Phosphate gemini quaternary ammonium salt ionic liquid flame retardant and preparation and application thereof

Abstract

The invention discloses a phosphate gemini quaternary ammonium salt ionic liquid flame retardant as well as 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 as shown in a formula I, a formula II and a formula III: # imgabs0. The phosphate gemini quaternary ammonium salt ionic liquid flame retardant is synthesized by two steps, and a quaternary ammonium salt structure is introduced to phosphate, so that the suffocation effect of the phosphate in a gas phase is compensated; the organic phosphorus-nitrogen free radicals can fully capture the free radicals during combustion, meanwhile, the phosphorus component effectively forms carbon by taking the epoxy resin as a carbon source, and the oxidation stability of Br <-> further improves the safety guarantee of the epoxy resin.

Description

Technical Field

[0001] The invention relates to the field of chemical synthesis, and in particular to a phosphate gemini quaternary ammonium salt ionic liquid flame retardant and a preparation method and application thereof. Background Art

[0002] With the depletion of fossil energy and the improvement of people's environmental awareness, it is urgent to find suitable substitutes for petrochemical energy. Lithium-ion batteries have quickly become the representative of the new generation of energy due to their high voltage and high energy density. At present, different types of high-performance lithium-ion batteries have emerged to meet the different needs of many industries such as new energy vehicles, large-scale energy storage power stations and portable electronic devices. However, the high energy density and low cost required for commercialization inevitably lead to certain safety issues. 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, the electrolyte has become a key obstacle to its further development due to its flammability.

[0003] So far, alkyl carbonates are often used as solvents in commercial lithium-ion battery electrolytes. This liquid electrolyte based on non-aqueous carbonates has great development potential in the field of highly reversible batteries due to its high fluidity and high dielectric constant in liquid electrolyte materials. However, its too low flash point is a risk that cannot be ignored for large lithium batteries that are often under high load. Its flammable and explosive properties and poor thermal stability make it very prone to accidents under abuse conditions such as high temperature, extrusion, and overcharging. The positive electrode material in the charged state has strong oxidizing properties, poor stability, and is easy to 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 causes a strong redox reaction when it comes into contact with oxygen, which also generates 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 greater than the thermal runaway rate. The accumulation of heat causes thermal runaway, which will inevitably lead to battery combustion and even explosion.

[0004] Phosphorus-containing flame retardants have been considered as one of the most promising flame retardants in recent years. Their excellent flame retardant properties in the condensed phase and gas phase have been widely praised by scholars at home and abroad. Since lithium battery electrolytes are mostly flammable organic solvents such as alkyl carbonates, choosing phosphate esters as flame retardants not only gives them good flame retardant properties, but also the good compatibility of esters in organic solvents ensures that the flame retardant has little effect on battery performance. Summary of the invention

[0005] The purpose of the present invention is to overcome the existing potential safety hazard of lithium ion electrolyte and provide a phosphate gemini quaternary ammonium salt ionic liquid flame retardant and its preparation and application.

[0006] In order to achieve the above object, the present invention adopts the following technical solution: In a first aspect, the present invention provides a method for preparing a phosphate gemini quaternary ammonium salt ionic liquid flame retardant, comprising the following steps: (1) Synthesis of quaternary ammonium salt intermediate: alkane bromide is dissolved in ethanol, and N,N-dimethylolamine compound is slowly added thereto through a constant pressure dropping funnel. The mixture is reacted at reflux temperature for 48 hours to obtain a light yellow liquid. After removing the ethanol by rotary evaporation, petroleum ether is added for recrystallization and drying to obtain a white solid, which is the quaternary ammonium salt intermediate. (2) Synthesis of flame retardant: Place the quaternary ammonium salt intermediate in a three-necked flask, add acetonitrile to dissolve it, and then add anhydrous sodium sulfate; dissolve phenylphosphonyl dichloride in another portion of acetonitrile and slowly drip it into the mixed solution through a constant pressure dropping funnel. React at 40°C under a nitrogen atmosphere for 2 hours to obtain a light yellow liquid; add petroleum ether and ethyl acetate to change the polarity of the solution, cool it down to precipitate white crystals and filter them to obtain a yellow liquid product. The solvent is spin-dried to obtain a dark red liquid product, which is the phosphate gemini quaternary ammonium salt ionic liquid flame retardant.

[0007] In a preferred embodiment of the present invention, the molar ratio of the brominated alkane to the N,N-dimethylalcoholamine compound is 1:1.1, and the ratio of the brominated alkane to ethanol is 9 mL:10 mL.

[0008] In a preferred embodiment of the present invention, the molar ratio of phenylphosphonyl dichloride to the quaternary ammonium salt intermediate is 1:2.1.

[0009] In a preferred embodiment of the present invention, the ratio of phenylphosphonic dichloride to acetonitrile is 1.5 mL:20 mL.

[0010] In a preferred embodiment of the present invention, the ratio of the quaternary ammonium salt intermediate to acetonitrile and anhydrous sodium sulfate is 9g:20mL:2g.

[0011] In a preferred embodiment of the present invention, the volume ratio of petroleum ether to ethyl acetate is 5:2.

[0012] In a preferred embodiment of the present invention, the brominated alkane is one of bromobutyl and dodecyl bromide; the N,N-dimethylalcoholamine compound is one of N,N-dimethylmethanolamine and N,N-dimethylethanolamine.

[0013] In a second aspect, the present invention provides a phosphate gemini quaternary ammonium salt ionic liquid flame retardant prepared by the above-mentioned preparation method. When the bromoalkane is bromobutyl and the N,N-dimethylalcoholamine compound is N,N-dimethylmethanolamine, its chemical structural formula is as shown in Formula I; when the bromoalkane is bromobutyl and the N,N-dimethylalcoholamine compound is N,N-dimethylethanolamine, its chemical structural formula is as shown in Formula II; when the bromoalkane is dodecyl bromide and the N,N-dimethylalcoholamine compound is N,N-dimethylethanolamine, its chemical structural formula is as shown in Formula III:

[0014] In a third aspect, the present invention provides the use of the phosphate gemini quaternary ammonium salt ionic liquid flame retardant prepared by the above-mentioned preparation method in the preparation of a flame-retardant lithium-ion battery electrolyte.

[0015] In a fourth aspect, the present invention provides a flame retardant lithium ion battery electrolyte, comprising a phosphate gemini quaternary ammonium salt ionic liquid flame retardant prepared by the above-mentioned preparation method; the amount of the phosphate gemini quaternary ammonium salt ionic liquid flame retardant added to the flame retardant lithium battery electrolyte is 5-15Vol%, and the original electrolyte used in the flame retardant lithium battery electrolyte is 1M LiPF 6 , the solvent is EC:DEC=1:1. .

[0016] Compared with the prior art, the beneficial technical effects of the present invention are: (1) The phosphate gemini quaternary ammonium salt ionic liquid flame retardant provided by the present invention is synthesized in two steps using N,N-dimethylethanolamine, n-butyl bromide and phenylphosphonyl dichloride as raw materials. By introducing a quaternary ammonium salt structure into the phosphate ester, the suffocation effect of the phosphate ester in the gas phase is compensated. The flame retardant is mainly used in the flame retardant lithium ion battery electrolyte. When the lithium ion battery electrolyte burns, the organic phosphorus nitrogen free radicals can fully capture the free radicals. At the same time, the phosphorus component can effectively form carbon with an organic solvent as a carbon source and has the effect of diluting the gas. In addition, the addition of the benzene ring can also improve the battery safety performance to a certain extent.

[0017] (2) The phosphate gemini quaternary ammonium salt ionic liquid flame retardant of the present invention still maintains good ionic conductivity and electrical cycling performance at a higher addition amount.

[0018] (3) The raw materials used for the phosphate gemini quaternary ammonium salt ionic liquid flame retardant of the present invention are easily available, and the synthesis and preparation are simple. It has good application prospects in the flame retardancy of lithium ion battery electrolytes and the enhancement of electrochemical properties. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 The infrared spectrum of the phosphate gemini quaternary ammonium salt ionic liquid flame retardant of Example 1 of the present invention; Figure 2The hydrogen nuclear magnetic resonance spectrum of the phosphate gemini quaternary ammonium salt ionic liquid flame retardant of Example 1 of the present invention; Figure 3 The nuclear magnetic resonance phosphorus spectrum of the phosphate gemini quaternary ammonium salt ionic liquid flame retardant of Example 1 of the present invention; DETAILED DESCRIPTION

[0020] The technical solution of the present invention will be described clearly and completely in conjunction with the embodiments below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0021] Example 1 Synthesis of quaternary ammonium salt intermediate: 12 g of bromobutane was dissolved in 20 mL of ethanol, 7.12 g of N,N-dimethylmethanolamine was slowly added thereto through a constant pressure dropping funnel, and the mixture was reacted at reflux temperature for 48 h to obtain a light yellow liquid; after rotary evaporation to remove ethanol, petroleum ether was added for recrystallization and drying to obtain a white solid product, N-(hydroxymethyl)-N,N-dimethylbutane quaternary ammonium salt, which is a quaternary ammonium salt intermediate.

[0022] Synthesis of flame retardant: 9 g of quaternary ammonium salt intermediate is placed in a three-necked flask, 20 mL of acetonitrile is added to dissolve, and then 2 g of anhydrous sodium sulfate is added; 2 g of phenylphosphonyl dichloride is dissolved in another 20 mL of acetonitrile and slowly dripped into the mixed solution through a constant pressure dropping funnel; react at 40 ° C. under a nitrogen atmosphere for 2 h to obtain a light yellow liquid, petroleum ether and ethyl acetate are added in a ratio of 5:2 to change the polarity of the solution, the temperature is lowered to precipitate white crystals and filtered to obtain a yellow liquid product, and the solvent is spin-dried to obtain a dark red liquid product, which is the phosphate gemini quaternary ammonium salt ionic liquid flame retardant of this embodiment.

[0023] The chemical structural formula of the phosphate gemini quaternary ammonium salt ionic liquid flame retardant of this embodiment is shown in Formula I:

[0024] like Figure 1-3 As shown, they are the infrared spectrum, nuclear magnetic resonance hydrogen spectrum, and nuclear magnetic resonance phosphorus spectrum of the epoxy resin flame retardant of this embodiment, respectively, indicating that the method of this embodiment successfully prepared the epoxy resin flame retardant.

[0025] Example 2 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 thereto through a constant pressure dropping funnel, and the mixture was reacted at reflux temperature for 48 h to obtain a light yellow liquid; after rotary evaporation to remove ethanol, petroleum ether was added for recrystallization and drying to obtain a white solid product, N-(2-hydroxyethyl)-N,N-dimethylbutane quaternary ammonium salt, which is a quaternary ammonium salt intermediate.

[0026] Synthesis of flame retardant: 4.5 g of quaternary ammonium salt intermediate is placed in a three-necked flask, 10 mL of acetonitrile is added to dissolve, and then 1 g of anhydrous sodium sulfate is added; 1 g of phenylphosphonyl dichloride is dissolved in another 10 mL of acetonitrile and slowly dripped into the mixed solution through a constant pressure dropping funnel; react at 40 ° C. under a nitrogen atmosphere for 2 hours to obtain a light yellow liquid; petroleum ether and ethyl acetate are added in a ratio of 5:2 to change the polarity of the solution, the temperature is lowered to precipitate white crystals and filtered to obtain a yellow liquid product, and the solvent is spin-dried to obtain a dark red liquid product, which is the phosphate gemini quaternary ammonium salt ionic liquid flame retardant of this embodiment.

[0027] The chemical structural formula of the phosphate gemini quaternary ammonium salt ionic liquid flame retardant of this embodiment is shown in Formula II: Example 3 Synthesis of quaternary ammonium salt intermediate: 24g of dodecyl bromide was dissolved in 40mL of ethanol, and 14.48g of N,N-dimethylethanolamine was slowly added thereto through a constant pressure dropping funnel, and the mixture was reacted at reflux temperature for 48h to obtain a light yellow liquid; after rotary evaporation to remove ethanol, petroleum ether was added for recrystallization and drying to obtain a white solid product, N-(2-hydroxyethyl)-N,N-dimethyldodecyl quaternary ammonium salt, which is a quaternary ammonium salt intermediate.

[0028] Synthesis of flame retardant: 18 g of quaternary ammonium salt intermediate is placed in a three-necked flask, 40 mL of acetonitrile is added to dissolve, and then 4 g of anhydrous sodium sulfate is added; 4 g of phenylphosphonyl dichloride is dissolved in another 40 mL of acetonitrile and slowly dripped into the mixed solution through a constant pressure dropping funnel; react at 40 ° C. under a nitrogen atmosphere for 2 hours to obtain a light yellow liquid; petroleum ether and ethyl acetate are added in a ratio of 5:2 to change the polarity of the solution, the temperature is lowered to precipitate white crystals and filtered to obtain a yellow liquid product, and the solvent is spin-dried to obtain a dark red liquid product, which is the phosphate gemini quaternary ammonium salt ionic liquid flame retardant of this embodiment.

[0029] The chemical structural formula of the phosphate gemini quaternary ammonium salt ionic liquid flame retardant of this embodiment is shown in Formula III: Example 4 The mixed organic solvent of binary lithium-ion battery electrolyte was prepared in the ratio of EC:DEC = 1:1, and the original electrolyte was 1M LiPF 6 , add the phosphate gemini quaternary ammonium salt ionic liquid flame retardant of Example 1 to the mixed organic solvent in an amount of 5Vol%, stir evenly, and obtain the flame-retardant lithium-ion battery electrolyte of this embodiment.

[0030] Example 5 The mixed organic solvent of binary lithium-ion battery electrolyte was prepared in the ratio of EC:DEC = 1:1, and the original electrolyte was 1M LiPF 6 , add the phosphate gemini quaternary ammonium salt ionic liquid flame retardant of Example 1 to the mixed organic solvent in an amount of 10Vol%, stir evenly, and obtain the flame-retardant lithium ion battery electrolyte of this embodiment.

[0031] Example 6 The mixed organic solvent of binary lithium-ion battery electrolyte was prepared in the ratio of EC:DEC = 1:1, and the original electrolyte was 1M LiPF 6 , add the phosphate gemini quaternary ammonium salt ionic liquid flame retardant of Example 1 to the mixed organic solvent in an amount of 15Vol%, stir evenly, and obtain the flame-retardant lithium-ion battery electrolyte of this embodiment.

[0032] Comparative Example 1 The mixed organic solvent of binary lithium-ion battery electrolyte was prepared in the ratio of EC:DEC = 1:1, and the original electrolyte was 1M LiPF 6 , stir evenly to obtain the lithium ion battery electrolyte of this comparative example.

[0033] Test Example 1 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, and the burning time was recorded using a stopwatch. This was repeated 10 times, and the average value was taken as the SET time. The SET value was measured to be 180 s / g. −1 .

[0034] Test Example 2 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, and the burning time was recorded using a stopwatch. This was repeated 10 times, and the average value was taken as the SET time. The SET value was measured to be 140s / g −1 , the flame retardant effect is improved by 22.2% compared with the original electrolyte.

[0035] Test Example 3 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, and the burning time was recorded using a stopwatch. This was repeated 10 times, and the average value was taken as the SET time. The SET value was measured to be 95s / g −1 , the flame retardant effect is improved by 41.6% compared with the original electrolyte.

[0036] Test Example 4 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, and the burning time was recorded using a stopwatch. This was repeated 10 times, and the average value was taken as the SET time. The SET value was measured to be 75s / g −1 , the flame retardant effect is improved by 58.3% compared with the original electrolyte.

[0037] Test Example 5 The limiting oxygen index of the lithium ion battery electrolyte of Comparative Example 1 was measured, and the LOI value was measured to be 15.9.

[0038] Test Example 6 The flame retardant lithium ion battery electrolyte of Example 4 was subjected to limiting oxygen index measurement, and the measured LOI value was found to be 19.5.

[0039] Test Example 7 The flame retardant lithium ion battery electrolyte of Example 5 was subjected to limiting oxygen index measurement, and the measured LOI value was found to be 25.9, and the UL-94 could reach V-1 level, showing good flame retardant properties.

[0040] Test Case 8 The flame retardant lithium ion battery electrolyte of Example 6 was subjected to limiting oxygen index measurement, and the measured LOI value was found to be 29.5, and the UL-94 could reach V-0 level, which showed good flame retardancy.

[0041] Test Example 9 The phosphate gemini quaternary ammonium salt ionic liquid flame retardant of Example 2 was used in the manner of Example 6 to prepare a flame-retardant lithium-ion battery electrolyte.

[0042] The SET value was measured according to the method of Test Example 4, and the measured SET value was 83s / g −1 The flame retardant effect is 47.1% higher than that of the original electrolyte. At the same time, the limiting oxygen index was measured, and the LOI value was 27.8, and the UL-94 can reach the V-1 level, which has good flame retardant properties.

[0043] Test Example 10 The phosphate gemini quaternary ammonium salt ionic liquid flame retardant of Example 3 was used in the manner of Example 6 to prepare a flame-retardant lithium-ion battery electrolyte.

[0044] The SET value was measured according to the method of Test Example 4, and the measured SET value was 95s / g −1 The flame retardant effect is 41.6% higher than that of the original electrolyte. At the same time, the limiting oxygen index is measured, and the LOI value is 25, and the UL-94 can reach the V-1 level, which has good flame retardant properties.

[0045] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the technical solution and conceptual invention of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for preparing a phosphate gemini quaternary ammonium salt ionic liquid flame retardant, characterized in that: The steps include: (1) Synthesis of quaternary ammonium salt intermediate: alkane bromide is dissolved in ethanol, and N,N-dimethylolamine compound is slowly added thereto through a constant pressure dropping funnel. The mixture is reacted at reflux temperature for 48 hours to obtain a light yellow liquid. After removing the ethanol by rotary evaporation, petroleum ether is added for recrystallization and drying to obtain a white solid, which is the quaternary ammonium salt intermediate. (2) Synthesis of flame retardant: Place the quaternary ammonium salt intermediate in a three-necked flask, add acetonitrile to dissolve it, and then add anhydrous sodium sulfate; dissolve phenylphosphonyl dichloride in another portion of acetonitrile and slowly drip it into the mixed solution through a constant pressure dropping funnel. React at 40°C under a nitrogen atmosphere for 2 hours to obtain a light yellow liquid; add petroleum ether and ethyl acetate to change the polarity of the solution, cool it down to precipitate white crystals and filter them to obtain a yellow liquid product. The solvent is spin-dried to obtain a dark red liquid product, which is the phosphate gemini quaternary ammonium salt ionic liquid flame retardant.

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

3. The preparation method according to claim 2, characterized in that: The molar ratio of the phenylphosphonic acid 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 the 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. The preparation method according to claim 6, characterized in that: The brominated alkane is one of brominated butylene and dodecyl bromide; the N,N-dimethyl alcoholamine compound is one of N,N-dimethylmethanolamine and N,N-dimethylethanolamine.

8. A phosphate gemini quaternary ammonium salt ionic liquid flame retardant prepared by the preparation method according to claim 6, wherein when the bromoalkane is bromobutyl and the N,N-dimethylalcoholamine compound is N,N-dimethylmethanolamine, its chemical structural formula is as shown in Formula I; when the bromoalkane is bromobutyl and the N,N-dimethylalcoholamine compound is N,N-dimethylethanolamine, its chemical structural formula is as shown in Formula II; when the bromoalkane is dodecyl bromide and the N,N-dimethylalcoholamine compound is N,N-dimethylethanolamine, its chemical structural formula is as shown in Formula III; 9. Use of the phosphate gemini quaternary ammonium salt ionic liquid flame retardant prepared by the preparation method according to any one of claims 1 to 7 in the preparation of flame-retardant lithium-ion battery electrolyte.

10. A flame retardant lithium ion battery electrolyte, characterized in that: It comprises a phosphate gemini quaternary ammonium salt ionic liquid flame retardant prepared by the preparation method described in any one of claims 1-7; the addition amount of the phosphate gemini quaternary ammonium salt ionic liquid flame retardant in the flame-retardant lithium battery electrolyte is 5-15Vol%, 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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