A phosphate ester gemini quaternary ammonium salt ionic liquid flame retardant and preparation and application thereof

Abstract

The application discloses a phosphate gemini quaternary ammonium salt ionic liquid flame retardant and a preparation and application thereof, and relates to the field of chemical synthesis.The chemical structural formula of the phosphate gemini quaternary ammonium salt ionic liquid flame retardant is shown as formula I, formula II and formula III.The phosphate gemini quaternary ammonium salt ionic liquid flame retardant is synthesized in two steps, the quaternary ammonium salt structure is introduced on the phosphate, the suffocation effect of the phosphate in the gas phase is made up, the suffocation effect of the phosphate in the gas phase is made up, the organic phosphorus nitrogen free radical can fully play the effect of capturing free radicals when combustion, meanwhile, the phosphorus component effectively forms carbon with the epoxy resin as a carbon source, and the oxidation stability of Br ‑ is further improved, so that the safety guarantee of the epoxy resin is further improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of chemical synthesis, in particular to a phosphate Gemini quaternary ammonium salt ionic liquid flame retardant and its preparation and application. BACKGROUND

[0002] With the depletion of fossil energy and the gradual improvement of people's environmental awareness, it is urgent to find a suitable substitute for fossil energy. Lithium-ion batteries have become the representative of the new generation of energy sources due to their high voltage and high energy density. At present, in order to meet the different needs of new energy vehicles, large-scale energy storage power stations and portable electronic devices, different types of high-performance lithium-ion batteries have emerged. However, the high energy density and low cost required for commercialization inevitably have certain safety problems. How to ensure the safety and reliability of lithium-ion batteries under such conditions has become a bottleneck restricting their practical application. As the core component of lithium-ion batteries, electrolyte has become a key obstacle to further development due to its flammability.

[0003] So far, alkyl carbonate is often used as a solvent in commercial lithium-ion battery electrolyte. This non-aqueous carbonate-based liquid electrolyte has great development potential in the field of highly reversible batteries due to its high flowability and high dielectric constant in liquid electrolyte materials. However, its very low flash point cannot be ignored for large lithium batteries that are often under high load. The characteristics of flammability, explosiveness and poor thermal stability make it prone to accidents under high temperature, extrusion, overcharge and other misuse conditions. The positive electrode material in the charged state has strong oxidizing properties and poor stability, which can release oxygen. When oxygen reacts with alkyl carbonate, a large amount of heat is released. At the same time, the strong reducing property of the negative electrode material will cause a strong oxidation-reduction reaction when it comes into contact with oxygen, which will also generate a large amount of heat. When a large amount of heat cannot be dissipated to the surrounding space in time, the heat release rate inside the battery is much higher than the heat dissipation rate, and the accumulation of heat leads to thermal runaway, which will inevitably lead to battery combustion and even explosion.

[0004] Phosphorus-containing flame retardants have been considered one of the most promising flame retardants in recent years, and their excellent flame retardant performance in condensed phase and gas phase has been widely praised by scholars at home and abroad. Since the electrolyte of lithium battery is mainly composed of flammable organic solvents such as alkyl carbonate, choosing phosphate as flame retardant not only gives it good flame retardant performance, but also ensures that the flame retardant has little effect on the performance of the battery due to the good compatibility of ester in organic solvents. SUMMARY

[0005] The purpose of the present application is to overcome the existing safety problems of lithium-ion electrolyte, and to provide a phosphate Gemini quaternary ammonium salt ionic liquid flame retardant and its preparation and application.

[0006] To achieve the above object, the present application adopts the following technical solutions:

[0007] In a first aspect, the present application provides a preparation method of phosphate gemini quaternary ammonium salt ionic liquid flame retardant, comprising the following steps:

[0008] (1) Synthesis of quaternary ammonium salt intermediate: dissolve bromoalkane in ethanol, slowly add N,N dimethyl alcohol amine compound through constant pressure dropping funnel, and react the mixture at reflux temperature for 48 h to obtain a light yellow liquid; after removing ethanol by rotary evaporation, add petroleum ether to recrystallize and dry to obtain white solid, which is the quaternary ammonium salt intermediate;

[0009] (2) Synthesis of flame retardant: place the quaternary ammonium salt intermediate in a three-necked flask, dissolve it in acetonitrile, and then add anhydrous sodium sulfate; dissolve phenyl phosphinic dichloride in another portion of acetonitrile, slowly drop it into the mixed solution through constant pressure dropping funnel, and react at 40°C under nitrogen atmosphere for 2 h to obtain a light yellow liquid; add petroleum ether and ethyl acetate to change the polarity of the solution, cool to precipitate white crystals, and filter to obtain a yellow liquid product, and dry the solvent to obtain a deep red liquid product, which is the phosphate gemini quaternary ammonium salt ionic liquid flame retardant.

[0010] In a preferred embodiment of the present application, the molar ratio of bromoalkane to N,N dimethyl alcohol amine compound is 1:1.1, and the ratio of bromoalkane to ethanol is 9 mL:10 mL.

[0011] In a preferred embodiment of the present application, the molar ratio of phenyl phosphinic dichloride to quaternary ammonium salt intermediate is 1:2.1.

[0012] In a preferred embodiment of the present application, the ratio of phenyl phosphinic dichloride to acetonitrile is 1.5 mL:20 mL.

[0013] In a preferred embodiment of the present application, the ratio of quaternary ammonium salt intermediate to acetonitrile and anhydrous sodium sulfate is 9 g:20 mL:2 g.

[0014] In a preferred embodiment of the present application, the volume ratio of petroleum ether to ethyl acetate is 5:2.

[0015] In a preferred embodiment of the present application, the bromoalkane is one of bromobutane and dodecyl bromide; and the N,N dimethyl alcohol amine compound is one of N,N dimethyl methanol amine and N,N dimethyl ethanol amine.

[0016] In a second aspect, the present application provides the phosphate Gemini quaternary ammonium salt ionic liquid flame retardant prepared by the preparation method, when the brominated alkane is n-butane and the N,N-dimethyl alcohol amine compound is N,N-dimethyl methanol amine, the chemical structural formula is shown as formula I; when the brominated alkane is n-butane and the N,N-dimethyl alcohol amine compound is N,N-dimethyl ethanol amine, the chemical structural formula is shown as formula II; when the brominated alkane is dodecyl bromide and the N,N-dimethyl alcohol amine compound is N,N-dimethyl ethanol amine, the chemical structural formula is shown as formula III:

[0017]

[0018] In a third aspect, the present application provides the application of the phosphate Gemini quaternary ammonium salt ionic liquid flame retardant prepared by the preparation method in the preparation of the flame-retardant lithium ion battery electrolyte.

[0019] In a fourth aspect, the present application provides a flame-retardant lithium ion battery electrolyte, which comprises the phosphate Gemini quaternary ammonium salt ionic liquid flame retardant prepared by the preparation method; the adding amount of the phosphate Gemini quaternary ammonium salt ionic liquid flame retardant in the flame-retardant lithium battery electrolyte is 5-15 Vol%, the original electrolyte used in the flame-retardant lithium battery electrolyte is 1M LiPF6, and the solvent is EC:DEC=1:1.

[0020] Compared with the prior art, the present application has the beneficial technical effects that:

[0021] (1) The phosphate Gemini quaternary ammonium salt ionic liquid flame retardant provided by the present application is synthesized by using N,N dimethyl ethanol amine, n-butane and phenyl phosphinic dichloride as raw materials in two steps, the quaternary ammonium salt structure is introduced on the phosphate, the suffocation effect of the phosphate in the gas phase is made up, the phosphate Gemini quaternary ammonium salt ionic liquid flame retardant is mainly applied to the flame-retardant lithium ion battery electrolyte, the organic phosphorus nitrogen free radical can fully play the effect of capturing free radicals when the lithium ion battery electrolyte burns, the phosphorus component can effectively form carbon with the carbon source of the organic solvent and the effect of diluting gas, and the addition of the benzene ring also has a certain improvement on the safety performance of the battery.

[0022] (2) The phosphate Gemini quaternary ammonium salt ionic liquid flame retardant provided by the present application still has good ionic conductivity and electrical cycle performance under a higher adding amount.

[0023] (3) The raw materials used in the phosphate Gemini quaternary ammonium salt ionic liquid flame retardant provided by the present application are easy to obtain, the synthesis and preparation are simple, and the phosphate Gemini quaternary ammonium salt ionic liquid flame retardant has a good application prospect in the enhancement of the lithium ion battery electrolyte flame retardation and electrochemical performance. BRIEF DESCRIPTION OF DRAWINGS

[0024] Fig. 1 The infrared spectrum of the phosphate Gemini quaternary ammonium salt ionic liquid flame retardant of the present application example 1 is shown in the figure;

[0025] Fig. 2 The nuclear magnetic resonance hydrogen spectrum of the phosphate ester gemini quaternary ammonium salt ionic liquid flame retardant of Example 1 of the present invention;

[0026] Fig. 3 The nuclear magnetic resonance phosphorus spectrum of the phosphate ester gemini quaternary ammonium salt ionic liquid flame retardant of Example 1 of the present invention; Detailed Implementation

[0027] The technical solutions of this invention will be clearly and completely described below with reference to the embodiments. Obviously, the described embodiments are only some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0028] Example 1

[0029] Synthesis of quaternary ammonium salt intermediate: 12 g of bromobutane was dissolved in 20 mL of ethanol, and 7.12 g of N,N-dimethylethanolamine was slowly added to it through a constant pressure dropping funnel. The mixture was reacted at reflux temperature for 48 h to obtain a pale yellow liquid. After removing the ethanol by rotary evaporation, petroleum ether was added for recrystallization and drying to obtain a white solid product, N-(hydroxymethyl)-N,N-dimethylbutane quaternary ammonium salt, which is the quaternary ammonium salt intermediate.

[0030] Synthesis of flame retardant: 9g of quaternary ammonium salt intermediate was placed in a three-necked flask and dissolved in 20mL of acetonitrile, followed by the addition of 2g of anhydrous sodium sulfate; 2g of phenylphosphonic dichloride was dissolved in another 20mL of acetonitrile and slowly added dropwise to the mixed solution through a constant pressure dropping funnel; the reaction was carried out at 40℃ under a nitrogen atmosphere for 2h to obtain a pale yellow liquid; petroleum ether and ethyl acetate were added in a 5:2 ratio to change the polarity of the solution; the solution was cooled to precipitate white crystals, which were then filtered to obtain a yellow liquid product; the solvent was evaporated to obtain a dark red liquid product, which is the phosphate ester gemini quaternary ammonium salt ionic liquid flame retardant of this embodiment.

[0031] The chemical structural formula of the phosphate ester gemini quaternary ammonium salt ionic liquid flame retardant in this embodiment is shown in Formula I:

[0032]

[0033] like Figs. 1-3 The images shown are the infrared spectrum, proton NMR spectrum, and phosphorus NMR spectrum of the epoxy resin flame retardant in this embodiment, indicating that the method of this embodiment successfully prepared the epoxy resin flame retardant.

[0034] Example 2

[0035] Synthesis of quaternary ammonium salt intermediate: 6 g of bromobutane was dissolved in 10 mL of ethanol, 3.56 g of N,N dimethylethanolamine was slowly added into the mixture through a constant pressure dropping funnel, the mixture was reacted at reflux temperature for 48 h to obtain a light yellow liquid; after removing ethanol by rotary evaporation, petroleum ether was added for recrystallization and drying to obtain white solid product N-(2-hydroxyethyl)-N,N-dimethylbutane quaternary ammonium salt, which was the quaternary ammonium salt intermediate.

[0036] Synthesis of flame retardant: 4.5 g of quaternary ammonium salt intermediate was placed in a three-necked flask, 10 mL of acetonitrile was added for dissolution, followed by addition of 1 g of anhydrous sodium sulfate; 1 g of phenyl phosphinic dichloride was dissolved in another 10 mL of acetonitrile, which was slowly dropped into the mixed solution through a constant pressure dropping funnel; the reaction was carried out at 40°C under nitrogen atmosphere for 2 h to obtain a light yellow liquid; petroleum ether and ethyl acetate were added in a ratio of 5:2 to change the polarity of the solution, white crystals were precipitated by cooling, and were filtered to obtain a yellow liquid product, and the solvent was dried to obtain a dark red liquid product, which was the phosphate Gemini quaternary ammonium salt ionic liquid flame retardant of the present example.

[0037] The chemical structural formula of the phosphate Gemini quaternary ammonium salt ionic liquid flame retardant of the present example is shown in Formula II:

[0038] Example 3

[0039] Synthesis of quaternary ammonium salt intermediate: 6 g of bromobutane was dissolved in 10 mL of ethanol, 3.56 g of N,N dimethylethanolamine was slowly added into the mixture through a constant pressure dropping funnel, the mixture was reacted at reflux temperature for 48 h to obtain a light yellow liquid; after removing ethanol by rotary evaporation, petroleum ether was added for recrystallization and drying to obtain white solid product N-(2-hydroxyethyl)-N,N-dimethylbutane quaternary ammonium salt, which was the quaternary ammonium salt intermediate.

[0040] Synthesis of flame retardant: 4.5 g of quaternary ammonium salt intermediate was placed in a three-necked flask, 10 mL of acetonitrile was added for dissolution, followed by addition of 1 g of anhydrous sodium sulfate; 1 g of phenyl phosphinic dichloride was dissolved in another 10 mL of acetonitrile, which was slowly dropped into the mixed solution through a constant pressure dropping funnel; the reaction was carried out at 40°C under nitrogen atmosphere for 2 h to obtain a light yellow liquid; petroleum ether and ethyl acetate were added in a ratio of 5:2 to change the polarity of the solution, white crystals were precipitated by cooling, and were filtered to obtain a yellow liquid product, and the solvent was dried to obtain a dark red liquid product, which was the phosphate Gemini quaternary ammonium salt ionic liquid flame retardant of the present example.

[0041] The chemical structural formula of the phosphate Gemini quaternary ammonium salt ionic liquid flame retardant of the present example is shown in Formula II:

[0042] Example 4

[0043] The binary lithium ion battery electrolyte mixed organic solvent was prepared according to the proportion of EC: DEC = 1:1, the original electrolyte was 1M LiPF6, the phosphonate Gemini quaternary ammonium salt ionic liquid flame retardant of Example 1 was added to the mixed organic solvent, the addition amount was 5Vol%, and the mixture was stirred uniformly to obtain the flame-retardant lithium ion battery electrolyte of the example.

[0044] Example 5

[0045] The binary lithium ion battery electrolyte mixed organic solvent was prepared according to the proportion of EC: DEC = 1:1, the original electrolyte was 1M LiPF6, the phosphonate Gemini quaternary ammonium salt ionic liquid flame retardant of Example 1 was added to the mixed organic solvent, the addition amount was 10Vol%, and the mixture was stirred uniformly to obtain the flame-retardant lithium ion battery electrolyte of the example.

[0046] Example 6

[0047] The binary lithium ion battery electrolyte mixed organic solvent was prepared according to the proportion of EC: DEC = 1:1, the original electrolyte was 1M LiPF6, the phosphonate Gemini quaternary ammonium salt ionic liquid flame retardant of Example 1 was added to the mixed organic solvent, the addition amount was 15Vol%, and the mixture was stirred uniformly to obtain the flame-retardant lithium ion battery electrolyte of the example.

[0048] Comparative Example 1

[0049] The binary lithium ion battery electrolyte mixed organic solvent was prepared according to the proportion of EC: DEC = 1:1, the original electrolyte was 1M LiPF6, and the mixture was stirred uniformly to obtain the lithium ion battery electrolyte of the comparative example.

[0050] Test Example 1

[0051] The glass fiber ball was immersed in the lithium ion battery electrolyte of Comparative Example 1 for a certain time interval, and then the glass fiber ball was ignited, the burning time was recorded using a stopwatch, and the average value was taken as the SET time. The measured SET value was 180s / g −1 .

[0052] Test Example 2

[0053] The glass fiber ball was immersed in the flame-retardant lithium ion battery electrolyte of Example 4 for a certain time interval, and then the glass fiber ball was ignited, the burning time was recorded using a stopwatch, and the average value was taken as the SET time. The measured SET value was 140s / g −1 , the flame-retardant effect was improved by 22.2% compared with the original electrolyte.

[0054] Test Example 3

[0055] The glass fiber ball was immersed in the flame-retardant lithium ion battery electrolyte of Example 5 for a certain time interval, and then the glass fiber ball was ignited, the burning time was recorded using a stopwatch, repeated 10 times, and the average value was the SET time. The measured SET value was 95 s / g −1 The flame-retardant effect was improved by 41.6% compared with the original electrolyte.

[0056] Test Example 4

[0057] The glass fiber ball was immersed in the flame-retardant lithium ion battery electrolyte of Example 6 for a certain time interval, and then the glass fiber ball was ignited, the burning time was recorded using a stopwatch, repeated 10 times, and the average value was the SET time. The measured SET value was 75 s / g −1 The flame-retardant effect was improved by 58.3% compared with the original electrolyte.

[0058] Test Example 5

[0059] The lithium ion battery electrolyte of Comparative Example 1 was subjected to limiting oxygen index determination, and the measured LOI value was 15.9.

[0060] Test Example 6

[0061] The flame-retardant lithium ion battery electrolyte of Example 4 was subjected to limiting oxygen index determination, and the measured LOI value was 19.5.

[0062] Test Example 7

[0063] The flame-retardant lithium ion battery electrolyte of Example 5 was subjected to limiting oxygen index determination, and the measured LOI value was 25.9, and the UL-94 could reach V-1 level, having good flame-retardant performance.

[0064] Test Example 8

[0065] The flame-retardant lithium ion battery electrolyte of Example 6 was subjected to limiting oxygen index determination, and the measured LOI value was 29.5, and the UL-94 could reach V-0 level, having good flame-retardant performance.

[0066] Test Example 9

[0067] The phosphonate gemini quaternary ammonium salt ionic liquid flame retardant of Example 2 was used to prepare a flame-retardant lithium ion battery electrolyte according to the method of Example 6.

[0068] The SET value was measured according to the method of Test Example 4, and the measured SET value was 83 s / g −1 The flame-retardant effect was improved by 47.1% compared with the original electrolyte. At the same time, the limiting oxygen index determination was carried out, and the measured LOI value was 27.8, and the UL-94 could reach V-1 level, having good flame-retardant performance.

[0069] Test Example 10

[0070] The phosphate ester gemini quaternary ammonium salt ionic liquid flame retardant of Example 3 was used to prepare a flame-retardant lithium ion battery electrolyte in the manner of Example 6.

[0071] The SET value was measured in the manner of Test Example 4 and was found to be 95 s / g −1 The flame-retardant effect was improved by 41.6% compared to the original electrolyte. At the same time, the limiting oxygen index was determined and the LOI value was found to be 25, and the UL-94 can reach V-1 level, having good flame-retardant performance.

[0072] The above only describes the preferred embodiments of the present application and is not intended to limit the present application. Any modification, equivalent replacement and improvement within the technical solutions and concepts of the present application shall be included in the protection scope of the present application.

Claims

1. A method for preparing a phosphate ester gemini quaternary ammonium salt ionic liquid flame retardant, characterized in that, Includes the following steps: (1) Synthesis of quaternary ammonium salt intermediate: Bromoalkanes were dissolved in ethanol, and N,N-dimethylolamine compounds were slowly added to them through a constant pressure dropping funnel. The mixture was reacted at reflux temperature for 48 h to obtain a pale yellow liquid. After removing the ethanol by rotary evaporation, petroleum ether was added for recrystallization and drying to obtain a white solid, which is the quaternary ammonium salt intermediate. (2) Synthesis of flame retardant: The quaternary ammonium salt intermediate was placed in a three-necked flask and dissolved in acetonitrile, followed by the addition of anhydrous sodium sulfate; phenylphosphonic dichloride was dissolved in another part of acetonitrile and slowly added dropwise to the mixed solution through a constant pressure dropping funnel. The reaction was carried out at 40°C under a nitrogen atmosphere for 2 hours to obtain a pale yellow liquid; petroleum ether and ethyl acetate were added to change the polarity of the solution, and white crystals were precipitated by cooling and filtration to obtain a yellow liquid product. The solvent was evaporated to obtain a dark red liquid product, which is the phosphate ester gemini quaternary ammonium salt ionic liquid flame retardant; The bromoalkane is one of bromobutane and dodecyl bromide; the N,N-dimethylolamine is one of N,N-dimethylmethanolamine and N,N-dimethylethanolamine.

2. The preparation method according to claim 1, characterized in that: The molar ratio of the bromoalkane to the N,N-dimethylolamine compound is 1:1.1, and the ratio of the bromoalkane to ethanol is 9 mL:10 mL.

3. The preparation method according to claim 2, characterized in that: The molar ratio of phenylphosphonic dichloride to the quaternary ammonium salt intermediate is 1:2.

1.

4. The preparation method according to claim 3, characterized in that: The ratio of phenylphosphonic dichloride to acetonitrile is 1.5 mL: 20 mL.

5. The preparation method according to claim 4, characterized in that: The ratio of the quaternary ammonium salt intermediate to acetonitrile and anhydrous sodium sulfate is 9g:20mL:2g.

6. The preparation method according to claim 5, characterized in that: The volume ratio of petroleum ether to ethyl acetate is 5:

2.

7. A phosphate ester gemini quaternary ammonium salt ionic liquid flame retardant prepared by the preparation method according to claim 6, wherein when the bromoalkane is butane bromo and the N,N-dimethylolamine compound is N,N-dimethylethanolamine, its chemical structure is as shown in Formula I; when the bromoalkane is butane bromo and the N,N-dimethylolamine compound is N,N-dimethylethanolamine, its chemical structure is as shown in Formula II; and when the bromoalkane is dodecyl bromide and the N,N-dimethylolamine compound is N,N-dimethylethanolamine, its chemical structure is as shown in Formula III. 。 8. The application of the phosphate ester gemini quaternary ammonium salt ionic liquid flame retardant prepared by the preparation method according to any one of claims 1-6 in the preparation of flame-retardant lithium-ion battery electrolyte.

9. A flame-retardant lithium-ion battery electrolyte, characterized in that: The flame retardant includes a phosphate ester gemini quaternary ammonium salt ionic liquid prepared by the preparation method according to any one of claims 1-6; the amount of the phosphate ester gemini quaternary ammonium salt ionic liquid flame retardant added to the flame retardant lithium battery electrolyte is 5-15 Vol%, and the original electrolyte used in the flame retardant lithium battery electrolyte is 1M LiPF6, and the solvent is EC:DEC=1:1.

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