CN112456465A - Preparation method of lithium difluorophosphate - Google Patents
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- CN112456465A CN112456465A CN202011440800.7A CN202011440800A CN112456465A CN 112456465 A CN112456465 A CN 112456465A CN 202011440800 A CN202011440800 A CN 202011440800A CN 112456465 A CN112456465 A CN 112456465A
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Abstract
A preparation method of lithium difluorophosphate comprises the following steps: (1) mixing lithium phosphate and lithium bicarbonate in an organic solvent at normal temperature; (2) after the materials are uniformly mixed, heating to a certain temperature, and introducing phosphorus pentafluoride for reaction to obtain a lithium difluorophosphate solution; (3) adding excessive alkaline lithium salt into lithium difluorophosphate solution for reaction and filtering, filtering out solids after full reaction, concentrating and crystallizing filtrate, and filtering out solution after crystallization is finished; (4) and transferring the crystal into an oven, and drying under the protection of nitrogen to obtain a high-purity lithium difluorophosphate product. The preparation method has wide raw material source and simple process; the phosphorus pentafluoride has high activity and quick reaction, the product lithium difluorophosphate is dissolved in an organic solvent (the reactant lithium phosphate is insoluble with lithium dihydrogen phosphate) in the reaction process, the reaction balance is constantly shifted to the right, and the reaction is thorough; the by-product is single, the amount is small, the recovery is easy, the purity of the obtained lithium difluorophosphate is high, and the use requirement of the battery can be met.
Description
Technical Field
The invention belongs to the technical field of lithium ion batteries, and particularly relates to a preparation method of lithium difluorophosphate.
Background
Lithium difluorophosphate is used as an additive of lithium battery electrolyte, can be subjected to oxidation-reduction reaction on the surface of an electrode in preference to the electrolyte to generate a layer of stable and compact protective film to protect the electrode, so that the cycle performance of the battery is improved, the service life is prolonged, the industrial value is high, and the application prospect is good.
The patent with the application number of CN2017111369615 discloses a method for rapidly preparing lithium difluorophosphate by taking lithium hexafluorophosphate and lithium carbonate as raw materials and ultrapure water as a catalyst, wherein the reaction is not easy to control, a plurality of byproducts are generated, and the lithium difluorophosphate is difficult to purify; in Japanese patent No. JP2005219994, lithium hexafluorophosphate and silicon dioxide are used as raw materials to synthesize lithium difluorophosphate, and the method is slow in reaction, long in period and not beneficial to industrial production; patent No. CN108640096B discloses a method for preparing difluorophosphoric acid and lithium difluorophosphate, which has complex reaction, and the prepared lithium difluorophosphate has many impurities and is not easy to purify.
In conclusion, the existing preparation method of lithium difluorophosphate has poor effect, and restricts the industrialization process of lithium difluorophosphate.
Disclosure of Invention
In order to overcome the defects in the prior art, the invention provides a simple and rapid preparation method of lithium difluorophosphate with high purity of the obtained product.
In order to solve the technical problems, the invention adopts the following technical scheme: a preparation method of lithium difluorophosphate comprises the following steps:
(1) at ambient temperature, lithium phosphate (Li)3PO4) With lithium dihydrogen carbonate (LiH)2PO4) Mixing in an organic solvent;
(2) after the materials are mixed evenly, the mixture is heated to a certain temperature and then phosphorus Pentafluoride (PF) is introduced5) Reacting to obtain a lithium difluorophosphate solution;
(3) adding excessive alkaline lithium salt into lithium difluorophosphate solution for reaction and filtering, filtering out solids after full reaction, concentrating and crystallizing filtrate, and filtering out solution after crystallization is finished;
(4) and transferring the crystal into an oven, and drying under the protection of nitrogen to obtain a high-purity lithium difluorophosphate product.
The raw materials lithium phosphate and lithium dihydrogen carbonate in the step (1) are both battery grade, and the purity is not lower than 99.9%; the main content of the phosphorus pentafluoride is not less than 99 percent.
The molar ratio of lithium phosphate to lithium bicarbonate to phosphorus pentafluoride is 1: (1-1.3): 2.
the organic solvent in the step (1) is selected from one or more of ethylene glycol dimethyl ether, ethylene glycol diethyl ether, methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol, methyl acetate, ethyl acetate, propyl acetate, butyl acetate, methyl propionate, ethyl propionate, dimethyl carbonate, diethyl carbonate, acetone and acetonitrile.
The temperature heated in the step (2) is 40-100 ℃; the reaction time is 0.5-3 h.
The alkaline lithium salt is lithium carbonate, lithium bicarbonate, lithium hydroxide or lithium oxide.
Concentrating and crystallizing in the step (3) to be vacuum concentration; the temperature of the concentration under reduced pressure does not exceed 60 ℃.
The organic solvent has a moisture content of less than 60 ppm.
The drying temperature in the step (4) is 80-150 ℃.
By adopting the technical scheme, the preparation method has wide raw material source and simple process; the phosphorus pentafluoride has high activity and quick reaction, the product lithium difluorophosphate is dissolved in an organic solvent (the reactant lithium phosphate is insoluble with lithium dihydrogen phosphate) in the reaction process, the reaction balance is constantly shifted to the right, and the reaction is thorough; the by-product is single, the amount is small, the recovery is easy, the purity of the obtained lithium difluorophosphate is high, and the use requirement of the battery can be met.
Drawings
FIG. 1 is a process flow diagram of the present invention;
figure 2 is an XRD spectrum of lithium difluorophosphate prepared in example 1.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
The invention provides a preparation method of lithium difluorophosphate, which comprises the following steps as shown in figure 1: mixing lithium phosphate and lithium dihydrogen phosphate in an organic solvent, and introducing phosphorus pentafluoride gas to react to obtain a lithium difluorophosphate solution (reaction solution 1).
The reaction principle of the invention is as follows: li3PO4+LiH2PO4+2PF5=4LiPO2F2+2 HF. The raw materials are bulk commodities in the battery industry and are convenient to purchase.
In the present invention, the sources of all raw materials are not particularly limited, and they may be commercially available.
Mixing lithium phosphate and lithium dihydrogen phosphate in an organic solvent; the purity of lithium phosphate and lithium dihydrogen phosphate is preferably not less than 99.9%; the molar ratio of lithium phosphate to lithium dihydrogen carbonate is preferably 1: (1 to 1.8), more preferably 1: (1.1 to 1.5), most preferably 1: (1.05-1.3); the organic solvent is preferably one or more of ethylene glycol dimethyl ether, ethylene glycol diethyl ether, methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol, methyl acetate, ethyl acetate, propyl acetate, butyl acetate, methyl propionate, ethyl propionate, dimethyl carbonate, diethyl carbonate, acetone and acetonitrile, and more preferably ethylene glycol dimethyl ether or ethyl acetate; the moisture content of the organic solvent is preferably less than 60ppm, more preferably less than 30ppm, still more preferably less than 10 ppm. Lithium dihydrogen phosphate is insoluble in organic solvent, and can be separated by filtration if the lithium dihydrogen phosphate is excessive, and the proper molar ratio can ensure that the lithium phosphate is reacted completely, and can not cause a great deal of raw material waste.
After mixing, heating and introducing phosphorus pentafluoride for reaction; the phosphorus pentafluoride purity is preferably not less than 99%; the molar ratio of lithium phosphate to phosphorus pentafluoride is preferably 1: 2; the temperature of the heating reaction is preferably 20-100 ℃, more preferably 40-80 ℃, and most preferably 50-70 ℃; the heating reaction time is preferably 0.5-3 h, and more preferably 0.8-2 h. At low temperature, the reaction activity of the raw materials is low, the reaction period is long, and the yield is low; at high temperature, the chemical reaction is fast, but the side reaction is increased, and the product lithium difluorophosphate is decomposed and deteriorated, so that the temperature is controlled within a certain range.
After the reaction, preferably cooling the reaction system, adding alkaline lithium salt, stirring the reaction solution 2 at a low temperature for full reaction, filtering, concentrating, crystallizing and drying to obtain lithium difluorophosphate; cooling, preferably to room temperature; the basic lithium salt is preferably lithium carbonate, lithium bicarbonate, lithium hydroxide or lithium oxide, and more preferably lithium carbonate; adding organic solvent, stirring at room temperature to dissolve completely, filtering, and removing solid; after filtration, the crystals are concentrated, preferably by concentration under reduced pressure; under the condition of a solvent, side reactions are easy to occur in the high-temperature concentration process, so that the purity of the product is low, and therefore, the temperature of the reduced pressure concentration is preferably not more than 60 ℃, and more preferably not more than 50 ℃; concentrating, crystallizing, and preferably drying to obtain high-purity lithium difluorophosphate; fig. 2 shows the XRD spectrum of the prepared high-purity lithium difluorophosphate. The drying temperature is preferably 80-150 ℃, more preferably 90-140 ℃, and further preferably 90-120 ℃; the drying is preferably carried out in a protective atmosphere; the protective atmosphere is preferably nitrogen.
According to the invention, lithium phosphate and lithium dihydrogen phosphate are mixed in an organic solvent, phosphorus pentafluoride is introduced for reaction to obtain lithium difluorophosphate, the preparation process is simple, the product is dissolved in the organic solvent, but the reactant is insoluble, the reaction is quicker and more thorough, the byproduct is single, the amount is small, the byproduct is easy to recover, the purity of the obtained lithium difluorophosphate is high, and the use requirement of the battery can be met.
In order to further illustrate the present invention, the following will describe the preparation method of lithium difluorophosphate provided by the present invention in detail with reference to the examples.
Example 1
At normal temperature, 29g of lithium phosphate and 27.3g of lithium dihydrogen phosphate (molar ratio is 1: 1.05) are mixed in 1080g of ethyl acetate (moisture is 10 ppm), the materials are uniformly mixed, the temperature is raised to 60 ℃, and phosphorus pentafluoride (63 g) is introduced for reaction for 1 hour. And cooling after the reaction is finished, adding excessive lithium carbonate, stirring for reaction, filtering out solids after full reaction, concentrating the filtrate at 45 ℃ under reduced pressure (-0.095 MPa) for crystallization, filtering out the solution after crystallization is finished, transferring the crystals into an oven, and drying at 90 ℃ under the protection of nitrogen to obtain the pure lithium difluorophosphate with the purity of 99.91 percent and the yield of 94.1 percent.
Example 2
At normal temperature, 29g of lithium phosphate and 28.6g of lithium dihydrogen phosphate (molar ratio is 1: 1.1) are mixed in 1080g of ethyl acetate (moisture is 10 ppm), the materials are uniformly mixed, the temperature is raised to 55 ℃, and phosphorus pentafluoride (63 g) is introduced for reaction for 1.8 hours. And cooling after the reaction is finished, adding excessive lithium carbonate, stirring for reaction, filtering out solids after full reaction, concentrating the filtrate at 55 ℃ under reduced pressure (-0.095 MPa) for crystallization, filtering out the solution after crystallization is finished, transferring the crystals into an oven, and drying at 100 ℃ under the protection of nitrogen to obtain the pure lithium difluorophosphate with the purity of 99.5% and the yield of 91.5%.
Example 3
At normal temperature, 29g of lithium phosphate and 33.8g of lithium dihydrogen phosphate (molar ratio is 1: 1.3) are mixed in 1080g of ethyl acetate (water content is 10 ppm), the materials are uniformly mixed, the temperature is raised to 70 ℃, and phosphorus pentafluoride (63 g) is introduced for reaction for 0.9 h. And cooling after the reaction is finished, adding excessive lithium carbonate, stirring for reaction, filtering out solids after full reaction, concentrating the filtrate at 45 ℃ under reduced pressure (-0.095 MPa) for crystallization, filtering out the solution after crystallization is finished, transferring the crystals into an oven, and drying at 110 ℃ under the protection of nitrogen to obtain the pure lithium difluorophosphate with the purity of 98.6% and the yield of 89.5%.
Comparative example 1
At normal temperature, 29g of lithium phosphate and 27.3g of lithium dihydrogen phosphate (molar ratio is 1: 1.05) are mixed in 1080g of ethyl acetate (moisture is 10 ppm), the materials are uniformly mixed, the temperature is raised to 100 ℃, and phosphorus pentafluoride (63 g) is introduced for reaction for 0.6 h. And cooling after the reaction is finished, adding excessive lithium carbonate, stirring for reaction, filtering out solids after full reaction, concentrating the filtrate at 45 ℃ under reduced pressure (-0.095 MPa) for crystallization, filtering out the solution after crystallization is finished, transferring the crystals into an oven, and drying at 90 ℃ under the protection of nitrogen to obtain the pure lithium difluorophosphate with the purity of 97.4% and the yield of 86.1%.
Comparative example 2
At normal temperature, 29g of lithium phosphate and 27.3g of lithium dihydrogen phosphate (molar ratio is 1: 1.05) are mixed in 1080g of ethyl acetate (moisture is 10 ppm), the materials are uniformly mixed, the temperature is raised to 60 ℃, and phosphorus pentafluoride (63 g) is introduced for reaction for 1 hour. And cooling after the reaction is finished, adding excessive lithium carbonate, stirring for reaction, filtering out solids after full reaction, concentrating the filtrate at 70 ℃ under reduced pressure (-0.095 MPa) for crystallization, filtering out the solution after crystallization is finished, transferring the crystals into an oven, and drying at 160 ℃ under the protection of nitrogen to obtain the pure lithium difluorophosphate with the purity of 98.8% and the yield of 90.3%.
The present embodiment is not intended to limit the shape, material, structure, etc. of the present invention in any way, and any simple modification, equivalent change and modification made to the above embodiments according to the technical spirit of the present invention are within the scope of the technical solution of the present invention.
Claims (9)
1. A preparation method of lithium difluorophosphate is characterized by comprising the following steps: the method comprises the following steps:
(1) at ambient temperature, lithium phosphate (Li)3PO4) With lithium dihydrogen carbonate (LiH)2PO4) Mixing in an organic solvent;
(2) after the materials are mixed evenly, the mixture is heated to a certain temperature and then phosphorus Pentafluoride (PF) is introduced5) Reacting to obtain a lithium difluorophosphate solution;
(3) adding excessive alkaline lithium salt into lithium difluorophosphate solution for reaction and filtering, filtering out solids after full reaction, concentrating and crystallizing filtrate, and filtering out solution after crystallization is finished;
(4) and transferring the crystal into an oven, and drying under the protection of nitrogen to obtain a high-purity lithium difluorophosphate product.
2. The method for preparing lithium difluorophosphate according to claim 1, wherein: the raw materials lithium phosphate and lithium dihydrogen carbonate in the step (1) are both battery grade, and the purity is not lower than 99.9%; the main content of the phosphorus pentafluoride is not less than 99 percent.
3. The method for preparing lithium difluorophosphate according to claim 1, wherein: the molar ratio of lithium phosphate to lithium bicarbonate to phosphorus pentafluoride is 1: (1-1.3): 2.
4. the method for preparing lithium difluorophosphate according to claim 1, wherein: the organic solvent in the step (1) is selected from one or more of ethylene glycol dimethyl ether, ethylene glycol diethyl ether, methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol, methyl acetate, ethyl acetate, propyl acetate, butyl acetate, methyl propionate, ethyl propionate, dimethyl carbonate, diethyl carbonate, acetone and acetonitrile.
5. The method for preparing lithium difluorophosphate according to claim 1, wherein: the temperature heated in the step (2) is 40-100 ℃; the reaction time is 0.5-3 h.
6. The method for preparing lithium difluorophosphate according to claim 1, wherein: the alkaline lithium salt is lithium carbonate, lithium bicarbonate, lithium hydroxide or lithium oxide.
7. The method for preparing lithium difluorophosphate according to claim 1, wherein: concentrating and crystallizing in the step (3) to be vacuum concentration; the temperature of the concentration under reduced pressure does not exceed 60 ℃.
8. The method according to claim 1, wherein the organic solvent has a moisture content of less than 60 ppm.
9. The method according to claim 1, wherein the temperature for drying in the step (4) is 80 to 150 ℃.
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN113184824A (en) * | 2021-05-12 | 2021-07-30 | 湖南博信新能源科技有限公司 | Preparation method of lithium difluorophosphate |
| CN114477122A (en) * | 2022-03-11 | 2022-05-13 | 滨州海川生物科技股份有限公司 | Preparation method of lithium difluorophosphate and lithium ion battery electrolyte |
| CN115321510A (en) * | 2022-08-30 | 2022-11-11 | 珠海正杏新材料科技有限公司 | Preparation method of lithium difluorophosphate |
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| CN109941982A (en) * | 2017-12-21 | 2019-06-28 | 江苏国泰超威新材料有限公司 | A kind of method of purification of difluorophosphate |
| CN112028047A (en) * | 2020-09-14 | 2020-12-04 | 湖南博信新能源科技有限公司 | Preparation method of lithium difluorophosphate |
| CN112028046A (en) * | 2020-09-09 | 2020-12-04 | 多氟多化工股份有限公司 | Preparation method of lithium difluorophosphate |
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| CN112028046A (en) * | 2020-09-09 | 2020-12-04 | 多氟多化工股份有限公司 | Preparation method of lithium difluorophosphate |
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Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN113184824A (en) * | 2021-05-12 | 2021-07-30 | 湖南博信新能源科技有限公司 | Preparation method of lithium difluorophosphate |
| CN113184824B (en) * | 2021-05-12 | 2022-10-11 | 湖南法恩莱特新能源科技有限公司 | Preparation method of lithium difluorophosphate |
| CN114477122A (en) * | 2022-03-11 | 2022-05-13 | 滨州海川生物科技股份有限公司 | Preparation method of lithium difluorophosphate and lithium ion battery electrolyte |
| CN115321510A (en) * | 2022-08-30 | 2022-11-11 | 珠海正杏新材料科技有限公司 | Preparation method of lithium difluorophosphate |
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