raw materials, which reduces the safety risk of production.

[0014] In the present invention, the phosphoric acid solution of diphosphorus pentoxide, sulfur trioxide and fluoride are mixed in a reaction vessel having a water content of less than 10 ppm, and the mixing includes the steps of first adding phosphoric acid at room temperature, gradually adding diphosphorus pentoxide to the phosphoric acid, stirring to dissolve, and then dripping sulfur trioxide liquid, controlling the temperature of the system, gradually adding fluoride after dripping, mixing uniformly and stirring, and then closing the reaction vessel.

[0015] Preferably, the phosphoric acid solution of diphosphorus pentoxide described in step (1) is a mixture of diphosphorus pentoxide and phosphoric acid.

[0016] Preferably, the molar ratio of diphosphorus pentoxide to phosphoric acid is 1:(0.01 to 1.0), and may be, for example, 1:0.01, 1:0.1, 1:0.2, 1:0.3, 1:0.4, 1:0.5, 1:0.6, 1:0.7, 1:0.8, 1:0.9, or 1:1.0, but is not limited to the recited numerical values ​​and other unrecited numerical values ​​within the numerical range are also applicable, and it is more preferable that the molar ratio is 1:(0.1 to 1.0).

[0017] Preferably, the molar ratio of the diphosphorus pentoxide to the sulfur trioxide described in step (1) to the fluoride ions in the fluoride is 1:(5.0-10.0):(12.0-24.0), and may be, for example, 1:5.0:12.0, 1:10.0:24.0, 1:8.0:18.0, 1:7.5:19.5, or 1:6.0:20.0, but is not limited to the recited numerical values, and other unrecited numerical values ​​within the numerical range also apply.

[0018] Preferably, the fluoride described in step (1) comprises a combination of at least one of an alkali metal ion-containing fluoride, an alkaline earth metal ion-containing fluoride, a transition metal-containing fluoride, and an ammonium ion-containing fluoride. Typical combinations include, but are not limited to, a combination of an alkali metal ion-containing fluoride and an alkaline earth metal ion-containing fluoride, a combination of a transition metal-containing fluoride and an ammonium ion-containing fluoride, or a combination of an alkali metal ion-containing fluoride, an alkaline earth metal ion-containing fluoride, and a transition metal-containing fluoride.

[0019] Preferably, the fluoride described in step (1) includes a combination of at least one of potassium fluoride, lithium fluoride, sodium fluoride, rubidium fluoride, cesium fluoride, magnesium fluoride, calcium fluoride, or barium fluoride, and typical combinations include, but are not limited to, a combination of potassium fluoride and lithium fluoride, a combination of potassium fluoride and sodium fluoride, a combination of lithium fluoride and calcium fluoride, a combination of lithium fluoride and magnesium fluoride, or a combination of potassium fluoride and magnesium fluoride.

[0020] As a preferred technical solution of the present application, the fluoride described in step (1) of the present application includes any one or a combination of at least two of potassium fluoride, lithium fluoride, sodium fluoride, or magnesium fluoride, and typical combinations include, but are not limited to, a combination of potassium fluoride and lithium fluoride, a combination of potassium fluoride and sodium fluoride, a combination of potassium fluoride and magnesium fluoride, a combination of lithium fluoride, sodium fluoride and magnesium fluoride, or a combination of potassium fluoride, lithium fluoride, sodium fluoride and magnesium fluoride.

[0021] Preferably, the reaction temperature of the reaction described in step (1) is 60.0 to 150.0°C, and may be, for example, 60.0°C, 80.0°C, 100.0°C, 120.0°C, 140.0°C, or 150.0°C, but is not limited to the recited numerical values, and other numerical values ​​not recited within the numerical range also apply, and is more preferably 60.0 to 120.0°C.

[0022] Preferably, the reaction time of the reaction described in step (1) is 10.0 to 15.0 h, and may be, for example, 10.0 h, 11.0 h, 12.0 h, 13.0 h, 14.0 h, or 15.0 h, but is not limited to the recited values, and other unrecited values ​​within the numerical range also apply.

[0023] The inert gas described in step (1) of the present application includes any one or a combination of at least two of nitrogen gas, argon gas, helium gas, or neon gas.

[0024] The concentration and evaporation described in step (2) of the present application may be performed sufficiently at normal pressure or at reduced pressure, for example, at a pressure of 0.01 to 0.05 MPa. The temperature of the concentration and evaporation is not particularly limited as long as the desired concentration effect can be obtained and the target product is not decomposed to generate unnecessary impurities, and may be, for example, 80.0 to 100.0° C. By the evaporation and concentration, phosphoric acid as a solvent and excess sulfur trioxide can be evaporated and removed.

[0025] Preferably, the solvent used in the dissolution process described in step (2) comprises ethanol or acetone.

[0026] The dissolution process described in step (2) of the present application can remove poorly soluble sulfates and fluorides by adding ethanol or acetone to dissolve thoroughly and then filtering. Hexafluorophosphate can be dissolved in ethanol or acetone and is mostly dissolved in the filtrate. To further increase the purity, dissolution and filtering operations can be performed twice or more times.

[0027] The temperature and time for drying described in step (2) of the present application are not particularly limited as long as the desired drying effect can be obtained and the target product is not decomposed to generate unnecessary impurities. For example, drying may be performed sufficiently at 80.0 to 100.0°C.

[0028] As a preferred technical solution of the preparation method described in aspect 1 of the present application, the preparation method comprises: Step (1) of mixing a phosphoric acid solution of diphosphorus pentoxide with sulfur trioxide and a fluoride in an inert gas atmosphere, and reacting at a temperature of 60.0 to 150.0°C for 10.0 to 15.0 hours to obtain a hexafluorophosphate precursor, the phosphoric acid solution of diphosphorus pentoxide being a mixture of diphosphorus pentoxide and phosphoric acid, the molar ratio of diphosphorus pentoxide to phosphoric acid being 1:(0.01 to 1.0), and the molar ratio of diphosphorus pentoxide to sulfur trioxide described in step (1) to fluorine ions in the fluoride being 1:(5.0 to 10.0):(12.0 to 24.0); and (2) evaporating and concentrating the hexafluorophosphate precursor obtained in step (1) at a temperature of 80.0 to 100.0°C, dissolving it in ethanol or acetone and filtering it to obtain a filtrate, drying the filtrate at a temperature of 80.0 to 100.0°C, and then obtaining the hexafluorophosphate.

[0029] In a second aspect, the present application provides a hexafluorophosphate salt prepared by the preparation method described in the first aspect.

[0030] The hexafluorophosphate salt according to the present application is a white powder.

[0031] In an embodiment 3, the present application provides a use of the hexafluorophosphate salt prepared by the preparation method according to the embodiment 1, the hexafluorophosphate salt being used as an electrolyte additive for lithium ion batteries.

[0032] In a fourth aspect, the present application provides a method for preparing phosphorus pentafluoride, comprising the steps of: (a) mixing a hexafluorophosphate salt with a catalyst solution to carry out a catalytic reaction and then obtaining crude phosphorus pentafluoride gas; and (b) sequentially subjecting the crude phosphorus pentafluoride gas obtained in step (a) to condensation, pressurization and removal of impurities by adsorption, and then obtaining the phosphorus pentafluoride, The hexafluorophosphate salt according to step (1) is the hexafluorophosphate salt according to claim 6. A method for preparing phosphorus pentafluoride is provided.

[0033] In the present invention, high-purity phosphorus pentafluoride is obtained by removing high-boiling impurities by condensation. The high-boiling impurities include any one or a combination of at least two of sulfur trioxide, sulfur dioxide, phosphoryl fluoride, hydrogen fluoride, and phosphoric acid vapor. These have a higher boiling point than phosphorus pentafluoride and belong to the high-boiling impurities.

[0034] Preferably, the catalyst described in step (a) comprises a combination of one or at least two of sulfuric acid, sulfur trioxide, a solution of sulfur trioxide in sulfuric acid, a solution of diphosphorus pentoxide in sulfuric acid, a solution of sulfur trioxide in phosphoric acid, or a crown ether, and typical combinations include, but are not limited to, a combination of sulfuric acid and sulfur trioxide, a combination of sulfur trioxide and a solution of sulfur trioxide in sulfuric acid, a solution of diphosphorus pentoxide in sulfuric acid, and a solution of sulfur trioxide in phosphoric acid, or a combination of sulfuric acid and a crown ether.

[0035] More preferably, the catalyst described in step (a) comprises any one or a combination of at least two of sulfuric acid, sulfur trioxide, or a solution of sulfur trioxide in sulfuric acid, and typical combinations include, but are not limited to, a combination of sulfuric acid and sulfur trioxide, a combination of sulfuric acid and a solution of sulfur trioxide in sulfuric acid, a combination of sulfur trioxide and a solution of sulfur trioxide in sulfuric acid, or a combination of sulfuric acid, sulfur trioxide, and a solution of sulfur trioxide in sulfuric acid.

[0036] Preferably, the crown ether comprises any one or at least two of 12-crown-4-ether, 15-crown-5-ether, or 18-crown-6-ether, and typical combinations include, but are not limited to, 12-crown-4-ether and 15-crown-5-ether, 15-crown-5-ether and 18-crown-6-ether, 12-crown-4-ether and 18-crown-6-ether, or 12-crown-4-ether, 15-crown-5-ether and 18-crown-6-ether.

[0037] Preferably, the temperature of the catalytic reaction described in step (a) is 150-400°C, for example, it may be 150°C, 200°C, 250°C, 300°C, 350°C, or 400°C, but is not limited to the recited values, and other unrecited values ​​within the numerical range apply as well.

[0038] The molar ratio of the hexafluorophosphate to the catalyst solution described in step (a) is 1:(5.0-20.0), and may be, for example, 1:5.0, 1:8.0, 1:10.0, 1:12.0, 1:14.0, 1:16.0, 1:18.0, or 1:20.0, but is not limited to the recited numerical values, and other unrecited numerical values ​​within the numerical range also apply, and is more preferably 1:(10.0-15.0).

[0039] The molar ratio of the hexafluorophosphate salt and the catalyst solution according to the present application is not particularly limited as long as the corresponding catalytic effect can be obtained.

[0040] Preferably, the duration of the catalytic reaction described in step (a) is 8-12 h, for example, it may be 8 h, 9 h, 10 h, 11 h, or 12 h, but is not limited to the recited values, and other unrecited values ​​within the numerical range also apply.

[0041] Preferably, the condensation pressure described in step (b) is 0.1-0.2 MPa, for example, 0.1 MPa, 0.12 MPa, 0.14 MPa, 0.16 MPa, 0.18 MPa, or 0.2 MPa, but is not limited to the recited values, and other unrecited values ​​within the numerical range apply as well.

[0042] Preferably, the temperature of condensation in step (b) is −50 to −40° C., e.g., −50° C., −48° C., −46° C., −44° C., −42° C., or −40° C., but is not limited to the recited values, and other unrecited values ​​within the numerical range also apply.

[0043] Preferably, the pressure in the pressurized liquefaction process described in step (b) is 0.6 to 1.0 MPa, and may be, for example, 0.6 MPa, 0.7 MPa, 0.8 MPa, 0.9 MPa, or 1.0 MPa, but is not limited to the recited numerical values, and other numerical values ​​not recited within the numerical range also apply, and is more preferably 0.6 to 0.8 MPa.

[0044] Preferably, the adsorbent employed in the process of removing impurities by adsorption described in step (b) comprises any one or a combination of at least two of alkali metal ion-containing fluorides, alkaline earth metal ion-containing fluorides, or ammonium ion-containing fluorides, and typical combinations include, but are not limited to, a combination of an alkali metal ion-containing fluoride and an alkaline earth metal ion-containing fluoride, a combination of a transition metal ion-containing fluoride and an ammonium ion-containing fluoride, or a combination of an alkali metal ion-containing fluoride, an alkaline earth metal ion-containing fluoride and a transition metal ion-containing fluoride.

[0045] Preferably, the adsorbent comprises any one or a combination of at least two of potassium fluoride, lithium fluoride, sodium fluoride, rubidium fluoride, cesium fluoride, magnesium fluoride, calcium fluoride, or barium fluoride, and more preferably, the adsorbent comprises any one or a combination of at least two of potassium fluoride, lithium fluoride, or magnesium fluoride.

[0046] The adsorbent according to the present application can remove impurities by adsorption, for example, small amounts of hydrogen fluoride that may remain.

[0047] In a fifth aspect, the present application provides phosphorus pentafluoride prepared by the preparation method described in the third aspect.

[0048] Preferably, the purity of the phosphorus pentafluoride is ≧99.9%, and may be, for example, 99.9%, 99.91%, 99.92%, 99.93%, 99.94%, 99.96%, or 99.98%, but is not limited to the recited values, and other unrecited values ​​within the numerical range also apply.

[0049] The purity of the phosphorus pentafluoride of the present invention is ≧99.9%, in which the content of anhydrous hydrogen fluoride is ≦10 ppm, the content of water is ≦10 ppm, and the content of metal ions is ≦5 ppm.

[0050] In a sixth aspect, the present application provides a use of phosphorus pentafluoride prepared by the preparation method according to the fourth aspect, the phosphorus pentafluoride being used for preparing a phosphate-based electrolyte additive, such as lithium hexafluorophosphate or lithium difluorophosphate, for lithium ion batteries.

[0051] As a preferred technical solution of the present application, the method for preparing phosphorus pentafluoride according to the present application comprises: Step (1) of mixing a phosphoric acid solution of diphosphorus pentoxide with sulfur trioxide and a fluoride in an inert gas atmosphere, and reacting at a temperature of 60.0 to 150.0°C for 10.0 to 15.0 hours to obtain a hexafluorophosphate precursor, the phosphoric acid solution of diphosphorus pentoxide being a mixture of diphosphorus pentoxide and phosphoric acid, the molar ratio of diphosphorus pentoxide to phosphoric acid being 1:(0.01 to 1.0), and the molar ratio of diphosphorus pentoxide to sulfur trioxide described in step (1) to fluorine ions in the fluoride being 1:(5.0 to 10.0):(12.0 to 24.0); Step (2) of evaporating and concentrating the hexafluorophosphate precursor obtained in step (1) at a temperature of 80.0 to 100.0°C, dissolving it in ethanol or acetone, filtering the resulting filtrate, and drying the filtrate at a temperature of 80.0 to 100.0°C to obtain the hexafluorophosphate; Step (3) of mixing hexafluorophosphate with a catalyst solution and carrying out a catalytic reaction at 150 to 400°C to obtain crude phosphorus pentafluoride, the molar ratio of the hexafluorophosphate to the catalyst solution being 1:(5.0 to 20.0); and step (4) of condensing the crude phosphorus pentafluoride gas obtained in step (3) at a temperature of -50 to -40°C under a pressure of 0.1 to 0.2 MPa, pressurizing and liquefying it at a pressure of 0.6 to 1.0 MPa, and then adsorbing it with an adsorbent to remove impurities, thereby obtaining the phosphorus pentafluoride.

[0052] The numerical ranges referred to in this application include not only the recited point values ​​but also any point values ​​between the recited numerical ranges that are not recited, and for the sake of space and clarity, this application does not exhaustively recite specific point values ​​included in the ranges. Effect of the Invention

[0053] Compared with the related art, the beneficial effects of the embodiments of the present application are as follows:

[0054] (1) The raw materials used in the method for preparing hexafluorophosphate according to the embodiments of the present application do not contain phosphorus pentafluoride, and the preparation of phosphorus pentafluoride using hydrogen fluoride as a raw material is avoided, thereby reducing safety risks during production.

[0055] (2) The method for preparing hexafluorophosphate in the embodiment of the present application uses diphosphorus pentoxide and sulfur trioxide as raw materials, which are inexpensive and widely available, thereby reducing the production cost and being favorable for industrial production.

[0056] (3) The methods for preparing hexafluorophosphate and phosphorus pentafluoride according to the embodiments of the present application have mild reactions, high conversion rates, low amounts of impurities, and easy process control.

[0057] Other aspects may be understood upon reading and understanding the detailed description. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0058] The technical solution of the present application will be further described below by means of specific embodiments. Those skilled in the art will appreciate that the above examples are merely for the purpose of understanding the present application, and should not be regarded as specific limitations of the present application.

[0059] The sources of some of the components in the following examples and comparative examples are as follows: Diphosphorus pentoxide and potassium chloride were purchased from Shanghai Macklin Biochemical CO., LTD., sulfur trioxide was purchased from Quzhou Hemao Chemical Industry Co., Ltd., hexafluorophosphate was purchased from Shanghai Macklin, and solvents such as phosphoric acid and sulfuric acid were purchased from the Aladdin reagent site.

[0060] The raw materials or reagents used in the examples and comparative examples of this application were all purchased from mainstream manufacturers in the market, and those without a specified manufacturer or concentration were all commonly available raw materials or reagents of analytical purity (Analytical Reagent), and are not particularly limited as long as they can perform the intended function. The reactors and rotary evaporators and other instrumental devices used in this example were all purchased from major manufacturers in the market, and are not particularly limited as long as they can perform the intended function. Those without a specified specific technique or condition in this example were performed according to the technique or condition described in the literature in this field, or according to the product instructions. EXAMPLES

[0061] This embodiment provides hexafluorophosphate and phosphorus pentafluoride, and a method for preparing the hexafluorophosphate and phosphorus pentafluoride includes the following steps:

[0062] Step (1) A phosphoric acid solution of 1.1 mol of diphosphorus pentoxide, 0.5 mol of sulfur trioxide, and 1.2 mol of potassium fluoride were mixed in a nitrogen gas atmosphere, and reacted at a temperature of 120.0°C for 10.0 hours to obtain a potassium hexafluorophosphate precursor. The phosphoric acid solution of diphosphorus pentoxide was a mixture of diphosphorus pentoxide and phosphoric acid, and the molar ratio of diphosphorus pentoxide to phosphoric acid was 0.1:1.0.

[0063] Step (2) The potassium hexafluorophosphate precursor obtained in step (1) was evaporated and concentrated at a temperature of 100.0°C to remove the phosphoric acid solvent and the like, and a solid powder mixture was precipitated. The mixture was then dissolved in 5.0 mol of ethanol and filtered to obtain a filtrate. The produced potassium sulfate and insoluble solid powders such as potassium fluoride that may remain were removed, and the filtrate was dried at a temperature of 100.0°C to obtain 0.181 mol of the potassium hexafluorophosphate.

[0064] Step (3) 0.1 mol of the potassium hexafluorophosphate obtained in step (2) was mixed with 1.0 mol of sulfuric acid, and a catalytic reaction was carried out at 150.0° C. for 12 hours to obtain crude phosphorus pentafluoride gas.

[0065] Step (4) The crude phosphorus pentafluoride gas obtained in step (3) is condensed at a temperature of -50°C under a pressure of 0.1 MPa to condense and remove high-boiling point impurity gases into a liquid. The gas after the impurities have been removed by condensation is pressurized and liquefied at a pressure of 0.6 MPa, and then adsorbed with potassium fluoride to remove impurities and remove small amounts of hydrogen fluoride contained therein, thereby obtaining high-purity phosphorus pentafluoride.

[0066] Using the preparation method described in this example, 0.181 mol of potassium hexafluorophosphate was prepared, the yield of the potassium hexafluorophosphate was 90.5%, and the purity of the potassium hexafluorophosphate was 99.90%.

[0067] The purity of phosphorus pentafluoride prepared by the method described in this example was 99.96%. EXAMPLES

[0068] This embodiment provides hexafluorophosphate and phosphorus pentafluoride, and a method for preparing the hexafluorophosphate and phosphorus pentafluoride includes the following steps:

[0069] Step (1) A phosphoric acid solution of 0.2 mol of diphosphorus pentoxide, 1.0 mol of sulfur trioxide, and 2.4 mol of lithium fluoride were mixed in an argon gas atmosphere, and reacted at a temperature of 60.0°C for 15.0 hours to obtain a lithium hexafluorophosphate precursor. The phosphoric acid solution of diphosphorus pentoxide was a mixture of diphosphorus pentoxide and phosphoric acid, and the molar ratio of diphosphorus pentoxide to phosphoric acid was 1.0:1.0.

[0070] Step (2) The lithium hexafluorophosphate precursor obtained in step (1) was evaporated and concentrated at a temperature of 80.0°C to remove the phosphoric acid solvent and excess sulfur trioxide, etc., to precipitate a solid powder mixture, which was then dissolved in 8.0 mol of acetone and filtered to obtain a filtrate, and the produced lithium sulfate and remaining insoluble solid powders such as lithium fluoride were removed. The filtrate was then dried at a temperature of 80.0°C, and 0.186 mol of the lithium hexafluorophosphate was obtained.

[0071] Step (3): 0.1 mol of the lithium hexafluorophosphate obtained in step (2) was mixed with 1.0 mol of a sulfuric acid solution of sulfur trioxide, and a catalytic reaction was carried out at 400°C for 8 hours to obtain crude phosphorus pentafluoride gas. The molar concentration of the sulfuric acid solution of sulfur trioxide was 20 mol%.

[0072] Step (4) The crude phosphorus pentafluoride gas obtained in step (3) was condensed at a temperature of -40°C under a pressure of 0.2 MPa, and then pressurized and liquefied at a pressure of 1.0 MPa. Impurities were then removed by adsorption with lithium fluoride to obtain high-purity phosphorus pentafluoride.

[0073] Using the preparation method described in this example, 0.186 mol of lithium hexafluorophosphate was prepared, the yield of the lithium hexafluorophosphate was 93.0%, and the purity of the lithium hexafluorophosphate was 99.92%.

[0074] The purity of phosphorus pentafluoride prepared by the method described in this example was 99.98%. EXAMPLES

[0075] This embodiment provides hexafluorophosphate and phosphorus pentafluoride, and a method for preparing the hexafluorophosphate and phosphorus pentafluoride includes the following steps:

[0076] Step (1) A phosphoric acid solution of 1.1 mol of diphosphorus pentoxide, 0.75 mol of sulfur trioxide, and 1.8 mol of magnesium fluoride were mixed in a nitrogen gas atmosphere, and reacted at a temperature of 90.0°C for 12.0 hours to obtain a magnesium hexafluorophosphate precursor. The phosphoric acid solution of diphosphorus pentoxide was a mixture of diphosphorus pentoxide and phosphoric acid, and the molar ratio of diphosphorus pentoxide to phosphoric acid was 0.1:1.0.

[0077] Step (2) The magnesium hexafluorophosphate precursor obtained in step (1) was evaporated and concentrated at a temperature of 90.0°C to remove the phosphoric acid solvent, sulfur trioxide, etc., to precipitate a solid powder mixture, which was then dissolved in 8.0 mol of acetone and filtered to obtain a filtrate, from which insoluble solid powders such as magnesium sulfate and magnesium fluoride were removed, and the filtrate was dried at a temperature of 90.0°C to obtain 0.091 mol of the magnesium hexafluorophosphate.

[0078] Step (3) 0.05 mol of magnesium hexafluorophosphate and 1.0 mol of sulfur trioxide in sulfuric acid were mixed, and the catalytic reaction was carried out at 300.0°C for 10.0 hours to obtain crude phosphorus pentafluoride gas. The molar concentration of the sulfur trioxide in sulfuric acid solution was 20 mol%.

[0079] Step (4) The crude phosphorus pentafluoride gas obtained in step (3) was condensed at a temperature of -45°C under a pressure of 0.15 MPa, pressurized and liquefied at a pressure of 0.8 MPa, and then adsorbed with an adsorbent to remove impurities, thereby obtaining high-purity phosphorus pentafluoride.

[0080] Using the preparation method described in this example, 0.091 mol of magnesium hexafluorophosphate was prepared, the yield of the magnesium hexafluorophosphate was 91.0%, and the purity of the magnesium hexafluorophosphate was 99.91%.

[0081] The purity of phosphorus pentafluoride prepared by the method described in this example was 99.98%. EXAMPLES

[0082] This example provides hexafluorophosphate and phosphorus pentafluoride, and the preparation methods of the hexafluorophosphate and phosphorus pentafluoride are the same as those of Example 1, except that potassium fluoride in step (1) is replaced with sodium fluoride. EXAMPLES

[0083] This example provides hexafluorophosphate and phosphorus pentafluoride, and the preparation method of said hexafluorophosphate and phosphorus pentafluoride is the same as that of Example 1, except that the catalyst solution in step (3) is replaced with a mixture of 1.0 mol of 20 mol% sulfur trioxide in sulfuric acid and 0.5 mol of 12-crown-4-ether. Comparative Example 1

[0084] This comparative example provides hexafluorophosphate and phosphorus pentafluoride, and the preparation methods of the hexafluorophosphate and phosphorus pentafluoride are the same as those of Example 1, except that the molar amount of sulfur trioxide in step (1) is replaced by 2.0 mol.

[0085] This comparative example provides hexafluorophosphate and phosphorus pentafluoride, and the preparation methods of the hexafluorophosphate and phosphorus pentafluoride are the same as those of Example 1, except that the reaction temperature in step (1) is changed to 30.0°C.

[0086] This comparative example provides hexafluorophosphate and phosphorus pentafluoride, and the preparation method of the hexafluorophosphate and phosphorus pentafluoride is the same as that of Example 1, except that the reaction temperature described in step (1) is changed to 160.0°C. Product performance detection was performed on the hexafluorophosphates according to Examples 1 to 5 and Comparative Examples 1 to 3. The purity was detected using a Metrohm930 ion chromatograph, the free acid (HF) content was detected using a Metrohm888 potentiometric titrator, the moisture content in the product was detected according to the Karl Fischer method using a Metrohm compact oven (885)-moisture meter (917) combined device, and the impurity metal ion content in the product was detected using an inductively coupled plasma optical emission spectroscope (ICP-OES). The obtained detection results are shown in Table 1.

[0087] [Table 1]

[0088] The phosphorus pentafluoride according to Examples 1 to 5 and Comparative Examples 1 to 3 was subjected to detection of product performance. The purity of phosphorus pentafluoride was detected using liquid chromatography and a Fourier transform infrared spectrometer, the free acid (HF) content was detected using a Metrohm 888 potentiometric titrator, the moisture content in the product was detected according to the Karl Fischer method using a Metrohm compact oven (885)-moisture meter (917) combination device, and the impurity metal ion content in the product was detected using an inductively coupled plasma optical emission spectrometer (ICP-OES). The obtained detection results are shown in Table 2.

[0089] [Table 2]

[0090] As can be seen from Tables 1 and 2, the yield of hexafluorophosphate in Examples 1 to 5 of the present application was higher than 90%, and the purity was clearly superior to that of the Comparative Example, with the free acid content being 12 ppm or less, the moisture content being 10 ppm or less, and the impurity metal content being 33 ppm or less. The purity of phosphorus pentafluoride in Examples 1 to 5 of the present application was high, and superior to that of the Comparative Example, with a purity of 99.95% or more, a free acid content being 10 ppm or less, a moisture content being 10 ppm or less, and an impurity content being 5 ppm.

[0091] Comparing Examples 1 to 5 with Comparative Example 1, the amount of sulfur trioxide in step (1) in Comparative Example 1 was excessive and exceeded the preferred range of the present application, resulting in a decrease in the purity of the hexafluorophosphate, an increase in the free acid content, an increase in the water content, and a decrease in the purity of phosphorus pentafluoride.

[0092] Comparing Examples 1 to 5 with Comparative Example 2, the reaction temperature in step (1) in Comparative Example 2 was too low, lower than the preferred range of the present application, and as a result, the reaction was incomplete, a large amount of unreacted material remained, the yield and purity of the hexafluorophosphate were significantly reduced, the free acid content was increased, and the water content was also increased, and the purity of phosphorus pentafluoride was significantly reduced, and the free acid content and water content were increased.

[0093] As can be seen from Tables 1 and 2, comparing Examples 1 to 5 with Comparative Example 3, the reaction temperature in step (1) in Comparative Example 2 was too high, higher than the preferred range of the present application, resulting in excessive reaction and the generation of by-products, as well as a significant decrease in the purity of hexafluorophosphate, a significant increase in the free acid content, and an increase in the impurity metal ion content, a significant decrease in the purity of phosphorus pentafluoride, a significant increase in the free acid content, and an increase in the moisture content and impurity metal ion content.

[0094] In summary, the present application adopts a new technical solution, uses diphosphorus pentaoxide, sulfur trioxide and fluoride as raw materials, and precisely controls the molar ratio and reaction conditions of the reaction, thereby obtaining unexpectedly good yield and purity. The present application does not use phosphorus pentafluoride as raw material to prepare hexafluorophosphate, and also avoids using hydrogen fluoride as raw material to produce phosphorus pentafluoride, greatly reducing the safety risk of production, providing a new production process, and has a wide range of raw material sources, reduced raw material costs, high yield and purity, and low impurity content, which is favorable for industrial large-scale production.

[0095] The above specific examples further explain the objectives, technical solutions and beneficial effects of the present application in detail. It should be understood that the above are only specific examples of the present application and do not limit the present application. Any modifications, equivalent replacements and improvements made within the spirit and principle of the present application should be included within the protection scope of the present invention.

Claims

1. 1. A process for preparing a hexafluorophosphate salt comprising the steps of: (1) mixing a phosphoric acid solution of diphosphorus pentoxide with sulfur trioxide and a fluoride in an inert gas atmosphere to obtain a hexafluorophosphate precursor after reaction; and (2) sequentially subjecting the hexafluorophosphate precursor obtained in step (1) to evaporation, dissolution, filtration and drying to obtain the hexafluorophosphate. Method for preparing hexafluorophosphate salts.

2. The phosphoric acid solution of diphosphorus pentoxide described in step (1) is a mixture of diphosphorus pentoxide and phosphoric acid, The molar ratio of diphosphorus pentoxide to phosphoric acid is 1: (0.01 to 1.0); 2. The method of claim 1.

3. The molar ratio of the diphosphorus pentoxide to the sulfur trioxide in step (1) to the fluorine ions in the fluoride is 1:(5.0-10.0):(12.0-24.0); The fluoride described in step (1) includes any one or a combination of at least two of an alkali metal ion fluoride, an alkaline earth metal ion-containing fluoride, a transition metal-containing fluoride, or an ammonium ion-containing fluoride; The fluoride described in step (1) includes any one or a combination of at least two of potassium fluoride, lithium fluoride, sodium fluoride, rubidium fluoride, cesium fluoride, magnesium fluoride, calcium fluoride, and barium fluoride; The reaction temperature of the reaction described in step (1) is 60.0 to 150.0° C.; The solvent used in the dissolution process described in step (2) comprises ethanol or acetone; The preparation method according to claim 2.

4. Step (1) of mixing a phosphoric acid solution of diphosphorus pentoxide with sulfur trioxide and a fluoride in an inert gas atmosphere, and reacting at a temperature of 60.0 to 150.0°C for 10.0 to 15.0 hours to obtain a hexafluorophosphate precursor, the phosphoric acid solution of diphosphorus pentoxide being a mixture of diphosphorus pentoxide and phosphoric acid, the molar ratio of diphosphorus pentoxide to phosphoric acid being 1:(0.01 to 1.0), and the molar ratio of diphosphorus pentoxide to sulfur trioxide and fluorine ions in the fluoride according to step (1) being 1:(5.0 to 10.0):(12.0 to 24.0); and (2) evaporating and concentrating the hexafluorophosphate precursor obtained in step (1) at a temperature of 80.0 to 100.0°C, dissolving it in ethanol or acetone, filtering the resulting filtrate, and drying the filtrate at a temperature of 80.0 to 100.0°C to obtain the hexafluorophosphate.

2. The method of claim 1.

5. Obtained by the process according to any one of claims 1 to 4, Hexafluorophosphate salts.

6. The hexafluorophosphate salt is used as an electrolyte additive for lithium ion batteries. Use of the hexafluorophosphate salt according to claim 5.

7. 1. A method for preparing phosphorus pentafluoride, comprising the steps of: (a) mixing a hexafluorophosphate salt with a catalyst solution to carry out a catalytic reaction and then obtaining crude phosphorus pentafluoride gas; and (b) sequentially subjecting the phosphorus pentafluoride crude gas obtained in step (a) to condensation, pressurization and removal of impurities by adsorption, and then obtaining the phosphorus pentafluoride, The hexafluorophosphate salt according to step (1) is the hexafluorophosphate salt according to claim 6. Method for preparing phosphorus pentafluoride.

8. The catalyst described in step (a) comprises any one or a combination of at least two of sulfuric acid, sulfur trioxide, a solution of sulfur trioxide in sulfuric acid, a solution of diphosphorus pentaoxide in sulfuric acid, a solution of sulfur trioxide in phosphoric acid, or a crown ether; The crown ether includes any one or a combination of at least two of 12-crown-4-ether, 15-crown-5-ether, or 18-crown-6-ether; The temperature of the catalytic reaction described in step (a) is 150 to 400° C.; The molar ratio of the hexafluorophosphate salt to the catalyst solution in step (a) is 1:(5.0-20.0); The pressure of the condensation described in step (b) is 0.1 to 0.2 MPa; The temperature of the condensation described in step (b) is −50 to −40° C. The pressure in the pressurized liquefaction process described in step (b) is 0.6 to 1.0 MPa; The adsorbent used in the adsorption impurity removal process described in step (b) comprises any one or a combination of at least two of an alkali metal ion-containing fluoride, an alkaline earth metal ion-containing fluoride, or an ammonium ion-containing fluoride; The preparation method according to claim 7.

9. Phosphorus pentafluoride, The phosphorus pentafluoride is obtained by the preparation process according to claim 7 or 8, The purity of the phosphorus pentafluoride is ≧99.9%; Phosphorus pentafluoride.

10. The phosphorus pentafluoride is used in the preparation of lithium hexafluorophosphate or lithium difluorophosphate for lithium ion batteries. Use of phosphorus pentafluoride according to claim 9.