Method for testing content of chloride ions or sulfate ions in lithium difluoro (oxalato) borate

Abstract

The invention belongs to the technical field of chemical substance testing, and particularly relates to a method for testing the content of chloride ions or sulfate ions in lithium difluoro (oxalato) borate, which at least comprises the following steps: 1, sample pretreatment; the preparation method comprises the following steps: adding lithium difluoro (oxalato) borate into a magnesium salt / calcium salt aqueous solution, uniformly mixing, filtering to remove insoluble substances when the solution is in a milky white opaque state, and taking clear liquid for later use; 2, detecting chloride ions or sulfate ions; (1) sample turbidity test; (2) standard substance turbidity test; and (3) result judgment. Compared with the prior art, through ingenious pretreatment, magnesium salt / calcium salt is added into a lithium difluoro (oxalato) borate system, and generated oxalate is removed firstly. Therefore, the interference of oxalate on the test of chloride ions and sulfate ions can be eliminated, and the test accuracy is greatly improved.

Description

Technical Field

[0001] The invention belongs to the technical field of chemical substance testing, and particularly relates to a method for testing the content of chloride ions or sulfate ions in lithium difluorooxalatoborate. Background Art

[0002] Turbidimetry is also called turbidity measurement. It is a method of measuring the intensity of light passing through a suspended particle medium to determine the concentration of suspended matter. It is a light scattering measurement technique. It uses the intensity of transmitted light (I) and the intensity of incident light (I o ) ratio I / I o , or the scattered light intensity (I s ) and the incident light intensity (I o ) ratio I s / I o , a method for determining the content of suspended matter.

[0003] There is a patent application that attempts to use turbidimetry to test the chloride ion content in lithium difluorooxalate borate. The principle is to add silver nitrate and nitric acid. The silver chloride produced does not dissolve in the acid, so turbidity is produced. By comparing it with the turbidity of the standard, the chloride ion content can be obtained. Lithium difluorooxalate borate decomposes into oxalate when it comes into contact with water. After adding silver nitrate and nitric acid, it reacts with oxalic acid and produces precipitates to form interference. Therefore, the turbidimetry method cannot accurately test the chloride ion content in lithium difluorooxalate borate.

[0004] Lithium difluorooxalatoborate is a commonly used functional additive in lithium-ion battery systems. During its production process, it is inevitable that chloride ions and sulfate ions will be introduced as impurities. A certain amount of chloride ions and sulfate ions in the lithium-ion battery system will reduce the performance and life of the battery. Therefore, it is particularly necessary to detect the chloride ion and sulfate ion content in lithium difluorooxalatoborate.

[0005] In view of this, the present invention aims to provide a method for testing the chloride ion or sulfate ion content in lithium difluorooxalatoborate, which removes the generated oxalate by adding magnesium salt or calcium salt through clever pretreatment, thereby eliminating the interference of oxalate on the chloride ion and sulfate ion test, thereby greatly improving the accuracy of the test. Summary of the invention

[0006] The purpose of the present invention is to provide a method for testing the content of chloride ions or sulfate ions in lithium difluorooxalatoborate in view of the deficiencies of the prior art. The method removes the generated oxalate ions by adding magnesium salt or calcium salt through clever pretreatment, thereby eliminating the interference of oxalate ions on the test of chloride ions and sulfate ions, thereby greatly improving the accuracy of the test.

[0007] In order to achieve the above object, the present invention adopts the following technical solution:

[0008] A method for testing the chloride ion or sulfate ion content in lithium difluorooxalatoborate, comprising at least the following steps:

[0009] The first step is sample pretreatment: add lithium difluorooxalatoborate to a magnesium salt or calcium salt aqueous solution, mix well, wait until the solution becomes milky white and opaque, filter to remove insoluble matter, and take the clear solution for later use;

[0010] The second step is the detection of chloride ions or sulfate ions;

[0011] (I) Sample turbidity test

[0012] When testing chloride ions, take the lithium difluorooxalate borate filtrate obtained in the first step, place it in a standard turbidity bottle, add ultrapure water, nitric acid solution, and silver nitrate solution in sequence and shake well, let it stand in a dark room, and measure the turbidity value with a desktop turbidity meter;

[0013] When testing sulfate ions, take the lithium difluorooxalate borate filtrate obtained in the first step, place it in a standard turbidity bottle, add ultrapure water, nitric acid solution, and barium chloride solution in sequence and shake well, let it stand in a dark room, and measure the turbidity value with a desktop turbidity meter;

[0014] (II) Turbidity test of standard products

[0015] When testing chloride ions, take the chloride ion standard solution, place it in a standard turbidity bottle, add magnesium salt or calcium salt (variable for controlling turbidity comparison experiment) aqueous solution, ultrapure water, nitric acid solution, silver nitrate solution in sequence and shake well, let it stand in a dark room, and measure the turbidity value with a desktop turbidity meter;

[0016] When testing sulfate ions, take sulfate standard solution, place it in a standard turbidity bottle, add magnesium salt or calcium salt (variable for controlling turbidity comparison experiment) aqueous solution, ultrapure water, nitric acid solution, barium chloride solution in sequence and shake well, let it stand in a dark room, and measure the turbidity value with a desktop turbidity meter;

[0017] (III) Result determination

[0018] Compare the sample bottle and the standard bottle by turbidimetry. If the turbidity of the sample tube does not exceed that of the standard bottle, it can be determined that the chloride ion in the sample is less than or equal to the concentration of the corresponding standard solution in the standard tube. Otherwise, it can be determined that the chloride ion in the sample is greater than the concentration of the corresponding standard solution in the standard bottle.

[0019] As an improvement of the method for testing the chloride ion or sulfate ion content in lithium difluorooxalatoborate of the present invention, the magnesium salt is magnesium bis(fluorosulfonyl)imide, magnesium nitrate, magnesium trifluoromethylsulfonylimide, magnesium trifluoromethylsulfonate or magnesium perchlorate.

[0020] As an improvement of the method for testing the chloride ion or sulfate ion content in lithium difluorooxalatoborate of the present invention, the calcium salt is calcium bis(fluorosulfonyl)imide, calcium nitrate, calcium trifluoromethylsulfonylimide, calcium trifluoromethylsulfonate or calcium perchlorate.

[0021] As an improvement of the method for testing the chloride ion or sulfate ion content in lithium difluorooxalatoborate of the present invention, in the first step, the molar ratio of lithium difluorooxalatoborate to magnesium salt is 1:0.5-1:10.

[0022] As an improvement of the method for testing the chloride ion or sulfate ion content in lithium difluorooxalatoborate of the present invention, in the first step, the molar ratio of lithium difluorooxalatoborate to calcium salt is 1:0.5-1:10.

[0023] As an improvement of the method for testing the chloride ion or sulfate ion content in lithium difluorooxalate borate of the present invention, in the first step, the mixing method is: firstly add a stirring bar into the mixed system of lithium difluorooxalate borate and magnesium salt or calcium salt aqueous solution, stir for 5-30 minutes, and then ultrasonicate at 40°C-80°C for 10-60 minutes.

[0024] As an improvement of the method for testing the chloride ion or sulfate ion content in lithium difluorooxalatoborate of the present invention, in the first step, filtration uses a 0.22-0.45 mm organic nylon filter membrane.

[0025] As an improvement of the method for testing the content of chloride ions or sulfate ions in lithium difluorooxalate borate of the present invention, in the sample turbidity testing step, when testing chloride ions, the mass ratio of lithium difluorooxalate borate, ultrapure water, nitric acid, and silver nitrate is 1:(0.5-5):(0.5-5):(0.1-2); when testing sulfate ions, the mass ratio of lithium difluorooxalate borate, ultrapure water, nitric acid, and barium chloride is 1:(0.5-5):(0.5-5):(0.1-2).

[0026] As an improvement of the method for testing the chloride ion or sulfate ion content in lithium difluorooxalatoborate of the present invention, in the standard turbidity test step, when testing chloride ions, the mass ratio of chloride ion standard solution, magnesium salt / calcium salt, ultrapure water, nitric acid, and silver nitrate is 1:(1-30):(10-30):(1-10):(1-5).

[0027] As an improvement of the method for testing the chloride ion or sulfate ion content in lithium difluorooxalatoborate of the present invention, in the standard turbidity test step, when testing sulfate ions, the mass ratio of sulfate standard solution, magnesium salt / calcium salt, ultrapure water, nitric acid, and barium chloride is 1:(1-30):(10-30):(1-10):(1-5).

[0028] Compared with the prior art, since lithium difluorooxalatoborate decomposes into oxalate when it meets water, and reacts with oxalic acid to generate precipitates after silver nitrate and nitric acid are added, the present invention removes the generated oxalate by adding magnesium salt / calcium salt through clever pre-treatment, thereby eliminating the test interference caused by oxalate, and then silver nitrate / barium chloride and nitric acid are added, and the generated silver chloride / barium sulfate does not dissolve in the acid, generating turbidity, and the turbidity of the turbidity can be compared with that of the standard to obtain the content of chloride ions and sulfate ions, thereby greatly improving the accuracy of the test. DETAILED DESCRIPTION

[0029] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the specific embodiments of the present invention are described in detail below.

[0030] In the following description, many specific details are set forth to facilitate a full understanding of the present invention, but the present invention may also be implemented in other ways different from those described herein, and those skilled in the art may make similar generalizations without violating the connotation of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0032] Example 1

[0033] This embodiment provides a method for testing the chloride ion content in lithium difluorooxalatoborate, which at least comprises the following steps:

[0034] The first step is sample pretreatment

[0035] Take 1g of lithium difluorooxalatoborate (LiDFOB) sample and add it to 12g of 20wt% magnesium bistrifluorosulfonyl imide (Mg(TFSI)2) aqueous solution. Add a stirrer, stir the mixture for 15 minutes and then ultrasonicate at 60℃ for 30 minutes. When the solution becomes milky white and opaque, filter it with a 0.22mm organic nylon filter membrane to remove insoluble matter, and take the clear solution for later use.

[0036] Step 2: Chloride ion detection

[0037] 2.1 Sample turbidity test

[0038] Take 2.600g of the lithium difluorooxalate borate filtrate obtained in the previous step, place it in a standard turbidity bottle, add 2.000g of ultrapure water, 1mL of 30wt% nitric acid solution, and 0.5mL of 1.5wt% silver nitrate solution in sequence and shake well. Let it stand in a dark room for 10 minutes. Use a WGZ-200 desktop turbidity meter to measure the turbidity value.

[0039] 2.2 Standard turbidity test

[0040] Take 0.200g of chloride ion standard solution, place it in a standard turbidity bottle, add 2.400g of 20wt% Mg(TFSI)2 aqueous solution, 2.000g of ultrapure water, 1mL of 30wt% nitric acid solution, 0.5mL of 1.5wt% silver nitrate solution in sequence and shake well. Let it stand in a dark room for 10 minutes. Use WGZ-200 desktop turbidity meter to measure the turbidity value.

[0041] 2.3 Result determination

[0042] Compare the sample bottle and the standard bottle by turbidimetry. If the turbidity of the sample tube does not exceed that of the standard bottle, it can be determined that the chloride ion in the sample is less than or equal to the concentration of the corresponding standard solution in the standard tube. Otherwise, it can be determined that the chloride ion in the sample is greater than the concentration of the corresponding standard solution in the standard bottle.

[0043] Example 2

[0044] This embodiment provides a method for testing the chloride ion content in lithium difluorooxalatoborate, which at least comprises the following steps:

[0045] The first step is sample pretreatment

[0046] Take 1g of lithium difluorooxalatoborate (LiDFOB) sample and add it to 10g of 20wt% magnesium nitrate (Mg(NO3)2) aqueous solution. Add a stirrer and stir the mixture for 18 minutes and then ultrasonicate at 70℃ for 25 minutes. When the solution becomes milky white and opaque, filter it with a 0.45mm organic nylon filter membrane to remove insoluble matter and take the clear solution for later use.

[0047] Step 2: Chloride ion detection

[0048] 2.1 Sample turbidity test

[0049] Take 2.200g of the lithium difluorooxalate borate filtrate obtained in the previous step, place it in a standard turbidity bottle, add 2.000g of ultrapure water, 1mL of 30wt% nitric acid solution, and 0.5mL of 1.5wt% silver nitrate solution in sequence and shake well. Let it stand in a dark room for 10 minutes. Use a WGZ-200 desktop turbidity meter to measure the turbidity value.

[0050] 2.2 Standard turbidity test

[0051] Take 0.200g of chloride ion standard solution, place it in a standard turbidity bottle, add 2.000g of 20wt% Mg(NO3)2 aqueous solution, 2.000g of ultrapure water, 1mL of 30wt% nitric acid solution, 0.5mL of 1.5wt% silver nitrate solution and shake well. Let it stand in a dark room for 10 minutes. Use WGZ-200 desktop turbidity meter to measure the turbidity value.

[0052] 2.3 Result determination

[0053] Compare the sample bottle and the standard bottle by turbidimetry. If the turbidity of the sample tube does not exceed that of the standard bottle, it can be determined that the chloride ion in the sample is less than or equal to the concentration of the corresponding standard solution in the standard tube. Otherwise, it can be determined that the chloride ion in the sample is greater than the concentration of the corresponding standard solution in the standard bottle.

[0054] Example 3

[0055] This embodiment provides a method for testing the chloride ion content in lithium difluorooxalatoborate, which at least comprises the following steps:

[0056] The first step is sample pretreatment

[0057] Take 1g of lithium difluorooxalatoborate (LiDFOB) sample and add it to 20g of 20wt% magnesium bis(fluorosulfonyl)imide (Mg(FSI)2) aqueous solution. Add a stirrer, stir the mixture for 15 minutes and then ultrasonicate at 60℃ for 30 minutes. When the solution becomes milky white and opaque, filter it with a 0.22mm organic nylon filter membrane to remove insoluble matter, and take the clear solution for later use.

[0058] Step 2: Chloride ion detection

[0059] 2.1 Sample turbidity test

[0060] Take 4.200g of the lithium difluorooxalate borate filtrate obtained in the previous step, place it in a standard turbidity bottle, add 2.000g of ultrapure water, 1mL of 30wt% nitric acid solution, and 0.5mL of 1.5wt% silver nitrate solution in sequence and shake well. Let it stand in a dark room for 10 minutes. Use a WGZ-200 desktop turbidity meter to measure the turbidity value.

[0061] 2.2 Standard turbidity test

[0062] Take 0.200g of chloride ion standard solution, place it in a standard turbidity bottle, add 4.000g of 20wt% Mg(FSI)2 aqueous solution, 2.000g of ultrapure water, 1mL of 30wt% nitric acid solution, 0.5mL of 1.5wt% silver nitrate solution and shake well. Let it stand in a dark room for 10 minutes. Use WGZ-200 desktop turbidity meter to measure the turbidity value.

[0063] 2.3 Result determination

[0064] Compare the sample bottle and the standard bottle by turbidimetry. If the turbidity of the sample tube does not exceed that of the standard bottle, it can be determined that the chloride ion in the sample is less than or equal to the concentration of the corresponding standard solution in the standard tube. Otherwise, it can be determined that the chloride ion in the sample is greater than the concentration of the corresponding standard solution in the standard bottle.

[0065] Example 4

[0066] This embodiment provides a method for testing the chloride ion content in lithium difluorooxalatoborate, which at least comprises the following steps:

[0067] The first step is sample pretreatment

[0068] Take 1g lithium difluorooxalatoborate (LiDFOB) sample and add it to 15g 20wt% calcium trifluoromethanesulfonate (Ca(CF3SO2)2 aqueous solution. Add a stirrer, stir the mixture for 12 minutes and then ultrasonicate at 65°C for 40 minutes. When the solution becomes milky white and opaque, filter it with a 0.22mm organic nylon filter membrane to remove insoluble matter, and take the clear solution for later use.

[0069] Step 2: Chloride ion detection

[0070] 2.1 Sample turbidity test

[0071] Take 3.200g of the lithium difluorooxalate borate filtrate obtained in the previous step, place it in a standard turbidity bottle, add 2.000g of ultrapure water, 1mL of 30wt% nitric acid solution, and 0.5mL of 1.5wt% silver nitrate solution in sequence and shake well. Let it stand in a dark room for 10 minutes. Use a WGZ-200 desktop turbidity meter to measure the turbidity value.

[0072] 2.2 Standard turbidity test

[0073] Take 0.200g of chloride ion standard solution, place it in a standard turbidity bottle, add 3.000g of 20wt% Ca(CF3SO2)2 aqueous solution, 2.000g of ultrapure water, 1mL of 30wt% nitric acid solution, 0.5mL of 1.5wt% silver nitrate solution and shake well. Let it stand in a dark room for 10 minutes. Use WGZ-200 desktop turbidity meter to measure the turbidity value.

[0074] 2.3 Result determination

[0075] Compare the sample bottle and the standard bottle by turbidimetry. If the turbidity of the sample tube does not exceed that of the standard bottle, it can be determined that the chloride ion in the sample is less than or equal to the concentration of the corresponding standard solution in the standard tube. Otherwise, it can be determined that the chloride ion in the sample is greater than the concentration of the corresponding standard solution in the standard bottle.

[0076] Example 5

[0077] This embodiment provides a method for testing the chloride ion content in lithium difluorooxalatoborate, which at least comprises the following steps:

[0078] The first step is sample pretreatment

[0079] Take 1g of lithium difluorooxalatoborate (LiDFOB) sample and add it to 18g of 20wt% magnesium perchlorate (Mg(ClO4)2) aqueous solution. Add a stirrer, stir the mixture for 15 minutes and then ultrasonicate at 60℃ for 30 minutes. When the solution becomes milky white and opaque, filter it with a 0.22mm organic nylon filter membrane to remove insoluble matter, and take the clear solution for later use.

[0080] Step 2: Chloride ion detection

[0081] 2.1 Sample turbidity test

[0082] Take 3.800g of the lithium difluorooxalate borate filtrate obtained in the previous step, place it in a standard turbidity bottle, add 2.000g of ultrapure water, 1mL of 30wt% nitric acid solution, and 0.5mL of 1.5wt% silver nitrate solution in sequence and shake well. Let it stand in a dark room for 10 minutes. Use a WGZ-200 desktop turbidity meter to measure the turbidity value.

[0083] 2.2 Standard turbidity test

[0084] Take 0.200g of chloride ion standard solution, place it in a standard turbidity bottle, add 3.600g of 20wt% Mg(ClO4)2 aqueous solution, 2.000g of ultrapure water, 1mL of 30wt% nitric acid solution, 0.5mL of 1.5wt% silver nitrate solution and shake well. Let it stand in a dark room for 10 minutes. Use WGZ-200 desktop turbidity meter to measure the turbidity value.

[0085] 2.3 Result determination

[0086] Compare the sample bottle and the standard bottle by turbidimetry. If the turbidity of the sample tube does not exceed that of the standard bottle, it can be determined that the chloride ion in the sample is less than or equal to the concentration of the corresponding standard solution in the standard tube. Otherwise, it can be determined that the chloride ion in the sample is greater than the concentration of the corresponding standard solution in the standard bottle.

[0087] Example 6

[0088] This embodiment provides a method for testing the sulfate ion content in lithium difluorooxalatoborate, which at least comprises the following steps:

[0089] The first step is sample pretreatment

[0090] Take 1g of lithium difluorooxalatoborate (LiDFOB) sample and add it to 11g of 20wt% calcium bistrifluorosulfonyl imide (Ca(TFSI)2) aqueous solution. Add a stirrer, stir the mixture for 25 minutes and then ultrasonicate at 50℃ for 35 minutes. When the solution becomes milky white and opaque, filter it with a 0.22mm organic nylon filter membrane to remove insoluble matter, and take the clear solution for later use.

[0091] Step 2: Sulfate ion detection

[0092] 2.1 Sample turbidity test

[0093] Take 2.500g of the lithium difluorooxalate borate filtrate obtained in the previous step, place it in a standard turbidity bottle, add 2.000g of ultrapure water, 1mL of 30wt% nitric acid solution, and 0.5mL of 1.5wt% barium chloride solution in sequence and shake well. Let it stand in a dark room for 10 minutes. Use a WGZ-200 desktop turbidity meter to measure the turbidity value.

[0094] 2.2 Standard turbidity test

[0095] Take 0.200g of sulfate standard solution and place it in a standard turbidity bottle. Then add 2.400g of 20wt% Ca(TFSI)2 aqueous solution, 2.000g of ultrapure water, 1mL of 30wt% nitric acid solution, and 0.5mL of 1.5wt% barium chloride solution and shake well. Let it stand in a dark room for 15 minutes. Use a WGZ-200 tabletop turbidity meter to measure the turbidity value.

[0096] 2.3 Result determination

[0097] Compare the sample bottle and the standard bottle by turbidimetry. If the turbidity of the sample tube does not exceed that of the standard bottle, it can be determined that the sulfate ion in the sample is less than or equal to the concentration of the corresponding standard solution in the standard tube. Otherwise, it can be determined that the sulfate ion in the sample is greater than the concentration of the corresponding standard solution in the standard bottle.

[0098] Example 7

[0099] This embodiment provides a method for testing the sulfate ion content in lithium difluorooxalatoborate, which at least comprises the following steps:

[0100] The first step is sample pretreatment

[0101] Take 1.2g lithium difluorooxalatoborate (LiDFOB) sample and add it to 10g 20wt% magnesium nitrate (Mg(NO3)2) aqueous solution. Add a stirrer, stir the mixture for 18 minutes and then ultrasonicate at 70℃ for 25 minutes. When the solution is milky white and opaque, filter it with a 0.45mm organic nylon filter membrane to remove insoluble matter, and take the clear solution for later use.

[0102] Step 2: Sulfate ion detection

[0103] 2.1 Sample turbidity test

[0104] Take 2.200g of the lithium difluorooxalate borate filtrate obtained in the previous step, place it in a standard turbidity bottle, add 2.000g of ultrapure water, 1mL of 30wt% nitric acid solution, and 0.5mL of 1.5wt% barium chloride solution in sequence and shake well. Let it stand in a dark room for 9 minutes. Use a WGZ-200 desktop turbidity meter to measure the turbidity value.

[0105] 2.2 Standard turbidity test

[0106] Take 0.200g of sulfate standard solution and place it in a standard turbidity bottle. Then add 2.500g of 20wt% Mg(NO3)2 aqueous solution, 2.000g of ultrapure water, 1mL of 30wt% nitric acid solution, and 0.5mL of 1.5wt% barium chloride solution and shake well. Let it stand in a dark room for 9 minutes. Use a WGZ-200 tabletop turbidity meter to measure the turbidity value.

[0107] 2.3 Result determination

[0108] Compare the sample bottle and the standard bottle by turbidimetry. If the turbidity of the sample tube does not exceed that of the standard bottle, it can be determined that the sulfate ion in the sample is less than or equal to the concentration of the corresponding standard solution in the standard tube. Otherwise, it can be determined that the sulfate ion in the sample is greater than the concentration of the corresponding standard solution in the standard bottle.

[0109] Example 8

[0110] This embodiment provides a method for testing the sulfate ion content in lithium difluorooxalatoborate, which at least comprises the following steps:

[0111] The first step is sample pretreatment

[0112] Take 1.3g lithium difluorooxalatoborate (LiDFOB) sample and add it to 20g 20wt% magnesium bis(fluorosulfonyl)imide (Mg(FSI)2) aqueous solution. Add a stirrer, stir the mixture for 12 minutes and then ultrasonicate at 60℃ for 45 minutes. When the solution becomes milky white and opaque, filter it with a 0.22mm organic nylon filter membrane to remove insoluble matter, and take the clear solution for later use.

[0113] Step 2: Sulfate ion detection

[0114] 2.1 Sample turbidity test

[0115] Take 4.200g of the lithium difluorooxalate borate filtrate obtained in the previous step, place it in a standard turbidity bottle, add 2.000g of ultrapure water, 1mL of 30wt% nitric acid solution, and 0.5mL of 1.5wt% barium chloride solution in sequence and shake well. Let it stand in a dark room for 10 minutes. Use a WGZ-200 desktop turbidity meter to measure the turbidity value.

[0116] 2.2 Standard turbidity test

[0117] Take 0.200g of sulfate standard solution and place it in a standard turbidity bottle. Then add 4.000g of 20wt% Mg(FSI)2 aqueous solution, 2.000g of ultrapure water, 1mL of 30wt% nitric acid solution, and 0.5mL of 1.5wt% barium chloride solution and shake well. Let it stand in a dark room for 10 minutes. Use a WGZ-200 tabletop turbidity meter to measure the turbidity value.

[0118] 2.3 Result determination

[0119] Compare the sample bottle and the standard bottle by turbidimetry. If the turbidity of the sample tube does not exceed that of the standard bottle, it can be determined that the sulfate ion in the sample is less than or equal to the concentration of the corresponding standard solution in the standard tube. Otherwise, it can be determined that the sulfate ion in the sample is greater than the concentration of the corresponding standard solution in the standard bottle.

[0120] Example 9

[0121] This embodiment provides a method for testing the sulfate ion content in lithium difluorooxalatoborate, which at least comprises the following steps:

[0122] The first step is sample pretreatment

[0123] Take 0.9g lithium difluorooxalatoborate (LiDFOB) sample and add it to 15g 20wt% magnesium trifluoromethanesulfonate (Mg(CF3SO2)2) aqueous solution. Add a stirrer, stir the mixture for 12 minutes and then ultrasonicate at 65℃ for 40 minutes. When the solution is milky white and opaque, filter it with a 0.22mm organic nylon filter membrane to remove insoluble matter, and take the clear solution for use.

[0124] Step 2: Sulfate ion detection

[0125] 2.1 Sample turbidity test

[0126] Take 3.200g of the lithium difluorooxalate borate filtrate obtained in the previous step, place it in a standard turbidity bottle, add 2.000g of ultrapure water, 1mL of 30wt% nitric acid solution, and 0.5mL of 1.5wt% barium chloride solution in sequence and shake well. Let it stand in a dark room for 10 minutes. Use a WGZ-200 desktop turbidity meter to measure the turbidity value.

[0127] 2.2 Standard turbidity test

[0128] Take 0.200g of sulfate standard solution, place it in a standard turbidity bottle, add 3.000g of 20wt% Mg(CF3SO2)2 aqueous solution, 2.000g of ultrapure water, 1mL of 30wt% nitric acid solution, 0.5mL of 1.5wt% barium chloride solution and shake well. Let it stand in a dark room for 10 minutes. Use WGZ-200 desktop turbidity meter to measure the turbidity value.

[0129] 2.3 Result determination

[0130] Compare the sample bottle and the standard bottle by turbidimetry. If the turbidity of the sample tube does not exceed that of the standard bottle, it can be determined that the sulfate ion in the sample is less than or equal to the concentration of the corresponding standard solution in the standard tube. Otherwise, it can be determined that the sulfate ion in the sample is greater than the concentration of the corresponding standard solution in the standard bottle.

[0131] Example 10

[0132] This embodiment provides a method for testing the chloride ion content in lithium difluorooxalatoborate, which at least comprises the following steps:

[0133] The first step is sample pretreatment

[0134] Take 1g of lithium difluorooxalatoborate (LiDFOB) sample and add it to 18g of 20wt% calcium perchlorate (Ca(ClO4)2) aqueous solution. Add a stirrer, stir the mixture for 10 minutes and then ultrasonicate at 75℃ for 20 minutes. When the solution becomes milky white and opaque, filter it with a 0.22mm organic nylon filter membrane to remove insoluble matter, and take the clear solution for later use.

[0135] Step 2: Sulfate ion detection

[0136] 2.1 Sample turbidity test

[0137] Take 3.800g of the lithium difluorooxalate borate filtrate obtained in the previous step, place it in a standard turbidity bottle, add 2.000g of ultrapure water, 1mL of 30wt% nitric acid solution, and 0.5mL of 1.5wt% barium chloride solution in sequence and shake well. Let it stand in a dark room for 10 minutes. Use a WGZ-200 desktop turbidity meter to measure the turbidity value.

[0138] 2.2 Standard turbidity test

[0139] Take 0.200g of sulfate standard solution, place it in a standard turbidity bottle, add 3.600g of 20wt% Ca(ClO4)2 aqueous solution, 2.000g of ultrapure water, 1mL of 30wt% nitric acid solution, 0.5mL of 1.5wt% barium chloride solution and shake well. Let it stand in a dark room for 10 minutes. Use WGZ-200 desktop turbidity meter to measure the turbidity value.

[0140] 2.3 Result determination

[0141] Compare the sample bottle and the standard bottle by turbidimetry. If the turbidity of the sample tube does not exceed that of the standard bottle, it can be determined that the sulfate ion in the sample is less than or equal to the concentration of the corresponding standard solution in the standard tube. Otherwise, it can be determined that the sulfate ion in the sample is greater than the concentration of the corresponding standard solution in the standard bottle.

[0142] According to the disclosure and teaching of the above description, those skilled in the art to which the present invention belongs may also make changes and modifications to the above embodiments. Therefore, the present invention is not limited to the specific embodiments disclosed and described above, and some modifications and changes to the present invention should also fall within the scope of protection of the claims of the present invention. In addition, although some specific terms are used in this specification, these terms are only for the convenience of description and do not constitute any limitation to the present invention.

Claims

1. A method for testing the chloride ion or sulfate ion content in lithium difluorooxalatoborate, characterized in that: At least the following steps are included: The first step is sample pretreatment: add lithium difluorooxalatoborate to a magnesium salt or calcium salt aqueous solution, mix well, wait until the solution becomes milky white and opaque, filter to remove insoluble matter, and take the clear solution for later use; The second step is the detection of chloride ions or sulfate ions; (I) Sample turbidity test When testing chloride ions, take the lithium difluorooxalate borate filtrate obtained in the first step, place it in a standard turbidity bottle, add ultrapure water, nitric acid solution, and silver nitrate solution in sequence and shake well, let it stand in a dark room, and measure the turbidity value with a desktop turbidity meter; When testing sulfate ions, take the lithium difluorooxalate borate filtrate obtained in the first step, place it in a standard turbidity bottle, add ultrapure water, nitric acid solution, and barium chloride solution in sequence and shake well, let it stand in a dark room, and measure the turbidity value with a desktop turbidity meter; (II) Turbidity test of standard products When testing chloride ions, take the chloride ion standard solution, place it in a standard turbidity bottle, add magnesium salt or calcium salt aqueous solution, ultrapure water, nitric acid solution, silver nitrate solution in sequence and shake well, let it stand in a dark room, and measure the turbidity value with a desktop turbidity meter; When testing sulfate ions, take sulfate standard solution, place it in a standard turbidity bottle, add magnesium salt or calcium salt aqueous solution, ultrapure water, nitric acid solution, barium chloride solution in sequence and shake well, let it stand in a dark room, and measure the turbidity value with a desktop turbidity meter; (III) Result determination Compare the sample bottle and the standard bottle by turbidimetry. If the turbidity of the sample tube does not exceed that of the standard bottle, it can be determined that the chloride ion in the sample is less than or equal to the concentration of the corresponding standard solution in the standard tube. Otherwise, it can be determined that the chloride ion in the sample is greater than the concentration of the corresponding standard solution in the standard bottle.

2. The method for testing the chloride ion or sulfate ion content in lithium difluorooxalatoborate according to claim 1, characterized in that: The magnesium salt is magnesium bis(fluorosulfonylimide), magnesium nitrate, magnesium trifluoromethylsulfonylimide, magnesium trifluoromethylsulfonate or magnesium perchlorate.

3. The method for testing the chloride ion or sulfate ion content in lithium difluorooxalatoborate according to claim 1, characterized in that: The calcium salt is calcium bis(fluorosulfonyl)imide, calcium nitrate, calcium trifluoromethylsulfonyl imide, calcium trifluoromethylsulfonate or calcium perchlorate.

4. The method for testing the chloride ion or sulfate ion content in lithium difluorooxalatoborate according to claim 1, characterized in that: In the first step, the molar ratio of lithium difluorooxalatoborate to magnesium salt is 1:0.5-1:

10.

5. The method for testing the chloride ion or sulfate ion content in lithium difluorooxalatoborate according to claim 1, characterized in that: In the first step, the molar ratio of lithium difluorooxalatoborate to calcium salt is 1:0.5-1:

10.

6. The method for testing the chloride ion or sulfate ion content in lithium difluorooxalatoborate according to claim 1, characterized in that: In the first step, the mixing method is: firstly put a stirring bar into the mixed system of lithium difluorooxalatoborate and magnesium salt or calcium salt aqueous solution, stir for 5-30 minutes and then ultrasonicate at 40°C-80°C for 10-60 minutes.

7. The method for testing the chloride ion or sulfate ion content in lithium difluorooxalatoborate according to claim 1, characterized in that: In the first step, filtration is performed using a 0.22-0.45 mm organic nylon filter membrane.

8. The method for testing the chloride ion or sulfate ion content in lithium difluorooxalatoborate according to claim 1, characterized in that: In the sample turbidity test steps, when testing chloride ions, the mass ratio of lithium difluorooxalate borate, ultrapure water, nitric acid, and silver nitrate is 1:(0.5-5):(0.5-5):(0.1-2); when testing sulfate ions, the mass ratio of lithium difluorooxalate borate, ultrapure water, nitric acid, and barium chloride is 1:(0.5-5):(0.5-5): (0.1～2)。 9. The method for testing the chloride ion or sulfate ion content in lithium difluorooxalatoborate according to claim 1, characterized in that: In the standard turbidity test steps, when testing chloride ions, the mass ratio of chloride ion standard solution, magnesium salt / calcium salt, ultrapure water, nitric acid, and silver nitrate is 1:(1-30):(10-30):(1-10):(1-5).

10. The method for testing the chloride ion or sulfate ion content in lithium difluorooxalatoborate according to claim 1, characterized in that: In the standard turbidity test steps, when testing sulfate ions, the mass ratio of sulfate standard solution, magnesium salt / calcium salt, ultrapure water, nitric acid, and barium chloride is 1:(1-30):(10-30):(1-10):(1-5).