Difluorobis(oxalato)phosphate composition, and preparation method therefor and use thereof

Abstract

The present invention relates to the technical field of battery electrolyte additives, and in particular to a difluorobis(oxalato)phosphate composition, and a preparation method therefor and a use thereof. The chemical formula of the composition is: MPF2(C2O4)2·xB, wherein M is an alkali metal, B is an organic solvent, X is a molar ratio, and 0.05<x<1.1. The difluorobis(oxalato)phosphate composition obtained by the present invention has good fluidity and is more suitable for being fed in the process of preparing an electrolyte. Compared with difluorobis(oxalato)phosphate, the yield and product quality of the prepared difluorobis(oxalato)phosphate composition are higher, and the content of impurities in the prepared composition is low.

Description

Difluorobisoxalate phosphate composition, preparation method and application thereof Technical Field

[0001] The present invention relates to the technical field of battery electrolyte additives, and in particular to a difluorobis(oxaloyl)phosphate composition, a preparation method and application thereof. Background Art

[0002] Common difluorobis(oxaloyl)phosphates include lithium difluorobis(oxaloyl)phosphate and sodium difluorobis(oxaloyl)phosphate. Lithium difluorobis(oxaloyl)phosphate (LiDFOP) is generally used as an additive for non-aqueous electrolyte batteries such as lithium-ion batteries or lithium-ion capacitors. After adding this additive, the electrolyte has excellent high-temperature resistance and can form a more stable solid electrolyte interface film structure on the surface of the positive electrode material, thereby improving the cycle performance of the battery. Sodium difluorobis(oxaloyl)phosphate is an important additive for sodium-ion battery electrolytes and has the following advantages: easy dissociation, which makes the electrolyte have better conductivity; good antioxidant, thermal stability and chemical stability; and certain reduction stability. Due to the above advantages, difluorobis(oxaloyl)phosphate has a good application prospect in batteries.

[0003] The preparation technology of more lithium difluorobis(oxalate)phosphates has been reported in the prior art. Japanese Patent JP2010143835A discloses a method for preparing lithium difluorobis(oxalate)phosphate solution by lithium hexafluorophosphate, silicon tetrachloride and oxalic acid. The method is rapid in reaction and easy to obtain with cheap raw materials, but silicon tetrachloride is introduced into the raw materials, which easily causes the chloride ion content in the final product to exceed the standard. Meanwhile, since the product exists in the form of a solution, unreacted oxalic acid is difficult to remove, resulting in a higher acidity of the product. Korean Patent KR101395663B1 discloses a method for preparing lithium difluorobis(oxalate)phosphate by reacting lithium hexafluorophosphate with oxalic acid di(trialkylsilyl)ester, which has mild reaction conditions, is free of chloride ion introduction, and the product is easy to purify. However, the raw materials of the method are not easy to obtain, have poor economic benefits, and have low raw material activity and a long reaction time. What is obtained is a mixture of lithium difluorobis(oxalate)phosphate and lithium tetrafluorobis(oxalate)phosphate. Chinese patent CN108910919A discloses a method for preparing lithium difluorobis(oxalate)phosphate using hexamethyldisilazane, oxalic acid and lithium hexafluorophosphate as raw materials. The shortcoming of this reaction is that an equivalent amount of ammonia is generated, and its attack product and then reacts a side reaction. Disclosed in CN110845539A is lithium hexafluorophosphate and ammonium oxalate as raw materials, and a mixed solution of lithium hexafluorophosphate and ammonium oxalate is prepared in an aprotic organic solvent. Under the condition of not introducing other substances, a method for directly reacting to obtain a lithium difluorobis(oxalate)phosphate solution is obtained. This method also has the problem of side reactions occurring in ammonium substances, raw materials and products, and the product purity is not high, and the method is not practical. As can be seen, in actual industrial applications, in addition to seeking low cost and high yield, the purity and performance of the product are increasingly being paid attention to. The purification method of conventional lithium difluorobis(oxalate)phosphate is recrystallization, and the wet product of lithium difluorobis(oxalate)phosphate is often obtained after recrystallization, and then the solvent is removed by high-temperature drying. The lithium difluorobis(oxaloyl)phosphate product obtained by high-temperature drying has no crystalline form. The poor fluidity of the solid powder during the preparation of the electrolyte makes it difficult to feed the material. Furthermore, the yield and purity are difficult to achieve satisfactory results.

[0004] Summary of the Invention

[0005] In view of the above-mentioned shortcomings of the prior art, the first object of the present invention is to provide a composition of difluorobis(oxalyl)phosphate, the chemical formula of which is: MPF2(C2O4)2·xB, wherein M is an alkali metal, B is an organic solvent, and x is a molar ratio, 0.05<x<1.1.

[0006] The second object of the present invention is to provide a method for preparing a difluorobisoxalate phosphate composition, the method comprising: obtaining a mixed solution containing difluorobisoxalate phosphate and an organic solvent, adding a poor solvent for crystallization, filtering to obtain a filter cake, and drying to obtain the difluorobisoxalate phosphate composition.

[0007] The third object of the present invention is to provide use of a difluorobis(oxaloyl)phosphate composition in an electrolyte.

[0008] A fourth object of the present invention is to provide use of the difluorobisoxalophosphate composition in a battery.

[0009] Compared with the prior art, the present invention has the following beneficial effects:

[0010] The difluorobisoxalate phosphate composition obtained by the present invention has good fluidity and is more suitable for feeding in the process of preparing an electrolyte; compared with obtaining difluorobisoxalate phosphate, the preparation of the difluorobisoxalate phosphate composition has a higher yield and product quality, and the impurity content in the obtained composition is low. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] FIG1 is a fluorine spectrum of the product LiPF2(C2O4)2·xDMC, x=1.002, prepared in Example 6;

[0012] FIG2 is a hydrogen spectrum of the product LiPF2(C2O4)2·xDMC, x=1.002 prepared in Example 6;

[0013] FIG3 is a carbon spectrum of the product LiPF2(C2O4)2·xDMC, x=1.002 prepared in Example 6;

[0014] FIG4 is a fluorine spectrum of the product LiPF2(C2O4)2·xEC, x=1.074 prepared in Example 3;

[0015] FIG5 is a hydrogen spectrum of the product LiPF2(C2O4)2·xEC, x=1.074 prepared in Example 3;

[0016] FIG6 is a carbon spectrum of the product LiPF2(C2O4)2·xEC, x=1.074 prepared in Example 3;

[0017] FIG7 is a fluorine spectrum of the product LiPF2(C2O4)2·0.501DMC·0.510EC, x=1.011, prepared in Example 9;

[0018] FIG8 is a hydrogen spectrum of the product LiPF2(C2O4)2·0.501DMC·0.510EC, x=1.011, prepared in Example 9;

[0019] FIG9 is a carbon spectrum of the product LiPF2(C2O4)2·0.501DMC·0.510EC, x=1.011, prepared in Example 9;

[0020] Figure 10 is a fluorine spectrum of the product NaPF2(C2O4)2·0.889DMC·0.102EC, x=0.991, prepared in Example 10;

[0021] FIG11 is a hydrogen spectrum of the product NaPF2(C2O4)2·0.889DMC·0.102EC, x=0.991, prepared in Example 10;

[0022] Figure 12 is a carbon spectrum of the product NaPF2(C2O4)2·0.889DMC·0.102EC, x=0.991, prepared in Example 10;

[0023] FIG13 is a fluorine spectrum of the product LiPF2(C2O4)2·0.112DMC·1.002EC, x=1.114, prepared in Example 11;

[0024] FIG14 is a hydrogen spectrum of the product LiPF2(C2O4)2·0.112DMC·1.002EC, x=1.114, prepared in Example 11;

[0025] FIG15 is a carbon spectrum of the product LiPF2(C2O4)2·0.112DMC·1.002EC, x=1.114, prepared in Example 11. DETAILED DESCRIPTION

[0026] The following detailed description specifically discloses the embodiments of the difluorobis(oxalate)phosphate composition, its preparation method, and its application. However, unnecessary detailed descriptions may be omitted. For example, detailed descriptions of well-known matters and repeated descriptions of actual identical structures may be omitted. This is to avoid the following description from becoming unnecessarily lengthy and to facilitate understanding by those skilled in the art. In addition, the drawings and the following description are provided to enable those skilled in the art to fully understand the present application and are not intended to limit the subject matter described in the claims.

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

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

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

[0030] Unless otherwise specified, the terms "include" and "comprising" used in this application may be open-ended or closed-ended. For example, "include" and "comprising" may mean that other components not listed may also be included or that only the listed components are included.

[0031] The inventors of the present invention have, after extensive research, provided a composition of difluorobisoxalate phosphate and its preparation method, as well as its use in electrolytes and batteries. The composition of difluorobisoxalate phosphate of the present application is obtained by first obtaining a mixed solution containing difluorobisoxalate phosphate and an organic solvent, adding a poor solvent for crystallization, filtering to obtain a filter cake, and drying to obtain the composition of the difluorobisoxalate phosphate obtained. Compared to difluorobisoxalate phosphate solids, the composition has good fluidity, higher yield and product quality, and the impurity content in the obtained composition is low. On this basis, the present application has been completed.

[0032] Compositions of difluorobisoxalophosphate

[0033] The present invention provides a difluorobis(oxaloyl)phosphate composition having the chemical formula: MPF2(C2O4)2·xB. The composition is an organic solvent crystal of difluorobis(oxaloyl)phosphate, obtained by cooling and crystallizing difluorobis(oxaloyl)phosphate and an organic solution, and then drying the resulting filter cake under certain conditions.

[0034] In the chemical formula of the composition of the present invention, M is an alkali metal, preferably, M is Li or Na.

[0035] In the chemical formula of the composition of the present invention, B is an organic solvent. Optionally, B is selected from one or more of dimethyl carbonate and ethylene carbonate. Preferably, B is selected from dimethyl carbonate (DMC) or ethylene carbonate (EC).

[0036] In the chemical formula of the composition of the present invention, x represents a molar ratio, and 0.05 < x < 1.1. Alternatively, 0.5 ≤ x ≤ 1, 0.05 < x < 0.1, 0.1 < x < 0.5, 0.5 < x < 0.8, 0.8 < x < 1.1, 0.1 < x < 0.2, 0.2 < x < 0.3, 0.3 < x < 0.4, 0.4 < x < 0.5, 0.5 < x < 0.6, 0.6 < x < 0.7, 0.7 < x < 0.8, 0.8 < x < 0.9, 0.9 < x < 1.0, or 1.0 < x < 1.1, etc. Preferably, 0.5 ≤ x ≤ 1, and particularly preferably, x = 1, is used for the best purity and yield. When x = 1, the composition is a crystalline complex, in which the metal compound MPF2(C2O4)2 and the solvent are chemically bonded together to form a defined crystal form. When x ≠ 1, the composition contains the complex and free solvent molecules, or the complex and difluorobis(oxaloyl)phosphate. As described elsewhere in this invention, when x is greater than 1, the composition contains the complex MPF2(C2O4)2·EC / DMC and free solvent molecules. When x is less than 1, the final product should contain both the complex MPF2(C2O4)2·EC / DMC and MPF2(C2O4)2. The value of x in this invention can be controlled by reaction conditions. Specific control methods are described in the preparation method section below.

[0037] As one embodiment of the present invention, the chemical formula of the composition of the present invention is MPF2(C2O4)2·x(DMC / EC), wherein M is Li or Na, DMC is dimethyl carbonate, EC is ethylene carbonate, and x is a molar ratio, 0.05<x<1.1. Alternatively, 0.5≤x≤1, 0.05<x<0.1, 0.1<x<0.5, 0.5<x<0.8, 0.8<x<1.1, 0.1<x<0.2, 0.2<x<0.3, 0.3<x<0.4, 0.4<x<0.5, 0.5<x<0.6, 0.6<x<0.7, 0.7<x<0.8, 0.8<x<0.9, 0.9<x<1.0, or 1.0<x<1.1, etc. Preferably, 0.5≤x≤1, and particularly preferably, x=1.

[0038] As an embodiment of the present invention, the chemical formula of the composition of the present invention can be any one of the following:

[0039] LiPF2(C2O4)2·x(DMC / EC), NaPF2(C2O4)2·x(DMC / EC). DMC is dimethyl carbonate, and EC is ethylene carbonate. DMC or EC can act as a single ligand to complex with difluorobis(oxalyl)phosphate, or both can act as dual ligands to complex with difluorobis(oxalyl)phosphate simultaneously.

[0040] x is a molar ratio, x is the total molar ratio of DMC and EC, 0.05<x<1.1; alternatively, 0.3<x<1.1; alternatively, 0.5≤x≤1, 0.05<x<0.1, 0.1<x<0.5, 0.5<x<0.8, 0.8<x<1.1, 0.1<x<0.2, 0.2<x<0.3, 0.3<x<0.4, 0.4<x<0.5, 0.5<x<0.6, 0.6<x<0.7, 0.7<x<0.8, 0.8<x<0.9, 0.9<x<1.0, or 1.0<x<1.1, etc. Preferably, 0.5≤x≤1, and x=1 is particularly preferred.

[0041] As an embodiment of the present invention, the chemical formula of the composition of the present invention can be any one of the following:

[0042] MPF2(C2O4)2·1.0DMC·0.1EC, MPF2(C2O4)2·0.9DMC·0.1EC, MPF2(C2O4)2·0.8DMC·0.1EC, MPF2(C2O4)2·0.8DMC·0.2EC, MPF2(C2O4)2· 0.7DMC·0.2EC, MPF2(C2O4)2·0.6DMC·0.2EC, MPF2(C2O4)2·0.6DMC·0.3EC, MPF2(C2O4)2·0.5DMC·0.3EC, MPF2(C2O4)2·0.5DMC·0.4EC, MPF2(C2O4)2·0.4DMC·0.4EC, MPF2(C2O4)2·0.4DMC·0.5EC, MPF2(C2O4)2·0.5DMC·0.5EC, MPF2(C2O4)2·0.4DMC·0.3EC, MPF2(C 2O4)2·0.4DMC·0.2EC, MPF2(C2O4)2·0.5DMC·0.5EC, MPF2(C2O4)2·0.3DMC·0.5EC, MPF2(C2O4)2·0.3DMC·0.6EC, MPF2(C2O4)2·0 .3DMC·0.7EC, MPF2(C2O4)2·0.2DMC·0.3EC, MPF2(C2O4)2·0.2DMC·0.5EC, MPF2(C2O4)2·0.2DMC·0.7EC, MPF2(C2O4)2·0.2DMC·0.8EC, MPF2(C2O4)2·0.1DMC·0.1EC, MPF2(C2O4)2·0.1DMC·0.5EC, MPF2(C2O4)2·0.1DMC·0.7EC, MPF2(C2O4)2·0.1DMC·0.9EC, etc. M is Li or Na.

[0043] As an embodiment of the present invention, the chemical formula of the composition of the present invention can be any one of the following:

[0044] LiPF2(C2O4)2·xDMC, LiPF2(C2O4)2·xEC, NaPF2(C2O4)2·xDMC, or NaPF2(C2O4)2·xEC.

[0045] Wherein, DMC is dimethyl carbonate, EC is ethylene carbonate, x is a molar ratio, 0.05<x<1.1; alternatively, 0.3<x<1.1; alternatively, 0.5≤x≤1, 0.05<x<0.1, 0.1<x<0.5, 0.5<x<0.8, 0.8<x<1.1, 0.1<x<0.2, 0.2<x<0.3, 0.3<x<0.4, 0.4<x<0.5, 0.5<x<0.6, 0.6<x<0.7, 0.7<x<0.8, 0.8<x<0.9, 0.9<x<1.0 or 1.0<x<1.1, etc. Preferably, 0.5≤x≤1, particularly preferably x=1, with the best purity and yield.

[0046] Preparation method of difluorobis(oxaloyl)phosphate composition

[0047] The present invention also provides a method for preparing a difluorobisoxalate phosphate composition, which comprises: obtaining a mixed solution containing difluorobisoxalate phosphate and an organic solvent, adding a poor solvent for crystallization, filtering to obtain a filter cake, and drying to obtain the difluorobisoxalate phosphate composition.

[0048] In the preparation method provided by the present invention, the mixed solution containing difluorobis(oxaloyl)phosphate and an organic solvent can be obtained by various methods. The following methods are used as examples, for example:

[0049] Method 1: A mixed solution containing difluorobisoxalophosphate and an organic solvent is prepared by preparing difluorobisoxalophosphate and an organic solvent. As one embodiment of Method 1 of the present invention, for example, difluorobisoxalophosphate and an organic solvent are refluxed and dissolved at a certain temperature, and then hot filtered to remove mechanical impurities to obtain a mixed solution. The temperature can be, for example, 60°C to 100°C.

[0050] Method 2: A mixed solution containing difluorobisoxalophosphate and an organic solvent is obtained during the preparation of difluorobisoxalophosphate. As an embodiment of Method 2 of the present invention, for example, hexafluorophosphate and anhydrous oxalic acid solid are added to an organic solvent, silicon tetrachloride or a solution prepared by silicon tetrachloride and an organic solvent is added dropwise after heating, and the mixture is stirred while maintaining the temperature. During this period, silicon tetrafluoride gas and hydrogen chloride are generated. 19 FNMR analysis indicates complete reaction of the hexafluorophosphate in the reaction solution. The reaction solution is cooled to room temperature, filtered to remove trace insoluble matter, and the filtrate is concentrated under reduced pressure. Alternatively, the filtrate is concentrated under reduced pressure to a viscous, translucent solid-liquid mixture. An organic solvent is added and heated until the solid-liquid mixture becomes clear.

[0051] In the second method of the present invention, the heating temperature can be, for example, 20°C to 70°C; the dropwise addition time can be 1 to 12 hours; the holding temperature can be 20°C to 70°C; and the holding time can be 3 to 6 hours. The hexafluorophosphate salt can be, for example, lithium hexafluorophosphate or sodium hexafluorophosphate. The temperature for concentrating the filtrate under reduced pressure can be, for example, 20°C to 80°C.

[0052] The molar ratio of silicon tetrachloride to hexafluorophosphate is 1:1-1.1, and the molar ratio of anhydrous oxalic acid to hexafluorophosphate is 2:1-1.1.

[0053] In the preparation method provided by the present invention, in the mixed solution containing difluorobisoxalophosphate and an organic solvent, the mass ratio of the organic solvent to the difluorobisoxalophosphate is 1:1-5. Alternatively, the mass ratio of the organic solvent to the difluorobisoxalophosphate can be, for example, 1:1-1.67, 1:1.67-5, 1:1-3, 1:3-5, 1:1-2, 1:2-3, 1:3-4, or 1:4-5. Too little organic solvent results in insufficient dissolution, while too much increases costs and is uneconomical.

[0054] In the preparation method provided by the present invention, the mass ratio of the difluorobisoxalate phosphate to the poor solvent is 1:1 to 10. Alternatively, the mass ratio of the difluorobisoxalate phosphate to the poor solvent can be, for example, 1:1 to 5, 1:5 to 10, 1:1 to 3, 1:3 to 5, 1:5 to 8, 1:8 to 10, 1:1 to 2, 1:2 to 3, 1:3 to 4, 1:4 to 5, 1:5 to 6, 1:6 to 7, 1:7 to 8, 1:8 to 9, 1:9 to 10, etc. Too little poor solvent affects the yield and incomplete precipitation of the product. Too much poor solvent affects the product quality and introduces new impurities.

[0055] In the preparation method provided by the present invention, the difluorobisoxalate phosphate is selected from lithium difluorobisoxalate phosphate or sodium lithium difluorobisoxalate phosphate.

[0056] In the preparation method provided by the present invention, the organic solvent is selected from one or more of dimethyl carbonate, ethylene carbonate, and other solvents. The organic solvent here is a good solvent, and dimethyl carbonate or ethylene carbonate must be present in the good solvent, but other good solvents may be present, but the precipitated solid composition will only carry two solvents, dimethyl carbonate and ethylene carbonate. Wherein, the other solvents are selected from one or more of ethyl methyl carbonate, diethyl carbonate, propylene carbonate, acetonitrile, tetrahydrofuran, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, and dioxane. Preferably, the organic solvent is selected from dimethyl carbonate and / or ethylene carbonate. In the present invention, if only other solvents are selected, a solid composition cannot be obtained, or the composition is unstable. The product obtained by the present invention can be stably present at room temperature and pressure and is easy to store. For example, if ethyl methyl carbonate is selected as a solvent, although a composition can be obtained, ethyl methyl carbonate is volatile and the product gradually loses weight, affecting quality and storage.

[0057] In the preparation method provided by the present invention, the poor solvent is a hydrocarbon solvent and / or a halogenated hydrocarbon solvent. Optionally, the poor solvent is a mixed solvent of one or more of benzene, toluene, o-xylene, m-xylene, p-xylene, chlorobenzene, o-dichlorobenzene, m-dichlorobenzene, p-dichlorobenzene, hexane, heptane, octane, dichloromethane, chloroform, carbon tetrachloride, 1,2-dichloroethane, 1,1-dichloroethane, 1,1,2-trichloroethane, tetrachloroethane, tetrachloroethylene, 1,2,3-trichloropropane, n-butyl ether, and isopropyl ether.

[0058] Optionally, the hydrocarbon solvent is selected from one or more of n-hexane, cyclohexane, n-heptane, n-octane, petroleum ether, toluene, and xylene. Preferably, the hydrocarbon solvent is selected from one or more of petroleum ether, n-hexane, toluene, and o-xylene.

[0059] Optionally, the halogenated hydrocarbon solvent is selected from a combination of one or more of dichloromethane, chloroform, 1,2-dichloroethane, 1,1,1-trichloroethane, 1,1,2-trichloroethane, 1,2,3-trichloropropane, 1,1,2,2-tetrachloroethane, 1,4-dichlorobutane, and 1,1,2,2-tetrachloroethylene. Preferably, the halogenated hydrocarbon solvent is selected from one or more of 1,4-dichlorobutane, 1,2,3-trichloropropane, and 1,2-dichloroethane. Reference points for selecting a poor solvent include: economical price, environmental protection, inherent stability, no introduction of impurities, easy recovery and separation, and guaranteed precipitation yield.

[0060] In the preparation method provided by the present invention, when the poor solvent is added dropwise, the mixture is stirred and crystallized while stirring. The stirring time affects the rate of crystallization and is the most important factor affecting the x value in the final product. The appropriate stirring time is 1-12h. In the initial stage of stirring, a large amount of crystals are precipitated. As the stirring time is prolonged, the solvent is redissolved in the crystal lattice and complexed with the metal compound at a suitable crystallization temperature. If the stirring time is too short, the crystals precipitate too quickly, and part of the solvent is dissolved in the crystal lattice, which is easy to escape during the subsequent drying and heating process. In addition to the stirring time, the crystallization temperature also affects the composition of the composition. If the temperature is too low, the crystals precipitate quickly. In addition to impurities, there is also ethylene carbonate with a melting point of 35-38°C, which becomes a solid phase at low temperatures. The temperature range of crystallization is 10°C to 75°C. Optionally, the crystallization temperature range is 10° C. to 45° C., 45° C. to 50° C., 50° C. to 75° C., 45° C. to 70° C., 70° C. to 75° C., 45° C. to 60° C., 60° C. to 75° C., 45° C. to 55° C., 55° C. to 65° C., or 65° C. to 75° C. In order to save energy, crystallization is generally performed at a low temperature as much as possible. However, if the temperature is too low, impurities will precipitate, affecting the purity of the product.

[0061] In the preparation method provided by the present invention, the drying is carried out in a conventional manner by heating under vacuum, in an inert gas atmosphere with a moisture content of less than 10 ppm, and any conventional drying method can be used.

[0062] Furthermore, the temperature of the heating under vacuum is 20°C to 90°C. Optionally, the temperature of the heating under vacuum can be, for example, 20°C to 50°C, 50°C to 90°C, 20°C to 70°C, 70°C to 90°C, 20°C to 30°C, 30°C to 50°C or 50°C to 90°C. Preferably, the temperature of the heating under vacuum is 30°C to 50°C. The heating temperature cannot be too high, as solvent molecules are likely to escape at high temperatures. Even if a partially complexed metal composition is obtained in the early stage, or some solvent remains in the lattice, continued drying at high temperature will cause the solvent molecules to volatilize, and ultimately only a solvent-free metal compound MPF2(C2O4)2 can be obtained.

[0063] Further, the pressure of the heating under vacuum is 0 Pa to 20,000 Pa. Optionally, the pressure of the heating under vacuum is 0 Pa to 10,000 Pa, 10,000 Pa to 20,000 Pa, 0 Pa to 5,000 Pa, 5,000 Pa to 10,000 Pa, 10,000 Pa to 15,000 Pa, 15,000 Pa to 20,000 Pa, 0 Pa to 200 Pa, 200 Pa to 5000 Pa, 200 Pa to 10,000 Pa, 200 Pa to 20,000 Pa, 0 Pa to 500 Pa, 500 Pa to 5000 Pa, 500 Pa to 10,000 Pa or 500 Pa to 20,000 Pa, etc.

[0064] application

[0065] The present invention also provides use of the aforementioned difluorobisoxalophosphate composition in electrolytes and batteries.

[0066] As one embodiment of the present invention, any of the above-described lithium difluorobisoxalate phosphate compositions or those prepared according to the above description can be used to prepare an additive for an electrolyte of an electrochemical device, etc. Such an electrolyte additive can be prepared using any of a variety of methods, for example, by mixing any of the lithium difluorobisoxalate phosphate compositions disclosed herein with one or more solvents, one or more diluents, and / or one or more additives. The solvents, diluents, and additives can be known in the art, or can simply be pure one or more lithium difluorobisoxalate phosphate compositions.

[0067] The beneficial effects of the present invention are further illustrated below with reference to the examples.

[0068] In order to make the invention objectives, technical solutions and beneficial technical effects of the present invention clearer, the present invention is further described in detail below with reference to the examples. However, it should be understood that the examples of the present invention are only for the purpose of explaining the present invention and are not intended to limit the present invention, and the examples of the present invention are not limited to the examples given in the specification. In the examples, where no specific experimental conditions or operating conditions are specified, the products were prepared under conventional conditions or under the conditions recommended by the material supplier.

[0069] Furthermore, it should be understood that the one or more method steps mentioned in the present invention do not exclude the presence of other method steps before or after the combination step, or the insertion of other method steps between these explicitly mentioned steps, unless otherwise specified. It should also be understood that the combination connection relationship between one or more devices / apparatuses mentioned in the present invention does not exclude the presence of other devices / apparatuses before or after the combination device / apparatus, or the insertion of other devices / apparatuses between two explicitly mentioned devices / apparatuses, unless otherwise specified. Furthermore, unless otherwise specified, the numbering of each method step is merely a convenient tool for identifying each method step, and is not intended to limit the order of arrangement of each method step or to define the scope of the present invention. Changes or adjustments to their relative relationships, without substantially changing the technical content, should also be considered within the scope of the present invention.

[0070] In the following examples, all reagents, materials and instruments used are commercially available unless otherwise specified.

[0071] Unless otherwise specified, the solvent used in the present invention needs to have a water content of 0.05% or less.

[0072] Preparation Example 1:

[0073] 500 g of lithium difluorobis(oxaloyl)phosphate with an ion chromatography purity of 99% was added to 500 g of dimethyl carbonate, and the mixture was heated to 90° C. and refluxed to dissolve the mixture. The solution was then hot filtered to remove mechanical impurities and obtained.

[0074] Preparation Example 2:

[0075] 500 g of sodium difluorobis(oxaloyl)phosphate with 99% purity by ion chromatography was added to a mixed solvent of 200 g of ethylene carbonate and 100 g of acetonitrile, the mixture was heated to 60° C. and refluxed to dissolve, and the solution was obtained after hot filtration to remove mechanical impurities.

[0076] Preparation Example 3:

[0077] At room temperature, add 76.7 g (0.505 mol) of solid lithium hexafluorophosphate and 90.05 g (1.0 mol) of anhydrous oxalic acid to 1000 g of ethyl methyl carbonate. Heat to 45°C, and begin dropwise addition of 84.95 g (0.5 mol) of liquid silicon tetrachloride. Continue the addition over 2 hours, then maintain the temperature at 45-55°C with stirring for 4 hours. During this time, silicon tetrafluoride and hydrogen chloride gases are generated. 19 FNMR analysis indicated complete reaction of the lithium hexafluorophosphate in the reaction solution. The reaction solution was cooled to room temperature and filtered to remove trace insoluble matter. The filtrate was concentrated under reduced pressure at 50°C to a viscous, translucent solid-liquid mixture. 80 g of ethylene carbonate was added and heated at 90°C until the solid-liquid mixture dissolved.

[0078] Preparation Example 4:

[0079] At room temperature, add 152g (1.0 mol) of solid lithium hexafluorophosphate and 180.1g (2.0 mol) of anhydrous oxalic acid to 1000g of dimethyl carbonate. Heat to 50°C, and begin dropwise addition of a solution prepared by adding 169.9g (1 mol) of liquid silicon tetrachloride and 500g of dimethyl carbonate. Continue the addition over 5 hours, then maintain the temperature at 40-50°C with stirring for 6 hours. During this time, silicon tetrafluoride and hydrogen chloride gas are generated. 19 FNMR analysis indicated that the lithium hexafluorophosphate in the reaction solution had completely reacted. The reaction solution was cooled to room temperature and filtered to remove trace insoluble matter. The filtrate was concentrated under reduced pressure at 80°C to a viscous, translucent solid-liquid mixture.

[0080] Preparation Example 5:

[0081] At room temperature, 168 g (1.0 mol) of solid sodium hexafluorophosphate and 180.1 g (2.0 mol) of anhydrous oxalic acid were added to a mixed solvent of 600 g of dimethyl carbonate and 500 g of ethylene glycol dimethyl ether. The mixture was heated to 50°C, and a solution prepared by adding 169.9 g (1 mol) of liquid silicon tetrachloride and 500 g of dimethyl carbonate was added dropwise. The addition was continued for 5 hours, followed by stirring at 40-50°C for 6 hours, during which time silicon tetrafluoride and hydrogen chloride gas were generated. 19 FNMR analysis indicated that the sodium hexafluorophosphate in the reaction solution had completely reacted. The reaction solution was cooled to room temperature and filtered to remove trace insoluble matter. The filtrate was concentrated under reduced pressure at 80°C to a viscous, translucent solid-liquid mixture.

[0082] Preparation Example 6:

[0083] In a nitrogen atmosphere, 1 mol of lithium trioxalatophosphate and 1.1 mol of lithium tetrafluorooxalatophosphate were added to 2000 g of dimethyl carbonate, mixed and dissolved, and reacted. The mixture was heated to a reaction temperature of 120° C. for 5 hours to obtain a lithium difluorodioxalatophosphate solution. The solution was returned to room temperature, and the insoluble matter was first filtered out. The filtrate was collected and then concentrated under reduced pressure to obtain a concentrated solution.

[0084] Preparation Example 7:

[0085] 500 g of lithium difluorobis(oxaloyl)phosphate with 99% purity by ion chromatography was added to a mixed solution of 250 g of dimethyl carbonate and 250 g of ethylene carbonate, the mixture was heated to 90° C. and refluxed to dissolve, and the solution was obtained after hot filtration to remove mechanical impurities.

[0086] Preparation Example 8:

[0087] 500 g of sodium difluorobisoxalophosphate with an ion chromatography purity of 99% was added to a mixed solvent of 180 g of dimethyl carbonate and 20 g of ethylene carbonate, the mixture was heated to 60° C. and refluxed to dissolve, and mechanical impurities were removed by hot filtration to obtain a solution.

[0088] Preparation Example 9:

[0089] At room temperature, add 76.7 g (0.505 mol) of solid lithium hexafluorophosphate and 90.05 g (1.0 mol) of anhydrous oxalic acid to 1000 g of ethyl methyl carbonate. Heat to 45°C, and begin dropwise addition of 84.95 g (0.5 mol) of liquid silicon tetrachloride. Continue the addition over 2 hours, then maintain the temperature at 45-55°C with stirring for 4 hours. During this time, silicon tetrafluoride and hydrogen chloride gases are generated. 19FNMR analysis indicated complete reaction of the lithium hexafluorophosphate in the reaction solution. The reaction solution was cooled to room temperature and filtered to remove trace insoluble matter. The filtrate was concentrated under reduced pressure at 50°C to a viscous, translucent solid-liquid mixture. 10 g of dimethyl carbonate and 90 g of ethylene carbonate were added and heated at 90°C until the solid-liquid mixture dissolved.

[0090] Example 1:

[0091] 1500 g of petroleum ether was added dropwise to the dimethyl carbonate solution of lithium difluorobisoxalatophosphate obtained in Preparation Example 1, and the mixture was crystallized while stirring at 70°C. The mixture was stirred for 3 h, and wet crystals were separated. The mixture was dried at 500 Pa and 50°C to obtain 528.5 g of product, which was determined to be LiPF2(C2O4)2·xDMC, where x=0.484. The product had a purity of 99.7%, an angle of repose of 29°, a bulk density of 1.07 g / ml, and a yield of 90.1%.

[0092] Example 2:

[0093] 3000 g of 1,4-dichlorobutane was added dropwise to the ethylene carbonate solution of sodium difluorobisoxalatephosphate obtained in Preparation Example 2, and the mixture was crystallized at 50°C with stirring for 10 h. Wet crystals were separated and dried at 200 Pa and 50°C to obtain 621 g of product. The product was determined to be NaPF2(C2O4)2·xEC, x=1.001, with a product purity of 99.8%, an angle of repose of 27°, a bulk density of 1.11 g / ml, and a yield of 93.5%.

[0094] Example 3:

[0095] To the clear mixed solution obtained in Preparation Example 3, 1000 g of 1,2,3-trichloropropane was added dropwise at 45°C, stirred, and crystallized. The mixture was stirred for 8 hours, cooled to 10°C, and filtered. After filtration, the mixture was rinsed with 200 g of 1,2,3-trichloropropane. The wet product was cooled to constant weight at room temperature to obtain 168.9 g of product, which was determined to be LiPF2(C2O4)2·xEC, with x=1.074. The yield was 97.5%, the purity was 99.5%, the angle of repose was 30°, and the bulk density was 1.21 g / ml. Figures 4 to 6 show the NMR spectra of the product obtained in Example 3.

[0096] Example 4:

[0097] To the clear mixed solution obtained in Preparation Example 3, 500 g of o-xylene was added dropwise at 60°C, stirring for 1 hour while crystallizing. After the addition was complete, the mixture was filtered with suction at 10°C and rinsed with 100 g of o-xylene to obtain a wet product. The product was dried at 40°C to constant weight to obtain 129.7 g of product, which was determined to be LiPF2(C2O4)2·x, EC, x=0.114. The yield was 99.0%, the purity was 99.7%, the angle of repose was 29°, and the bulk density was 1.23 g / ml.

[0098] Example 5:

[0099] The filtrate from Preparation Example 4 was concentrated under reduced pressure at 80°C to 300 g. 1000 g of n-hexane was added dropwise at 50°C with stirring while crystallizing. The mixture was stirred for 2 h, cooled to 30°C, and filtered. After filtration, the mixture was rinsed with 300 g of n-hexane to obtain a wet product, which was then cooled to constant weight at room temperature to obtain 280.8 g of product, which was determined to be LiPF2(C2O4)2·xDMC, with x=0.355. The yield was 98.9%, the purity was 99.5%, the bulk density was 0.994 g / ml, and the angle of repose was 31°.

[0100] Example 6:

[0101] The filtrate from Preparation Example 4 was concentrated under reduced pressure at 80°C to 500 g. 1500 g of toluene was added dropwise at 75°C with stirring for crystallization. The mixture was stirred for 12 h, cooled to 30°C, and filtered. The mixture was then rinsed with 100 g of toluene to obtain a wet product, which was then cooled to constant weight at room temperature to obtain 324.9 g of product, identified as LiPF2(C2O4)2·xDMC, with x=1.002. The yield was 95.0%, the purity was 99.6%, the bulk density was 0.989 g / ml, and the angle of repose was 33°. Figures 1 to 3 show the NMR spectra of the product obtained in Example 6.

[0102] Example 7:

[0103] The filtrate from Preparation Example 5 was concentrated under reduced pressure at 80°C to 550 g. 1000 g of o-xylene was added dropwise at 75°C with stirring for crystallization. The mixture was stirred for 6 hours, cooled to 30°C, and filtered. After filtration, the mixture was rinsed with 100 g of o-xylene to obtain a wet product. The product was cooled to constant weight at room temperature to obtain 328.1 g of product, which was determined to be LiPF2(C2O4)2·xDMC, with x=0.714. The yield was 93.5%, the purity was 99.8%, the bulk density was 0.956 g / ml, and the angle of repose was 38°.

[0104] Example 8:

[0105] 500 g of the concentrate obtained in Preparation Example 6 was cooled to 60°C, and 800 g of 1,2-dichloroethane was added dropwise with stirring to induce crystallization. The mixture was stirred for 4 hours, cooled to 10°C, and filtered. After filtration, it was rinsed with 100 g of 1,2-dichloroethane. The wet product was cooled and pumped to a constant weight at room temperature to obtain 296.1 g of product, which was determined to be LiPF2(C2O4)2·xDMC, with x = 0.502. The yield was 95.0%, the purity was 99.6%, the bulk density was 1.02 g / ml, and the angle of repose was 30°.

[0106] Example 9:

[0107] To the mixed solution of lithium difluorobis(oxalatophosphate) obtained in Preparation Example 7 was added dropwise 1000 g of toluene. The mixture was stirred at 60°C for 10 h while crystallizing. Wet crystals were separated and dried at 50°C under 500 Pa to obtain 636.5 g of product. The product was determined to be LiPF2(C2O4)2·0.501DMC·0.510EC, with x=1.011. The product had a purity of 99.6%, an angle of repose of 30°, a bulk density of 1.05 g / ml, and a yield of 94.0%. Figures 7-9 show the NMR spectra of the product obtained in Example 9.

[0108] Example 10:

[0109] To the mixed solution of sodium difluorobis(oxalatophosphate) obtained in Preparation Example 8 was added dropwise 3000 g of 1,4-dichlorobutane. Crystallization was carried out at 40°C with stirring for 12 h. Wet crystals were separated and dried at 200 Pa and 30°C to obtain 616.2 g of product. The product was determined to be NaPF2(C2O4)2·0.889DMC·0.102EC, with x=0.991. The product had a purity of 99.5%, an angle of repose of 27°, a bulk density of 1.01 g / ml, and a yield of 92.5%. Figures 10-12 show the NMR spectra of the product obtained in Example 10.

[0110] Example 11:

[0111] To the clear mixed solution obtained in Preparation Example 9, 1500 g of o-xylene was added dropwise at 60°C with stirring to induce crystallization. The mixture was stirred for 11 hours and filtered with suction at 10°C. The mixture was then rinsed with 100 g of o-xylene to obtain a wet product. The product was then dried at 40°C to constant weight to yield 161.22 g of product, which was determined to be LiPF2(C2O4)2·0.112DMC·1.002EC, with x=1.114. The yield was 92.1%, the purity was 99.2%, the angle of repose was 31°, and the bulk density was 0.996 g / ml. Figures 13-15 show the NMR spectra of the product obtained in Example 11.

[0112] Comparative Example 1 (corresponding to Preparation Example 3):

[0113] At room temperature, 76.7 g (0.505 mol) of solid lithium hexafluorophosphate and 90.05 g (1.0 mol) of anhydrous oxalic acid were added to 1000 g of ethyl methyl carbonate. The mixture was heated to 45°C and 84.95 g (0.5 mol) of liquid silicon tetrachloride was added dropwise. The addition was continued for 2 hours, followed by stirring at 45-55°C for 4 hours, during which time silicon tetrafluoride and hydrogen chloride gases were generated. The reaction solution was cooled to room temperature and filtered to remove trace insoluble matter. The filtrate was concentrated under reduced pressure at 50-80°C to a viscous, translucent solid-liquid mixture. 400 g of toluene was then added and the mixture was cooled to room temperature in a cold water bath. A large amount of white solid precipitated from the mixture. The mixture was transferred to a glove box, filtered, and dried under reduced pressure at 70-80°C for 12 hours to yield 104.1 g of the product as a white powder, with a yield of 82.6%. The product had an angle of repose of 52°, a bulk density of 0.566 g / ml, and a purity of 98.8%.

[0114] Comparative Example 2 (corresponding to Preparation Example 4):

[0115] At room temperature, add 152g (1.0 mol) of solid lithium hexafluorophosphate and 180.1g (2.0 mol) of anhydrous oxalic acid to 1000g of dimethyl carbonate. Heat to 50°C, and begin dropwise addition of a solution prepared by adding 169.9g (1 mol) of liquid silicon tetrachloride and 500g of dimethyl carbonate. Continue the addition over 5 hours, then maintain the temperature at 40-50°C with stirring for 6 hours. During this time, silicon tetrafluoride and hydrogen chloride gas are generated. 19 FNMR analysis indicated complete reaction of the lithium hexafluorophosphate in the reaction solution. The reaction solution was cooled to room temperature and filtered to remove trace insoluble matter. The filtrate was concentrated under reduced pressure at 80°C to a viscous, translucent solid-liquid mixture. 800 g of dichloroethane was added all at once, and the mixture was cooled to room temperature in a cold water bath. A large amount of white solid precipitated, which was then transferred to a glove box for filtration and dried under reduced pressure at 70-80°C for 6 hours to yield 200.3 g of the product as a white powder, with a yield of 79.5%, a purity of 95.9%, an angle of repose of 49°, and a bulk density of 0.690 g / ml.

[0116] Comparative Example 3 (corresponding to Preparation Example 6):

[0117] In a nitrogen atmosphere, 1 mol of lithium trioxalate phosphate and 1.1 mol of lithium tetrafluorooxalate phosphate were added to 2000 g of dimethyl carbonate, mixed and dissolved, reacted, heated to a reaction temperature of 120 ° C, and the reaction time was 5 hours to prepare a lithium difluorobis(oxalate)phosphate solution. The solution was returned to room temperature, and the insoluble matter was first filtered to remove the insoluble matter. The filtrate was collected and then concentrated under reduced pressure to obtain 500 g of a concentrate. 800 g of dichloroethane was then added dropwise for crystallization. The solution was cooled to room temperature. A large amount of white solid precipitated from the system. The solution was transferred to a glove box, filtered, washed with 100 g of dichloroethane, and dried under vacuum at 5 kPa and 90 ° C for 4 hours to obtain lithium difluorobis(oxalate)phosphate as a white powder with a yield of 85%, a purity of 95.8%, an angle of repose of 50°, and a bulk density of 0.701 g / ml.

[0118] Comparative Example 4:

[0119] At room temperature, 76.7 g (0.505 mol) of solid lithium hexafluorophosphate and 90.05 g (1.0 mol) of anhydrous oxalic acid were added to 1000 g of ethyl methyl carbonate. The mixture was heated to 45°C and 84.95 g (0.5 mol) of liquid silicon tetrachloride was added dropwise. The mixture was added dropwise for 2 hours, then stirred at 45-55°C for 4 hours, during which time silicon tetrafluoride and hydrogen chloride gases were generated. The reaction solution was cooled to room temperature and filtered to remove trace insoluble matter. The filtrate was concentrated under reduced pressure at 50-80°C to a viscous, translucent solid-liquid mixture. 400 g of toluene was then added, and the mixture was cooled to room temperature in a cold water bath. Crystallization was carried out while stirring for 20 minutes. A large amount of white solid precipitated from the system. The solid was transferred to a glove box, filtered, and dried under reduced pressure at 70-80°C for 12 hours to obtain 105.8 g of the product, lithium difluorobis(oxalophosphate), as a white powder, with a yield of 84.0%. The angle of repose is 53°, the bulk density is 0.570 g / ml, and the purity is 98.6%.

[0120] Comparative Example 5:

[0121] At room temperature, add 152g (1.0 mol) of solid lithium hexafluorophosphate and 180.1g (2.0 mol) of anhydrous oxalic acid to 1000g of dimethyl carbonate. Heat to 50°C, and begin dropwise addition of a solution prepared by adding 169.9g (1 mol) of liquid silicon tetrachloride and 500g of dimethyl carbonate. Continue the addition over 5 hours, then maintain the temperature at 40-50°C with stirring for 6 hours. During this time, silicon tetrafluoride and hydrogen chloride gas are generated. 19FNMR analysis indicated complete reaction of the lithium hexafluorophosphate in the reaction solution. The reaction solution was cooled to room temperature and filtered to remove trace insoluble matter. The filtrate was concentrated under reduced pressure at 80°C to a viscous, translucent solid-liquid mixture. 800 g of dichloroethane was added all at once, and the mixture was cooled to room temperature in a cold water bath. Crystallization occurred while stirring for 30 minutes, during which a large amount of white solid precipitated. The mixture was transferred to a glove box, filtered, and dried under reduced pressure at 70-80°C for 6 hours to obtain 204.8 g of the product, lithium difluorobis(oxaloyl)phosphate, as a white powder. The yield was 81.3%, the purity was 95.6%, the angle of repose was 50°, and the bulk density was 0.695 g / ml.

[0122] Comparative Example 6:

[0123] In a nitrogen atmosphere, 1 mol of lithium trioxalate phosphate and 1.1 mol of lithium tetrafluorooxalate phosphate were added to 2000 g of dimethyl carbonate, mixed and dissolved, reacted, heated to a reaction temperature of 120 ° C, and the reaction time was 5 hours to prepare a difluorodioxalate lithium phosphate solution. The solution was returned to room temperature, first filtered to remove insoluble matter, and the filtrate was collected. The filtrate was then concentrated under reduced pressure to obtain 500 g of a concentrate. 80 g of dichloroethane was then added dropwise for crystallization. The solution was cooled to room temperature and crystallized while stirring for 40 min. A large amount of white solid was precipitated from the system. The solution was transferred to a glove box, filtered, washed with 100 g of dichloroethane, and dried under vacuum at 5 kPa, 90 ° C, and 4 hours to obtain 433.9 g of a white powder of lithium difluorodioxalate phosphate with a yield of 86%, a purity of 96.5%, an angle of repose of 51 °, and a bulk density of 0.703 g / ml.

[0124] According to Comparative Examples 1-3 and Control Examples 3-8, after adding the poor solvent, no stirring was performed, and a large amount of crystals precipitated, and no composition could be obtained. The product yield and purity were low, and the obtained product had a relatively small bulk density, a large angle of repose, and poor fluidity.

[0125] According to Comparative Examples 4-6 and Control Examples 3-8, after adding the poor solvent, the stirring time was less than 1 hour, and the composition could not be obtained. The product yield and purity were low. The obtained product had a relatively small bulk density, a large repose angle, and poor fluidity.

[0126] Analytical methods:

[0127] Moisture: Coulometric moisture analyzer (Wantong 831);

[0128] Complexation ratio: The solvent content was quantitatively measured by gas spectrometer and then converted into molar weight using a Shimadzu 2010pro gas chromatograph.

[0129] Gas chromatography was performed using Shimadzu HP-5, 30 m × 0.32 mm × 0.25 μm as a column;

[0130] Purity and impurity ions: Ion chromatography, Thermo Fisher Aquion, chromatographic column SH-AC-4, 250 mm × 4.6 mm; guard column SH-AG-4, 50 mm × 4.6 mm;

[0131] Bulk density: Take 50g of sample in a graduated cylinder, pump it 100 times, measure the volume, and calculate the corresponding density;

[0132] Angle of repose measuring instrument: XF-4324 Dust Angle of Repose Meter, Xiamen Xiongfa Instrument Co., Ltd.

[0133] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form or substance. It should be pointed out that ordinary technicians in this technical field can make several improvements and supplements without departing from the method of the present invention. These improvements and supplements should also be regarded as the scope of protection of the present invention. Any equivalent changes, modifications and evolutions made by technicians familiar with this profession without departing from the spirit and scope of the present invention by using the technical content disclosed above are all equivalent embodiments of the present invention; at the same time, any equivalent changes, modifications and evolutions made to the above embodiments based on the essential technology of the present invention are still within the scope of the technical solution of the present invention.

Claims

1. A composition of difluoro bis(oxalato) phosphate, characterized in that, The chemical formula of the composition is: MPF2(C2O4)2·xB, where M is an alkali metal, B is an organic solvent, x is the molar ratio, and 0.05 < x < 1.

1.

2. The composition of difluorodioxalate phosphate according to claim 1, characterized in that, It further includes any one or more of the following features: a1) M is Li or Na; a2) B is selected from one or more of dimethyl carbonate and ethylene carbonate; a3) 0.5 ≤ x ≤ 1.

3. The composition of difluorodioxalate phosphate according to claim 1 or 2, characterized in that, The chemical formula of the composition is: MPF2(C2O4)2·x(DMC / EC), where M and x are as defined in claim 1 or 2, DMC is dimethyl carbonate, and EC is ethylene carbonate.

4. The composition of difluorodioxalate phosphate according to claim 1 or 2, characterized in that, The chemical formula of the composition is any one of the following: LiPF2(C2O4)2·xDMC, LiPF2(C2O4)2·xEC, NaPF2(C2O4)2·xDMC or NaPF2(C2O4)2·xEC; where x is as defined in claim 1 or 2, DMC is dimethyl carbonate, and EC is ethylene carbonate.

5. The composition of difluoro diphosphite oxalate according to claim 4, characterized in that, 0.3＜x＜1.1。 6. The composition of difluoro bis(oxalato)phosphate according to claim 5, wherein 0.5≤x≤1。 7. The preparation method of the composition of difluorodioxalate phosphate according to any one of claims 1 to 6, characterized in that, The preparation method includes: obtaining a mixed solution containing difluorodioxalate phosphate and an organic solvent, adding a poor solvent for crystallization, filtering to obtain a filter cake, and drying to obtain a composition of difluorodioxalate phosphate.

8. The preparation method of the composition of difluoro diphosphate oxalate according to claim 7, characterized in that, It further includes any one of the following features: b1) The mixed solution containing difluorodioxalate phosphate and an organic solvent is prepared by mixing difluorodioxalate phosphate and an organic solvent; b2) The mixed solution containing difluorodioxalate phosphate and an organic solvent is obtained during the preparation of difluorodioxalate phosphate.

9. The method for preparing the composition of difluorodioxalate phosphate according to claim 7 or 8, characterized in that, It further includes any one or more of the following features: c1) In the mixed solution containing difluorodioxalate phosphate and an organic solvent, the mass ratio of the organic solvent to difluorodioxalate phosphate is 1:1 to 5; c2) The mass ratio of difluorodioxalate phosphate to the poor solvent is 1:1 to 10; c3) The temperature range for crystallization is 10°C to 75°C; c4) The difluorodioxalate phosphate is selected from lithium difluorodioxalate phosphate or lithium sodium difluorodioxalate phosphate; c5) The organic solvent is selected from one or more of dimethyl carbonate, ethylene carbonate, and other solvents, and must contain dimethyl carbonate or ethylene carbonate; the other solvents are selected from one or more of methyl ethyl carbonate, diethyl carbonate, propylene carbonate, acetonitrile, tetrahydrofuran, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, and dioxane; c6) The poor solvent is a hydrocarbon solvent and / or a halogenated hydrocarbon solvent; c7) The drying is heating under vacuum; c8) In the step of adding a poor solvent for crystallization, when adding the poor solvent dropwise, crystallization is carried out while stirring, and the stirring time is 1 - 12 h.

10. The preparation method of the composition of difluoro bis(oxalato) phosphate according to claim 9, characterized in that, It further includes any one or more of the following features: c51) In feature c5), the organic solvent is selected from dimethyl carbonate and / or ethylene carbonate; c61) In feature c6), the hydrocarbon solvent is selected from one or more of n - hexane, cyclohexane, n - heptane, n - octane, petroleum ether, toluene, and xylene; c62) In feature c6), the halogenated hydrocarbon solvent is selected from one or more combinations of methylene chloride, chloroform, 1,2-dichloroethane, 1,1,1-trichloroethane, 1,1,2-trichloroethane, 1,2,3-trichloropropane, 1,1,2,2-tetrachloroethane, 1,4-dichlorobutane, and 1,1,2,2-tetrachloroethylene; c71) In feature c7), the temperature of heating under vacuum is 20°C to 90°C; c72) In feature c7), the pressure of heating under vacuum is 0 Pa to 20000 Pa.

11. The preparation method of the composition of difluorodioxalate phosphate according to claim 9, characterized in that, In feature c7), the temperature of heating under vacuum is 20°C to 50°C.

12. The method for preparing the composition of difluoro dicarboxylate phosphate according to claim 10, wherein, It further includes any one or more of the following features: c611) In feature c61), the hydrocarbon solvent is selected from one or more of petroleum ether, n-hexane, toluene, and o-xylene; c621) In feature c62), the halogenated hydrocarbon solvent is selected from one or more of 1,4-dichlorobutane, 1,2,3-trichloropropane, and 1,2-dichloroethane; c711) In feature c71), the temperature of heating under vacuum is 30°C to 50°C; c721) In feature c72), the pressure of heating under vacuum is 0 Pa to 10000 Pa.

13. Use of the composition of difluoro(dioxalato)phosphate as described in any one of claims 1 to 6 in an electrolyte.

14. Use of the composition of difluoro(dioxalato)phosphate as described in any one of claims 1 to 6 in a battery.

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