Method and system for measuring lithium content in lithium-containing mixed material

Abstract

The invention relates to a method and system for measuring the lithium content in a lithium-containing mixed material, and the method comprises the following steps: sampling the lithium-containing mixed material to obtain a plurality of test samples; the color features of the test samples are converted into variable data in a color model, the color features comprise one or more of hue, brightness and color saturation, and the variable data are used for reflecting the lithium content in the multiple test samples. The determination method further comprises the following steps: analyzing whether the variable data of the plurality of test samples have differences or not, and judging whether the uniformity of the lithium-containing mixed material is qualified or not according to an analysis result. According to the determination method, the distribution information of the lithium content in the lithium-containing mixed material can be obtained without determining the specific lithium content, and the uniformity of the lithium-containing mixed material can be rapidly and accurately evaluated.

Description

Technical Field

[0001] The present application relates to the field of lithium-ion battery material detection, and in particular to a method and system for determining the lithium content in a lithium-containing mixed material. Background Art

[0002] As a widely used energy storage medium, lithium-ion batteries have a huge market demand, and the market's pursuit of lithium-ion battery performance is getting higher and higher. Each improvement in lithium-ion battery performance comes from the improvement in the performance of key materials. In the positive electrode material of nickel-cobalt-manganese oxide lithium compound, the local ratio of lithium, nickel, cobalt and manganese, such as the ratio of Li:Me (Me=Ni+Co+Mn), has a great influence on the electrochemical performance of the positive electrode material. Therefore, whether the mixing of ingredients is uniform becomes one of the keys affecting the performance of the positive electrode material.

[0003] The process of mixing lithium raw materials and precursors (metal hydroxides or oxides) in a certain proportion is called dry mixing. In order to ensure the uniformity of dry mixing, the industry currently mainly uses chemical titration or potentiometric titration to obtain the measured value of lithium, and the measured value is assumed to be uniform within the index range. However, this method has the disadvantages of long testing time, high cost and complicated pre-treatment process, and the sampling test volume is small at one time, which is not representative enough and is not conducive to the evaluation of the uniformity of the mixture. Although it can be evaluated through multiple tests, multiple tests are too time-consuming and not conducive to rapid detection. Summary of the invention

[0004] In view of this, the present application provides a method and system for determining the lithium content in a lithium-containing mixed material to solve at least one of the above-mentioned technical problems.

[0005] To achieve the above-mentioned objectives, in a first aspect, the present application provides a method for determining the lithium content in a lithium-containing mixed material, the determination method comprising: sampling the lithium-containing mixed material to obtain a plurality of test samples; converting the color characteristics of the test samples into variable data in a color model, the color characteristics comprising one or more of hue, brightness and color saturation, and the variable data being used to reflect the lithium content in the plurality of test samples.

[0006] In some possible implementations, the above-mentioned determination method further includes: analyzing whether there are differences in the variable data of multiple test samples, and judging whether the uniformity of the lithium-containing mixed material is qualified based on the analysis results.

[0007] In some possible implementations, the color feature includes brightness, and converting the brightness of the lithium-containing mixed material into variable data in the color model includes: providing an illumination light source; obtaining tristimulus values ​​of the lithium-containing mixed material under the illumination light source; and converting the tristimulus values ​​into brightness variables in the color model.

[0008] In some possible implementations, obtaining tristimulus values ​​of the lithium-containing mixed material under an illumination source includes: collecting, through a sensor, a spectrum reflected by the lithium-containing mixed material under the illumination source at a preset viewing angle; obtaining tristimulus values ​​of the lithium-containing mixed material under the illumination source according to a color matching function; and converting the tristimulus values ​​into brightness variables in a color model.

[0009] In some possible implementations, the preset viewing angle includes one or both of 1° to 4° and greater than 4°.

[0010] In some possible implementations, the illumination light source includes a standard light source and a fluorescent light source, and the correlated color temperature of the standard light source is 2856K to 6504K.

[0011] In some possible implementations, the standard light source includes one of the standard light source D65, the standard light source C, and the standard light source A.

[0012] In some possible implementations, the lithium-containing mixed material includes a dry-mixed material of a lithium source and a metal hydroxide, or a dry-mixed material of a lithium source and a metal oxide.

[0013] In some possible implementations, before converting the color features of the lithium-containing mixed material into variable data in a color model, the method further includes: placing the lithium-containing mixed material in a container, wherein the ratio of the height of the lithium-containing mixed material to the height of the container is 2 / 3-3 / 4; and compacting the lithium-containing mixed material.

[0014] The present application finds that the distribution of lithium in the lithium-containing mixed material has a significant effect on the color characteristics inside the lithium-containing mixed material. Therefore, the above-mentioned method for determining the lithium content in the lithium-containing mixed material converts the color characteristics of multiple test samples in the lithium-containing mixed material into variable data, and the variable data of the color characteristics can better reflect the lithium content in the test sample, thereby reflecting the distribution information of the lithium content in different test samples according to the variable data of different test samples. In this way, the distribution information of the lithium content inside the lithium-containing mixed material can be obtained without measuring the specific content of lithium. Further, by whether there is a difference in the variable data between multiple test positions in the lithium-containing mixed material, the specific content of lithium can be determined without measuring the specific content of lithium, and the uniformity of the lithium-containing mixed material can be quickly and accurately evaluated. The present application also finds that the distribution of lithium in the lithium-containing mixed material has a more obvious effect on the brightness inside the lithium-containing mixed material. Obtaining the brightness of the test sample through specific light source conditions, tristimulus values ​​and a color model with brightness variables can more accurately map the lithium content in the test sample, thereby more accurately evaluating the uniformity of the lithium-containing mixed material.

[0015] In a second aspect, the present application provides a system for determining the lithium content in a lithium-containing mixed material, the determination system comprising a testing device, the testing device being used to convert the color characteristics of the lithium-containing mixed material into variable data in a color model, the color characteristics comprising one or more of hue, brightness and color saturation, the variable data being used to reflect the lithium content in a plurality of test samples.

[0016] In some possible implementations, the above-mentioned measurement system also includes a processor, and the processor is used to analyze whether there are differences in the variable data of multiple test samples, and determine whether the uniformity of the lithium-containing mixed material is qualified based on the analysis results. DETAILED DESCRIPTION

[0017] The embodiments of the present application are described in detail below. The embodiments described below are exemplary and are only used to explain the present application, and cannot be understood as limiting the present application; it should be noted that, unless otherwise defined, all technical and scientific terms used herein have the same meaning as those generally understood by technicians in the technical field of the present application; in the absence of conflict, the embodiments of the present application and the features in the embodiments can be combined with each other; many specific details are explained in the following description to facilitate a full understanding of the present application, and the described embodiments are only part of the embodiments of the present application, not all of the embodiments.

[0018] The uniformity evaluation of existing positive electrode material mixtures is usually carried out by dissolving lithium and then performing chemical titration or potentiometric titration on lithium, which involves pre-treatment steps and complex titration operations. The present application notes that before the positive electrode material materials are mixed, the lithium salt appears white and the precursor appears gray-black or green. After the two are mixed, the color of the mixed material changes. Based on this, the present application attempts to quantify the color characteristics of the mixed material and use the quantified color characteristics to evaluate the uniformity of the mixed material. Based on the theory of three primary colors, the perception of color is the comprehensive result of the stimulation of the three primary colors of red, green, and blue, that is, the color can be described by the three stimulus values, and the three stimulus values ​​can be further converted into data variables in various color models to characterize the color characteristics of the substance.

[0019] Based on this, an embodiment of the present application provides a method for determining the lithium content in a lithium-containing mixed material, the determination method comprising: Step 1: Sampling the lithium-containing mixed material to obtain multiple test samples.

[0020] In some embodiments, the lithium-containing mixed material includes a dry mixed material of a lithium source and a metal hydroxide, or a dry mixed material of a lithium source and a metal oxide.

[0021] Step 2: Convert the color characteristics of the test samples into variable data in the color model, where the color characteristics include one or more of hue, brightness, and color saturation, and the variable data is used to reflect the lithium content in the multiple test samples.

[0022] In some embodiments, the color model includes one or more of CIEXYZ, CIEYxy, CIELab, CIELCh, CIELuv, Hunter Lab, Munsell color system, HSV, YUV, HSB, HIS, CMY, CMYK and RGB.

[0023] In some embodiments, before converting the color characteristics of the lithium-containing mixed material into variable data in the color model, the method further includes: placing the lithium-containing mixed material in a container, wherein the ratio of the height of the lithium-containing mixed material to the height of the container is 2 / 3-3 / 4; and compacting the lithium-containing mixed material.

[0024] The present application has found that the distribution of lithium in the lithium-containing mixed material has a significant effect on the color characteristics inside the lithium-containing mixed material. Therefore, the above-mentioned method for determining the lithium content in the lithium-containing mixed material converts the color characteristics of multiple test samples in the lithium-containing mixed material into variable data. The variable data of the color characteristics can better reflect the lithium content in the test sample, thereby reflecting the distribution information of the lithium content in different test samples according to the variable data of different test samples. In this way, the distribution information of the lithium content inside the lithium-containing mixed material can be obtained without measuring the specific content of lithium.

[0025] In some embodiments, the above-mentioned determination method further includes: analyzing whether there are differences in the variable data of multiple test samples, and judging whether the uniformity of the lithium-containing mixed material is qualified according to the analysis results. By determining whether there are differences in the variable data between multiple test positions in the lithium-containing mixed material, the uniformity of the lithium-containing mixed material can be quickly and accurately evaluated without determining the specific content of lithium.

[0026] In some embodiments, a significance difference analysis can be performed on variable data obtained from multiple transformations, and whether the uniformity of the lithium-containing mixed material is qualified can be determined based on the significance difference analysis results.

[0027] In some embodiments, the significant difference analysis includes one-way ANOVA. Further, one-way ANOVA can be performed in mintab.

[0028] In some embodiments, the color feature includes brightness. The present application finds that the distribution of lithium in the lithium-containing mixed material has a more obvious effect on the brightness inside the lithium-containing mixed material, and obtaining the brightness of the test sample through specific light source conditions, tristimulus values, and a color model with brightness variables can more accurately map the lithium content in the test sample, thereby also being able to more accurately evaluate the uniformity of the lithium-containing mixed material.

[0029] When the color feature is brightness, the brightness of the lithium-containing mixed material is converted into variable data in the color model including: S10: Providing an illumination light source.

[0030] S20: Obtain tristimulus values ​​of the lithium-containing mixed material under an illumination light source.

[0031] S30: Convert the tristimulus values ​​into brightness variables in the color model.

[0032] In some embodiments, the color model includes one or more of CIELab, CIELCh, CIELuv, Hunter Lab, Munsell color system, HSV, YUV, HSB and HIS. It can be understood that when the color feature is brightness, a color model with a brightness parameter is selected to convert the brightness of the material into variable data.

[0033] In order to convert the brightness of the test sample into a brightness variable, it is necessary to obtain the tristimulus values ​​of the material. In the field of color science, the tristimulus values ​​of a material can be measured by a sensor (such as a spectral sensor, more specifically, a colorimeter) to measure the spectrum of a specific wavelength (red, green, and blue) reflected by the material under a specific lighting source, and then the spectrum is converted into the tristimulus values ​​according to the color matching function. The conversion process can be completed by the processor's built-in color matching function and related formulas. Therefore, S20 can include the following more specific steps: S21: Collecting, by means of a sensor, a spectrum reflected by the lithium-containing mixed material under an illumination light source at a preset viewing angle.

[0034] In some embodiments, the preset viewing angle includes one or both of 1° to 4° and greater than 4°. It should be noted that the viewing angle is also called the standard observer, which refers to the angle of projection of the standard sample in the observer's eyes. The size of the object will affect the human eye's recognition of color. For an object at a certain distance from the human eye, if the area of ​​the object is large, the angle formed by the eye is also large, and the image of the object on the retina is large, otherwise the image is small. When observing an object at a viewing angle of 1° to 4°, the foveal cone cells of the human eye are mainly responsible. When observing an object at a viewing angle greater than 4°, the foveal cone cells and the rod cells around the fovea are mainly responsible. As the viewing angle increases, the human eye's perception of color will change. Different color matching functions are obtained for different viewing angles. It can be understood that when a preset viewing angle of 1° to 4° is adopted, the tristimulus values ​​are obtained by converting the 2° standard observer color matching function, and when a preset viewing angle greater than 4° is adopted, the tristimulus values ​​are obtained by converting the 10° supplementary standard observer color matching function.

[0035] In some embodiments, the illumination light source includes a standard light source and a fluorescent light source, and the correlated color temperature of the standard light source is 2856 K to 6504 K. In some embodiments, the standard light source includes one of standard light source D65, standard light source C, and standard light source A.

[0036] S22: Obtaining tristimulus values ​​of the lithium-containing mixed material under the lighting source according to the color matching function.

[0037] S23: Convert the tristimulus values ​​into brightness variables in the color model.

[0038] In some embodiments, the color model includes one or more of CIELab, CIELCh, CIELuv, Hunter Lab and Munsell color systems. It is understandable that in the relevant field, the above color model is selected to be compatible with the test methods of S21, S22 and S23.

[0039] Another embodiment of the present application also provides a determination system that can implement the above-mentioned method for determining the lithium content in the lithium-containing mixed material, and the determination system includes a testing device.

[0040] The above-mentioned testing device is used to convert the color characteristics of the lithium-containing mixed material into variable data in the color model, the color characteristics include one or more of hue, brightness and color saturation, and the variable data is used to reflect the lithium content in multiple test samples.

[0041] In some embodiments, when the color characteristic is brightness, the testing device includes a light source emitter and a colorimetric instrument.

[0042] As the light source emitter, a standard light source and a fluorescent light source are configured, and the correlated color temperature of the standard light source is 2856 K to 6504 K. In some embodiments, the standard light source includes one of the standard light source D65, the standard light source C, and the standard light source A.

[0043] As a colorimetric instrument, a spectral sensor is configured. In some embodiments, the colorimetric instrument is further configured with a first data processor for converting the data of the spectral sensor into tristimulus values ​​according to a color matching function, wherein the color matching function includes a 2° standard observer color matching function and a 10° supplementary standard observer color matching function. In some embodiments, the colorimetric instrument is further configured with a second data processor for converting the tristimulus values ​​into brightness variables in a color model, wherein the color model includes one or more of CIELab, CIELCh, CIELuv, Hunter Lab, and Munsell color systems.

[0044] In some embodiments, the above-mentioned determination system further includes a processor, which is used to analyze whether there are differences in the variable data of multiple test samples, and determine whether the uniformity of the lithium-containing mixed material is qualified according to the analysis results.

[0045] The processor is used to perform significant difference analysis on variable data obtained through multiple transformations.

[0046] In some embodiments, the processor performs a significance difference analysis on variable data obtained from a plurality of transformations, and determines whether the uniformity of the lithium-containing mixed material is qualified according to the significance difference analysis result.

[0047] In some embodiments, the significant difference analysis includes one-way ANOVA. Further, one-way ANOVA can be performed in mintab.

[0048] The scheme of the present application will be explained below in conjunction with the embodiments. Those skilled in the art will understand that the following examples are only used to explain the present application and cannot be construed as limiting the present application. Unless otherwise stated, the reagents, software and instruments not specifically stated in the following embodiments are all conventional commercial products or open source.

[0049] Embodiment 1: The first step is to select 3 batches of NCM dry-mixed samples. The indicators of the finished products corresponding to these 3 batches of samples (electrical properties, particle size and elemental composition) are qualified. They are laid out flat, and 2 on the left, 2 in the middle and 2 on the right are taken from each batch, for a total of 6 test samples.

[0050] In the second step, a D65 light source (relative spectral energy distribution is S(λ)) is used, the colorimeter has an observation angle of 10 degrees, and the sample measurement port size is 30 mm (i.e. the measurement area is a circle with a diameter of 30 mm).

[0051] In the third step, pour the test sample into the culture dish, with the amount of sample higher than 2 / 3 of the height of the culture dish, spread it evenly, and compact the sample; under the conditions set in the second step, use a colorimeter to test, test each test sample twice, and obtain the spectral reflectance R(λ) of the material.

[0052] Step 4: Obtain the color matching function based on the 10° supplementary standard observer , the tristimulus value Y is calculated by the following formula (1) and formula (2): (1); (2).

[0053] Step 5: According to the CIELab color model, when Y / Yn≥0.008856, the brightness variable L is calculated by the following formula (3); when Y / Yn<0.008856, L is calculated by formula (4), where Yn is the value corresponding to the green primary color in the tristimulus values ​​obtained when the total reflection diffuse reflector is illuminated by the same light source S: (3); (4).

[0054] Step 6: Import the measured L value into mintab for one-way ANOVA. Please refer to Table 1 for the results.

[0055] Table 1. Mean and standard deviation of L values ​​of the test samples in three batches of NCM dry mixed samples in Example 1 of the present application In Table 1, the P value is greater than 0.05, indicating that the samples are mixed uniformly. The three batches of NCM dry-mixed samples can be used as standard samples, and thus the uniformity index that meets qualified production can be set to 29.02±0.48 according to X+3Σ.

[0056] Embodiment 2: The first step is to select the NCA dry mixed sample (this sample is a small test material for a new product and there is no corresponding finished product that meets all indicators), flatten it, take 2 on the left, 2 in the middle, and 2 on the right, a total of 6 test samples, and evaluate the sample uniformity.

[0057] In the second step, a D65 light source (relative spectral energy distribution is S(λ)) is used, the colorimeter has an observation angle of 10 degrees, and the sample measurement port size is 30 mm (i.e. the measurement area is a circle with a diameter of 30 mm).

[0058] In the third step, pour the test sample into the culture dish, with the amount of sample higher than 2 / 3 of the height of the culture dish, spread it evenly, and compact the sample; under the conditions set in the second step, use a colorimeter to test, test each test sample 3 times, and obtain the spectral reflectance R(λ) of the material.

[0059] Step 4: Obtain the color matching function based on the 10° supplementary standard observer , the tristimulus value Y is calculated by the following formula (1) and formula (2): (1); (2).

[0060] Step 5: According to the CIELab color model, when Y / Yn≥0.008856, the brightness variable L is calculated by the following formula (3); when Y / Yn<0.008856, L is calculated by formula (4), where Yn is the value corresponding to the green primary color in the tristimulus values ​​obtained when the total reflection diffuse reflector is illuminated by the same light source S: (3); (4).

[0061] Step 6: Import the measured L value into mintab for one-way ANOVA. Please refer to Table 2 for the results.

[0062] Table 2. Homogeneity evaluation of NCA dry mixed sample (small test sample) in Example 2 of this application For new product pilot materials, that is, there is no corresponding finished product that meets each index, the L value can be obtained by the above Example 2, and the L value is subjected to a one-way ANOVA to test whether there is no significant difference in the sample means, so as to characterize the uniformity of the pilot material mixing. In Table 2, the P value>0.05 indicates that the batch of pilot materials is uniformly mixed.

[0063] The above implementation modes are only used to illustrate the technical solutions of the present application and are not intended to limit the present application. Although the present application has been described in detail with reference to the above preferred implementation modes, a person skilled in the art should understand that the technical solutions of the present application may be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present application.

Claims

1. A method for determining the lithium content in a lithium-containing mixed material, characterized in that: The determination method comprises: Sampling the lithium-containing mixed material to obtain a plurality of test samples; The color characteristics of the test samples are converted into variable data in a color model, wherein the color characteristics include one or more of hue, brightness, and color saturation, and the variable data is used to reflect the lithium content in the multiple test samples.

2. The measuring method according to claim 1, characterized in that The determination method further comprises: Analyze whether there are differences in the variable data of the multiple test samples, and determine whether the uniformity of the lithium-containing mixed material is qualified based on the analysis results.

3. The measuring method according to claim 1, characterized in that The color feature includes brightness, and converting the brightness of the lithium-containing mixed material into variable data in a color model includes: Provide lighting source; Obtaining tristimulus values ​​of the lithium-containing mixed material under the illumination light source; The tristimulus values ​​are converted into brightness variables in a color model.

4. The assay method according to claim 3, wherein Obtaining the tristimulus values ​​of the lithium-containing mixed material under the illumination light source comprises: Collecting, by means of a sensor, a spectrum reflected by the lithium-containing mixed material under the illumination light source at a preset viewing angle; Obtaining tristimulus values ​​of the lithium-containing mixed material under the illumination light source according to a color matching function; The tristimulus values ​​are converted into brightness variables in a color model.

5. The assay method according to claim 4, wherein The preset viewing angle includes one or both of 1° to 4° and greater than 4°.

6. The assay method according to claim 3, wherein The illumination light source comprises a standard light source and a fluorescent light source, and the correlated color temperature of the standard light source is 2856K to 6504K.

7. The assay method according to claim 6, wherein The standard light source includes one of the standard light source D65, the standard light source C and the standard light source A.

8. The assay method according to claim 1, wherein The lithium-containing mixed material includes a dry mixed material of a lithium source and a metal hydroxide, or a dry mixed material of the lithium source and a metal oxide.

9. The measuring method according to claim 1, characterized in that Before converting the color characteristics of the lithium-containing mixed material into variable data in a color model, the method further includes: Placing the lithium-containing mixed material in a container, wherein the ratio of the height of the lithium-containing mixed material to the height of the container is 2 / 3-3 / 4; The lithium-containing mixed material is compacted.

10. A system for measuring lithium content in a lithium-containing mixed material, characterized in that: The measuring system comprises: A testing device is used to convert the color characteristics of a lithium-containing mixed material into variable data in a color model, wherein the color characteristics include one or more of hue, brightness and color saturation, and the variable data is used to reflect the lithium content of multiple test samples in the lithium-containing mixed material.

11. The measuring system according to claim 10, wherein The measuring system further comprises: The processor is used to analyze whether there are differences in the variable data of the multiple test samples, and determine whether the uniformity of the lithium-containing mixed material is qualified according to the analysis results.

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