Electrode recycling methods

Abstract

This application relates to a method for recycling electrode sheets. The method includes the following steps: testing the elastic modulus of the electrode sheets, and testing the powder shedding rate of the electrode sheets using the cross-cut adhesion method; sorting out electrodes with an elastic modulus not exceeding 250 N / cm². 2 Electrode sheets with a powder loss rate exceeding 40% are subjected to pulverization to prepare electrode powder. The electrode powder separated in this application is easy to peel off, and a peeling rate of not less than 95% can be achieved through 1-2 pulverization processes. At the same time, it can effectively reduce the impurity content in the electrode powder, with the mass ratio of electrode powder with low impurity content not less than 65%. It has high recovery efficiency, short recovery process, and good economic benefits.

Description

Technical Field

[0001] This application relates to the technical field of lithium battery recycling, and in particular to a method for recycling electrode sheets. Background Technology

[0002] Lithium-ion batteries are widely used due to their unique advantages such as high energy density, high specific capacity, low self-discharge, no memory effect, and long cycle life, resulting in a large number of waste lithium-ion batteries. Waste lithium-ion batteries contain metallic resources such as lithium, iron, cobalt, manganese, copper, and aluminum. Recycling and reusing waste lithium-ion batteries has significant economic and environmental benefits.

[0003] In the recycling of spent lithium batteries, the electrode sheet typically requires separating the electrode powder and the current collector, and then recycling the electrode powder and the current collector separately. However, traditional electrode powder and current collector separation processes suffer from low electrode powder stripping rates and high impurity content. Summary of the Invention

[0004] Therefore, it is necessary to provide a method for recovering electrode sheets to overcome the problems of low electrode sheet stripping rate and high impurity content in traditional electrode powder and current collector separation processes.

[0005] In a first aspect, this application provides a method for recycling electrode sheets, comprising the following steps:

[0006] The elastic modulus of the electrode was tested, and the powder shedding rate of the electrode was tested using the cross-cut test.

[0007] Those with an elastic modulus not exceeding 250 N / cm² were sorted out. 2 Electrode sheets with a powder loss rate exceeding 40% are then ground into powder to prepare electrode powder.

[0008] In one embodiment, testing the elastic modulus of the electrode includes the following steps:

[0009] An external force is applied to the electrode to bend it into a U-shape, and the elastic modulus of the electrode is calculated based on the torque balance.

[0010] In one embodiment, the electrode is square, with side length L, thickness T, thickness x of the electrode powder layer, bending diameter D, external force F, and elastic modulus ε. The elastic modulus of the electrode is calculated according to the following formula:

[0011] .

[0012] In one embodiment, the side length L of the electrode is 4cm to 8cm.

[0013] In one embodiment, the thickness T of the electrode is 120 μm to 300 μm.

[0014] In one embodiment, the thickness x of the electrode powder layer in the electrode sheet is 50 μm to 150 μm.

[0015] In one embodiment, the bending diameter D of the electrode is 0.01cm to 0.5cm.

[0016] In one embodiment, the external force F is 0.3N~5N.

[0017] In one embodiment, the elastic modulus ε of the electrode is 100 N / cm. 2 ~240N / cm 2 .

[0018] In one embodiment, the powder shedding rate of the electrode is tested using the cross-cut adhesion test, which includes the following steps:

[0019] A 10×10 grid is etched on the electrode sheet. The tape is then applied tightly to the grid for 30 to 120 seconds and then peeled off. The amount of powder falling off is observed, and the powder falling off rate of the electrode sheet is calculated based on the number of grids from which the electrode powder falls off.

[0020] In one embodiment, the powder shedding rate of the electrode is 45% to 95%.

[0021] In one embodiment, the powdering process includes a kneading-type powdering method.

[0022] In one embodiment, the stripping rate of the electrode powder in the electrode sheet is not less than 95%.

[0023] In one embodiment, after the pulverization process, the following steps are also included:

[0024] The powder is sieved using a 100-500 mesh sieve.

[0025] In one embodiment, the mass percentage of the electrode powder layer in the electrode sheet that passes through a 300-mesh sieve is not less than 60%.

[0026] This application has at least the following beneficial effects: Traditional dry powder stripping does not sort the electrode sheets before pulverization, making it difficult to strip the electrode powder from some sheets, resulting in a low stripping rate. Multiple crushing operations are often required to improve the stripping rate, and with each crushing operation, the impurity content in the electrode powder gradually increases. To address these findings, this application, before pulverization, tests the elastic modulus of the electrode sheets and uses the cross-cut adhesion method to test the powder shedding rate, thereby sorting out electrodes with an elastic modulus not exceeding 250 N / cm². 2And electrode sheets with a powder loss rate exceeding 40%. The electrode powder of this type of electrode sheet is easy to peel off, and a peeling rate of no less than 95% can be achieved with only 1 to 2 grindings. At the same time, it can effectively reduce the impurity content in the electrode powder, with the mass ratio of electrode powder with low impurity content being no less than 65%. It has high recycling efficiency, short recycling process, and good economic benefits. Attached Figure Description

[0027] To more clearly illustrate the technical solutions in the embodiments of this application and to more completely understand this application and its beneficial effects, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0028] Figure 1 This is a schematic diagram of a structure in which an external force is used to bend the electrode sheet into a U-shape in one embodiment;

[0029] Figure 2 The graph shows the test results of the cross-cut method for the electrode in Example 1;

[0030] Figure 3 The graph shows the test results of the cross-cut method for the electrode in Example 2;

[0031] Figure 4 The graph shows the test results of the cross-cut method for the electrode in Comparative Example 1.

[0032] Reference numerals: current collector 100, electrode powder layer 200, external force F, electrode thickness T, electrode powder layer thickness x, bending radius D. Detailed Implementation

[0033] To facilitate understanding of this application, the following detailed description is provided in conjunction with specific embodiments. However, this application can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a more thorough and complete understanding of the disclosure of this application.

[0034] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application.

[0035] In this application, "and / or" means any and all combinations of one or more of the related listed items. "At least one" means one or more, such as one, two, or more. "Multiple" or "several" means at least two, such as two, three, etc., and "multi-layered" means at least two layers, such as two, three, etc., unless otherwise expressly and specifically defined. In the description of this application, "several" means at least one, such as one, two, etc., unless otherwise expressly and specifically defined.

[0036] When a numerical range is disclosed in this application, the range is considered continuous and includes the minimum and maximum values ​​of the range, as well as every value between the minimum and maximum values. Furthermore, when the range refers to an integer, it includes every integer between the minimum and maximum values ​​of the range. Additionally, when multiple ranges are provided to describe a feature or characteristic, the ranges may be merged. In other words, unless otherwise specified, all ranges disclosed in this application should be understood to include any and all subranges to which they are included.

[0037] Unless otherwise specified, all steps in this application may be performed sequentially or randomly. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the method may also include step (c), indicating that step (c) may be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0038] In this application, "above" or "below" includes the number itself. For example, "below 1" includes 1.

[0039] Unless otherwise specified, the temperature parameters in this application are permitted to be either constant-temperature treatment or variations within a certain temperature range. It should be understood that the constant-temperature treatment allows temperature fluctuations within the precision range of the instrument control, such as ±5℃, ±4℃, ±3℃, ±2℃, or ±1℃.

[0040] In this application, room temperature refers to indoor temperature, normal temperature, or general temperature. Generally, room temperature can be any of the following temperature ranges: 23℃±2℃, 25℃±5℃, or 20℃±5℃.

[0041] A method for separating electrode powder and current collector in lithium-ion battery electrodes has been reported, including the following steps: mixing water with N-methylpyrrolidone (NMP) to prepare a stripping agent; immersing the electrode in the stripping agent at a temperature of 55℃~140℃ and subjecting it to ultrasonic or mechanical stirring to separate the electrode powder and current collector. This method requires a long separation time, taking up to 3 hours to complete the separation of the active material and the current collector; furthermore, organic solvents such as NMP are toxic and pose a significant environmental hazard.

[0042] A reported method for the industrial separation of electrode materials during the recycling of waste electrode sheets includes the following steps: crushing the waste electrode sheets into fragments of 0.5cm to 30cm; calcining the fragments at a temperature above 370°C in an atmosphere of reducing gas and carbon dioxide to remove the binder from the electrode powder; and then sieving to obtain the electrode material. This method requires high-temperature sintering in a specific atmosphere to remove the binder, which places stringent requirements on the environment and equipment, consumes a lot of energy, and generates the hazardous gas HF during the binder removal process, polluting the environment.

[0043] A method for solid-phase recovery of lithium-ion battery cathode materials based on hollow microspheres has been reported, including the following steps: soaking lithium-ion battery electrodes in an alkaline solution for 10-13 hours to dissolve copper / aluminum current collectors, followed by filtration to obtain filter residue containing the cathode active material. This method can effectively separate electrode materials; however, similar to directly dissolving copper / aluminum foil with acid, the completely dissolved aluminum ions will be adsorbed by the conductive carbon black in the electrode material, making them difficult to remove during the electrode material recovery stage and reducing batch-to-batch consistency.

[0044] As can be seen from the above, the separation processes of electrode powder and current collector are mainly divided into two types: wet stripping and dry stripping. Wet stripping usually uses organic solvents, acids, or alkalis. However, organic solvents have low separation efficiency and cause significant environmental pollution, while acids or alkalis react with the aluminum foil used as the current collector, generating a large amount of H2, and also require wastewater treatment, making industrialization difficult. Dry stripping mostly involves physical crushing of the electrode sheet, requiring multiple crushing processes to improve the electrode powder stripping rate. However, dry stripping often suffers from a low electrode powder stripping rate.

[0045] Based on this, in its first aspect, this application provides a method for recycling electrode sheets.

[0046] In some implementations, the method for recovering the electrode includes the following steps:

[0047] The elastic modulus of the electrode was tested, and the powder shedding rate of the electrode was tested using the cross-cut test.

[0048] Those with an elastic modulus not exceeding 250 N / cm² were sorted out. 2 Electrode sheets with a powder loss rate exceeding 40% are then ground into powder to prepare electrode powder.

[0049] Traditional dry powder stripping does not sort the electrode sheets before pulverization. This makes it difficult to strip the electrode powder from some sheets, resulting in a low stripping rate. Multiple crushing operations are often required to improve the stripping rate, but with each crushing attempt, the impurity content in the electrode powder gradually increases. To address this issue, this application tests the elastic modulus of the electrode sheets before pulverization and uses the cross-cut adhesion method to test the powder shedding rate, thereby sorting out electrodes with an elastic modulus not exceeding 250 N / cm². 2 And electrode sheets with a powder loss rate exceeding 40%. The electrode powder of this type of electrode sheet is easy to peel off, and a peeling rate of no less than 95% can be achieved with only 1 to 2 grindings. At the same time, it can effectively reduce the impurity content in the electrode powder, with the mass ratio of electrode powder with low impurity content being no less than 65%. It has high recycling efficiency, short recycling process, and good economic benefits.

[0050] Understandably, the recycling method provided in this application does not require testing each electrode sheet before pulverization. Instead, it involves extracting several electrodes from the same ton bag for testing and evaluating whether the electrodes in the ton bag are electrodes that are easy to peel off based on the test results of the elastic modulus method and the cross-cut test.

[0051] Understandably, the elastic modulus is an indicator of an object's resistance to elastic deformation, or the ease with which a material undergoes elastic deformation. The higher the elastic modulus, the greater the stress required to cause elastic deformation, meaning the material is more rigid. Generally, the lower the elastic modulus of the electrode, the more thoroughly it bends or curls, the more completely the electrode powder peels off, and the higher the peeling rate. Conversely, if the elastic modulus of the electrode is too high, it cannot be crushed or bent, resulting in a lower peeling rate. After numerous experiments, it was finally verified that when the elastic modulus of the electrode exceeds 250 N / cm², the peeling rate is... 2 The electrode sheet is easy to bend, and the electrode powder on the surface is easy to peel off, thus achieving a peeling rate of not less than 95%.

[0052] Please see Figure 1 This is a schematic diagram of a structure in one embodiment where an external force is used to bend the electrode sheet into a U-shape. For example... Figure 1 As shown, the electrode includes a current collector 100 and an electrode powder layer 200 disposed on at least one surface of the current collector 100.

[0053] Optionally, the electrode is a positive electrode, the current collector 100 of the positive electrode is aluminum foil, and the electrode powder layer 200 of the positive electrode contains a positive electrode active material. The positive electrode active material includes lithium cobalt oxide (such as LiCoO2), lithium nickel oxide (such as LiNiO2), lithium manganese oxide (such as LiMnO2, LiMn2O4), lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, and lithium nickel cobalt manganese oxide (LiNi). x Co yMn z O2), lithium nickel cobalt aluminum oxide (LiNi x Co y Al z O2), lithium nickel cobalt magnesium oxide (LiNi x Co y Mg z O2), lithium nickel iron oxide, lithium iron phosphate (LiFePO4), lithium manganese phosphate (LiMnPO4), lithium manganese iron phosphate and at least one of its modified materials or composite materials, where 0 < x < 1, 0 < y < 1, 0 < z < 1. The electrode powder layer 200 of the positive electrode sheet further contains a binder, and the binder includes at least one of polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), vinylidene fluoride - tetrafluoroethylene - propylene terpolymer, vinylidene fluoride - tetrafluoroethylene - hexafluoropropylene terpolymer, tetrafluoroethylene - hexafluoropropylene terpolymer, fluorinated acrylate resin, polyimide (PI), polyacrylic acid (PAA), and polyacrylonitrile (PAN). The electrode powder layer 200 of the positive electrode sheet further contains a conductive agent, and the conductive agent includes at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0054] Optionally, the electrode sheet is a negative electrode sheet, the current collector 100 of the positive electrode sheet is a copper foil, and the electrode powder layer 200 of the positive electrode sheet contains a negative electrode active material. Among them, the negative electrode active material includes one or more of graphite, nano - silicon, and lithium titanate. The electrode powder layer 200 of the negative electrode sheet further contains a binder including at least one of styrene - butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS)). The electrode powder layer 200 of the negative electrode sheet further contains a conductive agent, and the conductive agent includes at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0055] Optionally, to test the elastic modulus of the electrode sheet, the following steps are included: applying an external force to the electrode sheet to bend it into a U - shape, and calculating the elastic modulus of the electrode sheet according to the moment balance.

[0056] Optionally, the electrode sheet is square, let the side length of the electrode sheet be L, let the thickness of the electrode sheet be T, let the thickness of the electrode powder layer 200 in the electrode sheet be x, let the bending diameter of the electrode sheet be D, let the external force be F, and let the elastic modulus of the electrode sheet be ε, and calculate the elastic modulus of the electrode sheet according to the following formula:

[0057] .

[0058] Understandably, discarded electrode sheets are usually long strips or coiled. Therefore, before conducting elastic modulus testing, the discarded electrode sheets need to be cut to obtain square electrode sheets, which can improve the accuracy and convenience of the measurement. Optionally, the side length L of the electrode sheet is 4cm to 8cm, such as 4cm, 4.5cm, 5cm, 5.5cm, 6cm, 6.5cm, 7cm, 7.5cm, 8cm, and further optionally 5cm.

[0059] Optionally, the thickness T of the electrode is 120μm to 300μm, such as 120μm, 150μm, 180μm, 210μm, 240μm, 270μm and 300μm, and further optionally 140μm to 260μm.

[0060] Understandably, the thickness x of the electrode powder layer 200 is the vertical distance from the surface of the electrode to the current collector 100. Optionally, the thickness x of the electrode powder layer in the electrode is 50 μm to 150 μm, for example, 50 μm, 60 μm, 70 μm, 80 μm, 90 μm, 100 μm, 110 μm, 120 μm, 130 μm, 140 μm and 150 μm, and more preferably 55 μm to 130 μm.

[0061] Understandably, after the electrode is bent into a U-shape, it has a first end and a second end that are parallel to each other, as well as a bent end connecting the first end and the second end. The vertical distance between the outer surface layer of the first end and the outer surface layer of the second end is the bending diameter D. Optionally, the bending diameter D of the electrode is 0.01cm to 0.5cm, for example, 0.01cm, 0.02cm, 0.04cm, 0.06cm, 0.08cm, 0.1cm, 0.15cm, 0.2cm, 0.25cm, 0.3cm, 0.35cm, 0.4cm, 0.45cm and 0.5cm, and further optionally 0.05cm to 0.2cm.

[0062] Optionally, the external force F is 0.3N~5N, for example 0.3N, 0.5N, 0.8N, 1N, 1.5N, 2N, 2.5N, 3N, 3.5N, 4N, 4.5N and 5N, and can be further selected as 0.4N~1.5N.

[0063] Optionally, the elastic modulus of the electrode is ε≤250N / cm. 2 For example, 250 N / cm 2 240N / cm 2 230N / cm 2 220N / cm 2 210N / cm 2 200N / cm 2 190N / cm 2180N / cm 2 170N / cm 2 160N / cm 2 150N / cm 2 100N / cm 2 50N / cm 2 and 10N / cm 2 A further option is 100 N / cm. 2 ~240N / cm 2 A further option is 180 N / cm. 2 ~240N / cm 2 .

[0064] Understandably, the cross-cut adhesion test is a simple and intuitive method for evaluating the bonding performance between the film layer and the substrate. Using the cross-cut test, the shedding of electrode powder in each grid can be directly observed, thereby assessing the bonding performance between the electrode powder layer 200 and the current collector 100, i.e., the ease with which the electrode powder can be peeled off.

[0065] Optionally, the powder shedding rate of the electrode sheet can be tested using the cross-cut test method, which includes the following steps: 10 × 10 grids are cut on the electrode sheet, tape is applied tightly to the grids for 30s to 120s and then peeled off, the powder shedding is observed, and the powder shedding rate of the electrode sheet is calculated based on the number of grids from which the electrode powder falls off.

[0066] Optionally, a 10×10 grid is formed on the electrode sheet by scribing, including the following steps: using a cutting tool to scribing 11 parallel horizontal lines and 11 parallel vertical lines on the electrode sheet to form a 10×10 square grid. The cutting edge size of the cutting tool is 10mm~30mm, the scribing speed is 20mm / s~50mm / s, and the side length of each grid is 1mm~3mm.

[0067] Optionally, 3M tape is used. After applying the tape tightly to the grid for 30s to 120s, the tape is peeled off at the smallest angle using a constant external force, and the amount of powder falling off each grid is observed using a magnifying glass.

[0068] Optionally, let a be the number of grids from which the electrode powder falls off, and let η be the powder shedding rate of the electrode sheet. The powder shedding rate of the electrode sheet is calculated according to the following formula: η = a / 100 × 100%.

[0069] Optionally, the powder shedding rate η of the electrode is ≥40%, for example 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95% and 100%, and further optionally 45%~95%.

[0070] Alternatively, the grinding process may include a kneading grinding method, using a kneading grinder.

[0071] Traditional dry powder stripping typically employs hammer crushing for physical crushing, requiring two to three crushing stages to improve the stripping rate of the electrode powder. However, this method results in a low stripping rate and easily damages the current collector, leading to high impurity content in the electrode powder due to debris from the current collector. Furthermore, the impurity content increases with each subsequent crushing stage. Because of the high impurity content in the electrode powder, direct regeneration and recycling are impossible; it can only be achieved through wet processing to convert it into lithium salts or other metal salts, resulting in a long recycling process and low economic efficiency. For example, when using aluminum foil as the current collector, after one hammer crushing stage, the stripping rate is approximately 50%, which is low. Moreover, the Al content in the electrode powder reaches 2500 ppm, which is too high for direct regeneration and recycling. It can only be achieved through wet processing to convert it into lithium salts or other metal salts, resulting in a long recycling process and low economic efficiency.

[0072] Compared to hammer milling, kneading milling achieves a higher single-pass peeling rate, generally exceeding 90%. However, the proportion of low-Al content powder is significantly affected by the type of electrode, resulting in substantial yield variations. To increase the proportion of low-Al content powder, the elastic modulus method and cross-cut adhesion method are used to select easily peelable electrodes, thereby improving the yield of directly recyclable powder. Therefore, this application can improve the peeling rate of electrode powder in electrode sheets and effectively reduce the impurity content of the electrode powder. The electrode powder obtained from milling can be directly recycled after simple sieving, thus offering advantages such as a short recycling process and high economic benefits.

[0073] Understandably, the peeling rate of the electrode powder in the electrode sheet refers to the ratio of the mass m1 of the electrode powder obtained by grinding to the total mass m of the electrode powder layer. Optionally, the peeling rate of the electrode powder in the electrode sheet is not less than 95%, such as 95%, 96%, 97%, 98%, 99% and 100%, and further optionally 98%~99%.

[0074] Optionally, after the powdering process, the following steps are also included: sieving the powder using a 100-500 mesh sieve.

[0075] Optionally, the screening process can be performed once or multiple times; the mesh size of the screen can be 100 mesh, 150 mesh, 200 mesh, 250 mesh, 300 mesh, 350 mesh, 400 mesh, and 500 mesh.

[0076] Optionally, the sieving process includes the following steps: performing a first sieving process on the powder using a 100-mesh sieve to obtain a first powder; performing a second sieving process on the first powder using a 300-mesh sieve to obtain a second powder; and performing a third sieving process on the second powder using a 500-mesh sieve to obtain a third powder.

[0077] Understandably, a 300-mesh sieve has a mesh diameter of approximately 75 μm, and the median particle size (D50) of the electrode powder is below 20 μm. However, the particle size of the current collector's debris is typically much larger than 75 μm. Therefore, after sieving through a 300-mesh sieve, the impurity content in the second powder is extremely low, allowing for direct regeneration and repair. This results in a short recycling process and high economic benefits. In some specific embodiments, the current collector is aluminum foil, and the Al content of the second powder is <300 ppm, referred to as low-Al content electrode powder.

[0078] Optionally, the mass percentage of the electrode powder passing through a 300-mesh sieve in the electrode powder layer of the electrode sheet is not less than 60%, for example, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, 100%, and further optionally 65%~80%.

[0079] The following detailed description, along with specific embodiments and comparative examples, further illustrates the process. Unless otherwise specified, all raw materials and instruments used in these embodiments and comparative examples are commercially available. Unless otherwise specified, all processes involved are conventionally chosen by those skilled in the art. Specifically, the waste gas electrode sheet is a commercially available positive electrode sheet from a lithium battery, the current collector is aluminum foil, and the positive electrode active material in the electrode powder layer is either a ternary positive electrode material or a lithium iron phosphate positive electrode material.

[0080] Example 1

[0081] The electrode in this embodiment satisfies the following condition: elastic modulus ε≤250N / cm 2 And the powder loss rate is ≥40%.

[0082] (1) Cut the electrode into a square with a side length L of 5cm and record the thickness T of the electrode and the thickness x of the electrode powder layer; apply an external force F to the electrode to bend it into a U-shape and record the bending diameter D of the electrode; calculate the elastic modulus ε of the electrode according to the torque balance, and the results are shown in Table 1.

[0083] (2) Using a blade with an 11mm kerf, at a scribing speed of 20mm / s, scribble 11 parallel horizontal lines spaced 1mm apart and 11 parallel vertical lines spaced 1mm apart on the electrode sheet to form a grid of 10 × 10 squares with a side length of 1mm. Apply tape to all grids, leave it for about 1 minute, and then peel it off at the smallest angle. Then observe the powder shedding in the grid with a magnifying glass. The test results of the grid method are shown in the figure below. Figure 2 As shown in Table 1, the number of grids where the electrode powder detached, a, was recorded, and the powder detachment rate η of the electrode sheet was calculated.

[0084] (3) The electrode sheets were pulverized once using a kneading pulverizing method to obtain electrode powder; the electrode powder was first sieved using a 100-mesh sieve to obtain the first powder; the electrode powder was second sieved using a 300-mesh sieve to obtain the second powder; the mass of the electrode powder layer was recorded as m, the mass of the electrode powder m1 and the mass of the second powder m2 were weighed, and the peeling rate of the electrode powder (m1 / m) and the mass ratio of the second powder (m2 / m) were calculated. The results are shown in Table 1.

[0085] Example 2

[0086] The electrodes in Example 2 all satisfy the following condition: elastic modulus ε≤250N / cm 2 With a powder shedding rate ≥40%, the only difference between this example and Example 1 lies in the relevant parameters of the electrode sheet, as detailed in Table 1. The test results of the cross-cut adhesion test are shown in the figure below. Figure 3 As shown.

[0087] Example 3

[0088] The electrodes in Example 3 all satisfy the following condition: elastic modulus ε≤250N / cm 2 With a powder shedding rate of ≥40%, the only difference between it and Example 1 is the relevant parameters of the electrode sheet, as detailed in Table 1.

[0089] Comparative Example 1

[0090] The electrodes in Comparative Example 1 all satisfy the following condition: elastic modulus ε > 250 N / cm 2 With a powder shedding rate of <40%, the relevant parameters of the electrode are detailed in Table 1, and the test results of the cross-cut adhesion test are shown in the figure below. Figure 4 As shown.

[0091] Comparative Example 2

[0092] The electrodes in Comparative Example 2 all satisfy the following condition: elastic modulus ε > 250 N / cm 2 With a powder loss rate of <40%, the relevant parameters of the electrode are detailed in Table 1.

[0093] Comparative Example 3

[0094] The electrodes in Comparative Example 3 all satisfy the following condition: elastic modulus ε≤250N / cm 2 With a powder loss rate of <40%, the relevant parameters of the electrode are detailed in Table 1.

[0095] Comparative Example 4

[0096] The electrodes in Comparative Example 4 all satisfy the following condition: elastic modulus ε > 250 N / cm 2 With a powder shedding rate ≥40%, the relevant parameters of the electrode are detailed in Table 1.

[0097] Analysis example

[0098] As shown in Table 1, the elastic modulus ε of the electrode in Example 1 is 231.7 N / cm. 2 ,Depend on Figure 2 It can be seen that the powder loss rate is ~45%. After one kneading and pulverizing process, the peeling rate reached 98%, and the mass ratio of the second powder (i.e., low-Al content electrode powder) reached 65%. The elastic modulus ε of the electrode in Example 2 is 193.1 N / cm. 2 ,Depend on Figure 3 It can be seen that its powder loss rate is ~95%, the peeling rate after powdering reaches 99%, and the mass ratio of the second powder reaches 70%. The elastic modulus ε of the electrode in Example 3 is 222.1 N / cm. 2 The powder loss rate is ~50%, the peeling rate after grinding reaches 95%, and the mass ratio of the second powder reaches 80%.

[0099] It is evident that by sorting using the elastic modulus method and the cross-cutting method, electrode sheets that are easy to peel off can be screened out. Electrode powder produced by kneading and grinding has a high peeling rate and low impurity content, and can be directly recycled. Therefore, it has the advantages of a short recycling process and high economic benefits.

[0100] The elastic modulus ε of Comparative Example 1 is 521.4 N / cm. 2 ,Depend on Figure 4 It can be seen that the electrode powder on the surface of this electrode did not fall off significantly in the cross-cut adhesion test. After one kneading and pulverizing process, the peeling rate was 90%, and the mass percentage of the second powder was only 50%. Similarly, the electrode of Comparative Example 2 did not meet the requirements for elastic modulus and powder loss rate. The peeling rate after pulverization was 92%, but the mass percentage of the second powder was only 55%. The elastic modulus of Comparative Example 3 met the requirement of <250 N / cm. 2 The requirement is met, but the powder shedding rate is <40%. Comparative Example 4 meets the requirement of a powder shedding rate >40%, but its elastic modulus is >250 N / cm². 2 The final peeling rate and the mass ratio of the second powder were both relatively low. This indicates that, under conditions not meeting the preset sorting requirements, the electrode sheet peeling rate was low and the impurity content was also high.

[0101] Table 1. Comparison of relevant parameters and recovery results of the electrode sheets

[0102]

[0103] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0104] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of protection of this application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these modifications and improvements all fall within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the appended claims.

Claims

1. A method of recycling an electrode tab, characterized by, The method comprises the following steps: The elastic modulus of the electrode tab is tested, and the powder drop rate of the electrode tab is tested by using the crosshatch method. Those with an elastic modulus not exceeding 250 N / cm were sorted out. 2 Electrode sheets with a powder loss rate exceeding 40% are then ground into powder to prepare electrode powder.

2. The recycling method of the pole piece according to claim 1, characterized by, The elastic modulus of the electrode tab is tested, and the powder drop rate of the electrode tab is tested by using the crosshatch method. The elastic modulus of the electrode tab is tested, and the powder drop rate of the electrode tab is tested by using the crosshatch method.

3. The recycling method of the pole piece according to claim 2, characterized by, The elastic modulus of the electrode tab is tested, and the powder drop rate of the electrode tab is tested by using the crosshatch method. 。 4. The recovery method of the pole piece according to claim 3, characterized by, The elastic modulus of the electrode tab is tested, and the powder drop rate of the electrode tab is tested by using the crosshatch method. The elastic modulus of the electrode tab is tested, and the powder drop rate of the electrode tab is tested by using the crosshatch method. The elastic modulus of the electrode tab is tested, and the powder drop rate of the electrode tab is tested by using the crosshatch method. The elastic modulus of the electrode tab is tested, and the powder drop rate of the electrode tab is tested by using the crosshatch method. The elastic modulus of the electrode tab is tested, and the powder drop rate of the electrode tab is tested by using the crosshatch method. The elastic modulus of the electrode tab is tested, and the powder drop rate of the electrode tab is tested by using the crosshatch method. (6) the elastic modulus ε of the pole piece is 100 N / cm 2 240 N / cm 2 .

5. The recovery method of the pole piece according to any one of claims 1 to 4, characterized by, The elastic modulus of the electrode tab is tested, and the powder drop rate of the electrode tab is tested by using the crosshatch method. The elastic modulus of the electrode tab is tested, and the powder drop rate of the electrode tab is tested by using the crosshatch method.

6. The recycling method of the pole piece according to claim 5, wherein The elastic modulus of the electrode tab is tested, and the powder drop rate of the electrode tab is tested by using the crosshatch method.

7. The method of recovering a pole piece according to any one of claims 1 to 4, wherein The elastic modulus of the electrode tab is tested, and the powder drop rate of the electrode tab is tested by using the crosshatch method.

8. The recycling method of the pole piece according to claim 7, characterized by, The elastic modulus of the electrode tab is tested, and the powder drop rate of the electrode tab is tested by using the crosshatch method.

9. The recovery method of the pole piece according to claim 7, characterized by, The elastic modulus of the electrode tab is tested, and the powder drop rate of the electrode tab is tested by using the crosshatch method. The elastic modulus of the electrode tab is tested, and the powder drop rate of the electrode tab is tested by using the crosshatch method.

10. The recycling method of the pole piece according to claim 9, characterized by, The elastic modulus of the electrode tab is tested, and the powder drop rate of the electrode tab is tested by using the crosshatch method. The elastic modulus of the electrode tab is tested, and the powder drop rate of the electrode tab is tested by using the crosshatch method. The elastic modulus of the electrode tab is tested, and the powder drop rate of the electrode tab is tested by using the crosshatch method. The elastic modulus of the electrode tab is tested, and the powder drop rate of the electrode tab is tested by using the crosshatch method. The elastic modulus of the electrode tab is tested, and the powder drop rate of the electrode tab is tested by using the crosshatch method. The elastic modulus of the electrode tab is tested, and the powder drop rate of the electrode tab is tested by using the crosshatch method. The elastic modulus of the electrode tab is tested, and the powder drop rate of the electrode tab is tested by using the crosshatch method. The elastic modulus of the electrode tab is tested, and the powder drop rate of the electrode tab is tested by using the crosshatch method. The elastic modulus of the electrode tab is tested, and the powder drop rate of the electrode tab is tested by using the crosshatch method. The elastic modulus of the electrode tab is tested, and the powder drop rate of the electrode tab is tested by using the crosshatch method. The elastic modulus of the electrode tab is tested, and the powder drop rate of the electrode tab is tested by using the crosshatch method. The elastic modulus of the electrode tab is tested, and the powder drop rate of the electrode tab is tested by using the crosshatch method. The elastic modulus of the electrode tab is tested, and the powder drop rate of the electrode tab is tested by using the crosshatch method. The elastic modulus of the electrode tab is tested, and the powder drop rate of the electrode tab is tested by using the crosshatch method. The elastic modulus of the electrode tab is tested, and the powder drop rate of the electrode tab is tested by using the crosshatch method. The elastic modulus of the electrode tab is tested, and the powder drop rate of the electrode tab is tested by using the crosshatch method. The elastic modulus of

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