CN114085148A

CN114085148A - Preparation method and application of monofluoroethyl ethyl carbonate

Info

Publication number: CN114085148A
Application number: CN202010784182.1A
Authority: CN
Inventors: 张洪源; 王丽秀; 徐振堂; 秦雪; 杨金萍; 杨广亮; 徐颖; 李学楠
Original assignee: Tianjin Vocational Institute
Current assignee: Tianjin Vocational Institute
Priority date: 2020-08-06
Filing date: 2020-08-06
Publication date: 2022-02-25

Abstract

The invention discloses a preparation method and application of fluoroethyl ethyl carbonate, wherein the preparation method comprises the following steps: the preparation method comprises the steps of mixing monochloroethyl carbonate with a first organic solvent, adding methyl cucurbituril [6] serving as a phase transfer catalyst, uniformly mixing, heating to 50-120 ℃, adding potassium fluoride powder under the condition of keeping the temperature, reacting for 3-6 hours, standing and cooling to room temperature of 20-25 ℃, filtering and collecting filtrate, and carrying out reduced pressure distillation to obtain the monochloroethyl carbonate.

Description

Preparation method and application of monofluoroethyl ethyl carbonate

Technical Field

The invention belongs to the technical field of preparation of monofluoroethyl ethyl carbonate, and particularly relates to a preparation method and application of monofluoroethyl ethyl carbonate.

Background

The lithium ion battery is widely applied to various fields by taking the advantages of large specific capacity, long cycle life, no pollution and the like as the current hottest power supply, but the performance of the lithium ion battery is seriously reduced below zero, so that the application of the lithium ion battery in various fields and in various scenes is limited. The adoption of the additive is a common technical means for improving the performance of the lithium ion battery. When the problem that the low-temperature performance of the lithium battery is insufficient is solved, the additive plays a crucial role, for example, scholars of China mining university study the influence of N-N-dimethyl trifluoroacetamide on the low-temperature performance, and the DTA additive can improve the charging specific capacity, the initial coulomb efficiency and the capacity retention rate of the graphite electrode at room temperature and low temperature. Researchers at university of eastern science and Xiamen university respectively propose that 2 percent fluoroethylene carbonate added into a ternary system as an additive can effectively improve the low-temperature discharge capacity of the battery. However, the fluoroethylene carbonate is a five-membered ring structure, the melting point is 18 ℃, the freezing point of the electrolyte can be improved, the use in winter is inconvenient, and accidents such as pipeline blockage can often occur.

Disclosure of Invention

In view of the defects of the prior art, the invention aims to provide a preparation method of monofluoroethyl ethyl carbonate, which is a fluorine-containing additive with a ring-opening structure and a low freezing point and is beneficial to the operation of a battery at low temperature. The heterogeneous fluorination substitution reaction is catalyzed by adopting a novel phase transfer catalyst methyl cucurbituril [6], and a target product with higher yield is obtained.

The invention also aims to provide the application of the fluoroethyl ethyl carbonate as the additive in the electrolyte, and when the electrolyte added with the fluoroethyl ethyl carbonate is adopted in the lithium ion battery, the performance of lithium ions can be improved.

The purpose of the invention is realized by the following technical scheme.

The preparation method of the fluoroethyl ethyl carbonate comprises the following steps:

mixing monochloroethyl ethyl carbonate with a first organic solvent, adding methyl cucurbituril [6] serving as a phase transfer catalyst, uniformly mixing, heating to 50-120 ℃, adding potassium fluoride powder under the condition of keeping the temperature, reacting for 3-6 h, standing and cooling to room temperature of 20-25 ℃, filtering and collecting filtrate, and carrying out reduced pressure distillation to obtain the monochloroethyl ethyl carbonate, wherein the methyl cucurbituril [6] accounts for 0.5-5 wt% of the monochloroethyl ethyl carbonate, and the ratio of the potassium fluoride powder to the monochloroethyl ethyl carbonate is (0.1-1): 1.

in the technical scheme, the filter cake is washed by the first organic solvent, the first organic solvent is removed by rectification, and then the filter cake is mixed with the filtrate, and the fluoroethyl ethyl carbonate is obtained by reduced pressure distillation.

In the above technical scheme, the first organic solvent is dimethyl carbonate, diethyl carbonate, methyl tert-butyl ether or methyl ethyl carbonate.

In the technical scheme, the temperature of 50-120 ℃ is preferably 65-90 ℃.

In the technical scheme, the methyl cucurbituril [6] accounts for 1-3 wt% of the monochloroethyl ethyl carbonate.

In the technical scheme, the ratio of the monochloroethyl ethyl carbonate to the first organic solvent is (0.1-1) by mass: 1.

in the technical scheme, the potassium fluoride powder is added in three batches at intervals of 30 minutes.

The fluoroethyl ethyl carbonate is used as an additive in the electrolyte.

In the above technical solution, the electrolyte includes: lithium salt, a second organic solvent, fluoroethyl ethyl carbonate and an electrolyte additive, wherein the second organic solvent is one or a mixture of more of dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, ethylene carbonate, propylene carbonate and ethyl methyl carbonate, the electrolyte additive is one or a mixture of more of vinylene carbonate VC, fluoroethylene carbonate FEC, 1, 3-propane sultone PS, ethylene sulfate PCS, propylene sulfite, ethylene carbonate VEC, propylene sulfate, phenyl acetone, 1, 4-butane sultone, tris (trimethylsilane) phosphite ester, butylene sulfite and 1, 4-succinonitrile, the second organic solvent accounts for 60-96 wt% of the electrolyte, the electrolyte additive accounts for 0.2-5 wt% of the electrolyte, and the monofluoroethyl ethyl carbonate accounts for 0.2-5 wt% of the electrolyte.

In the technical scheme, the lithium salt is lithium hexafluorophosphate and/or lithium tetrafluoroborate, and the lithium salt in the electrolyte is 3-30 wt%.

In the above technical solution, the battery is a nickel-cobalt-manganese ternary system battery, including: the electrolyte comprises a positive electrode, a negative electrode, a diaphragm and the electrolyte, wherein the positive electrode material of the positive electrode is LiNi_xCo_yMn_1-x-yO₂Wherein x is more than or equal to 0.1 and less than or equal to 0.9, y is more than or equal to 0.1 and less than or equal to 0.9,1-x-y is more than or equal to 0, and the negative electrode is a metallic lithium sheet or a graphite carbon material.

The monofluoroethyl ethyl carbonate is a chain fluorine-containing carbonate compound, and is applied to the electrolyte additive, so that a layer of compact SEI film can be formed on the surface of an electrode, and the cycle performance and the low-temperature performance of the battery are improved.

Drawings

FIG. 1 is a nuclear magnetic spectrum of fluoroethyl ethyl carbonate obtained in example 2;

FIG. 2 shows the performance test of the corresponding battery of Table 2;

fig. 3 shows the performance test of the battery corresponding to table 4.

Detailed Description

The technical scheme of the invention is further explained by combining specific examples.

The drugs involved in the following examples are as follows:

diethyl monochlorocarbonate (99%, Shanghai Aladdin Biotechnology, Inc.), having the formula:

potassium fluoride (analytically pure, jinsha chemical ltd, new county);

diethyl carbonate (analytically pure, york chemical ltd);

methyl Cucurbituril [6] (98.5%, self-made, preparation method is described in Day A, Arnold A P, Blanch R J et al, Controlling Factors in The Synthesis of Current and Its Homologues [ J ]. The Journal of Organic chemistry.2001,66: 8094-;

polyethylene glycol 1000 (analytical grade, chemical technology ltd, de shan city);

crown ether 18 crown 6 (analytically pure, Hubeixin chemical Co., Ltd.).

Ternary nickel cobalt manganese materials (beidou materials ltd);

an electrolyte (Tianjin Taurus power supply materials Co., Ltd.);

n-methylpyrrolidone (Dingshenxin chemical Co., Ltd., Tianjin);

lithium tablets (ningde times new energy technology ltd);

diaphragm (Tianjin Karpt new energy science and technology, Inc.);

PVDF (Shandong Huaxia China new materials Co., Ltd.)

Example 1

in a flask with a stirrer, 400g of monochloroethyl ethyl carbonate is mixed with 700g of a first organic solvent, the first organic solvent is diethyl carbonate, 4g of methyl cucurbituril [6] serving as a phase transfer catalyst is gradually added under slow stirring, the mixture is uniformly mixed, the temperature is raised to 65 ℃, under the premise of keeping the temperature, 240g of potassium fluoride powder is added in batches (240g of potassium fluoride powder is added in three batches at intervals of 30 minutes and 80g each time), the reflux reaction is carried out for 5 hours, the mixture is kept stand and cooled to the room temperature of 20-25 ℃, filtrate is filtered and collected, a filter cake is washed by the first organic solvent, the first organic solvent is removed by rectification, the filtrate is mixed with the filtrate, and the monofluoroethyl ethyl carbonate is obtained by reduced pressure distillation, wherein the methyl cucurbituril [6] is 1 wt% of the monochloroethyl ethyl carbonate, the ratio of the potassium fluoride powder to the monochloroethyl ethyl carbonate is 240:400 in parts by mass, the ratio of monochloroethyl ethyl carbonate to the first organic solvent is 4:7 by mass.

The structural formula of the fluoroethyl ethyl carbonate is:

example 2

in a flask with a stirrer, 400g of monochloroethyl ethyl carbonate is mixed with 700g of first organic solvent, the first organic solvent is dimethyl carbonate, 12g of methyl cucurbituril [6] serving as a phase transfer catalyst is gradually added under slow stirring, the mixture is uniformly mixed, the temperature is raised to 90 ℃, under the premise of keeping the temperature, 240g of potassium fluoride powder is added in batches (240g of potassium fluoride powder is added in three batches at intervals of 30 minutes and 80g each time), the mixture is refluxed for 3 hours, the mixture is kept stand and cooled to the room temperature of 20-25 ℃, filtrate is filtered and collected, a filter cake is washed by the first organic solvent, the first organic solvent is removed by rectification, the filtrate is mixed, and the monofluoroethyl ethyl carbonate is obtained by reduced pressure distillation, wherein the methyl cucurbituril [6] is 3 wt% of the monochloroethyl ethyl carbonate, the ratio of the potassium fluoride powder to the monochloroethyl ethyl carbonate is 240:400 by mass fraction, the ratio of monochloroethyl ethyl carbonate to the first organic solvent is 4:7 by mass.

Nuclear magnetic hydrogen of examples 1 and 2The spectra are all:¹H-NMR(CDCl₃-d，400MHz):δ＝6.71(dq,1H, J_H-F＝46.4Hz,J_H-H＝6.6Hz,)；δ＝4.25(q,2H,J_H-H＝7.8Hz)；δ＝1.97(dd,3H,J_H-F＝25.4Hz, J_H-H＝6.6Hz,)；δ＝1.32(t,3H，J_H-H7.8 Hz). Mass spectrum EI-MS: and m/z is 136. The nuclear magnetic hydrogen spectrum is shown in the attached figure 1: the hydrogen atom No. 1 is closest to the fluorine atom and is strongly coupled by the fluorine atom, so the coupling constant reaches 46.4Hz, the distance F between the hydrogen atom No. 3 and the fluorine atom No. 1 is one C-C length longer than that of the hydrogen atom No. 1, the coupling degree is weakened, and the coupling constant is 25.4 Hz.

Example 3

The battery is a nickel-cobalt-manganese ternary system battery, and comprises: the lithium battery comprises a positive electrode, a negative electrode, a diaphragm and electrolyte, wherein the positive electrode is made of an OK nickel cobalt manganese NCM523 type ternary material, and the negative electrode is a round metal lithium sheet. Wherein N-methylpyrrolidone (NMP) is used as a solvent, polyvinylidene fluoride (PVDF) is used as a binder, and a carbon black conductive agent Super P is used as a conductive agent. According to the positive electrode material: conductive agent: adhesive agent: the positive electrode slurry was prepared in a mass ratio of 8:1:1:40 NMP. And (3) uniformly coating the anode slurry on a smooth aluminum foil with the thickness of 10mm by adopting a scraper to obtain the pole piece. And (4) drying the coated pole piece in a drying oven at 45 ℃ for 12 h. And tabletting by a tablet press to obtain the positive pole piece with a smooth and flat surface.

The electrolyte includes: the electrolyte comprises a lithium salt, a second organic solvent and an electrolyte additive, wherein the second organic solvent is 82 wt% of the electrolyte, the electrolyte additive is 4.5 wt% of the electrolyte, the lithium salt in the electrolyte is 13.5 wt%, the second organic solvent is a mixture of ethyl methyl carbonate, diethyl carbonate and ethylene carbonate, the mass ratio of the ethyl methyl carbonate, the diethyl carbonate and the ethylene carbonate is 1:1:1, the electrolyte additive is a mixture of vinylene carbonate VC, fluoroethylene carbonate FEC, 1, 3-propane sultone PS and ethylene sulfate PCS, the mass ratio of the vinylene carbonate VC, the fluoroethylene carbonate FEC, 1, 3-propane sultone PS and the ethylene sulfate PCS is 1:2:0.5:1, and the lithium salt is lithium hexafluorophosphate.

The CR2032 button cell is assembled in a glove box according to the sequence of an anode shell, an anode gasket, an anode, electrolyte, a diaphragm, electrolyte, a cathode gasket, an elastic sheet and a cathode shell. The CR2032 button cell was tested for charge and discharge using the wuhan blue CT3001A battery test system and the cantonese beyer test equipment limited model BTH-100 high and low temperature test chamber. The test is carried out at the normal temperature of 20-25 ℃, the set voltage is 3.0-4.2V, and the current density is 0.5C.

Example 4

This example is substantially the same as example 3, except that: the electrolyte includes: a lithium salt, a second organic solvent, the monofluoroethyl ethyl carbonate prepared in example 2, and an electrolyte additive. The contents of the lithium salt, the second organic solvent, the fluoroethyl ethyl carbonate, and the electrolyte additive in the electrolyte are shown in table 1.

TABLE 1

The performance test of the battery was performed while maintaining the same test conditions as in example 3. The batteries prepared in examples 3 and 4 were tested and the test results are shown in table 2.

TABLE 2

	Specific first discharge capacity (mAhg)^-1)	First week coulombic efficiency (%)
			Example 3 (blank)	153	92.16
Practice ofExample 4(+ 1%)	162	93.64
			Example 4(+ 2%)	166	94.32
Example 4(+ 3%)	160	93.02

Example 5

The battery is a nickel-cobalt-manganese ternary system battery, and comprises: the cathode comprises a cathode, an anode, a diaphragm and electrolyte, wherein the cathode is made of a nickel-cobalt-manganese NCM622 type ternary material, and the anode is made of graphite. Wherein N-methyl pyrrolidone is used as a solvent, polyvinylidene fluoride (PVDF) is used as a binder, and a carbon black conductive agent Super P is used as a conductive agent. According to the positive electrode material: conductive agent: adhesive NMP 8:1: 40 mass ratio to prepare a positive electrode slurry. And (3) uniformly coating the anode slurry on a smooth aluminum foil with the thickness of 10mm by adopting a scraper to obtain the pole piece. And (4) drying the coated pole piece in a drying oven at 45 ℃ for 12 h. And tabletting by a tablet press to obtain the positive pole piece with a smooth and flat surface.

The electrolyte includes: the electrolyte comprises a lithium salt, a second organic solvent and an electrolyte additive, wherein the second organic solvent is 83 wt% of the electrolyte, the electrolyte additive is 4 wt% of the electrolyte, the lithium salt in the electrolyte is 13 wt%, the second organic solvent is a mixture of dimethyl carbonate, ethyl methyl carbonate and ethylene carbonate, the mass ratio of the dimethyl carbonate, the ethyl methyl carbonate and the ethylene carbonate is 4:3:3, the electrolyte additive is a mixture of vinylene carbonate VC, fluoroethylene carbonate FEC, 1, 4-butane sultone and 1, 4-succinonitrile, the mass ratio of the vinylene carbonate VC, the fluoroethylene carbonate FEC, 1, 4-butane sultone and 1, 4-succinonitrile is 1:2:0.5:0.5, and the lithium salt is lithium hexafluorophosphate.

The CR2032 button cell is assembled in a glove box according to the sequence of an anode shell, an anode gasket, an anode, electrolyte, a diaphragm, electrolyte, a cathode gasket, an elastic sheet and a cathode shell. The CR2032 button cell was tested for charge and discharge using the wuhan blue CT3001A battery test system and the cantonese beyer test equipment limited model BTH-100 high and low temperature test chamber. The test is carried out at-10 ℃, the set voltage is 3.0-4.2V, and the current density is 0.5C.

Example 6

This example is substantially the same as example 5 except that: the electrolyte includes: lithium salt, second organic solvent, monofluoroethyl ethyl carbonate prepared in example 2, and electrolyte additive, the contents of lithium salt, second organic solvent, monofluoroethyl ethyl carbonate, and electrolyte additive in the electrolyte are shown in table 3.

The performance test of the battery was performed while maintaining the same test conditions as in example 5. The batteries prepared in examples 5 and 6 were tested and the results are shown in table 4.

TABLE 3

TABLE 4

The invention has been described in an illustrative manner, and it is to be understood that any simple variations, modifications or other equivalent changes which can be made by one skilled in the art without departing from the spirit of the invention fall within the scope of the invention.

Claims

1. The preparation method of the fluoroethyl ethyl carbonate is characterized by comprising the following steps of:

2. the process according to claim 1, wherein the filter cake is washed with the first organic solvent, the first organic solvent is distilled off, and the filtrate is mixed with the filtrate and distilled under reduced pressure to obtain the monofluoroethyl ethyl carbonate.

3. The method according to claim 1, wherein the first organic solvent is dimethyl carbonate, diethyl carbonate, methyl t-butyl ether or ethyl methyl carbonate.

4. The method according to claim 1, wherein the temperature of 50 to 120 ℃ is preferably 65 to 90 ℃.

5. The method according to any one of claims 1 to 4, wherein the methyl cucurbituril [6] is 1 to 3 wt% of the monochloroethyl ethyl carbonate.

6. The preparation method according to claim 5, wherein the ratio of the monochloroethyl ethyl carbonate to the first organic solvent is (0.1-1) by mass: 1.

7. use of fluoroethyl ethyl carbonate according to claim 1 as an additive in an electrolyte.

8. Use according to claim 7, wherein the electrolyte comprises: lithium salt, a second organic solvent, fluoroethyl ethyl carbonate and an electrolyte additive, wherein the second organic solvent is one or a mixture of more of dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, ethylene carbonate, propylene carbonate and ethyl methyl carbonate, the electrolyte additive is one or a mixture of more of vinylene carbonate VC, fluoroethylene carbonate FEC, 1, 3-propane sultone PS, ethylene sulfate PCS, propylene sulfite, ethylene carbonate VEC, propylene sulfate, phenyl acetone, 1, 4-butane sultone, tris (trimethylsilane) phosphite ester, butylene sulfite and 1, 4-succinonitrile, the second organic solvent accounts for 60-96 wt% of the electrolyte, the electrolyte additive accounts for 0.2-5 wt% of the electrolyte, and the monofluoroethyl ethyl carbonate accounts for 0.2-5 wt% of the electrolyte.

9. The use according to claim 7, wherein the lithium salt is lithium hexafluorophosphate and/or lithium tetrafluoroborate, and the amount of lithium salt in the electrolyte is 3-30 wt%.

10. The use of claim 7, wherein the battery is a nickel-cobalt-manganese ternary system battery comprising: the electrolyte comprises a positive electrode, a negative electrode, a diaphragm and the electrolyte, wherein the positive electrode material of the positive electrode is LiNi_xCo_yMn_1-x-yO₂Wherein x is more than or equal to 0.1 and less than or equal to 0.9, y is more than or equal to 0.1 and less than or equal to 0.9,1-x-y is more than or equal to 0, and the negative electrode is a metallic lithium sheet or a graphite carbon material.