Method for measuring content of villiaumite in electrolyte by using nuclear magnetic resonance technology

Abstract

According to the method for measuring the content of the villiaumite in the electrolyte by using the nuclear magnetic resonance technology, a nuclear magnetic fluorine spectrum and an ion chromatography are combined, the interfered villiaumite is qualitatively and quantitatively tested through an internal standard method, the test result is high in accuracy and good in repeatability, and RSD is smaller than 0.5%; the problems that in a traditional testing method, villiaumite is prone to being interfered, so that the measuring error is large, and even qualitative and quantitative testing cannot be achieved are solved. The method can determine the fluorine-containing salt easy to interfere, has the advantages of accurate determination result, good repeatability, less sample consumption, simple operation, rapid determination and the like, and is suitable for component analysis, quality control and other performance evaluation of electrolytes of lithium ion batteries and sodium ion batteries.

Description

Technical Field

[0001] The present application relates to the technical field of analysis of electrolytes of lithium-ion batteries and sodium-ion batteries, and in particular to a method for determining the content of fluoride salts in electrolytes using nuclear magnetic resonance technology. Background Art

[0002] Lithium-ion batteries and sodium-ion batteries have been widely studied and applied due to their high energy density and long cycle life. As a key component of lithium-ion batteries, the quality of electrolytes directly affects the performance and safety of batteries. Fluoride-containing salts and fluoride-containing salt additives have received extensive attention and application due to their excellent high and low temperature performance, thermal stability and cycle performance, and their good promotion effect in the formation of solid electrolyte interface (SEI film). However, in traditional ion chromatography tests, due to their low concentration, weak signal, and susceptibility to interference from other components in the electrolyte, the determination of their content becomes difficult. For example, in ion chromatography tests, the signal peak of lithium difluorooxalatoborate is easily interfered by lithium dioxalatoborate and fluoroethylene carbonate, and lithium difluorophosphate is easily interfered by lithium tetrafluoroborate, resulting in overlapping signal peak positions. In addition, the chemical stability of fluoride-containing salts places higher requirements on the test method. They are easily hydrolyzed in a very short time, making it difficult for ion chromatography to meet the needs of high-precision quantitative testing.

[0003] In the production and use of electrolytes, accurate determination of the content of fluorine-containing lithium salts is crucial to the performance evaluation of electrolytes. Therefore, there is an urgent need for a test method suitable for accurately determining the content of fluorine-containing lithium salts, which should have the advantages of low sample consumption, simple operation, fast determination, and accurate results. Summary of the invention

[0004] Technical problems solved: In view of the technical problems existing in the prior art, such as the interference of fluoride-containing salts in the traditional ion chromatography test method, which leads to large measurement errors and even inability to conduct qualitative and quantitative tests, a method for determining the content of fluoride-containing salts in electrolytes using nuclear magnetic resonance technology is provided. The ion chromatography detection method and quantitative 19 The fluorine-containing salts that are less likely to interfere with the ion chromatography results were used as internal standards.

[0005] A method for determining the content of fluoride salt in an electrolyte using nuclear magnetic resonance technology, the preparation method comprising the following steps:

[0006] The first step is to determine the type and content of total salt by ion chromatography: weigh 0.100-1.000g of electrolyte, add ultrapure water to 20-50g, shake and mix for 10-15s, filter through a 0.22μm filter head, and detect by ion chromatography to obtain the type and accurate content of fluoride-containing salts;

[0007] The second step is to prepare a fluorine-containing salt internal standard mother solution: using a determined fluorine-containing salt as an internal standard substance, dissolving it in a solvent to prepare a 5.00% to 25.00% (w / w) internal standard mother solution;

[0008] Step 3: Preparation of the mother solution of the fluorine-containing salt to be tested: accurately weigh 0.050-1.500 g of the fluorine-containing salt to be tested, add a solvent to dissolve and prepare a mother solution of the fluorine-containing salt to be tested, the concentration of which is 0.30%-15.00% (w / w), and mix evenly until it is completely dissolved;

[0009] Step 4, prepare a fluorine-containing salt gradient sample with an internal standard: mix the solutions obtained in step 2 and step 3 according to the gradient ratio to obtain a series of fluorine-containing lithium salt gradient samples with an internal standard, accurately pipette 0.02-0.10 mL into a 5 mm NMR tube, add 0.40-0.48 mL of a deuterated reagent, mix well, and obtain a sample solution to be tested;

[0010] Step 5, prepare the electrolyte sample to be analyzed: accurately pipette 0.02-0.10 mL of the electrolyte sample to be analyzed into a 5 mm NMR tube, add 0.40-0.48 mL of a deuterated reagent, mix well, and obtain the electrolyte sample to be analyzed;

[0011] Step 6: Test and calculate the results: The samples from step 4 and step 5 are injected into the NMR for detection. The results are processed by Mestrenova software, the internal standard peak area is determined, and the peak area A of the fluoride-containing salt peak to be tested is obtained. i , calculate the content of fluorine-containing lithium salt to be tested by the internal standard method.

[0012] Furthermore, in the second step, 2 to 10 g of the internal standard fluoride salt is accurately weighed, and carbonate is added to 10.00 to 40.00 g to prepare an internal standard mother solution with a concentration of 5.00% to 25.00% (w / w).

[0013] Furthermore, in the third step, 0.050-1.500 g of the fluorine-containing salt to be tested is accurately weighed, and carbonate is added to 5.00-15.00 g to prepare a mother solution of the fluorine-containing salt to be tested with a concentration of 0.30%-15.00% (w / w).

[0014] Furthermore, in the fourth step, 0.500 g, 1.500 g, 2.500 g, 4.000 g and 5.000 g of the fluorine-containing salt mother liquor are accurately weighed, and the solvent is added to 2.00-10.00 g respectively, and then 1.00-5.00 g of the internal standard mother liquor is accurately weighed and added to a 20 mL centrifuge tube, and mixed evenly to obtain a fluorine-containing salt gradient sample with an internal standard.

[0015] Furthermore, in the fourth and fifth steps, 0.02-0.10 mL of the standard substance and sample to be tested are accurately pipetted, and 0.40-0.48 mL of deuterated reagent is added to dilute them respectively, and the mixture is shaken to obtain a nuclear magnetic resonance test sample.

[0016] Furthermore, the fluorine-containing salt is one or more of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium bisoxalate borate, lithium difluorooxalate borate, lithium bistrifluoromethanesulfonyl imide, lithium bisfluorosulfonyl imide, lithium difluorophosphate, sodium hexafluorophosphate, sodium tetrafluoroborate, sodium bisoxalate borate, sodium difluorooxalate borate, sodium bistrifluoromethanesulfonyl imide, sodium bisfluorosulfonyl imide, and sodium difluorophosphate; the solvent is one or more of ethyl methyl carbonate, dimethyl carbonate, diethyl carbonate, propylene carbonate, ethylene carbonate, methyl trifluoroethyl carbonate, ethyl acetate, ethyl propionate, propyl acetate, ethylene glycol dimethyl ether, and ethylene glycol dipropionitrile ether; and the deuterated reagent is one or more of deuterated acetonitrile, deuterated acetone, deuterated dimethyl sulfoxide, deuterated methanol, and deuterated chloroform.

[0017] Furthermore, the test conditions of the nuclear magnetic resonance apparatus in the sixth step include sequence zg, scanning times 8 to 128 times, and D1=5.

[0018] Furthermore, in the sixth step, phase correction, baseline correction and chemical shift correction are manually performed, and the characteristic peak of the internal standard is selected to set the area to 1000-1500, and the fluorine peak of the fluorine-containing salt to be tested at the characteristic shift is integrated.

[0019] Furthermore, draw —Linear equation for concentration, based on electrolyte Get electrolyte A i , combined with linear equations, the content of fluoride salts in the electrolyte can be accurately calculated.

[0020] Principle explanation:

[0021] 19 F nuclear magnetic resonance (NMR) spectroscopy is known for its 100% natural abundance and high gyromagnetic ratio, which give it high sensitivity, high specificity and a wide chemical shift range. 19 F-NMR can clearly and accurately detect the fluorine-containing components in the electrolyte; 19 The F-NMR technique is used to determine the fluoride salt content in the electrolyte. The integral area of ​​the NMR peak of a specific proton in quantitative analysis is proportional to its mass concentration. By preparing a series of standards containing known concentrations of the lithium salt to be tested and the internal standard substance, and performing NMR determination under the same test conditions, it can be found that there is a linear relationship between the integral area ratio of the signal peak and their content ratio. By establishing an equation for this linear relationship, the content of the fluoride lithium salt to be tested in the electrolyte sample can be accurately calculated.

[0022] Beneficial effects:

[0023] 1. High accuracy: The use of nuclear magnetic quantitative method and internal standard method reduces the interference to the sample and improves the accuracy of the measurement;

[0024] 2. High efficiency: Compared with the existing ion chromatography method, it simplifies the sample pretreatment operation steps, reduces sample loss and possible contamination, has a fast determination speed, short analysis time, and high accuracy and repeatability of the test results;

[0025] 3. High repeatability: Optimized experimental conditions and data processing methods ensure the repeatability of the measurement results;

[0026] 4. High applicability: suitable for the analysis of different types of lithium-ion battery electrolytes;

[0027] 5. Industrial application: The present invention is particularly suitable for the quality control and performance evaluation of electrolytes in the manufacturing field of lithium-ion batteries and sodium-ion batteries, and can also be used for the quality control of electrolytes in the battery production process;

[0028] 6. Compared with the traditional ion chromatography detection method, the method used in the present invention has the characteristics of rapid and high-precision lithium salt content determination. Ion chromatography can only determine the composition of lithium salts by comparing with an established database, but it is difficult to accurately determine the quality and quantity of new lithium salts outside the database or components with completely overlapping ion peaks (such as lithium difluorooxalatoborate and fluoroethylene carbonate); the use of NMR technology can quickly and accurately determine the quality and quantity of various fluorine-containing lithium salts in the electrolyte through chemical shift, while avoiding the interference of other fluorine-containing components or lithium salt hydrolysis on the results; the present invention Peak area ratio 19 The relative standard deviation of the repeatability of the F-NMR result is 0.34%, which can accurately determine the content of 0.02% (w / w) lithium difluorooxalatoborate in the electrolyte. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 This application is a lithium-ion electrolyte test containing only lithium hexafluorophosphate and lithium difluorooxalate borate 19 F-NMR spectrum;

[0030] Figure 2 This application is for testing a lithium-ion electrolyte 19 F-NMR spectrum;

[0031] Figure 3 This application contains different concentrations of lithium difluorooxalate borate solution tested with internal standard 19 F-NMR spectrum;

[0032] Figure 4 It is a standard curve graph of linearity and range of lithium difluorooxalate borate of the present application. DETAILED DESCRIPTION

[0033] The embodiments of the present invention are described below with reference to the accompanying drawings.

[0034] Example 1

[0035] A method for determining the content of fluoride salt in an electrolyte using nuclear magnetic resonance technology, wherein the detection of lithium difluorooxalate borate content in a simple electrolyte comprises the following steps:

[0036] The first step is to determine the type and content of total salts by ion chromatography: weigh 0.150g of electrolyte, add ultrapure water to 30.000g, shake and mix for 10-15s, filter through a 0.22μm filter head, and detect by ion chromatography to obtain the type and accurate content of fluoride-containing salts;

[0037] The second step is to prepare the internal standard mother solution of the fluorine-containing salt: take the determined fluorine-containing salt lithium hexafluorophosphate as the internal standard, accurately weigh 4.000 g, add solvent propylene carbonate to 40.000 g and dissolve to prepare the internal standard mother solution;

[0038] Step 3: Preparation of the mother solution of the fluorine-containing salt to be tested: accurately weigh 0.200 g of the fluorine-containing salt to be tested, lithium difluorooxalate borate, add solvent propylene carbonate to 10.000 g, mix evenly until completely dissolved to prepare a lithium difluorooxalate borate mother solution sample with a concentration of 2.00% (w / w);

[0039] Step 4, prepare a fluorine-containing salt gradient sample with an internal standard: add propylene carbonate to the lithium difluorooxalatoborate mother solution in the third step to make it 5.000 g, accurately weigh 5.000 g of the internal standard lithium hexafluorophosphate mother solution, mix well in a 20 mL centrifuge tube, accurately transfer 0.04 mL to a 5 mm NMR tube, add 0.46 mL of deuterated acetone, mix well, and obtain a sample solution to be tested;

[0040] Step 5: Prepare the electrolyte sample to be analyzed: accurately pipette 0.02 mL of the electrolyte sample to be analyzed into a 5 mm NMR tube, add 0.48 mL of deuterated acetone, mix well, and obtain the electrolyte sample to be analyzed; the above weighing records should be accurate to 0.001 g;

[0041] Step 6: Test and calculate the results: The samples from step 4 and step 5 were injected into the NMR for detection. The results were processed by Mestrenova software. Phase correction, baseline correction and chemical shift correction were performed manually in sequence. The internal standard peak area was determined to obtain the peak area A of lithium difluorooxalate borate. ODFB , get the peak area of ​​lithium difluorooxalate borate, and plot —Linear equation for concentration, based on electrolyte Get A in the electrolyte ODFB, combined with the linear equation, the exact content of lithium difluorooxalatoborate in the electrolyte is accurately calculated.

[0042] Specifically, the purity of the internal standard lithium hexafluorophosphate and lithium difluorooxalatoborate is 99.95%.

[0043] Specifically, the test conditions of the nuclear magnetic quantitative analysis method of Example 1 of the present invention are: sequence zg, scanning number 16 times, D1 = 5. The fluorine peak area at -71.75 ppm of lithium hexafluorophosphate is determined to be 1000, and the fluorine peak at -153.9 ppm of lithium difluorooxalatoborate is integrated.

[0044] Example 2

[0045] A method for determining the content of fluorine-containing salts in an electrolyte using nuclear magnetic resonance technology, and a method for detecting the content of lithium difluorooxalate borate in a complex electrolyte: Considering that new lithium-ion electrolytes may contain a variety of fluorine-containing additives, and these components may interfere with the spectrum, a complex electrolyte sample containing possible interfering substances (such as lithium difluorophosphate, lithium bis(fluorosulfonyl)imide, fluoroethylene carbonate, etc.) is prepared, and deuterated acetone is added according to the method of Example 1 to perform NMR measurement. Special attention is paid to distinguishing and excluding the signals of interfering substances. The interference is corrected using the internal standard method, and the content of lithium difluorooxalate borate is accurately determined by the correction factor based on the known content of lithium hexafluorophosphate. The analysis results are as follows: Figure 2 and Figure 3 As shown, the blank solution and electrolytes containing other fluorine-containing additives do not interfere with the components to be tested.

[0046] Example 3

[0047] A method for determining the content of fluoride salts in electrolytes using nuclear magnetic resonance technology, linearity and range:

[0048] Weigh 0.500g, 1.5000g, 2.500g, 4.000g and 5.000g (accurate to 0.001g) of the lithium difluorooxalate borate mother liquor of Example 1 respectively, add propylene carbonate to 5.000g respectively, then accurately weigh and add 5.000g of the internal standard lithium hexafluorophosphate mother liquor, mix evenly in a 20mL centrifuge tube, and obtain a lithium difluorooxalate borate gradient sample with an internal standard. Accurately transfer 100uL of the gradient sample to a 5mm nuclear magnetic tube, accurately add 400uL of deuterated acetone, prepare lithium difluorooxalate borate standard solutions with concentrations ranging from 0.02% to 0.2% (w / w), and place the solutions of different concentrations in the determination steps of Example 1 from low to high, with concentration as the horizontal axis and peak area ratio as the vertical axis. The concentrations used and the corresponding peak area ratios are listed in Table 1, and the standard curve is drawn as shown in Table 1. Figure 4As shown, the obtained linear equation is y=27.284x+0.0343, and the correlation coefficient r=0.9976>0.995, which is used for quantitative analysis of the content of lithium difluorooxalate borate in electrolyte samples. Lithium difluorooxalate borate has a good linear relationship in the concentration range of 0.020% to 0.230% (w / w).

[0049] Table 1 Lithium difluorooxalate borate concentration and peak area results

[0050]

[0051] Example 4

[0052] A method for determining the content of fluoride salts in electrolytes using nuclear magnetic resonance technology, system accuracy experiment:

[0053] A 0.10% (w / w) solution of lithium difluorooxalate borate containing an internal standard was prepared with deuterated acetone to a concentration of 0.02% (w / w) according to the method in Example 3, and the sample was injected 6 times continuously. The results are shown in Table 2. The peak areas of lithium difluorooxalate borate and internal standard lithium hexafluorophosphate The relative standard deviation (RSD) of repeatability is 0.34%, so the system accuracy of the present invention is good.

[0054] Table 2 System accuracy experimental results

[0055]

[0056] Example 5

[0057] A method for determining the content of fluoride salts in electrolytes using nuclear magnetic resonance technology, repeatability experiment:

[0058] The repeatability of the method was investigated using the recovery data of the spiked solution of the test sample at the 100% level using an electrolyte that did not contain lithium difluorooxalateborate.

[0059] The mean recovery rate of the 6 test sample spiked solutions should be within the range of 90% to 108%, and the recovery rate RSD should be no more than 3%. The results are shown in Table 3. The recovery rates of the 6 solutions are between 100.0% and 105.0%, and the recovery rate RSD is 0.46%, which meets the requirements. Therefore, this method has good repeatability.

[0060] Table 3 Repeatability test results

[0061]

[0062] Example 6

[0063] A method for determining the content of fluoride salts in electrolytes using nuclear magnetic resonance technology, with quantitative limits and detection limits:

[0064] Preparation of quantitative limit solution: Take lithium difluorooxalate borate internal standard solution, prepare it with deuterated acetone to 0.02% (w / w), inject it 6 times continuously, and examine the signal-to-noise ratio of the fluorine atom peak of lithium difluorooxalate borate and the RSD of the peak area of ​​6 injections. The signal-to-noise ratio of the fluorine atom peak of lithium difluorooxalate borate should be no less than 10, and the RSD of the peak area of ​​6 consecutive injections should be no more than 5%.

[0065] The results are shown in Table 4. The signal-to-noise ratio of the fluorine atom peak in the quantitative limit solution is greater than 10, and the peak area RSD is 0.49%, which meets the requirements. Therefore, the concentration of the quantitative limit solution of the present invention is 0.02% (w / w).

[0066] Table 4 Quantitation limit results

[0067] Sample name Peak area S / N Quantitative limit solution 1 54.81 27.4 Quantitative limit solution 2 54.89 26.0 Quantitative limit solution 3 55.29 28.1 Quantitative limit solution 4 54.37 25.7 Quantitative limit solution 5 54.72 26.3 Quantitative limit solution 6 54.78 29.1 RSD 0.49％ -

[0068] Preparation of detection limit solution: Take lithium difluorooxalate borate with internal standard solution, configure it to 0.01% (w / w) with deuterated acetone, inject it continuously for 3 times, and examine the signal-to-noise ratio of the fluorine atom peak of lithium difluorooxalate borate. After 3 consecutive injections, the signal-to-noise ratio of the detection limit lithium difluorooxalate borate fluorine atom peak should be greater than 3. The results are shown in Table 5. The signal-to-noise ratio of the detection limit solution is greater than 3, which meets the requirements. Therefore, the concentration of the detection limit solution is 0.01% (w / w).

[0069] Table 5 Detection limit results

[0070] Sample name Peak area S / N Detection limit solution 1 32.7 14.3 Detection limit solution 2 34.6 15.7 Detection limit solution 3 33.2 12.8

[0071] The embodiments of the present invention are described in detail above, but the contents described are only preferred embodiments of the present invention and cannot be considered to limit the scope of implementation of the present invention. All equivalent changes and improvements made within the scope of the present invention should still fall within the scope of the patent coverage of the present invention.

Claims

1. A method for determining the content of fluoride salt in an electrolyte using nuclear magnetic resonance technology, characterized in that: The method The following steps are involved: The first step is to determine the type and content of total salt by ion chromatography: weigh 0.100-1.000g of electrolyte, add ultrapure water to 20-50g, shake and mix for 10-15s, filter through a 0.22μm filter head, and detect by ion chromatography to obtain the type and accurate content of fluoride-containing salts; The second step is to prepare a fluorine-containing salt internal standard mother solution: using a determined fluorine-containing salt as an internal standard substance, dissolving it in a solvent to prepare a 5.00% to 25.00% (w / w) internal standard mother solution; Step 3: Preparation of the mother solution of the fluorine-containing salt to be tested: accurately weigh 0.050-1.500 g of the fluorine-containing salt to be tested, add a solvent to dissolve and prepare a mother solution of the fluorine-containing salt to be tested, the concentration of which is 0.30%-15.00% (w / w), and mix evenly until it is completely dissolved; Step 4, prepare a fluorine-containing salt gradient sample with an internal standard: mix the solutions obtained in step 2 and step 3 according to the gradient ratio to obtain a series of fluorine-containing lithium salt gradient samples with an internal standard, accurately pipette 0.02-0.10 mL into a 5 mm NMR tube, add 0.40-0.48 mL of a deuterated reagent, mix well, and obtain a sample solution to be tested; Step 5, prepare the electrolyte sample to be analyzed: accurately pipette 0.02-0.10 mL of the electrolyte sample to be analyzed into a 5 mm NMR tube, add 0.40-0.48 mL of a deuterated reagent, mix well, and obtain the electrolyte sample to be analyzed; Step 6: Test and calculate the results: The samples from step 4 and step 5 are injected into the NMR for detection. The results are processed by Mestrenova software, and the internal standard peak area is determined to obtain the peak area A of the fluoride-containing salt peak to be tested. i , calculate the content of fluorine-containing lithium salt to be tested by the internal standard method.

2. The method for determining the content of fluorine-containing salt in electrolyte using nuclear magnetic resonance technology according to claim 1, characterized in that: In the second step, 2-10 g of the internal standard fluoride salt is accurately weighed, and carbonate is added to make the amount 10.00-40.00 g to prepare an internal standard mother solution with a concentration of 5.00%-25.00% (w / w).

3. The method for determining the content of fluorine-containing salt in electrolyte using nuclear magnetic resonance technology according to claim 1, characterized in that: In the third step, 0.050-1.500 g of the fluorine-containing salt to be tested is accurately weighed, and carbonate is added to 5.00-15.00 g to prepare a mother solution of the fluorine-containing salt to be tested with a concentration of 0.30%-15.00% (w / w).

4. The method for determining the content of fluorine-containing salt in electrolyte using nuclear magnetic resonance technology according to claim 1, characterized in that: In the fourth step, 0.500 g, 1.500 g, 2.500 g, 4.000 g and 5.000 g of the fluorine-containing salt mother liquor are accurately weighed, and the solvent is added to 2.00-10.00 g respectively. Then, 1.00-5.00 g of the internal standard mother liquor is accurately weighed and added to a 20 mL centrifuge tube, and mixed evenly to obtain a fluorine-containing salt gradient sample with an internal standard.

5. The method for determining the content of fluorine-containing salt in electrolyte using nuclear magnetic resonance technology according to claim 1, characterized in that: In the fourth and fifth steps, 0.02-0.10 mL of the standard substance and sample to be tested are accurately pipetted, and 0.40-0.48 mL of deuterated reagent is added to dilute them respectively, and the mixture is shaken to obtain a nuclear magnetic resonance test sample.

6. The method for determining the content of fluoride salt in electrolyte using nuclear magnetic resonance technology according to claim 1, characterized in that: The fluorine-containing salt is one or more of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium bisoxalate borate, lithium difluorooxalate borate, lithium bistrifluoromethanesulfonyl imide, lithium bisfluorosulfonyl imide, lithium difluorophosphate, sodium hexafluorophosphate, sodium tetrafluoroborate, sodium bisoxalate borate, sodium difluorooxalate borate, sodium bistrifluoromethanesulfonyl imide, sodium bisfluorosulfonyl imide, and sodium difluorophosphate; the solvent is one or more of ethyl methyl carbonate, dimethyl carbonate, diethyl carbonate, propylene carbonate, ethylene carbonate, methyl trifluoroethyl carbonate, ethyl acetate, ethyl propionate, propyl acetate, ethylene glycol dimethyl ether, and ethylene glycol dipropionitrile ether; the deuterated reagent is one or more of deuterated acetonitrile, deuterated acetone, deuterated dimethyl sulfoxide, deuterated methanol, and deuterated chloroform.

7. The method for determining the content of fluorine-containing salt in electrolyte using nuclear magnetic resonance technology according to claim 1, characterized in that: The test conditions of the nuclear magnetic resonance apparatus in the sixth step include sequence zg, scanning times 8 to 128 times, and D1=5.

8. The method for determining the content of fluoride salt in electrolyte using nuclear magnetic resonance technology according to claim 1, characterized in that: In the sixth step, phase correction, baseline correction and chemical shift correction are manually performed, and the characteristic peak of the internal standard is selected to set the area to 1000-1500, and the fluorine peak of the fluorine-containing salt to be tested at the characteristic shift is integrated.

9. The method for determining the content of fluoride salt in electrolyte using nuclear magnetic resonance technology according to claim 8, characterized in that: by Get electrolyte A i , combined with linear equations, the content of fluoride salts in the electrolyte can be accurately calculated.

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