Recycling method of positive plate, recycled positive electrode material and battery

Abstract

The invention relates to a recovery method of a positive plate, a recovered positive electrode material and a battery. The recovery method of the positive plate comprises the following steps: soaking a first positive plate in an aqueous solution, dissolving an aqueous binder and separating a positive active layer from a positive current collector to obtain a first positive material; sintering the second positive plate in a protective atmosphere at 300-600 DEG C for 0.5-3 hours to separate the positive active layer from the positive current collector to obtain a second positive material; crushing and separating the third positive plate to obtain a third positive material; mixing the first positive electrode material, the second positive electrode material and the third positive electrode material according to a mass ratio of (4-8): (1-5): 1 to obtain a mixture; and sintering the mixture in a protective atmosphere to obtain the recycled positive electrode material. According to the recycling method, recycling is carried out through a direct repairing process, and the recycled positive electrode material is relatively good in discharge capacity and cycle performance.

Description

Technical Field

[0001] This application relates to the field of electrode material recycling, and in particular to methods for recycling positive electrode sheets, recycling positive electrode materials, and batteries. Background Technology

[0002] With the rapid development of the battery industry, the recycling of retired and scrapped cathode materials has become an industry with both environmental value and commercial prospects. Currently, hydrometallurgical processes are commonly used recycling technologies, but they rely on strong acids and alkalis, generate large amounts of waste liquid, and suffer from severe environmental pollution and poor economic viability. This is especially true for scrapped lithium iron phosphate cathode sheets and batteries, where the economic value of hydrometallurgical recycling is even more limited due to the limited content of their high-value components. In recent years, a novel direct repair process has emerged for the recycling of scrapped cathode sheets and batteries. This process avoids the strong acid and alkali dissolution process of traditional hydrometallurgy and has received widespread attention and importance within the industry.

[0003] However, current direct repair methods still have limitations, such as a narrow applicability of the positive electrode and the need to improve the discharge capacity and cycle performance of the recovered positive electrode material. Summary of the Invention

[0004] Based on this, some embodiments of this application provide a method for recycling positive electrode sheets, which enables the positive electrode sheets to be recycled and reused through a direct repair process, and the discharge capacity and cycle performance of the recycled positive electrode material are good.

[0005] In addition, some other embodiments of this application also provide a recyclable cathode material and a battery.

[0006] A method for recycling a positive electrode sheet includes the following steps:

[0007] The first positive electrode sheet is immersed in an aqueous solution to dissolve the aqueous binder and separate the positive electrode active layer and the positive electrode current collector to obtain the first positive electrode material.

[0008] The second positive electrode sheet is sintered in a protective atmosphere at 300℃~600℃ for 0.5h~3h to separate the positive electrode active layer and the positive electrode current collector, thereby obtaining the second positive electrode material;

[0009] The third positive electrode sheet is crushed and separated to obtain the third positive electrode material;

[0010] The first positive electrode material, the second positive electrode material and the third positive electrode material are mixed in a mass ratio of (4~8):(1~5):1 to obtain a mixture;

[0011] The mixture is sintered under a protective atmosphere at a temperature of 400℃ to 800℃ for 3 to 15 hours to obtain recycled cathode material.

[0012] In some embodiments, the positive current collector comprises aluminum foil, and the mass percentage of aluminum in the first positive electrode material, the second positive electrode material and the third positive electrode material is 10ppm~100ppm, 300ppm~800ppm and 1000ppm~3000ppm, respectively.

[0013] In some embodiments, the first positive electrode, the second positive electrode, and the third positive electrode are obtained through the following steps:

[0014] A portion of the positive electrode sheets to be recycled is immersed in an aqueous solution for a preset time. After immersion, the positive electrode current collector is removed, the remaining solid is recovered, dried, and weighed. If the percentage of the remaining solid mass to the mass of the positive electrode sheets to be recycled is greater than or equal to a preset value, the positive electrode sheets to be recycled are designated as the first positive electrode sheet. If the percentage of the remaining solid mass to the mass of the positive electrode sheets to be recycled is less than the preset value, another portion of the positive electrode sheets to be recycled is sintered in a protective atmosphere at 300℃~600℃ for 0.5h~3h. After sintering, the positive electrode current collector is removed, the remaining solid is recovered, and if the percentage of the remaining solid mass to the mass of the positive electrode sheets to be recycled is greater than or equal to a preset value, the positive electrode sheets to be recycled are designated as the second positive electrode sheet. If the percentage of the remaining solid mass to the mass of the positive electrode sheets to be recycled is less than the preset value, the positive electrode sheets to be recycled are designated as the third positive electrode sheet. Optionally, the preset value is 85%~91%.

[0015] In some embodiments, the first positive electrode material, the second positive electrode material, and the third positive electrode material are mixed in a mass ratio of (5~8):(2~3):1.

[0016] In some embodiments, the positive electrode is a liquid-filled electrode. After the step of mixing the first positive electrode material, the second positive electrode material and the third positive electrode material in a mass ratio of (4~8):(1~5):1, and before the step of sintering the mixture, a lithium supplement is added.

[0017] In some embodiments, the amount of lithium supplement added is obtained through the following steps:

[0018] Take a portion of the mixture of the first cathode material, the second cathode material, and the third cathode material, and test the Li element content and the metal element content, wherein the metal element includes one or more of Fe, Co, Ni, and Mn;

[0019] The amount of lithium supplement agent to be added is determined based on the Li element content and the metal element content.

[0020] In some embodiments, the positive electrode is a liquid-filled electrode, and in the step of sintering the mixture under a protective atmosphere, the sintering temperature is 600℃~800℃, and the sintering time is 7h~15h; or,

[0021] All positive electrode sheets are unfilled with liquid. In the step of sintering the mixture under a protective atmosphere, the sintering temperature is 400℃~600℃ and the sintering time is 3h~10h.

[0022] In some embodiments, after the step of sintering the mixture under a protective atmosphere, a crushing step is further included to reduce the particle size D of the crushed material. v50 ≤1.5μm.

[0023] In some embodiments, the particle size D of the first cathode material, the second cathode material, and the third cathode material is... v50 Each independently ≤5μm; and / or,

[0024] The aqueous solution includes one or more of water and acidic aqueous solutions; optionally, the acidic aqueous solution includes one or both of citric acid solution and phosphoric acid solution; and / or,

[0025] In the step of crushing and separating the third positive electrode sheet, separation is carried out based on the density difference of the crushed material.

[0026] A method for recycling positive electrode material, obtained through the above-described method for recycling positive electrode sheets.

[0027] A battery comprising the aforementioned recycled cathode material.

[0028] The method for recycling positive electrode sheets according to some embodiments of this application involves using different separation methods for the first, second, and third positive electrode sheets. In the first separation process, the first positive electrode sheet is immersed in an aqueous solution to dissolve the aqueous binder and separate the positive electrode current collector and the positive electrode active layer. The first positive electrode material obtained by this separation process has a low impurity content, such as Al content, but does not remove the oily binder, such as PVDF. In the second separation process, the second positive electrode sheet is subjected to short-time high-temperature sintering treatment to deactivate the oily binder, such as PVDF, and separate the positive electrode active layer and the positive electrode current collector. The second positive electrode material obtained by this process has a low oily binder content and a slightly higher impurity content, such as Al content, than the first positive electrode material. The third separation process involves crushing and separating the third positive electrode sheet. This method is simple, low-cost, and applicable to all positive electrode sheets. However, it results in a significantly higher impurity content, such as Al content, leading to poor electrical performance when directly used for recovering the positive electrode material. Therefore, current methods for recovering third positive electrode materials mostly employ traditional hydrometallurgical processes (such as acid dissolution and alkali dissolution) to recover individual elements separately, making direct regeneration methods difficult. In some embodiments of this application, the third positive electrode material is mixed with two other positive electrode materials obtained through other separation processes in a certain proportion. This results in a significantly lower impurity content, such as Al, in the mixed material compared to the third positive electrode material, and an appropriate content of oil-soluble binder, such as PVDF, which is beneficial for improving its discharge capacity and cycle performance.

[0029] Therefore, the cathode recycling method of some embodiments of this application mixes and sinters the cathodes after processing them with different separation methods, so that the cathodes can be recycled and reused through direct repair process, and the discharge capacity and cycle performance of the recycled cathode material are good. Attached Figure Description

[0030] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying 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.

[0031] Figure 1 This is a schematic diagram of a process flow for recycling positive electrode sheets according to some embodiments of this application. Detailed Implementation

[0032] To facilitate understanding of this application, a more comprehensive description of the application will be provided below in conjunction with specific embodiments. Preferred embodiments of the application are given in the 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.

[0033] 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 in the specification of this application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0034] Unless otherwise stated or in case of conflict, the terms or phrases used in this application shall have the following meanings:

[0035] In this application, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined with "first" and "second" may explicitly or implicitly include at least one of those features.

[0036] In the description of this application, "multiple" means at least two, such as two, three, etc., unless otherwise expressly and specifically limited.

[0037] In this application, "one or more" refers to any one, two, or more of the listed items. "Multiple" refers to any two or more of the listed items.

[0038] Unless otherwise specified, all percentage concentrations mentioned in this application refer to the final concentration. The final concentration refers to the proportion of the added component in the system after the addition of that component.

[0039] In this application, terms such as "further," "even more," "particularly," "for example," "like," "example," and "exemplary" are used for descriptive purposes to indicate a connection in the coverage of different technical solutions presented earlier and later, but should not be construed as limiting the preceding technical solution or restricting the scope of protection herein. Unless otherwise specified herein, A (e.g., B) indicates that B is a non-limiting example of A, and it can be understood that A is not limited to B.

[0040] In this application, "optionally," "optionally," and "optional" mean that something is optional, that is, it is selected from either "present" or "absent." If multiple "options" appear in a technical solution, unless otherwise specified and there are no contradictions or mutual constraints, each "option" is independent. In this application, descriptions such as "optionally contains" and "optionally includes" indicate "contains or does not contain." "Optional component X" indicates whether component X exists or does not exist, or whether component X is contained or not.

[0041] 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.

[0042] In this application, the technical features described in an open-ended manner include both closed technical solutions consisting of the listed features and open technical solutions that include the listed features.

[0043] The terms "comprising" and "having," and any variations thereof, used in the embodiments of this application, are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or device that includes a series of steps or units is not limited to the steps or units listed, but may optionally include steps or units not listed, or may optionally include other steps or components inherent to such processes, methods, products, or devices.

[0044] In this application, the reference to "embodiment" means that a specific feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a mutually exclusive, independent, or alternative embodiment. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described in this application can be combined with other embodiments.

[0045] In the flowchart of this application, although the steps are shown sequentially according to the arrows, these steps are not necessarily performed in the order indicated by the arrows. Unless otherwise specified herein, there is no strict order restriction on the execution of these steps. They can be executed in other orders. Moreover, at least some of the steps in the diagram may include multiple sub-steps or multiple stages. These sub-steps or stages are not necessarily completed at the same time, but can be executed at different times. Their execution order is not necessarily sequential, but can be performed alternately or in turn with at least some of other steps or other sub-steps or stages.

[0046] Direct regeneration is a recycling technology that uses a series of physical or chemical methods to directly repair spent cathode materials, restoring their electrochemical performance. It differs fundamentally from mainstream hydrometallurgy (which completely dissolves and then purifies the material): direct regeneration aims to repair the structure, rather than completely decompose it. Compared to traditional hydrometallurgical techniques, it is less polluting, lower in cost, and simpler in process. However, current direct regeneration methods still have limitations, including applicability only to the recycling of certain specific cathode sheets, and the need to improve discharge capacity and cycle performance.

[0047] Based on this, the first aspect of this application provides a method for recycling a positive electrode sheet; please refer to [link to relevant documentation]. Figure 1 It includes the following steps:

[0048] Step S110: Immerse the first positive electrode sheet in an aqueous solution to dissolve the aqueous binder and separate the positive electrode active layer and the positive electrode current collector to obtain the first positive electrode material;

[0049] Step S120: Sinter the second positive electrode sheet in a protective atmosphere at 300℃~600℃ for 0.5h~3h to separate the positive electrode active layer and the positive electrode current collector, thereby obtaining the second positive electrode material;

[0050] Step S130: The third positive electrode sheet is crushed and separated to obtain the third positive electrode material;

[0051] Step S140: Mix the first cathode material, the second cathode material and the third cathode material in a mass ratio of (4~8):(1~5):1 to obtain a mixture;

[0052] Step S150: Under a protective atmosphere, the mixture is sintered at a temperature of 400℃~800℃ for 3h~15h to obtain the recycled cathode material.

[0053] The method of crushing and separating the third cathode sheet to obtain the third cathode material is simple and low-cost, but the impurity content, such as Al content, is significantly high. Direct use in recycling cathode materials results in poor electrical performance. Therefore, most current methods for obtaining the third cathode material employ traditional hydrometallurgical processes (such as acid dissolution and alkali dissolution) to recover individual elements separately, making direct regeneration methods difficult. In some embodiments of this application, the third cathode material is mixed with two cathode materials obtained through other separation processes in a certain proportion. This results in a significantly lower impurity content, such as Al content, in the mixed material compared to the third cathode material, and an appropriate content of oil-soluble binder, such as PVDF, which is beneficial for improving its discharge capacity and cycle performance.

[0054] Specifically, the first cathode material has a low Al content, but it does not remove oily binders such as PVDF. The second cathode sheet removes at least part of the PVDF binder through sintering, but the Al content of the second cathode material is relatively higher than that of the first cathode material. If only the first cathode material and the third cathode material are mixed, the Al content can be reduced, but the binder content is high, which is not conducive to improving the discharge capacity and cycle performance. If only the second cathode material and the third cathode material are mixed, it is difficult to effectively reduce the Al content, and the discharge capacity and cycle performance are difficult to meet the application requirements.

[0055] Therefore, the cathode recycling method in some embodiments of this application, by mixing and sintering the cathode after processing it with different separation methods, is beneficial to reduce impurity content, improve discharge capacity and cycle performance compared to the third cathode material. This also allows the cathode material that has been directly separated by pulverization to be recycled and reused by direct repair methods, thus expanding the recycling scope of cathodes.

[0056] In some embodiments, the positive electrode sheet is derived from waste positive electrode sheets generated during the lithium battery manufacturing process, and can be either a liquid-filled positive electrode sheet or an unfilled positive electrode sheet.

[0057] Unfilled electrode sheets refer to electrode sheets that have completed all processes such as coating, rolling, and slitting, but have not yet been assembled into the battery casing and have not been injected with electrolyte. Unfilled electrode sheets are usually scraps and defective materials generated during production. The materials have only undergone simple physical mixing, and the structure of the positive electrode material has not been damaged, resulting in a stable structure.

[0058] Electrode sheets with electrolyte filling refer to electrodes salvaged from used or scrapped finished batteries. These electrodes have undergone electrolyte immersion and complete charge-discharge cycles, resulting in complex electrochemical changes. The positive electrode material is oxidized under the influence of an electric field, releasing lithium ions and electrons. After the electrolyte filling is removed, the electrode sheet is structurally unstable and lacks lithium, making it unusable directly. It needs to be replenished with lithium and sintered before use.

[0059] Taking lithium iron phosphate (LiFePO4) as an example, the charge-discharge reaction is as follows:

[0060] Charging reaction (lithiation): LiFePO4 – xe - → xLi + + FePO4 + (1-x)LiFePO4;

[0061] Discharge reaction (lithium intercalation): FePO4 + xLi + + xe - → xLiFePO4 + (1-x)Fe.

[0062] Since the properties of liquid-filled and non-liquid-filled electrodes are different, in the actual processing, when the first positive electrode material, the second positive electrode material and the third positive electrode material are mixed in a mass ratio of (4~8):(1~5):1, the first positive electrode material, the second positive electrode material and the third positive electrode material are all obtained by non-liquid-filled electrode processing or by liquid-filled electrode processing.

[0063] In some embodiments, the length of the positive electrode sheet is 5cm to 30cm and the width is 5cm to 30cm. Specifically, the positive electrode sheet of the above dimensions can be obtained by disassembling and tearing up waste positive electrode sheets.

[0064] In some embodiments, the positive electrode sheet includes a positive current collector and a positive active layer. Specifically, the positive current collector includes, but is not limited to, aluminum foil. The positive active layer comprises a positive active material, a first conductive agent, and an oily binder. The positive active material includes, but is not limited to, lithium iron phosphate (LFP), nickel-cobalt-manganese ternary materials (NMC), nickel-cobalt-aluminum ternary materials (NCA), lithium cobalt oxide (LCO), etc. The first conductive agent includes, but is not limited to, conductive carbon black, such as Super P. Super P is a highly graphitized carbon black material with a special shape and structure that provides low resistance and high conductivity. It typically exhibits a spherical structure with micron-sized particles and a high specific surface area. Super P has a high degree of graphitization, its main component is carbon, and it contains almost no impurities, thus exhibiting excellent conductivity and chemical stability. The binder is an oil-soluble binder, such as PVDF, a highly non-reactive thermoplastic fluoropolymer. It can be synthesized by the polymerization of 1,1-difluoroethylene and is soluble in strong polar solvents such as dimethylacetamide. And a carbon coating layer disposed between the positive electrode current collector and the positive electrode active layer.

[0065] In some embodiments, the positive electrode sheet further includes a carbon coating layer disposed between the positive electrode current collector and the positive electrode active layer. The carbon coating layer is used to improve the adhesion between the positive electrode active layer and the positive electrode current collector, and to reduce the interfacial impedance of the positive electrode current collector. Specifically, the carbon coating layer includes a second conductive agent and an aqueous binder. The second conductive agent includes, but is not limited to, conductive carbon. The aqueous binder refers to a high molecular weight polymer with water solubility or water dispersibility, including, but not limited to, one or more of sodium carboxymethyl cellulose, polyacrylic acid, styrene-butadiene rubber, and polyvinyl alcohol.

[0066] In this application, different electrodes, such as electrodes recovered from different batches or from different sources, may have different compositions and require different separation methods. This application expands the scope of electrode recycling by separating different electrodes using different methods.

[0067] In some embodiments, the aqueous solution includes one or more of water and acidic solutions.

[0068] Optionally, the acidic solution includes one or both of citric acid solution and phosphoric acid solution. In one example, the concentration of the acidic solution is 0.1 mol / L to 1 mol / L.

[0069] In some embodiments, the temperature of the aqueous solution is 0°C to 100°C.

[0070] In some embodiments, after the step of mixing the first positive electrode sheet with an aqueous solution to dissolve the aqueous binder and separate the positive electrode active layer and the positive electrode current collector, the method further includes a step of drying the separated first positive electrode active layer. Specifically, the drying temperature is 100°C to 120°C, and the drying time is 2 hours to 10 hours.

[0071] In some embodiments, the particle size D of the first cathode material v50 ≤5μm. Optionally, the particle size D of the first cathode material... v50 The particle size is 0.5μm to 3μm. Using this particle size facilitates thorough mixing in subsequent processes. Specifically, the first cathode material can be crushed, and the parameters of the crushing device can be adjusted to ensure the particle size meets the above requirements. In one example, the crushing device can be, but is not limited to, an air jet mill or a pin mill.

[0072] In some embodiments, step S110 includes: mixing the first positive electrode sheet with an aqueous solution to dissolve the aqueous binder and separate the positive electrode active layer and the positive electrode current collector; drying and crushing the separated positive electrode active layer to obtain D. v50 The first cathode material with a thickness of ≤5μm.

[0073] In some embodiments, step S120 includes: sintering the positive electrode sheet in a protective atmosphere at 300°C to 600°C for 0.5 to 3 hours to separate the positive electrode active layer and the positive electrode current collector, thereby obtaining a second positive electrode material.

[0074] Short-duration, high-temperature sintering deactivates the binder in the material, allowing the positive electrode active layer and the positive electrode current collector to separate. If the sintering time is too long, the binder, such as PVDF, may react with the positive electrode current collector, such as aluminum foil, resulting in a significant decrease in the discharge capacity of the recycled positive electrode material. If the sintering temperature is too low, the binder, such as PVDF, may not deactivate, making it difficult to separate the positive electrode current collector from the positive electrode material.

[0075] In some embodiments, the flow rate of the protective gas is 1 L / min to 10 L / min.

[0076] In one example, the sintering step can be carried out in a sintering apparatus such as a box furnace or a roller kiln.

[0077] In some embodiments, the particle size D of the second cathode material v50≤5μm. Optionally, the particle size D of the second cathode material... v50 The particle size is 0.5μm to 3μm. Using this particle size facilitates thorough mixing in subsequent processes. Specifically, the second cathode material can be crushed, and the parameters of the crushing device can be adjusted to ensure the particle size meets the above requirements. In one example, the crushing device can be, but is not limited to, an air jet mill or a pin mill.

[0078] In some embodiments, step S120 includes: sintering the second positive electrode sheet at 300°C to 600°C for 0.5 h to 4 h under a protective atmosphere, with a protective gas flow rate of 1 L / min to 10 L / min, to separate the positive electrode active layer and the positive electrode current collector; and then crushing the separated positive electrode active layer to obtain D. v50 Second cathode material with a diameter of ≤5μm.

[0079] In some embodiments, step S130 includes: breaking and separating the third positive electrode sheet to obtain the third positive electrode material.

[0080] Specifically, the step of crushing the third positive electrode sheet can be carried out in an air jet mill or a pin mill.

[0081] Specifically, the particle size D of the third cathode material v50 ≤5μm. Optionally, the particle size D of the third cathode material... v50 ≤2.5μm. Optionally, the particle size D of the third cathode material... v50 The particle size should be between 1 μm and 2.5 μm. Using this particle size facilitates thorough mixing in subsequent processes. Specifically, the particle size can be adjusted to meet these requirements by adjusting the parameters of the pulverizing equipment.

[0082] Specifically, in the crushing and separation steps of the third positive electrode sheet, separation is performed based on the density differences of the crushed materials. In one example, a cyclone separator is used for separation. Specifically, the parameters of the cyclone separator include: processing air volume: 2000~50000 m³ / h. 3 / h, intake speed 16~24m / s.

[0083] The process of crushing and separating the third cathode sheet is simple and low-cost, and the cathode active layer and cathode current collector can be separated from all cathode sheets using this method. However, the cathode material obtained by this method has a high impurity content, such as Al content, and direct recycling for use in batteries results in unsatisfactory electrochemical performance. Traditional processes mostly employ conventional hydrometallurgical methods (such as acid dissolution and alkali dissolution) to recover individual elements separately, making direct regeneration methods difficult. In some embodiments of this application, the crushed and separated third cathode material is mixed and sintered with two other cathode materials obtained through other separation processes in a certain proportion. Compared to a single third cathode material, this reduces the impurity content and improves the discharge capacity and cycle performance.

[0084] In some embodiments, the positive current collector includes aluminum foil, and the mass percentage of aluminum in the first, second, and third positive electrode materials is 10 ppm to 100 ppm, 300 ppm to 800 ppm, and 1000 ppm to 3000 ppm, respectively. For example, the mass percentage of aluminum in the first positive electrode material may be, but is not limited to, 10 ppm, 20 ppm, 30 ppm, 40 ppm, 50 ppm, 60 ppm, 70 ppm, 80 ppm, 90 ppm, 100 ppm, or any combination of these values. The mass percentage of aluminum in the second positive electrode material may be, but is not limited to, 300 ppm, 400 ppm, 500 ppm, 600 ppm, 700 ppm, 800 ppm, or any combination of these values. The mass percentage of aluminum in the third cathode material may be, but is not limited to, 1000ppm, 1200ppm, 1500ppm, 1800ppm, 2000ppm, 2200ppm, 2500ppm, 2800ppm, 3000ppm, or any combination of these values.

[0085] In some embodiments, the first positive electrode, the second positive electrode, and the third positive electrode are different. Specifically, the first positive electrode, the second positive electrode, and the third positive electrode are derived from different sources.

[0086] In practice, when faced with multiple positive electrode plates from different sources, it is necessary to first determine whether each positive electrode plate is the first, second, or third positive electrode plate.

[0087] Specifically, the first positive electrode, the second positive electrode, and the third positive electrode are obtained through the following steps:

[0088] A portion of the positive electrode sheets to be recycled is immersed in an aqueous solution for a preset time. After immersion, the positive current collector is removed, the remaining solid is recovered, dried, and weighed. If the mass percentage of the remaining solid relative to the mass of the positive electrode sheets to be recycled is greater than or equal to a preset value, the positive electrode sheets to be recycled are designated as the first positive electrode sheet. If the mass percentage of the remaining solid relative to the mass of the positive electrode sheets to be recycled is less than the preset value, another portion of the positive electrode sheets to be recycled is sintered in a protective atmosphere at 300℃~600℃ for 0.5h~3h. After sintering, the positive current collector is removed, the remaining solid is recovered, and if the mass percentage of the remaining solid relative to the mass of the positive electrode sheets to be recycled is greater than or equal to a preset value, the positive electrode sheets to be recycled are designated as the second positive electrode sheet. If the mass percentage of the remaining solid relative to the mass of the positive electrode sheets to be recycled is less than the preset value, the positive electrode sheets to be recycled are designated as the third positive electrode sheet.

[0089] The preset time can be 10 to 15 minutes. The preset value can be determined based on the percentage of positive electrode material in the total mass of the untreated positive electrode sheet. In one example, the preset value is 85% to 91%.

[0090] Since the positive electrode current collector basically retains its original morphology, such as foil, after soaking and sintering, the remaining solid after separating it from the system is the positive electrode material separated from the positive electrode current collector. By comparing the percentage of the remaining solid to the original electrode sheet, if it is greater than or equal to the preset value, it indicates that the positive electrode material has been basically peeled off from the positive electrode current collector. If it is less than the preset value, it indicates that the peeling effect of the positive electrode material is not good, and it is difficult to use this method for separation.

[0091] The above steps determine the type of positive electrode sheet to be recycled. First, the positive electrode sheet is soaked. If the positive electrode sheet cannot be separated after soaking, for example, if it does not contain an aqueous binder, sintering is used for separation. In sintering, high-temperature, short-time sintering deactivates the binder, such as PVDF, thus separating the positive electrode material from the positive electrode current collector. However, in some electrode sheets, the PVDF content may be too high or the binder may be different, making it difficult to deactivate at the above temperature and time, thus hindering the separation of the positive electrode material from the positive electrode current collector. Therefore, a powdering separation method is used. This method is simple and can separate all positive electrode sheets. However, the positive electrode material obtained by this method has a high impurity content, and its electrochemical performance does not meet requirements when directly applied. Therefore, if the above two separation methods fail, a third separation process is used.

[0092] In some embodiments, the step of mixing the first cathode material, the second cathode material, and the third cathode material in a mass ratio of (4~8):(1~5):1 includes: using negative pressure to draw the first cathode material, the second cathode material, and the third cathode material into their respective buffer tanks, and then feeding them into a mixing bin via a feeding screw located below each buffer tank. Precise feeding is achieved through the feeding screw, with the feeding error controlled within ±0.5g, thus ensuring precise mixing of the cathode materials.

[0093] Specifically, the mass ratio of the first cathode material to the third cathode material can be, but is not limited to, 4:1, 5:1, 6:1, 7:1, 8:1, or any combination of these values. The mass ratio of the second cathode material to the third cathode material can be, but is not limited to, 1:1, 2:1, 3:1, 4:1, 5:1, or any combination of these values. Optionally, the first cathode material, the second cathode material, and the third cathode material are mixed in a mass ratio of (5~8):(2~3):1.

[0094] Specifically, the negative pressure intensity is -10kPa to -50kPa.

[0095] Specifically, in the mixing step, the rotation speed is 20 rpm / min to 40 rpm / min, and the time is 10 min to 60 min.

[0096] Specifically, the mixing step is carried out under a protective atmosphere. The protective atmosphere may be, but is not limited to, nitrogen, argon, etc.

[0097] In some embodiments, the positive electrode is a liquid-filled electrode. After mixing the first, second, and third positive electrode materials in a mass ratio of (4-8):(1-5):1, and before sintering the mixture, a lithium replenishing agent is added. The liquid-filled electrode undergoes electrolyte wetting and a complete charge-discharge cycle, resulting in complex electrochemical changes. The positive electrode material is oxidized under an electric field, releasing lithium ions and electrons. When the liquid-filled electrode is removed, its structure is unstable and lithium-deficient. The positive electrode material is then mixed with the lithium replenishing agent and subjected to prolonged high-temperature sintering. The high temperature provides energy for atomic rearrangement, repairing the disordered crystal structure and restoring it to an ordered layered or spinel structure.

[0098] Specifically, the amount of lithium supplement added is obtained through the following steps:

[0099] The content of Li and the content of metal elements were tested after a mixture of the first cathode material, the second cathode material and the third cathode material. The metal elements included one or more of Fe, Co, Ni and Mn.

[0100] The amount of lithium supplement agent to be added is determined based on the Li element content and the content of other metal elements.

[0101] Specifically, the Li and metal element content were tested using ICP (inductively coupled plasma spectroscopy). Both Li and metal element content refer to their mass percentage in the material.

[0102] Specifically, in the step of determining the amount of lithium supplementer to be added based on the Li element content and the metal element content, the molar ratio of lithium element to metal element after adding the lithium supplementer meets a preset value. For example, if the positive electrode is a lithium iron phosphate positive electrode, the preset value can be 1.05.

[0103] Specifically, lithium supplements include one or both of lithium carbonate (Li₂CO₃) and lithium hydroxide (LiOH). The amount of lithium supplement added refers to the mass of the lithium supplement added.

[0104] Specifically, the lithium replenishment agent is precisely fed through a feeding screw, with the feeding error controlled within ±0.05g.

[0105] Specifically, after adding the lithium supplement, continue mixing for 10 to 60 minutes under a protective atmosphere and at a rotation speed of 20 to 40 rpm.

[0106] In some embodiments, prior to the sintering step, the mixture is further further subjected to a process of loading it into saggers. This loading process allows for the handling of more material in a single sintering operation. Specifically, an automatic roller conveyor loading machine is used. The loading machine precisely controls the weight of each sagger, with an accuracy of ±0.5g / sagger. Each sagger is automatically and evenly shaken within the sagger using ultrasonic vibration. The sagger material is selected from materials such as graphite and cordierite. In one example, the saggers are 50-400mm long, 50-400mm wide, and 5-300mm high, with each sagger containing 3-5kg of material. Double-layer, two- to four-row stacking is possible, with flat-mouthed saggers on top and notched saggers on the bottom, automatically stacked using a gripper tool. It is understood that the above is only one specific loading process and is not limited to it.

[0107] In some embodiments, during the sintering step of the mixture, the sintering temperature is 400°C to 800°C, and the sintering time is 3 hours to 15 hours. Optionally, the sintering time is 3 hours to 10 hours, or 3 hours to 8 hours.

[0108] In some embodiments, the positive electrode is a liquid-filled electrode. In the step of sintering the mixture under a protective atmosphere, the sintering temperature is 600℃~800℃ and the sintering time is 7h~15h. Optionally, the sintering time is 7h~8h.

[0109] In other embodiments, the positive electrode is an unfilled electrode. In the step of sintering the mixture under a protective atmosphere, the sintering temperature is 400℃~600℃ and the sintering time is 3h~10h. Optionally, the sintering time is 3h~4h.

[0110] During the sintering process of liquid-filled electrodes, high temperatures provide energy for atomic rearrangement, repairing the disordered crystal structure and restoring it to an ordered layered or spinel-like structure. In contrast, the sintering process of non-liquid-filled electrodes mainly utilizes high temperatures to remove internal impurities from the material. Therefore, the sintering temperature and sintering time of liquid-filled electrodes are relatively higher.

[0111] In some embodiments, during the step of sintering the mixture, the flow rate of the protective gas is 1 L / min to 10 L / min.

[0112] In some embodiments, the step of sintering the mixture is carried out in a box furnace at a heating rate of 5°C / min to 10°C / min.

[0113] In some embodiments, after the step of sintering the mixture under a protective atmosphere, a crushing step is further included to reduce the particle size D of the crushed material. v50 ≤1.5μm. Optionally, the particle size D of the crushed material. v50 The particle size is 0.5μm to 1.5μm. Furthermore, the particle size D of the crushed material... max ≤15μm.

[0114] Specifically, an air jet mill is used for crushing, with the following equipment parameters: feeding frequency 10Hz~20Hz, grading frequency 100Hz~150Hz, and induced draft frequency 30Hz~50Hz.

[0115] The second aspect of this application provides a method for recycling positive electrode material, obtained by the method for recycling the positive electrode sheet described in the first aspect.

[0116] A third aspect of this application provides a battery comprising the recycled cathode material described in the second aspect above.

[0117] It's understandable that recycled positive electrode materials are used to make positive electrode sheets for use in batteries. Batteries also include negative electrode sheets, separators, and electrolytes. The electrolyte acts as a conductor of ions between the positive and negative electrode sheets. The separator, positioned between the positive and negative electrode sheets, prevents short circuits while allowing ions to pass through.

[0118] To make the objectives and advantages of this application clearer, the following detailed description of the positive electrode recovery method and its effects, in conjunction with specific embodiments, is provided. It should be understood that the specific embodiments described herein are merely illustrative and should not be construed as limiting the scope of this application. Unless otherwise specified, the following embodiments do not include components other than unavoidable impurities. Unless otherwise specified, the drugs and instruments used in the embodiments are conventionally chosen in the art. Experimental methods in the embodiments that do not specify specific conditions were implemented under conventional conditions, such as those described in literature, books, or methods recommended by the manufacturer.

[0119] Example 1

[0120] This embodiment provides a method for recycling a positive electrode sheet, including the following steps:

[0121] (1) The unfilled battery waste electrode sheets from multiple batches of recycling are split and shredded to obtain small positive electrode sheets; the length of the small positive electrode sheets is 5~30cm and the width is 5~30cm. A small amount of each of the multiple batches of small positive electrode sheets is taken and their type is determined according to the following steps. Take a portion of the small positive electrode sheets to be recycled and soak them in water for 10min. After soaking, remove the aluminum foil of the positive current collector, recover the remaining solid, dry and weigh it. If the mass of the remaining solid accounts for more than or equal to 85% of the mass of the positive electrode sheet to be recycled, the positive electrode sheet to be recycled is recorded as the first positive electrode sheet; otherwise, take another portion of the positive electrode sheets to be recycled and sinter them at 475℃ for 3h under a protective atmosphere with an inert gas flow rate of 7L / min. After sintering, remove the aluminum foil of the positive current collector and recover the remaining solid. If the mass of the remaining solid accounts for more than or equal to 85% of the mass of the positive electrode sheet to be recycled, the positive electrode sheet to be recycled is recorded as the second positive electrode sheet; otherwise, the positive electrode sheet to be recycled is recorded as the third positive electrode sheet.

[0122] (2) Soak the first positive electrode sheet after tearing it in step (1) in water to dissolve the water-based binder and separate the positive electrode layer from the aluminum foil. The water temperature is controlled at 30°C. The separated positive electrode active layer is dried at 100°C for 5 hours. After drying, it is drawn into an air jet mill for crushing to make the particle size D of the crushed first positive electrode material... v50 The diameter is 1.78 μm, and the Al content in the first cathode material is 25 ppm.

[0123] (3) Place the shredded second positive electrode sheet from step (1) into a box furnace and sinter it at 475°C for 3 hours under inert gas protection. The inert gas flow rate is 7 L / min. This separates the positive electrode active layer from the aluminum foil. The separated positive electrode active layer is then drawn into an air jet mill for crushing, reducing the particle size D of the crushed second positive electrode material. v50 The diameter is 1.02 μm, and the Al content in the second cathode material is 572 ppm.

[0124] (4) The third positive electrode sheet, which was shredded in step (1), is drawn into an air jet mill for crushing and grinding, so that the particle size D is reduced. v50 The particle size was 2μm. The powder was then separated by a cyclone separator with the following parameters: air inlet velocity 18m / s. The third cathode material was obtained with an Al content of 1250ppm.

[0125] (5) The first positive electrode material, the second positive electrode material, and the third positive electrode material are respectively sucked into their respective buffer tanks using negative pressure pumping. The negative pressure intensity is -10 kPa. Each buffer tank is equipped with a vertical feeding screw. After setting the feeding weight according to the mass ratio of the first positive electrode material, the second positive electrode material, and the third positive electrode material of 8:1:1, the feeding screw achieves precise feeding with a feeding error of ±0.5g. After feeding, the materials are mixed in an inert gas at a speed of 30 pm / min for 20 minutes to make the materials uniform and obtain a mixture.

[0126] (6) After mixing, the mixture is placed in saggers and pumped to the sintering buffer silo under negative pressure (-10 kPa). An automatic roller conveyor sagger is used for loading. The sagger is designed to precisely control the weight of each sagger (±0.5 g / sagger). Each sagger is automatically shaken and leveled within the sagger using ultrasonic vibration. The saggers are made of graphite and are 300 mm long, 300 mm wide, and 150 mm high. Each sagger contains 4 kg of material. The saggers are arranged in two to four rows in a double layer. The upper layer uses flat-mouthed saggers, and the lower layer uses notched saggers. The saggers are automatically stacked using a gripper tool with the parameters set as required.

[0127] (7) After the material is filled into a bowl, it is stacked in a box furnace and sintered for 4 hours under the conditions of an inert gas flow rate of 7L / min and a temperature of 460℃.

[0128] (8) The sintered material is fed into an air jet mill for crushing. The equipment parameters are: feeding frequency 15Hz, grading frequency 110Hz, and induced draft frequency 30Hz. The particle size D of the crushed material is... v50 It is 0.96μm, D max The thickness was 8.76 μm, and the recovered cathode material was obtained.

[0129] Example 2

[0130] This embodiment provides a method for recycling a positive electrode sheet, which is similar to the recycling method in Embodiment 1. The difference is that in step (5), the mixing ratio of the first positive electrode material, the second positive electrode material, and the third positive electrode material is different. In this embodiment, the first positive electrode material, the second positive electrode material, and the third positive electrode material are mixed in a mass ratio of 6:3:1.

[0131] Example 3

[0132] This embodiment provides a method for recycling a positive electrode sheet, which is similar to the recycling method in Embodiment 1. The difference is that in step (5), the mixing ratio of the first positive electrode material, the second positive electrode material, and the third positive electrode material is different. In this embodiment, the first positive electrode material, the second positive electrode material, and the third positive electrode material are mixed in a mass ratio of 4:5:1.

[0133] Example 4

[0134] This embodiment provides a method for recycling a positive electrode sheet, including the following steps:

[0135] (1) Disassemble and shred the recycled battery electrode sheets from multiple batches to obtain small positive electrode sheets; the small positive electrode sheets are 5-30cm long and 5-30cm wide. Take a small amount of each of the multiple batches of small positive electrode sheets and determine their type according to the following steps. Take a portion of the small positive electrode sheets to be recycled and immerse them in a 0.5 mol / L citric acid aqueous solution for 10 min. After immersion, remove the aluminum foil of the positive electrode current collector, recover the remaining solid, dry it, and weigh it. If the mass of the remaining solid accounts for more than or equal to 85% of the mass of the positive electrode sheets to be recycled, the positive electrode sheets to be recycled are recorded as the first positive electrode sheet; otherwise, take another portion of the positive electrode sheets to be recycled and sinter them at 400℃ for 2 h under a protective atmosphere with an inert gas flow rate of 7 L / min. After sintering, remove the aluminum foil of the positive electrode current collector, recover the remaining solid, and if the mass of the remaining solid accounts for more than or equal to 85% of the mass of the positive electrode sheets to be recycled, the positive electrode sheets to be recycled are recorded as the second positive electrode sheet; otherwise, the positive electrode sheets to be recycled are recorded as the third positive electrode sheet.

[0136] (2) The first positive electrode sheet after being torn up in step (1) is immersed in a 0.5 mol / L citric acid aqueous solution to dissolve the aqueous binder and separate the positive electrode active layer from the aluminum foil. The temperature of the citric acid aqueous solution is controlled at 35°C. The separated positive electrode active layer is dried at 100°C for 5 hours. After drying, it is drawn into an air jet mill for crushing to reduce the particle size D of the crushed first positive electrode material. v50 The diameter is 2.1 μm, and the Al content in the first cathode material is 65 ppm.

[0137] (3) Place the second positive electrode sheet shredded in step (1) into a box furnace and sinter it at 450°C for 2 hours under inert gas protection. The inert gas flow rate is 7 L / min. This separates the positive electrode active layer from the aluminum foil. The separated positive electrode active layer is then drawn into an air jet mill for crushing, so that the particle size D of the crushed second positive electrode material is reduced. v50 The diameter is 1.2 μm, and the Al content in the second cathode material is 450 ppm.

[0138] (4) The third positive electrode sheet, which was shredded in step (1), is drawn into an air jet mill for crushing and grinding, so that the particle size D is reduced. 50 The particle size was 1.78 μm. The powder was then separated by a cyclone separator with the following parameters: air inlet velocity 18 m / s. The resulting third cathode material had an Al content of 1828 ppm.

[0139] (5) Using negative pressure pumping, the first, second, and third cathode materials are respectively sucked into their respective buffer tanks. The negative pressure intensity is -10 kPa. Each buffer tank is equipped with a vertical feeding screw. After setting the feeding weight according to the mass ratio of the first, second, and third cathode materials as 8:1:1, the tail screw achieves precise feeding with a feeding error of ±0.5g. A portion of the mixed material is taken for ICP testing to determine the Li and Fe contents. The amount of lithium carbonate to be added is calculated based on the molar ratio of Li to Fe in LiFePO4 as 1.05:1. The tail screw of the high-precision lithium source material buffer tank achieves precise feeding. The feeding weight is set with a feeding error of ±0.05g. After lithium addition, the mixture can be continued in an inert gas at a speed of 30 rpm / min for 15 min to ensure uniform mixing and obtain a mixture.

[0140] (6) After mixing, the mixture is placed in saggers and pumped to the sintering buffer silo under negative pressure (-10 kPa). An automatic roller conveyor sagger is used for loading. The sagger is designed to precisely control the weight of each sagger (±0.5 g / sagger). Each sagger is automatically shaken and leveled within the sagger using ultrasonic vibration. The saggers are made of materials such as cordierite, and are 300 mm long, 300 mm wide, and 150 mm high, with each sagger containing 4 kg of material. The saggers are arranged in two to four rows in a double layer. The upper layer uses flat-mouthed saggers, and the lower layer uses notched saggers. The saggers are automatically stacked using a gripper tool with the parameters set as required.

[0141] (7) After the material is filled into a bowl, it is stacked in a box furnace and sintered for 8 hours under the conditions of an inert gas flow rate of 7L / min and a temperature of 750℃.

[0142] (8) The sintered material is fed into an air jet mill for crushing. The equipment parameters are: feeding frequency 10Hz, grading frequency 100Hz, and induced draft frequency 28Hz. The particle size D of the crushed material is... v50 It is 1.15μm, D max The thickness is 10 μm, and the recovered cathode material is obtained.

[0143] Example 5

[0144] This embodiment provides a method for recycling a positive electrode sheet, which is similar to the recycling method in Embodiment 4, except that the sintering temperature and time in step (5) are different. In step (5) of this embodiment, the sintering temperature is 770°C and the time is 10 hours.

[0145] Comparative Example 1

[0146] Comparative Example 1 provides a method for recycling a positive electrode sheet, which is similar to the recycling method in Example 1. The difference is that in step (5), the mixing ratio of the first positive electrode material, the second positive electrode material, and the third positive electrode material is different. In Comparative Example 1, they are mixed in a ratio of 1:1:1.

[0147] Comparative Example 2

[0148] Comparative Example 2 provides a method for recycling a positive electrode sheet, similar to the recycling method in Example 1, except that it does not include step (2), and step (5) is different. In Comparative Example 2, step (5) is as follows:

[0149] The second and third cathode materials are drawn into their respective buffer tanks using negative pressure pumping with a negative pressure intensity of -10 kPa. Each buffer tank is equipped with a vertical feeding screw. After setting the feeding weight according to the mass ratio of the second and third cathode materials as 1:1, the tail screw achieves precise feeding with a feeding error controlled within ±0.5g. After feeding, the materials are mixed in an inert gas at a speed of 30 rpm / min for 20 minutes to ensure uniform mixing and obtain a mixture.

[0150] Comparative Example 3

[0151] Comparative Example 3 provides a positive electrode recycling method, which is similar to the recycling method in Example 1, except that the sintering time in step (3) is different. In Comparative Example 3, the sintering time in step (3) is 5 hours.

[0152] The recycled cathode materials obtained in the above embodiments and comparative examples were assembled into batteries and tested. The experimental data are shown in Table 1 below. The recycled cathode materials were mixed with PVDF and conductive acetylene black at a mass percentage of 98%, 1.5%, and 0.5% to obtain the cathode sheet. Lithium-ion batteries were used as the anode sheet, and lithium hexafluorophosphate was used as the electrolyte. The battery performance testing method is as follows: At 25°C, the battery was charged at a constant current of 0.1C to the upper voltage limit of 3.75V for the first charge cycle to obtain the initial charge capacity. Then, at 25°C, the battery was discharged at a constant current of 0.1C to the lower voltage limit of 2.5V for the first discharge cycle to obtain the initial discharge capacity. Then, the battery was cycled at a constant current of 1C. The ratio of the discharge capacity after 100 cycles to the initial discharge capacity at 1C was recorded as the capacity retention rate.

[0153] Table 1

[0154]

[0155] As can be seen from Table 1 above, the embodiments of this application, by mixing the third cathode material with two cathode materials obtained by other separation processes in a certain proportion, are beneficial to improving its discharge capacity and cycle performance.

[0156] 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.

[0157] The embodiments described above are merely illustrative of several implementation methods of this application, intended to facilitate a detailed understanding of the technical solutions of this application, but should not be construed as limiting the scope of protection of the invention patent. 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 all fall within the scope of protection of this application. It should be understood that technical solutions obtained by those skilled in the art based on the technical solutions provided in this application through logical analysis, reasoning, or limited experimentation are all within the scope of protection of the appended claims. Therefore, the scope of protection of this patent application should be determined by the content of the appended claims, and the specification and drawings can be used to interpret the content of the claims.

Claims

1. A method for recycling a positive electrode sheet, characterized in that, Includes the following steps: The first positive electrode sheet is immersed in an aqueous solution to dissolve the aqueous binder and separate the positive electrode active layer and the positive electrode current collector to obtain the first positive electrode material. The second positive electrode sheet is sintered in a protective atmosphere at 300℃~600℃ for 0.5h~3h to separate the positive electrode active layer and the positive electrode current collector, thereby obtaining the second positive electrode material; The third positive electrode sheet is crushed and separated to obtain the third positive electrode material; The first positive electrode material, the second positive electrode material and the third positive electrode material are mixed in a mass ratio of (4~8):(1~5):1 to obtain a mixture; The mixture is sintered under a protective atmosphere at a temperature of 400℃ to 800℃ for 3 to 15 hours to obtain recycled cathode material.

2. The method for recycling the positive electrode sheet according to claim 1, characterized in that, The positive electrode current collector includes aluminum foil, and the mass percentages of aluminum in the first positive electrode material, the second positive electrode material, and the third positive electrode material are 10ppm~100ppm, 300ppm~800ppm, and 1000ppm~3000ppm, respectively; and / or, The first positive electrode, the second positive electrode, and the third positive electrode are obtained through the following steps: A portion of the positive electrode sheets to be recycled is immersed in an aqueous solution for a preset time. After immersion, the positive electrode current collector is removed, the remaining solid is recovered, dried, and weighed. If the percentage of the remaining solid mass to the mass of the positive electrode sheets to be recycled is greater than or equal to a preset value, the positive electrode sheets to be recycled are designated as the first positive electrode sheet. If the percentage of the remaining solid mass to the mass of the positive electrode sheets to be recycled is less than the preset value, another portion of the positive electrode sheets to be recycled is sintered in a protective atmosphere at 300℃~600℃ for 0.5h~3h. After sintering, the positive electrode current collector is removed, the remaining solid is recovered, and if the percentage of the remaining solid mass to the mass of the positive electrode sheets to be recycled is greater than or equal to a preset value, the positive electrode sheets to be recycled are designated as the second positive electrode sheet. If the percentage of the remaining solid mass to the mass of the positive electrode sheets to be recycled is less than the preset value, the positive electrode sheets to be recycled are designated as the third positive electrode sheet. Optionally, the preset value is 85%~91%.

3. The method for recycling the positive electrode sheet according to claim 1, characterized in that, The first positive electrode material, the second positive electrode material and the third positive electrode material are mixed in a mass ratio of (5~8):(2~3):

1.

4. The method for recycling the positive electrode sheet according to any one of claims 1 to 3, characterized in that, All positive electrode sheets are liquid-filled electrode sheets. After mixing the first positive electrode material, the second positive electrode material and the third positive electrode material in a mass ratio of (4~8):(1~5):1, and before sintering the mixture, a lithium supplement agent is added.

5. The method for recycling the positive electrode sheet according to claim 4, characterized in that, The amount of lithium supplement added is determined by the following steps: Take a portion of the mixture of the first cathode material, the second cathode material, and the third cathode material, and test the Li element content and the metal element content, wherein the metal element includes one or more of Fe, Co, Ni, and Mn; The amount of lithium supplement agent to be added is determined based on the Li element content and the metal element content.

6. The method for recycling the positive electrode sheet according to any one of claims 1 to 3, characterized in that, The positive electrode sheets are all liquid-filled electrode sheets. In the step of sintering the mixture under a protective atmosphere, the sintering temperature is 600℃~800℃, and the sintering time is 7h~15h; or... All positive electrode sheets are unfilled with liquid. In the step of sintering the mixture under a protective atmosphere, the sintering temperature is 400℃~600℃ and the sintering time is 3h~10h.

7. The method for recycling the positive electrode sheet according to any one of claims 1 to 3, characterized in that, Following the step of sintering the mixture under a protective atmosphere, the process further includes a crushing step to reduce the particle size D of the crushed material. v50 ≤1.5μm.

8. The method for recycling the positive electrode sheet according to any one of claims 1 to 3, characterized in that, The particle size D of the first cathode material, the second cathode material, and the third cathode material v50 Each independently ≤5μm; and / or, The aqueous solution includes one or more of water and acidic aqueous solutions; optionally, the acidic aqueous solution includes one or both of citric acid solution and phosphoric acid solution; and / or, In the step of crushing and separating the third positive electrode sheet, separation is carried out based on the density difference of the crushed material.

9. A method for recycling cathode materials, characterized in that, It is obtained by the recycling method of the positive electrode sheet according to any one of claims 1 to 8.

10. A battery, characterized in that, Includes the recycled cathode material as described in claim 9.

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