Method for detecting contents of copper and zinc in battery material

Abstract

The invention discloses a method for detecting the content of copper and zinc in a battery material, which comprises the following steps: carrying out wet screening on a positive electrode material of a battery, and collecting oversize products to obtain a pretreated sample; wherein a solution used in the wet screening process comprises water and a first dispersing agent; adding the pretreated sample into an ammonia water solution for reaction to form a to-be-detected solution; and detecting the to-be-detected liquid, and obtaining the copper and zinc contents in the to-be-detected liquid. The positive electrode material is subjected to wet screening, copper and zinc particles separated out from the positive electrode material are enriched and then subjected to a complexation reaction with an ammonia water solution, the to-be-detected solution is obtained, the specific content of copper and zinc separated out from the positive electrode material is obtained through the content of copper and zinc in the to-be-detected solution, and the detection method is simple, easy to implement, high in detection rate and high in accuracy.

Description

Technical Field

[0001] The present application relates to the field of battery technology, and in particular to a method for detecting the copper and zinc content in battery materials. Background Art

[0002] During the synthesis process of lithium-ion battery cathode materials, foreign matter can be introduced due to factors such as raw material introduction and equipment wear. This is particularly true of copper and zinc, which can precipitate from the cathode at relatively low voltages (2V-3V), directly leading to poor self-discharge K values. Therefore, to ensure the optimal electrochemical performance and safety of lithium-ion batteries, it is necessary to monitor and control the precipitated copper and zinc content. Summary of the Invention

[0003] The present application provides a method for detecting the copper and zinc content in battery materials, which is used to detect the copper and zinc content and has a high detection rate.

[0004] To solve the above technical problems, a technical solution adopted in the present application is: to provide a method for detecting the copper and zinc content in battery materials, comprising: wet screening the positive electrode material of the battery, collecting the material on the sieve to obtain a pretreated sample; wherein the solution used in the wet screening process includes water and a first dispersant; adding an ammonia aqueous solution to the pretreated sample to react to form a liquid to be tested; testing the liquid to be tested, and obtaining the copper and zinc content in the liquid to be tested.

[0005] The positive electrode material is first wet-screened, and the copper and zinc particles precipitated in the positive electrode material are enriched to form a pretreated sample. The pretreated sample undergoes a complexation reaction with an ammonia solution to obtain a test liquid. The test liquid is tested to obtain the copper and zinc content in the test liquid, and then the specific content of copper and zinc precipitated in the positive electrode material is obtained. The detection method is simple and easy, with a high detection rate and high accuracy.

[0006] In one embodiment, adding the pretreated sample to the ammonia solution to react to form the liquid to be detected specifically includes: adding the pretreated sample to the ammonia solution, performing a complexation reaction by magnetic stirring to form the liquid to be detected.

[0007] By carrying out complexation reaction by means of magnetic stirring, the copper oxide in the agglomerated state of polycrystalline nanoparticles can be dissolved, the interference of copper oxide on the detection of copper element can be reduced, and the detection accuracy of the copper element content in the positive electrode material can be maintained at a high level.

[0008] In one embodiment, adding the pretreated sample to an ammonia solution for reaction to form the test solution further comprises: adding ammonium salt to the ammonia solution; and reacting the pretreated sample with the ammonia solution containing the ammonium salt to form the test solution.

[0009] By adding ammonium salt to the ammonia solution, more NH 4+, promote the complexation reaction so that the copper and zinc in the pretreated sample are fully complexed, and maintain a high detection rate and accuracy for the copper and zinc content in the positive electrode material.

[0010] In one embodiment, before testing the liquid to be tested, the method further includes: concentrating the liquid to be tested; and testing the liquid to be tested specifically includes: testing the concentrated liquid to be tested.

[0011] By concentrating the liquid to be tested, the amount of solvent in the liquid to be tested is reduced, the copper and zinc content in the same volume of solution is increased, and the copper and zinc content of the concentrated solution is kept within the detection range of the detection equipment. The detection ability of the detection method for the copper and zinc content in the positive electrode material is improved, and the copper and zinc content in the positive electrode material can be detected at the ppb level.

[0012] In one embodiment, before adding the pretreated sample to the ammonia solution, the method further includes: washing the pretreated sample with water.

[0013] By washing the pretreated sample with water, the soluble substances in the pretreated sample are dissolved, the interference of soluble copper salts / zinc salts is reduced, and the detection accuracy of the copper and zinc content in the positive electrode material is improved.

[0014] In one embodiment, before wet-sieving the positive electrode material of the battery, the process further includes dry-sieving the positive electrode material.

[0015] A dry screening enrichment step is performed before wet screening, and the dry-screened powder can be reused in the production line, reducing material loss and saving costs. Due to the small particle size of the positive electrode material, it is easy to agglomerate during the dry screening process, which can easily cause substances other than elemental copper and zinc to remain on the sieve. Wet screening the oversize material after dry screening achieves secondary enrichment, reduces interference from soluble substances on the test, and helps improve the accuracy of the detection method for the copper and zinc content in the positive electrode material.

[0016] In one embodiment, testing the liquid to be tested specifically includes: testing the liquid to be tested using an inductively coupled plasma optical emission spectrometer.

[0017] The quantitative detection of the copper and zinc content in the test liquid is achieved by inductively coupled plasma emission spectrometry. The detection method is simple, highly sensitive and accurate.

[0018] In one embodiment, the pH value of the pretreated sample after adding the ammonia solution is 11-12, and the ammonia solution fully reacts with the copper-zinc particles in the pretreated sample obtained after wet screening, maintaining a high detection rate and detection accuracy for the content of copper-zinc particles in the positive electrode material.

[0019] In one embodiment, the ammonium salt comprises ammonium chloride; and / or, the amount of the ammonium salt added is 1 g to 2 g of the ammonium salt per 50 ml of the ammonia solution.

[0020] Ammonium chloride is added to the ammonia solution to provide more NH 4+ , promoting the complexation reaction. In addition, the Cl provided by ammonium chloride - It can also chemically react with copper / zinc, allowing the copper-zinc particles in the pretreated sample to fully react into an ionic state, maintaining a high detection rate and accuracy for the copper-zinc content in the positive electrode material. By designing the addition ratio of ammonium salt to ammonia solution as described above, the complexation reaction is promoted, the reaction rate is faster, and the copper-zinc particles in the pretreated sample obtained after wet sieving can fully react, maintaining a high detection rate and accuracy for the copper-zinc content in the positive electrode material.

[0021] In one embodiment, the positive electrode material includes at least one of a positive electrode active material, a conductive agent, a binder, and a second dispersant. The method for detecting the copper and zinc content in the battery material provided in the embodiments of the present application can detect the copper and zinc content of at least one of the positive electrode active material, the conductive agent, the binder, and the second dispersant.

[0022] In one embodiment, the positive electrode material has a Dv50 particle size greater than 10 μm. Prior to wet screening the positive electrode material, the method further includes pre-treating the positive electrode material, wherein the pre-treatment conditions include: a 10%-20% ascorbic acid aqueous solution at 40°C-60°C with magnetic stirring for 1-3 hours. Pre-treating the positive electrode material reduces the particle size to less than 10 μm. During wet screening, the screen retains copper and zinc particles in the positive electrode material, thereby improving recovery and, consequently, detection accuracy.

[0023] The above description is only an overview of the technical solution of the present application. In order to more clearly understand the technical means of the present application, it can be implemented in accordance with the contents of the specification. In order to make the above and other purposes, features and advantages of the present application more obvious and easy to understand, the specific implementation methods of the present application are listed below. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0025] Figure 1 1 is a flow chart of a method for detecting copper and zinc content in battery materials provided in the first embodiment of the present application;

[0026] Figure 2 2 is a comparative diagram showing the ratio of ammonia solution to ammonium chloride in a specific embodiment of the present application. DETAILED DESCRIPTION

[0027] In order to make the purpose, technical solution and effect of this application clearer and more specific, the following embodiments of the technical solution of this application will be described in detail with reference to the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of this application and are therefore only examples and are not intended to limit the scope of protection of this application.

[0028] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which this application belongs; the terms used herein are only for the purpose of describing specific embodiments and are not intended to limit this application; the terms "including" and "having" and any variations thereof in the specification and claims of this application and the above-mentioned figure descriptions are intended to cover non-exclusive inclusions.

[0029] In the description of the embodiments of the present application, the technical terms "first" and "second" are used only to distinguish different objects and should not be understood as indicating or implying relative importance or implicitly indicating the quantity, specific order, or primary and secondary relationship of the indicated technical features. In the description of the embodiments of the present application, the term "multiple" refers to more than two (including two), similarly, "multiple groups" refers to more than two (including two), and "multiple pieces" refers to more than two (including two), unless otherwise clearly and specifically defined.

[0030] References herein to "embodiments" mean that a particular feature, structure, or characteristic described in connection with the embodiments may be included in at least one embodiment of the present application. The appearance of this phrase in various places in the specification does not necessarily refer to the same embodiment, nor does it constitute an independent or alternative embodiment that is mutually exclusive of other embodiments. It is understood, both explicitly and implicitly, by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0031] In the description of the embodiments of this application, the term "and / or" is simply a description of the association relationship between associated objects, indicating that three relationships can exist. For example, A and / or B can represent the following three situations: A exists alone, A and B exist simultaneously, and B exists alone. In addition, the character " / " in this document generally indicates that the associated objects are in an "or" relationship.

[0032] Amounts, ratios, and other numerical values ​​are presented herein in a range format. It should be understood that such range format is used for convenience and brevity and should be interpreted flexibly to include not only the values ​​explicitly specified as range limits, but also all individual values ​​or sub-ranges encompassed within the range, as if each value and sub-range were explicitly specified.

[0033] If not otherwise specified, all steps of the present application may be performed sequentially, randomly, or in parallel, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially, or may include steps (a) and (b) performed simultaneously in parallel. For example, the method may further include step (c), indicating that step (c) may be added to the method in any order, for example, the method may include steps (a), (b), and (c), or may include steps (a), (c), and (b), or may include steps (c), (a), and (b), etc.

[0034] Lithium-ion batteries have been widely used due to their high voltage, light weight, long cycle life, lack of memory effect, and excellent safety. Lithium-ion batteries consist of a positive electrode, a negative electrode, a separator, and an electrolyte. During the battery's charge and discharge processes, active ions are inserted and removed between the positive and negative electrodes. The separator, located between the positive and negative electrodes, acts as a barrier. The electrolyte conducts ions between the positive and negative electrodes.

[0035] Among them, during the synthesis process of the positive electrode material of the lithium-ion battery, foreign matter will be introduced due to factors such as the introduction of raw materials and equipment wear. In particular, copper and zinc foreign matter (i.e., copper and zinc in elemental state) can easily cause self-discharge problems during the formation. Copper and zinc metal particles have begun to precipitate during the formation stage of the battery cell, and the precipitation rate is faster at high temperatures, causing the battery voltage drop per unit time to drop too quickly (i.e., a poor self-discharge K value phenomenon), resulting in a large capacity loss. Copper and zinc are continuously precipitated under high voltage, dissolved and deposited at the negative electrode until all are precipitated; after passing through the diaphragm, the copper ions are reduced to a dendritic state at the negative electrode, causing safety risks. Therefore, in order to ensure the good electrochemical performance and safety of lithium-ion batteries, it is necessary to detect and control the content of precipitated copper and zinc.

[0036] In view of this, an embodiment of the present application provides a method for detecting the copper and zinc content in a battery material, so as to detect the copper and zinc content with a high detection rate.

[0037] See also Figure 1 , Figure 1 Schematic diagram of the process of detecting the copper and zinc content in battery materials provided in the embodiments of the present application.

[0038] The method for detecting the copper and zinc content in the battery material provided in the embodiment of the present application specifically includes:

[0039] Step S01: wet-screening the positive electrode material of the battery, and collecting the material on the screen to obtain a pretreated sample; wherein the solution used in the wet-screening process includes water and a first dispersant.

[0040] Specifically, the content of copper and zinc foreign matter particles in the positive electrode material is low, and the distribution of copper and zinc foreign matter in the positive electrode material is characterized by random distribution. Due to the random distribution of copper and zinc foreign matter, a small test sample (for example, a test sample of several hundred grams) is not representative. The copper and zinc content in the test sample may be lower than the actual copper and zinc content in the positive electrode material. It is even possible that the test sample is a portion of the positive electrode material that does not contain copper and zinc foreign matter, affecting the detection probability and accuracy of copper and zinc.

[0041] The present application enriches the copper-zinc foreign matter particles in the test sample by wet screening the positive electrode material as the test sample, which can increase the amount of the test sample, thereby improving the closeness between the measurement result of the test sample and the actual copper-zinc content in the positive electrode material. In one embodiment, the test sample amount is 1kg-100kg, and the test sample amount is large, which is conducive to improving the probability of detection. The test sample amount can be 1kg, 5kg, 10kg, 20kg, 30kg, 40kg, 50kg, 60kg, 70kg, 80kg, 90kg, 100kg, etc., or a range consisting of any two of the above values, for example, 1kg-10kg, 10kg-100kg, 30kg-90kg, 60kg-100kg, etc. Exemplarily, the test sample amount is 1kg-100kg, and each batch of production lines is monitored once a day, which hardly affects production efficiency.

[0042] The solution used in the wet screening process includes water and a first dispersant. The copper-zinc elemental particles in the positive electrode material are insoluble in water and the first dispersant, and the elemental copper-zinc particles can be well screened out; at the same time, the solution used in the wet screening process can dissolve the soluble substances in the positive electrode material, wherein the soluble substances include soluble copper salts / zinc salts. The soluble substances pass through the screen along with the solution used in the wet screening, which reduces the interference of the soluble copper salts / zinc salts in the detection of the copper-zinc elemental content and improves the detection accuracy. The first dispersant can act on the positive electrode material to improve the agglomeration of the positive electrode material; specifically, by adding the first dispersant to the solution used in the wet screening process, the agglomeration of the positive electrode material on the screen during the wet screening process can be alleviated, thereby achieving a better wet screening effect. In addition, the solution used in the wet screening process includes water and the first dispersant, which is lower in cost than the use of ethanol for dispersion in the prior art.

[0043] In one embodiment, the mesh size of the screen used in the wet screening process in step S01 is 1000-1500 mesh. It should be noted that the mesh size of the screen can be selected according to the particle size of the positive electrode material. When the positive electrode material includes a positive electrode active material and the particle size of the positive electrode active material is less than or equal to 10 μm, a mesh size of 1000-1500 mesh is selected, which can screen out the elemental copper-zinc particles while having a high screening efficiency. The mesh size of the screen used in the wet screening process can be 1000 mesh, 1100 mesh, 1200 mesh, 1300 mesh, 1400 mesh, 1500 mesh, etc., or a range consisting of any two of the above values, for example, 1000 mesh-1200 mesh, 1100 mesh-1400 mesh, etc. Exemplarily, the mesh size of the screen can be 1000 mesh. Exemplarily, the mesh size of the screen can be 1200 mesh. Exemplarily, the mesh size of the screen can be 1500 mesh.

[0044] Alternatively, wet sieving can be performed using a hand sifter or a wet sifter.

[0045] In one embodiment, the first dispersant in step S01 comprises at least one of aqueous dispersant X3204 and aqueous dispersant D300. The first dispersant selected from the above ingredients effectively disperses the positive electrode material powder and reduces agglomeration during the wet sieving process. It should be noted that the first dispersant is not limited to aqueous dispersant X3204 or aqueous dispersant D300; any dispersant capable of reducing agglomeration during the wet sieving process is sufficient.

[0046] It should be noted that since the elemental copper and zinc content affects the electrochemical and safety performance of the battery, the purpose of the detection method provided in this application is to detect the elemental copper and zinc content, monitor the elemental copper and zinc content, and further monitor the electrochemical and safety performance of the battery. Before content detection, the test sample is wet-sieved. The solution used for wet sieve can dissolve soluble copper / zinc substances, such as soluble copper salts / zinc salts, and reduce the content of soluble copper / zinc substances in the test solution. The copper and zinc content obtained by testing the test solution in step S03 is closer to the actual elemental copper and zinc content.

[0047] Step S02: adding the pre-treated sample to an ammonia solution for reaction to form a liquid to be tested.

[0048] Specifically, the positive electrode material is wet-sieved, and the sieve material is collected as a pre-treated sample. The pre-treated sample includes copper and zinc elemental particles, and the copper and zinc react with the ammonia solution as follows:

[0049] Cu+NH3+O2+H2O→[Cu(NH3)4](OH)2

[0050] Zn+NH3+O2+H2O→[Zn(NH3)4](OH)2

[0051] It can be understood that copper / zinc reacts with ammonia water to form a complex reaction; the oxygen required for the complex reaction can be provided by air introduced into the solution by stirring, or can be oxygen introduced intentionally, as long as the complex reaction can occur.

[0052] By wet sieving, the elemental copper-zinc particles in the test sample are enriched, the interference of soluble copper-zinc (for example, copper salt / zinc salt) can be reduced, and a pre-treated sample is obtained. The ammonia solution in step S02 can disperse the pre-treated sample, and relative to the ammonia solution when not enriched, it is necessary to disperse the test sample, which reduces the consumption of ammonia solution in step S02, is beneficial to reducing waste liquid discharge, improves environmental protection, and the reaction device tends to miniaturization, is easy to operate, promotes reaction completely, and detection cost is relatively low. Exemplary, the test sample amount is 1kg-100kg, and the pre-treated sample after wet sieving enrichment is generally gram level or even milligram level, and required ammonia solution amount is less (for example, 50ml), which significantly reduces the consumption of ammonia solution, and is easy to operate, so that the pre-treated sample after enrichment and ammonia solution can fully mix and react.

[0053] Step S03: testing the liquid to be tested and obtaining the copper and zinc content in the liquid to be tested.

[0054] Since wet screening enrichment is performed before content detection in this application, the amount of ammonia solution used in the complexation reaction is relatively small, the amount of solvent in the liquid to be tested is also relatively small, and the concentration of complexed copper / zinc ions in the liquid to be tested is relatively large, making it easy to detect copper and zinc. The method for detecting the copper and zinc content in battery materials provided in the embodiments of this application can achieve the detection of ppb-level copper and zinc content.

[0055] The method for detecting the copper and zinc content in battery materials provided in the embodiments of the present application first wet-screens the positive electrode material to enrich the copper and zinc particles precipitated in the positive electrode material and reduce the interference of soluble copper salts / zinc salts. Then, after complexation reaction with an ammonia solution, a liquid to be tested is obtained. The liquid to be tested is tested to obtain the elemental copper and zinc content of the liquid to be tested, and then the specific content of copper and zinc precipitated in the positive electrode material is obtained. The detection method is simple and easy, with a high detection rate and high accuracy.

[0056] In one embodiment, in step S02, adding the pretreated sample to the ammonia solution to react and form the test solution specifically includes: adding the pretreated sample to the ammonia solution and performing a complexation reaction via magnetic stirring to form the test solution. The complexation reaction via magnetic stirring can dissolve copper oxide in the aggregated state of the polycrystalline nanoparticles, thereby reducing the copper oxide content in the test solution. The detected copper content is closer to the actual elemental copper content of the test sample, thereby maintaining a high degree of detection accuracy for the elemental copper content in the positive electrode material.

[0057] Optionally, the stirring speed is 700r / min-800r / min; and / or the reaction time is 1h-2h. By selecting the stirring speed of 700r / min-800r / min, the copper-zinc particles of the pretreated sample are dissolved more fully, especially the copper oxide can be fully dissolved, which is beneficial to maintain a high detection accuracy for the content of copper element in the positive electrode material. By selecting the reaction time of 1h-2h, the copper-zinc particles of the pretreated sample are dissolved more fully, especially the copper oxide can be fully dissolved, and the copper element content in the positive electrode material maintains a high detection accuracy. The stirring speed can be 700r / min, 710r / min, 720r / min, 730r / min, 740r / min, 750r / min, 760r / min, 770r / min, 780r / min, 790r / min, 800r / min, etc., or a range consisting of any two of the above values. The reaction time can be 1 h, 1.1 h, 1.2 h, 1.3 h, 1.4 h, 1.5 h, 1.6 h, 1.7 h, 1.8 h, 1.9 h, 2 h, etc., or a range consisting of any two of the above values.

[0058] In one embodiment, in step S02, adding the pretreated sample to the ammonia solution to react to form the test solution further comprises: adding ammonium salt to the ammonia solution; and reacting the pretreated sample with the ammonia solution to form the test solution. By adding ammonium salt to the ammonia solution, more NH 4+ , promote the complexation reaction so that the copper-zinc particles in the pretreated sample are fully complexed, and maintain a high detection rate and detection accuracy for the content of copper-zinc particles in the positive electrode material.

[0059] Optionally, the ammonium salt includes ammonium chloride; and / or, the amount of the ammonium salt added is 1 g to 2 g of the ammonium salt per 50 ml of the ammonia solution.

[0060] Ammonium chloride is added to the ammonia solution to provide more NH 4+ , promoting the complexation reaction. In addition, the Cl provided by ammonium chloride - It can also react chemically with copper / zinc, so that the copper / zinc particles in the pretreated sample are fully reacted into ions, maintaining a high detection rate and accuracy for the copper / zinc content in the positive electrode material. It should be noted that ammonium salts can also be ammonium sulfate, ammonium carbonate, etc., which can provide NH 4+ The amount of ammonium salt added per 50 ml of ammonia solution can be 1 g, 1.1 g, 1.2 g, 1.3 g, 1.4 g, 1.5 g, 1.6 g, 1.7 g, 1.8 g, 1.9 g, 2 g, etc., or a range consisting of any two of the above values.

[0061] By adjusting the ratio of ammonium salt to ammonia solution as described above, the complexation reaction is promoted, the reaction rate is fast, the copper-zinc particles in the pretreated sample obtained after wet sieving can fully react, the pH tends to be stable, and the detection rate and accuracy of the copper-zinc particles in the positive electrode material are maintained at a high level. For example, Figure 2 As shown, Figure 2 The comparison chart of the ratio of ammonia solution to ammonium chloride in the specific embodiment of the present application shows that when the ammonium salt is ammonium chloride, 1g-2g of ammonium chloride is added to every 50ml of ammonia solution, and the recovery rate is greater than 90%, maintaining a high detection accuracy. It should be noted that Figure 2 In the comparison diagram shown, except for the different ratios of ammonia solution and ammonium chloride, all other conditions are the same. Figure 2 The recovery rate shown in is the spiked recovery rate. For details, please refer to the steps of Example 4 introduced later. The difference from Example 4 is the amount of ammonia solution and ammonium chloride added.

[0062] In one embodiment, before performing step S03 , that is, before testing the liquid to be tested, the process further includes: concentrating the liquid to be tested; and testing the liquid to be tested specifically includes: testing the concentrated liquid to be tested.

[0063] Specifically, by concentrating the liquid to be tested, reducing the amount of solvent in the liquid to be tested, increasing the copper and zinc content in the same volume of solution, keeping the copper and zinc content of the concentrated liquid to be tested within the detection range of the detection equipment, and then performing content testing, the detection method's ability to detect the copper and zinc content in the positive electrode material is improved. Even if the copper and zinc particle content in the positive electrode material is at the ppb level, it can be detected.

[0064] Exemplarily, when the detection equipment uses an inductively coupled plasma emission spectrometer, the copper and zinc content of the concentrated liquid to be detected is within the detection range of the inductively coupled plasma emission spectrometer equipment by concentrating the liquid to be detected; in addition, the inductively coupled plasma emission spectrometer test requires a neutral or acidic solution. By concentrating the liquid to be detected, the ammonia water in the concentrated liquid to be detected is less, and the acid consumption can be reduced on the basis of meeting the testing requirements of the inductively coupled plasma emission spectrometer. Exemplarily, the amount of the test sample is 1kg-100kg, and the pretreated sample after wet sieving enrichment is usually in the gram level or even milligram level. The amount of ammonia solution is usually 50ml to keep the complexation reaction fully carried out. By concentrating the liquid to be detected, the amount of solvent can be reduced to ten milliliters or less, and then acid (for example, nitric acid) is added to make the volume constant, and then the inductively coupled plasma emission spectrometer is tested, which helps to reduce the acid consumption.

[0065] Exemplarily, the test solution is concentrated by heating or distillation. This concentration method is simple and easy to perform and increases the content of the copper / zinc complex in the same volume of solution. Exemplarily, the test solution is concentrated by high-temperature evaporation. Exemplarily, the test solution is concentrated by a rotary evaporator or other distillation equipment. Exemplarily, the test solution is concentrated by vacuum heating. Exemplarily, the test solution is concentrated by high-temperature heating (180-300°C).

[0066] In one embodiment, before performing step S02 , that is, before adding the pretreated sample to the ammonia solution, the method further includes: washing the pretreated sample with water.

[0067] Specifically, the pretreated sample is rinsed with ultrapure water or deionized water to dissolve soluble substances, such as soluble copper salts / zinc salts, to reduce the interference of copper salts / zinc salts on the detection of copper / zinc elemental content. The detected copper and zinc content is closer to the actual elemental copper and zinc content of the test sample, which is beneficial to maintain a high detection accuracy for the elemental copper and zinc content in the positive electrode material.

[0068] Optionally, the pre-treated sample is rinsed with water multiple times. Exemplarily, the pre-treated sample is rinsed with water twice.

[0069] Optionally, the pre-treated sample is rinsed into a beaker, stirred, and then filtered onto a filter membrane to achieve water washing of the pre-treated sample.

[0070] In one embodiment, before step S01 , that is, before wet-screening the positive electrode material of the battery, the method further includes: dry-screening the positive electrode material of the battery.

[0071] It can be understood that a dry screening enrichment is performed before wet screening, and the powder screened by dry screening can be reused in the production line, reducing material loss and saving costs. Since the particle size of the positive electrode material is small, it is easy to agglomerate during the dry screening process, which easily causes substances other than elemental copper and zinc to remain on the sieve. The wet screening is used to perform a secondary elemental copper and zinc particle enrichment on the dry screened material, reducing the consumption of ammonia solution in step S02, which is conducive to improving the detection accuracy of the detection method for the copper and zinc content in the positive electrode material.

[0072] Optionally, the powder of the positive electrode material is dry-sieved using a rotary vibrating sieve, an automated sieve, or an ultrasonic vibrating sieve.

[0073] Optionally, the mesh size of the screen used in the dry screening process is 800-1000 mesh. It should be noted that the mesh size of the screen can be selected according to the particle size of the positive electrode material. When the positive electrode material includes a positive electrode active material, and the particle size of the positive electrode active material is less than or equal to 10 μm, a mesh size of 800-1000 mesh is selected, which can screen out the elemental copper-zinc particles while having a higher screening efficiency. Exemplarily, the mesh size of the screen can be 1000 mesh. Exemplarily, the mesh size of the screen can be 800 mesh. Exemplarily, the mesh size of the screen can be 900 mesh.

[0074] For example, when the positive electrode active material is a ternary material or lithium iron phosphate, the amount of the test sample for the copper-zinc particle content test may be 10 kg to 100 kg, and dry screening is performed first, and then wet screening is performed.

[0075] In one embodiment, in step S03 , testing the liquid to be tested specifically includes: testing the liquid to be tested using an inductively coupled plasma optical emission spectrometer.

[0076] Specifically, inductively coupled plasma optical emission spectrometry (ICP-OES) can achieve quantitative detection of the copper and zinc content in the test solution. The test results of the copper and zinc content in the test sample are:

[0077]

[0078]

[0079] When only wet screening is performed, the sample mass refers to the amount of wet-screened cathode material sample tested. When dry screening is performed before wet screening, the sample mass refers to the amount of dry-screened cathode material sample tested. V refers to the constant volume when performing inductively coupled plasma emission spectrometry testing. The Cu / Zn ratio on the right side of the formula refers to the Cu / Zn content of the test solution as measured by the inductively coupled plasma emission spectrometer. The Cu / Zn ratio on the left side of the formula refers to the Cu / Zn content of the test sample after either dry or wet screening.

[0080] It should be noted that this application is not limited to using inductively coupled plasma optical emission spectrometry to detect the copper and zinc content in the test liquid. Other methods can also be used to detect the copper and zinc content in the test liquid. In the embodiment of this application, inductively coupled plasma optical emission spectrometry is used to quantitatively detect the copper and zinc content in the test liquid. The detection method is simple, highly sensitive, and highly accurate.

[0081] In one embodiment, in step S02, the pH value of the pretreated sample is 11-12 after the ammonia solution is added. Through the above design, the ammonia solution fully reacts with the copper-zinc particles in the pretreated sample obtained after wet screening, and the recovery rate is above 90%, maintaining a high detection rate and detection accuracy for the content of copper-zinc particles in the positive electrode material. The pH value of the pretreated sample after the ammonia solution is added is 11-12, the system is stable, and is sufficient to dissolve the copper-zinc particles in the pretreated sample. Exemplarily, the pH value of the pretreated sample after the ammonia solution is added is 11. Exemplarily, the pH value of the pretreated sample after the ammonia solution is added is 12. Exemplarily, the pH value of the pretreated sample after the ammonia solution is added is between 11 and 12.

[0082] Optionally, 10ml-50ml of ammonia solution is added to every 0.01g-10g of pretreated sample, so that the ammonia solution fully reacts with the copper-zinc particles in the pretreated sample obtained after wet sieving, and the detection rate and detection accuracy of the copper-zinc particles in the positive electrode material are maintained at a high level. Exemplarily, 50ml of ammonia solution is added to every 1g of pretreated sample, and the mass concentration of the ammonia solution is 25%-28%. For example, 50ml of ammonia solution is added to every 0.01g of pretreated sample, and the concentration of the ammonia solution is 25%-28%. For example, 50ml of ammonia solution is added to every 0.1g of pretreated sample, and the concentration of the ammonia solution is 25%-28%. For example, 50ml of ammonia solution is added to every 10g of pretreated sample, and the concentration of the ammonia solution is 25%-28%. For example, 50ml of ammonia solution is added to every 5g of pretreated sample, and the concentration of the ammonia solution is 25%-28%. Exemplarily, 10 ml of ammonia solution is added to every 5 g of pre-treated sample, and the concentration of ammonia solution is 25%-28%. Exemplarily, 25 ml of ammonia solution is added to every 5 g of pre-treated sample, and the concentration of ammonia solution is 25%-28%.

[0083] In one embodiment, the positive electrode material in step S01 includes at least one of a positive electrode active material, a conductive agent, a binder, and a second dispersant. The detection method provided in the embodiment of the present application can detect the copper and zinc content of at least one of the positive electrode active material, the conductive agent, the binder, and the second dispersant.

[0084] Optionally, the binder includes polyvinylidene fluoride (PVDF).

[0085] Optionally, the second dispersant may be an emulsion dispersant or a solution dispersant.

[0086] Optionally, the positive electrode active material includes a ternary material or lithium iron phosphate (LiFePO4, LFP) or lithium manganese iron phosphate (LiMn (1-x) Fe xPO4, LMFP). Ternary materials include LiNi x Co y Mn z O2, wherein x+y+z=1, 0.3≤x≤0.98, 0.01≤y≤0.3, 0.01≤z≤0.4; the value of x is, for example but not limited to, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 0.98, etc.; the value of y is, for example but not limited to, 0.01, 0.05, 0.1, 0.2, 0.25, 0.3, etc.; the value of z is, for example but not limited to, 0.01, 0.05, 0.2, 0.25, 0.3, 0.35, 0.4, etc. Exemplary, ternary materials include N5C2M3(LiNi 0.5 Co 0.2 Mn 0.3 02) N6C2M2(LiNi 0.6 Co 0.2 Mn 0.2 02) N7C1M2(LiNi 0.7 Co 0.1 Mn 0.2 02) at least one of.

[0087] Optionally, when the positive electrode active material is a ternary material, the amount of the test sample for the copper-zinc particle content test may be 10kg-100kg, or 1kg-10kg.

[0088] Optionally, when the positive electrode active material is lithium iron phosphate, the amount of the test sample for the copper-zinc particle content test may be 1 kg to 10 kg.

[0089] In one embodiment, the Dv50 particle size of the positive electrode material is less than or equal to 10 μm. Exemplarily, a 1200 mesh screen (15-20 μm) can be used for wet screening. It should be noted that the Dv50 particle size of the positive electrode material is less than or equal to 10 μm, and a 1000-1500 mesh screen is used for wet screening, so that the material can pass through the screen while keeping the copper and zinc particles on the screen.

[0090] In one embodiment, the Dv50 particle size of the positive electrode active material is 5 μm-10 μm. The Dv50 particle size of the positive electrode active material can be 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, etc., or a range consisting of any two of the above values. Exemplarily, the Dv50 particle size of the ternary material is 3-5 μm, 8-10 μm. Exemplarily, the Dv50 particle size of the lithium iron phosphate material is 0.5 μm-1.5 μm, 1.0 μm-2.0 μm, or 4.0 μm-10.0 μm.

[0091] In one embodiment, the positive electrode material has a Dv50 particle size greater than 10 μm and requires pretreatment. The treatment conditions include a 10%-20% ascorbic acid aqueous solution at 40°C-60°C for 1-3 hours with magnetic stirring. Compared to directly wet-sieving positive electrode materials with a Dv50 particle size greater than 10 μm using a larger mesh sieve, pre-treating the positive electrode material to reduce the particle size to less than 10 μm allows for wet-sieving using a 1000-1500 mesh sieve. This reduces the amount of copper and zinc particles that slip through the sieve, ensuring that the copper and zinc particles remain on the sieve, thereby improving recovery and, consequently, detection accuracy.

[0092] In one embodiment, when the positive electrode material includes a positive electrode active material, and the positive electrode active material includes a ternary material, 2-4 kg of ultrapure water or deionized water (DI water) and 10 g of a non-ionic polymer dispersant X3204 are used per kg of the ternary material for wet sieving to separate elemental copper and zinc particles while eliminating dissolution interference from soluble copper and zinc substances (e.g., copper salts / zinc salts). Exemplary amounts of ultrapure water or deionized water used during wet sieving per kg of the ternary material can be 2.0 kg, 2.1 kg, 2.2 kg, 2.3 kg, 2.4 kg, 2.5 kg, 2.6 kg, 2.7 kg, 2.8 kg, 2.9 kg, 3 kg, 3.1 kg, 3.2 kg, 3.3 kg, 3.4 kg, 3.5 kg, 3.6 kg, 3.7 kg, 3.8 kg, 3.9 kg, 4 kg, or the like, or a range consisting of any two of the foregoing values.

[0093] In one embodiment, the positive electrode material includes a positive electrode active material, and when the positive electrode active material includes a lithium iron phosphate material, 4-5 kg ​​of ultrapure water or deionized water (DI water) and 50 g of a non-ionic polymer dispersant X3204 are used for wet sieving per kg of the lithium iron phosphate material to separate elemental copper and zinc particles while eliminating dissolution interference from soluble copper and zinc substances (e.g., copper salts / zinc salts). For example, the amount of ultrapure water or deionized water used during the wet sieving process per kg of the lithium iron phosphate material can be 4 kg, 4.1 kg, 4.2 kg, 4.3 kg, 4.4 kg, 4.5 kg, 4.6 kg, 4.7 kg, 4.8 kg, 4.9 kg, 5 kg, or the like, or a range consisting of any two of the foregoing values.

[0094] In one embodiment, the positive electrode material includes a positive electrode active material, which is a ternary material. 10 kg to 100 kg of the ternary material is sequentially dry-sieved and wet-sieved to enrich the copper and zinc particles in the ternary material to form a pretreated sample. The pretreated sample is then subjected to a complexation reaction with an ammonia solution to form a test solution. The test solution is then concentrated, and the copper and zinc content is then tested.

[0095] In one embodiment, the positive electrode material includes a positive electrode active material, which is a ternary material. 1 kg to 10 kg of the ternary material is wet-sieved to concentrate the copper and zinc particles in the ternary material to form a pretreated sample. The pretreated sample is then subjected to a complexation reaction with an ammonia solution to form a test solution. The test solution is then concentrated, and the copper and zinc content is then tested.

[0096] In one embodiment, the positive electrode material includes a positive electrode active material, which is a lithium iron phosphate material. 1 kg to 10 kg of the lithium iron phosphate material is wet-sieved to concentrate copper and zinc particles in the lithium iron phosphate material to form a pretreated sample. The pretreated sample is then subjected to a complexation reaction with an aqueous ammonia solution to form a test solution. The test solution is then concentrated, and the copper and zinc content is then tested.

[0097] The beneficial effects of the present application are further illustrated below with reference to the examples.

[0098] In order to make the technical problems, technical solutions and beneficial effects solved by the embodiments of the present application clearer, the following will be further described in detail with reference to the embodiments and drawings. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. The following description of at least one exemplary embodiment is actually only illustrative and is in no way intended to limit the present application and its applications. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0099] Example 1:

[0100] Step 1: Use a rotary vibrating sieve to separate 100 kg of lithium nickel cobalt manganese oxide Li (Ni 0.5 Co 0.2 Mn 0.3 ) The O2 material was added step by step and vibrated on an 800-mesh sieve, and the material on the sieve was collected.

[0101] Step 2: Wet-sieve the oversize material on a 1200 mesh sieve, add 10 g of non-ionic polymer dispersant X3204 to 3.5 kg of deionized water and stir with a glass rod to dissolve, pour the lithium nickel cobalt manganese oxide material in step 1 and stir and disperse with a glass rod, pour the mixed slurry onto the sieve in several times and stir manually, and finally add water to wash until the particles are not significantly reduced, tilt the sieve to rinse the oversize material into a 500 ml beaker, then place the sieve in an ultrasonic machine and sonicate three times, rinse the particles on the sieve into the beaker again, and filter the solution containing the oversize material in the beaker onto the filter membrane.

[0102] Step 3: Place the filter membrane in a 150ml beaker, use a measuring cylinder to take 50ml of deionized water and add it to the beaker, stir with a glass rod; filter the solution in the beaker onto the filter membrane.

[0103] Step 4: Place the filter membrane in a 150ml beaker, use a graduated cylinder to take 50ml of ammonia solution (mass concentration is 25%-28%), and weigh 1.00g of ammonium chloride powder on weighing paper and pour it into the beaker.

[0104] Step 5: Place the beaker on a magnetic stirrer, add a stirring magnet, seal the beaker with a sealing film, and stir at a speed of 720 r / min (power 100%) for 1 hour.

[0105] Step 6: Use a 0.45μm water filter membrane to completely extract the filtrate, add a small amount of water to the beaker and wash it twice, and filter pure water with a vacuum filtration device and wash it twice.

[0106] Step 7: After filtration, place the conical flask on a heating plate at 300°C and evaporate to about 10 ml. Remove the conical flask and place it in a dry place to cool.

[0107] Step 8: Transfer the evaporated liquid to a 50ml volumetric flask and add 2ml of nitric acid to the volume using a disposable plastic dropper;

[0108] Step 9: Use inductively coupled plasma optical emission spectrometry (ICP-OES) to test the copper and zinc content in the filtrate. Input the sample mass and constant volume, and record the experimental results Cu (ppb) and Zn (ppb).

[0109]

[0110]

[0111] The difference between the steps of Example 2 and Example 1 is that step 1 is omitted and subsequent operations are performed according to steps 2-9 in Example 1.

[0112] The steps of Example 3 differ from those of Example 1 in that: Step 1 and Step 3 are omitted; Step 1 is not performed and Step 2 is performed directly; after Step 2, subsequent operations are performed directly according to Steps 4-9 in Example 1.

[0113] The steps of Example 4 differ from those of Example 1 in that Steps 1 to 3 are omitted, and Step 4 is performed directly. Specifically, Step 4 comprises the following steps: 1 g of oversize (the material residue after the ammonia complexation test is collected and dried), 0.0109 g of Cu powder, and 0.0130 g of Zn powder are weighed, 50 ml of ammonia solution (with a mass concentration of 25%-28%) is taken using a graduated cylinder, and 1.00 g of ammonium chloride powder is weighed on weighing paper and poured into a beaker. Subsequent operations are then performed according to Steps 5-9 of Example 1. It should be noted that the 1 g of oversize can be the filter residue on the filter membrane after Step 6 in any of Examples 1 to 3, i.e., the material residue after the ammonia complexation test. The amount of copper and zinc contained in this residue is very small, and can be considered to be almost absent.

[0114] The steps of Example 5 differ from those of Example 4 in that 0.0109 g of Cu powder in Step 4 is replaced by 0.0119 g of CuO, and 0.0130 g of Zn powder is replaced by 0.0131 g of ZnO.

[0115] Table 1 Test results of Examples 1-3

[0116] Example Ammonia solution / ml Speed / (r / min) Duration / h Cu(ppb) Zn(ppb) 1 50 720 1 1.1 2.3 2 50 720 1 0.6 1.3 3 50 720 1 0.8 1.7

[0117] Table 2 Test results of Examples 4-5

[0118]

[0119] As shown in Example 2, the detection method provided by this application can achieve the detection of copper-zinc particle content in the positive electrode material at the ppb level even if the "dry screening" step is omitted. As shown in Example 3, the detection method provided by this application can achieve the detection of copper-zinc particle content in the positive electrode material at the ppb level even if the "dry screening" and "water washing" steps are omitted.

[0120] It can be seen from Examples 4 and 5 that the detection method provided in the present application performs spiked detection, and the copper spiked recovery rate is greater than 90% or even greater than 100%, the zinc spiked recovery rate is greater than 90% or even greater than 100%, and the copper oxide spiked recovery rate is about 10%, which can significantly reduce the interference of copper oxide on the copper content detection results.

[0121] The above description is only an implementation method of the present application and does not limit the patent scope of the present application. Any equivalent structure or equivalent process transformation made using the contents of the description and drawings of this application, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present application.

Claims

1. A method for detecting the copper and zinc content in battery materials, characterized in that: include: Wet-screening the positive electrode material of the battery and collecting the sieve material to obtain a pretreated sample; wherein the solution used in the wet-screening process includes water and a first dispersant; adding the pretreated sample into an ammonia solution to react and form a liquid to be tested; The liquid to be detected is detected, and the copper and zinc content in the liquid to be detected is obtained.

2. The method for detecting the copper and zinc content in battery materials according to claim 1, characterized in that: The step of adding the pretreated sample to an ammonia solution for reaction to form a liquid to be tested specifically includes: The pretreated sample is added to the ammonia solution, and a complexation reaction occurs through magnetic stirring to form the liquid to be tested.

3. The method for detecting the copper and zinc content in battery materials according to claim 1 or 2, characterized in that: The step of adding the pretreated sample to an ammonia solution for reaction to form a liquid to be tested further comprises: adding an ammonium salt to the aqueous ammonia solution; The pretreated sample reacts with the ammonia solution added with the ammonium salt to form the liquid to be tested.

4. The method for detecting the copper and zinc content in battery materials according to any one of claims 1 to 3, characterized in that: Before the test liquid is tested, the method further includes: concentrating the liquid to be tested; The testing of the liquid to be tested specifically includes: The concentrated liquid to be tested is tested.

5. The method for detecting the copper and zinc content in battery materials according to any one of claims 1 to 4, characterized in that: Before adding the pre-treated sample to the ammonia solution, the method further comprises: The pretreated sample was washed with water.

6. The method for detecting the copper and zinc content in battery materials according to any one of claims 1 to 5, characterized in that: Before wet screening the positive electrode material of the battery, the method further comprises: The positive electrode material is dry-sieved.

7. The method for detecting the copper and zinc content in battery materials according to any one of claims 1 to 6, characterized in that: The testing of the liquid to be tested specifically includes: The liquid to be tested is tested using an inductively coupled plasma optical emission spectrometer.

8. The method for detecting the copper and zinc content in battery materials according to any one of claims 1 to 7, characterized in that: The pH value of the pretreated sample after adding the ammonia solution is 11-12.

9. The method for detecting the copper and zinc content in battery materials according to any one of claims 3 to 8, characterized in that: The ammonium salt includes ammonium chloride; and / or, the amount of the ammonium salt added is 1g-2g of the ammonium salt per 50ml of the ammonia solution.

10. The method for detecting the copper and zinc content in battery materials according to any one of claims 1 to 9, characterized in that: The positive electrode material includes at least one of a positive electrode active material, a conductive agent, a binder, and a second dispersant.

11. The method for detecting the copper and zinc content in battery materials according to any one of claims 1 to 10, characterized in that: The Dv50 particle size of the positive electrode material is greater than 10 μm; and before wet screening the positive electrode material of the battery, the method further comprises: The positive electrode material is pretreated under the following conditions: 10%-20% ascorbic acid aqueous solution, at 40° C.-60° C., and magnetically stirred for 1 h-3 h.

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