Method for detecting content of lithium salt in lithium ion battery electrolyte
By preparing mixed standard mother liquor of lithium-ion battery electrolyte and performing gradient dilution, combined with the testing technology of ion chromatograph, the problem of singularity and inaccuracy of lithium salt content detection in lithium-ion battery electrolyte in the prior art is solved, and the problem of singularity and inaccuracy of lithium-ion battery electrolyte in the prior art is realized. High-precision lithium salt content detection.
Patent Information
- Application Number
- CN202411594134.0
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-11-08
- Publication Date
- 2025-02-18
AI Technical Summary
The prior art has a problem of single detection and inaccuracy in detecting the lithium salt content in lithium-ion battery electrolytes, and it is impossible to fully reflect the lithium salt content in the electrolyte.
By preparing mixed standard mother liquors of different lithium salts and performing gradient dilution, using an ion chromatograph to test the standard mother liquor and the electrolyte sample to be detected, a standard curve for external standard statutory quantification was prepared, lithium salt was qualitative, and the response area was recorded, and lithium salt was calculated. content.
It realizes accurate detection of the lithium salt content in the electrolyte of lithium-ion battery, with a wide linear range, good linear relationship and repeatability, and high test accuracy.
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Figure CN119470697A_ABST
Abstract
Description
Technical Field
[0001] The invention belongs to the technical field of analysis and detection, and specifically relates to a method for detecting the lithium salt content in a lithium ion battery electrolyte. Background Art
[0002] Electrolyte lithium salt plays a vital role in lithium-ion batteries. It can provide a channel for ion transmission and realize the storage and release of electrical energy. Different types of electrolyte lithium salts have different characteristics and application fields. Choosing a suitable electrolyte lithium salt is very important for the performance and safety of lithium-ion batteries. With the continuous development of science and technology, the research on electrolyte lithium salts is also deepening, which will bring greater breakthroughs and progress to the application of lithium-ion batteries.
[0003] Lithium-ion battery electrolyte is mainly composed of three raw materials: solvent (such as PC, EC, DMC, EA, etc.), additives (such as VC, FEC, DTD, PS, etc.), and lithium salt. Lithium salts include conventional lithium salts, such as lithium hexafluorophosphate (LiPF6), and new lithium salts, such as lithium tetrafluoroborate (LiBF4), lithium dioxalatoborate (LiBOB), lithium difluorophosphate (LiPO2F2), lithium difluorooxalatoborate (LiODFB), lithium bis(fluorosulfonyl imide) (LiFSI), and lithium bis(trifluoromethylsulfonyl imide) (LiTFSI). The above lithium salts have their own advantages and disadvantages during use. For example, lithium bis(fluorosulfonyl)imide (LiFSI) has high ion conductivity, high decomposition temperature, and good safety, but its relative cost is also high, and it will corrode iron and aluminum foil during use; lithium difluorooxalate borate (LiODFB) has good electrochemical stability and good low-temperature performance, but its solubility is poor and its cost is also high; lithium tetrafluoroborate (LiBF4) is easy to dissociate, has low low-temperature impedance, high melting point, and excellent high-temperature performance, but it is easy to coordinate with organic solvents and has relatively low conductivity; lithium dioxalate borate (LiBOB) has good overcharge performance and thermal stability, and can form a passivation film on the surface of the aluminum current collector to inhibit the decomposition of the electrolyte and the dissolution of metal ions, but its ion conductivity is low, its solubility is poor, and its oxidation potential is low. In view of this, the lithium salt in the electrolyte is mainly composed of lithium hexafluorophosphate (LiPF6) plus one or more other lithium salt additives. The performance of the mixed lithium salt obtained after mixing is often better than that of a single lithium salt. Moreover, lithium salt, as the core of the electrolyte, accounts for the highest proportion of the cost, currently reaching about 50% to 60%.
[0004] At present, there are few studies on the testing methods for the content of lithium salts and their additives in lithium-ion battery electrolytes, and there are some drawbacks and blind spots. For example, the existing technology uses ion chromatography to test PF - 6 content, and F was detected by potentiometric titration - The content of PF - 6 decomposition amount. Finally, according to the ion chromatography test results and F -The content test results are converted into the content of LiPF6. This test method is relatively one-sided, as it only tests one major lithium salt of LiPF6 and cannot fully reflect the content of lithium salt in the electrolyte. The prior art also discloses the use of an ion chromatograph to test F - and PO4 3- After the content is determined, a series of calculations are performed to obtain the concentration of lithium salt (LiPF6). This method also only tests LiPF6, a lithium salt. The method is relatively one-sided and the calculation process is complicated. The prior art also provides an ion chromatography method using deionized water as the mobile phase. The standard sample and the electrolyte sample are diluted with deionized water, and the aged sample is allowed to stand for 5-20 minutes. The type of lithium salt in the electrolyte is qualitatively determined by retention time and spike addition. This method only qualitatively determines the type of lithium salt, but does not determine the content of the lithium salt. In addition, deionized water is used as the mobile phase, and the organic components in the electrolyte cannot be well separated. Long-term testing will cause the chromatographic column of the ion chromatograph to be blocked, resulting in the appearance of mixed peaks in the test, and it is impossible to accurately determine the various lithium salts.
[0005] Therefore, developing a simple and rapid method to detect the lithium salt content in the electrolyte can monitor the production quality of the electrolyte, analyze and develop excellent electrolyte formulas, and is of great significance for battery companies to control the quality of electrolyte suppliers. Summary of the invention
[0006] The present application provides a method for detecting the lithium salt content in a lithium ion battery electrolyte, aiming to solve the problem that the existing lithium salt content detection in a lithium ion battery electrolyte is single and inaccurate.
[0007] The present application provides a method for detecting the lithium salt content in a lithium ion battery electrolyte, comprising the following steps:
[0008] (1) preparing mixed standard solutions of different lithium salts, and performing gradient dilution on the standard solutions;
[0009] (2) using an ion chromatograph to test the gradient diluted standard stock solution, and preparing a standard curve for external standard method quantification based on the concentration of each lithium salt and the area of its corresponding peak;
[0010] (3) Using an ion chromatograph to test the electrolyte sample to be tested, qualitatively identifying the lithium salt by retention time and recording its corresponding response area, substituting the response area into the corresponding standard curve for lithium salt external standard method quantification, and obtaining the content of lithium salt.
[0011] The detection method described in the present application can accurately detect the content of lithium salt in the electrolyte of a lithium-ion battery. The detection method described in the present application has a wide detection linear range, good linear relationship and repeatability, and high test accuracy.
[0012] According to some embodiments of the method for detecting the lithium salt content in the lithium-ion battery electrolyte described in the present application, in step (1), the lithium salt includes one or more of lithium difluorooxalatoborate, lithium difluorophosphate, lithium tetrafluoroborate, lithium hexafluorophosphate, lithium dioxalatoborate and lithium bis(fluorosulfonyl)imide.
[0013] According to some embodiments of the method for detecting the lithium salt content in the lithium ion battery electrolyte described in the present application, in step (1), the concentration of lithium hexafluorophosphate in the standard mother solution is 100,000 ppm-150,000 ppm.
[0014] According to some embodiments of the method for detecting the lithium salt content in the lithium-ion battery electrolyte described in the present application, the concentration of lithium difluorooxalatoborate in the standard mother solution is 8000ppm-12000ppm.
[0015] According to some embodiments of the method for detecting the lithium salt content in the lithium-ion battery electrolyte described in the present application, the concentration of lithium difluorophosphate in the standard mother solution is 8000ppm-12000ppm.
[0016] According to some embodiments of the method for detecting the lithium salt content in the lithium-ion battery electrolyte described in the present application, the concentration of lithium tetrafluoroborate in the standard mother solution is 8000ppm-12000ppm.
[0017] According to some embodiments of the method for detecting the lithium salt content in the lithium-ion battery electrolyte described in the present application, the concentration of lithium dioxalatoborate in the standard mother solution is 8000ppm-12000ppm.
[0018] According to some embodiments of the method for detecting the lithium salt content in the lithium-ion battery electrolyte described in the present application, the concentration of lithium bis(fluorosulfonyl)imide in the standard mother solution is 36000 ppm-54000 ppm.
[0019] According to some embodiments of the method for detecting the lithium salt content in the lithium ion battery electrolyte described in the present application, in step (1), acetonitrile is used as a solvent to prepare the standard mother solution.
[0020] According to some embodiments of the method for detecting the lithium salt content in the lithium-ion battery electrolyte described in the present application, chromatographic grade acetonitrile is used as a solvent to prepare the standard mother solution.
[0021] According to some embodiments of the method for detecting the lithium salt content in a lithium-ion battery electrolyte described in the present application, the number of gradient dilutions is at least 3 times.
[0022] According to some embodiments of the method for detecting the lithium salt content in the lithium-ion battery electrolyte described in the present application, the dilution multiple each time is 10 times.
[0023] According to some embodiments of the method for detecting the lithium salt content in the lithium ion battery electrolyte described in the present application, in step (2), the test conditions of the ion chromatograph are:
[0024] The chromatographic column of the ion chromatograph is a Metrosep A Supp 5-250 chromatographic column, the mobile phase is a mixture of Na2CO3 aqueous solution and acetonitrile, the detector is an electrochemical detector, and the injection volume is 20uL.
[0025] According to some embodiments of the method for detecting the lithium salt content in the lithium-ion battery electrolyte described in the present application, the concentration of the Na2CO3 aqueous solution in the mobile phase is 4-6 mmol / L.
[0026] According to some embodiments of the method for detecting the lithium salt content in the lithium-ion battery electrolyte described in the present application, the volume ratio of the Na2CO3 aqueous solution and acetonitrile is (1.5-2):1.
[0027] According to some embodiments of the method for detecting the lithium salt content in the lithium ion battery electrolyte described in the present application, the flow rate of the mobile phase is 0.6-0.8 mL / min.
[0028] According to some embodiments of the method for detecting the lithium salt content in the lithium-ion battery electrolyte described in the present application, in step (2), the standard curve is: A=a*C+b; wherein A is the response area of the lithium salt; C is the concentration of the lithium salt in the standard mother solution; a is the slope of the curve; b is the intercept, and b=0 when passing through the origin.
[0029] According to some embodiments of the method for detecting the lithium salt content in a lithium-ion battery electrolyte described in the present application, in step (3), the electrolyte sample to be detected is diluted and then tested.
[0030] According to some embodiments of the method for detecting the lithium salt content in the lithium-ion battery electrolyte described in the present application, ultrapure water is used to dilute the electrolyte sample to be detected.
[0031] According to some embodiments of the method for detecting the lithium salt content in the lithium-ion battery electrolyte described in the present application, the detection method further includes using an ion chromatograph to test the peak times of different lithium salts to qualitatively analyze the lithium salts.
[0032] According to some embodiments of the method for detecting the lithium salt content in the lithium-ion battery electrolyte described in the present application, different lithium salts are prepared into solutions with a concentration of 100ppm-300ppm using ultrapure water, and the peak times of different lithium salts are tested using an ion chromatograph.
[0033] According to some embodiments of the method for detecting the lithium salt content in the lithium-ion battery electrolyte described in the present application, the lithium salt includes one or more of lithium difluorooxalatoborate, lithium difluorophosphate, lithium tetrafluoroborate, lithium hexafluorophosphate, lithium dioxalatoborate and lithium bis(fluorosulfonyl)imide. BRIEF DESCRIPTION OF THE DRAWINGS
[0034] Figure 1 The ion chromatograms of the lithium salts described in Example 1 of the present application;
[0035] Figure 2 This is the linear relationship diagram of the standard curve of lithium difluorooxalate borate;
[0036] Figure 3 This is the linear relationship diagram of the standard curve of lithium difluorophosphate;
[0037] Figure 4 This is the linear relationship diagram of the standard curve of lithium tetrafluoroborate;
[0038] Figure 5 This is the linear relationship diagram of the standard curve of lithium hexafluorophosphate;
[0039] Figure 6 This is the linear relationship diagram of the standard curve of lithium dioxalate borate;
[0040] Figure 7 This is the linear relationship diagram of the standard curve of bis(fluorosulfonyl)imide;
[0041] Figure 8 The ion chromatogram of the lithium ion battery electrolyte described in Example 2;
[0042] Fig. 9 This is the corresponding ion chromatogram after the electrolyte sample described in Example 3 is spiked and superimposed. DETAILED DESCRIPTION
[0043] Embodiments of the present invention are described in detail below, and examples of the embodiments are shown in the accompanying drawings. The embodiments described below with reference to the accompanying drawings are exemplary and intended to be used to explain the present invention, but should not be understood as limiting the present invention.
[0044] In the present invention, the terms "one embodiment", "some embodiments", "examples", "specific examples", or "some examples" etc. mean that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the described specific features, structures, materials or characteristics may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.
[0045] The present application provides a method for detecting the lithium salt content in a lithium ion battery electrolyte, comprising the following steps:
[0046] (1) preparing mixed standard solutions of different lithium salts, and performing gradient dilution on the standard solutions;
[0047] (2) using an ion chromatograph to test the gradient diluted standard stock solution, and preparing a standard curve for external standard method quantification based on the concentration of each lithium salt and the area of its corresponding peak;
[0048] (3) Using an ion chromatograph to test the electrolyte sample to be tested, qualitatively identifying the lithium salt by retention time and recording its corresponding response area, substituting the response area into the corresponding standard curve for lithium salt external standard method quantification, and obtaining the content of lithium salt.
[0049] The detection method described in the present application can accurately detect the content of lithium salt in the electrolyte of a lithium-ion battery. The detection method described in the present application has a wide detection linear range, good linear relationship and repeatability, and high test accuracy.
[0050] In some embodiments of the present application, in step (1), the lithium salt includes one or more of lithium difluorooxalatoborate (ODFB), lithium difluorophosphate, lithium tetrafluoroborate, lithium hexafluorophosphate, lithium dioxalatoborate and lithium bis(fluorosulfonyl)imide.
[0051] In some embodiments of the present application, in step (1), the concentration of lithium hexafluorophosphate in the standard mother solution is 100,000 ppm-150,000 ppm; for example, 100,000 ppm, 120,000 ppm, 130,000 ppm, 150,000 ppm, etc.
[0052] In some embodiments of the present application, the concentration of lithium difluorooxalatoborate in the standard mother solution is 8000ppm-12000ppm; for example, 8000ppm, 10000ppm, 11000ppm, 12000ppm, etc.
[0053] In some embodiments of the present application, the concentration of lithium difluorophosphate in the standard mother solution is 8000ppm-12000ppm; for example, 8000ppm, 10000ppm, 11000ppm, 12000ppm, etc.
[0054] In some embodiments of the present application, the concentration of lithium tetrafluoroborate in the standard mother solution is 8000ppm-12000ppm; for example, 8000ppm, 10000ppm, 11000ppm, 12000ppm, etc.
[0055] In some embodiments of the present application, the concentration of lithium dioxalatoborate in the standard mother solution is 8000ppm-12000ppm; for example, 8000ppm, 10000ppm, 11000ppm, 12000ppm, etc.
[0056] In some embodiments of the present application, the concentration of lithium bis(fluorosulfonyl)imide in the standard mother solution is 36000ppm-54000ppm; for example, 36000ppm, 38000ppm, 40000ppm, 45000ppm, 48000ppm, 50000ppm, 54000ppm, etc.
[0057] In some embodiments of the present application, in step (1), acetonitrile is used as a solvent to prepare the standard mother solution, preferably chromatographic grade acetonitrile.
[0058] In some embodiments of the present application, the number of gradient dilutions is at least 3 times, and preferably, the multiple of each dilution is 10 times.
[0059] In some embodiments of the present application, in step (2), the test conditions of the ion chromatograph are:
[0060] The chromatographic column of the ion chromatograph is a Metrosep A Supp 5-250 chromatographic column, the mobile phase is a mixture of Na2CO3 aqueous solution and acetonitrile, the detector is an electrochemical detector, and the injection volume is 20uL.
[0061] In some embodiments of the present application, the concentration of the Na2CO3 aqueous solution in the mobile phase is 4-6mmol / L; for example, 4mmol / L, 5mmol / L, 6mmol / L, etc.
[0062] In some embodiments of the present application, the volume ratio of the Na2CO3 aqueous solution and acetonitrile is (1.5-2):1, for example, 1.5:1, 1.6:1, 1.8:1, 2:1, etc.
[0063] In some embodiments of the present application, the flow rate of the mobile phase is 0.6-0.8 mL / min, such as 0.6 mL / min, 0.7 mL / min, 0.8 mL / min, etc. If the flow rate is too low, the peak time of the substance will be late and the analysis and testing time will be long; if the flow rate is too high, the pressure of the chromatographic column will be too high, causing damage to the chromatographic column.
[0064] In some embodiments of the present application, in step (2), the standard curve is: A = a*C + b;
[0065] Wherein, A is the response area of lithium salt; C is the concentration of lithium salt in the standard mother solution; a is the slope of the curve; b is the intercept, and b=0 when passing through the origin.
[0066] In some embodiments of the present application, in step (3), the electrolyte sample to be tested is diluted and then tested.
[0067] In some embodiments of the present application, ultrapure water is used to dilute the electrolyte sample to be detected.
[0068] In some embodiments of the present application, the detection method further comprises using an ion chromatograph to test the peak times of different lithium salts to conduct qualitative analysis of the lithium salts.
[0069] In some embodiments of the present application, ultrapure water is used to prepare different lithium salts into solutions with concentrations of 100ppm-300ppm, for example, 100ppm, 120ppm, 150ppm, 180ppm, 200ppm, 230ppm, 260ppm, 300ppm, etc., and an ion chromatograph is used to test the peak times of different lithium salts; preferably, the lithium salt includes one or more of lithium difluorooxalatoborate, lithium difluorophosphate, lithium tetrafluoroborate, lithium hexafluorophosphate, lithium dioxalatoborate and lithium bis(fluorosulfonyl)imide.
[0070] The present application is further described below in conjunction with specific embodiments and drawings.
[0071] Example 1
[0072] A method for detecting the lithium salt content in a lithium ion battery electrolyte comprises the following steps:
[0073] Prepare lithium salt single standards, and use ion chromatography to test each lithium salt single standard to confirm the peak time of each lithium salt, and qualitatively analyze the lithium salt by the peak time:
[0074] The specific operations are:
[0075] Accurately weigh 0.002g of lithium tetrafluoroborate (LiBF4), 0.002g of lithium dioxalatoborate (LiBOB), 0.002g of lithium difluorophosphate (LiPO2F2), 0.002g of lithium difluorooxalatoborate (LiODFB), 0.002g of lithium bis(fluorosulfonyl)imide (LiFSI), and 0.002g of lithium hexafluorophosphate (LiPF6) and place them in 10ml centrifuge tubes respectively, add ultrapure water to 10g (accurate to 1mg) to prepare lithium salt single-label A series solutions of different concentrations.
[0076] An ion chromatograph was used for testing (the test conditions of the ion chromatograph were as follows: the chromatographic column of the ion chromatograph was a Metrosep A Supp 5-250 chromatographic column, the mobile phase was a mixture of Na2CO3 aqueous solution and acetonitrile in a volume ratio of 62:38, wherein the concentration of the Na2CO3 aqueous solution was 5mmol / L (millimoles per liter), the flow rate of the mobile phase was 0.7mL / min, the detector was an electrochemical detector, and the injection volume was 20uL) to confirm the peak time of each lithium salt. The peak time of each lithium salt is shown in Table 1, and the corresponding ion chromatogram is shown in Figure 1 shown.
[0077] Table 1
[0078] Serial number Chinese name Lithium salt abbreviation Peak time 1 Lithium difluorooxalate borate LiODFB 4.88 2 Lithium difluorophosphate <![CDATA[LiPO2F2]]> 6.35 3 Lithium tetrafluoroborate <![CDATA[LiBF4]]> 8.43 4 Lithium hexafluorophosphate <![CDATA[LiPF6]]> 13.87 5 Lithium dioxalate borate LiBOB 17.79 6 Bis(fluorosulfonyl)imide LiFSI 24.90
[0079] The lithium salt mixed standard mother solution was prepared using chromatographic grade acetonitrile. The proportions of various lithium salts in the electrolyte in the lithium salt mixed standard mother solution are shown in Table 2:
[0080] Table 2
[0081]
[0082]
[0083] Weigh a certain amount of prepared lithium salt mixed standard mother solution into a 10ml centrifuge tube, and use ultrapure water to dilute the mixed standard mother solution into 3 lithium salt standard curve concentration points of different concentrations (gradient dilution with a coefficient multiple of 10 times each time), and use ion chromatograph to test and analyze (the test conditions of the ion chromatograph are: the chromatographic column of the ion chromatograph is a Metrosep ASupp 5-250 chromatographic column, the mobile phase is a mixture of Na2CO3 aqueous solution and acetonitrile with a volume ratio of 62:38, wherein the concentration of Na2CO3 aqueous solution is 5mmol / L (millimoles per liter), the flow rate of the mobile phase is 0.7mL / min, the detector is an electrochemical detector, and the injection volume is 20uL), and a standard curve for external standard method quantification is prepared according to the concentration of each lithium salt and the area of its corresponding peak, and the standard curve is set to pass through the origin. The linear relationship of each lithium salt standard curve is:
[0084] Lithium difluorooxalatoborate (LiODFB): A = 4.49052*10 -4 *20*C
[0085] Lithium difluorophosphate (LiPO2F2): A = 5.37851*10 -3 *20*C
[0086] Lithium tetrafluoroborate (LiBF4): A = 7.67611*10 -3 *20*C
[0087] Lithium hexafluorophosphate (LiPF6): A = 2.67843*10 -3 *20*C
[0088] Lithium bis(oxalatoborate) (LiBOB): A = 5.20240*10 -3 *20*C
[0089] Bis(fluorosulfonyl)imide (LiFSI): A = 1.86631*10 -3 *20*C
[0090] Where: C is the concentration of lithium salt in the standard mother solution, and A is the response area of lithium salt.
[0091] The linear relationship diagram of the standard curve corresponding to each lithium salt is as follows Figure 2-7 shown.
[0092] Weigh a certain amount of the prepared lithium salt mixed standard mother solution again into a 10mL centrifuge tube, add ultrapure water to dilute to 10g and mix evenly, filter the diluted sample with a 0.22um filter head, and then use an ion chromatograph for testing (test conditions are the same as above). Test the standard sample in parallel for 6 consecutive times, recorded as Sample 1-6, and use the external standard method quantitative standard curve to quantify the lithium salt content in the prepared standard sample. The test results are shown in Table 3 below.
[0093] Table 3
[0094]
[0095]
[0096] It can be seen from Table 3 that the relative standard deviation of the standard sample was less than 5% after 6 consecutive parallel tests, and the error between the actual value and the mean value was small, indicating that this method is stable, accurate and reliable.
[0097] Example 2
[0098] A method for detecting the lithium salt content in a lithium ion battery electrolyte comprises the following steps:
[0099] Accurately weigh 0.1g of lithium-ion battery electrolyte sample provided by Jiujiang Tianci Electrolyte Manufacturer (the lithium salt content contained in it is known, as shown in Table 4) into a 10ml centrifuge tube, add ultrapure water to dilute the total mass to about 10g, mix evenly, filter with a 0.22um filter head, and wait for the machine test. Repeat the steps (accurately weigh 0.1g of lithium-ion battery electrolyte sample provided by Jiujiang Tianci electrolyte manufacturer in a 10ml centrifuge tube, add ultrapure water to record the total mass and dilute to about 10g, mix evenly, filter with a 0.22um filter head, and wait for machine testing) 2 times, and the electrolyte dilutions obtained three times are respectively recorded as Sample 1-3, and tested and analyzed by ion chromatograph (the test conditions of the ion chromatograph are: the chromatographic column of the ion chromatograph is a MetrosepA Supp 5-250 chromatographic column, and the mobile phase is a mixture of Na2CO3 aqueous solution and acetonitrile in a volume ratio of 62:38, wherein the concentration of Na2CO3 aqueous solution is 5mmol / L (millimoles per liter), the flow rate of the mobile phase is 0.7mL / min, the detector is an electrochemical detector, and the injection volume is 20uL) Use the external standard method standard curve made in Example 1 to qualitatively and quantitatively analyze the lithium salt content in the sample.
[0100] The ion chromatogram corresponding to the lithium ion battery electrolyte described in Example 2 is as follows Figure 8 shown.
[0101] The sample sampling volume and machine-readable concentration data are shown in Table 5 below. The test results calculated according to Formula 1 are shown in Table 6 below.
[0102] Formula 1 is:
[0103] Among them, ω%--the proportion of lithium salt in the electrolyte
[0104] C—machine readable concentration (ug / g)
[0105] M---Total mass after dilution (g)
[0106] m---mass of electrolyte sample (g).
[0107] Table 4
[0108]
[0109]
[0110] Table 5
[0111] Lithium salts Sample1 Sample2 Sample3 Sample mass (g) 0.1028 0.1034 0.1153 Total mass after dilution (g) 10.1432 10.0586 10.1846 PF6 test content (ug / g) 1014.50 1024.89 1132.10 FSI test content (ug / g) 254.39 255.97 281.89
[0112] Table 6
[0113]
[0114] It can be seen from Table 6 that the electrolyte samples were tested three times in parallel, and the relative standard deviation was less than 1%, and the error between the actual value and the mean was small, indicating that this method is stable, accurate and reliable.
[0115] Example 3
[0116] An appropriate amount of lithium salt mixed standard mother solution was added to each of the three samples tested in Example 2. The amount of lithium salt mixed standard mother solution added to each 100uL sample was 0.0876g. The samples were tested using an ion chromatograph (test conditions were the same as above). The lithium salt content in the samples was quantified using the external standard method standard curve. The test data and the spike recovery rate are shown in Table 7 below:
[0117] The ion chromatograms corresponding to the spiked electrolyte samples in Example 3 are shown in FIG. Fig. 9 shown.
[0118] Table 7
[0119]
[0120] It can be seen from Table 7 that the sample spike recovery rate ranges from 95% to 105%, indicating that the test method described in this application is accurate, has a small systematic error, and has high accuracy.
[0121] Although the above embodiments have been shown and described, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations on the present invention. Changes, modifications, substitutions and variations of the above embodiments by those of ordinary skill in the art are all within the scope of protection of the present invention.
Claims
1. A method for detecting the lithium salt content in a lithium ion battery electrolyte, characterized in that: The following steps are involved: (1) preparing mixed standard solutions of different lithium salts, and performing gradient dilution on the standard solutions; (2) using an ion chromatograph to test the gradient diluted standard stock solution, and preparing a standard curve for external standard method quantification based on the concentration of each lithium salt and the area of its corresponding peak; (3) Using an ion chromatograph to test the electrolyte sample to be tested, qualitatively identifying the lithium salt by retention time and recording its corresponding response area, substituting the response area into the corresponding standard curve for lithium salt external standard method quantification, and obtaining the content of lithium salt.
2. The method for detecting the lithium salt content in a lithium ion battery electrolyte according to claim 1, characterized in that: In step (1), the lithium salt includes one or more of lithium difluorooxalatoborate, lithium difluorophosphate, lithium tetrafluoroborate, lithium hexafluorophosphate, lithium dioxalatoborate and lithium bis(fluorosulfonyl)imide.
3. The method for detecting the lithium salt content in a lithium ion battery electrolyte according to claim 2, characterized in that: In step (1), the concentration of lithium hexafluorophosphate in the standard mother solution is 100000ppm-150000ppm; And / or, the concentration of lithium difluorooxalatoborate in the standard mother solution is 8000ppm-12000ppm; And / or, the concentration of lithium difluorophosphate in the standard mother solution is 8000ppm-12000ppm; And / or, the concentration of lithium tetrafluoroborate in the standard mother solution is 8000ppm-12000ppm; And / or, the concentration of lithium bis(oxalatoborate) in the standard mother solution is 8000ppm-12000ppm; And / or, the concentration of lithium bis(fluorosulfonyl)imide in the standard mother solution is 36000ppm-54000ppm.
4. The method for detecting the lithium salt content in a lithium ion battery electrolyte according to claim 1, characterized in that: In step (1), acetonitrile is used as a solvent to prepare the standard mother solution, preferably chromatographic grade acetonitrile; And / or, the number of gradient dilutions is at least 3 times, preferably, the dilution multiple is 10 times.
5. The method for detecting the lithium salt content in a lithium ion battery electrolyte according to claim 1, characterized in that: In step (2), the test conditions of the ion chromatograph are: The chromatographic column of the ion chromatograph is a Metrosep A Supp 5-250 chromatographic column, the mobile phase is a mixture of Na2CO3 aqueous solution and acetonitrile, the detector is an electrochemical detector, and the injection volume is 20uL.
6. The method for detecting the lithium salt content in a lithium ion battery electrolyte according to claim 5, characterized in that: The concentration of the Na2CO3 aqueous solution in the mobile phase is 4-6mmol / L; Preferably, the volume ratio of the Na2CO3 aqueous solution to acetonitrile is (1.5-2):1; Preferably, the flow rate of the mobile phase is 0.6-0.8 mL / min.
7. The method for detecting the lithium salt content in a lithium ion battery electrolyte according to claim 1, characterized in that: In step (2), the standard curve is: A = a*C + b; Wherein, A is the response area of lithium salt; C is the concentration of lithium salt in the standard mother solution; a is the slope of the curve; b is the intercept, and b=0 when passing through the origin.
8. The method for detecting the lithium salt content in a lithium ion battery electrolyte according to claim 1, characterized in that: In step (3), the electrolyte sample to be tested is diluted and then tested; Preferably, ultrapure water is used to dilute the electrolyte sample to be detected.
9. The method for detecting the lithium salt content in a lithium ion battery electrolyte according to claim 1, characterized in that: The detection method also includes using an ion chromatograph to test the peak times of different lithium salts to qualitatively characterize the lithium salts.
10. The method for detecting the lithium salt content in a lithium ion battery electrolyte according to claim 9, characterized in that: Ultrapure water was used to prepare different lithium salts into solutions with a concentration of 100ppm-300ppm, and an ion chromatograph was used to test the peak times of the different lithium salts. Preferably, the lithium salt includes one or more of lithium difluorooxalatoborate, lithium difluorophosphate, lithium tetrafluoroborate, lithium hexafluorophosphate, lithium dioxalatoborate and lithium bis(fluorosulfonyl)imide.