Method for detecting magnetic metal particles in battery positive electrode material and application thereof

Abstract

The invention discloses a method for detecting magnetic metal particles in a battery positive electrode material and application of the method, and the method comprises the following steps: mixing and stirring a positive electrode powder material, a solvent and a magnetic adsorption part, so that the magnetic metal particles in the positive electrode powder material are adsorbed on the surface of the magnetic adsorption part; collecting coarse magnetic metal particles on the surface of the magnetic adsorption part; the coarse magnetic metal particles and acid liquor are mixed and placed in a container, the side portion of the container is sleeved with an external magnetic ring, the container is placed on a ball mill to roll, and the external magnetic ring adsorbs the magnetic metal particles; pouring out the liquid in the container, taking down the external magnetic ring, and collecting the magnetic metal particles on the inner wall of the container to obtain a magnetic metal particle suspension; carrying out suction filtration and drying on the magnetic metal particle suspension to obtain magnetic metal particles; and detecting and analyzing the magnetic metal particles, and calculating the total number of the magnetic metal particles. Therefore, the test accuracy and the test efficiency of the number of the magnetic metal particles in the battery positive electrode material are improved.

Description

Technical Field

[0001] The present application belongs to the technical field of battery material detection, and specifically relates to a method for detecting magnetic metal particles in a battery positive electrode material and its application. Background Art

[0002] As the most expensive and critical component in the battery preparation process, the performance of the positive electrode material of lithium-ion batteries plays a vital role. Magnetic metal particles will inevitably be introduced into the production and preparation process of the positive electrode material and its raw materials. The presence of these magnetic metal particles will reduce the specific capacity and energy density of the positive electrode material, resulting in poor battery storage performance. Some magnetic metal particles are even easy to dissolve in the electrolyte, causing a series of side reactions, affecting the service life and consistency of lithium-ion batteries. In addition, magnetic metal particles will grow with agglomerates to form edges or spikes, which can easily pierce the battery separator during movement between the positive and negative electrodes of the battery, causing the battery to self-discharge after short circuit, causing the battery to heat up, burn, or even explode, affecting the safety performance of lithium-ion batteries during use. Therefore, it is very important to detect and monitor magnetic metal particles in the positive electrode materials of lithium-ion batteries.

[0003] In the prior art, the methods for analyzing and detecting the number and particle size of magnetic metal particles in powder materials have the following problems: 1. The process of extracting magnetic substances from materials requires multiple barrel changes and long-term adsorption. It often takes 2h to 2.5h to test a sample, which is time-consuming and has low test efficiency. 2. The detection process requires multiple barrel changes and complicated manual cleaning processes. Some small magnetic metal particles with weak adsorption force are easily lost during the detection process, affecting the extraction rate of magnetic metal particles and the detection accuracy. Summary of the invention

[0004] The present application aims to solve at least one of the technical problems in the related art to a certain extent. To this end, the purpose of the present application is to propose a method for efficiently and accurately detecting the number of magnetic metal particles in the positive electrode material of a battery, so as to achieve accurate monitoring of the magnetic metal particles in the positive electrode material.

[0005] In one aspect of the present application, the present application proposes a method for detecting magnetic metal particles in a positive electrode material of a battery. According to an embodiment of the present application, the method comprises:

[0006] (1) mixing and stirring a positive electrode powder material, a first solvent, and a magnetic adsorbent so that magnetic metal particles in the positive electrode powder material are adsorbed on the surface of the magnetic adsorbent;

[0007] (2) collecting coarse magnetic metal particles on the surface of the magnetic adsorbent;

[0008] (3) mixing the coarse magnetic metal particles with an acid solution and placing the mixture in a container, wherein at least a portion of the side surface of the container is covered with an external magnetic ring, and the container is placed on a first ball mill and rolled so that the external magnetic ring can adsorb the magnetic metal particles;

[0009] (4) pouring out the liquid in the container, removing the external magnetic ring, and collecting the magnetic metal particles on the inner wall of the container to obtain a magnetic metal particle suspension;

[0010] (5) filtering the magnetic metal particle suspension and drying it to obtain magnetic metal particles;

[0011] (6) Detect and analyze the number and size of magnetic metal particles, and calculate the total number of magnetic metal particles according to the formula.

[0012] According to the detection method of magnetic metal particles in the positive electrode material of the battery of the embodiment of the present application, by reducing the number of barrel changes during the extraction of magnetic metal particles, the extraction steps are reduced, the extraction time is shortened, and the test efficiency is improved while ensuring that the metal particles are accurately extracted. At the same time, by reducing the number of barrel changes, the loss of magnetic metal particles caused by multiple barrel changes is reduced, and the test accuracy is improved. In addition, the magnetic metal particle suspension after the magnetic metal particles are extracted and collected is directly filtered to replace multiple manual cleanings, reduce the time-consuming manual operation, and avoid the loss of some small magnetic metal particles with weak adsorption force caused by manual cleaning operations, thereby improving the efficiency and accuracy of the test.

[0013] In addition, the method for detecting magnetic metal particles in the positive electrode material of a battery according to the above embodiment of the present application may also have the following additional technical features:

[0014] In some embodiments of the present application, in step (1), the positive electrode powder material, the first solvent and the magnetic adsorbent are placed in a non-magnetic barrel, mixed and stirred, the non-magnetic barrel is sealed, and the non-magnetic barrel is placed on a second ball mill and rolled so that the magnetic metal particles in the positive electrode powder material are adsorbed on the surface of the magnetic adsorbent.

[0015] In some embodiments of the present application, in step (1), the rotation speed of the second ball mill is 20 Hz to 100 Hz, and the time is 5 min to 20 min.

[0016] In some embodiments of the present application, in step (1), the magnetic adsorption component includes a magnetic rod and a non-magnetic tube sleeved on the surface of the magnetic rod, the length of the magnetic rod is 200mm~300mm, the diameter of the magnetic rod is 20mm~30mm, the magnetic field strength of the magnetic rod is 5000GS~7000GS, and the wall thickness of the non-magnetic tube is 0.1mm~0.5mm.

[0017] In some embodiments of the present application, step (2) includes: removing the magnetic rod, flushing the outer wall of the non-magnetic tube with a second solvent, and scraping the outer wall of the non-magnetic tube with a non-magnetic blade to collect coarse magnetic metal particles on the surface of the magnetic adsorbent.

[0018] In some embodiments of the present application, the acid solution includes HCl solution and HNO 3 At least one of the solutions; and / or, the mass concentration of the acid solution is 10% to 30%.

[0019] In some embodiments of the present application, in step (3), the coarse magnetic metal particles are mixed with the acid solution and ultrasonically placed in the container; and / or, in step (3), the rotation speed of the first ball mill is 20 Hz to 100 Hz, and the time is 25 min to 40 min; and / or, in step (3), the magnetic field strength of the external magnetic ring is 5000 GS to 7000 GS.

[0020] In some embodiments of the present application, in step (4), the liquid in the container is poured out, the external magnetic ring is removed, and the magnetic metal particles on the inner wall of the container are rinsed with a third solvent to obtain a magnetic metal particle suspension.

[0021] In some embodiments of the present application, in step (5), the pore size of the filter membrane used for the filtration is less than 4.5μm to 5.5μm; and / or, in step (6), the instrument automatically reads the number of particles in the ranges of particle sizes >200μm, 150μm to 200μm, 100μm to 150μm, 50μm to 100μm, and 25μm to 50μm, and the total number of magnetic metal particles in 1kg of battery positive electrode material is calculated according to the following formula: The total number of magnetic metal particles in 1kg of battery positive electrode material = (the number of particles with a particle size of 25μm to 50μm) / 2+(the number of particles with a particle size of 50μm to 100μm) / 2+(the number of particles with a particle size of 100μm to 150μm)+(the number of particles with a particle size of 150μm to 200μm)+(the number of particles with a particle size >200μm).

[0022] In the second aspect of the present application, the present application proposes an application of the above embodiment method in the preparation process of battery positive electrode materials. It should be noted that the features and advantages described above for the detection method of magnetic metal particles in battery positive electrode materials are also applicable to the application of this method in the preparation process of battery positive electrode materials, specifically, the test accuracy and test efficiency of the number of magnetic metal particles in battery positive electrode materials are improved.

[0023] Additional aspects and advantages of the present application will be given in part in the description below, and in part will become apparent from the description below, or will be learned through the practice of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The above and / or additional aspects and advantages of the present application will become apparent and easily understood from the description of the embodiments in conjunction with the following drawings, in which:

[0025] Figure 1 A schematic diagram of the process of the method for detecting magnetic metal particles in the positive electrode material of a battery of the present application. DETAILED DESCRIPTION

[0026] Embodiments of the present application are described in detail below, and examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present application, and should not be construed as limiting the present application.

[0027] In one aspect of the present application, the present application proposes a method for detecting magnetic metal particles in a positive electrode material of a battery. Figure 1 The method includes: S100: mixing and stirring a positive electrode powder material, a first solvent and a magnetic adsorbent so that the magnetic metal particles in the positive electrode powder material are adsorbed on the surface of the magnetic adsorbent; S200: collecting coarse magnetic metal particles on the surface of the magnetic adsorbent; S300: mixing the coarse magnetic metal particles with an acid solution and placing them in a container, wherein at least part of the side surface of the container is covered with an external magnetic ring, and the container is placed on a first ball mill and rolled so that the external magnetic ring adsorbs the magnetic metal particles; S400: pouring out the liquid in the container, removing the external magnetic ring, collecting the magnetic metal particles on the inner wall of the container, and obtaining a magnetic metal particle suspension; S500: filtering the magnetic metal particle suspension, drying it, and obtaining magnetic metal particles; S600: detecting and analyzing the number and size of the magnetic metal particles, and calculating the total number of magnetic metal particles according to a formula.

[0028] According to the detection method of magnetic metal particles in the positive electrode material of the battery of the embodiment of the present application, by reducing the number of barrel changes during the extraction process of the magnetic metal particles, the extraction steps are reduced, the extraction time is shortened, and the test efficiency is improved while ensuring that the metal particles are accurately extracted. At the same time, by reducing the number of barrel changes, the loss of magnetic metal particles caused by multiple barrel changes is reduced, and the test accuracy is improved. In addition, the magnetic metal particle suspension after the magnetic metal particles are extracted and collected is directly filtered to replace multiple manual cleanings, reduce the time-consuming manual operation, and avoid the loss of some small magnetic metal particles with weak adsorption force caused by manual cleaning operations, thereby improving the test efficiency and accuracy.

[0029] In view of the shortcomings of the prior art that the detection process is time-consuming and the magnetic metal particles are easily lost during the detection process, this application provides a detection method that effectively improves the stability and efficiency of the test of the number of magnetic metal particles in the positive electrode material of lithium-ion batteries. This application mainly improves the extraction and collection of magnetic metal particles and the cleaning of magnetic metal particles. Specifically, this application reduces the process of placing the magnetic adsorbent into a plastic bucket for extraction and cleaning three times during the extraction of magnetic metal particles to one time, and replaces the complicated manual cleaning steps in the collection process with an external magnetic ring. It only takes about 1.5 hours to prepare each sample, and the manual operation time is reduced by an average of about 30 minutes, greatly improving the test efficiency. The extraction rate of the number of magnetic metal particles in the positive electrode material using the method of this application is >80%, which is relatively accurate and stable.

[0030] The following is a detailed description of the method for detecting magnetic metal particles in the battery positive electrode material proposed in this application:

[0031] Specifically, refer to the attached Figure 1 The above-mentioned method for detecting magnetic metal particles in the positive electrode material of the battery comprises the following steps:

[0032] S100: mixing and stirring the positive electrode powder material, the first solvent and the magnetic adsorbent so that the magnetic metal particles in the positive electrode powder material are adsorbed on the surface of the magnetic adsorbent;

[0033] In this step, the magnetic adsorbent includes a magnetic rod and a non-magnetic tube (such as a heat shrink tube) sleeved on the surface of the magnetic rod. The non-magnetic tube is sleeved on the magnetic rod and heat-sealed with a heat sealer. The weighed positive electrode material sample and the heat-sealed magnetic adsorbent are mixed in a non-magnetic barrel (such as a plastic barrel), and the first solvent is added and stirred to fully adsorb the magnetic particles on the heat-sealed magnetic rod.

[0034] As a preferred solution, a non-magnetic barrel containing a positive electrode powder material, a first solvent and a magnetic adsorbent is sealed and placed on a second ball mill for rolling, so that the magnetic metal particles in the positive electrode powder material are fully adsorbed on the surface of the magnetic adsorbent, thereby effectively reducing the number of barrel changes during the extraction of magnetic metal particles (i.e., the present application reduces the process of placing the magnetic adsorbent in a non-magnetic barrel for extraction and cleaning three times in the extraction process of magnetic metal particles in the prior art to one time), and on the premise of ensuring that the metal particles are accurately extracted, the extraction steps are reduced, the extraction time is shortened, and the test efficiency is improved. Further, the rotation speed of the second ball mill is 20Hz to 100Hz (as an example, it can be 20Hz, 30Hz, 40Hz, 50Hz, 60Hz, 70Hz, 80Hz, 90Hz, 100Hz, etc.), and the time is 5min to 20min (as an example, it can be 5min, 10min, 15min, 20min, etc.), thereby further allowing the magnetic metal particles in the positive electrode powder material to be adsorbed on the surface of the magnetic adsorbent. As a specific embodiment, the second ball mill has a rotation speed of 40 Hz and a time of 15 minutes.

[0035] According to some specific embodiments of the present application, the length of the magnetic bar is 200mm-300mm (as an example, it can be 200mm, 210mm, 220mm, 230mm, 240mm, 250mm, 260mm, 270mm, 280mm, 290mm, 300mm, etc.), the diameter of the magnetic bar is 20mm-30mm (as an example, it can be 20mm, 21mm, 22mm, 23mm, 24mm, 25mm, 26mm, 27mm, 28mm, 29mm, 30mm, etc.), and the magnetic field strength of the magnetic bar is 5000GS-7000GS (as an example, it can be 5000GS, 6000GS, 7000GS, etc.), thereby further ensuring that the magnetic metal particles are fully adsorbed on the surface of the magnetic adsorbent. As a specific embodiment, the length of the magnetic bar is 240mm, the diameter is 24mm, and the magnetic field strength is 6000GS.

[0036] In the embodiments of the present application, the specific material of the non-magnetic tube is not particularly limited, and those skilled in the art may select it according to actual needs. As some preferred embodiments, the non-magnetic tube may be made of heat-shrinkable plastic material.

[0037] In the embodiments of the present application, the non-magnetic tube is sleeved on the surface of the magnetic rod, and the non-magnetic tube is arranged close to the magnetic rod. The size of the non-magnetic tube depends on the size of the magnetic rod. According to some other specific embodiments of the present application, the wall thickness of the non-magnetic tube is 0.1mm to 0.5mm (as an example, it can be 0.1mm, 0.2mm, 0.3mm, 0.4mm, 0.5mm, etc.), thereby further ensuring that the magnetic metal particles are fully adsorbed on the surface of the magnetic adsorbent. As a specific embodiment, the diameter of the non-magnetic tube is 25mm and the wall thickness is 0.3mm.

[0038] In the embodiments of the present application, the specific type of the first solvent is not particularly limited, and those skilled in the art may select it according to actual needs. Water is preferred, and pure water is more preferred.

[0039] Furthermore, the above method for detecting magnetic metal particles in the positive electrode material of a battery further includes the following steps before step S100:

[0040] Preparation before sample preparation: Use a magnetic bar to demagnetize the environment, sample preparation tools, sample bags and the operator himself. As a specific embodiment, the length of the magnetic bar used is 240 mm, the diameter is 24 mm, and the magnetic field strength is 12000 GS.

[0041] S200: collecting coarse magnetic metal particles on the surface of the magnetic adsorbent;

[0042] According to some specific embodiments of the present application, step S200 includes: cutting the non-magnetic tube, taking out the magnetic rod, washing the outer wall of the non-magnetic tube with a second solvent, and scraping the outer wall of the non-magnetic tube with a non-magnetic blade (such as a ceramic blade), and then washing the outer wall of the non-magnetic tube again to ensure that all the magnetic particles are washed into the beaker. It should be noted that a small amount of positive electrode powder may be attached to the surface of the coarse magnetic metal particles collected in this step.

[0043] In the embodiments of the present application, the specific type of the second solvent is not particularly limited, and those skilled in the art may select it according to actual needs. Water is preferred, and pure water is more preferred.

[0044] S300: Mixing the coarse magnetic metal particles with the acid solution and placing them in a container, wherein at least a portion of the side surface of the container is covered with an external magnetic ring, and the container is placed on a first ball mill and rolled so that the external magnetic ring can adsorb the magnetic metal particles;

[0045] In this step, acid is added to the coarse magnetic metal particles collected in step S200, and ultrasound is performed to separate the positive electrode powder attached to the surface of the coarse magnetic metal particles from the surface of the magnetic metal particles, thereby effectively avoiding the positive electrode powder from being mixed into the magnetic metal particles, thereby improving the accuracy of the detection method of magnetic metal particles in the positive electrode material of the battery. Then pour it into a container (such as a PE bottle), the side surface of the container is sleeved with an external magnetic ring, and the container is placed on the first ball mill and rolled, so that the magnetic metal particles in the mixed liquid in the container are fully adsorbed on the inner wall of the container by the external magnetic ring, while the positive electrode powder separated from the surface of the magnetic metal particles is still in the mixed liquid, thereby further realizing the separation of the magnetic metal particles and the positive electrode powder.

[0046] In the embodiments of the present application, the specific type of the above-mentioned acid solution is not particularly limited, and those skilled in the art can select it according to actual needs. As some preferred embodiments, the above-mentioned acid solution includes HCl solution and HNO 3 Further, the mass concentration of the acid solution is 10% to 30%, and as an example, it can be 10%, 15%, 20%, 25%, 30%, etc., thereby further ensuring that the positive electrode powder attached to the surface of the magnetic metal particles is separated from the surface of the magnetic metal particles.

[0047] According to some specific embodiments of the present application, ultrasound is performed for 1 min to 10 min (for example, 1 min, 2 min, 3 min, 4 min, 5 min, 6 min, 7 min, 8 min, 9 min, 10 min, etc.), thereby further ensuring that the positive electrode powder attached to the surface of the magnetic metal particles is separated from the surface of the magnetic metal particles. Preferably, 1 min to 5 min.

[0048] According to some further specific embodiments of the present application, the rotation speed of the first ball mill is 20 Hz to 100 Hz (as an example, it can be 20 Hz, 30 Hz, 40 Hz, 50 Hz, 60 Hz, 70 Hz, 80 Hz, 90 Hz, 100 Hz, etc.), and the time is 25 min to 40 min (as an example, it can be 25 min, 30 min, 35 min, 40 min, etc.), thereby further ensuring that the magnetic metal particles in the mixed liquid in the container are fully adsorbed on the inner wall of the container by the external magnetic ring. As a specific embodiment, the rotation speed of the first ball mill is 40 Hz, and the time is 30 min.

[0049] According to some other specific embodiments of the present application, the magnetic field strength of the external magnetic ring is 5000GS to 7000GS, and can be 5000GS, 6000GS, 7000GS, etc. as examples, thereby further ensuring that the magnetic metal particles in the mixed liquid in the container are fully adsorbed on the inner wall of the container by the external magnetic ring, thereby further achieving the separation of the magnetic metal particles and the positive electrode powder. As a specific embodiment, the magnetic field strength of the external magnetic ring is 6000GS.

[0050] S400: pouring out the liquid in the container, removing the external magnetic ring, collecting the magnetic metal particles on the inner wall of the container, and obtaining a magnetic metal particle suspension;

[0051] In this step, the liquid mixed with the positive electrode powder in the container is poured out, and the magnetic metal particles are adsorbed on the inner wall of the container by the external magnetic ring, thereby achieving the separation of the magnetic metal particles and the positive electrode powder. Then, the external magnetic ring is removed, and the magnetic metal particles on the inner wall of the container are washed with a third solvent to obtain a magnetic metal particle suspension.

[0052] In the embodiments of the present application, the specific type of the third solvent is not particularly limited, and those skilled in the art may select it according to actual needs. Water is preferred, and pure water is more preferred.

[0053] S500: filtering and drying the magnetic metal particle suspension to obtain magnetic metal particles;

[0054] In this step, the magnetic metal particle suspension is filtered, and after the filtration, the filter paper with the magnetic metal particles attached to the surface is placed on the slide of the cleanliness meter microscope, and the slide is placed in an oven to dry to obtain the magnetic metal particles.

[0055] According to some other specific embodiments of the present application, the pore size of the filter membrane used for filtration is less than 4.5 μm to 5.5 μm, thereby preventing small-size magnetic metal particles from being filtered out.

[0056] The present application adds steps S300 and S400 before the filtration, and realizes the separation of the positive electrode powder attached to the surface of the magnetic metal particles, thereby improving the accuracy of the detection method of the magnetic metal particles in the positive electrode material of the battery. If the filtration is directly performed after the addition of the acid solution for ultrasonic treatment, the separation of the magnetic metal particles and the positive electrode powder cannot be achieved.

[0057] S600: Detect and analyze the number and size of magnetic metal particles, and calculate the total number of magnetic metal particles according to a formula.

[0058] In this step, the automatic analysis system of the slide cleanliness instrument with filter paper is used to detect and analyze the number and size of magnetic metal particles. The instrument automatically reads the number of particles in the range of particle size >200μm, 150μm to 200μm, 100μm to 150μm, 50μm to 100μm, and 25μm to 50μm, and the total number of magnetic metal particles in 1kg of battery positive electrode material is calculated according to the following formula:

[0059] The total number of magnetic metal particles in 1 kg of battery positive electrode material = (the number of particles with a particle size of 25 μm to 50 μm) / 2 + (the number of particles with a particle size of 50 μm to 100 μm) / 2 + (the number of particles with a particle size of 100 μm to 150 μm) + (the number of particles with a particle size of 150 μm to 200 μm) + (the number of particles with a particle size > 200 μm).

[0060] In the second aspect of the present application, the present application proposes an application of the above embodiment method in the preparation process of battery positive electrode materials. It should be noted that the features and advantages described above for the detection method of magnetic metal particles in battery positive electrode materials are also applicable to the application of this method in the preparation process of battery positive electrode materials, specifically, the test stability and test efficiency of the number of magnetic metal particles in battery positive electrode materials are improved.

[0061] The embodiments of the present application are described in detail below. It should be noted that the embodiments described below are exemplary and are only used to explain the present application, and should not be construed as limiting the present application. In addition, unless otherwise explicitly stated, all reagents used in the following embodiments are commercially available or can be synthesized according to this article or known methods, and the reaction conditions not listed are also easily available to those skilled in the art.

[0062] Example 1

[0063] This embodiment provides a method for detecting magnetic metal particles in a positive electrode material of a battery, comprising the following steps:

[0064] 1) Preparation before sample preparation: Use a 12000Gs magnetic bar to demagnetize the operating table, gloves, heat shrink tubing, heat sealer, plastic barrel wall and other testing tools and testing environments that may be in contact with the test tools. Place a 12000Gs magnetic bar in a plastic barrel, add 5L of ultrapure water, wrap the barrel mouth with plastic wrap three times, seal the lid, and roll it on a ball mill for 10 minutes to demagnetize it.

[0065] 2) Extraction of magnetic particles: Weigh 1000g of positive electrode material sample into a demagnetized plastic bucket, add 5.0L of pure water, and then put in a 6000Gs magnetic rod sealed with a heat shrink tube. The two ends of the magnetic rod were sealed with wrinkle glue for three circles in advance. After the plastic bucket is sealed, it is placed on the second ball mill, and the speed is set to 40Hz and the time is 15min.

[0066] 3) Magnetic particle collection: Place the magnetic rod after extracting the magnetic particles in a 500 mL beaker, cut the heat shrink tube, take out the magnetic rod, rinse the tube wall with pure water, scrape it 4 times with a ceramic knife and rinse it again to ensure that all the magnetic particles are rinsed into the beaker.

[0067] 4) Then add 20 mL of 18% HCl solution, ultrasonicate for 2 minutes, and pour into a 500 mL PE bottle. After the PE bottle is sealed, put a 6000 Gs external magnetic ring on the side, place it on the first ball mill and roll it for 30 minutes, setting the speed to 40 Hz.

[0068] 5) When the external magnetic ring is wrapped around the PE bottle, pour out the liquid (including non-magnetic substances) in the bottle, then remove the external magnetic ring, rinse the PE bottle several times, and obtain a magnetic metal particle suspension.

[0069] 6) Filtration and drying: Pour the magnetic metal particle suspension into the filtration bottle, rinse the beaker wall and the inner wall of the filter cup 10 times with a washing bottle, and after filtration, place the filter paper with magnetic particles on the surface on the slide of the cleanliness meter microscope, and place the slide in a 60℃ oven to dry for 15 minutes.

[0070] 7) The dried filter membrane on the slide was tested for magnetic metal particles in the cleanliness automatic analysis system of the cleanliness instrument. The results are shown in Table 1.

[0071] Example 2

[0072] The experiment of extracting the magnetic metal particles in the positive electrode material in Example 1 mainly includes the following steps:

[0073] After completing the first extraction and detection of magnetic metal particles according to the detection steps of Example 1, the filter membrane was ultrasonicated for 15 minutes. After the ultrasonication, the solution was poured into the plastic bucket after the magnetic rod was taken out in step 2) of Example 1 to complete the extraction, and a 6000Gs magnetic rod was added. Steps 2) to 7) in Example 1 were repeated to obtain the measurement results of the magnetic metal particles extracted for the second time. The ratio of the measurement results of the number of magnetic metal particles extracted for the second time to the measurement results of the number of magnetic metal particles extracted for the first time was the extraction rate of the method. The results are shown in Table 1.

[0074] Example 3

[0075] The detection method of this embodiment is basically the same as the detection method of embodiment 1, except that:

[0076] 2) Extraction of magnetic particles: Weigh 1000g of positive electrode material sample into a demagnetized plastic bucket, add 5.0L of pure water, and then put in a 6000Gs magnetic rod sealed with a heat shrink tube. The two ends of the magnetic rod were sealed with wrinkle glue for three circles in advance. After the plastic bucket is sealed, it is placed on the second ball mill, and the speed is set to 30Hz and the time is 20min.

[0077] Example 4

[0078] The experiment of extracting the magnetic metal particles in the positive electrode material in Example 3 mainly includes the following steps:

[0079] After completing the first extraction and detection of magnetic metal particles according to the detection steps of Example 3, the filter membrane was ultrasonicated for 15 minutes. After the ultrasonication, the solution was poured into the plastic bucket after the magnetic rod was taken out in step 2) of Example 3 to complete the extraction, and a 6000Gs magnetic rod was added. Steps 2) to 7) in Example 3 were repeated to obtain the measurement results of the magnetic metal particles extracted for the second time. The ratio of the measurement results of the number of magnetic metal particles extracted for the second time to the measurement results of the number of magnetic metal particles for the first time was the extraction rate of the method. The results are shown in Table 1.

[0080] Example 5

[0081] The detection method of this embodiment is basically the same as the detection method of embodiment 1, except that:

[0082] 2) Extraction of magnetic particles: Weigh 1000g of positive electrode material sample into a demagnetized plastic bucket, add 5.0L of pure water, and then put in a 6000Gs magnetic rod sealed with a heat shrink tube. The two ends of the magnetic rod were sealed with wrinkle glue for three circles in advance. After the plastic bucket is sealed, it is placed on the second ball mill, and the speed is set to 50Hz and the time is 15min.

[0083] Example 6

[0084] The experiment of extracting the magnetic metal particles in the positive electrode material in Example 5 mainly includes the following steps:

[0085] After completing the first extraction and detection of magnetic metal particles according to the detection steps of Example 5, the filter membrane was ultrasonicated for 15 minutes. After the ultrasonication, the solution was poured into the plastic bucket after the magnetic rod was taken out in step 2) of Example 5 to complete the extraction, and a 6000Gs magnetic rod was added. Steps 2) to 7) in Example 5 were repeated to obtain the measurement results of the magnetic metal particles extracted for the second time. The ratio of the measurement results of the number of magnetic metal particles extracted for the second time to the measurement results of the number of magnetic metal particles for the first time was the extraction rate of the method. The results are shown in Table 1.

[0086] Example 7

[0087] The detection method of this embodiment is basically the same as the detection method of embodiment 1, except that:

[0088] 4) Then add 20 mL of 18% HCl solution, ultrasonicate for 2 minutes, and pour into a 500 mL PE bottle. After the PE bottle is sealed, put a 6000 Gs external magnetic ring on the side, place it on the first ball mill and roll it for 40 minutes, setting the speed to 20 Hz.

[0089] Example 8

[0090] The experiment of extracting the number of magnetic metal particles in the positive electrode material in Example 7 mainly includes the following steps:

[0091] After completing the first extraction and detection of magnetic metal particles according to the detection steps of Example 7, the filter membrane was ultrasonicated for 15 minutes. After the ultrasonication, the solution was poured into the plastic bucket after the magnetic rod was taken out in step 2) of Example 7 to complete the extraction, and a 6000Gs magnetic rod was added. Steps 2) to 7) in Example 7 were repeated to obtain the measurement results of the magnetic metal particles extracted for the second time. The ratio of the measurement results of the number of magnetic metal particles extracted for the second time to the measurement results of the number of magnetic metal particles extracted for the first time was the extraction rate of the method. The results are shown in Table 1.

[0092] Example 9

[0093] The detection method of this embodiment is basically the same as the detection method of embodiment 1, except that:

[0094] 4) Then add 20 mL of 18% HCl solution, ultrasonicate for 2 minutes, and pour into a 500 mL PE bottle. After the PE bottle is sealed, put a 6000 Gs external magnetic ring on the side, place it on the first ball mill and roll it for 20 minutes, setting the speed to 60 Hz.

[0095] Example 10

[0096] The experiment of extracting the magnetic metal particles in the positive electrode material in Example 9 mainly includes the following steps:

[0097] After completing the first extraction and detection of magnetic metal particles according to the detection steps of Example 9, the filter membrane was ultrasonicated for 15 minutes. After the ultrasonication, the solution was poured into the plastic bucket after the magnetic rod was taken out in step 2) of Example 9 to complete the extraction, and a 6000Gs magnetic rod was added. Steps 2) to 7) in Example 9 were repeated to obtain the measurement results of the magnetic metal particles extracted for the second time. The ratio of the measurement results of the number of magnetic metal particles extracted for the second time to the measurement results of the number of magnetic metal particles for the first time was the extraction rate of the method. The results are shown in Table 1.

[0098] Comparative Example 1

[0099] 1) Preparation before sample preparation: Use a 12000Gs magnetic bar to demagnetize the work surface, hands, gloves, heat shrink tubing, heat sealer, plastic barrel wall, etc. that may be in contact with the magnet. Place three 12000Gs magnetic bars in three plastic barrels, add 5L of ultrapure water, wrap the barrel mouth with plastic wrap three times, seal the lid, and roll it on a ball mill for 10 minutes to demagnetize.

[0100] 2) Extraction of magnetic particles: Weigh 1000g of positive electrode material sample into a demagnetized plastic bucket, add 5.0L of pure water, and then put in a 6000Gs magnetic rod sealed with a heat shrink tube. The two ends of the magnetic rod were sealed with wrinkle glue three times in advance. After the plastic bucket is sealed, it is placed on the first ball mill, and the speed is set to 40Hz for 15min. Then the magnetic rod is taken out and placed in a new bucket. Under the same conditions, it is rolled on the first ball mill for 15min, and finally repeated once.

[0101] 3) Collection of magnetic particles: Place the magnetic rod after extracting the magnetic particles in a 500mL beaker, cut the heat shrink tube, take out the magnetic rod, rinse the tube wall with pure water, scrape it with a ceramic knife for 3-5 times, and then rinse it again to ensure that all the magnetic particles are rinsed into the beaker. Use a small magnetic block to adsorb 15 circles clockwise from the outside to the inside at the bottom of the beaker, then fix the magnetic block, shake the beaker clockwise for 15 circles, and then rinse the adsorbed impurities along the wall of the beaker 3-5 times. Ensure that no more than 100mL of liquid remains in the beaker each time.

[0102] Then add 20mL of 18% HCl, ultrasonicate for 2 minutes, then use a small magnetic block to suck the bottom of the beaker and rotate it 15 times, then fix the beaker with the small magnetic block and shake it 15 times, rinse along the wall of the beaker with pure water for 3 times, and ensure that no more than 100mL of liquid remains in the beaker each time.

[0103] 4) Filtration and drying: Pour the liquid in the PE bottle into the filtration bottle, rinse the beaker wall and the inner wall of the filter cup 10 times with a washing bottle, and after filtration, place the filter paper with magnetic particles on the surface on the slide of the cleanliness meter microscope, and place the slide in a 60℃ oven to dry for 15 minutes.

[0104] 5) The dried filter membrane on the slide was tested for magnetic metal particles in the cleanliness automatic analysis system of the cleanliness instrument. The results are shown in Table 1. The results are shown in Table 1.

[0105] Comparative Example 2

[0106] The experiment of extracting the number of magnetic metal particles in the positive electrode material in Comparative Example 1 mainly includes the following steps:

[0107] After completing the first extraction and detection of magnetic metal particles according to the detection steps of Comparative Example 1, the filter membrane was ultrasonicated for 15 minutes. After the ultrasonication, the solution was poured into the plastic bucket after the magnetic rod was taken out in step 2) of Comparative Example 1 to complete the extraction, and a 6000Gs magnetic rod was added. Steps 2)-5) in Comparative Example 1 were repeated to obtain the measurement results of the magnetic metal particles extracted for the second time. The ratio of the measurement results of the number of magnetic metal particles extracted for the second time to the measurement results of the number of magnetic metal particles extracted for the first time was the extraction rate of the method. The results are shown in Table 1.

[0108] It should be noted that the positive electrode material samples in the above embodiments and comparative examples are the same. The test results of the positive electrode material samples are shown in Table 1.

[0109] Table 1

[0110]

[0111]

[0112] It can be seen from Table 1 that, compared with Comparative Examples 1-2, the extraction rate of Examples 1-10 is significantly improved, and the time for testing one sample of Examples 1-10 is significantly reduced, and the testing efficiency is greatly improved.

[0113] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present application. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0114] Although the embodiments of the present application have been shown and described above, it can be understood that the above embodiments are exemplary and cannot be understood as limitations on the present application. Ordinary technicians in this field can change, modify, replace and modify the above embodiments within the scope of the present application.

Claims

1. A method for detecting magnetic metal particles in a positive electrode material of a battery, characterized in that: include: (1) mixing and stirring a positive electrode powder material, a first solvent, and a magnetic adsorbent so that magnetic metal particles in the positive electrode powder material are adsorbed on the surface of the magnetic adsorbent; (2) collecting coarse magnetic metal particles on the surface of the magnetic adsorbent; (3) mixing the coarse magnetic metal particles with an acid solution and placing the mixture in a container, wherein at least a portion of the side surface of the container is covered with an external magnetic ring, and the container is placed on a first ball mill and rolled so that the external magnetic ring can adsorb the magnetic metal particles; (4) pouring out the liquid in the container, removing the external magnetic ring, and collecting the magnetic metal particles on the inner wall of the container to obtain a magnetic metal particle suspension; (5) filtering the magnetic metal particle suspension and drying it to obtain magnetic metal particles; (6) Detect and analyze the number and size of magnetic metal particles, and calculate the total number of magnetic metal particles according to the formula.

2. The method for detecting magnetic metal particles in a positive electrode material of a battery according to claim 1, characterized in that: In step (1), the positive electrode powder material, the first solvent and the magnetic adsorbent are placed in a non-magnetic barrel, mixed and stirred, the non-magnetic barrel is sealed, and the non-magnetic barrel is placed on a second ball mill for rolling so that the magnetic metal particles in the positive electrode powder material are adsorbed on the surface of the magnetic adsorbent.

3. The method for detecting magnetic metal particles in a positive electrode material of a battery according to claim 2, characterized in that: In step (1), the rotation speed of the second ball mill is 20 Hz to 100 Hz, and the time is 5 min to 20 min.

4. The method for detecting magnetic metal particles in a positive electrode material of a battery according to claim 1, characterized in that: In step (1), the magnetic adsorption component includes a magnetic rod and a non-magnetic tube sleeved on the surface of the magnetic rod, the length of the magnetic rod is 200mm to 300mm, the diameter of the magnetic rod is 20mm to 30mm, the magnetic field strength of the magnetic rod is 5000GS to 7000GS, and the wall thickness of the non-magnetic tube is 0.1mm to 0.5mm.

5. The method for detecting magnetic metal particles in a positive electrode material of a battery according to claim 4, characterized in that: Step (2) comprises: The magnetic rod is taken out, the outer wall of the non-magnetic tube is washed with a second solvent, and the outer wall of the non-magnetic tube is scraped with a non-magnetic blade to collect the coarse magnetic metal particles on the surface of the magnetic adsorbent.

6. The method for detecting magnetic metal particles in a positive electrode material of a battery according to claim 1, characterized in that: The acid solution includes at least one of HCl solution and HNO3 solution; And / or, the mass concentration of the acid solution is 10% to 30%.

7. The method for detecting magnetic metal particles in a positive electrode material of a battery according to claim 1, characterized in that: In step (3), the coarse magnetic metal particles are mixed with the acid solution and ultrasonically placed in the container; And / or, in step (3), the rotation speed of the first ball mill is 20 Hz to 100 Hz, and the time is 25 min to 40 min; And / or, in step (3), the magnetic field strength of the external magnetic ring is 5000GS to 7000GS.

8. The method for detecting magnetic metal particles in a positive electrode material of a battery according to claim 1, characterized in that: In step (4), the liquid in the container is poured out, the external magnetic ring is removed, and the magnetic metal particles on the inner wall of the container are rinsed with a third solvent to obtain a magnetic metal particle suspension.

9. The method for detecting magnetic metal particles in a positive electrode material of a battery according to claim 1, characterized in that: In step (5), the pore size of the filter membrane used for the suction filtration is less than 4.5 μm to 5.5 μm; And / or, in step (6), the instrument automatically reads the number of particles in the ranges of particle sizes >200 μm, 150 μm to 200 μm, 100 μm to 150 μm, 50 μm to 100 μm, and 25 μm to 50 μm, and calculates the total number of magnetic metal particles in 1 kg of battery positive electrode material according to the following formula: The total number of magnetic metal particles in 1 kg of battery positive electrode material = (the number of particles with a particle size of 25 μm to 50 μm) / 2 + (the number of particles with a particle size of 50 μm to 100 μm) / 2 + (the number of particles with a particle size of 100 μm to 150 μm) + (the number of particles with a particle size of 150 μm to 200 μm) + (the number of particles with a particle size > 200 μm).

10. Use of the method for detecting magnetic metal particles in a battery positive electrode material as claimed in any one of claims 1 to 9 in a process for preparing a battery positive electrode material.

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