阅读说明：本技术 一种六氟磷酸锂的制备方法 (Preparation method of lithium hexafluorophosphate ) 是由 汪许诚 王小龙 于 2021-01-12 设计创作，主要内容包括：本发明公开了一种六氟磷酸锂的制备方法,其包括如下步骤：(1)将五氯化磷与第一非质子有机胺混合,形成能够溶解于第一非质子有机胺中的五氯化磷有机胺配合物,得到五氯化磷有机胺配合物的混合物；然后向五氯化磷有机胺配合物的混合物中加入有机胺氟化剂,与五氯化磷有机胺配合物进行氟氯取代反应,生成五氟化磷有机胺配合物；(2)将氟化锂分散在第二非质子有机胺中,制成氟化锂混合物；(3)将五氟化磷有机胺配合物与氟化锂混合物混合,反应生成六氟磷酸锂配合物,分离,制成六氟磷酸锂；该方法操作简单,安全环保,且反应过程可控、成本低,收率以及纯度较为理想,适于工业化应用。(The invention discloses a preparation method of lithium hexafluorophosphate, which comprises the following steps: (1) mixing phosphorus pentachloride and first aprotic organic amine to form a phosphorus pentachloride organic amine complex capable of being dissolved in the first aprotic organic amine to obtain a mixture of the phosphorus pentachloride organic amine complex; then adding an organic amine fluorinating agent into the mixture of the phosphorus pentachloride organic amine complex, and carrying out fluorine-chlorine substitution reaction with the phosphorus pentachloride organic amine complex to generate a phosphorus pentafluoride organic amine complex; (2) dispersing lithium fluoride in second aprotic organic amine to prepare a lithium fluoride mixture; (3) mixing a phosphorus pentafluoride organic amine complex with a lithium fluoride mixture, reacting to generate a lithium hexafluorophosphate complex, and separating to prepare lithium hexafluorophosphate; the method is simple to operate, safe and environment-friendly, controllable in reaction process, low in cost, ideal in yield and purity, and suitable for industrial application.)

1. The preparation method of the lithium hexafluorophosphate is characterized by comprising the following steps of:

(1) mixing phosphorus pentachloride and first aprotic organic amine to form a phosphorus pentachloride organic amine complex capable of being dissolved in the first aprotic organic amine to obtain a mixture of the phosphorus pentachloride organic amine complex;

then adding an organic amine fluorinating agent into the mixture of the phosphorus pentachloride organic amine complex, and carrying out fluorine-chlorine substitution reaction with the phosphorus pentachloride organic amine complex to generate a phosphorus pentafluoride organic amine complex;

(2) dispersing lithium fluoride in second aprotic organic amine to prepare a lithium fluoride mixture;

(3) mixing the phosphorus pentafluoride organic amine complex with a lithium fluoride mixture, reacting to generate a lithium hexafluorophosphate complex, and separating to prepare the lithium hexafluorophosphate.

2. The method for producing lithium hexafluorophosphate according to claim 1, wherein in the step (1), the first aprotic organic amine is an aprotic tertiary amine having 3 to 10 carbon atoms.

3. The method for producing lithium hexafluorophosphate according to claim 2, wherein in the step (1), the first aprotic organic amine is triethylamine and/or N, N' -tetramethylethylenediamine.

4. The method for producing lithium hexafluorophosphate according to claim 1 or 2, wherein in the step (1), the organic amine fluorinating agent is a salt of an aprotic tertiary amine and hydrogen fluoride.

5. The method for preparing lithium hexafluorophosphate according to claim 4, wherein in the step (1), the organic amine fluorinating agent is triethylamine hydrogen fluoride and/or N, N, N ', N' -tetramethylethylenediamine hydrogen fluoride, and the triethylamine hydrogen fluoride has a structural formula:

n is 3 to 5;

the structural formula of the N, N, N ', N' -tetramethylethylenediamine hydrogen fluoride is as follows:

6. the method for preparing lithium hexafluorophosphate according to claim 1, wherein in the step (1), the phosphorus pentachloride in the mixture of phosphorus pentachloride organic amine complex is 10-50% by mass; and/or in the step (1), the fluorine-chlorine substitution reaction is carried out at-10 to 10 ℃.

7. The method for producing lithium hexafluorophosphate according to claim 1, wherein the second aprotic organic amine in the step (2) is the same as the first aprotic organic amine in the step (1); and/or in the step (2), the specific implementation manner of the step (2) is as follows: dispersing lithium fluoride in second aprotic organic amine under the action of a dispersing agent to prepare a lithium fluoride mixture, wherein the dispersing agent comprises polyethylene glycol with the molecular weight of 400-1000, and the addition amount of the dispersing agent is 0.1-5% of that of the lithium fluoride in percentage by mass.

8. The method for producing lithium hexafluorophosphate according to claim 1, wherein the reaction is performed at 5 to 10 ℃ in the step (3).

9. The method for producing lithium hexafluorophosphate according to claim 1, wherein in the step (3), the separation comprises filtration, concentration, crystallization and drying which are sequentially performed; the solvent adopted by the crystallization is alkyl carbonate solvent and/or alkyl ether solvent, the alkyl carbonate solvent is one or a combination of more of dimethyl carbonate, diethyl carbonate and methyl ethyl carbonate, and the alkyl ether solvent is 1, 2-dimethoxyethane and/or diethyl ether.

10. The method for producing lithium hexafluorophosphate according to claim 1, wherein the steps (1), (2) and (3) are performed in the presence of a protective gas, respectively.

Technical Field

The invention belongs to the field of lithium batteries, particularly relates to an electrolyte for a lithium battery, and particularly relates to a preparation method of lithium hexafluorophosphate.

Background

Lithium hexafluorophosphate (LiPF)₆) Is the most important component of the electrolyte, accounts for about 43 percent of the total cost of the electrolyte, and is mixed with LiBF₄、LiAsF₆、LiClO₄Compared with the electrolyte, the lithium ion battery has the most advantages in the aspects of solubility, conductivity, safety and environmental protection in an organic solvent, and becomes the lithium salt electrolyte with the widest application range at present.

The preparation method of lithium hexafluorophosphate mainly comprises two methods:

(1) the wet method is that lithium salt is dissolved in anhydrous hydrofluoric acid to form LiF-HF solution, and then PF is introduced₅Gas reaction for producing lithium hexafluorophosphateAnd (4) crystallizing. And separating and drying to obtain the product. The process flow is as follows: the method comprises treating LiF with anhydrous HF to form porous LiF, and introducing PF₅Reacting the gas to obtain a product;

(2) a solvent method, wherein lithium salt and alkali metal salt, ammonium salt or organic amine salt of fluorophosphoric acid react in an organic solvent, and are crystallized, so as to prepare a lithium hexafluorophosphate product;

however, these methods have some problems as follows: the solid-liquid fluorination reaction is uneven; the existence of pure gas phase reaction brings great hidden trouble to the reaction safety; the preparation process is complicated, which is not beneficial to simplifying the process and the like.

Disclosure of Invention

The invention aims to overcome the defects of the prior art and provide an improved method for preparing lithium hexafluorophosphate, which is simple to operate, safe and environment-friendly, controllable in reaction process, low in cost, ideal in yield and purity and suitable for industrial application.

In order to achieve the purpose, the invention adopts the technical scheme that:

a preparation method of lithium hexafluorophosphate comprises the following steps:

(1) mixing phosphorus pentachloride and first aprotic organic amine to form a phosphorus pentachloride organic amine complex capable of being dissolved in the first aprotic organic amine to obtain a mixture of the phosphorus pentachloride organic amine complex;

then adding an organic amine fluorinating agent into the mixture of the phosphorus pentachloride organic amine complex, and carrying out fluorine-chlorine substitution reaction with the phosphorus pentachloride organic amine complex to generate a phosphorus pentafluoride organic amine complex;

(2) dispersing lithium fluoride in second aprotic organic amine to prepare a lithium fluoride mixture;

(3) mixing the phosphorus pentafluoride organic amine complex with a lithium fluoride mixture, reacting to generate a lithium hexafluorophosphate complex, and separating to prepare the lithium hexafluorophosphate.

According to some preferred aspects of the present invention, in the step (1), the first aprotic organic amine is an aprotic tertiary amine having 3 to 10 carbon atoms.

According to some preferred and specific aspects of the present invention, in step (1), the first aprotic organic amine is triethylamine and/or N, N' -tetramethylethylenediamine.

According to some preferred aspects of the invention, in step (1), the organic amine fluorinating agent is a salt synthesized from an aprotic tertiary amine and hydrogen fluoride.

According to some preferred and specific aspects of the present invention, in step (1), the organic amine fluorinating agent is triethylamine hydrogen fluoride and/or N, N' -tetramethylethylenediamine hydrogen fluoride, and the triethylamine hydrogen fluoride has a formula of:

n is 3 to 5;

the structural formula of the N, N, N ', N' -tetramethylethylenediamine hydrogen fluoride is as follows:

according to some preferred aspects of the present invention, in the step (1), the phosphorus pentachloride organic amine complex mixture contains 10% to 50% by mass of phosphorus pentachloride.

According to some preferred aspects of the present invention, in the step (1), the fluorine-chlorine substitution reaction is performed at-10 to 10 ℃.

According to some preferred aspects of the present invention, the second aprotic organic amine in step (2) may be the same as the first aprotic organic amine in step (1), i.e., both may preferably employ the same aprotic organic amine.

According to some preferred aspects of the present invention, in step (2), the specific implementation manner of step (2) is: dispersing lithium fluoride in second aprotic organic amine under the action of a dispersing agent to prepare a lithium fluoride mixture, wherein the dispersing agent comprises polyethylene glycol (PEG) with the molecular weight of 400-1000, and the addition amount of the dispersing agent is 0.1-5% of that of the lithium fluoride in percentage by mass.

According to some preferred aspects of the invention, in step (2), the lithium fluoride is milled to form a powdered lithium fluoride, which is then mixed with a dispersant and a second aprotic organic amine to form a lithium fluoride mixture.

According to some preferred aspects of the present invention, in the step (2), anhydrous lithium fluoride is used as the lithium fluoride.

According to some preferred and specific aspects of the invention, the dispersant is polyethylene glycol 400 or polyethylene glycol 800.

According to some preferred aspects of the present invention, in the step (3), the reaction is performed at 5 to 10 ℃. Further, in the step (3), the reaction is carried out at the temperature of 8-10 ℃. According to a particular aspect of the invention, in step (3), the reaction is carried out at 10 ℃.

According to some preferred aspects of the present invention, in the step (3), the separation comprises filtration, concentration, crystallization and drying, which are sequentially performed; wherein the solvent adopted by the crystallization is alkyl carbonate solvent and/or alkyl ether solvent, the alkyl carbonate solvent is one or a combination of more of dimethyl carbonate (DMC), diethyl carbonate and methyl ethyl carbonate, and the alkyl ether solvent is 1, 2-Dimethoxyethane (DME) and/or diethyl ether (Et)₂O)。

According to a preferred aspect of the present invention, the solvent used for the crystallization is 1, 2-Dimethoxyethane (DME).

According to some preferred aspects of the present invention, the alkyl carbonate-based solvent and/or the alkyl ether-based solvent each have a moisture content of less than 10ppm and a purity of more than 99.95%.

According to some preferred aspects of the present invention, the step (1), the step (2), and the step (3) are respectively performed in the presence of a protective gas including nitrogen, argon, or the like.

According to the present invention, in the step (3), the purity of the lithium hexafluorophosphate produced is 99.95% or more, the moisture content is less than 20ppm, and the free acid is less than 10 ppm.

According to some preferred and specific aspects of the present invention, the method for preparing lithium hexafluorophosphate comprises the steps of:

under the protection of protective gas, mixing phosphorus pentachloride and first aprotic organic amine, after completely dissolving, dripping an organic amine fluorinating agent at the temperature of-10-0 ℃, after finishing dripping, carrying out heat preservation reaction at the temperature of 1-10 ℃, and filtering to remove hydrochloride to obtain a mixture of phosphorus pentafluoride organic amine complexes;

under the protection of protective gas, grinding anhydrous lithium fluoride in a ball mill to prepare powdery anhydrous lithium fluoride, and then mixing the anhydrous lithium fluoride with a dispersant and a second aprotic organic amine to prepare a lithium fluoride mixture;

adding a mixture of phosphorus pentafluoride organic amine complexes into a lithium fluoride mixture at the temperature of 5-10 ℃ under the protection of protective gas, carrying out heat preservation reaction at the temperature of 8-10 ℃ to generate lithium hexafluorophosphate organic amine complexes dissolved in aprotic organic amine, filtering to remove unreacted lithium fluoride, concentrating filtrate to obtain a lithium hexafluorophosphate crude product, adding a solvent adopted for recrystallization into the lithium hexafluorophosphate crude product, and filtering, concentrating, crystallizing and drying to prepare the lithium hexafluorophosphate.

In the invention, the lithium hexafluorophosphate organic amine complex contained in the lithium hexafluorophosphate crude product can be combined with different amounts of aprotic organic amine, is relatively unstable, and can be separated under the condition of reduced pressure concentration to form the lithium hexafluorophosphate of the invention.

According to some preferred aspects of the present invention, the drying is performed at 20 to 30 ℃ under a vacuum of 1 to 5 mmHg.

Due to the application of the technical scheme, compared with the prior art, the invention has the following advantages:

the invention innovatively adopts the aprotic organic amine as a complexing agent and a solvent, so that the phosphorus pentachloride in a solid form can form a phosphorus pentachloride organic amine complex which can be dissolved in the aprotic organic amine, further, the fluorine-chlorine substitution reaction can be carried out in a liquid phase, the uniformity of the reaction is ensured, meanwhile, the generated phosphorus pentafluoride (colorless, stink and extremely strong in irritation) also exists in a complex form, the safety problem of the phosphorus pentafluoride in a gas form in the reaction process is avoided, then, the lithium fluoride is dispersed in the aprotic organic amine, so that the reaction of the lithium fluoride and the phosphorus pentafluoride is carried out in the liquid phase, the high selectivity and the safety of the reaction are ensured, the acid value of a product can be further controlled, the reaction time is shortened, and the yield and the quality of a target product are improved.

The method has the advantages of simple operation, safety, environmental protection, controllable reaction process, low cost, ideal yield and purity, and suitability for industrial application.

Detailed Description

The above-described scheme is further illustrated below with reference to specific examples; it is to be understood that these embodiments are provided to illustrate the general principles, essential features and advantages of the present invention, and the present invention is not limited in scope by the following embodiments; the implementation conditions used in the examples can be further adjusted according to specific requirements, and the implementation conditions not indicated are generally the conditions in routine experiments.

Not specifically illustrated in the following examples, all starting materials are commercially available or prepared by methods conventional in the art.

Example 1

Under the protection of nitrogen, a 1000ml four-neck flask is added with phosphorus pentachloride solid (PCl)₅)210g (1mol) of triethylamine and 500ml of triethylamine are dissolved completely, and triethylamine trihydrofluoride (Et) is slowly added dropwise at-5 DEG C₃N^.3HF)285g (1.67mol), dripping off after 2 hours, keeping the temperature at 5 ℃ for 4 hours, and filtering to remove hydrochloride to obtain the mixed liquid of the phosphorus pentafluoride triethylamine complex.

Under the protection of nitrogen, 30g (1.156mol) of anhydrous lithium fluoride LiF was weighed and added to a ball mill to be crushed for 0.5 hour to obtain anhydrous lithium fluoride powder, and the obtained powder, 1.5g of PEG400 dispersant and 100ml of triethylamine were added to a 2000ml flask and stirred for 0.5 hour to obtain a lithium fluoride mixture.

And slowly adding the mixed solution of the phosphorus pentafluoride triethylamine complex into a lithium fluoride mixture at 5 ℃ under nitrogen atmosphere, dropwise adding the mixed solution for 3 hours, keeping the temperature at 10 ℃ for 4 hours, filtering to remove unreacted lithium fluoride, and concentrating the filtrate under reduced pressure to obtain 154g of a lithium hexafluorophosphate crude product.

Under the protection of nitrogen, 1000ml of dimethyl carbonate (purity 99.98 percent and moisture 8ppm) is added into the crude product at 20 ℃ for full dissolution and filtration, and the filtrate is concentrated and crystallized to obtain 128g of lithium hexafluorophosphate semi-finished product. Controlling the temperature at 30 ℃, and drying under vacuum of 5mmHg for 24 hours to obtain 119.8g of white lithium hexafluorophosphate finished product, wherein the yield is 78.78%, the purity is 99.965%, the moisture content is 5ppm, and the acidity (calculated by HF) is 2.5 ppm.

Example 2

Under the protection of nitrogen, a 1000ml four-neck flask is added with phosphorus pentachloride solid (PCl)₅)210g (1mol) of triethylamine and 500ml of triethylamine are dissolved completely, and triethylamine trihydrofluoride (Et) is slowly added dropwise at-5 DEG C₃N^.3HF)285g (1.67mol), dripping off after 2 hours, keeping the temperature at 5 ℃ for 4 hours, and filtering to remove hydrochloride to obtain the mixed liquid of the phosphorus pentafluoride triethylamine complex.

Under the protection of nitrogen, 30g (1.156mol) of anhydrous lithium fluoride LiF was weighed and added to a ball mill to be crushed for 0.5 hour to obtain anhydrous lithium fluoride powder, and the obtained powder, 1.5g of PEG400 dispersant and 100ml of triethylamine were added to a 2000ml flask and stirred for 0.5 hour to obtain a lithium fluoride mixture.

And slowly adding the mixed solution of the phosphorus pentafluoride triethylamine complex into a lithium fluoride mixture at 5 ℃ under nitrogen atmosphere, dropwise adding the mixed solution for 3 hours, keeping the temperature at 10 ℃ for 4 hours, filtering to remove unreacted lithium fluoride, and concentrating the filtrate under reduced pressure to obtain 155g of a lithium hexafluorophosphate crude product.

Under the protection of nitrogen, 1000ml of diethyl carbonate (purity 99.98% and water content 8ppm) is added into the crude product at 20 ℃ for full dissolution and filtration, and the filtrate is concentrated and crystallized to obtain 129g of lithium hexafluorophosphate semi-finished product. Controlling the temperature at 30 ℃, and drying under vacuum for 24 hours under 5mmHg to obtain 119g of white lithium hexafluorophosphate finished product, wherein the yield is 78.25%, the purity is 99.956%, the moisture content is 5ppm, and the acidity (calculated by HF) is 5 ppm.

Example 3

Under the protection of nitrogen, a 1000ml four-neck flask is added with phosphorus pentachloride solid (PCl)₅)210g (1mol), TMEDA500ml, after complete dissolution, N, N, N ', N' -tetramethylethylenediamine hydrogen fluoride (TMEDA) was slowly added dropwise at-5 deg.C^.2HF)290g (2.5mol), dripping for 2 hours, keeping the temperature at 5 ℃ for 4 hours, filtering and removing hydrochloride to obtain the mixed liquid of the phosphorus pentafluoride N, N, N ', N' -tetramethyl ethylenediamine complex.

Under the protection of nitrogen, 30g (1.156mol) of anhydrous lithium fluoride LiF was weighed and added to a ball mill to be crushed for 0.5 hour to obtain anhydrous lithium fluoride powder, and the obtained powder, 1.5g of PEG400 dispersant and 100ml of TMEDA were added to a 2000ml flask and stirred for 0.5 hour to obtain a lithium fluoride mixture.

And slowly adding the mixed solution of the phosphorus pentafluoride N, N, N ', N' -tetramethylethylenediamine complex into a lithium fluoride mixture at 5 ℃ under a nitrogen atmosphere, dropwise adding the mixture for 3 hours, keeping the temperature at 10 ℃ for 4 hours, filtering to remove unreacted lithium fluoride, and concentrating the filtrate under reduced pressure to obtain 157g of a crude lithium hexafluorophosphate product.

Under the protection of nitrogen, 1000ml of diethyl carbonate DEC (purity 99.98% and water content 8ppm) is added into the crude product at 20 ℃ for full dissolution and filtration, and the filtrate is concentrated and crystallized to obtain 129g of lithium hexafluorophosphate semi-finished product. Controlling the temperature at 30 ℃, and drying in vacuum for 24 hours under 5mmHg to obtain 110g of white lithium hexafluorophosphate finished product, wherein the yield is 72.33%, the purity is 99.96%, the moisture content is 8ppm, and the acidity (calculated by HF) is 5 ppm.

Example 4

Under the protection of nitrogen, a 1000ml four-neck flask is added with phosphorus pentachloride solid (PCl)₅)210g (1mol) of triethylamine 500ml, after complete dissolution triethylamine trihydrofluoride (Et) was slowly added dropwise at-5 ℃₃N^.3HF)285g (1.67mol), dripping off after 2 hours, keeping the temperature at 5 ℃ for 4 hours, and filtering to remove hydrochloride to obtain the mixed liquid of the phosphorus pentafluoride triethylamine complex.

Under the protection of nitrogen, 30g (1.156mol) of anhydrous lithium fluoride LiF was weighed and added to a ball mill to be crushed for 0.5 hour to obtain anhydrous lithium fluoride powder, and the obtained powder, 1.5g of PEG400 dispersant and 100ml of triethylamine were added to a 2000ml flask and stirred for 0.5 hour to obtain a lithium fluoride mixture.

And slowly adding the mixed solution of the phosphorus pentafluoride triethylamine complex into a lithium fluoride mixture at 5 ℃ under nitrogen atmosphere, dropwise adding the mixed solution for 3 hours, keeping the temperature at 10 ℃ for 4 hours, filtering to remove unreacted lithium fluoride, and concentrating the filtrate under reduced pressure to obtain 158g of a lithium hexafluorophosphate crude product.

Under the protection of nitrogen, 1000ml of 1, 2-dimethoxyethane DME (purity 99.98%, moisture 10ppm) is added into the crude product at 20 ℃ for full dissolution and filtration, and 135g of lithium hexafluorophosphate semi-finished product is obtained by concentrating and crystallizing the filtrate. Controlling the temperature at 30 ℃, and drying under vacuum of 5mmHg for 24 hours to obtain the finished white lithium hexafluorophosphate 126.2g with the yield of 83 percent, the purity of 99.975 percent, the moisture of 8ppm and the acidity (calculated by HF) of 3.6 ppm.

Example 5

Under the protection of nitrogen, a 1000ml four-neck flask is added with phosphorus pentachloride solid (PCl)₅)210g (1mol), TMEDA500ml, after complete dissolution, N, N, N ', N' -tetramethylethylenediamine hydrogen fluoride (TMEDA) was slowly added dropwise at-5 deg.C^.2HF)290g (2.5mol), dripping for 2 hours, keeping the temperature at 5 ℃ for 4 hours, filtering and removing hydrochloride to obtain the mixed liquid of the phosphorus pentafluoride N, N, N ', N' -tetramethyl ethylenediamine complex.

Under the protection of nitrogen, 30g (1.156mol) of anhydrous lithium fluoride LiF was weighed and added to a ball mill to be crushed for 0.5 hour to obtain anhydrous lithium fluoride powder, and the obtained powder, 1.5g of PEG400 dispersant and 100ml of TMEDA were added to a 2000ml flask and stirred for 0.5 hour to obtain a lithium fluoride mixture.

And slowly adding the mixed solution of the phosphorus pentafluoride N, N, N ', N' -tetramethylethylenediamine complex into a lithium fluoride mixture at 5 ℃ under a nitrogen atmosphere, dropwise adding the mixture for 3 hours, keeping the temperature at 10 ℃ for 4 hours, filtering to remove unreacted lithium fluoride, and concentrating the filtrate under reduced pressure to obtain 156g of a lithium hexafluorophosphate crude product.

Under the protection of nitrogen, 1000ml of 1, 2-dimethoxyethane DME (purity 99.98 percent, moisture 10ppm) is added into the crude product at 20 ℃ for full dissolution and filtration, and 138g of lithium hexafluorophosphate semi-finished product is obtained by concentrating and crystallizing the filtrate. Controlling the temperature at 30 ℃, and drying in vacuum for 24 hours under 5mmHg to obtain 129g of white lithium hexafluorophosphate finished product, wherein the yield is 84.84%, the purity is 99.97%, the moisture content is 8ppm, and the acidity (calculated by HF) is 3 ppm.

The above embodiments are merely illustrative of the technical ideas and features of the present invention, and the purpose thereof is to enable those skilled in the art to understand the contents of the present invention and implement the present invention, and not to limit the protection scope of the present invention. All equivalent changes and modifications made according to the spirit of the present invention should be covered within the protection scope of the present invention.

The endpoints of the ranges and any values disclosed herein are not limited to the precise range or value, and such ranges or values should be understood to encompass values close to those ranges or values. For ranges of values, between the endpoints of each of the ranges and the individual points, and between the individual points may be combined with each other to give one or more new ranges of values, and these ranges of values should be considered as specifically disclosed herein.