Determination of 2-propyn-1-yl 1H imidazole-carboxylic ester in lithium ion battery electrolyte

Abstract

The invention discloses a method for determining 2-propyn-1-yl 1H imidazole-carboxylic ester in lithium ion battery electrolyte. The method comprises the following steps: preparing standard solution mother liquor with at least three gradient concentrations; preparing a standard solution; preparing a to-be-detected sample solution, wherein a methanol aqueous solution is adopted as a mobile phase; and determining: respectively determining the standard solution and the to-be-detected sample solution of each gradient concentration by adopting a high performance liquid chromatograph with a differential detector, preparing a standard solution curve according to the standard solutions, and calculating the content of the 2-propyn-1-yl 1H imidazole-carboxylic ester in the to-be-detected sample according to the peak area and the dilution ratio of the characteristic product by adopting an external standard method. The method has the advantages that the content of the 2-propyn-1-yl 1H imidazole-carboxylic ester in the lithium ion battery electrolyte can be accurately quantified, and the content of the 2-propyn-1-yl 1H imidazole-carboxylic ester can be accurately measured in the whole quality guarantee period of the lithium ion battery electrolyte.

Description

Technical Field

[0001] This invention relates to the field of component determination technology in lithium-ion battery electrolytes, specifically to a method for determining 2-propyn-1-yl-1H imidazole-carboxylic acid ester. Background Technology

[0002] The structural formula of 2-propyn-1-yl1H imidazole-carboxylic acid ester is as follows:

[0003]

[0004] Lithium-ion batteries possess characteristics such as high energy density, low maintenance, low self-discharge rate, wide operating temperature range, long cycle life, no memory effect, stable operating voltage, and environmental friendliness. They have become one of the most promising new green chemical power sources in the world and are widely used in smart products (including mobile phones, laptops, cameras, and other electronic products), power tools, and electric vehicles. With rapid technological advancements and diversified market demands, higher performance requirements are being placed on lithium-ion batteries.

[0005] Functional additives for lithium-ion batteries have become a new technological development direction, as they can specifically modify certain battery properties using relatively small doses. 2-Propyne-1-yl1H-imidazolium-carboxylic acid ester, as a novel lithium-ion electrolyte additive, can improve the cathode interface and cathode material conditions, thereby enhancing the battery's high and low temperature cycling performance and safety.

[0006] 2-Propyne-1-yl1H-imidazolium-carboxylate, as a raw material, can be tested using gas chromatography. However, in lithium-ion battery electrolytes, 2-propyne-1-yl1H-imidazolium-carboxylate is alkaline and can react with acidic additives, such as ethylene sulfate (ESA), causing its content to decrease over time. Therefore, quantitative analysis using standard solutions prepared with 2-propyne-1-yl1H-imidazolium-carboxylate presents a technical problem: different results are obtained at different times. This makes it impossible to accurately reflect the content of 2-propyne-1-yl1H-imidazolium-carboxylate in the original formula, thus hindering accurate monitoring of the production process. Summary of the Invention

[0007] The technical problem to be solved by the present invention is to provide a method for determining 2-propyn-1-yl 1H imidazole-carboxylic acid ester in lithium-ion battery electrolyte, which can accurately quantify the ester and is not affected by time within the shelf life.

[0008] To solve the above problems, the technical solution adopted by the present invention is: the determination of 2-propyn-1-yl 1H imidazole-carboxylic acid ester in lithium-ion battery electrolyte, comprising the following steps:

[0009] Prepare standard stock solutions with at least three gradient concentrations by the following steps: first, mix 2-propyn-1-yl-1H imidazole-carboxylic acid ester and propylene carbonate evenly, and then add vinyl sulfate and mix evenly.

[0010] Preparation of standard solutions: Take the stock solution of each gradient concentration, dilute it with the mobile phase, and then pre-treat it by heating, and then cool it to room temperature;

[0011] Preparation of the test sample solution: Dilute the test sample with the mobile phase, then pre-treat it by heating, and then cool it to room temperature;

[0012] The mobile phase is an aqueous methanol solution;

[0013] Determination: A high-performance liquid chromatograph with a differential detector was used to determine the standard solutions and the test sample solutions at each gradient concentration. A standard solution curve was prepared based on the standard solutions. The content of 2-propyn-1-yl-1H-imidazolium-carboxylic acid ester in the test sample was calculated based on the peak area and dilution factor of the characteristic products using the external standard method.

[0014] Further, in the determination of 2-propyn-1-yl 1H imidazole-carboxylic acid ester in the aforementioned lithium-ion battery electrolyte, three gradient concentration standard stock solutions are prepared, with the concentrations of 2-propyn-1-yl 1H imidazole-carboxylic acid ester in the three gradient standard stock solutions being (1000±20) ppm, (2000±40) ppm, and (3000±60) ppm, respectively. In each gradient concentration standard stock solution, the mass of vinyl sulfate added is 3 to 5 times the mass of 2-propyn-1-yl 1H imidazole-carboxylic acid ester. The standard solutions are prepared by taking the three gradient concentration standard stock solutions, diluting them 10 to 20 times with the mobile phase, and then pre-treating them by heating, followed by cooling to room temperature. The test sample solutions are prepared by taking the test sample, diluting it 10 to 20 times with the mobile phase, and then pre-treating it by heating, followed by cooling to room temperature.

[0015] Furthermore, in the determination of 2-propyn-1-yl 1H imidazole-carboxylic acid ester in the aforementioned lithium-ion battery electrolyte, the instrument conditions of the high-performance liquid chromatograph with differential detector include: flow rate of 0.4 ml / min, chromatographic column: C18 column, length 250 mm, inner diameter 4.6 mm, temperature 35℃; and differential detector temperature of 35℃.

[0016] Furthermore, in the determination of 2-propyn-1-yl 1H imidazole-carboxylic acid ester in the aforementioned lithium-ion battery electrolyte, the volume ratio of methanol to water in the mobile phase methanol-water solution is 45% to 55%.

[0017] Furthermore, in the determination of 2-propyn-1-yl 1H imidazole-carboxylic acid ester in the aforementioned lithium-ion battery electrolyte, the preparation steps of the mobile phase include: filtering chromatographic grade methanol through a 0.45 μm PTFE microporous membrane, and then mixing it with ultrapure water to make the volume percentage of methanol between 45% and 55%.

[0018] Furthermore, in the determination of 2-propyn-1-yl 1H imidazole-carboxylic acid ester in the aforementioned lithium-ion battery electrolyte, the heating pretreatment steps for preparing the standard solution and the sample solution to be tested include: maintaining a constant temperature in a 60°C oven for 30 minutes.

[0019] The advantages of this invention are: 1. It can accurately quantify the content of 2-propyn-1-yl 1H imidazole-carboxylic acid ester in lithium-ion battery electrolyte. 2. It can be used for monitoring the production process, solving the technical problem of inaccurate detection when too much or too little 2-propyn-1-yl 1H imidazole-carboxylic acid ester is added in the current production process. 3. The content of 2-propyn-1-yl 1H imidazole-carboxylic acid ester can be accurately determined throughout the entire shelf life of the lithium-ion battery electrolyte. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the standard solution curve in a specific implementation method. Detailed Implementation

[0021] The present invention will now be described in further detail.

[0022] To simplify the explanation, the English abbreviations used in the instruction manual are as follows:

[0023] PImC----2-propyn-1-yl1H imidazole-carboxylic acid ester;

[0024] PC --- Propylene carbonate;

[0025] ESA – Vinyl sulfate;

[0026] HPLC – High Performance Liquid Chromatography.

[0027] The determination of 2-propyn-1-yl 1H imidazole-carboxylic acid ester in the lithium-ion battery electrolyte of the present invention includes the following steps.

[0028] 1. Preparation of mobile phase: Filter chromatographic grade methanol through a 0.45µm PTFE microporous membrane, and then mix it with ultrapure water until the volume percentage of methanol is between 45% and 55%.

[0029] II. Preparation of stock solutions for standard solutions: Prepare three concentration gradients using PC medium as shown in Table 1 below. Note that ESA should be added only after the PC and PIMC are thoroughly mixed, and then stirred until homogeneous.

[0030] Table 1:

[0031]

[0032] For the selection of the medium, common carbonate and carboxylic acid ester solvents used in lithium-ion electrolytes, such as DMC, EMC, DEC, PC, EP, and PP, were tested. PC was chosen as the medium for the standard solution stock solution because of its high boiling point (242℃), low melting point (-48.8℃), and viscosity and density similar to those of lithium-ion battery electrolytes.

[0033] Regarding the selection of acidic additives, ESA and PS were tested. It was confirmed that 2-propyn-1-yl-1H imidazole-carboxylate is compatible with ESA and can convert 2-propyn-1-yl-1H imidazole-carboxylate into a stable characteristic product.

[0034] A standard solution of 2-propyn-1-yl 1H imidazole-carboxylic acid ester was prepared in PC medium and ESA was introduced. This converted 2-propyn-1-yl 1H imidazole-carboxylic acid ester into a stable characteristic product, which was then analyzed by HPLC. This greatly improved the accuracy of the determination of the content of 2-propyn-1-yl 1H imidazole-carboxylic acid ester.

[0035] III. Preparation of standard solutions: The stock solutions of the three gradient standard solutions prepared in step II are diluted 10-20 times with the mobile phase, kept at a constant temperature of 60℃ for 30 minutes, and then removed and cooled to room temperature.

[0036] IV. Preparation of the sample solution: Take the sample to be tested, dilute it 10-20 times with the mobile phase, keep it in a 60℃ oven for 30 minutes, remove it, and cool it to room temperature. See Table 3 for specific dilution factors.

[0037] V. Using a high-performance liquid chromatograph with a differential detector, the standard solutions and the sample solution at three different concentration gradients were measured respectively. A standard solution curve (CA curve, where C represents the concentration of the standard solution and A represents the peak area of ​​the characteristic product) was constructed based on the three concentration gradients of the standard solutions. Figure 1 As shown. The content of 2-propyn-1-yl-1H-imidazolium-carboxylic acid ester in the sample was calculated using the external standard method based on the peak area and dilution factor of the characteristic product.

[0038] The instrument conditions are shown in Table 2.

[0039] Table 2:

[0040] Flow rate 0.4 ml / min chromatographic column, temperature C18 column (250 mm long – 4.6 mm inner diameter), 35℃ Detector, temperature Differential detector, 35℃

[0041] The test results of the samples are shown in Table 3.

[0042] Table 3:

[0043]

[0044] The reliability of the determination method described in this invention is verified by the recovery rate experiment below.

[0045] A certain amount of 2-propyn-1-yl 1H imidazole-carboxylic acid ester was added to sample A to obtain A1. A and A1 were tested under the same conditions to see if the difference between the detected values ​​of A1 and A matched the theoretical increase. The data are shown in Table 4.

[0046] Table 4:

[0047]

[0048] As can be seen from the table above, the spiked recovery rate is between 98% and 101.3%, which shows that the determination method described in this invention has good reliability, stability and high accuracy.

[0049] The advantages of this invention are: 1. It can accurately quantify the content of 2-propyn-1-yl 1H imidazole-carboxylic acid ester in lithium-ion battery electrolyte. 2. It can be used for monitoring the production process, solving the technical problem of inaccurate detection when too much or too little 2-propyn-1-yl 1H imidazole-carboxylic acid ester is added in the current production process. 3. The content of 2-propyn-1-yl 1H imidazole-carboxylic acid ester can be accurately determined throughout the entire shelf life of the lithium-ion battery electrolyte.

Claims

1. A method for determining 2-propyn-1-yl 1H imidazole-carboxylate in electrolyte of lithium ion battery, comprising the following steps: preparing at least three standard solution mother liquor of gradient concentration, including the following steps: firstly mixing 2-propyn-1-yl 1H imidazole-carboxylate and propylene carbonate uniformly, and then adding ethylene sulfate uniformly; preparing standard solution: taking each standard solution mother liquor of gradient concentration, respectively diluting with mobile phase, and then respectively performing heating pretreatment, and then cooling to room temperature; preparing sample solution to be determined: taking sample to be determined, diluting with mobile phase, and then respectively performing heating pretreatment, and then cooling to room temperature; the mobile phase is methanol aqueous solution; determining: using high performance liquid chromatograph with differential detector, respectively determining each standard solution of gradient concentration and sample solution to be determined, preparing standard solution curve according to standard solution, and using external standard method to calculate the content of 2-propyn-1-yl 1H imidazole-carboxylate in sample to be determined according to peak area of characteristic product and dilution multiple.

2. The determination of 2-propyn-l-yl 1 H imidazole-carboxylate in lithium-ion battery electrolytes according to claim 1, characterized in that: preparing three standard solution mother liquor of gradient concentration, the concentration of 2-propyn-1-yl 1H imidazole-carboxylate in three standard solution mother liquor of gradient concentration is respectively: (1000±20) ppm, (2000±40) ppm, (3000±60) ppm, and the added mass of ethylene sulfate in each standard solution mother liquor of gradient concentration is 3-5 times of the mass of 2-propyn-1-yl 1H imidazole-carboxylate; preparing standard solution: respectively taking three standard solution mother liquor of gradient concentration, respectively diluting 10-20 times with mobile phase, and then respectively performing heating pretreatment, and then cooling to room temperature; preparing sample solution to be determined: taking sample to be determined, diluting 10-20 times with mobile phase, and then respectively performing heating pretreatment, and then cooling to room temperature.

3. The determination of 2-propyn-l-yl 1 H imidazole-carboxylate in lithium-ion battery electrolytes according to claim 1 or 2, characterized in that: The instrument conditions of high performance liquid chromatograph with differential detector include: flow rate is 0.4 ml / min, chromatographic column is C18 chromatographic column with length of 250 mm and inner diameter of 4.6 mm, temperature is 35℃, and the temperature of differential detector is 35℃.

4. The determination of 2-propyn-l-yl 1 H imidazole-carboxylate in lithium ion battery electrolytes according to claim 1 or 2, characterized in that: The volume ratio of methanol to water in the mobile phase methanol aqueous solution is 45%-55%.

5. The determination of 2-propyn-l-yl 1 H imidazole-carboxylate in lithium-ion battery electrolytes according to claim 4, characterized in that: The preparation steps of mobile phase include: filtering chromatographic grade methanol with 0.45 um PTFE microporous filter membrane, and then mixing with ultrapure water to make the volume percentage of methanol between 45%-55%.

6. The determination of 2-propyn-l-yl 1 H imidazole-carboxylate in lithium-ion battery electrolytes according to claim 1 or 2, characterized in that: The heating pretreatment steps when preparing standard solution and sample solution to be determined include: constant temperature in 60℃ oven for 30 minutes.

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