Method for testing homogeneity of main elements in a material

Abstract

This application belongs to the field of analytical testing, specifically relating to a method for testing the homogeneity of major elements in materials. The method includes: using an X-ray energy dispersive spectroscopy (EDS) instrument to determine the content of major elements in n particles of a sample under test. 主 Obtain a sample of principal element content data, where n is not less than 10000; plot the measured data into a two-dimensional triangular scatter plot and calculate the area of ​​the scatter plot as S. EDS The content of major elements in the sample was determined by inductively coupled plasma atomic emission spectrometry (ICP). 主 If |EDS 主 -ICP 主 |<2% and S EDS If |EDS < 64, the sample elemental distribution is uniform; if |EDS 主 -ICP 主 |<2% and 64 EDS If |EDS <100, the elemental distribution of the sample is relatively uneven; if |EDS 主 -ICP 主 |<2% and S EDS If the value is greater than 100, the elemental distribution in the sample is severely uneven. This method offers high accuracy, short cycle time, high efficiency, and low cost.​

Description

Technical Field

[0001] This application belongs to the field of analytical testing, specifically relating to a method for testing the uniformity of principal elements in materials. Background Technology

[0002] Current methods for evaluating the uniformity of ternary oxide precursors mainly rely on inductively coupled plasma optical emission spectroscopy (ICP-OES / MS). This involves completely dissolving the precursor sample and measuring the total concentration and proportion of the main elements in the solution. The macroscopic uniformity is determined by a relative deviation of ≤±2% between the measured and designed proportions (an industry standard, i.e., |(measured proportion - designed proportion) / design proportion| × 100% ≤ 2%). However, this method only reflects the overall consistency of the precursor solution preparation and synthesis process and cannot accurately characterize the distribution of main elements within and between individual particles. Therefore, it is insufficient to meet the evaluation requirements for the microscopic uniformity of precursors prepared by pyrolysis spraying. Thus, methods for testing the uniformity of main elements in materials need further improvement. Summary of the Invention

[0003] This application aims to at least partially address one of the technical problems in related technologies. To this end, this application proposes a testing method for the homogeneity of main elements in materials, characterized by high testing accuracy, short cycle time, high efficiency, or low cost.

[0004] A first aspect of this application proposes a method for testing the homogeneity of principal elements in a material, comprising: The content of major elements in n particles of a sample was determined using an X-ray energy dispersive spectroscopy (EDS) instrument. 主 Obtain a sample of principal element content data, where n is not less than 10000; A two-dimensional triangular scatter plot is drawn based on the principal element content data sample, and the area S of the scatter plot is calculated. EDS ; The main element content of the sample was determined by inductively coupled plasma atomic emission spectrometry (ICP-AES). 主 ; If |EDS 主 -ICP 主 |<2% and S EDS If the value is less than 64, then the principal element is uniformly distributed; if |EDS| is satisfied... 主 -ICP 主 |<2% and 64≤S EDS If |EDS| < 100, then the distribution of the principal elements is relatively uneven; if |EDS| < 100, then the distribution of the principal elements is relatively uneven. 主 -ICP 主 |<2% and S EDS If the value is greater than 100, then the distribution of the principal elements is severely uneven.

[0005] This application accurately evaluates the microscopic uniformity of the test material by analyzing the test data of each particle, with high detection accuracy, which can effectively control product quality and precisely optimize the production process. In addition, the method has the advantages of short test cycle and high analysis efficiency, which can significantly reduce quality control costs, and it is universally applicable to samples obtained by various preparation methods.

[0006] According to embodiments of this application, the main element content (EDS) of n particles in a sample is measured using an X-ray energy dispersive spectroscopy (EDS) instrument. 主 include: The sample to be tested is dispersed in a solvent and subjected to ultrasonic treatment to obtain a sample dispersion. Take the supernatant of the sample dispersion, add 1 to 5 drops onto the stage, blow dry, and obtain the electron microscope sample; The electron microscope sample was observed using a scanning electron microscope, and the main element content (EDS) of n particles in the electron microscope field of view was tested using an X-ray energy dispersive spectroscopy (EDS) instrument to obtain the total elemental content (EDS) of the n particles. 主 .

[0007] According to an embodiment of this application, the ultrasonic treatment satisfies at least one of the following conditions: The ultrasonic power of the ultrasonic treatment is 100W-250W; The ultrasonic treatment time is 3 min to 15 min.

[0008] According to an embodiment of this application, the main element content (EDS) of n particles in a sample is measured using an X-ray energy dispersive spectrometer. 主 At least one of the following conditions must be met: The scanning electron microscope has a magnification of 100x-1000x, preferably 100x-500x; The particle collection count rate is greater than 500,000.

[0009] According to embodiments of this application, the electron microscope sample satisfies at least one of the following conditions: The sample particles to be tested meet the following requirements: the aggregate particle size is 1 to 3 times the size of a single particle. Within a single field of view of the electron microscope, the particle coverage of the sample under test is 30% to 50%.

[0010] According to an embodiment of this application, the sample to be tested includes a nickel-cobalt-manganese ternary material precursor, and the main elements include nickel, cobalt, and manganese.

[0011] According to embodiments of this application, the preparation method of the nickel-cobalt-manganese ternary material precursor includes at least one of the following: pyrolysis spray method and co-precipitation method. Attached Figure Description

[0012] Figure 1 This is a two-dimensional triangular scatter plot of the main element content in Embodiment 1 of this application.

[0013] Figure 2 This is a two-dimensional triangular scatter plot of the main element content in Embodiment 2 of this application. Detailed Implementation

[0014] The embodiments of this application are described in detail below, with examples of these embodiments illustrated in the accompanying drawings. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain this application, and should not be construed as limiting this application.

[0015] Currently, the pyrolysis spray process suffers from uneven metal salt concentrations within the atomized droplets and a mismatch between the drying and decomposition rates during pyrolysis. This results in the final particles not being uniformly distributed according to the designed proportions of metal elements, leading to uneven distribution of the main element content (Ni / Co / Mn) in the pyrolysis spray method. This can easily cause localized elemental inhomogeneities during the resynthesis of cathode materials. Currently, elemental uniformity in the pyrolysis spray method is analyzed using inductively coupled plasma optical emission spectrometry (ICP-OES / MS). The specific method is as follows: after completely dissolving the precursor sample, the total concentration and proportion of Ni, Co, and Mn in the solution are directly measured. Evaluation criteria: the relative deviation between the measured elemental proportions and the designed proportions should be ≤±2% (a common industry requirement). The smaller the deviation, the better the macroscopic uniformity, directly reflecting the overall consistency of the precursor solution preparation and atomization. However, this method is a macroscopic uniformity evaluation and cannot analyze the actual situation of each particle in the pyrolysis spray sample, resulting in low accuracy.

[0016] Based on the above, this application achieves synergistic characterization of sample microstructure and composition by comprehensively analyzing ICP and EDS data of major elements in a large number of test materials, and combining two-dimensional triangular scatter plots drawn from major element content data samples with quantitative calculation of the area of ​​the scatter plots. By analyzing test data for each particle, the microscopic uniformity of the test material can be accurately evaluated. The detection accuracy is high, which can effectively control product quality in the production process and accurately optimize the production process. In addition, this method has the advantages of short testing cycle and high analysis efficiency, which can significantly reduce quality control costs, and it is universally applicable to samples obtained by various preparation methods.

[0017] In view of this, this application proposes a method for testing the homogeneity of principal elements in a material, comprising: S10: Using X-ray energy dispersive spectroscopy (EDS) to determine the main element content of n particles in the sample. 主 To obtain a sample of main element content data, n is not less than 10000.

[0018] This step selects a sufficient amount of particles as test samples. By accumulating rich data on the content of major elements, it effectively reduces statistical random errors and ensures the reliability of the test results.

[0019] Furthermore, scanning electron microscopy (SEM) is often equipped with energy dispersive X-ray spectroscopy (EDS) as a coupled analytical accessory, forming a collaborative testing system of "morphological observation-elemental analysis": During the test, EDS can use the electron beam of SEM to excite the sample to generate characteristic X-rays, while simultaneously using the secondary electron / backscattered electron imaging function of SEM to observe the microscopic morphology of the sample in real time (such as particle morphology, agglomeration state, and microscopic defects), and precisely locate the analytical area of ​​EDS (such as specific particles, particle localities, or interface regions). Scanning electron microscopy (SEM) uses a focused high-energy electron beam on the surface of the sample to form extremely high-resolution images by detecting various signals generated by the interaction of electrons with matter (such as secondary electrons and backscattered electrons). This step has the following two functions: (1) Morphological observation: In this step, the micromorphology, particle size and aggregation state of the sample under high magnification SEM image can be clearly observed.

[0020] (2) Component Confirmation (EDS): To ensure the accuracy of the observed target, the elemental composition was qualitatively analyzed using the X-ray energy dispersive spectroscopy (EDS) instrument equipped with the SEM. Point analysis or area scanning was performed on suspected particles, and the main elemental composition of the particles was confirmed through their characteristic X-ray spectral lines.

[0021] According to embodiments of this application, the main element content (EDS) of n particles in a sample is measured using an X-ray energy dispersive spectroscopy (EDS) instrument. 主 The process includes: dispersing the sample to be tested in a solvent (including but not limited to ethanol) and sonicating it to obtain a sample dispersion; taking the supernatant from the sample dispersion, adding 1 to 5 drops onto the stage, and drying it to obtain an electron microscopy sample; observing the electron microscopy sample using a scanning electron microscope, and testing n particles in the electron microscope field of view using an X-ray energy dispersive spectroscopy (EDS) instrument to obtain the main element content (EDS) of the n particles. 主 This step, through a pretreatment process of dispersion-ultrasonication-drying, effectively breaks up particle agglomerations, ensuring that the test particles are independently dispersed single particles, thus avoiding interference from agglomerates and impurities on the detection signal. Combined with the intuitive observation of scanning electron microscopy and the precise testing of X-ray energy dispersive spectroscopy, the main element content data of the sample can be obtained efficiently, with high detection accuracy and good repeatability.

[0022] According to embodiments of this application, ultrasonic processing includes ultrasonic treatment at a power of 100W-250W (specifically, 100W, 150W, 200W, 250W or any range thereof) for 3-15 minutes (specifically, 3 minutes, 5 minutes, 7 minutes, 9 minutes, 11 minutes, 13 minutes, 15 minutes or any range thereof). Under these conditions, particle agglomerates can be efficiently broken up, allowing particles to disperse independently, avoiding overlapping interference, and ensuring the accuracy of single-particle element detection.

[0023] According to embodiments of this application, the sample particles to be tested satisfy the following condition: the aggregate particle size is 1 to 3 times the size of a single particle, specifically 1, 1.5, 2, 2.5, 3 times, or any combination thereof. This ensures that the sample particles are dispersed to a state where multiple particles do not stack or overlap, guaranteeing the authenticity and independence of single-particle elemental detection data, and preventing aggregates from obscuring the true morphology of the particles (such as sphericity and surface roughness), thus laying the foundation for accurate evaluation of microscopic uniformity.

[0024] According to embodiments of this application, within a single field of view of the electron microscope, the particle coverage of the sample under test is 30% to 50%, specifically 30%, 35%, 40%, 45%, 50%, or any range between two of these. The particles are not locally densely packed, ensuring that each particle is imaged independently, facilitating statistical analysis of particle size distribution.

[0025] Among them, the particle coverage of the sample to be tested refers to the percentage of the area occupied by all the particles to be tested in the field of view imaging area under the set electron microscope observation parameters (accelerating voltage, magnification, working distance, etc.), that is, the percentage of the total particle projection area to the effective imaging area of ​​a single field of view.

[0026] According to embodiments of this application, the dispersion process does not introduce impurities (such as dispersant residues or grinding media debris), thus avoiding impurities from obscuring particle details or being misidentified as particles.

[0027] According to an embodiment of this application, the main element content (EDS) of n particles was measured. 主 The next step includes removing obviously abnormal data, which refers to particles whose size is significantly larger than the sample being tested, typically large particles introduced during sample preparation. Removing abnormal data eliminates distorted data caused by detection errors, improving the accuracy and reliability of elemental homogeneity analysis results.

[0028] According to the embodiments of this application, the proportion of the number of particles corresponding to abnormal data to n particles is ≤0.2%, which can avoid the interference of abnormal data on the overall statistical results and ensure that the remaining valid data can truly reflect the microscopic uniformity of the sample to be tested.

[0029] As a specific example, this step includes: The principle of backscattered electron (BSE) imaging in scanning electron microscopy (SEM) is as follows: when an electron beam bombards a sample, the higher the atomic number of the sample, the stronger the backscattered electron signal, and the higher the image gray value; conversely, the lower the atomic number, the lower the image gray value. Based on this characteristic, samples are often distinguished according to different gray values ​​in backscattered electron imaging, followed by morphological and elemental content analysis of the particles. The gray value range is determined using aluminum foil and copper foil. In image processing, pixel values ​​typically represent brightness or color intensity, ranging from 0 to 255. This is because in an 8-bit grayscale image, each pixel is represented by one byte (8 bits), resulting in 256 possible values ​​(0 to 255). 0 represents black, 255 represents white, and intermediate values ​​represent different gray levels. The gray value range of the sample to be tested falls between that of aluminum foil and copper foil; adjustments are made to determine the final gray value range. Using standard samples, the energy resolution of the half-wavelength of Mn-Ka measured in-situ should be better than 127 eV; the energy resolution of the half-wavelength of F-Ka measured in-situ should be better than 64 eV; and the energy resolution of the half-wavelength of C-Ka measured in-situ should be better than 56 eV. The prepared test samples are then transferred to a scanning electron microscope (SEM) and imaged using backscatter mode. The recommended test voltage is 10 kV–30 kV, and the electron beam current range is 3 pA–20 nA.

[0030] Determine the grayscale value of the sample to be tested, identifying the brighter areas within the field of view, and import them into the energy dispersive spectroscopy (EDS) spectrometer for component analysis. The EDS spectrometer collects images of brighter particles at various magnifications from top to bottom and left to right. The collected particles are photographed, recorded, and imported into the content report.

[0031] According to embodiments of this application, the magnification of the scanning electron microscope is 100x-1000x, specifically 100x-500x, such as 100x, 200x, 300x, 400x, 500x, 600x, 700x, 800x, 900x, 1000x, or any range between two of these. Within this range, particle morphology and dispersion state can be clearly captured, improving the accuracy of the testing process.

[0032] According to embodiments of this application, the particle counting rate is greater than 500,000 counts. More abundant particle characteristic data can be acquired per unit time, which helps improve the accuracy of the testing process.

[0033] S20: Draw a two-dimensional triangular scatter plot based on the principal element content data sample, and calculate the area S of the scatter plot. EDS .

[0034] In this step, the EDS of the n particles obtained from the test are... 主The data was plotted as a two-dimensional triangular scatter plot, with each side corresponding to the content distribution of the two elements at each vertex. The element content distribution can be effectively evaluated by calculating the area enclosed by the scatter points within the triangular plot. The scatter area is calculated as follows: The maximum and minimum values ​​of two elements are selected, and parallel lines are drawn corresponding to the directions of those elements, resulting in a parallelogram region enclosed by four lines. The area S of this region is then calculated. EDS Used to evaluate the distribution of elements. Specifically, the smaller the area, the smaller the difference in the content of the main element between different particles, and the more uniform the distribution; the larger the area, the higher the dispersion of the main element content, and the more uneven the distribution.

[0035] S30: The main element content of the sample to be tested was determined by inductively coupled plasma atomic emission spectrometry (ICP). 主 .

[0036] In this step, the sample to be tested is pretreated and then subjected to ICP testing.

[0037] According to an embodiment of this application, the pretreatment includes: drying the sample to be tested using a forced-air drying oven or a vacuum drying oven at 100℃-150℃ (specifically, 100℃, 110℃, 120℃, 130℃, 140℃, 150℃ or any two thereof) for 1.5h-2h (specifically, 1.5h, 1.6h, 1.7h, 1.8h, 1.9h, 2.0h or any two thereof). This removes moisture and volatile impurities, preventing them from affecting the sample digestion efficiency and the accuracy of elemental content detection results.

[0038] According to an embodiment of this application, this step further includes: sieving the dried sample, typically using a 300-500 mesh standard sieve, selecting 5g-10g of the sieve-passing material; and performing ICP testing on a portion of this material 5 times to calculate the average value of the main content and the relative standard deviation. The main purpose is to break up agglomerated particles and ensure uniform sample dispersion.

[0039] S40: If |EDS is satisfied 主 -ICP 主 |<2% and S EDS If the value is less than 64, then the principal element is uniformly distributed; if |EDS| is satisfied... 主 -ICP 主 |<2% and 64≤S EDS If |EDS| < 100, then the distribution of the principal elements is relatively uneven; if |EDS| < 100, then the distribution of the principal elements is relatively uneven. 主 -ICP 主 |<2% and S EDS If the value is greater than 100, then the distribution of the principal elements is severely uneven.

[0040] Statistical analysis was performed on the above test results, ICP主 EDS reflects the average content of major elements in the overall macroscopic sample. 主 The content of major elements in the micro-area of ​​a single particle is reflected by EDS. A deviation of less than 2% between the two indicates that EDS... 主 The data is reliable and representative. Based on this data reliability, the dispersion of principal element content among all particles is quantified using the area distribution of a two-dimensional triangular scatter plot (SEDS). EDS The smaller the value, the more concentrated the content of the main elements in different particles, and the more uniform the overall distribution; S EDS The larger the value, the more drastic the fluctuation in particle content and the more disordered the distribution.

[0041] If the statistical results satisfy "|EDS" 主 -ICP 主 |<2% and S EDS If the criterion "<64" is met, it indicates that the distribution of the main element among individual particles in the sample is highly concentrated and lowly dispersed, meaning the main element is uniformly distributed; if the criterion "|EDS" is met, it indicates that the main element is uniformly distributed. 主 -ICP 主 |<2% and 64≤S EDS The condition ≤100 indicates that the content of the main element fluctuates among individual particles, and the dispersion is at a moderate level, meaning that the distribution of the main element is relatively uneven; if the condition ≤100 is met, it indicates that the content of the main element fluctuates among individual particles, and the dispersion is at a moderate level, meaning that the distribution of the main element is relatively uneven. 主 -ICP 主 |<2% and S EDS A value >100 indicates that the main element has significant fluctuations in content or local enrichment / deficiency among particles, meaning that the distribution of the main element is severely uneven.

[0042] According to an embodiment of this application, the testing method further includes: obtaining the particle size of the sample to be tested based on the scanning electron microscope image of the electron microscope sample, and calculating and analyzing the maximum, minimum, average, average deviation and relative standard deviation of the main elements in the sample to be tested.

[0043] The particle size in this application is obtained statistically based on the equivalent circle diameter (ECD) data of particles measured by scanning electron microscopy (SEM). The specific operation includes: identifying the particle outline using image analysis software, and converting the projected pixel area to the actual area (usually in μm²) using a scale. This parameter uniformly transforms irregularly shaped particles into the diameter of a spherical particle with an equivalent projection effect. The diameter of a circle with the same projected area as the target particle is calculated. The calculation formula is: Where Ai is the actual area of ​​the particle after scale conversion (usually in μm²), di is the diameter of the equivalent circle, π is pi, and the size distribution range of the sample to be tested is statistically analyzed.

[0044] This application uses n=10000 as an example for illustration: Maximum value (Max): The highest content of the main element in a single particle; Minimum value (Min): The lowest content of the main element in a single particle; average value( ): = (xi is the element content of the i-th particle) Mean deviation (MD): MD= It is used to quantify the overall deviation of the main element content of all particles in the sample from the average value, reflecting the central tendency of the main element distribution.

[0045] Relative Standard Deviation (RSD): RSD = / s ×100% reflects the degree of dispersion of the principal element distribution.

[0046] The formula for calculating the standard deviation (s) is as follows: .

[0047] According to an embodiment of this application, the testing method further includes: based on the main element content data sample and the main element content ICP... 主 The percentage of segregated particles is calculated, whereby segregated particles are those that satisfy |EDS 主 -ICP 主 |>3% of particles.

[0048] In this paper, "segregation" refers to the phenomenon where the content of major elements in some individual particles of the sample deviates significantly from the average content of major elements in the entire sample. The quantitative criterion is: the content of major elements in individual particles obtained by the EDS test described above (EDS). 主 The average content of major elements in the sample as characterized by ICP testing 主 Satisfy | EDS 主 -ICP 主 When the content of a single particle exceeds 3%, it is considered a segregated particle. Essentially, the elemental content at the single particle level deviates from the average macroscopic level of the sample beyond the acceptable range, reflecting the local enrichment or deficiency of elements at the microscopic scale.

[0049] According to an embodiment of this application, the main element includes at least two elements. If the proportion of segregated particles of a single element is ≤1% and the proportion of segregated particles of all the main elements is ≤2%, then the main element is uniformly distributed; otherwise, the main element is unevenly distributed.

[0050] For test samples containing at least two main elements, this application employs a dual segregation criterion of "single element + overall main element" to comprehensively ensure the uniformity of main element distribution: on the one hand, the proportion of segregated particles of each single element is limited to ≤1%, ensuring that the independent function of each main element is not affected by local segregation; on the other hand, the proportion of overall segregated particles of all main elements is limited to ≤2% (i.e., particles segregated by any main element are included in the overall statistics), avoiding the disruption of synergistic effects by multi-element cross-segregation. Only when both conditions are met simultaneously can the uniformity of main element distribution be determined; failure to meet either condition indicates a risk of local failure of a single element or imbalance of multi-element synergy, resulting in an uneven distribution of main elements.

[0051] According to an embodiment of this application, the principal element includes three types of elements, and the testing method further includes: grouping particles according to element proportions using the K-means clustering algorithm; if only one principal cluster appears, the principal element is evenly distributed; otherwise, the principal element is unevenly distributed. The principal cluster refers to a cluster in which the particle proportion is ≥95%.

[0052] For test samples containing three main elements, this application can also use the K-means clustering algorithm to determine the uniformity of element proportions: if only one main cluster appears in the clustering results (i.e., the number of particles contained in this cluster accounts for ≥95% of the total number of n test particles), it indicates that the proportion of the three main elements in more than 95% of the particles is highly concentrated, and the distribution of main elements is determined to be uniform; if multiple main clusters appear or no cluster accounts for ≥95%, it indicates that there is a significant differentiation in the element proportions among the particles, and the uniformity is low, and the distribution of main elements is determined to be uneven.

[0053] K-means clustering is an unsupervised learning algorithm that automatically groups data based on similarity. It can group particles with similar proportions into the same cluster according to the proportions of the three principal elements of each particle (such as atomic ratio and mass ratio), thereby minimizing the difference in element proportions within the same cluster and maximizing the difference between different clusters.

[0054] According to an embodiment of this application, the principal element includes three elements, and the testing method further includes: drawing a three-dimensional scatter plot based on the principal element content data sample, wherein each coordinate axis in the three-dimensional scatter plot corresponds to a principal element.

[0055] For test samples containing three main elements, this application can further analyze the uniformity of elemental distribution by plotting a three-dimensional scatter plot. During the analysis, the content of the three main elements in the material needs to be normalized, specifically limiting the sum of the mole fractions of the three main elements in a single particle to 1. Using the three main elements as the X, Y, and Z axes of a three-dimensional coordinate system, each axis value corresponds to the content of that element in a single particle (e.g., atomic percentage at%). Each test particle corresponds to a data point in three-dimensional space based on its three main element content data, forming a three-dimensional scatter plot containing n valid data points. If the main elements are uniformly distributed, the elemental proportions of all particles will be consistent around the target proportion, and the data points in the scatter plot will exhibit dense clustering characteristics. If the main elements are unevenly distributed, the elemental proportions between particles will differ significantly, and the data points will be scattered in space, forming multiple discrete clusters, or exhibiting outliers deviating from the target area.

[0056] According to an embodiment of this application, the sample to be tested includes a nickel-cobalt-manganese ternary material precursor, and the main elements include nickel, cobalt, and manganese.

[0057] It is understood that this application does not impose specific restrictions on the preparation method of the test material, as long as the above-mentioned preparation method of the ternary precursor can be obtained.

[0058] As a specific example, the preparation methods for nickel-cobalt-manganese ternary material precursors include at least one of spray pyrolysis and co-precipitation methods. The testing methods in this application are universally applicable to different preparation systems.

[0059] As an example, the spray pyrolysis method includes: preparing a salt solution (usually chloride) of nickel, cobalt, and manganese according to a certain design ratio; evaporating the solvent by spray drying to precipitate the solute and form nickel, cobalt, and manganese oxide particles; and collecting the particles after particle size classification to obtain the nickel, cobalt, and manganese ternary material precursor.

[0060] As an example, the coprecipitation method involves preparing a nickel-cobalt-manganese salt solution (usually sulfate) according to a certain design ratio, adding an alkali such as ammonia to a liquid-phase reactor to form a nickel-cobalt-manganese hydroxide precipitate, and then performing solid-liquid separation to obtain the nickel-cobalt-manganese ternary material precursor.

[0061] The embodiments of this application are described in detail below.

[0062] Example 1 (1) ICP testing The Ni, Co, Mn ternary oxide precursors prepared by spray pyrolysis were dried in a forced-air oven at 100℃ for 2 hours.

[0063] The dried sample was sieved through a 400-mesh standard sieve, and 10g of the material passed through the sieve was collected. A portion of this material was tested five times using ICP, and the average value of the main content was calculated. The relative standard deviation (RSD) is calculated by taking the average values ​​of the Ni content data samples, Co content data samples, and Mn content data samples, respectively. Ni , Co , Mn and relative standard deviation (RSD) Ni RSD Co RSD Mn Based on the above average value Ni , Co , Mn Calculate the mean deviation MD Ni MD Co MD Mn .

[0064] (2) Testing EDS Weigh 0.02g of the oxide precursor sample and disperse it in 10ml of ethanol. Sonicate at 200W for 5 minutes. Select the supernatant (avoiding undispersed agglomerates), add 1-5 drops onto the conductive adhesive, and dry with a syringe. The grayscale values ​​acquired by this SEM are between 120-150. Using standard samples, the half-wavelength of Mn-Ka was measured in-situ, and the calculated energy resolution should be better than 127eV; the half-wavelength of F-Ka was measured in-situ, and the calculated energy resolution should be better than 64eV; the half-wavelength of C-Ka was measured in-situ, and the calculated energy resolution should be better than 56eV. Transfer the processed test samples to the SEM and image using backscatter mode; the test voltage is 20kV, and the electron beam current is 6.4 nA.

[0065] Determine the grayscale value (120-150) of the oxide precursor, identifying areas with higher brightness within the field of view, and import them into an energy dispersive spectroscopy (EDS) spectrometer for component analysis. The aggregate particle size of the oxide precursor should be ≤1.5 times the single particle size; the particle coverage of the oxide precursor within a single field of view under an electron microscope should be 30%–50%. The EDS spectrometer should collect high-brightness particles at equal magnifications from top to bottom and left to right, photographing and recording the nickel-cobalt-manganese-oxygen (NiCoMnO) particles, and importing the results into a content report (exporting 10,000 particles). A magnification of 500x is preferred; the particle count rate should be greater than 500,000 counts.

[0066] SEM was used to determine the particle images of the oxide precursor, and image analysis software was used to identify the particle outlines. The projected pixel area is the actual area (usually in μm²) after scale conversion. This parameter unifies irregularly shaped particles into the diameter of a spherical particle with an equivalent projection effect. The diameter of the circle with the same projected area as the target particle is calculated. The calculation formula is: Where Ai is the actual area of ​​the particle's projected pixel area after scale conversion (the unit is usually μm²), di is the diameter of the equivalent circle, and π is pi (value is 3.14). The size distribution and distribution range of the oxide precursor are statistically shown in Table 1.

[0067] (3) Perform statistical analysis of oxide precursor data. The contents (maximum, minimum, average, RSD) of each major element in the oxide precursor were calculated as atomic percentages (at%) of Ni, Co, and Mn, as shown in Table 2.

[0068] Calculate the percentage of segregated particles: Count the number of Ni, Co, and Mn segregated particles respectively, and calculate their respective percentages (number of segregated particles / 10000 × 100%), as shown in Table 3. Creating a 2D triangular scatter plot: Using plotting software, a 2D triangular scatter plot is created, with each side corresponding to the content distribution of the two elements at each vertex. This visually displays the elemental distribution of 10,000 particles. Figure 1 As shown.

[0069]

[0070] Among them, classification / ECD (μm): the horizontal data is the interval division of the equivalent circle diameter (ECD) of the particles (unit: μm), and the vertical data is the interval classification of the molar content of Ni element in the particles, which is used to simultaneously characterize the distribution relationship between composition and size.

[0071] Ni 30-40 indicates that the Ni content is between 30 mol% and 40 mol%, Ni 40-50 indicates that the Ni content is between 40 mol% and 50 mol%, and so on. Ni 90-100 indicates that the Ni content is between 90 mol% and 100 mol%.

[0072] The equivalent circular diameter of a single ECD particle, measured in micrometers (μm), is calculated based on the two-dimensional projected area of ​​the particle observed by a scanning electron microscope (SEM), according to the aforementioned formula. The calculation yields a value used to quantify the actual size of a single particle, reflecting its morphological characteristics.

[0073]

[0074]

[0075] Note: Due to the large amount of sample data, only part of the data is given in Table 2.

[0076]

[0077]

[0078] Among them, "row label" refers to the grouping identifier based on "Ni mol% range", which represents the range of the molar percentage of Ni element in the micro-region of the precursor particles of the oxide to be tested (such as "Ni 30-40" means that the Ni content in the micro-region of the particles in this group is between 30mol% and 40mol%), and is used to statistically analyze the particle distribution characteristics of different Ni content ranges.

[0079] "Particle Count" corresponds to the effective statistical particle count (i.e., the number of particle micro-regions that meet the test conditions within the Ni content range shown in the "Row Label"), for example, the count for the "Ni 50-60" range is 1506, which means that a total of 1506 particle micro-regions with Ni molar content between 50% and 60% were detected.

[0080] "Particle percentage" corresponds to the proportion (percentage) of particles in the Ni content range shown in the "Row label" to the total number of particles, which is (count item in this range: category value / total number) × 100%. It is used to quantify the distribution percentage of particles in different Ni content ranges and reflect the overall distribution trend of elemental segregation (e.g., the "Ni 60-70" range accounts for 67.82%, which means that particles in this range are the main distribution type).

[0081] Conclusion: As shown in Table 3, in Example 1, ICP... 主 The average Ni content of the oxide precursor prepared by pyrolysis spray oxide was 62.66 mol%, the average Co content was 7.58 mol%, and the average Mn content was 29.76 mol%. As shown in Tables 2 and 3, the sample was tested with EDS... 主 With ICP 主 The difference is small; specifically, for Ni, |EDS 主 -ICP 主 |=|64.02%-62.66%|=1.36%; For Co element, |EDS 主 -ICP 主 |=|7.95%-7.58%|=0.37%; For the Mn element, |EDS 主 -ICP 主 |=|28.03%-29.76%|=1.73%, the primary element's |EDS 主 -ICP 主 All are less than 2%. Then combine Figure 1 In a 2D triangular scatter plot, the area of ​​the scatter points is distributed as a percentage. Calculate S. EDS It is 1215.19. (By...) Figure 1 It can be seen that the three-dimensional scatter plot of the main element distribution in the oxide precursor prepared by pyrolysis spray oxide is relatively wide. In summary, the elemental distribution of the oxide precursor prepared by pyrolysis spray oxide is severely uneven.

[0082] Furthermore, calculations were performed based on the data in Table 2. Ni , Co , Mn The average Ni content was 64.02 mol%, the average Co content was 7.95 mol%, and the average Mn content was 28.03 mol%; RSD Ni RSD Co RSD Mn The percentages were 8.9%, 17.5%, and 17.1%, respectively, with the highest Ni content being 96.11 mol%, a standard deviation of 5.72, and an RSD of 8.9%. Table 4 shows that the proportion of segregated particles of the main element was >30%. All of these data indicate that the elemental distribution of the oxide precursor prepared from the pyrolysis spray oxide is severely uneven.

[0083] Example 2 Same as Example 1, except that the hydroxide precursor was prepared by co-precipitation. Some test data are shown in Tables 5 and 6. Figure 2 .

[0084]

[0085] Among them, classification / ECD (μm): the horizontal data is the interval division of the equivalent circle diameter (ECD) of the particles (unit: μm), and the vertical data is the classification of Ni element in the particles between 60mol% and 70mol%, which is used to simultaneously characterize the distribution relationship between composition and size.

[0086]

[0087]

[0088]

[0089] Conclusion: As shown in Table 7, in Example 2, ICP... 主 The results showed that the average Ni content was 62.19 mol%, the average Co content was 7.41 mol%, and the average Mn content was 30.40 mol%.

[0090] As shown in Table 6, in Example 2, ICP 主The average particle size of the oxide precursor prepared by the pyrolysis spray method was 2.5 µm, with a maximum value of 9.85 µm and a minimum value of 0.91 µm. The calculated standard deviation was 0.57. Ni , Co , Mn The average Ni content was 63.51 mol%, the average Co content was 7.6 mol%, and the average Mn content was 28.89 mol%; RSD Ni RSD Co RSD Mn The percentages were 1.5%, 5.9%, and 3%, respectively, with the maximum Ni content being 70.51 mol%, the standard deviation being 0.93, and the RSD being 1.5%.

[0091] Depend on Figure 2 It can be seen that the elemental distribution of the ternary precursor of the coprecipitated hydroxide is relatively concentrated in the three-dimensional scatter plot. As shown in Tables 6 and 7, the EDS analysis of this sample... 主 With ICP 主 The differences are small, all less than 2%. Then, the area of ​​the scatter plot is calculated, with the scatter coordinates expressed as a percentage, and S is calculated. EDS The value is 58.65. In summary, the elemental distribution of the ternary hydroxide precursor prepared by the co-precipitation method is relatively uniform.

[0092] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0093] Although embodiments of this application have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting this application. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of this application.

Claims

1. A method for testing the uniformity of major elements in a material, characterized in that, include: The content of major elements in n particles of a sample was determined using an X-ray energy dispersive spectroscopy (EDS) instrument. 主 Obtain a sample of principal element content data, where n is not less than 10000; A two-dimensional triangular scatter plot is drawn based on the principal element content data sample, and the area S of the scatter plot is calculated. EDS ; The main element content of the sample was determined by inductively coupled plasma atomic emission spectrometry (ICP-AES). 主 ; If |EDS 主 -ICP 主 |<2% and S EDS If the value is less than 64, then the principal element is uniformly distributed; if |EDS| is satisfied... 主 -ICP 主 |<2% and 64≤S EDS If |EDS| < 100, then the distribution of the principal elements is relatively uneven; if |EDS| < 100, then the distribution of the principal elements is relatively uneven. 主 -ICP 主 |<2% and S EDS If the value is greater than 100, then the distribution of the principal element is severely uneven. Among them, S EDS The calculation is performed as follows: In the two-dimensional triangular scatter plot, the maximum and minimum values ​​of two principal elements are selected respectively. Parallel lines corresponding to the directions of these elements are drawn, resulting in a parallelogram region enclosed by four straight lines. The area of ​​this region, S, is then calculated. EDS .

2. The method according to claim 1, characterized in that, The content of major elements in n particles of a sample was determined using an X-ray energy dispersive spectroscopy (EDS) instrument. 主 include: The sample to be tested is dispersed in a solvent and subjected to ultrasonic treatment to obtain a sample dispersion. Take the supernatant of the sample dispersion, add 1 to 5 drops onto the stage, blow dry, and obtain the electron microscope sample; The electron microscope sample was observed using a scanning electron microscope, and the sample particles in the electron microscope field of view were tested using an X-ray energy dispersive spectroscopy (EDS) instrument to obtain the main element content (EDS) of n particles. 主， n must be greater than 10000.

3. The method according to claim 2, characterized in that, The ultrasonic treatment satisfies at least one of the following conditions: The ultrasonic power of the ultrasonic treatment is 100W-250W; The ultrasonic treatment time is 3 min to 15 min.

4. The method according to claim 2, characterized in that, The content of major elements in n particles of a sample was determined using an X-ray energy dispersive spectroscopy (EDS) instrument. 主 At least one of the following conditions must be met: The magnification of the scanning electron microscope is 100x-1000x; The particle collection count rate is greater than 500,000.

5. The method according to claim 4, characterized in that, The scanning electron microscope has a magnification of 100x to 500x.

6. The method according to claim 3, characterized in that, The electron microscope sample satisfies at least one of the following conditions: The sample particles to be tested meet the following requirements: the aggregate particle size is 1 to 3 times the size of a single particle; Within a single field of view of the electron microscope, the particle coverage of the sample under test is 30% to 50%.

7. The method according to any one of claims 1 to 6, characterized in that, The sample to be tested includes a nickel-cobalt-manganese ternary material precursor, and the main elements include nickel, cobalt, and manganese.

8. The method according to claim 7, characterized in that, The preparation method of the nickel-cobalt-manganese ternary material precursor includes at least one of the following: pyrolysis spray method and co-precipitation method.

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