Determination of lithium difluorooxalate borate and lithium bisoxalate borate in lithium battery electrolyte

Abstract

The application discloses a kind of lithium battery electrolyte lithium difluoroborate oxalate and lithium difluoroborate oxalate determination, comprising the following steps: preparation BF4 ‑ Standard solution mother liquor;Preparation BF4 ‑ Standard solution;Preparation lithium battery electrolyte BF4 ‑ To be measured solution;Preparation C2O4 2‑ Standard solution mother liquor;Preparation C2O4 2‑ Standard solution;Preparation lithium battery electrolyte C2O4 2‑ To be measured solution;Instrument analysis: using anion chromatograph, regenerative liquid is sulfuric acid aqueous solution, eluent uses Na2CO3, NaHCO3 acetonitrile water system;Respectively to BF4 ‑ Standard solution, C2O4 2‑ Standard solution, lithium battery electrolyte BF4 ‑ To be measured solution, lithium battery electrolyte C2O4 2‑ To be measured solution carries out anion chromatography analysis, records peak area;Calculate the content of lithium difluoroborate oxalate and lithium difluoroborate oxalate.The method is simple, convenient, accurate and stable, thereby providing reliable means for accurate determination of the content of each component of lithium battery electrolyte, and further ensuring the quality of lithium battery electrolyte product.

Description

Technical Field

[0001] This invention relates to the determination of the components of lithium battery electrolytes, specifically to the determination of lithium difluorooxalate borate and lithium dioxalate borate. Background Technology

[0002] Lithium difluorooxalate borate (LiODFB) is sensitive to water and can decompose in water to release oxalate and borate ions. Hydrolysis of lithium difluorooxalate borate (LiBOB) also produces oxalate and borate compounds.

[0003] Boric acids do not produce peaks on anion exchange chromatography. When either of these two substances is present alone in the lithium battery electrolyte, their hydrolysis ion peak (C2O4) can be observed. 2- The accurate content was determined after quantitative analysis. However, when both substances are present in the electrolyte, their stable hydrolysis ion peaks are both C2O4. 2- Therefore, it is impossible to accurately determine the content of the two components separately using the ion peak at this position. However, each component in the lithium battery electrolyte formulation has certain concentration requirements. The concentration of each component in the lithium battery electrolyte formulation is an important reference indicator for judging whether the lithium battery electrolyte meets the application requirements. Therefore, it is necessary to accurately quantify lithium difluorooxalate borate (LiODFB) and lithium dioxalate borate (LiBOB) in the lithium battery electrolyte separately. Summary of the Invention

[0004] The purpose of this invention is to provide a method for determining lithium difluorooxalate borate and lithium dioxalate borate in lithium battery electrolytes. This method can simultaneously determine the content of lithium difluorooxalate borate and lithium dioxalate borate in lithium battery electrolytes, and the determination method has high accuracy.

[0005] To solve the above-mentioned technical problems, the technical solution adopted by the present invention includes: the determination of lithium difluorooxalate borate and lithium dioxalate borate in lithium battery electrolyte, comprising the following steps:

[0006] Preparation of BF4 - Standard solution stock solution: Weigh the raw material LiBF4, dilute it with pure water to form BF4. - Standard solution stock solution.

[0007] Preparation of BF4 - Standard solution, weigh out BF4 - The standard solution stock solution was further diluted with pure water to form BF4. - Standard solution.

[0008] Preparation of lithium battery electrolyte BF4 - Test solution: Take the lithium battery electrolyte to be tested, dilute it with water, add an excess of hydrofluoric acid aqueous solution, heat it at 60℃~80℃ for reaction, cool it after completion, add water to further dilute it, shake it well and test it.

[0009] Preparation of C2O4 2- Standard solution stock solution: C2O4 is prepared by diluting the primary standard reagent Na2C2O4 with pure water. 2- Standard solution stock solution.

[0010] Preparation of C2O4 2- Standard solution: Take C2O4 2- The standard solution stock solution is further diluted with pure water to form C2O4. 2- Standard solution.

[0011] Preparation of lithium battery electrolyte C2O4 2- Test solution: Weigh the lithium battery electrolyte to be tested; dilute with pure water to form lithium battery electrolyte C2O4. 2- The solution to be tested.

[0012] Instrumental analysis: Anion chromatography was used. The regenerator was an aqueous sulfuric acid solution, and the eluent was an acetonitrile-water system containing Na₂CO₃ and NaHCO₃. BF₄ was analyzed separately. - Standard solution, C2O4 2- Standard solution, lithium battery electrolyte BF4 - C2O4 in the test solution and lithium battery electrolyte 2- The test solution was subjected to anion chromatography analysis, and the peak area was recorded.

[0013] Calculate the contents of lithium difluorooxalate borate and lithium dioxalate borate by solving equations one and two simultaneously.

[0014]

[0015]

[0016] In the formula, X represents the content of lithium difluorooxalate borate in the electrolyte of the lithium battery to be tested, in ppm; Y represents the content of lithium dioxalate borate in the electrolyte of the lithium battery to be tested, in ppm; A 样B BF4 in lithium battery electrolyte was determined by anion chromatography. - BF4 in the test solution - Peak area; A 标B BF4 was determined by anion chromatography. - BF4 in standard solutions - Peak area; C 标B BF4 - BF4 in standard solution - Concentration, in ppm; multiple B To prepare lithium battery electrolyte BF4 - The dilution factor of the test solution; A 样C Anion chromatography was used to determine C2O4 in lithium battery electrolyte.2- C2O4 in the test solution 2- Peak area; A 标C C2O4 was determined by anion chromatography. 2- C2O4 in standard solution 2- Peak area; C 标C C2O4 2- C2O4 in standard solution 2- The concentration, in ppm;

[0017] multiple C To prepare lithium battery electrolyte C2O4 2- The dilution factor of the test solution; M1 is the molecular weight of lithium difluorooxalate borate; M2 is the molecular weight of lithium difluorooxalate borate; M3 is C2O4. 2- Molecular weight; M4 is BF4 - The molecular weight; 10000 is a constant.

[0018] Furthermore, the determination of lithium difluorooxalate borate and lithium dioxalate borate in the aforementioned lithium battery electrolyte was performed using an ICS-2100 ion chromatograph with a Shodex SI-904E anion chromatography column. The concentration of the sulfuric acid solution was 0.07 mol / L to 0.09 mol / L. The concentrations of Na2CO3 and NaHCO3 in the eluent were both 2.4 mmol / L, and the volume ratio of acetonitrile to water was 1:3.

[0019] Furthermore, the determination of lithium difluorooxalateborate and lithium dioxalateborate in the aforementioned lithium battery electrolyte, wherein the preparation of C2O4 2- When preparing the standard solution stock solution, the primary standard reagent Na₂C₂O₄ requires pre-drying treatment. The pre-drying treatment steps include: placing the primary standard reagent Na₂C₂O₄ in a porcelain crucible and drying it at a constant temperature of 100±2℃ in an oven for 2 hours, then cooling it in a desiccator for later use. The purpose of drying is to remove the moisture adsorbed by sodium oxalate during storage and to increase the C₂O₄ content. 2- The accuracy of standard solution stock solution preparation is improved to enhance the performance of C2O4. 2- The accuracy of standard solution preparation improves the detection accuracy of anion chromatography.

[0020] Furthermore, in the aforementioned determination of lithium difluorooxalate borate and lithium dioxalate borate in the lithium battery electrolyte, the purity of the raw material LiBF4 is greater than or equal to 99.9%. Using high-purity raw materials can effectively avoid interference from impurities, thereby improving the accuracy of the determination.

[0021] Furthermore, the determination of lithium difluorooxalate borate and lithium dioxalate borate in the aforementioned lithium battery electrolyte, wherein the preparation of the lithium battery electrolyte BF4 -When preparing the test solution, an excess of hydrofluoric acid aqueous solution is added, followed by heating in an oven at 80°C. The excess hydrofluoric acid ensures complete conversion of all boron elements, and the 80°C temperature further ensures the conversion of boron elements and accelerates the conversion rate.

[0022] Furthermore, in the determination of lithium difluorooxalate borate and lithium dioxalate borate in the aforementioned lithium battery electrolyte, the mass concentration of the hydrofluoric acid aqueous solution is 30%.

[0023] Furthermore, the determination of lithium difluorooxalate borate and lithium dioxalate borate in the aforementioned lithium battery electrolyte, wherein the prepared BF4 - The concentration of the standard solution stock solution is approximately 5000 ppm, BF4 - The concentration of the standard solution was (25±2) ppm; BF4 was used to prepare the lithium battery electrolyte. - The dilution factor for the test solution is 50 to 500 times, and the specific dilution factor is calculated based on the theoretical content of element B in the sample. - To determine the theoretical content of BF4, select an appropriate dilution factor. The dilution principle is to determine the concentration of BF4 in the diluted sample solution. - concentration and BF4 - The standard solution is similar; C2O4 2- The standard solution stock solution concentration is approximately 5000 ppm, C2O4 2- The standard solution concentration was (25±2) ppm, and the C2O4 electrolyte for lithium batteries was prepared. 2- The dilution factor for the test solution is 50 to 500 times, and the specific dilution factor depends on the C2O4 content in the sample. 2- Choose an appropriate dilution factor based on the theoretical content. The dilution principle is that the C2O4 content in the diluted sample solution should be... 2- The concentration of C2O4 2- The concentrations of the standard solutions and the dilution factors of the test solutions are similar. Setting these concentrations facilitates measurement and calculation, and also facilitates the determination of anion peaks. Furthermore, it prevents high-salt and high-organic components in the test sample solution from damaging the anion exchange chromatography column, thus extending the column's lifespan.

[0024] Furthermore, in the determination of lithium difluorooxalate borate and lithium dioxalate borate in the aforementioned lithium battery electrolyte, the Na2CO3 and NaHCO3 used in the eluent were both of the primary standard grade, and the acetonitrile was of analytical grade; the pure water used in all solution preparation and dilution processes was distilled water that met the GB-6682 Grade III water standard.

[0025] The advantages of this invention are: pretreatment with hydrofluoric acid followed by detection of BF4 using an anion chromatography instrument. - and C2O4 2-The total content is determined by using a linear equation in two variables to accurately calculate the content of LiODFB and LiBOB components. This method is simple, convenient, and accurate, providing a reliable means for determining the components in lithium battery electrolytes, thus greatly ensuring the quality of lithium battery electrolyte products. Attached Figure Description

[0026] Figure 1 The image shows the anion chromatogram of boric acid aqueous solution from Experiment 1.

[0027] Figure 2 The image shows the anion chromatogram of the boric acid aqueous solution after the addition of hydrofluoric acid in Experiment 1.

[0028] Figure 3 The anion chromatogram is obtained by anion chromatography analysis immediately after dilution of LiODFB in pure water in Experiment 2.

[0029] Figure 4 The anion chromatogram is obtained by anion chromatography analysis of LiODFB after it has been diluted with pure water and left for a period of time in Experiment 2.

[0030] Figure 5 The anion chromatogram is obtained from the anion chromatography analysis of LiBOB immediately after dilution with pure water in Experiment 2.

[0031] Figure 6 The anion chromatogram obtained by anion chromatography analysis of LiBOB after dilution with pure water and addition of hydrofluoric acid in Experiment 2. Detailed Implementation

[0032] The determination of lithium difluorooxalate borate and lithium dioxalate borate in the lithium battery electrolyte of the present invention will be further described in detail below.

[0033] The anion chromatograph mentioned below is an ICS-2100 ion chromatograph with a Shodex SI-90 4E column. The instrument regenerator is a sulfuric acid solution with a concentration of 0.07 mol / L to 0.09 mol / L. The eluent is an acetonitrile-water system of Na2CO3 and NaHCO3, where the concentrations of Na2CO3 and NaHCO3 are both 2.4 mmol / L, and the volume ratio of acetonitrile to water is 1:3.

[0034] The Na2CO3 and NaHCO3 used in the rinsing solution were both of the primary standard grade, and the acetonitrile was of analytical grade. All pure water used in the preparation and dilution of the solutions was distilled water that met the GB-6682 Class III water standard.

[0035] Preparation of BF4 - When preparing the standard solution mother liquor, the purity of the raw material LiBF4 should be greater than or equal to 99.9%.

[0036] Preparation of C2O4 2- When preparing the standard solution stock solution, Na₂C₂O₄ is used as a reference reagent. Preparation of C₂O₄ 2- When preparing the standard solution stock solution, the Na2C2O4 primary standard reagent needs to be pretreated by drying. The primary standard reagent Na2C2O4 is placed in a porcelain crucible and dried at a constant temperature of 105±2℃ in an oven for 2 hours, and then placed in a desiccator to cool for later use.

[0037] Experiment 1: To verify the reaction of boric acid and hydrofluoric acid: H2BO3 + 4HF = HBF4 + 3H2O.

[0038] First, anion chromatography analysis was performed on a 500 ppm boric acid aqueous solution. The anion chromatogram is shown below. Figure 1 As shown. Figure 1 The results show that no significant ion peaks appeared in the 500ppm boric acid aqueous solution, and the small peak that appeared at 4 minutes should be the impurity ion peak in the boric acid.

[0039] Next, excess hydrofluoric acid was added to the 500 ppm boric acid aqueous solution, followed by anion chromatography analysis. The anion chromatogram is shown below. Figure 2 As shown. Figure 2 Display: In BF4 - A very high ion peak is generated at the location.

[0040] Experiment 2: Experimental verification was carried out on the hydrolysis products of lithium difluorooxalate borate and lithium dioxalate borate, respectively.

[0041] First, take lithium difluorooxalate borate, dilute it with pure water, and analyze it immediately. The anion chromatogram is as follows. Figure 3 As shown. After standing for 2 hours, analyze again; the anion chromatogram is shown below. Figure 4 As shown. Figure 3 The results show that the anions of the LiODFB hydrolysis products are fluoride, borate, and oxalate ions. Figure 4 The diagram shows that the fluorine in the hydrofluoric acid produced by the self-hydrolysis of LiODFB combines with boron to form BF4. - ion.

[0042] In addition, lithium dioxarate borate was diluted with pure water and analyzed immediately. The anion chromatogram is shown below. Figure 5 As shown, Figure 5 The data shows only an oxalate ion peak. An excess of 30% hydrofluoric acid aqueous solution was added to the above lithium dioxalate-borate aqueous solution. After allowing the reaction to proceed for one hour, the solution was then subjected to anion chromatography analysis. The ion chromatogram is shown below. Figure 6 As shown. Figure 6 The data shows the presence of fluoride ion peaks and BF4. - The ion peak. Figure 6The fluoride ion peak is produced by the addition of hydrofluoric acid, BF4 - It is produced by the combination of boron and fluorine in LiBOB.

[0043] The above experiment demonstrates that the boron (B) element in LiODFB and LiBOB combines with the fluorine (fluorine) element in hydrofluoric acid to produce BF4. - .

[0044] Experiment 3: Reacting with hydrofluoric acid to produce BF4 - The accuracy was verified through experiments.

[0045] Three types of lithium battery electrolytes were prepared for testing: electrolyte #1, electrolyte #2, and electrolyte #3. Electrolyte #1 contained LiODFB but not LiBOB, with a LiODFB mass percentage of 0.302%. Electrolyte #2 contained LiBOB but not LiODFB, with a LiBOB mass percentage of 0.116%. Electrolyte #3 contained both LiODFB and LiBOB, with a LiODFB mass percentage of 0.293% and a LiBOB mass percentage of 0.112%.

[0046] BF4 - Preparation of standard solution stock solution: Weigh 0.5038 g of LiBF4 and dilute with pure water to a concentration equal to BF4. - The concentration was 4664 ppm. Preparation of BF4-standard solution: Weigh 0.5023 g of the BF4-standard solution stock solution and dilute it with pure water to 95.7801 g. At this point, the BF4 content... - The content was 24.46 ppm.

[0047] C2O4 2- Preparation of standard solution stock solution: Weigh 0.5231 g of Na₂C₂O₄ and dilute with pure water to C₂O₄. 2- An aqueous solution with a concentration of 4664 ppm. (C2O4) 2- Preparation of standard solution: Weigh 0.5023 g of C2O4 2- The standard solution stock solution was diluted with pure water to 95.7801 g. At this point, C2O4... 2- The content was 24.46 ppm.

[0048] The pretreatment steps for samples 1# and 2# of the lithium battery electrolyte to be tested are the same, as follows: Take approximately 1g of the lithium battery electrolyte to be tested, add approximately 10g of water, then add 0.3g of a 30% hydrofluoric acid aqueous solution. Heat in an oven at 80℃ for 2 hours, then remove and add water to bring the total volume to approximately 100g. Shake well before testing. The purpose of adding the hydrofluoric acid aqueous solution is to completely convert the boron element in LiODFB and LiBOB into BF4. -This allows for the conversion of LiODFB and LiBOB contents based on the formula weight. The purpose of controlling the reaction temperature at 80℃ is to ensure rapid boron conversion. This was applied to the lithium battery electrolyte samples #1 and #2, as well as BF4. - The standard solutions were analyzed by anion chromatography. Specific data are shown in Table 1.

[0049] Table 1:

[0050]

[0051] To verify the data in Table 1: Take approximately 1g of the No. 1 and No. 2 lithium battery electrolytes to be tested, respectively, and dilute them directly with pure water by about 100 times. After shaking well, perform anion chromatography detection, using C2O4 as the ion exchange medium. 2- The peak values ​​at the test locations were used to correct the percentage content of LiODFB and LiBOB in the electrolytes of lithium batteries #1 and #2. Specific data are shown in Table 2.

[0052] Table 2:

[0053]

[0054] A comparison of the data in Table 1 with the data in Table 2, and with the theoretical data, shows that: after adding excess HF acid to the lithium battery electrolyte, the boron element in LiODFB and LiBOB in the lithium battery electrolyte will be completely converted into BF4. - Therefore, by adding excess HF acid to the lithium battery electrolyte and then measuring the generated BF4... - A method for quantifying LiODFB and LiBOB is feasible.

[0055] Experiment 4: Analyze the stability of the measured values.

[0056] Five samples of lithium battery electrolytes (No. 1 and No. 2) were taken from each sample and processed using the same steps as in Experiment 3. After processing, they were analyzed by anion chromatography. The results are shown in Tables 3 and 4.

[0057] Table 3

[0058]

[0059] Table 4

[0060]

[0061] From the data in Tables 3 and 4, we can conclude that the data have good parallelism, meaning that the generated BF4... - The method for quantifying LiODFB and LiBOB has good stability.

[0062] Experiment 5: Measurement of the electrolyte of lithium battery #3 to be tested.

[0063] Specific steps: Preparation of lithium battery electrolyte BF4 - Test solution: Take approximately 1g of the No. 3 lithium battery electrolyte to be tested, add approximately 10g of water, then add 0.3g of a 30% hydrofluoric acid aqueous solution. Heat in an 80℃ oven for 2 hours, then remove and add water to approximately 100g, shake well, and then test. After the pretreatment of the lithium battery electrolyte sample, perform anion chromatography analysis to detect BF4. - Preparation of lithium battery electrolyte C2O4 2- Test solution: Weigh approximately 1g of the No. 3 lithium battery electrolyte sample, dilute it directly with pure water, shake well, and then perform anion chromatography analysis to detect C2O4. 2- According to BF4 - and C2O4 2- Given the concentration and peak area of ​​the target solution, and the corresponding concentration and peak area of ​​the standard solution, solve equations one and two simultaneously.

[0064]

[0065]

[0066] In the formula, X represents the content of lithium difluorooxalate borate in the electrolyte of the lithium battery to be tested, in ppm; Y represents the content of lithium dioxalate borate in the electrolyte of the lithium battery to be tested, in ppm; A 样B BF4 in lithium battery electrolyte was determined by anion chromatography. - BF4 in the test solution - Peak area; A 标B BF4 was determined by anion chromatography. - BF4 in standard solutions - Peak area; C 标B BF4 - BF4 in standard solution - Concentration, in ppm; multiple B To prepare lithium battery electrolyte BF4 - The dilution factor of the solution to be tested; A 样C Anion chromatography was used to determine C2O4 in lithium battery electrolyte. 2- C2O4 in the test solution 2- Peak area; A 标C C2O4 was determined by anion chromatography. 2- C2O4 in standard solution 2- Peak area; C 标C C2O4 2- C2O4 in standard solution 2- The concentration, in ppm;

[0067] multipleC To prepare lithium battery electrolyte C2O4 2- The dilution factor of the test solution; M1 is the molecular weight of lithium difluorooxalate borate, with a value of 143.79; M2 is the molecular weight of lithium difluorooxalate borate, with a value of 193.79; M3 is C2O4. 2- The molecular weight is 88; M4 is BF4. - The molecular weight is 86.8; 10000 is a constant.

[0068] The percentage content of LiODFB and LiBOB in the sample was calculated. The detection data and calculation results are shown in Table 5.

[0069] Table 5

[0070]

[0071] The test data shown in Table 5 are compared with the theoretical content values, and the test results are accurate. Therefore, the method for determining lithium difluorooxalate borate and lithium dioxalate borate in lithium battery electrolyte described in this invention can simultaneously and accurately determine the percentage content of LiODFB and LiBOB.

[0072] Experiment 6: Stability analysis of the electrolyte of lithium battery #3 to be tested.

[0073] Five samples of the lithium battery electrolyte to be tested (No. 3) were taken, and each sample was prepared as lithium battery electrolyte BF4. - The test solution and the lithium battery electrolyte C2O4 2- The test solution was then used to detect BF4. - and C2O4 2- The sample processing and analysis steps for each group are as follows: Preparation of lithium battery electrolyte BF4 - Test solution: Take approximately 1g of the No. 3 lithium battery electrolyte to be tested, add approximately 10g of water, then add 0.3g of a 30% hydrofluoric acid aqueous solution. Heat in an 80℃ oven for 2 hours, then remove and add water to approximately 100g, shake well, and then perform anion chromatography analysis to detect BF4. - Preparation of lithium battery electrolyte C2O4 2- Test solution: Weigh approximately 1g of the No. 3 lithium battery electrolyte sample, dilute it directly with pure water, shake well, and then perform anion chromatography analysis to detect C2O4. 2- According to BF4 - and C2O4 2- The concentrations and peak areas of the LiODFB and LiBOB in the samples were determined by combining equations one and two, and the percentage content of LiODFB and LiBOB in the samples was calculated. The detection results of the five groups of samples are shown in Table 6.

[0074] Table 6

[0075]

[0076] As can be seen from the data in Table 6, the data parallelism is good, that is, the method for determining lithium difluorooxalate borate and lithium dioxalate borate in the lithium battery electrolyte of the present invention has good stability.

[0077] The above experimental process shows that the method for determining lithium difluorooxalate borate and lithium dioxalate borate in lithium battery electrolytes described in this invention can effectively detect the content of LiODFB and LiBOB. This method is simple, convenient, accurate, and stable, thus providing a reliable means for the accurate determination of the content of each component in lithium battery electrolytes, thereby ensuring the quality of lithium battery electrolyte products.

Claims

1. The determination of lithium difluorooxalate borate and lithium dioxalate borate in lithium battery electrolyte includes the following steps: Preparation of BF4 - Standard solution stock solution: Weigh the raw material LiBF4, dilute it with pure water to form BF4. - Standard solution stock solution; Preparation of BF4 - Standard solution, weigh out BF4 - The standard solution stock solution was further diluted with pure water to form BF4. - Standard solution; Preparation of lithium battery electrolyte BF4 - Test solution: Take the lithium battery electrolyte to be tested, dilute it with water, add an excess of hydrofluoric acid aqueous solution, heat it at 60℃~80℃ to react, cool it after the reaction is completed, add water to further dilute it, shake it well and test it. Preparation of C2O4 2- Standard solution stock solution: C2O4 is prepared by diluting the primary standard reagent Na2C2O4 with pure water. 2- Standard solution stock solution; Preparation of C2O4 2- Standard solution: Take C2O4 2- The standard solution stock solution is further diluted with pure water to form C2O4. 2- Standard solution; Preparation of lithium battery electrolyte C2O4 2- Test solution: Weigh the lithium battery electrolyte to be tested and dilute it with pure water to form lithium battery electrolyte C2O4. 2- The solution to be tested; Instrumental analysis: An anion chromatography system was used. The regenerator was an aqueous sulfuric acid solution, and the eluent was an acetonitrile-water system containing Na₂CO₃ and NaHCO₃. The ion chromatography system used was an ICS-2100 ion chromatograph with a Shodex SI-90 4E anion column. The concentration of sulfuric acid solution was 0.07 mol / L to 0.09 mol / L. The concentrations of Na₂CO₃ and NaHCO₃ in the eluent were both 2.4 mmol / L, and the volume ratio of acetonitrile to water was 1:

3. BF4 respectively - Standard solution, C2O4 2- Standard solution, lithium battery electrolyte BF4 - Test solution, lithium battery electrolyte C2O4 2- The test solution was subjected to anion chromatography analysis, and the peak area was recorded. Calculate the contents of lithium difluorooxalate borate and lithium dioxalate borate by solving equations one and two simultaneously. ； In the formula, X represents the content of lithium difluorooxalate borate in the electrolyte of the lithium battery to be tested, in ppm; Y represents the content of lithium dioxaborate in the electrolyte of the lithium battery to be tested, in ppm; A 样B BF4 in lithium battery electrolyte was determined by anion chromatography. - BF4 in the test solution - Peak area; A 标B BF4 was determined by anion chromatography. - BF4 in standard solutions - Peak area; C 标B BF4 - BF4 in standard solution - Concentration, in ppm; multiple B To prepare lithium battery electrolyte BF4 - The dilution factor of the solution to be tested; A 样C Anion chromatography was used to determine C2O4 in lithium battery electrolyte. 2- C2O4 in the test solution 2- Peak area; A 标C C2O4 was determined by anion chromatography. 2- C2O4 in standard solution 2- Peak area; C 标C C2O4 2- C2O4 in standard solution 2- The concentration, in ppm; multiple C To prepare lithium battery electrolyte C2O4 2- The dilution factor of the test solution; M1 is the molecular weight of lithium difluorooxalate borate; M2 is the molecular weight of lithium difluorooxalate borate; M3 is C2O4. 2- Molecular weight; M4 is BF4 - The molecular weight; 10000 is a constant.

2. The determination of lithium difluorooxalateborate and lithium dioxalateborate in the lithium battery electrolyte according to claim 1, characterized in that: Preparation of C2O4 2- When preparing the standard solution stock solution, the primary standard reagent Na2C2O4 needs to be dried. The drying steps include: placing the primary standard reagent Na2C2O4 in a porcelain crucible and drying it at a constant temperature of 100±2℃ in an oven for 2 hours, and then placing it in a desiccator to cool for later use.

3. The determination of lithium difluorooxalate borate and lithium dioxalate borate in the lithium battery electrolyte according to claim 1, characterized in that: The purity of the raw material LiBF4 is greater than or equal to 99.9%.

4. The determination of lithium difluorooxalate borate and lithium dioxalate borate in the lithium battery electrolyte according to claim 1, characterized in that: Preparation of lithium battery electrolyte BF4 - When preparing the solution to be tested, add an excess of hydrofluoric acid aqueous solution and then heat the solution in an oven at 80°C to react.

5. The determination of lithium difluorooxalate borate and lithium dioxalate borate in the lithium battery electrolyte according to claim 1, characterized in that: The mass concentration of the hydrofluoric acid aqueous solution is 30%.

6. The determination of lithium difluorooxalateborate and lithium dioxalateborate in the lithium battery electrolyte according to claim 1, characterized in that: Prepared BF4 - The concentration of the standard solution is (25±2) ppm; Preparation of lithium battery electrolyte BF4 - The dilution factor for the test solution is 50 to 500 times; the prepared C2O4 2- The standard solution concentration was (25±2) ppm, and the lithium battery electrolyte C2O4 was prepared. 2- The solution to be tested is diluted by a factor of 50 to 500.

7. The determination of lithium difluorooxalateborate and lithium dioxalateborate in the lithium battery electrolyte according to claim 1, characterized in that: The Na2CO3 and NaHCO3 used in the rinsing solution were both of the primary standard grade, and the acetonitrile was of analytical grade. All pure water used in the preparation and dilution of the solutions was distilled water that met the GB-6682 Class III water standard.

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