Guanidine salt ionic liquid and preparation method and application thereof

文档序号：1703087 发布日期：2019-12-13 浏览：39次中文

阅读说明：本技术 一种胍盐离子液体及其制备方法和应用 (Guanidine salt ionic liquid and preparation method and application thereof ) 是由张文林刘雪娇王雨昕和佳明马青查李春利于 2019-09-10 设计创作，主要内容包括：本发明为一种胍盐离子液体及其制备方法和应用。该胍盐类离子液体具体结构如下：其中,n1为0,1或2；n2为1或2；Y-为BF4-,PF6-,TFSI-,FSI-或N(CN)2-。制备方法中,通过2-氨基丁烷的反应,引入了支链烷基；并改变了传统方法中的烷基化反应,通过卤素取代反应引入了醚基官能团。本发明将该胍盐离子液体作为添加剂,以少量的离子液体、锂盐和有机溶剂作为锂电池的电解液,具有粘度较低,电化学性能良好的优点。<Image he="362" wi="515" file="DDA0002196804680000011.GIF" imgContent="drawing" imgFormat="GIF" orientation="portrait" inline="no"></Image>(the invention relates to a guanidine salt ionic liquid and a preparation method and application thereof. The specific structure of the guanidinium ionic liquid is as follows: wherein n is 1 Is 0,1 or 2; n is 2 Is 1 or 2; y is ‑ is BF 4 ‑ ，PF 6 ‑ ，TFSI ‑ ，FSI ‑ Or N (CN) 2 ‑ . In the preparation method, branched alkyl is introduced through the reaction of 2-aminobutane; and changes the alkylation reaction in the traditional methodAn ether functional group is introduced by a halogen substitution reaction. The guanidine salt ionic liquid is used as an additive, and a small amount of ionic liquid, lithium salt and organic solvent are used as electrolyte of the lithium battery, so that the guanidine salt ionic liquid has the advantages of low viscosity and good electrochemical performance.)

1. A guanidine salt ionic liquid, which has the following structure:

wherein n is₁Is 0,1 or 2; n is₂is 1 or 2; y is^-Is BF₄ ^-，PF₆ ^-，TFSI^-，FSI^-Or N (CN)₂ ^-。

2. the process for preparing the guanidinium ionic liquid of claim 1, comprising the steps of:

(1) Dissolving tetramethylurea in a solvent, dripping oxalyl chloride under the conditions of protective gas atmosphere and stirring, and reacting at 60-80 ℃ for 24-36 hours to obtain a product N, N, N, N-tetramethylchloromethylammonium chloride, wherein the structural formula is as follows;

Wherein the raw material molar ratio is tetramethylurea: oxalyl chloride is 1: 1-1: 1.3; the solvent is toluene, and 100-170 ml of toluene is added to each mol of tetramethylurea;

(2) adding N, N, N, N-tetramethylchloromethylammonium chloride into a solvent dichloromethane at 0 ℃, then dripping 2-aminoalkane into the solvent dichloromethane, and heating and carrying out reflux reaction for 18-25 hours under stirring; after cooling, dripping sodium hydroxide solution under the ice bath condition to obtain the following alkyl guanidine salt ionic liquid with branched chains;

Wherein, the molar ratio is N, N, N, N-tetramethyl chloromethyl ammonium chloride: 2-aminoalkane: dichloromethane: sodium hydroxide is 1:4 to 4.1: 6-10: 20 to 22; the 2-amino alkane is specifically 2-aminopropane, 2-aminobutane or 2-aminopentane; the mass percentage concentration of the sodium hydroxide solution is 30-40%;

wherein n is₁is 0,1 or 2;

(3) Under the protective atmosphere, dropwise adding halogenated ether into the branched alkyl guanidine salt ionic liquid, and reacting at 40-50 ℃ for 24-36 hours to obtain 1,1,3, 3-tetramethyl-2, 2-alkyl alkoxy guanidine salt halide with the following structural formula:

wherein n is₁Is 0,1 or 2; n is₂is 1 or 2; x is halogen; the molar ratio of the branched alkyl guanidine salt ionic liquid to the halogenated ether is 1: 1.05-1: 1.2;

The halogenated ether is specifically 2-bromomethyl methyl ether or 2-bromomethyl ethyl ether; the solvent in the branched alkyl guanidine salt ionic liquid is acetonitrile;

(4) according to the method, the 1,1,3, 3-tetramethyl-2, 2-alkyl alkoxy guanidine salt halide synthesized by the method is mixed with inorganic salt M⁺Y^-Dissolving the raw materials in deionized water in sequence, mixing the raw materials and reacting the mixture at room temperature for 24 to 3and 6 hours, obtaining the guanidine salt ionic liquid with the following structural formula:

Wherein M is⁺Is Li; y is^-Is BF₄ ^-，PF₆ ^-，TFSI^-，FSI^-Or N (CN)₂ ^-(ii) a The molar ratio of the synthesized 1,1,3, 3-tetramethyl-2, 2-alkyl alkoxy guanidine salt halide to the deionized water is 1: 1.7-1: 2.8; the molar ratio is 1,1,3, 3-tetramethyl-2, 2-alkyl alkoxy guanidine salt halide: inorganic salt M⁺Y^-＝1:1～1:1.2。

3. the method for preparing the guanidine salt ionic liquid of claim 2, wherein the step (2) further comprises the following steps: heating and refluxing the N, N, N, N-tetramethylchloromethylammonium chloride and 2-amino alkane for 18-25 hours, adding a sodium hydroxide solution, and then separating and purifying the alkyl guanidine salt ionic liquid with the branched chain of the product, wherein the separation and purification process comprises the following steps:

Extracting the mixture obtained after the reaction with dichloromethane for 2-4 times, and combining organic phases; drying with anhydrous magnesium sulfate, removing volatile dichloromethane from the dried solution through rotary evaporation, and distilling the residual liquid under reduced pressure to obtain the branched alkyl guanidine salt ionic liquid.

4. The method for preparing the guanidine salt ionic liquid of claim 2, wherein the step (4) further comprises the following steps: mixing the 1,1,3, 3-tetramethyl-2, 2-alkyl alkoxy guanidine salt halide and inorganic salt M⁺Y^-And after the deionized water reacts at room temperature, separating and purifying the ionic liquid, wherein the ionic liquid separation and purification process comprises the following steps:

Extracting the mixed solution obtained after the reaction for 2-4 times by using dichloromethane, washing the mixed solution for several times by using deionized water, checking the mixed solution by using a silver nitrate solution until the eluate does not contain halogen ions, performing rotary evaporation on the treated solution to remove volatile dichloromethane, and drying the treated solution for more than 24-36 hours under a vacuum condition to obtain the guanidinium ionic liquid: 1,1,3, 3-tetramethyl-2, 2-alkyl alkoxy guanidine bis (trifluoromethyl sulfonyl) imide salt ionic liquid.

5. The process for preparing the guanidinium ionic liquid of claim 2, wherein the molar ratio of tetramethylurea to oxalyl chloride is preferably 1: 1.1;

The molar ratio of the N, N, N, N-tetramethylchloromethylammonium chloride to the 2-aminoalkane is preferably 1: 4;

The molar ratio of branched alkylguanidine to halogenated ether is preferably 1: 1.05;

The 1,1,3, 3-tetramethyl-2, 2-alkyl alkoxy guanidine salt halide and inorganic salt M⁺Y^-Is preferably 1:1.

6. The method of claim 2, wherein the protective atmosphere is nitrogen or argon.

7. Use of a guanidinium ionic liquid according to claim 1 as electrolyte for lithium ion batteries.

8. Use of a guanidinium ionic liquid according to claim 7, characterized in that the electrolyte comprises: organic solvents, lithium salts and ionic liquids; wherein the mass percent of the lithium salt is 1-10%, the mass percent of the ionic liquid is 1-20%, and the mass percent of the organic solvent is 70-90%;

The guanidine salt ionic liquid has the following structure:

wherein n is₁Is 0,1 or 2; n is₂Is 1 or 2; y is^-Is BF₄ ^-，PF₆ ^-，TFSI^-，FSI^-Or N (CN)₂ ^-；

The organic solvent is a mixed solution of propylene carbonate and dimethyl carbonate; wherein the volume ratio of the propylene carbonate to the dimethyl carbonate is 1: 2-1: 4;

The lithium salt is LiTFSI or LiPF₆、LiBF₄Or LiBOB.

9. The use of the guanidine salt ionic liquid of claim 8, wherein the electrolyte is prepared by a method comprising the steps of:

Mixing propylene carbonate and dimethyl carbonate according to the proportion to obtain an organic solvent; and mixing an organic solvent and the guanidine salt ionic liquid, adding a lithium salt after stirring, and continuously stirring until the lithium salt is completely dissolved to obtain the ionic liquid electrolyte.

Technical Field

The invention relates to the technical field of ionic liquid. Mainly used for researching preparation method of novel guanidine ionic liquid and application of novel guanidine ionic liquid in lithium ion battery

Background

The lithium secondary battery has the outstanding advantages of high working voltage, high specific energy, long cycle life, no memory effect, environmental friendliness and the like, has developed rapidly since 1992, and has become a hot spot of new energy research in the 21 st century. However, with the expansion of the application field of lithium secondary batteries, the requirements for the rate capacity and power density of the batteries are continuously increased, the safety problem of the lithium secondary batteries is gradually highlighted, and the lithium secondary batteries manufactured by Sony company have been recalled many times due to accidents such as combustion and explosion during use. The traditional electrolyte system composed of carbonic ester and inorganic salt cannot meet the requirements of the lithium secondary battery on high power density and high energy density due to the characteristics of easy volatilization and easy combustion, so that the research on the novel electrolyte system of the lithium secondary battery is not slow.

The ionic liquid is a liquid low-melting-point ionic compound, and is a salt substance which is composed of anions and cations and is in a liquid state at room temperature or near room temperature. The ionic liquid is generally composed of organic cations and inorganic or organic anions, wherein the cations mainly comprise imidazoles, quaternary ammonium salts, guanidines and the like, and the anions mainly comprise halogen anions, hexafluorophosphate anions and the like. It has excellent physicochemical properties: wider electrochemical window, good stability, higher conductivity and catalytic activity, and the like. Different combinations of anions and cations of the ionic liquid can be designed and synthesized into various ionic liquids. With the increasing research of ionic liquid, the ionic liquid is widely applied to various fields such as organic synthesis, catalysis, extraction separation, electrochemistry and the like. However, according to the needs of practical application, different functional groups are introduced into the cation instead of alkyl groups, and the design and synthesis of ionic liquids with specific functions are one of the main directions for research.

the research of ionic liquid in lithium ion batteries is the focus of research of people at present, and common ionic liquid electrolyte is mainly imidazole, but the electrochemical window is narrow, the capacity attenuation is fast, the stability to a lithium electrode is poor, and the problem of compatibility of imidazole cations in electrode materials must be effectively solved. And the high-viscosity ionic liquid serving as an electrolyte greatly restricts the conductivity of the lithium ion battery.

At present, the reports on guanidine salt ionic liquids are few, especially, the research on the properties and the application of the guanidine salt ionic liquids is very limited, the types of the guanidine salt ionic liquids are few, and the ionic liquids mainly comprise four-alkyl guanidine and six-alkyl guanidine, and it is known from the reports that alkyl guanidine mainly comprises linear alkyl substitution, and the guanidine salt ionic liquids are not found in the research on branched alkyl guanidine. In addition, in the field of batteries, the guanidine salt ionic liquid has high viscosity due to its own structure, which is the most fatal disadvantage as a battery electrolyte, thereby greatly hindering the application of the guanidine salt ionic liquid as a battery electrolyte. Therefore, a novel guanidine salt ionic liquid is developed and functionalized with a purpose, so that the guanidine salt ionic liquid has specific functions, and the novel guanidine salt ionic liquid is applied to the industry, so that the development of the guanidine salt ionic liquid is a new step.

Disclosure of Invention

The invention aims to provide a guanidine salt ionic liquid aiming at the defects in the prior art. The ionic liquid structurally has branched alkyl, and an ether group is introduced to a double-bond nitrogen position, so that the viscosity of the ionic liquid is reduced, and the ionic liquid is better applied to a lithium ion battery; in the preparation method, branched alkyl is introduced through the reaction of 2-aminobutane; and the alkylation reaction in the traditional method is changed, and an ether functional group is introduced through a halogen substitution reaction. The guanidine salt ionic liquid is used as an additive, and a small amount of ionic liquid, lithium salt and organic solvent are used as electrolyte of the lithium battery, so that the guanidine salt ionic liquid has the advantages of low viscosity and good electrochemical performance.

The technical scheme of the invention is that

a guanidine salt ionic liquid has the following specific structure:

Wherein n is₁Is 0,1 or 2; n is₂is 1 or 2; y is^-Is BF₄ ^-，PF₆ ^-，TFSI^-，FSI^-Or N (CN)₂ ^-。

The preparation method of the guanidine salt ionic liquid comprises the following steps:

(1) dissolving tetramethylurea in a solvent, dripping oxalyl chloride under the conditions of protective gas atmosphere and stirring, and reacting at 60-80 ℃ for 24-36 hours to obtain a product N, N, N, N-tetramethylchloromethylammonium chloride, wherein the structural formula is as follows;

Wherein the raw material molar ratio is tetramethylurea: oxalyl chloride is 1: 1-1: 1.3; the solvent is toluene, and 100-170 ml of toluene is added to each mol of tetramethylurea;

(2) Adding N, N, N, N-tetramethylchloromethylammonium chloride into a solvent dichloromethane at 0 ℃, then dripping 2-aminoalkane into the solvent dichloromethane, and heating and carrying out reflux reaction for 18-25 hours under stirring; after cooling, dripping sodium hydroxide solution under the ice bath condition to obtain the following alkyl guanidine salt ionic liquid with branched chains;

Wherein, the molar ratio is N, N, N, N-tetramethyl chloromethyl ammonium chloride: 2-aminoalkane: dichloromethane: sodium hydroxide is 1:4 to 1: 4.1: 6-10: 20 to 22; the 2-amino alkane is specifically 2-aminopropane, 2-aminobutane or 2-aminopentane; the mass percentage concentration of the sodium hydroxide solution is 30-40%;

Wherein n is₁Is 0,1 or 2;

(3) Under the protective atmosphere, halogenated ether is added into the branched alkyl guanidine salt ionic liquid dropwise to react at the temperature of 40-50 ℃ to obtain 24-E

After 36 hours, a 1,1,3, 3-tetramethyl-2, 2-alkylalkoxyguanidine salt halide having the formula:

wherein n is₁Is 0,1 or 2; n is₂Is 1 or 2; x is halogen; the molar ratio of the branched alkyl guanidine salt ionic liquid to the halogenated ether

＝1:1.05～1:1.2；

The halogenated ether is specifically 2-bromomethyl methyl ether or 2-bromomethyl ethyl ether; the solvent in the branched alkyl guanidine salt ionic liquid is acetonitrile;

(4) according to the method, the 1,1,3, 3-tetramethyl-2, 2-alkyl alkoxy guanidine salt halide synthesized by the method is mixed with inorganic salt M⁺Y^-dissolving in deionized water in sequence, mixing and reacting at room temperature for 24-36 hours to obtain the guanidine salt ionic liquid with the following structural formula:

The molar ratio of tetramethylurea to oxalyl chloride is preferably 1: 1.1.

The molar ratio of the N, N, N, N-tetramethylchloromethylammonium chloride to the 2-aminoalkane is preferably 1:4.

The molar ratio of the branched alkyl guanidine salt ionic liquid to the halogenated ether is preferably 1: 1.05.

The 1,1,3, 3-tetramethyl-2, 2-alkyl alkoxy guanidine salt halide and inorganic salt M⁺Y^-Is preferably 1:1.

The protective atmosphere is nitrogen or argon.

in the step (2), the method further comprises the following steps: heating and refluxing the N, N, N, N-tetramethylchloromethylammonium chloride and 2-amino alkane for 18-25 hours, adding a sodium hydroxide solution, and then separating and purifying the alkyl guanidine salt ionic liquid with the branched chain of the product, wherein the separation and purification process comprises the following steps:

The resulting mixture after the reaction was extracted 2 to 4 times with dichloromethane, and the organic phases were combined. Drying with anhydrous magnesium sulfate, removing volatile dichloromethane from the dried solution through rotary evaporation, and distilling the residual liquid under reduced pressure to obtain the branched alkyl guanidine salt ionic liquid.

In the step (4), the method further comprises the following steps: mixing the 1,1,3, 3-tetramethyl-2, 2-alkyl alkoxy guanidine salt halide and inorganic salt M⁺Y^-And after the deionized water reacts at room temperature, separating and purifying the ionic liquid, wherein the ionic liquid separation and purification process comprises the following steps:

The guanidine salt ionic liquid is applied as an electrolyte of a lithium ion battery.

The electrolyte includes: organic solvents, lithium salts and ionic liquids; the mass percent of the lithium salt is 1-10%, the mass percent of the ionic liquid is 1-20%, the mass percent of the organic solvent is 70-90%, and the structure of the guanidine salt ionic liquid is as follows:

Wherein n is₁Is 0,1 or 2; n is₂Is 1 or 2; y is^-is BF₄ ^-，PF₆ ^-，TFSI^-，FSI^-or N (CN)₂ ^-。

The organic solvent is a mixed solution of propylene carbonate and dimethyl carbonate; wherein the volume ratio of the propylene carbonate to the dimethyl carbonate is 1: 2-1: 4.

the lithium salt is LiTFSI or LiPF₆、LiBF₄Or LiBOB.

The molar ratio of tetramethylurea to oxalyl chloride is preferably 1: 1.1.

The molar ratio of the N, N, N, N-tetramethylchloromethylammonium chloride to the 2-aminoalkane is preferably 1:4.

the molar ratio of branched alkylguanidine to halogenated ether is preferably 1: 1.05.

The 1,1,3, 3-tetramethyl-2, 2-alkyl alkoxy guanidine salt halide and inorganic salt M⁺Y^-Is preferably 1:1.

The invention has the substantive characteristics that:

The cation of the guanidine salt ionic liquid is 1,1,3, 3-tetramethyl-2, 2-alkyl alkoxy guanidine cation, and compared with the traditional guanidine cation, after the guanidine is substituted by branched alkyl, the guanidine salt ionic liquid has more alkyl electron-donating groups, so that the viscosity of the ionic liquid is effectively reduced, the electrochemical stability is improved, and the electrochemical window of the ionic liquid is wider; due to the introduction of alkoxy, the guanidine salt ionic liquid has functionalized ether bonds, the dissolving capacity of the guanidine salt ionic liquid is improved, the viscosity of the guanidine salt ionic liquid can be effectively reduced, and the electrochemical performance of the battery is improved; furthermore, the introduction of alkoxy groups allows the ionic liquid to have a lower melting point. Through electrochemical performance detection, the guanidine salt ionic liquid has better electrochemical stability and conductivity than the traditional ionic liquid.

The preparation process of the guanidine salt ionic liquid comprises the steps of firstly preparing N, N, N, N-tetramethyl chloromethyl ammonium chloride by using tetramethylurea and oxalyl chloride, secondly reacting the N, N, N, N-tetramethyl chloromethyl ammonium chloride with 2-amino alkane and sodium hydroxide to prepare alkyl guanidine salt ionic liquid with branched chains, secondly reacting the alkyl guanidine salt ionic liquid with halogenated ether to prepare 1,1,3, 3-tetramethyl-2, 2-alkyl alkoxy guanidine salt halide, and finally carrying out ion exchange reaction on the 1,1,3, 3-tetramethyl-2, 2-alkyl alkoxy guanidine salt halide and inorganic salt containing target anions, and separating, purifying and drying the product obtained by the ion exchange reaction, namely the guanidine salt ionic liquid. The process method is universal, raw materials are easy to obtain, the reaction is easy to control, the product yield is high, the process method is suitable for industrial production, and the prepared guanidine salt ionic liquid has excellent electrochemical performance and is suitable for lithium ion battery electrolyte.

the invention has the beneficial effects that:

The preparation method of the guanidine salt ionic liquid is universal, raw materials are easy to obtain, the reaction is easy to control, and the method is suitable for industrial production. The concrete expression is as follows:

The synthesized guanidine salt ionic liquid has lower viscosity and higher conductivity, and the introduction of alkoxy groups enables the guanidine salt ionic liquid to have functionalized ether bonds, so that the dissolving capacity of the guanidine salt ionic liquid is improved; after the guanidine is substituted by the branched alkyl, the viscosity of the ionic liquid is effectively reduced, the electrochemical stability is improved, and the electrochemical window of the ionic liquid is wider. The electrolyte is applied to a lithium ion battery as an electrolyte, and LiFeO is adopted₂the/Li is used as the positive electrode and the negative electrode of the battery, the cycle effect is good, and the capacity retention rate is high.

Compared with the traditional lithium ion battery electrolyte, the guanidine salt ionic liquid electrolyte is introduced due to the introduction of the ionic liquidthe lithium ion battery has higher electrochemical stability, and the safety performance of the battery is improved; meanwhile, the formation of an SEI film of the graphite cathode is promoted, and the cycle performance of the battery is improved. The cation of the guanidine salt ionic liquid is 1,1,3, 3-tetramethyl-2, 2-alkyl alkoxy guanidine cation, and compared with the traditional guanidine cation, after the guanidine is substituted by branched alkyl, the guanidine salt ionic liquid has more alkyl electron-donating groups, can effectively reduce the viscosity of the ionic liquid, improves the electrochemical stability and enables the electrochemical window of the ionic liquid to be wider; due to the introduction of alkoxy, the guanidine salt ionic liquid has functionalized ether bonds, the dissolving capacity of the guanidine salt ionic liquid can be increased, and the electrochemical performance of the battery is improved; and, the introduction of alkoxy groups allows the ionic liquid to have a lower melting point. Through electrochemical performance detection, the guanidine salt ionic liquid has better electrochemical stability and conductivity than the traditional ionic liquid. The electrolyte is applied to LiFeO as electrolyte₂in the Li lithium ion battery, as can be seen from FIG. 2, the maximum specific discharge capacity at 0.2C is 122mAh g^-1The specific discharge capacity after 50 cycles is 108mAh g^-1The capacity retention rate is nearly 90 percent, and the capacity retention rate is higher.

drawings

FIG. 1 is a nuclear magnetic hydrogen spectrum of the ionic liquid obtained in example 1;

FIG. 2 is a charge-discharge cycle test chart of the lithium ion battery obtained in example 1;

Detailed Description

The preparation of the guanidinium ionic liquid and the application thereof in the electrolyte of the lithium ion battery are further described with reference to the accompanying drawings and specific examples.

one embodiment of a guanidinium ionic liquid has the following structural formula:

Wherein n is₁Is 0,1 or 2; n is₂Is 1 or 2; y is^-Is BF₄ ^-，PF₆ ^-，TFSI^-，FSI^-Or N (CN)₂ ^-。

The cation of the guanidine salt ionic liquid is 1,1,3, 3-tetramethyl-2, 2-alkyl alkoxy guanidine cation, and compared with the traditional guanidine cation, the guanidine cation is substituted by branched alkyl, so that the viscosity of the ionic liquid is effectively reduced, the electrochemical stability is improved, and the electrochemical window of the ionic liquid is wider; due to the introduction of alkoxy, the guanidine salt ionic liquid has functionalized ether bonds, the dissolving capacity of the guanidine salt ionic liquid can be increased, the viscosity of the guanidine salt ionic liquid can be effectively reduced, and the electrochemical performance of the battery is improved; furthermore, the introduction of alkoxy groups allows the ionic liquid to have a lower melting point. Through electrochemical performance detection, the guanidine salt ionic liquid has better electrochemical stability and conductivity than the traditional ionic liquid.

In addition, the embodiment also provides a preparation method of the guanidine salt ionic liquid, which comprises the following steps:

Step S110, according to the molar ratio of 1: 1.1-1: 1.3 of tetramethylurea to oxalyl chloride, tetramethylurea and oxalyl chloride are stirred and react for 24-36 hours in a protective gas atmosphere at 60-80 ℃ to obtain N, N, N, N-tetramethylchloromethylammonium chloride with the structural formula as follows:

In other preferred embodiments, the molar ratio of tetramethylurea to oxalyl chloride is 1: 1.1.

Step S120, according to the molar ratio of N, N, N, N-tetramethylchloromethylammonium chloride to 2-aminoalkane of 1: 4-1: 4.1, stirring N, N, N, N-tetramethylchloromethylammonium chloride and 2-aminoalkane in a protective gas atmosphere at 60-80 ℃ for reaction, cooling, and dripping 120-200 ml of sodium hydroxide solution with the mass fraction of 35% according to the molar ratio of N, N, N, N-tetramethylchloromethylammonium chloride to sodium hydroxide of 1:21 under an ice bath condition to obtain branched alkyl guanidine salt ionic liquid with the structural formula as follows:

Wherein n is₁is 0,1 or 2.

The 2-amino alkane is specifically 2-aminopropane, 2-aminobutane and 2-aminopentane.

Extracting the obtained N, N, N, N-tetramethyl chloromethyl ammonium chloride with dichloromethane for 2-4 times, combining organic phases, drying with anhydrous magnesium sulfate, removing volatile solvent by rotary evaporation, and distilling residual liquid under reduced pressure to obtain the product alkyl guanidine salt ionic liquid with branched chains.

In other preferred embodiments, the molar ratio of N, N-tetramethylchloromethylammonium chloride to 2-aminoalkane is 1:4.

Step S130, in a protective atmosphere, stirring and reacting the branched alkyl guanidine salt ionic liquid and halogenated ether at 40-50 ℃ according to the molar ratio of the branched alkyl guanidine salt ionic liquid to the halogenated ether being 1: 1.05-1: 1.2 to obtain 1,1,3, 3-tetramethyl-2, 2-alkyl alkoxy guanidine salt halide with the following structural formula:

Wherein n is₁Is 0,1 or 2; n is₂Is 1 or 2; x is halogen.

The halogenated ether is specifically 2-bromomethyl methyl ether and 2-bromomethyl ethyl ether.

In other preferred embodiments, the molar ratio of branched alkylguanidinium ionic liquid to halogenated ether is 1: 1.05.

Step S140, mixing the synthesized 1,1,3, 3-tetramethyl-2, 2-alkyl alkoxy guanidine salt halide and inorganic salt M according to the molar ratio of 1: 1-1: 1.2⁺Y^-Respectively dissolving the mixture in deionized water, mixing and reacting at room temperature for 24-36 hours to obtain the guanidine salt ionic liquid with the following structural formula:

wherein M is⁺Is Li⁺；Y^-Is BF₄ ^-，PF₆ ^-，TFSI^-，FSI^-Or N (CN)₂ ^-. The volume ratio of the synthesized 1,1,3, 3-tetramethyl-2, 2-alkyl alkoxy guanidine salt halide to the deionized water is 1 mol: 30-50 ml.

in other preferred embodiments, the 1,1,3, 3-tetramethyl-2, 2-alkylalkoxyguanidinium halide is reacted with an inorganic salt M⁺Y^-In a molar ratio of 1:1.

in addition, the preparation method of the guanidine salt ionic liquid also comprises the step of mixing the 1,1,3, 3-tetramethyl-2, 2-alkyl alkoxy guanidine salt halide and inorganic salt M⁺Y^-And after the deionized water reacts at room temperature, separating and purifying the ionic liquid, wherein the ionic liquid separation and purification process comprises the following steps:

Extracting the mixed solution obtained after the reaction with dichloromethane for 2-4 times, washing with deionized water for several times, and checking with silver nitrate solution until the eluate does not contain halogen ions.

And (3) performing rotary evaporation on the treated solution to remove volatile dichloromethane, and drying for more than 24-36 hours under a vacuum condition to obtain the guanidine salt ionic liquid: 1,1,3, 3-tetramethyl-2, 2-alkyl alkoxy guanidine bis (trifluoromethyl sulfonyl) imide salt ionic liquid.

The preparation process of the guanidine salt ionic liquid comprises the steps of firstly preparing N, N, N, N-tetramethyl chloromethyl ammonium chloride by using tetramethylurea and oxalyl chloride, secondly reacting the N, N, N, N-tetramethyl chloromethyl ammonium chloride with 2-amino alkane and sodium hydroxide to prepare alkyl guanidine salt ionic liquid with branched chains, secondly reacting the alkyl guanidine salt ionic liquid with halogenated ether to prepare 1,1,3, 3-tetramethyl-2, 2-alkyl alkoxy guanidine salt halide, and finally carrying out ion exchange reaction on the 1,1,3, 3-tetramethyl-2, 2-alkyl alkoxy guanidine salt halide and inorganic salt containing target anions, and separating, purifying and drying the product obtained by the ion exchange reaction, namely the guanidine salt ionic liquid. The process has the advantages of easily obtained raw materials, easily controlled reaction and suitability for industrial production, and the prepared guanidine salt ionic liquid has excellent electrochemical performance and is suitable for the field of lithium ion battery electrolyte.

in addition, the embodiment also provides a guanidine salt ionic liquid electrolyte for the lithium ion battery and a preparation method thereof.

the ionic liquid electrolyte includes an organic solvent, an ionic liquid, and a lithium salt. The ionic liquid is the guanidine salt ionic liquid, the organic solvent is a mixed solution of Propylene Carbonate (PC) and dimethyl carbonate (DMC), and the volume ratio of the propylene carbonate to the dimethyl carbonate is 1: 2-1: 4. The lithium salt is LiTFSI or LiPF₆、LiBF₄Or LiBOB. The concentration of the lithium salt is 0.3-1.0 mol/kg, the mass percent of the ionic liquid is 1-20%, and the mass percent of the organic solvent is 70-90%.

Compared with the traditional lithium ion battery electrolyte, the guanidine salt ionic liquid electrolyte has higher electrochemical stability due to the introduction of the ionic liquid, and the safety performance of the battery is improved; meanwhile, the formation of an SEI film of the graphite cathode is promoted, and the cycle performance of the battery is improved.

The preparation method of the ionic liquid electrolyte comprises the following steps:

Step S210, preparing the guanidine salt ionic liquid.

and step S220, mixing the propylene carbonate and the diethyl carbonate according to the volume ratio of 1: 2-1: 4 to prepare the organic solvent.

Step S230, adding the ionic liquid into the organic solvent according to the mass percent of 1-20% of the ionic liquid and 70-90% of the organic solvent, uniformly stirring and mixing, and then adding the lithium salt into the system according to the mass percent of 1-10% until the lithium salt is completely dissolved, thereby obtaining the ionic liquid electrolyte. The lithium salt is LiTFSI or LiPF₆、LiBF₄Or LiBOB.

The guanidine salt ionic liquid electrolyte has the advantages of simple preparation process, easiness in reaction control and suitability for industrial production, and the prepared ionic liquid electrolyte has a wider electrochemical window, good electrochemical stability and good safety performance and is suitable for the field of lithium ion batteries.

The following describes the preparation of guanidine salt ionic liquid and its application in lithium ion battery electrolyte, and describes the test of the electrolyte in the aspects of performance and the like, with reference to specific examples.

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