Lithium ion battery reverse particle size analysis method and system

Abstract

The invention provides a reverse particle size analysis method and system for a lithium ion battery, and the method comprises the steps: carrying out the detailed disassembly, cleaning, adhesion, stripping and high-temperature treatment of a to-be-analyzed cell, can accurately analyze the particle size distribution of an electrode active material in the positive and negative electrode materials of the lithium ion battery, guarantees the purity and activity of the electrode active material, and improves the detection accuracy. Therefore, the particle size analysis result is more accurate and reliable. According to the invention, the performance of the battery material is optimized, the safety of the battery is improved, the service life of the battery is prolonged, and important data support is provided for research, development and improvement of the battery material.

Description

Technical Field

[0001] The technical field of the present invention belongs to the technical field of lithium-ion batteries, and in particular, relates to a reverse particle size analysis method and system for lithium-ion batteries. Background Art

[0002] Lithium-ion batteries (LIBs) are widely used in mobile devices, electric vehicles, and energy storage systems due to their advantages such as high energy density, high voltage, long life, and low self-discharge rate. Among them, the battery pole piece is a key component of the battery cell. The battery pole piece is usually composed of a current collector (in lithium-ion batteries, the current collector mainly refers to metal foil, the positive electrode current collector is usually aluminum foil, and the negative electrode current collector is usually copper foil) and a pole piece material coated thereon, which is dried and stamped. The pole piece material (positive electrode material or negative electrode material) is a mixture of active substances, conductive agents, binders, etc. The active substance is mainly responsible for storing and releasing lithium ions during the charging and discharging process of the battery.

[0003] Measuring particle size in a battery cell mainly refers to measuring the particle size of the active material in the electrode material. This is because the particle size distribution of the active material has an important influence on the physical and electrochemical properties of the battery, including the battery's capacity, energy density, charge and discharge performance, cycle performance, and safety performance.

[0004] In traditional methods, the battery cell pole pieces are usually physically scraped directly to obtain powder samples of positive and negative electrode materials. Then, instruments such as SEM (scanning electron microscope) are used to perform particle size analysis on the scraped powder samples. Based on the SEM analysis results, the particle size distribution of the electrode material is evaluated. However, since the powder samples are affected by the binder and conductive agent inside the battery cell, the particle size test results are too large and cannot truly reflect the original particle size of the pole piece material, resulting in an inability to accurately evaluate the material formula. Summary of the invention

[0005] The object of the present invention is to provide a lithium-ion battery reverse particle size analysis method and system for analyzing the particle size of the electrode active material at the electrode level in an unknown battery cell system.

[0006] According to a first aspect of the present invention, a method for reverse particle size analysis of a lithium ion battery is provided, comprising the following steps:

[0007] Disassemble the battery cells to be analyzed, separate the electrode plates, clean and dry them;

[0008] Using a physical stripping method to remove the diaphragm material adhered to the electrode plate;

[0009] placing the electrode plate into a first solution for ultrasonic immersion until all the electrode material coated on the electrode current collector is peeled off into the first solution to obtain a suspension;

[0010] Filter and dry the suspension to obtain electrode powder;

[0011] Process the electrode powder within a set temperature range to obtain electrode active material;

[0012] Analyze the particle size of the electrode active material using a particle size analyzer.

[0013] Furthermore, in the reverse particle size analysis method, the separated electrode plate includes any one of a positive electrode plate and a negative electrode plate.

[0014] Furthermore, in the reverse particle size analysis method, when the separated electrode plate is a positive electrode plate, the first solution includes an N-methyl-2-pyrrolidone solution or a dimethyl sulfoxide solution; when the separated electrode plate is a negative electrode plate, the solvent in the first solution includes deionized water or reverse osmosis water.

[0015] Furthermore, in the reverse particle size analysis method, the electrode powder includes electrode materials coated on the electrode current collector.

[0016] Furthermore, in the reverse particle size analysis method, the electrode materials coated on the electrode current collector include electrode active material, electrode conductive agent, and electrode binder.

[0017] Furthermore, in the reverse particle size analysis method, the set temperature range is 200°C to 600°C.

[0018] Furthermore, in the reverse particle size analysis method, the physical stripping method includes at least one of stretching stripping, shear stripping, and stripping agent stripping.

[0019] According to the second aspect of the present invention, there is provided a reverse particle size analysis system for a lithium-ion battery, including:

[0020] A disassembly module for disassembling a lithium-ion battery cell to be analyzed and separating out the electrode plates;

[0021] A cleaning module for cleaning the separated electrode plates;

[0022] A stripping module for removing the separator material adhered to the electrode plates by a physical stripping method, and for putting the stripped electrode plates into a first solution for ultrasonic soaking to strip the electrode materials from the current collector into the solution to obtain a suspension;

[0023] A filtering module for filtering the suspension to separate out the electrode powder;

[0024] A drying module for drying the separated electrode plates and the separated electrode powder;

[0025] A heat treatment module for treating the dried electrode powder within a set temperature range to obtain electrode active materials; and

[0026] A particle size analysis module for analyzing the particle size of the electrode active materials and obtaining particle size distribution data.

[0027] Furthermore, in the reverse particle size analysis system of the lithium-ion battery, the separated electrode plates include either a positive electrode plate or a negative electrode plate; when the separated electrode plate is a positive electrode plate, the first solution includes an N-methyl-2-pyrrolidone solution or a dimethyl sulfoxide solution; when the separated electrode plate is a negative electrode plate, the solvent in the first solution includes deionized water or reverse osmosis water.

[0028] Furthermore, in the reverse particle size analysis system of the lithium-ion battery, the set temperature range is 200°C to 600°C.

[0029] Compared with the prior art, the present invention has at least the following technical effects:

[0030] The present invention provides a method and system for reverse particle size analysis of a lithium-ion battery. By performing meticulous disassembly, cleaning, adhesion, peeling, and high-temperature treatment on the battery cell to be analyzed, it is possible to accurately analyze the particle size distribution of the electrode active materials in the positive and negative electrode materials of the lithium-ion battery, ensure the purity and activity of the electrode active materials, thereby making the particle size analysis results more accurate and reliable. It helps to optimize the performance of the battery materials, improve the safety and service life of the battery, and also provides important data support for the research and development and improvement of battery materials. Description of the Drawings

[0031] Figure 1 It is a flowchart of the method for reverse particle size analysis of a lithium-ion battery in an embodiment of the present invention;

[0032] Figure 2 It is a flowchart of the method for reverse particle size analysis of a lithium-ion battery in another embodiment of the present invention;

[0033] Figure 3 It is a SEM of the positive electrode active material particles measured by scraping powder test before treatment in an embodiment of the present invention;

[0034] Figure 4 It is a SEM of the treated positive electrode active material particles measured after treatment in an embodiment of the present invention;

[0035] Figure 5Another embodiment of the present invention is the SEM of the negative electrode active material particles measured by the scraping powder test before treatment;

[0036] Figure 6 Another embodiment of the present invention is the SEM of the treated negative electrode active material particles measured after treatment. Detailed implementation manners

[0037] The following will describe in more detail a method and system for reverse particle size analysis of a lithium-ion battery according to the present invention with reference to schematic diagrams, in which preferred embodiments of the present invention are shown. It should be understood that those skilled in the art can modify the present invention described herein while still achieving the advantageous effects of the present invention. Therefore, the following description should be understood as a broad guidance for those skilled in the art and not as a limitation to the present invention.

[0038] For clarity, not all features of the actual embodiments are described. In the following description, well-known functions and structures are not described in detail because they would obscure the present invention with unnecessary details. It should be considered that in the development of any actual embodiment, a large number of implementation details must be made to achieve the specific goals of the developer, such as changing from one embodiment to another according to the relevant system or business limitations. Additionally, it should be considered that such development work may be complex and time-consuming, but it is only routine work for those skilled in the art.

[0039] In the following paragraphs, the present invention will be described more specifically by way of example with reference to the accompanying drawings. The advantages and features of the present invention will be clearer according to the following description. It should be noted that the accompanying drawings are all in very simplified forms and use non-precise scales, only for the purpose of facilitating and clearly assisting in explaining the purpose of the embodiments of the present invention.

[0040] I. Preparation of the positive electrode sheet

[0041] Material ratio: Mix pure LFO (lithium iron oxide, as the positive electrode active material), PVDF (polyvinylidene fluoride, as the binder), and SP (carbon black, as the conductive agent) with a known particle size in a mass ratio of 80:10:5.

[0042] Stirring: Mix the above materials with an appropriate amount of NMP solvent in a blender until a uniform slurry (as the positive electrode material) is formed.

[0043] Coating: Uniformly coat the stirred positive electrode slurry on one side of the aluminum foil.

[0044] Drying: Put the aluminum foil coated with the positive electrode slurry into an oven for drying to remove the solvent and cure the slurry.

[0045] II. Preparation of the negative electrode sheet

[0046] Material ratio: Graphite (as the negative electrode active material), SP (carbon black, as the conductive agent), SBR (styrene-butadiene rubber, as the binder), and PAA (polyacrylic acid, as the thickener) are mixed in a mass ratio of 85:5:5:5.

[0047] Mixing: Mix the above materials with an appropriate amount of solvent in a blender until a uniform slurry (as the negative electrode material) is formed.

[0048] Coating: Uniformly coat the mixed negative electrode slurry on one side of the copper foil.

[0049] Drying: Place the copper foil coated with the negative electrode slurry in an oven for drying to remove the solvent and solidify the slurry.

[0050] III. Cell Assembly

[0051] Stacking: Alternately stack the dried positive electrode sheets and negative electrode sheets, inserting a separator in between to form a multi-layer stacked structure.

[0052] Pressing: Place the stacked structure in a press for pressing to ensure close contact between the electrode sheets and the separator.

[0053] Inserting into the battery case: Insert the pressed stacked structure into the battery case.

[0054] Injecting electrolyte: Inject an appropriate amount of electrolyte through the injection hole.

[0055] Sealing: Seal the battery case to ensure that the electrolyte does not leak.

[0056] Formation: Perform the first charge and discharge on the assembled cell, aiming to activate the battery materials and form a stable solid electrolyte interface (SEI).

[0057] Example 1

[0058] As Figure 1 shown, this example provides a method for analyzing the reverse particle size of a lithium-ion battery, including the following steps:

[0059] S1: Disassemble the cell to be analyzed, separate the positive electrode sheet, and clean and dry it.

[0060] S2: Use a physical peeling method to remove the separator material adhered to the positive electrode sheet.

[0061] S3: Place the positive electrode sheet in a first solution for ultrasonic soaking until all the positive electrode material coated on the positive electrode current collector is peeled off into the first solution to obtain a suspension.

[0062] S4: Filter and dry the suspension to obtain positive electrode powder.

[0063] S5: Treat the positive electrode powder within a set temperature range to obtain the positive electrode active material.

[0064] S6: Analyze the particle size of the positive electrode active material using a particle size analyzer.

[0065] It should be noted that during the assembly process of the battery cell, the positive electrode sheet and the negative electrode sheet are alternately laminated with the separator material by winding or stacking to form the core part of the battery cell, namely the wound core or the stacked structure. Then, this wound core or stacked structure is placed inside the battery cell casing, filled with electrolyte, and sealed. Thus, the electrolyte is distributed inside the battery cell and is in full contact with the positive and negative electrode sheets and the separator material to ensure the normal operation of the battery.

[0066] Specifically, for step S1, when disassembling the battery cell to be analyzed, the battery cell (usually a lithium-ion battery) needs to be disassembled to facilitate access to the internal cell materials. After disassembling the battery cell, the positive electrode sheet needs to be separated, the electrolyte remaining on the positive electrode sheet is washed off using a cleaning solvent, and then dried. A certain amount of the electrode sheet is taken for backup. The cleaning solvent can remove the electrolyte remaining on the electrode sheet and prevent the electrolyte from contaminating the subsequent processes. Among them, the cleaning solvent can be dimethyl carbonate (DMC). DMC is a strongly polar solvent and has a good dissolving effect on components such as lithium salts in the electrolyte, and can effectively remove the residual electrolyte on the electrode sheet.

[0067] Furthermore, for step S2, a physical peeling method is used to remove the separator material adhered to the positive electrode sheet. The physical peeling method includes at least one of stretching peeling, shear peeling, and peeling agent peeling.

[0068] Specifically, take a stretching peeling method as an example. Using transparent tape, the ceramic and glue on the separator adhered to the surface of the positive electrode sheet are pulled off the substrate positive electrode sheet under an external force to remove the separator material adhered to the positive electrode sheet.

[0069] Specifically, for step S3, the first solution includes N-methyl-2-pyrrolidone (NMP) solution or dimethyl sulfoxide solution. During the battery homogenization process, N-methyl-2-pyrrolidone (NMP) can well dissolve the binder (such as PVDF), lithium salt, and conductive substances as a solvent, enabling them to come into full and uniform contact with each other. After the homogenization is coated on the aluminum foil and dried, it goes through processes such as recovery, pressing, and vacuum drying to manufacture the battery cell. In addition, dimethyl sulfoxide (DMSO) can also be used as the solvent of the first solution because NMP and DMSO share the following characteristics:

[0070] Polar solvents: Both NMP and DMSO are polar aprotic solvents with high dielectric constants and degrees of polarity. This polarity enables them to effectively dissolve a variety of organic and inorganic substances, including the binder PVDF.

[0071] Good dissolving ability: Both can dissolve components such as active materials, binders, and conductive agents in the battery slurry well, thus ensuring the uniformity and stability of the slurry.

[0072] Chemical stability: Both NMP and DMSO have good chemical stability and are not prone to chemical reactions during battery preparation.

[0073] As an example, for step S3, the positive electrode plate is placed in N-methyl-2-pyrrolidone for ultrasonic soaking until all the positive electrode material coated on the positive electrode current collector is peeled off into the solution to obtain a suspension.

[0074] It should be noted that N-methyl-2-pyrrolidone (NMP) is a preferred highly polar aprotic solvent in this embodiment. The binder is generally a substance used to stick the active material, conductive agent, and current collector together. NMP has a strong dissolving ability and can effectively dissolve adhesives such as polyvinylidene fluoride (PVDF), thus enabling the positive electrode material on the positive electrode plate to be peeled off from the positive electrode current collector into the solution. NMP has a high dielectric constant and degree of polarity. The nitrogen atom in its molecule has a high electronegativity and can undergo electrostatic interactions with positively charged ions or partial negative charges in polar molecules. In addition, the negatively charged nitrogen atom in the NMP molecule can form hydrogen bonds with positively charged hydrogen atoms in other molecules. The formation of these hydrogen bonds further promotes the interaction and dissolution between NMP and other substances. The polar characteristics of NMP enable it to interact with many polar or ionic compounds, break or reduce the intermolecular forces between the solvent and solute, thereby promoting dissolution and increasing solubility. Therefore, it is applied as a battery positive electrode solvent.

[0075] In addition, ultrasonic soaking can improve the cleaning efficiency and accelerate the dissolution process of NMP for binder residues. During ultrasonic soaking, the mechanical vibration of ultrasonic waves can promote NMP to penetrate into the pore structure of the electrode plate, accelerate the peeling process, and enable the positive electrode material to be more thoroughly peeled off from the current collector into the solution.

[0076] It can be understood that the above examples cannot be used as a limitation to the present invention. Those skilled in the art can flexibly select other substances that can achieve this process based on the above ideas, and all of these should be regarded as being covered within the scope of the present invention.

[0077] In this embodiment, the obtained suspension contains the positive electrode material coated on the positive electrode current collector (such as aluminum foil). The positive electrode material includes a positive electrode active material, a positive electrode conductive agent, and a positive electrode binder. The positive electrode conductive agent includes carbon black, and the positive electrode binder includes polyvinylidene fluoride (PVDF).

[0078] After that, as described in step S4, the suspension is filtered and dried to obtain positive electrode powder. By filtration and drying, impurities and unnecessary solvents in the suspension can be removed, and relatively pure positive electrode material powder can be obtained, which is beneficial to subsequent analysis of the positive electrode material.

[0079] For step S5: The positive electrode powder is processed within a set temperature range to obtain a positive electrode active material. Specifically, by subjecting the positive electrode powder to high-temperature treatment in a muffle furnace, the binder (such as PVDF) in the positive electrode material can be decomposed. The set temperature range is 200 - 600 °C, its initial decomposition temperature is 350 - 450 °C, and the complete decomposition temperature is 600 °C. At this temperature, the conductive agent will undergo oxidative decomposition, thereby removing organic impurities and obtaining a positive electrode active material with a higher purity. At this time, the positive electrode active material is observed by SEM (scanning electron microscope) as Figure 4 shown.

[0080] It should be noted that the positive electrode active material obtained after high-temperature treatment includes at least one of lithium-rich lithium ferrite, lithium cobaltate, ternary material, and lithium iron phosphate.

[0081] It should be noted that the muffle furnace adopts advanced heating elements and heat-insulating materials, which can quickly reach and stably maintain the required high-temperature environment. This helps with the high-temperature treatment of the electrode sheet materials. Since the temperature uniformity inside the furnace chamber is good, it can ensure that the samples are heated evenly and reduce experimental errors.

[0082] Specifically, for step S6, a particle size analyzer (such as a laser particle size analyzer) is used to measure the particle size of the active material in the sintered positive electrode material. For example, the measured results are compared with the original particle size data provided by the manufacturer to verify the effectiveness and accuracy of the processing flow.

[0083] During the particle size test, based on the SEM analysis results, the particle size distribution of the cathode material is evaluated, and the particle size values of the cathode active material for D10, D50, D90, and D99 are calculated respectively. (Here, D10, D50, D90, and D99 are common particle size distribution parameters, representing the particle size values corresponding to the cumulative distribution percentages of the particles respectively. In other words, they represent that in the particle size cumulative distribution, the particles smaller than this particle size account for 10%, 50%, 90%, and 99% of the total volume or mass, etc.) The particle size values of the cathode active material measured after being processed by the above method are compared with the particle size parameters of the original cathode active material provided by the manufacturer. As shown in Table 1 below:

[0084] Table 1

[0085]

[0086] In summary, from the test results, the binder and conductive agent of the cathode electrode sheet after processing have been removed, and the particle size test results of the cathode active material are basically consistent with the factory parameters.

[0087] Example 2

[0088] As Figure 2 shown, this example provides a reverse particle size analysis method for lithium-ion batteries, including the following steps:

[0089] S1: Disassemble the battery cell to be analyzed, separate the negative electrode sheet, and clean and dry it.

[0090] S2: Use a physical peeling method to remove the separator material adhered to the negative electrode sheet.

[0091] S3: Immerse the negative electrode sheet in a first solution and perform ultrasonic soaking until all the negative electrode material coated on the negative electrode current collector is peeled off into the first solution to obtain a suspension.

[0092] S4: Filter and dry the suspension to obtain negative electrode powder.

[0093] S5: Process the negative electrode powder within a set temperature range to obtain negative electrode active material.

[0094] S6: Analyze the particle size of the negative electrode active material using a particle size analyzer.

[0095] Specifically, the procedure is the same as in Example 1. For step S1, when disassembling the battery cell to be analyzed, the battery cell (usually a lithium-ion battery) needs to be disassembled to facilitate access to the internal cell materials. After disassembling the cell, the negative electrode tab needs to be separated, and the electrolyte remaining on the negative electrode tab is washed off with dimethyl carbonate (DMC) and then dried. A certain amount of the electrode tab is taken for preparation. The cleaning solvent can remove the electrolyte remaining on the electrode tab and prevent the electrolyte from contaminating the subsequent processes.

[0096] Further, for step S2, a physical stripping method is used to remove the separator material adhered to the negative electrode tab. The physical stripping method includes at least one of stretching stripping, shear stripping, and stripping agent stripping.

[0097] Specifically, as an example of the stretching stripping method, the ceramic and glue on the separator adhered to the surface of the negative electrode tab are pulled off the substrate negative electrode tab under an external force using transparent tape to remove the separator material adhered to the negative electrode tab.

[0098] Specifically, for step S3, the solvent in the first solution includes deionized water or reverse osmosis water. Among them, deionized water is preferably selected as the negative electrode solvent because the ion content of deionized water is low and it can be prepared by techniques such as reverse osmosis and ion exchange. In addition, due to its high purity, deionized water can effectively exclude the interference of impurities on the homogenization performance, not only significantly improving the quality and stability of the homogenization, but also extending the service life of the battery by reducing corrosion and oxidation inside the battery.

[0099] For step S3, the negative electrode tab is put into deionized water for ultrasonic soaking until all the negative electrode material coated on the negative electrode current collector is stripped into the solution to obtain a suspension. Specifically, deionized water can clean the impurities, residual electrolyte, and other substances on the surface of the negative electrode tab. Then, using the mechanical vibration generated by ultrasonic soaking, the negative electrode material on the negative electrode tab can be effectively stripped from the negative electrode current collector into the solution. Among them, the ultrasonic cleaning frequency during the ultrasonic soaking process is usually 60 kHz, the power is 1.5 kW, and the ultrasonic time is controlled between 10 seconds and 40 seconds to ensure the complete separation of the negative electrode material and the negative electrode current collector.

[0100] It can be understood that the above examples cannot be used as a limitation to the present invention. Those skilled in the art can flexibly select other substances that can achieve this process based on the above idea, and all of these should be regarded as covered within the scope of the present invention.

[0101] In this embodiment, the obtained suspension contains the negative electrode material coated on the negative electrode current collector (such as copper foil). The negative electrode material includes a negative electrode active material, a negative electrode conductive agent, and a negative electrode binder. The negative electrode conductive agent includes carbon black, and the negative electrode binder includes at least one of styrene-butadiene rubber, carboxymethyl cellulose solution, and polyacrylic acid.

[0102] After that, the suspension is filtered and dried as described in step S4 to obtain negative electrode powder. Filtration and drying can remove impurities and unnecessary solvents in the suspension, and obtain relatively pure negative electrode material powder, which is beneficial for subsequent analysis of the negative material.

[0103] Furthermore, for step S5: the negative electrode powder is heat-treated in a muffle furnace, and the temperature is controlled within the range of 200°C to 450°C. The heat treatment helps to remove organic impurities in the negative electrode material, such as residual binder and conductive agent, etc., so as to obtain a negative electrode active material with higher purity. At this time, the negative electrode active material is observed by SEM (scanning electron microscope) as Figure 6 shown.

[0104] It should be noted that the negative electrode active material obtained after heat treatment includes at least one of graphite, silicon-carbon composite material, and silicon-oxygen composite material.

[0105] For step S6, a particle size analyzer (such as a laser particle size analyzer) is used to test the particle size of the active material in the sintered negative electrode material. The measured results are compared with the original particle size data provided by the manufacturer to verify the effectiveness and accuracy of the processing flow.

[0106] Specifically, during the particle size test, according to the SEM analysis results, the particle size distribution of the negative electrode material is evaluated, and D10, D50, D90, and D99 are commonly used particle size distribution parameters, which respectively represent the particle size values corresponding to the percentage of particle cumulative distribution. In other words, they respectively represent that in the particle size cumulative distribution, the particles smaller than this particle size account for 10%, 50%, 90%, and 99% of the total volume or mass, etc. The particle size values of the negative electrode active material measured after being processed by the above method are compared with the original particle size parameters of the negative electrode active material provided by the manufacturer. As shown in Table 2 below:

[0107] Table 2

[0108]

[0109] In summary, from the test results, the binder and conductive agent of the processed negative electrode sheet have been removed, and the particle size test results of the negative electrode active material are basically consistent with the factory parameters.

[0110] Comparative Example 1

[0111] In the material analysis of lithium-ion batteries, traditional particle size analysis methods generally include the following steps:

[0112] 1. Physical scraping: First, disassemble the positive electrode sheet from the battery cell. Then, directly use a scraper or other physical tools to physically scrape the battery cell electrode sheet to obtain a powder sample of the positive electrode material. This process requires careful operation to avoid damaging the electrode sheet while ensuring that the scraped material is as complete as possible.

[0113] 2. Sample collection: The scraped powder sample will be collected into a clean container to ensure that the sample is not contaminated and is prepared for subsequent analysis.

[0114] 3. Particle size analysis:

[0115] Place the collected powder sample in a scanning electron microscope (SEM) for analysis. The SEM can provide high-resolution images and can clearly observe the morphology and surface characteristics of the particles. Figure 3 Figure of the particle image of the positive electrode active material obtained by SEM after using the powder scraping test method.

[0116] From the images obtained by SEM, researchers can use image analysis software (such as a laser particle size analyzer) to measure the particles and calculate the particle diameter and particle size distribution.

[0117] During the particle size test, according to the SEM analysis results, evaluate the particle size distribution of the positive electrode material obtained by the powder scraping test, and calculate the particle size values of D10, D50, D90, and D99 of the positive electrode active material respectively. (D10, D50, D90, and D99 are commonly used particle size distribution parameters, which respectively represent the particle size values corresponding to the percentage of particle cumulative distribution. In other words, they respectively represent that in the particle size cumulative distribution, the particles smaller than this particle size account for 10%, 50%, 90%, and 99% of the total volume or mass, etc.). Compare the particle size values of the positive electrode active material measured by the powder scraping test method before the electrode sheet treatment and the method in Example 1 with the original particle size parameters of the positive electrode active material provided by the manufacturer. As shown in Table 3 below:

[0118] Table 3

[0119]

[0120] From the test results in Table 3 above, it can be seen that there is more binder and conductive agent bonded around the positive electrode active material particles obtained by the powder scraping test method before the electrode sheet treatment, and the particle size is generally larger; after the electrode sheet is treated using the method of Example 1, the binder and conductive agent of the electrode sheet are removed, and the particle size test results of the obtained positive electrode active material are basically consistent with the factory parameters provided by the manufacturer. At this time, the measured particle size is close to its true particle size.

[0121] Comparative Example 2

[0122] In the material analysis of lithium-ion batteries, traditional particle size analysis methods generally include the following steps:

[0123] 1. Physical scraping: First, disassemble the negative electrode sheet from the battery cell. Then, directly use a scraper or other physical tools to physically scrape the battery cell electrode sheet to obtain a powder sample of the negative electrode material.

[0124] 2. Sample collection: The scraped powder sample will be collected into a clean container to ensure that the sample is not contaminated and is prepared for subsequent analysis.

[0125] 3. Particle size analysis:

[0126] Place the collected powder sample in a scanning electron microscope (SEM) for analysis. The SEM can provide high-resolution images and can clearly observe the morphology and surface characteristics of the particles. As Figure 5 shown, it is the particle image of the negative electrode active material obtained by SEM after using the powder scraping test method.

[0127] Using the same processing method as Comparative Example 1, during the particle size test, according to the SEM analysis results, evaluate the particle size distribution of the negative electrode material obtained by the powder scraping test, and calculate the particle size values of D10, D50, D90, and D99 of the negative electrode active material respectively. (D10, D50, D90, and D99 are commonly used particle size distribution parameters, which respectively represent the particle size values corresponding to the percentage of particle cumulative distribution. In other words, they respectively represent that in the particle size cumulative distribution, the particles smaller than this particle size account for 10%, 50%, 90%, and 99% of the total volume or mass, etc.). Compare the particle size values of the negative electrode active material measured by the powder scraping test method before the electrode sheet treatment and the method in Example 1 with the original particle size parameters of the negative electrode active material provided by the manufacturer. As shown in Table 4 below:

[0128] Table 4

[0129]

[0130]

[0131] From the test results in Table 4 above, it can be seen that there is more binder and conductive agent bonded around the negative electrode active material particles obtained by the powder scraping test method before the electrode sheet treatment, and the particle size is generally larger; since the binder and conductive agent of the electrode sheet have been removed after the electrode sheet is treated using the method of Example 2, the particle size test results of the obtained negative electrode active material are basically the same as the factory parameters provided by the manufacturer, and the measured particle size is close to its true particle size at this time.

[0132] Example 3

[0133] Embodiment 3 provides a reverse particle size analysis system for lithium-ion batteries, including: a disassembly module, a cleaning module, a stripping module, a filtering module, a drying module, a heat treatment module, and a particle size analysis module.

[0134] The disassembly module is used to disassemble the lithium-ion battery cell to be analyzed and separate the positive electrode plate.

[0135] The cleaning module is used to clean the separated positive electrode plate.

[0136] The stripping module is used to remove the separator material adhered to the positive electrode plate by a physical stripping method, and to ultrasonically soak the stripped positive electrode plate in a first solution to strip the positive electrode material from the current collector into the solution to obtain a suspension.

[0137] Wherein, the first solution includes an N-methyl-2-pyrrolidone solution or a dimethyl sulfoxide solution.

[0138] As an example, the stripping module can ultrasonically soak the positive electrode plate in N-methyl-2-pyrrolidone until all the positive electrode material coated on the positive electrode current collector is stripped into the solution to obtain a suspension.

[0139] It should be noted that N-methyl-2-pyrrolidone (NMP) is a preferred high-polarity aprotic solvent in this embodiment. The binder is generally a substance used to bond the active material, conductive agent, and current collector together. NMP has a strong dissolving ability and can effectively dissolve adhesives such as polyvinylidene fluoride (PVDF), so as to realize the stripping of the positive electrode material on the positive electrode plate from the positive electrode current collector into the solution. NMP has a high dielectric constant and polarity. The nitrogen atom in its molecule has a high electronegativity and can undergo electrostatic interaction with positively charged ions or partial negative charges in polar molecules. In addition, the negatively charged nitrogen atom in the NMP molecule can form hydrogen bonds with the positively charged hydrogen atoms in other molecules, and the formation of this hydrogen bond further promotes the interaction and dissolution between NMP and other substances. The polar characteristics of NMP enable it to interact with many polar or ionic compounds, break or reduce the interaction force between the solvent and the solute, thereby promoting dissolution and increasing solubility, so it is applied as a battery positive electrode solvent.

[0140] In addition, ultrasonic soaking can improve the cleaning efficiency and accelerate the dissolution process of NMP for the binder residue. The mechanical vibration of ultrasonic waves during ultrasonic soaking can promote NMP to penetrate into the pore structure of the electrode plate, accelerate the stripping process, and make the positive electrode material more thoroughly stripped from the current collector into the solution.

[0141] A filtering module for filtering the suspension to separate the positive electrode powder.

[0142] A drying module for drying the separated positive electrode sheet and the separated positive electrode powder.

[0143] A heat treatment module for treating the dried positive electrode powder within a set temperature range to obtain positive electrode active materials. The set temperature range is 200°C to 600°C.

[0144] As an example, the heat treatment module treats the positive electrode powder within the set temperature range to obtain positive electrode active materials. Specifically, treating the positive electrode powder in a muffle furnace at high temperature can decompose the binder (such as PVDF) in the positive electrode material. The set temperature range is 200 - 600°C, its initial decomposition temperature is 350 - 450°C, and the complete decomposition temperature is 600°C. At this temperature, the conductive agent will undergo oxidative decomposition, thereby removing organic impurities and obtaining positive electrode active materials with higher purity.

[0145] It should be noted that the positive electrode active materials obtained after high-temperature treatment include at least one of lithium-rich lithium ferrate, lithium cobaltate, ternary materials, and lithium iron phosphate.

[0146] It should be noted that the muffle furnace uses advanced heating elements and heat-insulating materials, which can quickly reach and stably maintain the required high-temperature environment. This helps in the high-temperature treatment of the electrode sheet materials. Since the temperature uniformity inside the furnace chamber is good, it can ensure that the samples are heated evenly and reduce experimental errors.

[0147] A particle size analysis module for analyzing the particle size of the positive electrode active materials to obtain particle size distribution data.

[0148] As an example, the particle size analysis module uses a particle size analysis instrument (such as a laser particle size analyzer) to measure the particle size of the active materials in the sintered negative electrode material. Compare the measured results with the original particle size data provided by the manufacturer to verify the effectiveness and accuracy of the processing flow.

[0149] Example Four

[0150] This Example Four provides a reverse particle size analysis system for lithium-ion batteries, including: a disassembly module, a cleaning module, a peeling module, a filtering module, a drying module, a heat treatment module, and a particle size analysis module.

[0151] A disassembly module for disassembling the lithium-ion battery cell to be analyzed and separating the negative electrode sheet.

[0152] A cleaning module for cleaning the separated negative electrode sheet.

[0153] The stripping module is used to remove the separator material adhered to the negative electrode sheet by means of physical stripping, and to immerse the stripped negative electrode sheet in a first solution for ultrasonic soaking, so that the negative electrode material is stripped from the current collector into the solution to obtain a suspension. The solvent in the first solution includes deionized water and reverse osmosis water.

[0154] As an example, in the stripping module, the solvent in the first solution includes deionized water or reverse osmosis water. Among them, deionized water is preferably selected as the negative electrode solvent. Since the ion content of deionized water is relatively low, it can be prepared by technologies such as reverse osmosis and ion exchange. In addition, due to its high purity, deionized water can effectively exclude the interference of impurities on the homogenization performance, not only can significantly improve the quality and stability of the homogenization, but also can extend the service life of the battery by reducing corrosion and oxidation inside the battery.

[0155] Further, the negative electrode sheet is immersed in deionized water for ultrasonic soaking until all the negative electrode material coated on the negative electrode current collector is stripped into the solution to obtain a suspension. It should be noted that after deionized water can clean the impurities, residual electrolyte and other substances that may affect the battery performance on the surface of the negative electrode sheet, the mechanical vibration generated by ultrasonic soaking can effectively strip the negative electrode material on the negative electrode sheet from the negative electrode current collector into the solution. Among them, the ultrasonic cleaning frequency during the ultrasonic soaking process is usually 60 kHz, the power is 1.5 kW, and the ultrasonic time is controlled between 10 seconds and 40 seconds to ensure the complete separation of the negative electrode material and the negative electrode current collector.

[0156] The filtration module is used to filter the suspension to separate the negative electrode powder.

[0157] The drying module is used to dry the separated negative electrode sheet and the separated negative electrode powder.

[0158] The heat treatment module is used to process the dried negative electrode powder within a set temperature range to obtain negative electrode active materials. The set temperature range is 200°C to 450°C.

[0159] As an example, the negative electrode powder is heat-treated in a muffle furnace, and the temperature is controlled at 200°C

[0160] ~450°C. The high-temperature treatment helps to remove organic impurities in the negative electrode material, such as residual binder and conductive agent, etc., so as to obtain negative electrode active materials with higher purity.

[0161] It should be noted that the negative electrode active materials obtained after high-temperature treatment include at least one of graphite, silicon-carbon composite materials and silicon-oxygen composite materials.

[0162] A particle size analysis module is used to perform particle size analysis on the negative electrode active material to obtain particle size distribution data.

[0163] As an example, the particle size analysis module uses a particle size analysis instrument (such as a laser particle size analyzer) to measure the particle size of the active material in the sintered negative electrode material. The measured results are compared with the original particle size data provided by the manufacturer to verify the effectiveness and accuracy of the processing flow.

[0164] In summary, by carefully disassembling, cleaning, adhering, peeling, and heat-treating the battery cell to be analyzed, the particle size distribution of the electrode active materials in the positive and negative electrodes of the lithium-ion battery can be accurately analyzed, ensuring the purity and activity of the electrode active materials, thereby making the particle size analysis results more accurate and reliable. This helps to optimize the performance of battery materials, improve the safety and service life of the battery, and also provides important data support for the research and development and improvement of battery materials.

[0165] The above are only the preferred embodiments of the present invention and do not impose any limitation on the present invention. Any person skilled in the art within the technical field of the present invention, without departing from the technical solution of the present invention, makes any form of equivalent substitution or modification and other changes to the technical solution and technical content disclosed by the present invention, all of which are within the content of the technical solution of the present invention and still fall within the protection scope of the present invention.

Claims

1. A lithium ion battery reverse particle size analysis method, characterized in that: The following steps are involved: Disassemble the battery cells to be analyzed, separate the electrode plates, clean and dry them; Using a physical stripping method to remove the diaphragm material adhered to the electrode plate; The electrode plate is placed in a first solution for ultrasonic immersion until all the electrode material coated on the electrode current collector is peeled off into the first solution to obtain a suspension; filtering and drying the suspension to obtain electrode powder; Treating the electrode powder within a set temperature range to obtain an electrode active material; The particle size of the electrode active material is analyzed using a particle size analyzer.

2. The reverse particle size analysis method according to claim 1, characterized in that: The separated electrode plates include any one of positive electrode plates and negative electrode plates.

3. The reverse particle size analysis method according to claim 2, characterized in that: When the separated electrode plate is a positive electrode plate, the first solution includes N-methyl-2-pyrrolidone solution or dimethyl sulfoxide solution; when the separated electrode plate is a negative electrode plate, the solvent in the first solution includes deionized water or reverse osmosis water.

4. The particle size analysis method according to claim 2, characterized in that: The electrode powder includes electrode materials coated from an electrode current collector.

5. The particle size analysis method according to claim 4, characterized in that: The electrode material coated on the electrode current collector includes an electrode active material, an electrode conductive agent and an electrode binder.

6. The reverse particle size analysis method according to claim 1, characterized in that: The set temperature range is 200°C to 600°C.

7. The particle size analysis method according to claim 1, characterized in that: The physical peeling method includes at least one of stretching peeling, shear peeling, and peeling agent peeling.

8. A lithium-ion battery reverse particle size analysis system, characterized in that: include: Disassembly module, used to disassemble the lithium-ion battery cells to be analyzed and separate the electrode plates; A cleaning module, used for cleaning the separated electrode plates; A stripping module, used to remove the diaphragm material adhered to the electrode plate by a physical stripping method, and to place the stripped electrode plate into a first solution for ultrasonic immersion, so that the electrode material is stripped from the current collector into the solution to obtain a suspension; A filtering module, used to filter the suspension to separate the electrode powder; A drying module, used for drying the separated electrode sheets and separated electrode powder; A heat treatment module is used to treat the dried electrode powder within a set temperature range to obtain an electrode active material; as well as The particle size analysis module is used to perform particle size analysis on the electrode active material to obtain particle size distribution data.

9. The lithium-ion battery reverse particle size analysis system according to claim 8, characterized in that: The separated electrode plate includes any one of a positive electrode plate and a negative electrode plate; when the separated electrode plate is a positive electrode plate, the first solution includes an N-methyl-2-pyrrolidone solution or a dimethyl sulfoxide solution; when the separated electrode plate is a negative electrode plate, the solvent in the first solution includes deionized water or reverse osmosis water.

10. The lithium-ion battery reverse particle size analysis system according to claim 8, characterized in that: The set temperature range is 200°C to 600°C.

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