A method for correcting aluminum content in elemental determination of molybdenum-containing lithium-ion battery cathode materials

Abstract

The application discloses a method for correcting aluminum content in element determination of a lithium ion battery positive electrode material containing molybdenum, and the positive electrode material is a ternary positive electrode rod material, and the method is characterized in that the method comprises the following steps: (1) dispersing phosphomolybdic acid in an organic solvent; (2) dissolving the ternary positive electrode material in hydrochloric acid as a primary sample; (3) adding the primary sample to the molybdenum-containing solution obtained in the step (2) after the molybdenum-containing solution is evaporated to dryness, so that the molybdenum element concentration is increased; (4) determining the contents of aluminum and molybdenum elements in the primary sample and the molybdenum-doped sample by inductively coupled plasma atomic emission spectrometry; and (5) obtaining the content of the aluminum element by graphic method, wherein the interference of molybdenum is eliminated. The application does not need to modify the equipment, and only needs to additionally add a molybdenum source reagent. The operation is simple, and the method can be conveniently attached to a standard determination process.

Description

Technical Field

[0001] This invention relates to the field of elemental analysis, and more specifically, to the determination of elements in lithium-ion battery cathode materials by inductively coupled plasma (ICP) emission spectroscopy, particularly a method for correcting aluminum content in the elemental determination of molybdenum-containing lithium-ion battery cathode materials. Background Technology

[0002] The main metallic elements in commonly used ternary cathode materials for lithium-ion batteries are nickel, cobalt, and manganese (NCM type) or nickel, cobalt, and aluminum (NCA type). Some ternary cathode materials also contain nickel, cobalt, manganese, and aluminum as the main elements, such as Chinese patent CN110518206. Molybdenum oxide has good corrosion resistance. In some new ternary cathode materials, molybdenum oxide or other molybdenum-containing substances are often used to encapsulate the ternary material nanoparticles to prevent them from pulverizing under the corrosion of the electrolyte, such as Chinese patents CN108091852 and CN113054168.

[0003] In the chemical composition analysis of the aforementioned ternary materials, due to their complex composition and preparation processes, and referring to the People's Republic of China Nonferrous Metals Industry Standard YS / T1006.2-2014, inductively coupled plasma atomic emission spectrometry (ICP-AES) is generally required to determine the content of their main metallic elements. In this standard, the recommended spectral line for aluminum is Al(I) 396.153 nm. However, this wavelength almost completely overlaps with the spectral line for molybdenum, Mo(II) 396.151 nm. Therefore, when the ternary material contains a molybdenum coating, the qualitative and quantitative measurements of aluminum will be significantly affected. Furthermore, among other available spectral lines for aluminum, Al(I) 237.312 nm almost overlaps with Co(I) 237.309 nm, and Al(I) 394.401 nm strongly interferes with Ni(I) 394.410 nm. Since high concentrations of cobalt and nickel are always present in ternary materials, these alternative spectral lines are also unusable. However, the spectral line at 204.598 nm of Mo(II) is far from the interference of common elements in all ternary materials and can be used to determine the molybdenum content in the sample.

[0004] Phosphomolybdic acid is a small-molecule heteropoly acid with the molecular formula H3PO4·12MoO3. It has certain solubility in water, ethanol, and ether. It is stable, does not decompose in strong acids, and can be stored for a long time in non-reducing solutions. Summary of the Invention

[0005] To address the problem that molybdenum in some novel ternary cathode materials for lithium-ion batteries severely interferes with the determination of aluminum content, the purpose of this invention is to provide a method for correcting aluminum content in the elemental determination of molybdenum-containing lithium-ion battery cathode materials.

[0006] The objective of this invention is achieved through the following method: a method for correcting aluminum content in the elemental determination of molybdenum-containing lithium-ion battery cathode materials, wherein the cathode material is a ternary cathode rod, characterized by comprising the following steps: (1) Prepare a molybdenum-containing organic solution by dispersing phosphomolybdic acid in an organic solvent; (2) Dissolve the ternary cathode material in hydrochloric acid solution to obtain the original solution of the original sample; (3) Take the organic solution obtained in step (1) and evaporate it to dryness. Then inject part of the original solution obtained in step (2) into it and shake it quickly to redisperse the phosphomolybdic acid in the new solution as a molybdenum doping solution to increase the molybdenum element concentration. (4) The original solution and the molybdenum-doped solution were determined by inductively coupled plasma (ICP) emission spectroscopy, respectively. The aluminum content was determined at 396.153 nm for Al (I) and the molybdenum content was determined at 204.598 nm for Mo (II). (5) Plot the concentrations of the original solution and the molybdenum-doped solution on the graph with molybdenum content as the horizontal axis and aluminum content as the vertical axis; draw boxes representing measurement error outside the corresponding data points, and use the attached diagram as an example. Figure 1 The graphical method shown obtains the corrected aluminum content on the vertical axis.

[0007] The aluminum content to eliminate molybdenum interference was obtained using a graphical method.

[0008] In step (5), the center point of each box is on the corresponding data point, its height is twice the average deviation d of the aluminum element measurement value of the corresponding data point, and its width is twice the average deviation d of the molybdenum element measurement value of the corresponding data point.

[0009] As attached Figure 1 As shown, in the graphical method, connecting two data points and a box, and extending it to the vertical axis, the corresponding intercept range is the corrected range of aluminum concentration.

[0010] Preferably, ethanol or diethyl ether is used as a solvent in step (1).

[0011] Preferably, the measurement methods and parameters in steps (2) and (4) shall be performed in accordance with the People's Republic of China Nonferrous Metals Industry Standard YS / T1006.2-2014.

[0012] Preferably, the average deviation value in step (5) is obtained by the ICP device based on the results of 5 consecutive rapid measurements.

[0013] The mechanism of this invention is as follows: Since molybdenum oxides are often poorly soluble in strong acids, the method of this invention cannot directly obtain the molybdenum content in the sample. However, by adding the molybdenum oxide, its interference with the determination of aluminum can be eliminated. The characteristic of phosphomolybdic acid, which is soluble in both some organic substances and water, is beneficial for specific experimental operations and improves accuracy.

[0014] To address the problem that molybdenum in some novel ternary cathode materials for lithium-ion batteries severely interferes with the determination of aluminum content, a method for correcting aluminum content in the elemental determination of molybdenum-containing lithium-ion battery cathode materials has been invented. The advantages of this invention are: (1) No equipment modification is required, only the molybdenum source reagent needs to be added; (2) It is easy to operate and can be easily added to the standard measurement process. Attached Figure Description

[0015] Figure 1 Aluminum element concentration correction chart; The experimental data are attached. Figure 1 Plot the corrected aluminum ion concentration on the vertical axis and calculate the aluminum content in the ternary material. Where C: the corrected aluminum ion concentration; H: the upper limit of the corrected aluminum ion concentration; L: the lower limit of the corrected aluminum ion concentration; d: the standard deviation of the concentration measurement (which varies for each element in each measurement). Detailed Implementation

[0016] The present invention will be further illustrated below with reference to specific embodiments. Unless otherwise specified, the experimental methods used in the following embodiments are conventional methods. Unless otherwise specified, the materials and reagents used in the following embodiments are commercially available. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention.

[0017] Example 1. The method for correcting aluminum content in the elemental determination of molybdenum-containing lithium-ion battery cathode materials by applying molybdenum using ethanol as a solvent is as follows: (1) Preparation of molybdenum-containing solution: Add 15.9 mg of commercially available analytical grade phosphomolybdic acid to 100 mL of pre-dried ethanol and stir thoroughly. The molybdenum content in this molybdenum-containing solution is 100 mg / L. -1 In 0-10 o Store in refrigerator C; (2) Preparation of the original solution for the ternary cathode material sample: Ternary cathode material was prepared according to YS / T1006.2-2014 standard. 0.20 g of solid material was accurately weighed and placed in a 100 mL polytetrafluoroethylene beaker. 20 mL of 36% concentrated hydrochloric acid was added to dissolve the material. After cooling, the solution was diluted to 200 mL in a volumetric flask and immediately transferred to a plastic reagent bottle for later use. This is the original sample solution. (3) Preparation of molybdenum-doped samples: Take 0.1 mL of the molybdenum-containing organic solution obtained in step (1) with a micropipette and place it in a 10 mL plastic centrifuge tube. Leave it open for about 30 min to allow the ethanol in the solution to evaporate. Then, take 10 mL of the original sample solution obtained in step (2) and add it to the plastic centrifuge tube. Shake repeatedly for 2 min to redisperse the phosphomolybdic acid in the sample to obtain the molybdenum-doped solution sample. (4) Determination of aluminum and molybdenum elements in the original sample solution and the molybdenum-doped sample: The ICP equipment was set to perform 5 consecutive measurements and the average value and average deviation d were calculated. The concentrations of aluminum ions and molybdenum ions in the original sample and the molybdenum-doped sample were determined by standard curve method according to the method described in YS / T1006.2-2014. The wavelength used for aluminum was 396.153 nm; the wavelength used for molybdenum was 204.598 nm. The preparation of molybdenum standard solution was carried out in accordance with GB / T 20975.25-2020. (5) Aluminum ion concentration correction: Plot the measured concentrations of the original sample solution and the molybdenum-doped sample solution on... Figure 1 In the diagram, molybdenum content is plotted on the horizontal axis and aluminum content on the vertical axis; boxes representing measurement error are drawn outside the corresponding data points, and the results are illustrated in the appendix. Figure 1 The graphical method shown obtains the corrected aluminum content on the vertical axis. The corrected aluminum ion concentration is then plotted on the vertical axis, and the aluminum content in the ternary material is calculated.

[0018] Example 2 A method for correcting aluminum content in the elemental determination of molybdenum-containing lithium-ion battery cathode materials by applying molybdenum using diethyl ether as a solvent, following these steps: Because diethyl ether evaporates quickly, the molybdenum content can be adjusted on-site.

[0019] (1) Preparation of molybdenum-containing solution: 15.9 mg of commercially available analytical grade phosphomolybdic acid was added to 100 mL of diethyl ether and stirred thoroughly. The molybdenum content in this solution was 100 mg / L. -1 In 0-10 o Store in refrigerator C; (2) Preparation of ternary cathode material sample: Ternary cathode material was prepared according to YS / T1006.2-2014 standard. 0.20 g of the obtained solid material was accurately weighed and placed in a 100 mL polytetrafluoroethylene beaker. 20 mL of 36% concentrated hydrochloric acid was added to dissolve the material. After cooling, the solution was diluted to 200 mL in a volumetric flask and immediately transferred to a plastic reagent bottle for later use. This is the original sample solution. (3) Determination of aluminum and molybdenum in the original sample solution: Calculate the required amount of molybdenum-containing solution based on the molybdenum ion concentration of the original sample obtained in step (2); ensure that the amount of molybdenum added is the same as the amount of molybdenum contained in the original sample; use a micropipette to extract the required amount of molybdenum-containing organic solution obtained in step (1) and place it in a 10 mL plastic centrifuge tube, and hold the tube wall for 1-2 minutes to allow the ether in it to evaporate; then extract 10 mL of the original sample solution obtained in step (2), add it to the plastic centrifuge tube, and shake it repeatedly for 2 minutes to redisperse the phosphomolybdic acid in the original sample solution to obtain the molybdenum-doped solution sample; (4) Determination of aluminum and molybdenum in the original sample solution and the molybdenum-doped sample solution: 1) Determination of aluminum and molybdenum in the original sample: The ICP equipment was set to perform five consecutive measurements and the average value and average deviation d were calculated. The concentrations of aluminum and molybdenum in the original sample were determined by the standard curve method as described in YS / T1006.2-2014. The wavelength used for aluminum was 396.153 nm, and the wavelength used for molybdenum was 204.598 nm. The preparation of the molybdenum standard solution was in accordance with GB / T20975.25-2020. 2) Preparation of molybdenum-doped samples: Calculate the required amount of molybdenum-containing solution based on the molybdenum ion concentration of the original sample obtained in step (3) 1), so that the amount of molybdenum added is the same as the amount of molybdenum contained in the original sample; use a micropipette to extract the required molybdenum-containing solution and place it in a 10 mL plastic centrifuge tube, and hold the tube wall for 1-2 minutes to allow the ether in it to evaporate; extract 10 mL of the original sample obtained in step (2), add it to the plastic centrifuge tube, and shake it repeatedly for 2 minutes to redisperse the phosphomolybdic acid in the sample to obtain the molybdenum-doped sample; The concentrations of aluminum and molybdenum in the molybdenum-doped sample were determined using the same method as in step (3) 1). (5) Aluminum ion concentration correction: The experimental data are attached. Figure 1 Plot the concentrations of the original solution and the molybdenum-doped solution on the graph with molybdenum content on the horizontal axis and aluminum content on the vertical axis. Draw boxes representing measurement errors outside the corresponding data points, intercept the corrected aluminum ion concentration on the vertical axis, and calculate the aluminum content in the ternary material.

[0020] The above embodiments are merely examples to clearly illustrate the present invention and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A method for correcting aluminum content in the elemental determination of molybdenum-containing lithium-ion battery cathode materials, wherein the cathode material is a ternary cathode material rod, characterized in that... Includes the following steps: (1) Prepare an organic solution by dispersing phosphomolybdic acid in an organic solvent; (2) Dissolve the ternary cathode material in hydrochloric acid solution to obtain the original solution; (3) Take the organic solution obtained in step (1) and evaporate it to dryness. Then, inject part of the original solution obtained in step (2) into it and shake it quickly to redisperse the phosphomolybdic acid in the new solution as a molybdenum-doped solution. (4) The original solution and the molybdenum-doped solution were determined by inductively coupled plasma (ICP) emission spectroscopy. The aluminum content was determined at 396.153 nm for Al (I) and the molybdenum content was determined at 204.598 nm for Mo (II). (5) Plot the concentrations of the original solution and the molybdenum-doped solution on the graph with the molybdenum content as the horizontal axis and the aluminum content as the vertical axis; draw boxes representing measurement error outside the data points, and obtain the corrected aluminum content on the vertical axis using a graphical method; The organic solvent used in step (1) is ethanol or diethyl ether.

2. The method for correcting aluminum content in the elemental determination of molybdenum-containing lithium-ion battery cathode materials according to claim 1, characterized in that, Follow these steps: (1) Preparation of molybdenum-containing solution: Add 15.9 mg of commercially available analytical grade phosphomolybdic acid to 100 mL of pre-dried ethanol and stir thoroughly. The molybdenum content in this molybdenum-containing solution is 100 mg / L. -1 Store in a refrigerator at 0-10℃; (2) Preparation of the original solution for the ternary cathode material sample: Ternary cathode material was prepared according to YS / T1006.2-2014 standard. 0.20 g of solid material was accurately weighed and placed in a 100 mL polytetrafluoroethylene beaker. 20 mL of 36% concentrated hydrochloric acid was added to dissolve the material. After cooling, the solution was diluted to 200 mL in a volumetric flask and immediately transferred to a plastic reagent bottle for later use. This is the original sample solution. (3) Preparation of molybdenum-doped samples: Take 0.1 mL of the molybdenum-containing organic solution obtained in step (1) with a micropipette and place it in a 10 mL plastic centrifuge tube. Leave it open for 30 min to allow the ethanol in the solution to evaporate. Then, take 10 mL of the original sample solution obtained in step (2) and add it to the plastic centrifuge tube. Shake repeatedly for 2 min to redisperse the phosphomolybdic acid in the sample to obtain the molybdenum-doped solution sample. (4) Determination of aluminum and molybdenum elements in the original sample solution and the molybdenum-doped sample: The ICP equipment was set to perform 5 consecutive measurements and the average value and average deviation d were calculated. The concentrations of aluminum ions and molybdenum ions in the original sample and the molybdenum-doped sample were determined by standard curve method according to the method described in YS / T1006.2-2014. The wavelength used for aluminum was 396.153 nm; the wavelength used for molybdenum was 204.598 nm. The preparation of molybdenum standard solution was carried out in accordance with GB / T 20975.25-2020. (5) Aluminum ion concentration correction: Plot the measured concentrations of the original sample solution and the molybdenum-doped sample solution in Figure 1, with the molybdenum content as the horizontal axis and the aluminum content as the vertical axis; draw boxes representing the measurement experiment error outside the corresponding data points, and obtain the corrected aluminum content on the vertical axis through graphical method; intercept the corrected aluminum ion concentration on the vertical axis, and calculate the aluminum content in the ternary cathode material.

3. The method for correcting aluminum content in the elemental determination of molybdenum-containing lithium-ion battery cathode materials according to claim 1, characterized in that, Follow these steps: (1) Preparation of molybdenum-containing solution: 15.9 mg of commercially available analytical grade phosphomolybdic acid was added to 100 mL of diethyl ether and stirred thoroughly. The molybdenum content in this solution was 100 mg / L. -1 Store in a refrigerator at 0-10℃; (2) Preparation of ternary cathode material sample: Ternary cathode material was prepared according to YS / T1006.2-2014 standard. 0.20 g of the obtained solid material was accurately weighed and placed in a 100 mL polytetrafluoroethylene beaker. 20 mL of 36% concentrated hydrochloric acid was added to dissolve the material. After cooling, the solution was diluted to 200 mL in a volumetric flask and immediately transferred to a plastic reagent bottle for later use. This is the original sample solution. (3) Determination of aluminum and molybdenum in the original sample solution: Calculate the required amount of molybdenum-containing solution based on the molybdenum ion concentration of the original sample obtained in step (2); ensure that the amount of molybdenum added is the same as the amount of molybdenum contained in the original sample; use a micropipette to extract the required amount of molybdenum-containing organic solution obtained in step (1) and place it in a 10 mL plastic centrifuge tube, and hold the tube wall for 1-2 minutes to allow the ether in it to evaporate; then extract 10 mL of the original sample solution obtained in step (2), add it to the plastic centrifuge tube, and shake it repeatedly for 2 minutes to redisperse the phosphomolybdic acid in the original sample solution to obtain the molybdenum-doped solution sample; (4) Determination of aluminum and molybdenum in the original sample solution and the molybdenum-doped sample solution: 1) Determination of aluminum and molybdenum in the original sample: The ICP equipment was set to perform five consecutive measurements and the average value and average deviation d were calculated. The concentrations of aluminum and molybdenum in the original sample were determined by the standard curve method as described in YS / T1006.2-2014. The wavelength used for aluminum was 396.153 nm, and the wavelength used for molybdenum was 204.598 nm. The preparation of the molybdenum standard solution was in accordance with GB / T 20975.25-2020. 2) Preparation of molybdenum-doped samples: Calculate the required amount of molybdenum-containing solution based on the molybdenum ion concentration of the original sample obtained in step (4) 1), so that the amount of molybdenum added is the same as the amount of molybdenum contained in the original sample; use a micropipette to extract the required molybdenum-containing solution and place it in a 10 mL plastic centrifuge tube, and hold the tube wall for 1-2 minutes to allow the ether in it to evaporate; extract 10 mL of the original sample obtained in step (2), add it to the plastic centrifuge tube, and shake it repeatedly for 2 minutes to redisperse the phosphomolybdic acid in the sample to obtain the molybdenum-doped sample; The concentrations of aluminum and molybdenum in the molybdenum-doped sample were determined using the same method as in step (4) 1). (5) Aluminum ion concentration correction: The experimental data were plotted, with the molybdenum content on the horizontal axis and the aluminum content on the vertical axis, showing the concentrations of the original solution and the molybdenum-doped solution. Boxes representing measurement errors were drawn outside the corresponding data points, and the corrected aluminum ion concentration was intercepted on the vertical axis. The aluminum content in the ternary cathode material was then calculated.

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