An alkali metal salt M + Y - Preparation method and electrolyte

Abstract

The present invention provides an alkali metal salt M + Y ‑ The preparation method comprises the following steps: reacting the compound represented by structural formula 1 with NH4 + Y ‑ Reaction to obtain alkali metal salt M + Y ‑ ;M + Selected from K + 、Na + and Li + One or more of; Y ‑ Selected from PO2F2 ‑ 、FSI ‑ DFOB ‑ PO3F 2‑ 、BOB ‑ 、BF4 ‑ One or more of; Structural Formula 1 wherein A is selected from the functional group shown in Structural Formula 2 or the functional group shown in Structural Formula 3; E is selected from Li, Na or K; Structural Formula 2 wherein R1 is selected from alkanes having 1 to 5 carbon atoms, aromatic hydrocarbons having 6 to 12 carbon atoms and their derivatives, cyclic carbonates having 3 to 6 carbon atoms and their derivatives; Structural Formula 3 wherein R2 is selected from nitrogen-containing heterocycles having 3 to 6 carbon atoms. The alkali metal salt M provided by the present invention + Y ‑ The preparation method can effectively increase the alkali metal salt M + Y ‑ The purity and yield of the product can be improved, thereby effectively improving the electrochemical performance of the secondary battery.

Description

Technical Field

[0001] The present invention belongs to the technical field of battery additive production, and specifically relates to an alkali metal salt M + Y - Preparation method and electrolyte. Background Art

[0002] In recent years, lithium-ion batteries have been widely used in various fields of society, such as consumer electronics, smart wearables, electric travel, and power storage. Some lithium salt additives, such as lithium difluorophosphate, lithium bis(fluorosulfonyl)imide, and lithium difluorooxalate borate, are lithium salts themselves. They can not only partially replace lithium salts, but also decompose to produce LiF and lithium carbonate due to their special structure and energy level effects. Therefore, SEI films can be formed at the positive and negative electrodes. Therefore, lithium salt additives can improve the high and low temperature performance and cycle stability of batteries and are widely used in lithium-ion batteries.

[0003] Lithium salt additives are usually difficult to synthesize directly. Most of them need to synthesize the corresponding ammonium salt first, and then convert the ammonium salt into the corresponding lithium salt additive by reaction. For example, there is a method for synthesizing lithium difluorophosphate, which mainly uses ammonium difluorophosphate to react with alkyl lithium or alcohol lithium, and then obtains lithium difluorophosphate after further purification. This method improves the purity of the product to a certain extent. However, whether ammonium difluorophosphate reacts with alkyl lithium or alcohol lithium, its reaction efficiency is low, and a catalyst containing metal ions such as SnCl4 needs to be introduced for the reaction to proceed normally. This catalyst will introduce metal ion impurities into the reaction product, and the metal ion impurities are difficult to remove in the subsequent purification process. Finally, they are combined with difluorophosphate anions and exist in the obtained lithium difluorophosphate in the form of impurities. Although the amount of introduced metal ion impurities is low, when lithium difluorophosphate is used as an electrolyte additive, it will still have an adverse effect on deteriorating the cycle performance of lithium-ion batteries. At the same time, even if a catalyst is introduced into this reaction mode, its reaction yield is still relatively low, and the reaction raw materials cannot be fully utilized. Summary of the invention

[0004] For existing alkali metal salts M + Y - There are problems of impurity introduction and insufficient reaction in the preparation of the present invention. The present invention provides an alkali metal salt M + Y - Preparation method and electrolyte.

[0005] The technical solution adopted by the present invention to solve the above technical problems is as follows:

[0006] In one aspect, the present invention provides an alkali metal salt M + Y - The preparation method comprises the following steps:

[0007] The compound shown in structural formula 1 is reacted with NH4 + Y - Reaction to obtain alkali metal salt M + Y - ;M + Selected from K + 、Na + and Li + One or more of; Y - Selected from PO2F2 - (difluorophosphate), FSI - (Bis(fluorosulfonyl)imide), DFOB - (difluorooxalate borate), PO3F 2- (monofluorophosphate), BOB - (bis(oxalatoborate), BF4 - (tetrafluoroborate);

[0008]

[0009] Structural formula 1

[0010] Wherein, A is selected from the functional group shown in Structural Formula 2 or the functional group shown in Structural Formula 3; E is selected from Li, Na or K;

[0011]

[0012] Structural formula 2

[0013] Wherein, R1 is selected from alkanes having 1 to 5 carbon atoms, aromatic hydrocarbons having 6 to 12 carbon atoms and their derivatives, cyclic carbonates having 3 to 6 carbon atoms and their derivatives;

[0014]

[0015] Structural formula 3

[0016] Wherein, R2 is selected from a nitrogen-containing heterocyclic ring having 3 to 6 carbon atoms.

[0017] Optionally, in structural formula 2, R1 is selected from alkanes having 1 to 5 carbon atoms, aromatic hydrocarbons and halogenated aromatic hydrocarbons having 6 to 12 carbon atoms, and cyclic carbonates having 3 to 6 carbon atoms.

[0018] Optionally, in structural formula 3, R2 is selected from an imidazole group, an oxazolidinone group or an oxathiazolidinyl group having 3 to 6 carbon atoms.

[0019] Optionally, the compound represented by structural formula 1 is selected from one or more of the following compounds:

[0020] .

[0021] Optionally, the compound shown in structural formula 1 and NH4 + Y - The reaction temperature is 10°C~160°C, the pressure is -0.1~0.3MPa, and the reaction time is 6~24h.

[0022] Optionally, the compound represented by the structural formula 1 and NH4 + Y - The reaction is carried out in a solvent-free system or in a non-aqueous solvent system.

[0023] Optionally, the compound represented by the structural formula 1 and NH4 + Y - The reaction is carried out in a non-aqueous solvent system at a reaction temperature of 60°C to 160°C, a pressure of 0.05 to 0.3 MPa, and a reaction time of 6 to 24 hours. After the reaction, by-products and solvents are removed by filtration and distillation to obtain a product containing an alkali metal salt M + Y - of crude product.

[0024] Optionally, the compound represented by the structural formula 1 and NH4 + Y - The reaction is carried out in a solvent-free system, wherein the compound represented by the structural formula 1 is reacted with NH4 + Y - The mixture was evenly mixed by ball milling under a protective atmosphere, and then put into a reactor. The reaction temperature was 20°C to 150°C, the pressure was -0.1 to 0.1 MPa, and the reaction time was 6 to 24 hours to obtain a product containing an alkali metal salt M. + Y - of crude product.

[0025] Optionally, the alkali metal salt M is obtained by reaction + Y - The crude product containing alkali metal salt M is treated with a non-aqueous solvent + Y - The crude product is recrystallized to contain alkali metal salt M + Y - The weight ratio of the crude product to the non-aqueous solvent is 1: (1-10), the dissolution temperature is 20°C-60°C, the recrystallization temperature is -10°C-20°C, and the crystals obtained by recrystallization are further vacuum dried to obtain the alkali metal salt M + Y - The drying temperature is 40℃~60℃, the drying vacuum degree is -98KPa~-99.5KPa, and the drying time is controlled at 6h~8h.

[0026] On the other hand, the present invention provides an electrolyte solution, comprising a solvent, an electrolyte salt and an additive, wherein the additive comprises an alkali metal salt M prepared by the above-mentioned preparation method. + Y - .

[0027] According to the present invention, the alkali metal salt M + Y - The preparation method uses an organic alkali metal salt shown in structural formula 1 to replace the existing alkyl lithium or alcohol lithium and NH4 + Y - The byproducts of the reaction are carbon dioxide, ammonia and organic matter R1-OH or R2-H. Compared with the existing synthesis method of alkyl lithium or alcohol lithium, the organic alkali metal salt shown in structural formula 1 is used as the reaction raw material, which effectively improves the reaction with NH4 + Y - The reactivity between them increases the alkali metal salt M + Y - The reaction can proceed normally without adding a catalyst, so the addition of a catalyst can be omitted during the production process, avoiding the need for alkali metal salt M + Y - Introducing other metal ion impurities into the reaction reduces the by-products of the reaction, and then using the alkali metal salt M + Y - When used in secondary batteries, it can effectively improve the electrochemical performance of the secondary batteries and avoid the degradation of the secondary battery performance caused by impurities. DETAILED DESCRIPTION

[0028] In order to make the technical problems, technical solutions and beneficial effects solved by the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0029] The present invention provides an alkali metal salt M + Y - The preparation method comprises the following steps:

[0030] The compound shown in structural formula 1 is reacted with NH4 + Y - Reaction to obtain alkali metal salt M + Y - ;M + Selected from K + 、Na + and Li + One or more of; Y - Selected from PO2F2 - (difluorophosphate), FSI -(Bis(fluorosulfonyl)imide), DFOB - (difluorooxalate borate), PO3F 2- (monofluorophosphate), BOB - (bis(oxalatoborate), BF4 - (tetrafluoroborate);

[0031]

[0032] Structural formula 1

[0033] Wherein, A is selected from the functional group shown in Structural Formula 2 or the functional group shown in Structural Formula 3; E is selected from Li, Na or K;

[0034]

[0035] Structural formula 2

[0036] Wherein, R1 is selected from alkanes having 1 to 5 carbon atoms, aromatic hydrocarbons having 6 to 12 carbon atoms and their derivatives, cyclic carbonates having 3 to 6 carbon atoms and their derivatives;

[0037]

[0038] Structural formula 3

[0039] Wherein, R2 is selected from a nitrogen-containing heterocyclic ring having 3 to 6 carbon atoms.

[0040] The organic alkali metal salt shown in the structural formula 1 is used to replace the existing alkyl lithium or alcohol lithium and NH4 + Y - The byproducts of the reaction are carbon dioxide, ammonia and organic matter R1-OH or R2-H. Compared with the existing synthesis method of alkyl lithium or alcohol lithium, the organic alkali metal salt shown in structural formula 1 is used as the reaction raw material, which effectively improves the reaction with NH4 + Y - The reactivity between them increases the alkali metal salt M + Y - The reaction can proceed normally without adding a catalyst, so the addition of a catalyst can be omitted during the production process, avoiding the need for alkali metal salt M + Y - Introducing other metal ion impurities into the reaction reduces the by-products of the reaction, and then using the alkali metal salt M + Y - When used in secondary batteries, it can effectively improve the electrochemical performance of the secondary batteries and avoid the degradation of the secondary battery performance caused by impurities.

[0041] In some embodiments, the derivatives of aromatic hydrocarbons having 6 to 12 carbon atoms refer to compounds in which any hydrogen atom in the aromatic hydrocarbon is replaced by a hydrocarbon group, a halogen, a halogenated hydrocarbon group, or the like; the derivatives of cyclic carbonates having 3 to 6 carbon atoms refer to compounds in which any hydrogen atom in the cyclic carbonate is replaced by a hydrocarbon group, a halogen, a halogenated hydrocarbon group, or the like.

[0042] In some embodiments, in structural formula 2, R1 is selected from alkanes having 1 to 5 carbon atoms, aromatic hydrocarbons and halogenated aromatic hydrocarbons having 6 to 12 carbon atoms, and cyclic carbonates having 3 to 6 carbon atoms.

[0043] In some embodiments, in formula 3, R2 is selected from an imidazole group, an oxazolidinone group or an oxathiazolidinyl group having 3 to 6 carbon atoms.

[0044] In some embodiments, depending on the type of secondary battery to be prepared, E can select different alkali metal ions. For example, in this embodiment, when preparing a lithium ion battery, E is selected from Li; when preparing a sodium ion battery, E is selected from Na.

[0045] In some embodiments, the compound represented by Structural Formula 1 is selected from one or more of the following compounds:

[0046] .

[0047] In some embodiments, the compound represented by structural formula 1 and NH4 + Y - The reaction temperature is 10°C~160°C, the pressure is -0.1~0.3MPa, and the reaction time is 6~24h.

[0048] As the reaction temperature increases, the reaction between the compound shown in formula 1 and NH4 + Y - However, when the reaction temperature is too high, the alkali metal salt M + Y - The decomposition and side reactions increase the reactivity of the by-products, which is not conducive to the alkali metal salt M + Y - Improved yield and purity.

[0049] In different embodiments, the compound represented by the structural formula 1 and NH4 + Y - The reaction is carried out in a solvent-free system or in a non-aqueous solvent system.

[0050] In some embodiments, the compound represented by the structural formula 1 and NH4 + Y -The reaction is carried out in a non-aqueous solvent system at a reaction temperature of 60°C to 160°C, a pressure of 0.05 to 0.3 MPa, and a reaction time of 6 to 24 hours. After the reaction, by-products and solvents are removed by filtration and distillation to obtain a product containing an alkali metal salt M + Y - of crude product.

[0051] The selection of the non-aqueous solvent is not particularly limited. In a preferred embodiment, the non-aqueous solvent is selected from aprotic organic solvents, for example, one or more of ether solvents, nitrile solvents, carbonate solvents, carboxylate solvents and sulfone solvents.

[0052] In some embodiments, the ether solvent includes a cyclic ether or a chain ether, preferably a chain ether with 3 to 10 carbon atoms and a cyclic ether with 3 to 6 carbon atoms. The cyclic ether may be, but is not limited to, one or more of 1,3-dioxolane (DOL), 1,4-dioxolane (DX), crown ether, tetrahydrofuran (THF), 2-methyltetrahydrofuran (2-CH3-THF), and 2-trifluoromethyltetrahydrofuran (2-CF3-THF); the chain ether may be, but is not limited to, dimethoxymethane, diethoxymethane, ethoxymethoxymethane, ethylene glycol di-n-propyl ether, ethylene glycol di-n-butyl ether, and diethylene glycol dimethyl ether.

[0053] In some embodiments, the nitrile solvent may specifically be, but is not limited to, one or more of acetonitrile, glutaronitrile, and malononitrile.

[0054] In some embodiments, the carbonate solvent includes a cyclic carbonate or a chain carbonate. The cyclic carbonate may be, but is not limited to, one or more of ethylene carbonate (EC), propylene carbonate (PC), and butylene carbonate (BC); the chain carbonate may be, but is not limited to, one or more of dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), and dipropyl carbonate (DPC).

[0055] In certain embodiments, it is also possible to preferably use chain carbonates with fluorine atoms (hereinafter referred to as "fluorinated chain carbonates"). The number of fluorine atoms possessed by the fluorinated chain carbonate is not particularly limited as long as it is more than 1, but is generally less than 6, preferably less than 4. When the fluorinated chain carbonate has a plurality of fluorine atoms, these fluorine atoms can be bonded to the same carbon or to different carbons. As the fluorinated chain carbonate, fluorinated dimethyl carbonate derivatives, fluorinated ethyl methyl carbonate derivatives, fluorinated diethyl carbonate derivatives, etc. can be listed.

[0056] Carboxylate solvents include cyclic carboxylate and / or chain carbonate. Examples of cyclic carboxylate include one or more of γ-butyrolactone, γ-valerolactone, and δ-valerolactone. Examples of chain carbonate include one or more of methyl acetate (MA), ethyl acetate (EA), propyl acetate (EP), butyl acetate, propyl propionate (PP), and butyl propionate.

[0057] In some embodiments, the sulfone solvent includes a cyclic sulfone and a chain sulfone. Preferably, in the case of a cyclic sulfone, it is usually a compound with 3 to 6 carbon atoms, preferably 3 to 5 carbon atoms, and in the case of a chain sulfone, it is usually a compound with 2 to 6 carbon atoms, preferably 2 to 5 carbon atoms. There is no special restriction on the amount of sulfone solvent added, and it is arbitrary within the range that does not significantly damage the effect of the lithium ion battery of the present invention. Relative to the total amount of solvent of the non-aqueous electrolyte, the volume ratio is usually 0.3% or more, preferably 0.5% or more, and more preferably 1% or more. In addition, the volume ratio is usually 40% or less, preferably 35% or less, and more preferably 30% or less. In the case of using two or more sulfone solvents in combination, the total amount of sulfone solvents can be made to meet the above range. When the amount of sulfone solvent added is within the above range, an electrolyte with excellent high temperature storage stability tends to be obtained.

[0058] In other embodiments, the compound represented by the structural formula 1 and NH4 + Y - The reaction is carried out in a solvent-free system, wherein the compound represented by the structural formula 1 is reacted with NH4 + Y - The mixture was evenly mixed by ball milling under a protective atmosphere, and then put into a reactor. The reaction temperature was 20°C to 150°C, the pressure was -0.1 to 0.1 MPa, and the reaction time was 6 to 24 hours to obtain a product containing an alkali metal salt M. + Y - of crude product.

[0059] Compared with the reaction in a non-aqueous solvent system, the solvent-free dry reaction using ball milling is beneficial to increase the alkali metal salt M + Y - The reaction yield is speculated to be due to the fact that the solvent-free reaction reduces the by-products generated by the solvent itself. At the same time, the product generated by the reaction has a low boiling point. The pressure is controlled in a negative pressure state, so that the carbon dioxide, ammonia, etc. generated by the reaction are quickly separated in the form of gas, making the reaction tend to generate alkali metal salt M + Y - direction, thereby increasing the alkali metal salt M + Y - The yield.

[0060] In some embodiments, the alkali metal salt M is obtained by reacting + Y - After the crude product is obtained, a non-aqueous solvent is used to react with the alkali metal salt M + Y - The crude product is recrystallized to contain alkali metal salt M + Y - The weight ratio of the crude product to the non-aqueous solvent is 1: (1-10), the dissolution temperature is 20°C-60°C, the recrystallization temperature is -10°C-20°C, and the crystals obtained by recrystallization are further vacuum dried to obtain the alkali metal salt M + Y - The drying temperature is 40℃~60℃, the drying vacuum degree is -98KPa~-99.5KPa, and the drying time is controlled at 6h~8h.

[0061] The alkali metal salt M can be removed by further vacuum drying. + Y - The surface solvent ensures that the alkali metal salt M + Y - To improve the purity of the finished product, in some embodiments, the alkali metal salt M may be treated with a non-aqueous solvent before vacuum drying. + Y - Rinse to further remove surface impurities.

[0062] In the recrystallization operation, the selection of the non-aqueous solvent used is not particularly limited. In a preferred embodiment, the non-aqueous solvent is selected from aprotic organic solvents, for example, it can be one or more of ether solvents, nitrile solvents, carbonate solvents, carboxylate solvents and sulfone solvents.

[0063] Another embodiment of the present invention provides an electrolyte solution, comprising a solvent, an electrolyte salt and an additive, wherein the additive comprises an alkali metal salt M prepared by the above-mentioned preparation method. + Y - .

[0064] The alkali metal salt M prepared by the above method + Y - It has the advantage of high purity and can effectively guarantee the electrochemical properties of the electrolyte.

[0065] The present invention is further described below by way of examples.

[0066] Example 1

[0067] This example is used to illustrate the lithium difluorophosphate and its preparation method disclosed in the present invention, and includes the following steps:

[0068] 1) Dimethyl carbonate and lithium iodide were mixed in a molar ratio of 3:1, heated and stirred, and then dimethyl carbonate and methyl iodide were removed by rotary evaporation to obtain a crude compound 1, which was washed with a corresponding carbonate solvent and dried in vacuo to obtain a crude compound 1.

[0069] 2) Compound 1 and ammonium difluorophosphate were evenly ground by ball milling at 0°C under nitrogen protection, and then put into a reactor, and reacted at a reaction temperature of 60°C and -0.1MPa to obtain a crude product containing lithium difluorophosphate, and then the crude product containing lithium difluorophosphate and ethylene glycol dimethyl ether were mixed in a mass ratio of 1:2 to obtain a lithium difluorophosphate solution, which was filtered, and the filtrate was introduced into a crystallization kettle for recrystallization and purification to obtain lithium difluorophosphate crystals.

[0070] 3) The lithium difluorophosphate crystals are introduced into a vacuum drying kettle for vacuum drying. The drying temperature is controlled at 50° C., the drying vacuum degree is -98 KPa, and the drying time is controlled at 7 hours to obtain a finished lithium difluorophosphate product.

[0071] Example 2

[0072] This example is used to illustrate the lithium difluorophosphate and the preparation method thereof disclosed in the present invention, and includes most of the operating steps in Example 1, except that:

[0073] In step 2), the reaction temperature is 90°C.

[0074] Example 3

[0075] This example is used to illustrate the lithium difluorophosphate and the preparation method thereof disclosed in the present invention, and includes most of the operating steps in Example 1, except that:

[0076] In step 2), the reaction temperature is 20°C.

[0077] Example 4

[0078] This example is used to illustrate the lithium difluorophosphate and its preparation method disclosed in the present invention, and includes the following steps:

[0079] 1) Dimethyl carbonate and lithium iodide were mixed in a molar ratio of 3:1, heated and stirred, and then dimethyl carbonate and methyl iodide were removed by rotary evaporation to obtain a crude compound 1, which was washed with a corresponding carbonate solvent and dried in vacuo to obtain a crude compound 1.

[0080] 2) Compound 1, ammonium difluorophosphate and dimethyl carbonate were placed in a reactor at 20°C under nitrogen protection, and reacted at a reaction temperature of 60°C and -0.05MPa for 6 hours. The vacuum was then adjusted to -0.1MPa and the reaction was continued for 2 hours to obtain a solution containing a crude lithium difluorophosphate product. The solution containing the crude lithium difluorophosphate product was filtered, and the filtrate was introduced into a crystallization kettle for recrystallization and purification to obtain lithium difluorophosphate crystals.

[0081] 3) The lithium difluorophosphate crystals are introduced into a vacuum drying kettle for vacuum drying. The drying temperature is controlled at 50° C., the drying vacuum degree is -98 KPa, and the drying time is controlled at 7 hours to obtain a finished lithium difluorophosphate product.

[0082] Example 5

[0083] This example is used to illustrate the lithium difluorophosphate and the preparation method thereof disclosed in the present invention, and includes most of the operating steps in Example 1, except that:

[0084] Compound 2 is used to replace compound 1 for reaction;

[0085] The preparation method of compound 2 is:

[0086] Using carbonyldiimidazole as raw material and carbonate as solvent, an equivalent amount of anhydrous lithium hydroxide was added in batches, and the by-product imidazole was filtered out to obtain compound 2.

[0087] In step 2), the reaction temperature is 150°C.

[0088] Example 6

[0089] This example is used to illustrate the lithium difluorophosphate and the preparation method thereof disclosed in the present invention, and includes most of the operating steps in Example 2, except that:

[0090] Compound 3 is used to replace compound 1 for the reaction;

[0091] The preparation method of compound 3 is:

[0092] Diethyl carbonate and lithium iodide were mixed at a molar ratio of 3:1, heated and stirred, and then dimethyl carbonate and ethyl iodide were removed by rotary evaporation to obtain a crude compound 3, which was then washed with a corresponding carbonate solvent and dried in vacuo to obtain a crude compound 3.

[0093] Example 7

[0094] This example is used to illustrate the lithium difluorophosphate and the preparation method thereof disclosed in the present invention, and includes most of the operating steps in Example 1, except that:

[0095] Compound 4 is used to replace compound 1 for the reaction;

[0096] The preparation method of compound 4 is:

[0097] Diisopropyl carbonate and lithium isopropoxide were mixed in a molar ratio of 3:1, and reacted under pressure to obtain a crude compound 4. The solvent and by-products were removed by rotary evaporation, and the compound 4 was washed with a corresponding carbonate solvent and dried in vacuo to obtain the crude compound 4.

[0098] Example 8

[0099] This example is used to illustrate the sodium difluorophosphate and its preparation method disclosed in the present invention, and comprises the following steps:

[0100] 1) Dimethyl carbonate and sodium iodide were mixed at a molar ratio of 3:1, heated and stirred, and then dimethyl carbonate and methyl iodide were removed by rotary evaporation to obtain a crude compound 5, which was then washed with a corresponding carbonate solvent and dried in vacuo to obtain a crude compound 5.

[0101] 2) Compound 5 and ammonium difluorophosphate were evenly ground by ball milling at 0°C under nitrogen protection, and then put into a reactor, and reacted at a reaction temperature of 60°C and -0.1MPa to obtain a crude product containing sodium difluorophosphate, and then the crude product containing sodium difluorophosphate and ethylene glycol dimethyl ether were mixed in a mass ratio of 1:2 to obtain a sodium difluorophosphate solution, which was filtered, and the filtrate was introduced into a crystallization kettle for recrystallization and purification to obtain sodium difluorophosphate crystals.

[0102] 3) The sodium difluorophosphate crystals are introduced into a vacuum drying kettle for vacuum drying, the drying temperature is controlled at 50°C, the drying vacuum degree is -98KPa, and the drying time is controlled at 7h to obtain a finished sodium difluorophosphate product.

[0103] Example 9

[0104] This example is used to illustrate the sodium difluorophosphate and its preparation method disclosed in the present invention, and includes most of the operating steps in Example 7, except that:

[0105] In step 2), the reaction temperature is 90°C.

[0106] Example 10

[0107] This example is used to illustrate the sodium difluorophosphate and its preparation method disclosed in the present invention, and comprises the following steps:

[0108] 1) Dimethyl carbonate and sodium iodide were mixed at a molar ratio of 3:1, heated and stirred, and then dimethyl carbonate and methyl iodide were removed by rotary evaporation to obtain a crude compound 5, which was then washed with a corresponding carbonate solvent and dried in vacuo to obtain a crude compound 5.

[0109] 2) Compound 5, ammonium difluorophosphate and dimethyl carbonate were placed in a reactor at 20°C under nitrogen protection, and reacted at a reaction temperature of 60°C and -0.05MPa for 6 hours. The vacuum was then adjusted to -0.1MPa and the reaction was continued for 2 hours to obtain a solution containing a crude sodium difluorophosphate product. The solution containing the crude sodium difluorophosphate product was filtered, and the filtrate was introduced into a crystallization kettle for recrystallization and purification to obtain sodium difluorophosphate crystals.

[0110] 3) The sodium difluorophosphate crystals are introduced into a vacuum drying kettle for vacuum drying, the drying temperature is controlled at 50°C, the drying vacuum degree is -98KPa, and the drying time is controlled at 7h to obtain a finished sodium difluorophosphate product.

[0111] Embodiment 11

[0112] This example is used to illustrate the sodium difluorophosphate and its preparation method disclosed in the present invention, and includes most of the operating steps in Example 7, except that:

[0113] In step 2), the reaction temperature is 20°C.

[0114] Example 12

[0115] This example is used to illustrate the sodium difluorophosphate and its preparation method disclosed in the present invention, and includes most of the operating steps in Example 7, except that:

[0116] Compound 6 is used to replace compound 5 for the reaction;

[0117] The preparation method of compound 6 is:

[0118] Using carbonyldiimidazole as raw material and carbonate as solvent, an equivalent amount of anhydrous sodium hydroxide was added in batches, and the by-product imidazole was filtered out to obtain compound 6.

[0119] In step 2), the reaction temperature is 150°C.

[0120] Embodiment 13

[0121] This example is used to illustrate the sodium difluorophosphate and its preparation method disclosed in the present invention, and includes most of the operating steps in Example 7, except that:

[0122] Compound 7 is used to replace compound 5 for the reaction;

[0123] The preparation method of compound 7 is:

[0124] Diethyl carbonate and sodium iodide were mixed at a molar ratio of 3:1, heated and stirred, and then dimethyl carbonate and ethyl iodide were removed by rotary evaporation to obtain a crude compound 7, which was then washed with a corresponding carbonate solvent and dried in vacuo to obtain a crude compound 7.

[0125] Embodiment 14

[0126] This example is used to illustrate the sodium difluorophosphate and its preparation method disclosed in the present invention, and includes most of the operating steps in Example 7, except that:

[0127] Compound 8 is used to replace compound 5 for the reaction;

[0128] The preparation method of compound 8 is:

[0129] Diisopropyl carbonate and sodium isopropoxide were mixed in a molar ratio of 3:1, and reacted under pressure to obtain a crude compound 8. The solvent and by-products were removed by rotary evaporation, and the compound 8 was washed with a corresponding carbonate solvent and dried in vacuo to obtain the crude compound 8.

[0130] Embodiment 15

[0131] This example is used to illustrate the sodium bis(fluorosulfonyl)imide disclosed in the present invention and its preparation method, comprising the following steps:

[0132] 1) Dimethyl carbonate and sodium iodide were mixed at a molar ratio of 3:1, heated and stirred, and then dimethyl carbonate and methyl iodide were removed by rotary evaporation to obtain a crude compound 5, which was then washed with a corresponding carbonate solvent and dried in vacuo to obtain a crude compound 5.

[0133] 2) Compound 5 and ammonium bis(fluorosulfonyl)imide were uniformly ground by ball milling at 0°C under nitrogen protection, and then put into a reactor, and reacted at a reaction temperature of 60°C and -0.1MPa to obtain a crude product containing sodium bis(fluorosulfonyl)imide, and then the crude product containing sodium bis(fluorosulfonyl)imide and ethylene glycol dimethyl ether were mixed in a mass ratio of 1:2 to obtain a sodium bis(fluorosulfonyl)imide solution, which was filtered, and the filtrate was introduced into a crystallization kettle for recrystallization and purification to obtain sodium bis(fluorosulfonyl)imide crystals.

[0134] 3) The sodium bis(fluorosulfonyl)imide crystals are introduced into a vacuum drying kettle for vacuum drying, the drying temperature is controlled at 50° C., the drying vacuum degree is -98 KPa, and the drying time is controlled at 7 h to obtain a finished sodium bis(fluorosulfonyl)imide product.

[0135] Example 16

[0136] This example is used to illustrate the sodium difluorooxalatoborate and its preparation method disclosed in the present invention, and includes the following steps:

[0137] 1) Dimethyl carbonate and sodium iodide were mixed at a molar ratio of 3:1, heated and stirred, and then dimethyl carbonate and methyl iodide were removed by rotary evaporation to obtain a crude compound 5, which was then washed with a corresponding carbonate solvent and dried in vacuo to obtain a crude compound 5.

[0138] 2) Compound 5 and ammonium difluorooxalatoborate were evenly ground by ball milling at 0°C under nitrogen protection, and then put into a reactor. After the reaction was carried out at a reaction temperature of 60°C and -0.1MPa to obtain a crude product containing sodium difluorooxalatoborate, the crude product containing sodium difluorooxalatoborate and ethylene glycol dimethyl ether were mixed in a mass ratio of 1:2 to obtain a sodium difluorooxalatoborate solution, which was filtered, and the filtrate was introduced into a crystallization kettle for recrystallization and purification to obtain sodium difluorooxalatoborate crystals.

[0139] 3) The sodium difluorooxalate borate crystals are introduced into a vacuum drying kettle for vacuum drying, the drying temperature is controlled at 50° C., the drying vacuum degree is -98 KPa, and the drying time is controlled at 7 h to obtain a finished sodium difluorooxalate borate.

[0140] Embodiment 17

[0141] This example is used to illustrate the sodium monofluorophosphate and its preparation method disclosed in the present invention, and comprises the following steps:

[0142] 1) Dimethyl carbonate and sodium iodide were mixed in a molar ratio of 3:1, heated and stirred, and then dimethyl carbonate and methyl iodide were removed by rotary evaporation to obtain a crude compound 5, which was then washed with a corresponding carbonate solvent and dried in vacuo to obtain a crude compound 5.

[0143] 2) Compound 5 and ammonium monofluorophosphate were evenly ground by ball milling at 0°C under nitrogen protection, and then put into a reactor, and reacted at a reaction temperature of 60°C and -0.1MPa to obtain a crude product containing sodium monofluorophosphate, and then the crude product containing sodium monofluorophosphate and ethylene glycol dimethyl ether were mixed in a mass ratio of 1:2 to obtain a sodium monofluorophosphate solution, which was filtered, and the filtrate was introduced into a crystallization kettle for recrystallization and purification to obtain sodium monofluorophosphate crystals.

[0144] 3) The sodium monofluorophosphate crystals are introduced into a vacuum drying kettle for vacuum drying, the drying temperature is controlled at 50°C, the drying vacuum degree is -98KPa, and the drying time is controlled at 7h to obtain a finished sodium monofluorophosphate product.

[0145] Embodiment 18

[0146] This example is used to illustrate the sodium bis(oxalatoborate) disclosed in the present invention and its preparation method, comprising the following steps:

[0147] 1) Dimethyl carbonate and sodium iodide were mixed in a molar ratio of 3:1, heated and stirred, and then dimethyl carbonate and methyl iodide were removed by rotary evaporation to obtain a crude compound 5, which was then washed with a corresponding carbonate solvent and dried in vacuo to obtain a crude compound 5.

[0148] 2) Compound 5 and ammonium bis(oxalatoborate) were evenly ground by ball milling at 0°C under nitrogen protection, and then put into a reactor. After the reaction was carried out at a reaction temperature of 60°C and -0.1MPa to obtain a crude product containing sodium bis(oxalatoborate), the crude product containing sodium bis(oxalatoborate) and ethylene glycol dimethyl ether were mixed in a mass ratio of 1:2 to obtain a sodium bis(oxalatoborate) solution, which was filtered, and the filtrate was introduced into a crystallization kettle for recrystallization and purification to obtain sodium bis(oxalatoborate) crystals.

[0149] 3) The sodium bis(oxalatoborate) crystals are introduced into a vacuum drying kettle for vacuum drying, the drying temperature is controlled at 50°C, the drying vacuum degree is -98KPa, and the drying time is controlled at 7h to obtain a finished sodium bis(oxalatoborate) product.

[0150] Embodiment 19

[0151] This example is used to illustrate the sodium tetrafluoroborate and its preparation method disclosed in the present invention, and comprises the following steps:

[0152] 1) Dimethyl carbonate and sodium iodide were mixed at a molar ratio of 3:1, heated and stirred, and then dimethyl carbonate and methyl iodide were removed by rotary evaporation to obtain a crude compound 5, which was then washed with a corresponding carbonate solvent and dried in vacuo to obtain a crude compound 5.

[0153] 2) Compound 5 and ammonium tetrafluoroborate were evenly ground by ball milling at 0°C under nitrogen protection, and then put into a reactor. After the reaction was carried out at a reaction temperature of 60°C and -0.1MPa to obtain a crude product containing sodium tetrafluoroborate, the crude product containing sodium tetrafluoroborate and ethylene glycol dimethyl ether were mixed in a mass ratio of 1:2 to obtain a sodium tetrafluoroborate solution, which was filtered and the filtrate was introduced into a crystallization kettle for recrystallization and purification to obtain sodium tetrafluoroborate crystals.

[0154] 3) The sodium tetrafluoroborate crystals are introduced into a vacuum drying kettle for vacuum drying. The drying temperature is controlled at 50°C, the drying vacuum is -98KPa, and the drying time is controlled at 7h to obtain a finished sodium tetrafluoroborate product.

[0155] Comparative Example 1

[0156] This comparative example is used to compare and illustrate the lithium difluorophosphate and the preparation method thereof disclosed in the present invention, and includes most of the operating steps in Example 1, except that:

[0157] Lithium hydroxide was used to replace compound 1 for the reaction.

[0158] Comparative Example 2

[0159] This comparative example is used to compare and illustrate the lithium difluorophosphate and the preparation method thereof disclosed in the present invention, and includes most of the operating steps in Example 2, except that:

[0160] Lithium hydroxide was used to replace compound 1 for the reaction.

[0161] Comparative Example 3

[0162] This comparative example is used to compare and illustrate the lithium difluorophosphate and the preparation method thereof disclosed in the present invention, and includes most of the operating steps in Example 4, except that:

[0163] Lithium hydroxide was used to replace compound 2 for the reaction.

[0164] Comparative Example 4

[0165] This comparative example is used to compare and illustrate the lithium difluorophosphate and the preparation method thereof disclosed in the present invention, and includes most of the operating steps in Example 1, except that:

[0166] Lithium carbonate was used to replace compound 1 for the reaction.

[0167] Comparative Example 5

[0168] This comparative example is used to compare and illustrate the lithium difluorophosphate and the preparation method thereof disclosed in the present invention, and includes most of the operating steps in Example 1, except that:

[0169] Tert-butyl lithium was used to replace compound 1 for the reaction.

[0170] Comparative Example 6

[0171] This comparative example is used to compare and illustrate the lithium difluorophosphate and the preparation method thereof disclosed in the present invention, and includes most of the operating steps in Example 1, except that:

[0172] Lithium tert-butoxide was used to replace compound 1 for the reaction.

[0173] Comparative Example 7

[0174] This comparative example is used to compare and illustrate the sodium difluorophosphate and the preparation method thereof disclosed in the present invention, and includes most of the operating steps in Example 7, except that:

[0175] Sodium hydroxide was used to replace compound 5 for the reaction.

[0176] Comparative Example 8

[0177] This comparative example is used to compare and illustrate the sodium difluorophosphate and the preparation method thereof disclosed in the present invention, and includes most of the operating steps in Example 8, except that:

[0178] Sodium hydroxide was used to replace compound 5 for the reaction.

[0179] Comparative Example 9

[0180] This comparative example is used to compare and illustrate the sodium difluorophosphate and the preparation method thereof disclosed in the present invention, and includes most of the operating steps in Example 10, except that:

[0181] Sodium hydroxide was used to replace compound 6 for the reaction.

[0182] Comparative Example 10

[0183] This comparative example is used to compare and illustrate the sodium difluorophosphate and the preparation method thereof disclosed in the present invention, and includes most of the operating steps in Example 8, except that:

[0184] Sodium carbonate was used to replace compound 1 for the reaction.

[0185] Comparative Example 11

[0186] This comparative example is used to compare and illustrate the sodium difluorophosphate and the preparation method thereof disclosed in the present invention, and includes most of the operating steps in Example 7, except that:

[0187] Sodium tert-butoxide was used to replace compound 5 for the reaction.

[0188] Comparative Example 12

[0189] This comparative example is used to compare and illustrate the sodium bis(fluorosulfonyl)imide and the preparation method thereof disclosed in the present invention, and includes most of the operating steps in Example 15, except that:

[0190] Sodium hydroxide was used to replace compound 5 for the reaction.

[0191] Comparative Example 13

[0192] This comparative example is used to compare and illustrate the sodium difluorooxalatoborate and its preparation method disclosed in the present invention, and includes most of the operating steps in Example 16, except that:

[0193] Sodium hydroxide was used to replace compound 5 for the reaction.

[0194] Comparative Example 14

[0195] This comparative example is used to compare and illustrate the sodium monofluorophosphate and the preparation method thereof disclosed in the present invention, and includes most of the operating steps in Example 17, except that:

[0196] Sodium hydroxide was used to replace compound 5 for the reaction.

[0197] Comparative Example 15

[0198] This comparative example is used to compare and illustrate the sodium bis(oxalatoborate) and preparation method thereof disclosed in the present invention, and includes most of the operation steps in Example 18, except that:

[0199] Sodium hydroxide was used to replace compound 5 for the reaction.

[0200] Comparative Example 16

[0201] This comparative example is used to compare and illustrate the sodium tetrafluoroborate and the preparation method thereof disclosed in the present invention, and includes most of the operating steps in Example 19, except that:

[0202] Sodium hydroxide was used to replace compound 5 for the reaction.

[0203] Performance Testing

[0204] The lithium difluorophosphate and sodium difluorophosphate prepared in the above examples and comparative examples were tested for purity. At the same time, the yield of lithium difluorophosphate was calculated based on the obtained lithium difluorophosphate or sodium difluorophosphate and the raw material and filled in Table 1.

[0205] Table 1

[0206]

[0207]

[0208] From the test results of Examples 1 to 4 and Examples 8 to 11, it can be seen that when the compound shown in Structural Formula 1 is used as the reaction raw material, the reaction yield and purity are significantly low at a temperature of 90°C, indicating that the reactivity of the alkali metal difluorophosphate increases with increasing temperature, and the alkali metal difluorophosphate decomposes to a certain extent or undergoes unnecessary side reactions at too high a temperature, while the reaction yield and purity do not change much at 20°C and 60°C, and the presence or absence of a solvent has little effect on the reaction results.

[0209] From the test results of Examples 1, 5-7 and Comparative Examples 1-4, as well as the test results of Examples 8, 12-14 and Comparative Examples 7-10, Examples 15-19 and Comparative Examples 12-16, it can be seen that the reaction yield and product purity of the compound represented by Structural Formula 1 are higher than those of inorganic lithium salt and inorganic sodium salt. This is because the byproduct water in the comparative example reacts with M + The activity of Y is higher than that of the byproduct of the compound shown in formula 1, and water and M + Y reaction, resulting in product M + Y loss and generation of by-products that are difficult to remove.

[0210] From the test results of Example 1 and Comparative Examples 5 and 6, as well as the test results of Example 8 and Comparative Example 11, it can be seen that compared with alkyl lithium, lithium alcohol and sodium alcohol, the use of the compound shown in Structural Formula 1 as a reaction raw material can greatly improve the reaction yield and product purity. It is speculated that this is because the reaction efficiency of alkyl lithium, lithium alcohol and sodium alcohol is too low under the condition of no catalyst added, and then the reaction cannot be fully carried out, resulting in a decrease in the reaction yield. At the same time, the inadequate reaction also affects the purity of the final product. The compound shown in Structural Formula 1 can react normally under the condition of no catalyst to obtain alkali metal difluorophosphate, while reducing the introduction of impurities caused by the catalyst.

[0211] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. The present invention provides an alkali metal salt M + Y - The preparation method comprises the following steps: The compound shown in structural formula 1 is reacted with NH4 + Y - Reaction to obtain alkali metal salt M + Y - ; The compound shown in structural formula 1 and NH4 + Y - The reaction temperature is 10°C~160°C, the pressure is -0.1~0.3MPa, and the reaction time is 6~24h; M + Selected from K + 、Na + and Li + One or more of; Y - Selected from PO2F2 - 、FSI - DFOB - PO3F 2- 、BOB - 、BF4 - One or more of; Structural formula 1 in, A is selected from the functional group shown in Structural Formula 2 or the functional group shown in Structural Formula 3; E is selected from Li, Na or K; Structural formula 2 Wherein, R1 is selected from alkanes having 1 to 5 carbon atoms, aromatic hydrocarbons having 6 to 12 carbon atoms and their derivatives, cyclic carbonates having 3 to 6 carbon atoms and their derivatives; Structural formula 3 Wherein, R2 is selected from a nitrogen-containing heterocyclic ring having 3 to 6 carbon atoms.

2. The alkali metal salt M according to claim 1 + Y - The preparation method is characterized in that In structural formula 2, R1 is selected from alkanes having 1 to 5 carbon atoms, aromatic hydrocarbons and halogenated aromatic hydrocarbons having 6 to 12 carbon atoms, and cyclic carbonates having 3 to 6 carbon atoms.

3. The alkali metal salt M according to claim 1 + Y - The preparation method is characterized in that In structural formula 3, R2 is selected from an imidazole group, an oxazolidinone group or an oxathiazolidinyl group having 3 to 6 carbon atoms.

4. The alkali metal salt M according to claim 1 + Y - The preparation method is characterized in that The compound represented by structural formula 1 is selected from one or more of the following compounds: 。 5. The alkali metal salt M according to claim 1 + Y - The preparation method is characterized in that The compound represented by the structural formula 1 and NH4 + Y - The reaction is carried out in a solvent-free system or in a non-aqueous solvent system.

6. The alkali metal salt M according to claim 5 + Y - The preparation method is characterized in that The compound represented by the structural formula 1 and NH4 + Y - The reaction is carried out in a non-aqueous solvent system at a reaction temperature of 60°C to 160°C, a pressure of 0.05 to 0.3 MPa, and a reaction time of 6 to 24 hours. After the reaction, by-products and solvents are removed by filtration and distillation to obtain a product containing an alkali metal salt M + Y - of crude product.

7. The alkali metal salt M according to claim 5 + Y - The preparation method is characterized in that The compound represented by the structural formula 1 and NH4 + Y - The reaction is carried out in a solvent-free system, wherein the compound represented by the structural formula 1 is reacted with NH4 + Y - The mixture is evenly mixed by ball milling under a protective atmosphere, and the mixture is put into a reactor. The reaction temperature is 20°C~150°C, the pressure is -0.1~0.1MPa, and the reaction time is 6~24h to obtain a crude product containing alkali metal salt.

8. The alkali metal salt M according to claim 1 + Y - The preparation method is characterized in that The alkali metal salt M is obtained by reaction + Y - The crude product containing alkali metal salt M is treated with a non-aqueous solvent + Y - The crude product is recrystallized to contain alkali metal salt M + Y - The weight ratio of the crude product to the non-aqueous solvent is 1: (1-10), the dissolution temperature is 20°C-60°C, the recrystallization temperature is -10°C-20°C, and the crystals obtained by recrystallization are further vacuum dried to obtain the alkali metal salt M + Y - The drying temperature is 40℃~60℃, the drying vacuum degree is -98KPa~-99.5KPa, and the drying time is controlled at 6h~8h.

9. An electrolyte, characterized in that: The invention comprises a solvent, an electrolyte salt and an additive, wherein the additive comprises an alkali metal salt M prepared by the preparation method according to any one of claims 1 to 8. + Y - .

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