Method for detecting number and elemental composition of falling dust particles in battery material packaging workshop

Abstract

The invention discloses a method for detecting the number and elemental composition of falling dust particles in a battery material packaging workshop, and the method comprises the following specific steps: adding ultrapure water into a beaker, and placing the beaker at a sampling point for 24 hours in an open manner; carrying out suction filtration on the liquid of the collected sample, and drying; and testing the number of particles of the collected sample filter membrane by using a JOMESAHFD cleanliness detector, or testing the elemental composition of the particles by using a JOMESAPSE scanning electron microscope. The method can accurately detect the number and elemental composition of insoluble and settled foreign matters by collecting naturally settled particulate matters in a lithium hydroxide packaging workshop environment without destroying the form of the foreign matters, is simple and rapid to operate, and reliable and accurate in result, so that the method can effectively help the packaging workshop to identify the source of the foreign matters and investigate the foreign matters, and improves the detection efficiency of the foreign matters. And effective control measures are formulated.

Description

Technical Field

[0001] This invention relates to the field of lithium-ion battery cathode material testing, and more specifically, to a method for detecting the number and elemental composition of dust particles falling into a battery material packaging workshop. Background Technology

[0002] Research has found that if lithium-ion batteries use cathode and anode materials containing metallic impurities such as Cu, Cr, and Zn, these metals will oxidize at the cathode and then reduce at the anode when the voltage during battery formation reaches their redox potential. When the metals accumulate to a certain level at the anode, their sharp edges can pierce the separator, causing self-discharge. Severe self-discharge affects the performance and safety of lithium-ion batteries, making it crucial to prevent the introduction of copper and zinc impurities at the source.

[0003] However, current detection of copper and zinc foreign matter generally only involves the content and quantity of magnetic foreign matter in raw materials, intermediate controls, and final products. There is a lack of simple and accurate methods for analyzing the composition of all magnetic and non-magnetic foreign matter in the production environment, which is one of the problems that battery and material manufacturers are currently concerned about and urgently need to solve. Summary of the Invention

[0004] In order to overcome the shortcomings of the existing technology, the purpose of this invention is to provide a method for detecting the quantity and elemental composition of dust particles in a packaging workshop, so as to solve the problem that existing methods cannot easily and accurately detect the quantity and composition of all magnetic and non-magnetic foreign objects in the production environment.

[0005] The technical solution adopted in this invention is as follows: (1) Add ultrapure water to a beaker and leave it open at the sampling point for 24 hours; (2) Filter and dry the liquid in the collected sample; (3) The number of particles in the filter membrane of the collected sample is tested using a JOMESAPHFD cleanliness tester, or the elemental composition of the particles is tested using a JOMESAPSE scanning electron microscope.

[0006] In step (1), the sampling point should be set at a height of 0.3m above ground level and 0.8-1.2m above the equipment operating surface. Avoid setting it in areas where air conditioning blows directly on it, where people frequently touch it, or where the equipment vibrates strongly.

[0007] In step (1), the beaker is 3L and the volume of ultrapure water added is 2000ml.

[0008] In step (1), the beaker is left open at the sampling point for 24 hours. If the beaker is tipped over or foreign objects are introduced due to human error during the sampling period, the sample must be resampled.

[0009] In step (2), a vacuum pump is used for liquid filtration, the filter membrane has a pore size of 0.45 μm, the drying temperature is 60 °C, and the drying time is about 30 minutes.

[0010] In step (3), after the filter membrane of the collected sample is allowed to cool naturally, the particle number is tested by scanning with a JOMESAHFD cleanliness detector. The analysis magnification is 2.5, the average filter is 3×3 with a length of 31, and the Laplace filter is 5×5 with a length of 1.500. After the scan is completed, the number of particles of each size is recorded.

[0011] In step (3), the total number of particles is calculated as follows: Total number of particles (PCS / kg) = Number of particles of each size × Sum of coefficients The coefficients for each particle size in the formula are as follows: Particle size (µm) coefficient ＞100 1 25~100 0.5 ＜25 0 In step (3), the filter membrane of the collected sample is attached to the sample holder base with a fixative and allowed to air dry naturally. Then, the elemental composition of the particles is tested by scanning with a JOMESAPSE scanning electron microscope. The parameters are set as follows: low vacuum full scan, magnification 1 mm, elements of interest Cu, Zn, and Cr, EDS count 10000, timeout 5 s, maximum diameter 25 μm. After the scan, the elemental mass percentage of each particle is recorded. The particle composition is determined by the elemental mass percentage of each particle, the origin of the particles is inferred, and the element with the highest content is identified as the element particle. The number of particles of each type is calculated.

[0012] This invention collects naturally settling particulate matter from the environment using pure water over a unit of time, dissolving potential product particles and other soluble substances, leaving only insoluble foreign matter without damaging its morphology. It accurately detects the quantity and elemental composition of the settled foreign matter, and is simple and reliable to operate. This effectively helps packaging departments identify the source of foreign matter, conduct foreign matter screening, and develop effective control measures. Attached Figure Description

[0013] Figure 1 This is the image of the largest particle in the first independent test.

[0014] Figure 2 This is the energy spectrum of the largest particle in the first independent test. Detailed Implementation

[0015] The following embodiments will enable those skilled in the art to more fully understand the present invention. The embodiments and features in the embodiments of this application can be combined with each other, but the present invention is not limited to the scope of the embodiments described. Example

[0016] The method for detecting the quantity and elemental composition of dust particles in a lithium hydroxide packaging workshop is as follows: Take a clean 3L beaker, add 2000ml of ultrapure water, and place it open at the sampling point. The sampling point should be set at a height of 0.3m above ground level and 0.8-1.2m above the equipment operating surface. Avoid placing it in areas where air conditioning blows directly on it, where people frequently touch it, or where the equipment vibrates strongly. For packaging rooms with an area of ​​<50㎡, set up 1-3 sampling points; for packaging rooms with an area of ​​50-100㎡, set up 3-5 sampling points; for packaging rooms with an area of ​​>100㎡, set up 5-7 sampling points.

[0017] The sampling beaker should be left open at the sampling point for 24 hours. If the beaker is tipped over or foreign objects are introduced due to human error during the sampling period, the sample must be resampled. (3) The collected liquid sample is filtered by vacuum pump. The filter membrane has a pore size of 0.45 μm and is dried at 60°C for about 30 minutes. Do not dry for too long or at too high a temperature, otherwise some metals will be oxidized and lose their metallic luster, making the test results inaccurate. (4) After the filter membrane is dried, it is allowed to cool naturally. The JOMESAHFD cleanliness tester is used to scan it. The analysis magnification is 2.5, the average filter length is 31 for 3×3 and the Laplace filter length is 1.500 for 5×5. After the scan is completed, the number of particles of each size is recorded.

[0018] (5) The total number of particles is calculated as follows: Total number of particles (PCS / kg) = Number of particles of each size × Sum of coefficients The coefficients for each particle size in the formula are as follows:

[0019] (6) Ten repeated tests were conducted on the same sampling point. The number of particles with metallic luster was counted and the total number of particles was calculated. The test results are shown in Table 1. The results show that the cleanliness of this packaging room is poor and needs to be cleaned.

[0020] (7) Then, attach the filter membrane of the collected sample to the PSE sample holder base with fixative, remove air bubbles, and let it air dry naturally. Be careful not to lose any particles or introduce other foreign objects during the operation. After drying, scan with a JOMESAPSE scanning electron microscope. Set the parameters to low vacuum full scan, magnification 1 mm, elements of interest Cu, Zn, and Cr, EDS count 10,000, timeout 5 s, and maximum diameter 25 μm. After the scan, determine the particle composition by the elemental mass percentage composition of each particle and infer the origin of the particles.

[0021] (8) Perform 10 repeated tests on the same sampling point. Figure 1-2The image and energy dispersive spectroscopy (EDS) of the largest particle in the first independent test show a size of 155µm, containing 77.3% iron, 11.9% chromium, and 10.8% aluminum. It is presumed to be a particle shed from the wear of an iron-chromium-aluminum (Fe2O3) heating material, providing significant guidance for identifying the source of foreign matter in the workshop. This particle has the highest iron content and is therefore identified as an iron particle with a size of 155µm. The number of Cu, Zn, and Cr particles, which have a significant impact on the battery, was counted using this method. The total number of particles of each type is the sum of the number of particles of each size. The results are shown in Table 2. The results indicate that the dust in this packaging area contains copper and zinc foreign matter, which needs to be investigated to prevent it from entering the product.

[0022] Table 1:

[0023] Table 2:

[0024] As can be seen from the test results in Tables 1 and 2, the method provided by this invention can simply and accurately detect the quantity and elemental composition of dust in the production workshop, providing an effective basis for controlling foreign matter.

Claims

1. A method for detecting the quantity and elemental composition of dust particles in a battery material packaging workshop, characterized in that, Includes the following steps: (1) Add ultrapure water to a beaker and leave it open at the sampling point for 24 hours; (2) Filter and dry the liquid in the collected sample; (3) The number of particles in the filter membrane of the collected sample is tested using a JOMESAPHFD cleanliness tester, or the elemental composition of the particles is tested using a JOMESAPSE scanning electron microscope.

2. The method for detecting the quantity and elemental composition of dust particles in a battery material packaging workshop according to claim 1, characterized in that, In step (1), the sampling point should be set at a height of 0.3m above ground level and 0.8-1.2m above the equipment operating surface. Avoid setting it in areas where air conditioning blows directly on it, where people frequently touch it, or where the equipment vibrates strongly.

3. The method for detecting the quantity and elemental composition of dust particles in a battery material packaging workshop according to claim 1, characterized in that, In step (1), the beaker is 3L and the volume of ultrapure water added is 2000ml.

4. The method for detecting the quantity and elemental composition of dust particles in a battery material packaging workshop according to claim 1, characterized in that, In step (1), the beaker is left open at the sampling point for 24 hours. If the beaker is tipped over or foreign objects are introduced due to human error during the sampling period, the sample must be resampled.

5. The method for detecting the quantity and elemental composition of dust particles in a battery material packaging workshop according to claim 1, characterized in that, In step (2), a vacuum pump is used for liquid filtration, the filter membrane has a pore size of 0.45 μm, the drying temperature is 60 °C, and the drying time is about 30 minutes.

6. The method for detecting the quantity and elemental composition of dust particles in a battery material packaging workshop according to claim 1, characterized in that, Step (3) After the filter membrane of the collected sample is allowed to cool naturally, the particle number is tested by scanning with a JOMESAHFD cleanliness detector. The analysis magnification is 2.5, the average filter is 3×3 with a length of 31, and the Laplace filter is 5×5 with a length of 1.

500. After scanning, the number of particles of each size is recorded.

7. The method for detecting the quantity and elemental composition of dust particles in a battery material packaging workshop according to claim 6, characterized in that, The total number of particles is calculated as follows: Total number of particles (PCS / kg) = Number of particles of each size × Sum of coefficients; The coefficients for each particle size in the formula are as follows: when the particle size is greater than 100μm, the corresponding coefficient is 1; when the particle size is in the range of 25~100μm, the corresponding coefficient is 0.5; when the particle size is less than 25μm, the corresponding coefficient is 0.

8. The method for detecting the quantity and elemental composition of dust particles in a battery material packaging workshop according to claim 1, characterized in that, Step (3) The filter membrane of the collected sample is attached to the sample holder base with fixative and allowed to air dry naturally. Then, the elemental composition of the particles is tested by scanning with a JOMESAPSE scanning electron microscope. The parameters are set as follows: low vacuum full scan, magnification 1 mm, elements of interest Cu, Zn, and Cr, EDS count 10000, timeout 5 s, maximum diameter 25 μm. After the scan is completed, the elemental mass percentage of each particle is checked. The particle composition is determined by the elemental mass percentage of each particle, the origin of the particles is inferred, and the element with the highest content is identified as the element particle. The number of particles of each type is calculated.

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