Method for detecting or assisting in regulating and controlling oxidation degree of precursor during precipitation by using chromatograph

Abstract

The invention relates to the technical field of preparation of positive electrode materials, and discloses a method for detecting or assisting in regulating and controlling the oxidation degree of a precursor during precipitation by using a chromatograph. The two methods both comprise the following steps: in the precursor precipitation process, sampling once every period of time; repeatedly detecting precipitates in each group of samples sampled each time by using a chromatograph, recording the precipitation time and chroma data L value corresponding to each detection, and recording the data into an L curve model; the L curve model has an L-down curve and an L-top curve, the L-down curve is a critical curve of good oxidation and excessive oxidation, the L-top curve is a critical curve of good oxidation and insufficient oxidation, and the critical curve is an L value and precipitation time relation curve; and comparing the position relationship between the average value and the two upper and lower limit curves to judge whether the condition of insufficient oxidation or excessive oxidation exists, and adjusting the precipitation process parameters according to the judgment result to ensure that the oxidation degree in the subsequent precipitation process is good.

Description

Technical Field

[0001] The present invention relates to the technical field of cathode material preparation, and in particular, to a method for detecting or assisting in regulating the oxidation degree during the precipitation of a precursor by using a color spectrometer. Background Art

[0002] The capacity of a lithium-ion battery is greatly affected by the cathode material. In order to obtain a cathode material with a higher capacity, the precursor of the cathode material synthesis has also received attention. The surface chemical properties and structure of the precursor determine the electrochemical performance of the synthesized cathode material, which is affected by factors such as the reactor, preparation method, and reaction conditions during the preparation process. Among them, the oxidation degree has a significant impact on the material structure, specifically manifested in affecting the particle morphology, size, and internal pores, etc. Therefore, a method for instant detection is needed to characterize the oxidation degree of the material.

[0003] In view of this, the present invention is specifically proposed. Summary of the Invention

[0004] The purpose of the present invention is to provide a method for detecting or assisting in regulating the oxidation degree during the precipitation of a precursor by using a color spectrometer.

[0005] The present invention is implemented as follows:

[0006] In a first aspect, the present invention provides a method for assisting in regulating the oxidation degree during the precipitation of a precursor by using a color spectrometer, including:

[0007] During the precipitation of the precursor, samples are taken from the reaction kettle every 0.1 - 1.5 h, and the number of groups of samples taken each time is at least one group;

[0008] The precipitate in each group of samples taken each time is subjected to multiple color spectrometer detections, the precipitation time and chromaticity data values corresponding to each detection are recorded, the average value of the chromaticity data of multiple detections of the samples taken each time is calculated, and after obtaining the average value of the chromaticity data each time, this data is recorded into the chromaticity data curve model. The chromaticity data value includes at least one of the L value, a value, and b value; the chromaticity data curve model includes at least one of the L curve model, a curve model, and b curve model;

[0009] In the L curve model, there are an L-down curve and an L-top curve. The L-down curve is the critical curve between good oxidation and over-oxidation, and this critical curve is the relationship curve between the L value and the precipitation time; the L-top curve is the critical curve between good oxidation and under-oxidation, and this critical curve is the relationship curve between the L value and the precipitation time;

[0010] In the a-curve model, there are an a-top curve and an a-down curve. The a-top curve is the critical curve between good oxidation and insufficient oxidation, and this critical curve is the relationship curve between the a value and the precipitation time; the a-down curve is the critical curve between good oxidation and excessive oxidation, and this critical curve is the relationship curve between the a value and the precipitation time;

[0011] In the b-curve model, there are a b-top curve and a b-down curve. The b-top curve is the critical curve between good oxidation and insufficient oxidation, and this critical curve is the relationship curve between the b value and the precipitation time; the b-down curve is the critical curve between good oxidation and excessive oxidation; this critical curve is the relationship curve between the b value and the precipitation time;

[0012] The oxidation situation is judged by the average value of L data, the average value of a data or the average value of b data:

[0013] The method for judging the oxidation situation by the average value of the L data is as follows:

[0014] If the coordinates of the current precipitation time and the average value of the L data are between the L-down curve and the L-top curve, it indicates that the oxidation situation is good; if the coordinates of the current precipitation time and the average value of the L data are not between the L-down curve and the L-top curve, it is determined that the oxidation situation is probably not good;

[0015] The method for judging the oxidation situation by the average value of the a data is as follows:

[0016] If the coordinates of the current precipitation time and the average value of the a data are between the a-down curve and the a-top curve, it indicates that the oxidation situation is good; if the coordinates of the current precipitation time and the average value of the a data are not between the a-down curve and the a-top curve, it is determined that the oxidation situation is probably not good;

[0017] The method for judging the oxidation situation by the average value of the b data is as follows:

[0018] If the coordinates of the current precipitation time and the average value of the b data are between the b-down curve and the b-top curve, it indicates that the oxidation situation is good; if the coordinates of the current precipitation time and the average value of the b data are not between the b-down curve and the b-top curve, it is determined that the oxidation situation is probably not good;

[0019] When it is determined that the situation is probably not good, the staff can adjust the process parameters during the precipitation process to improve the phenomenon of excessive or insufficient oxidation that may exist in the subsequent precipitation process.

[0020] In an alternative embodiment, it includes:

[0021] When the result of the continuous judgment is excessive oxidation, reduce the compressed air in the reaction kettle. When the result of the continuous judgment is too low oxidation degree, increase the compressed air in the reaction kettle.

[0022] In an alternative embodiment, the way to obtain all the top curves and all the down curves is as follows:

[0023] S1. Judge the oxidation degree according to the BET result at the precipitation end point. Collect the test results of the color spectrometers on the pilot production line with qualified BET upper limit oxidation in multiple batches. The process chromaticity data is used as the standard sample data of L-down, a-down, and b-down. Collect the test results of the color spectrometers on the pilot production line with qualified BET lower limit oxidation in multiple batches. The process chromaticity data is used as the standard sample data of the L-top, a-top, and b-top curves.

[0024] S2. On the basis of S1, finely adjust the compressed air process plan to obtain the test results of the color spectrometers on the upper limit stable production line in 3 to 10 batches and the test results of the color spectrometers on the lower limit stable production line in 3 to 10 batches. Collect the effective verification groups in the above test results of the stable production line color spectrometers. The effective verification group is the group with qualified BET at the precipitation end point. Use the process chromaticity data of the effective verification group as the verification data of the upper and lower limit curves of L, a, and b.

[0025] S3. Use the standard sample data in S1 as the standard sample group, and the verification data in S2 as the verification group. Combine the qualified standard sample group and the verification group data to determine the boundary values of the L-up and L-down, a-up and a-down, b-up and b-down curves, and establish a model diagram of the upper and lower limit curves of the L, a, and b values. The critical curve and the verification curve are the curves of the L, a, and b values versus the precipitation time.

[0026] In an alternative embodiment, the multiple batches in step S1 are 2 to 3 batches.

[0027] In an alternative embodiment, in step S2, on the basis of S1, finely adjust the compressed air process plan to obtain the test results of the color spectrometers on the stable production line in 10 batches.

[0028] In an alternative embodiment, the precursor is a mono- or multi-metal hydroxide. The precursor is a hydroxide containing a main metal element. The main metal element includes at least one of nickel, cobalt, and manganese. Optionally, the precursor further contains a doped metal. The doped metal includes at least one of tungsten, titanium, aluminum, magnesium, zirconium, and yttrium.

[0029] In an alternative embodiment, the color spectrometer detection selects the use of a diffuse reflection D65 light source.

[0030] In an alternative embodiment, the color spectrometer used for detection is a spectrophotometer CS-820N.

[0031] In a second aspect, an embodiment of the present invention provides a method for detecting the oxidation degree of a precursor using a color spectrometer, including:

[0032] During the precipitation process of the precursor, samples are taken from the reaction kettle every 0.1 - 1.5 h, and the number of groups of samples taken each time is at least one group;

[0033] Perform multiple color spectrometer detections on the precipitates in each group of samples taken each time, record the precipitation time and chromaticity data values corresponding to each detection, calculate the average chromaticity data value of multiple detections of the samples taken each time, and after obtaining the average chromaticity data value each time, record this data into the chromaticity data curve model. The chromaticity data value includes at least one of the L value, a value, and b value; the chromaticity data curve model includes at least one of the L curve model, a curve model, and b curve model;

[0034] In the L curve model, there are an L-down curve and an L-top curve. The L-down curve is the critical curve between good oxidation and over-oxidation, and this critical curve is the relationship curve between the L value and the precipitation time; the L-top curve is the critical curve between good oxidation and under-oxidation, and this critical curve is the relationship curve between the L value and the precipitation time;

[0035] In the a curve model, there are an a-top curve and an a-down curve. The a-top curve is the critical curve between good oxidation and under-oxidation, and this critical curve is the relationship curve between the a value and the precipitation time; the a-down curve is the critical curve between good oxidation and over-oxidation, and this critical curve is the relationship curve between the a value and the precipitation time;

[0036] In the b curve model, there are a b-top curve and a b-down curve. The b-top curve is the critical curve between good oxidation and under-oxidation, and this critical curve is the relationship curve between the b value and the precipitation time; the b-down curve is the critical curve between good oxidation and over-oxidation; this critical curve is the relationship curve between the b value and the precipitation time;

[0037] Judge the oxidation situation through the average L data, average a data, or average b data:

[0038] The method for judging the oxidation situation through the average L data is as follows:

[0039] If the coordinates of the precipitation time and the average L data for all times are between the L-down and L-top curves, it indicates that the oxidation situation during this precipitation process is good; if there is one or two consecutive times during the middle or later stage of precipitation where the coordinates of the precipitation time and the average L data are not between the L-down curve and the L-top curve, then this precipitation process is determined to have a suspected problem of non-good oxidation situation;

[0040] The method for judging the oxidation situation by the average value of the a data is as follows:

[0041] If the precipitation time and the coordinates of the average value of the a data for all times are between the a-down and the a-top curves, it indicates that the oxidation situation in this precipitation process is good; if there is one or two consecutive times during the middle or later stage of precipitation when the precipitation time and the coordinates of the average value of the a data are not between the a-down curve and the a-top curve, then this precipitation process is determined to have a suspected oxidation situation and is not good.

[0042] The method for judging the oxidation situation by the average value of the b data is as follows:

[0043] If the precipitation time and the coordinates of the average value of the b data for all times are between the b-down and the b-top curves, it indicates that the oxidation situation in this precipitation process is good; if there is one or two consecutive times during the middle or later stage of precipitation when the precipitation time and the coordinates of the average value of the b data are not between the b-down curve and the b-top curve, then this precipitation process is determined to have a suspected oxidation situation and is not good.

[0044] In an alternative embodiment, a diffuse reflection D65 light source is selected for the color spectrometer detection.

[0045] In an alternative embodiment, the color spectrometer used for detection is a spectrophotometer CS-820N.

[0046] In a third aspect, an embodiment of the present invention provides an application of the above method in the preparation of cathode materials.

[0047] The present invention has the following beneficial effects:

[0048] By sampling and detecting the chromaticity of the precipitate during the precipitation process, comparing the chromaticity value with the critical curves of over-oxidation and under-oxidation to judge whether the oxidation degree of the precursor during the precipitation process is good. When it is suspected that the oxidation degree is excessive or insufficient, the precipitation process can be corrected in time by adjusting the subsequent precipitation process or the operation parameters of the next batch of precipitation processes, avoiding greater losses caused by the lag of abnormal detection and reducing the production scrap rate. In addition, the method provided by the present invention also has the following characteristics: quantitatively characterizing the oxidation degree of the precursor, reducing the risk of misjudgment by the human eye; no impurities are introduced during the operation process, and the internal situation of the reaction kettle is not affected; there is no pre-treatment process for the test, no other substances or auxiliary characterization means are introduced, and the test result error is small; simple operation, fast and efficient test, low cost; good stability, small manual error; the solution provided by the present invention is the first application of a spectrophotometer in the new energy field and also the first application of color science in the production link of battery cathode materials, which has important guiding significance. Description of the Drawings

[0049] To more clearly illustrate the technical solutions of the embodiments of the present invention, the following will briefly introduce the accompanying drawings required in the embodiments. It should be understood that the following drawings only show some embodiments of the present invention, and thus should not be regarded as limiting the scope. For those of ordinary skill in the art, without creative efforts, other related drawings can also be obtained based on these drawings.

[0050] Figure 1 L curve model diagram for Example 1 (XTC1);

[0051] Figure 2 a curve model diagram for Example 1;

[0052] Figure 3 b curve model diagram for Example 1;

[0053] Figure 4 L value verification curve for Example 1;

[0054] Figure 5 a value verification curve for Example 1;

[0055] Figure 6 b value verification curve for Example 1;

[0056] Figure 7 Application diagram of the L value verification curve for Example 1 (XTC1);

[0057] Figure 8 Application diagram of the a value verification curve for Example 1;

[0058] Figure 9 Application diagram of the b value verification curve for Example 1;

[0059] Figure 10 L curve model diagram for Example 2 (XTC2);

[0060] Figure 11 a curve model diagram for Example 2;

[0061] Figure 12 b curve model diagram for Example 2;

[0062] Figure 13 Application diagram of the L value verification curve for Example 2 (XTC2);

[0063] Figure 14 Application diagram of the a value verification curve for Example 2;

[0064] Figure 15 Application diagram of the b value verification curve for Example 2. Specific implementation manners

[0065] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. For those not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer are followed. Reagents or instruments not indicated with the manufacturer are all conventional products that can be obtained through commercial purchase.

[0066] The features and performance of the present invention will be further described in detail below in conjunction with embodiments.

[0067] The inventor found that there are color differences in precursor materials with different oxidation degrees. For the process monitoring of the precursor precipitation process, currently only visual means can be used, and the oxidation degree of the material is judged by observing with the naked eye or comparing the color of the slurry with a color comparison card. In addition, other detection means such as specific surface area testing can reflect the oxidation degree of the precursor, but the timeliness is poor. It is necessary to explore an efficient, simple, and quantifiable analysis method to determine the oxidation degree difference in the precursor preparation process.

[0068] In this context, we introduced the concepts of the color science LAB model and statistics, established a new test method, established the correlation between chromaticity and the oxidation degree of the material, and used it to guide the quality control of the future production process. The color spectrometer test method can quickly and quantitatively judge the differences between materials, identify production anomalies in a timely manner according to the experimental results, optimize the production process, reduce energy consumption, and improve production efficiency.

[0069] Color spectrometers are widely used in industries with quality control requirements for product colors, such as: paint coatings, plastic silicone, textile printing and dyeing, printing, food and medicine, hardware electroplating oxidation, ceramics, chemical engineering, etc. Among them, it solves the color quality problems of products in the same batch and different batches in manufacturing, and is convenient for sample quality comparison between different workshops or manufacturers. If the color spectrometer can be applied to the problem of the oxidation degree of materials in the precursor synthesis process, this will be the first application of the spectrophotometer in the new energy manufacturing industry and also the first application of color science knowledge in the production link of battery cathode materials.

[0070] The method for detecting or assisting in regulating the oxidation degree during precursor precipitation provided by the embodiments of the present invention will be specifically described below.

[0071] The method for assisting in regulating the oxidation degree during precursor precipitation provided by the embodiments of the present invention includes:

[0072] During the precursor precipitation process, samples are taken from the reaction kettle every 0.1 - 1.5 h, and the number of groups of each sampling is at least one group;

[0073] Perform multiple color spectrometer detections on the precipitates in each group of samples for each sampling, record the precipitation time and chromaticity data values corresponding to each detection, calculate the average chromaticity data value of the multiple detections of the samples for each sampling, and after obtaining the average chromaticity data value each time, record this data into the chromaticity data curve model. The chromaticity data value includes at least one of the L value, a value, and b value; the chromaticity data curve model includes at least one of the L curve model, a curve model, and b curve model.

[0074] In the L curve model, there are an L-down curve and an L-top curve. The L-down curve is the critical curve between good oxidation and over-oxidation, and this critical curve is the relationship curve between the L value and the precipitation time; the L-top curve is the critical curve between good oxidation and under-oxidation, and this critical curve is the relationship curve between the L value and the precipitation time.

[0075] In the a curve model, there are an a-top curve and an a-down curve. The a-top curve is the critical curve between good oxidation and under-oxidation, and this critical curve is the relationship curve between the a value and the precipitation time; the a-down curve is the critical curve between good oxidation and over-oxidation, and this critical curve is the relationship curve between the a value and the precipitation time.

[0076] In the b curve model, there are a b-top curve and a b-down curve. The b-top curve is the critical curve between good oxidation and under-oxidation, and this critical curve is the relationship curve between the b value and the precipitation time; the b-down curve is the critical curve between good oxidation and over-oxidation; this critical curve is the relationship curve between the b value and the precipitation time.

[0077] Judge the oxidation situation through the average L data, average a data, or average b data:

[0078] The method of judging the oxidation situation through the average L data is as follows:

[0079] If the coordinates of the current precipitation time and the average L data are between the L-down curve and the L-top curve, it indicates that the oxidation situation is good; if the coordinates of the current precipitation time and the average L data are not between the L-down curve and the L-top curve, it is determined that the suspected oxidation situation is not good.

[0080] The method of judging the oxidation situation through the average a data is as follows:

[0081] If the coordinates of the current precipitation time and the average a data are between the a-down curve and the a-top curve, it indicates that the oxidation situation is good; if the coordinates of the current precipitation time and the average a data are not between the a-down curve and the a-top curve, it is determined that the suspected oxidation situation is not good.

[0082] The method of judging the oxidation situation through the average b data is as follows:

[0083] If the coordinates of the current precipitation time and the average value of b data are between the b-down curve and the b-top curve, it indicates that the oxidation condition is good; if the coordinates of the current precipitation time and the average value of b data are not between the b-down curve and the b-top curve, it is determined that the suspected oxidation condition is not good.

[0084] After it is determined that the suspected condition is not good, the staff can adjust the process parameters during the precipitation process to improve the phenomenon of excessive or insufficient oxidation that may exist in the subsequent precipitation process.

[0085] In the present invention, L represents the brightness (black and white) of the slurry, a represents the red and green of the slurry, and b represents the yellow and blue of the slurry.

[0086] The inventors found that there is a certain correlation between the oxidation degree of the precursor, the BET size and the chromaticity during the precipitation process. Based on this, the method for using a color spectrometer to assist in regulating the oxidation degree during the precipitation of the precursor provided by the present invention detects the chromaticity of the precipitate by sampling during the precipitation process, and compares the chromaticity value with the critical curves of over-oxidation and under-oxidation to determine whether the oxidation degree of the precursor during the precipitation process is good. When it is detected that the oxidation degree is suspected to be excessive or insufficient, the precipitation process can be corrected in time by adjusting the operation parameters during the precipitation process in time, avoiding greater losses caused by the lag of abnormal detection and reducing the production scrap rate. In addition, the method provided by the present invention also has the following characteristics: quantitatively characterizing the oxidation degree of the precursor, which can reduce the risk of misjudgment by the human eye; no impurities are introduced during the operation process, and the internal situation of the reaction kettle is not affected; there is no pre-treatment process for the test, no other substances or auxiliary characterization means are introduced, and the test result error is small; the operation is simple, the test is fast and efficient, and the cost is low; the stability is good and the human error is small.

[0087] For the method provided by the present invention, the oxidation condition can be judged by the average value of L data, the average value of a data or the average value of b data. Usually, the average value of L data can be selected to judge whether the oxidation degree is good. Since the types of precursors prepared are different and the nickel-cobalt-manganese ratios are different, the corresponding colors are different. When it is difficult to judge by the average value of L data, the average value of a data or the average value of b data can be selected for judgment. The situation where it is difficult to judge by the average value of L data is, for example: when the precipitated precursor is more easily oxidized to black, the difference between the L-top curve and the L-down curve is small, and the average value of L data is easily beyond the L-top curve and the L-down curve.

[0088] Specifically, the operation method is as follows:

[0089] S1. Feed raw materials into the reaction kettle

[0090] A mixed solution of metal salts with different main metal ratios (for example, using nickel-cobalt-manganese salts as the main metals, and the molar ratios of the three can be 8:1:1, 5:3:2, 6:2:2, 3:3:3, etc.), a precipitating agent, a complexing agent, etc. are simultaneously added to a reaction kettle, and a precursor material is synthesized by a co-precipitation method. If a precursor with a doping element is to be prepared, in this step, in addition to the main metals, the mixed solution of metal salts also contains doping metals, and the doping metals can be, for example, at least one of tungsten, titanium, aluminum, magnesium, zirconium, and yttrium.

[0091] The method provided by the present invention is applicable to the preparation of mono- or multi-component precursors by all precipitation methods. The precipitation method for preparing precursors is a common method for preparing mono- or multi-component cathode materials at present, and its specific content will not be elaborated here too much.

[0092] S2. Sampling and detection

[0093] Within a primary precipitation period of 30 - 120 h (preferably 50 - 80 h), taking 0.1 - 1.5 h (such as 0.5 h, 1 h, or 1.5 h) as the gradient unit, precipitation process samples are taken out from the reaction kettle respectively, and the number of sampling groups each time is 1 group or multiple groups. The taken precursor slurry samples are in a suspension state, and the sampling amount is 10 ml. The samples are placed in a quartz dish for testing, stirred evenly, and then allowed to settle naturally for spectroscope testing.

[0094] S3. Spectroscope testing

[0095] Turn on the spectroscope, complete the calibration, and select the light source. Each group of samples for each sampling is tested multiple times, and the L, a, b values of the samples are recorded and the average value is taken. A total of n groups of test average values (L 1 ~L n , a 1 ~a n , b 1 ~b n ) are obtained during a primary precipitation period. For example: L 0.5 , L 1 , L 1.5 , L 2 , …L 60 , …L m ; a 0.5 , a 1 , a 1.5 , a 2 , …a 60 , …a m ; b 0.5 , b 1 , b 1.5 , b 2 , …b 60 , b m (the subscript m is the precipitation time, in units of h).

[0096] Preferably, to obtain accurate detection results, a diffuse reflection D65 light source is selected for the color spectrometer detection.

[0097] Optionally, the color spectrometer used for detection is a spectrocolorimeter CS-820N.

[0098] S4. Oxidation degree determination

[0099] After obtaining a set of average value data each time, record this data into the L curve model, a curve model, and b curve model respectively; analyze the oxidation degree of the sample precipitated at this time point.

[0100] When the oxidation situation of the precursor can be judged by the L value:

[0101] Analyze the sample data L n : When the L value is basically within the [L-top, L-down] interval, it is judged that the oxidation is normal and the sample is qualified; when the L value exceeds the L-top curve for more than 2 consecutive points, it is judged that the oxidation is insufficient and the BET is small; when the L value is lower than the L-down curve, it is judged that the oxidation is excessive and the BET is large.

[0102] When it is difficult to judge the oxidation situation of the precursor by the L value, for example, when there is no linear relationship between the oxidation degree of the material itself and the brightness of the L value, judge by the a value or b value:

[0103] Analyze the sample data a n : When the a value is basically within the [a-top, a-down] interval, it is judged that the oxidation is normal and the sample is qualified; when the a value exceeds the a-top curve for more than 2 consecutive points, it is judged that the oxidation is insufficient and the BET is small; when the a value is lower than the a-down curve, it is judged that the oxidation is excessive and the BET is large.

[0104] Analyze the sample data b n : When the b value is basically within the [b-top, b-down] interval, it is judged that the oxidation is normal and the sample is qualified; when the b value exceeds the b-top curve for more than 2 consecutive points, it is judged that the oxidation is insufficient and the BET is small; when the b value is lower than the b-down curve, it is judged that the oxidation is excessive and the BET is large.

[0105] S5. Process adjustment

[0106] When the result obtained by continuous judgment is that the oxidation is excessive or insufficient, adjust the process parameters during the precipitation process to improve the phenomenon of excessive or insufficient oxidation degree in the subsequent precipitation process;

[0107] Specifically, when the result of continuous judgment shows over-oxidation or under-oxidation, the method of adjusting process parameters during the precipitation process is as follows: when the result of continuous judgment shows over-oxidation, reduce the air pressure in the reaction kettle; when the result of continuous judgment shows too low oxidation degree, increase the air pressure in the reaction kettle.

[0108] Further, before performing the above steps S1 to S5, it is necessary to pre-obtain the L-down curve, L-top curve, a-top curve, a-down curve, b-top curve, and b-down curve.

[0109] As oxidation progresses, the material structure tends to be loose, the primary particles are elongated, and the specific surface area is large. Therefore, the degree of oxidation can be judged according to the BET specific surface area result at the precipitation end point. Therefore, in the following acquisition method, the BET of the obtained precursor product is used to correlate its oxidation degree, thereby obtaining the curve.

[0110] The specific acquisition method is as follows:

[0111] (1) Judge the oxidation degree according to the BET result at the precipitation end point, collect the test results of the color spectrometers of multiple batches (such as 2 batches or 3 batches) of trial production lines with qualified BET upper limit oxidation, and use the process chromaticity data as the standard sample data of L-down, a-down, and b-down. Collect the test results of the color spectrometers of multiple batches of trial production lines with qualified BET lower limit oxidation, and use the process chromaticity data as the standard sample data of the L-top, a-top, and b-top curves.

[0112] (2) On the basis of the above step (1), finely adjust the air pressure process plan to obtain the test results of 3 to 10 batches (preferably 5 batches) of upper limit stable production line color spectrometers and the test results of 3 to 10 batches (preferably 5 batches) of lower limit stable production line color spectrometers. Collect the effective verification groups in the above batch of stable production line color spectrometer test results. The effective verification group is the group with qualified BET at the precipitation end point, and use the process chromaticity data of the effective verification group as the verification data of the L, a, and b upper and lower limit curves;

[0113] (3) Use the standard sample data in S1 as the standard sample group, use the verification data in S2 as the verification group, and combine the qualified standard sample group and verification group data to determine the boundary values of the L-up and L-down, a-up and a-down, b-up and b-down curves, and establish a model diagram of the L, a, and b value upper and lower limit curves. The critical curve and the verification curve are the curves of the relationship between the L, a, and b values and the precipitation time.

[0114] Optionally, in order to improve the accuracy, the sampling data involved in the above steps (1) to (3) are average data, that is, multiple samples are taken each time, and the average value of these multiple samples is measured.

[0115] Optionally, the fine-tuning scheme mentioned in step (2) may be as follows:

[0116] It is divided into the upward adjustment (deoxidation) and downward adjustment (strong oxidation) of the LAB chromaticity curve (or the BET at the precipitation end point, inversely linearly correlated). For example, the strong oxidation process of XTC1 is 5 ± 0.5 cubic meters of air pressure, and the deoxidation process depends on the precipitation time period, with a value of 1 to 2 ± 0.5 cubic meters; the strong oxidation process of XTC2 is 17.5 to 20 cubic meters of air pressure, and the deoxidation process depends on the precipitation time period, with a value of 9 to 19 cubic meters.

[0117] It should be noted that the set upper limit oxidation qualification and lower limit oxidation qualification here are only one example, and for different types of precursor products or different enterprise requirements, their set values may be different.

[0118] The present invention also provides a method for detecting the oxidation degree of the precursor using a color spectrometer, and its implementation method is slightly different from the above method for using a color spectrometer to assist in regulating the oxidation degree during the precipitation of the precursor.

[0119] This method includes:

[0120] During the precipitation process of the precursor, samples are taken from the reaction kettle every 0.1 to 1.5 hours, and the number of groups of samples taken each time is at least one group;

[0121] The precipitate in each group of samples taken each time is detected by a color spectrometer multiple times, the precipitation time and chromaticity data value corresponding to each detection are recorded, the average chromaticity data of multiple detections of the samples taken each time is calculated, and after obtaining the average chromaticity data each time, this data is recorded into the chromaticity data curve model. The chromaticity data value includes at least one of the L value, a value, and b value; the chromaticity data curve model includes at least one of the L curve model, a curve model, and b curve model;

[0122] In the L curve model, there are an L-down curve and an L-top curve. The L-down curve is the critical curve between good oxidation and over-oxidation, and this critical curve is the relationship curve between the L value and the precipitation time; the L-top curve is the critical curve between good oxidation and under-oxidation, and this critical curve is the relationship curve between the L value and the precipitation time;

[0123] In the a curve model, there are an a-top curve and an a-down curve. The a-top curve is the critical curve between good oxidation and under-oxidation, and this critical curve is the relationship curve between the a value and the precipitation time; the a-down curve is the critical curve between good oxidation and over-oxidation, and this critical curve is the relationship curve between the a value and the precipitation time;

[0124] In the b-curve model, there are a b-top curve and a b-down curve. The b-top curve is the critical curve between good oxidation and insufficient oxidation, and this critical curve is the curve of the relationship between the b value and the precipitation time; the b-down curve is the critical curve between good oxidation and over-oxidation; this critical curve is the curve of the relationship between the b value and the precipitation time;

[0125] The oxidation situation is judged by the average value of L data, the average value of a data or the average value of b data:

[0126] The method of judging the oxidation situation by the average value of L data is as follows:

[0127] If the coordinates of the precipitation time and the average value of L data for all times are between the L-down curve and the L-top curve, it indicates that the oxidation situation in this precipitation process is good; if there is one or two consecutive times during the middle or late stage of precipitation where the coordinates of the precipitation time and the average value of L data are not between the L-down curve and the L-top curve, then this precipitation process is determined to have a suspected non-good oxidation situation;

[0128] The method of judging the oxidation situation by the average value of a data is as follows:

[0129] If the coordinates of the precipitation time and the average value of a data for all times are between the a-down curve and the a-top curve, it indicates that the oxidation situation in this precipitation process is good; if there is one or two consecutive times during the middle or late stage of precipitation where the coordinates of the precipitation time and the average value of a data are not between the a-down curve and the a-top curve, then this precipitation process is determined to have a suspected non-good oxidation situation;

[0130] The method of judging the oxidation situation by the average value of b data is as follows:

[0131] If the coordinates of the precipitation time and the average value of b data for all times are between the b-down curve and the b-top curve, it indicates that the oxidation situation in this precipitation process is good; if there is one or two consecutive times during the middle or late stage of precipitation where the coordinates of the precipitation time and the average value of b data are not between the b-down curve and the b-top curve, then this precipitation process is determined to have a suspected non-good oxidation situation.

[0132] The method for detecting the oxidation degree of the precursor with a color spectrometer can judge whether there is over-oxidation or insufficient oxidation in the precipitation process by comparing the detected chromaticity value data curve with the top curve and the down curve. When it is judged that there is a suspected over-oxidation or insufficient oxidation situation in this precipitation process, the process parameters can be adjusted in the next batch of production on this production line to avoid over-oxidation or insufficient oxidation as much as possible.

[0133] There is no clear limitation on the middle or late stage of precipitation mentioned in this application. Generally, it can be set according to industry experience. For example, the first 1 / 3 of the total precipitation time can be used as the early stage, the second 1 / 3 time period as the middle stage, and the third 1 / 3 time period as the late stage.

[0134] The method for detecting the oxidation degree of the precursor using a color spectrometer provided by the present invention has the same advantages as the method for assisting in regulating the oxidation degree during the precipitation of the precursor using a color spectrometer.

[0135] It should be noted that for the above two methods provided by the present invention, different types of precursors correspond to different upper and lower limit curves. Therefore, when testing different types of precursors, it is necessary to compare them with their corresponding upper and lower limit curves.

[0136] The present invention also provides the application of the above two methods in the preparation of cathode materials. When the above two methods are applied in the preparation of cathode materials, the qualification rate of the cathode materials can be improved.

[0137] Example 1

[0138] This example takes the preparation of XTC1 (nickel-cobalt-manganese ratio of 6:2:2) as an example.

[0139] Obtain the upper limit (top) curve and the lower limit (down) curve:

[0140] S1. Judge the oxidation degree according to the BET specific surface area result at the precipitation end point. Collect the test results of the color spectrometers on the trial production line with qualified BET upper limit oxidation in 3 batches. The process chromaticity data is used as the standard sample data for L-down, a-down, and b-down. Collect the test results of the color spectrometers on the trial production line with qualified BET lower limit oxidation in 3 batches. The process chromaticity data is used as the standard sample data for the L-top, a-top, and b-top curves.

[0141] S2. On the basis of S1, finely adjust the air pressure process plan to obtain the test results of the color spectrometers on the upper limit batch stable production line in 5 batches and the test results of the color spectrometers on the lower limit batch stable production line in 5 batches. Among them, there are valid verification groups (4 groups for each of the upper and lower limits) and invalid verification groups (1 group for each of the upper and lower limits). The BET results at the precipitation end point of the valid verification groups are qualified, and the BET results at the precipitation end point of the invalid verification groups exceed the limit. Collect the test results of the color spectrometers on the stable production line with qualified oxidation in 10 batches. The process chromaticity data is used as the verification data for the L, a, and b upper and lower limit curves.

[0142] S3. Using the upper and lower limit standard sample data of each of the 3 groups in S1 as the standard sample group, and the upper and lower limit verification data of each of the 4 groups in the effective verification group in S2 as the verification group, combining the qualified standard sample group and verification group data to determine the boundary values of the L-up and L-down, a-up and a-down, b-up and b-down curves, and establishing a model diagram of the upper and lower limit curves of the L, a, and b values. The critical curve and the verification curve are the curves showing the relationship between the L, a, and b values and the precipitation time.

[0143] Obtain the Figures 1 - 3 as shown upper and lower limit curves. Figure 1 Among them, the abscissa is the precipitation cycle unit h, and the ordinate is the L value; Figure 2 Among them, the abscissa is the precipitation cycle unit h, and the ordinate is the a value; Figure 3 Among them, the abscissa is the precipitation cycle unit h, and the ordinate is the b value.

[0144] Use 7 batches of stable and qualified samples (C03006, C03018, C03023, C02020, C01022, B04001, B03002) and 2 batches of unqualified samples (C01009, B05001) to verify the effectiveness of the upper and lower limit curves. As Figures 4 - 6 shown, Figure 4 is the verification curve of the L value, Figure 5 is the verification curve of the a value, Figure 6 is the verification curve of the b value. Through Figures 4 - 6 it can be seen that the curves C01009 and B05001 are in the middle and late stages of precipitation, while the other curves are between the upper and lower limit curves in the middle and late stages of precipitation.

[0145] This is consistent with the standard for verifying whether oxidation is qualified provided by the present invention, indicating that the upper and lower limit curves obtained in this embodiment are effective.

[0146] The precipitation process of XTC1 is as follows:

[0147] Introduce nitrogen into the reaction kettle for more than 4 hours to remove the oxygen in the reaction kettle. Configure a mixed metal sulfate solution of nickel, cobalt, and manganese according to a predetermined molar ratio (6:2:2). Simultaneously introduce the ternary metal salt solution, precipitant (sodium hydroxide solution), and complexing agent (ammonia water concentration of 5 g / L) into the reaction kettle for coprecipitation crystallization reaction. Control the stirring speed of the reaction kettle at 600 rpm, the temperature of the reaction slurry at 50 °C, and the pH value of the solution at 10 - 13, so that the salt and alkali react to form ternary precursor crystal nuclei and gradually grow. The reaction time is 115 h. When the particle size D50 reaches 10 μm, filter, wash, and dry the reaction slurry to obtain the ternary precursor.

[0148] Samples were taken every 1 h after the precipitation started, and each sample was detected 3 times on the color spectrometer and the average value was taken. The average values of the obtained L, a, and b data were substituted into the upper and lower limit curve models obtained above.

[0149] Figure 7 It is the application diagram of the L-value verification curve; Figure 8 It is the application diagram of the a-value verification curve; Figure 9 It is the application diagram of the b-value verification curve. It can be seen from the figure that there are cases where the data exceeds the upper and lower limits during the initial precipitation. After adjustment, the later data are all between the upper and lower limit curves.

[0150] Example 2

[0151] This example takes the preparation of product model XTC2 (the ratio of nickel, cobalt, and manganese is 3:3:3) as an example.

[0152] The upper limit (top) curve and the lower limit (down) curve were obtained.

[0153] The process parameters of the standard sample group were finely adjusted by using the data of the verification group. Combining the data of the standard sample group and the verification group, the precipitation period-chromaticity curve was plotted, and the oxidation limit curve model was established. The upper and lower limit curves as shown in Figures 10 - 12 were obtained. Figure 10 Among them, the abscissa is the precipitation period in hours, and the ordinate is the L value; Figure 11 Among them, the abscissa is the precipitation period in hours, and the ordinate is the a value; Figure 12 Among them, the abscissa is the precipitation period in hours, and the ordinate is the b value.

[0154] The precipitation process of XTC2 refers to Example 1:

[0155] Figure 13 It is the application diagram of the L-value verification curve; Figure 14 It is the application diagram of the a-value verification curve; Figure 15 It is the application diagram of the b-value verification curve.

[0156] In this example, since the precursor with a nickel-cobalt-manganese ratio of 3:3:3 is easily oxidized to black during precipitation, as shown in Figure 13 , it is difficult to judge the oxidation situation through the upper and lower limit curves of the L value. Therefore, in this example, the upper and lower limit curves of the a value and the upper and lower limit curves of the b value are used to judge. It can be seen from Figure 14 and Figure 15 that there are cases where the data exceeds the upper and lower limits during the initial precipitation. After adjustment, the later data are all between the upper and lower limit curves.

[0157] In summary, the method for detecting or assisting in regulating the oxidation degree during the precipitation of the precursor provided by the present invention samples and detects the chromaticity of the precipitate during the precipitation process, and compares the chromaticity value with the critical curves of over-oxidation and under-oxidation to determine whether the oxidation degree of the precursor during the precipitation process is good. When it is detected that the oxidation degree is excessive or insufficient, the precipitation process can be corrected in a timely manner by adjusting the subsequent precipitation process or the operating parameters of the next batch of precipitation processes, avoiding greater losses caused by the lag of abnormal detection and reducing the production rejection rate. In addition, the method provided by the present invention also has the following characteristics: quantitatively characterizing the oxidation degree of the precursor, which can reduce the risk of misjudgment by the human eye; no impurities are introduced during the operation process, and the internal situation of the reaction kettle is not affected; there is no pre-treatment process for the test, no other substances or auxiliary characterization means are introduced, and the test result error is small; the operation is simple, the test is fast and efficient, and the cost is low; the stability is good and the human error is small.

[0158] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention can have various changes and modifications. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A method for assisting in regulating the oxidation degree during the precipitation of a precursor by using a color spectrometer, characterized in that, it includes: During the precipitation of the precursor, samples are taken from the reaction kettle every 0.1 - 1.5 h, and the number of groups of samples taken each time is at least one group; The precipitate in each group of samples taken each time is subjected to multiple color spectrometer detections. Record the precipitation time and chromaticity data values corresponding to each detection, calculate the average chromaticity data of multiple detections of the samples taken each time. After obtaining the average chromaticity data each time, record this data into the chromaticity data curve model. The chromaticity data values include at least one of the L value, a value, and b value; The chromaticity data curve model includes at least one of the L curve model, a curve model, and b curve model; In the L curve model, there are an L - down curve and an L - top curve. The L - down curve is the critical curve between good oxidation and over - oxidation, and this critical curve is the relationship curve between the L value and the precipitation time; The L - top curve is the critical curve between good oxidation and insufficient oxidation, and this critical curve is the relationship curve between the L value and the precipitation time; In the a curve model, there are an a - top curve and an a - down curve. The a - top curve is the critical curve between good oxidation and insufficient oxidation, and this critical curve is the relationship curve between the a value and the precipitation time; The a - down curve is the critical curve between good oxidation and over - oxidation, and this critical curve is the relationship curve between the a value and the precipitation time; In the b curve model, there are a b - top curve and a b - down curve. The b - top curve is the critical curve between good oxidation and insufficient oxidation, and this critical curve is the relationship curve between the b value and the precipitation time; The b - down curve is the critical curve between good oxidation and over - oxidation; This critical curve is the relationship curve between the b value and the precipitation time; Judge the oxidation situation through the average L data, average a data, or average b data: The method of judging the oxidation situation through the average L data is: If the coordinates of the current precipitation time and the average L data are between the L - down curve and the L - top curve, it indicates that the oxidation situation is good; If the coordinates of the current precipitation time and the average L data are not between the L - down curve and the L - top curve, it is determined that the suspected oxidation situation is not good; The method of judging the oxidation situation through the average a data is: If the coordinates of the current precipitation time and the average a data are between the a - down curve and the a - top curve, it indicates that the oxidation situation is good; If the coordinates of the current precipitation time and the average a data are not between the a - down curve and the a - top curve, it is determined that the suspected oxidation situation is not good; The method of judging the oxidation situation through the average b data is: If the coordinates of the current precipitation time and the average b data are between the b - down curve and the b - top curve, it indicates that the oxidation situation is good; If the coordinates of the current precipitation time and the average b data are not between the b - down curve and the b - top curve, it is determined that the suspected oxidation situation is not good; After it is determined that the suspected situation is not good, the staff can adjust the process parameters during the precipitation process to improve the phenomenon of excessive or insufficient oxidation that may exist in the subsequent precipitation process.

2. The method according to claim 1, wherein, it includes: When the result obtained from the continuous judgment is excessive oxidation, reduce the size of the compressed air in the reaction kettle; when the result obtained from the continuous judgment is too low oxidation degree, increase the size of the compressed air in the reaction kettle.

3. The method according to claim 1, wherein, The acquisition methods of all the top curves and all the down curves are as follows: S1. Judge the oxidation degree according to the BET result at the precipitation end point. Collect the test results of the color spectrometers on the trial production line with qualified BET upper limit oxidation in multiple batches, and the process chromaticity data as the standard sample data of L-down, a-down, and b-down. Collect the test results of the color spectrometers on the trial production line with qualified BET lower limit oxidation in multiple batches, and the process chromaticity data as the standard sample data of the L-top, a-top, and b-top curves; S2. On the basis of S1, finely adjust the compressed air process plan to obtain the test results of the color spectrometers on the upper limit production line in 3 to 10 batches and the test results of the color spectrometers on the lower limit production line in 3 to 10 batches. Collect the effective verification groups in the above-mentioned test results of the production line color spectrometers. The effective verification group is the group with qualified BET at the precipitation end point. Use the process chromaticity data of the effective verification group as the verification data of the L, a, and b upper and lower limit curves; S3. Use the standard sample data in S1 as the standard sample group, use the verification data in S2 as the verification group, combine the qualified standard sample group and the verification group data to determine the boundary values of the L-up and L-down, a-up and a-down, b-up and b-down curves, and establish a model diagram of the L, a, and b value upper and lower limit curves. The critical curve and the verification curve are the curves of the relationship between the L, a, and b values and the precipitation time.

4. The method according to claim 3, wherein, The "multiple batches" in step S1 is 2 to 3 batches; Optionally, in step S2, on the basis of S1, finely adjust the compressed air process plan to obtain the test results of the color spectrometers on the production line in 10 batches.

5. The method according to claim 1, wherein, The precursor is a mono- or multi-metal hydroxide. The precursor is a hydroxide containing a main metal element. The main metal element includes at least one of nickel, cobalt, and manganese; optionally, the precursor also contains a doped metal, and the doped metal includes at least one of tungsten, titanium, aluminum, magnesium, zirconium, and yttrium.

6. The method according to claim 1, wherein, The color spectrometer detection selects the use of a diffuse reflection D65 light source; Optionally, the color spectrometer used for detection is a spectrophotometer CS-820N.

7. A method for detecting the oxidation degree of a precursor using a color spectrometer, wherein, it includes: During the precipitation process of the precursor, take samples from the reaction kettle every 0.1 to 1.5 h, and the number of groups of each sampling is at least one group; Perform multiple spectroscope detections on the precipitate in each group of samples for each sampling, record the precipitation time and chromaticity data values corresponding to each detection, calculate the average chromaticity data value of the multiple detections of the samples for each sampling. After obtaining the average chromaticity data value each time, record this data into the chromaticity data curve model. The chromaticity data value includes at least one of the L value, a value, and b value; the chromaticity data curve model includes at least one of the L curve model, a curve model, and b curve model; In the L curve model, there are an L-down curve and an L-top curve. The L-down curve is the critical curve between good oxidation and over-oxidation. This critical curve is the relationship curve between the L value and the precipitation time; the L-top curve is the critical curve between good oxidation and under-oxidation. This critical curve is the relationship curve between the L value and the precipitation time; In the a curve model, there are an a-top curve and an a-down curve. The a-top curve is the critical curve between good oxidation and under-oxidation. This critical curve is the relationship curve between the a value and the precipitation time; the a-down curve is the critical curve between good oxidation and over-oxidation. This critical curve is the relationship curve between the a value and the precipitation time; In the b curve model, there are a b-top curve and a b-down curve. The b-top curve is the critical curve between good oxidation and under-oxidation. This critical curve is the relationship curve between the b value and the precipitation time; the b-down curve is the critical curve between good oxidation and over-oxidation. This critical curve is the relationship curve between the b value and the precipitation time; Judge the oxidation situation through the average L data, average a data, or average b data: The method of judging the oxidation situation through the average L data is: If the coordinates of the precipitation time and the average L data for all times are between the L-down and L-top curves, it indicates that the oxidation situation of this precipitation process is good; If there is one or two consecutive times during the middle or late stage of precipitation where the coordinates of the precipitation time and the average L data are not between the L-down curve and the L-top curve, then this precipitation process is determined to have a suspected non-good oxidation situation problem; The method of judging the oxidation situation through the average a data is: If the coordinates of the precipitation time and the average a data for all times are between the a-down and a-top curves, it indicates that the oxidation situation of this precipitation process is good; if there is one or two consecutive times during the middle or late stage of precipitation where the coordinates of the precipitation time and the average a data are not between the a-down curve and the a-top curve, then this precipitation process is determined to have a suspected non-good oxidation situation problem; The method of judging the oxidation situation through the average b data is: If the coordinates of the precipitation time and the average b data for all times are between the b-down and b-top curves, it indicates that the oxidation situation of this precipitation process is good; If, during the mid or late stage of precipitation, the coordinates of the average value of the precipitation time and b data are not between the b-down curve and the b-top curve for once or continuously twice, then this precipitation process is determined to have a suspected oxidation situation, which is a non-good problem.

8. The method according to claim 7, wherein, the color spectrometer is selected to use a diffuse reflection D65 light source for detection.

9. The method according to claim 7, wherein, the color spectrometer used for detection is a spectrocolorimeter CS-820N.

10. The application of the method according to any one of claims 1 to 6, or the method according to any one of claims 7 to 9 in the preparation of the cathode material.

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