Method for determining metal impurities in aromatic additive of lithium ion battery electrolyte

Abstract

The invention discloses a method for determining metal impurities in an aromatic additive of a lithium ion battery electrolyte, which comprises the following steps: 1, preparing metal impurity standard solutions with at least three gradient concentrations, the concentrations of all metal impurity elements in the metal impurity standard solutions with each gradient concentration being the same; 2, taking a to-be-detected sample, and diluting and dissolving the to-be-detected sample with propylene carbonate to obtain a to-be-detected sample solution; and 3, determining and analyzing the blank, the metal impurity standard solution and the to-be-detected sample solution by adopting an inductively coupled plasma emission spectrometer, determining all the metal impurity standard solutions with gradient concentrations to prepare a standard curve, and calculating the content of the metal impurities in the to-be-detected sample by adopting an external standard method. The method has the advantages of rapidness, high efficiency, accuracy, good reliability and high stability, and a reliable method is provided for determining the metal impurities in the aromatic additives of the lithium ion battery electrolyte, so that a guarantee is provided for the quality of the lithium ion battery electrolyte.

Description

Technical Field

[0001] The present invention relates to the technical field of component determination of additives for lithium ion battery electrolytes, and in particular to a method for determining metal impurities in aromatic additives. Background Art

[0002] Lithium-ion battery electrolytes are primarily composed of three components: solvents, salts, and additives. Additives are one of the key factors that differentiate the competitiveness of lithium-ion battery electrolytes, improving their performance and enabling them to meet the demands of different usage environments.

[0003] Aromatic additives, also known as compounds containing a benzene structure, primarily include BP (biphenyl), OTP (o-terphenyl), DPC (diphenyl carbonate), PA (phthalic anhydride), PDCA (pyridine-3,4-dicarboxylic anhydride), SAA (succinic anhydride), DDB (1,4-di-tert-butyl-2,5-dimethoxybenzene), MAH (maleic anhydride), and DFBP (2,4-difluorobiphenyl). Depending on their function, they can be categorized as membrane additives, high-temperature additives, low-temperature additives, rate additives, overcharge prevention additives, flame retardant additives, and neutralizing additives. The impurity content in the additives directly affects the additive's effectiveness, thereby impacting the performance of lithium-ion battery electrolytes. Therefore, accurate detection of metal impurities in aromatic additives is crucial.

[0004] Inductively coupled plasma emission spectrometry (ICP) is a commonly used instrument for lithium-ion battery electrolyte testing. However, the determination of metal impurities in aromatic additives presents the technical challenge of difficult sample pretreatment. Aromatic additives are compounds containing a benzene structure, which are insoluble in water. Using an aqueous phase, an acidic system, or an alkaline system as a diluent will cause them to be difficult to dissolve, resulting in solid precipitation and making them undetectable. Using other methods to pretreat the sample may result in sample loss during the dissolution process, making accurate determination impossible, time-consuming, and costly. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a method for determining metal impurities in aromatic additives of lithium ion battery electrolyte, which is rapid, accurate and stable.

[0006] To solve the above problems, the present invention adopts a technical solution: a method for determining metal impurities in aromatic additives for lithium-ion battery electrolytes, comprising the following steps: 1. preparing at least three metal impurity standard solutions with gradient concentrations, wherein the metal impurity standard solutions contain the metal impurity elements contained in the sample to be measured, and the concentrations of all metal impurity elements in each gradient concentration metal impurity standard solution are the same; 2. taking the sample to be measured, using propylene carbonate as a diluent, diluting and dissolving the sample to be measured, and diluting (30-60) times to obtain a sample solution to be measured; and 3. using an inductively coupled plasma emission spectrometer (ICP), inputting the concentrations of the metal impurity standard solutions with each gradient concentration and the dilution factor of the sample to be measured, and measuring an analytical blank, the metal impurity standard solutions with all gradient concentrations, and the sample solution to be measured, wherein the analytical blank is the propylene carbonate used as the diluent in the second step, and the metal impurity standard solutions with all gradient concentrations are measured to obtain a standard curve, and the content of the metal impurities in the sample to be measured is calculated using an external standard method.

[0007] Furthermore, in the aforementioned method for determining metal impurities in aromatic additives for lithium-ion battery electrolytes, the purity of the diluent propylene carbonate is above 99.99%.

[0008] Furthermore, in the aforementioned method for determining metal impurities in aromatic additives for lithium-ion battery electrolytes, the operating parameters of the inductively coupled plasma emission spectrometer include: analysis pump speed: 12 rpm; RF power 1.2 kW; stabilization time: 15 s; observation mode: axial; observation height: 8 mm; atomizing gas flow rate: 0.80 L / min; plasma gas flow rate: 14.0 L / min; and auxiliary gas flow rate: 1.20 L / min.

[0009] Furthermore, in the aforementioned method for determining metal impurities in aromatic additives for lithium-ion battery electrolytes, in the second step, the sample to be tested is diluted 50 times to obtain a sample solution to be tested.

[0010] Furthermore, in the aforementioned method for determining metal impurities in aromatic additives for lithium-ion battery electrolytes, the metal impurities include Al, Ca, Cr, Cu, Fe, K, Na, Ni, Pb, and Zn.

[0011] Furthermore, in the aforementioned method for determining metal impurities in aromatic additives for lithium-ion battery electrolytes, the metal impurity standard solution contains Al, Ca, Cr, Cu, Fe, K, Na, Ni, Pb, and Zn.

[0012] Furthermore, in the aforementioned method for determining metal impurities in aromatic additives for lithium-ion battery electrolytes, the metal impurity standard solution contains three gradient concentrations, which are (0.1000±0.01) ppm, (0.2000±0.02) ppm, and (0.3000±0.03) ppm.

[0013] Furthermore, the aforementioned method for determining metal impurities in aromatic additives for lithium-ion battery electrolytes, wherein the aromatic additives include biphenyl (BP), o-terphenyl (OTP), diphenyl carbonate (DPC), phthalic anhydride (PA), pyridine-3,4-dicarboxylic anhydride (PDCA), succinic anhydride (SAA), 1,4-di-tert-butyl-2,5-dimethoxybenzene (DDB), maleic anhydride (MAH), and 2,4-difluorobiphenyl (DFBP).

[0014] The advantages of the present invention are: the method for determining metal impurities in aromatic additives for lithium-ion battery electrolytes of the present invention is rapid, efficient, accurate, reliable, and highly stable, providing a reliable method for determining metal impurities in aromatic additives for lithium-ion battery electrolytes, thereby providing a guarantee for the quality of lithium-ion battery electrolytes. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is a schematic diagram of the standard curve. DETAILED DESCRIPTION

[0016] The following is a further detailed description of the method for determining metal impurities in the aromatic additives for lithium-ion battery electrolytes according to the present invention.

[0017] First, determine the diluent used to dilute and dissolve the sample to be tested.

[0018] Taking biphenyl (BP) and phthalic anhydride (PA) as examples, different diluents were selected to observe their solubility. Inductively coupled plasma emission spectrometry was used to measure different diluents and check the test status of each diluent.

[0019] BP and PA respectively use aqueous systems as diluents, and both have solid precipitation. Aromatic additives have poor solubility in aqueous diluents.

[0020] Table 1:

[0021] Diluent name Solubility Nitric acid water system Insoluble Ethanol-water system Insoluble

[0022] From Table 1, it can be seen that the sample to be tested is not soluble in the above-mentioned aqueous diluents, so it cannot be measured by inductively coupled plasma optical emission spectrometry.

[0023] BP and PA were dissolved using different organic solvents as diluents, and then measured using inductively coupled plasma emission spectrometry. The test results are shown in Table 2.

[0024] Table 2:

[0025] Diluent name Diluent boiling point (℃) Solubility Test Status Anhydrous ethanol 78 Completely dissolved Instrument off DMC (dimethyl carbonate) 90 Completely dissolved Instrument off DEC (diethyl carbonate) 126～128 Completely dissolved The instrument is normal EMC (ethyl methyl carbonate) 107 Completely dissolved Instrument off PC (propylene carbonate) 242 Completely dissolved The instrument is normal

[0026] Table 2 shows that the test samples were completely dissolved in the aforementioned organic solvents, as measured using an inductively coupled plasma optical emission spectrometer (Agilent 5800 ICP-OES). Anhydrous ethanol, dimethyl carbonate (DMC), and ethyl methyl carbonate (EMC) all extinguished the plasma during ICP analysis due to their low boiling points, indicating that these solvents are not suitable as diluents for ICP analysis. Only diethyl carbonate (DEC) and propylene carbonate (PC) did not extinguish the plasma during ICP analysis.

[0027] Next, diethyl carbonate (DEC) and propylene carbonate (PC) were used as diluents to detect the content of Al, Ca, Cr, Cu, Fe, K, Na, Ni, Pb, and Zn metal impurities in biphenyl (BP) using ICP. Three parallel measurements were performed on the test solutions diluted with each diluent. The results are shown in Table 3.

[0028] Table 3:

[0029]

[0030] During testing, it was observed that solutions using DEC (diethyl carbonate) as a diluent exhibited significant interference with the tail flame during ICP testing. The data in Table 3 indicate that using DEC as a diluent resulted in poor test result stability. Using PC as a diluent resulted in more stable test results.

[0031] Therefore, it was determined that propylene carbonate (PC) should be used as a diluent when using ICP to detect the content of metal impurities such as Al, Ca, Cr, Cu, Fe, K, Na, Ni, Pb, and Zn in aromatic additives.

[0032] The method for determining metal impurities in the aromatic additives for lithium-ion battery electrolytes of the present invention will be further described in detail below through specific examples.

[0033] The method for determining metal impurities in aromatic additives comprises the following steps.

[0034] 1. Prepare three metal impurity standard solutions with gradient concentrations: 1. Accurately weigh 100 μg / ml samples of three mixed metal element standard solutions containing Al, Ca, Cr, Cu, Fe, K, Na, Ni, Pb, and Zn. Mixed metal element standard solutions are commercially available. Dilute each of these mixed metal element standard solutions with propylene carbonate (PC) to obtain three metal impurity standard solutions with gradient concentrations of 0.0999 ppm, 0.2002 ppm, and 0.2997 ppm, respectively.

[0035] 2. Preparation of the sample solution: Weigh the sample using a 1 / 10,000 electronic balance, dilute it 50 times with propylene carbonate, and dissolve it by ultrasonication to obtain the sample solution.

[0036] 3. An inductively coupled plasma optical emission spectrometer (Agilent 5800ICP-OES) was used. The instrument conditions included: analytical pump speed: 12 rpm; RF power: 1.2 kW; stabilization time: 15 s; observation mode: axial; observation height: 8 mm; nebulizing gas flow rate: 0.80 L / min; plasma gas flow rate: 14.0 L / min; and auxiliary gas flow rate: 1.20 L / min.

[0037] Enter the ICP Expert instrument control software, click the worksheet icon, open the metal element analysis method for Al, Ca, Cr, Cu, Fe, K, Na, Ni, Pb, and Zn to be performed, and enter the analysis worksheet. Enter the metal impurity standard solution and the dilution multiple of the sample to be tested respectively, and sequentially measure the analytical blank, three gradient concentrations of metal impurity standard solutions, and the sample solution to be tested. The PC (propylene carbonate) used to prepare the sample solution to be tested is the analytical blank. The three gradient concentrations of metal impurity standard solutions are measured to obtain a standard curve with a linearity of ≥0.995. Figure 1 As shown. Ignite the plasma, wait for the instrument to stabilize, and analyze the sample solution. Using the external standard method, calculate the metal impurity content (ppm) of Al, Ca, Cr, Cu, Fe, K, Na, Ni, Pb, and Zn in the sample based on the obtained standard curve, and obtain the data results.

[0038] The aromatic additive biphenyl (BP) was the sample to be tested, and the test results using PC as the diluent are shown in Table 4.

[0039] Table 4:

[0040]

[0041] The aromatic additive phthalic anhydride (PA) was the sample to be tested, and the test results using PC as the diluent are shown in Table 5.

[0042] Table 5:

[0043]

[0044]

[0045] The aromatic additive o-terphenyl (OTP) was the sample to be tested, and the test results using PC as the diluent are shown in Table 6.

[0046] Table 6:

[0047]

[0048] The aromatic additive diphenyl carbonate (DPC) was the sample to be tested, and the test results using PC as the diluent are shown in Table 7.

[0049] Table 7:

[0050]

[0051] The aromatic additive 1,4-di-tert-butyl-2,5-dimethoxybenzene (DDB) was the sample to be tested, and the test results using PC as the diluent are shown in Table 8.

[0052] Table 8:

[0053]

[0054] It can be seen from Tables 4, 5, 6, 7 and 8 that the method for determining metal impurities in aromatic additives for lithium-ion battery electrolytes described in the present application has good stability.

[0055] The following sample recovery test is performed to further examine the analytical error and reliability of the determination method described in this application.

[0056] Three groups of sample solutions with known metal impurity concentrations were prepared. Three gradient concentrations of metal impurity solutions containing Al, Ca, Cr, Cu, Fe, K, Na, Ni, Pb, and Zn were added to each sample solution. The three gradient concentrations were approximately 0.1000 ppm, 0.2000 ppm, and 0.3000 ppm, respectively. The ICP results were measured and the recovery rate was calculated.

[0057] The results of the biphenyl (BP) test sample solution are shown in Table 9.

[0058] Table 9:

[0059]

[0060]

[0061] The results of the phthalic anhydride (PA) test sample solution are shown in Table 10.

[0062] Table 10:

[0063]

[0064]

[0065] As shown in Tables 9 and 10, the standard recovery rates of the determination methods for metal impurities in aromatic additives described in the present application are both between 94% and 111%. Therefore, the error of this method is small and can meet the analysis requirements.

[0066] From the above, it can be seen that the method for determining metal impurities in aromatic additives described in the present invention is rapid, efficient, accurate, reliable, and highly stable, providing a reliable method for determining metal impurities in aromatic additives for lithium-ion battery electrolytes, thereby ensuring the quality of lithium-ion battery electrolytes.

Claims

1. A method for determining metal impurities in aromatic additives for lithium-ion battery electrolytes, comprising the following steps:

1. Prepare at least three metal impurity standard solutions with gradient concentrations, wherein the metal impurity standard solutions contain the metal impurity elements contained in the sample to be tested, and the concentrations of all metal impurity elements in each gradient concentration metal impurity standard solution are the same; 2. Take the sample to be tested, use propylene carbonate as a diluent, dilute and dissolve the sample to be tested, and dilute it (30 to 60) times to obtain a sample solution to be tested; 3. Use an inductively coupled plasma emission spectrometer to input the concentrations of the metal impurity standard solutions with each gradient concentration and the dilution multiple of the sample to be tested, and measure an analytical blank, all metal impurity standard solutions with all gradient concentrations, and the sample solution to be tested, wherein the analytical blank is propylene carbonate used as a diluent in the second step, and all metal impurity standard solutions with all gradient concentrations are measured to obtain a standard curve, and the content of metal impurities in the sample to be tested is calculated using an external standard method.

2. The method for determining metal impurities in aromatic additives for lithium-ion battery electrolytes according to claim 1, wherein: The purity of the diluent propylene carbonate is above 99.99%.

3. The method for determining metal impurities in aromatic additives for lithium-ion battery electrolytes according to claim 1, wherein: The operating parameters of the inductively coupled plasma optical emission spectrometer include: analytical pump speed: 12 rpm; RF power: 1.2 kW; stabilization time: 15 s; observation mode: axial; observation height: 8 mm; nebulizer gas flow rate: 0.80 L / min; plasma gas flow rate: 14.0 L / min; and auxiliary gas flow rate: 1.20 L / min.

4. The method for determining metal impurities in aromatic additives for lithium ion battery electrolytes according to claim 1, 2 or 3, wherein: In the second step, the sample to be tested is diluted 50 times to obtain a sample solution to be tested.

5. The method for determining metal impurities in aromatic additives for lithium ion battery electrolyte according to claim 1, 2 or 3, characterized in that: The metal impurities include Al, Ca, Cr, Cu, Fe, K, Na, Ni, Pb, and Zn.

6. The method for determining metal impurities in aromatic additives for lithium-ion battery electrolytes according to claim 5, characterized in that: The metal impurity standard solution contains Al, Ca, Cr, Cu, Fe, K, Na, Ni, Pb, and Zn.

7. The method for determining metal impurities in aromatic additives for lithium-ion battery electrolytes according to claim 6, wherein: The metal impurity standard solution contains three gradient concentrations, which are (0.1000±0.01) ppm, (0.2000±0.02) ppm, and (0.3000±0.03) ppm.

8. The method for determining metal impurities in aromatic additives for lithium-ion battery electrolytes according to claim 1, wherein: The aromatic additives include biphenyl, o-terphenyl, diphenyl carbonate, phthalic anhydride, pyridine-3,4-dicarboxylic anhydride, succinic anhydride, 1,4-di-tert-butyl-2,5-dimethoxybenzene, maleic anhydride, and 2,4-difluorobiphenyl.

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