Method and system for measuring lithium content in material

Abstract

The invention relates to a method and system for measuring the lithium content in a material, and the method comprises the steps: converting the color characteristics of the material into variable data in a color model, the color characteristics comprising one or more of hue, brightness and color saturation; acquiring a preset relationship between the standard lithium content and the variable data; and obtaining the lithium content in the material according to the variable data obtained by conversion and a preset relationship. The determination method provided by the invention can rapidly and accurately determine the lithium content of the material.

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 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. Every improvement in the performance of lithium-ion batteries comes from the performance improvement of key materials. In the positive electrode material of nickel-cobalt-manganese oxide lithium compound, the 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 ingredients are accurately mixed has become one of the keys to 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 verify the accuracy of the raw material mixing ratio, the lithium content in the dry mix needs to be quantitatively analyzed. At present, the industry mainly uses chemical titration or potentiometric titration, which uses hydrochloric acid as a titrant and calculates the lithium measurement value through the principle of acid-base neutralization reaction. However, this method has the disadvantages of long testing time, high cost and complicated pre-treatment process, which is 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 material to solve at least one of the above technical problems.

[0005] To achieve the above-mentioned purpose, in a first aspect, the present application provides a method for determining the lithium content in a material, the method comprising: converting the color characteristics of the material into variable data in a color model, the color characteristics including one or more of hue, brightness and color saturation; obtaining a preset relationship between the standard lithium content and the variable data; and obtaining the lithium content in the material based on the converted variable data and the preset relationship.

[0006] In some possible implementations, the color feature includes brightness, and converting the brightness of the material into variable data in the color model includes: providing an illumination light source; obtaining tristimulus values ​​of the material under the illumination light source; and converting the tristimulus values ​​into brightness variables in the color model.

[0007] In some possible implementations, obtaining the tristimulus values ​​of a material under an illumination source includes: collecting, through a sensor, a spectrum reflected by the material under the illumination source at a preset viewing angle; obtaining the tristimulus values ​​of the material under the illumination source according to a color matching function; and converting the tristimulus values ​​into brightness variables in a color model.

[0008] In some possible implementations, the preset viewing angle includes one or both of 1° to 4° and greater than 4°.

[0009] 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.

[0010] 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.

[0011] In some possible implementations, the preset relationship includes a linear relationship between a standard lithium content and the variable data.

[0012] In some possible implementations, the 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 characteristics of the material into variable data in the color model, the method further includes: placing the material in a container, with the ratio of the height of the material to the height of the container being 2 / 3-3 / 4; and compacting the material.

[0014] In a second aspect, the present application provides a system for determining the lithium content in a material, the system comprising: a testing device, a storage device and a processor. The testing device is used to convert the color characteristics of the material into variable data in a color model, the color characteristics including one or more of hue, brightness and color saturation; the storage device is used to store a preset relationship between the standard lithium content and the variable data; the processor is used to obtain the lithium content in the material according to the converted variable data and the preset relationship.

[0015] The determination method of the present application mainly establishes a preset relationship between the material color characteristic variable data and the lithium content. The color characteristic variable data of the material can be measured to reflect the lithium content in the material. This method does not require pre-treatment such as dissolution of lithium, nor does it require complex titration operations. The present application also found that the content of mixed lithium in the material has a more obvious effect on the brightness in the color characteristics of the mixed material. Therefore, by constructing a preset relationship between the brightness variable and the lithium content, the lithium content in the material can be quickly and accurately calculated. Therefore, the determination method of the present application can quickly and accurately determine the lithium content of the material. DETAILED DESCRIPTION

[0016] 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.

[0017] Existing methods for quantifying the lithium content in mixed cathode materials usually require the lithium to be dissolved and then chemically titrated or potentiometrically titrated, involving pre-treatment steps and complex titration operations. The present application notes that before the cathode 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 to quantitatively analyze the lithium in the mixed material. Based on the theory of three primary colors, the perception of color is the combined 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.

[0018] Based on this, an embodiment of the present application provides a method for determining the lithium content in a material, comprising: Step 1: Convert the color characteristics of the material into variable data in the color model. The color characteristics include one or more of hue, brightness and color saturation.

[0019] In some embodiments, the material includes a dry mixture of a lithium source and a metal hydroxide, or a dry mixture of a lithium source and a metal oxide. For example, the material may include lithium nickel cobalt manganese oxide (NCM), lithium nickel cobalt aluminum oxide (NCA), lithium manganese oxide, lithium nickel manganese oxide, and lithium iron phosphate.

[0020] 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.

[0021] In some embodiments, before converting the color characteristics of the material into variable data in the color model, the method further includes: placing the material in a container, with the ratio of the height of the material to the height of the container being 2 / 3-3 / 4; and compacting the material.

[0022] Step 2: Obtain the preset relationship between the standard lithium content and the variable data.

[0023] By establishing a correlation between the material color characteristic variable data and the lithium content, a preset relationship between the two is obtained. The lithium content in the material can be reflected by measuring the material's color characteristic variable data. This method does not require pre-treatment such as dissolution of lithium, nor does it require complicated titration operations.

[0024] Specifically, the standard lithium content is a material with a known lithium content. The color characteristics of a plurality of materials with known lithium contents are converted into variable data in a color model, and a preset relationship between the variable data and the standard lithium content is established according to the lithium content of the material.

[0025] In some embodiments, the predetermined relationship includes a linear relationship between the standard lithium content and the variable data.

[0026] Step three, obtaining the lithium content in the material based on the converted variable data and the preset relationship.

[0027] In some embodiments, the color feature includes brightness. The present application finds that the content of mixed lithium in the material has a more obvious effect on the brightness in the color feature of the mixed material. The brightness in the material is converted into a brightness variable through specific light source conditions, tristimulus values, and a color model with a brightness variable, and a correlation between the brightness variable and the lithium content is constructed to obtain a preset relationship between the two. The lithium content in the material can be calculated without pre-treatment such as dissolution of the lithium, and without complicated titration operations.

[0028] When the color feature is brightness, converting the brightness of the material into variable data in the color model includes: S10: Providing an illumination light source.

[0029] S20: Obtain tristimulus values ​​of the material under the illumination light source.

[0030] S30: Convert the tristimulus values ​​into brightness variables in the color model.

[0031] 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.

[0032] 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: The spectrum reflected by the material under the illumination light source is collected at a preset viewing angle through the sensor.

[0033] 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.

[0034] 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.

[0035] S22: Obtaining the tristimulus values ​​of the material under the lighting source according to the color matching function.

[0036] S23: Convert the tristimulus values ​​into brightness variables in the color model.

[0037] 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.

[0038] An embodiment of the present application further provides a determination system that can implement the above-mentioned method for determining the lithium content in a material. The determination system includes a testing device, a storage device, and a processor.

[0039] The testing device is used to convert the color characteristics of the material into variable data in the color model, and the color characteristics include one or more of hue, brightness and color saturation.

[0040] In some embodiments, when the color characteristic is brightness, the testing device includes a light source emitter and a colorimetric instrument.

[0041] 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.

[0042] 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.

[0043] The memory is used to store the preset relationship between the standard lithium content and the variable data. When the lithium content needs to be measured, the preset relationship between the standard lithium content and the variable data stored in the memory is called or obtained.

[0044] The processor is used to obtain the lithium content in the material according to the variable data obtained by conversion and the preset relationship.

[0045] Based on the method for determining the lithium content in a material provided in the above-mentioned embodiment, another embodiment of the present application provides a method for determining the lithium content in a material, comprising: providing a material with a lithium content of A, a material with a lithium content of B, and a material to be tested, assuming that the lithium content in the material to be tested is n; converting the color characteristics of the material with a lithium content of A into variable data f(A) in a color model; converting the color characteristics of the material with a lithium content of B into variable data f(B) in a color model; converting the color characteristics of the material to be tested into variable data f(n) in a color model, and when f(n) falls within the range formed by f(A) and f(B), the lithium content n of the material to be tested is between A and B.

[0046] In this embodiment, by setting A and B as the industry thresholds of lithium content, by judging whether f(n) falls within the range formed by f(A) and f(B), it can be quickly judged whether the lithium content of the material to be tested meets the standard. For example, the lithium content in the qualified dry blend is within the range between the upper and lower limits of the specification tolerance, and according to experience, the amount of lithium added or less will not exceed twice the specification tolerance. Then, when preparing the standard sample, it is preferred to prepare 5, the first of which is to prepare lithium salt and precursor ingredients according to the ratio given by the process, the second and third are respectively mixed ingredients corresponding to the upper and lower limits of the lithium content specification tolerance, and the fourth and fifth are respectively mixed ingredients corresponding to 2 times the deviation of the upper limit of the specification and 2 times the deviation of the lower limit of the specification. Through the above determination method, the lithium content level of the material to be tested can be quickly judged.

[0047] 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.

[0048] Embodiment 1: A method for determining the lithium content in a material, comprising: S1, prepare ternary dry mixed sample, theoretical lithium content 5.7%, specification tolerance ±0.1%, prepare five kinds of standard samples of 5.5%, 5.6%, 5.7%, 5.8% and 5.9%.

[0049] S2, using D65 light source (relative spectral energy distribution is S(λ)), the colorimeter has a 10 degree observation angle, and the sample measurement port size is 30 mm (i.e. the measurement area is a circle with a diameter of 30 mm).

[0050] S3, pour the standard sample into the culture dish, the amount of sample poured is higher than 2 / 3 of the height of the culture dish, spread it evenly, and compact the sample; under the conditions set in S2, use a colorimeter to test, test each standard sample 3 times, take the average value, and obtain the spectral reflectance R(λ) of the material.

[0051] S4, obtained according to the 10° supplementary standard observer color matching function , the tristimulus value Y is calculated by the following formula (1) and formula (2): (1); (2).

[0052] S5, according to the CIELab color model, when Y / Yn≥0.008856, the brightness variable L is calculated by the following formula (3), and 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).

[0053] S6, taking the mean value of the brightness variable of the five standard samples as the independent variable p, and the lithium salt obtained by the corresponding chemical titration as the dependent variable q, fitting was performed according to the formula q=ap+b, where a and b are fitting constants, and a=0.2878, b=-2.8113 were obtained, that is, the linear correlation curve between the brightness variable of the standard sample and the lithium content is q=0.2878p-2.8113.

[0054] S7, produce two ternary dry mixed samples with unknown lithium content, test them according to the methods of S2 to S5, obtain the color characteristics of the samples to be tested, that is, the brightness variable, substitute it into the fitting result of S6 to obtain the lithium content. Please refer to Table 1 for the results.

[0055] This application conducted a chemical titration test on two ternary dry mixed samples of S7 with unknown lithium content. Please refer to Table 1 for the results.

[0056] Table 1. Comparison of lithium content obtained in Example 1 of the present application with lithium content obtained by chemical titration test As can be seen from Table 1, Example 1 of the present application converts the color characteristics of the material into variable data in the color model, and obtains the lithium content in the material according to the preset relationship between the variable data and the lithium content. The measurement result is close to the chemical titration result, indicating that the lithium content test method of the embodiment of the present application is highly accurate. Moreover, the test method does not require pre-treatment such as dissolution of lithium, nor does it require complex titration operations.

[0057] 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 material, characterized in that: The determination method comprises: Converting the color characteristics of the material into variable data in a color model, wherein the color characteristics include one or more of hue, brightness, and color saturation; Obtaining a preset relationship between the standard lithium content and the variable data; and The lithium content in the material is obtained according to the variable data obtained by conversion and the preset relationship.

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

3. The assay method according to claim 2, wherein Obtaining the tristimulus values ​​of the material under the illumination light source includes: By means of a sensor, a spectrum reflected by the material under the illumination light source is collected at a preset viewing angle; Obtaining tristimulus values ​​of the material under the illumination source according to the color matching function; The tristimulus values ​​are converted into brightness variables in the color model.

4. The assay method according to claim 3, wherein The preset viewing angle includes one or both of 1° to 4° and greater than 4°.

5. The assay method according to claim 2, 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.

6. The assay method according to claim 5, wherein The standard light source includes one of the standard light source D65, the standard light source C and the standard light source A.

7. The measuring method according to claim 1, characterized in that The preset relationship includes a linear relationship between the standard lithium content and the variable data.

8. The assay method according to claim 1, wherein The 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 material into variable data in the color model, it also includes: Placing the material in a container, wherein the ratio of the height of the material to the height of the container is 2 / 3-3 / 4; The material is compacted.

10. A system for determining the lithium content in a material, characterized in that: The measuring system comprises: A testing device, used to convert the color characteristics of the material into variable data in a color model, wherein the color characteristics include one or more of hue, brightness and color saturation; A memory, used to store a preset relationship between a standard lithium content and the variable data; and A processor is used to obtain the lithium content in the material according to the variable data obtained by conversion and the preset relationship.

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