Method for recycling positive electrode active material

Abstract

The application discloses a recycling method of a positive electrode active material and relates to the technical field of battery recycling. The recycling method comprises the following steps: calcining a positive electrode sheet in a protective gas environment, so that boehmite included in the positive electrode sheet is dehydrated and decomposed, and calcium hydroxide wrapped by the boehmite is exposed; soaking the calcined positive electrode sheet in an alkali solution, so that the calcium hydroxide is dissolved and aluminum oxide after dehydration and decomposition of the boehmite is absorbed; filtering residues in the soaking solution, and drying the residues to obtain the positive electrode active material. In the application, the binder on the positive electrode sheet is decomposed during calcination, so that the positive electrode active material is easily separated from the foil, and the calcium hydroxide wrapped by the boehmite is exposed, thereby facilitating subsequent processing; when the calcined positive electrode sheet is soaked in the alkali solution, the positive electrode active material falls off in the soaking solution, and the exposed calcium hydroxide is dissolved in the alkali solution, so that calcium is removed; and thus the recycling efficiency is ensured, and the quality of the positive electrode active material is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of recycling of energy storage devices, in particular to a recycling method of positive electrode active material. BACKGROUND

[0002] Energy storage devices, such as lithium secondary batteries, have the advantages of high working voltage, high stability, long cycle life, good safety performance, etc., and are one of the most important battery systems for new energy vehicles. The current treatment process of waste lithium batteries includes pretreatment of the battery and recovery of valuable components in various materials (electrolyte, negative electrode sheet, positive electrode sheet, etc.). These processes are extremely challenging. Among them, the pretreatment of the battery includes battery discharge, electrolyte collection, shell removal, cell disassembly, recovery of graphite on the negative electrode sheet, and recovery of positive electrode active material on the positive electrode sheet.

[0003] The treatment technology for recycling of waste lithium batteries has high energy consumption and complex smelting process, which makes it difficult to achieve effective economic benefits in smelting recovery. In order to improve the recovery benefit and shorten the recycling process of waste lithium batteries, most battery recycling units directly crush the discharged battery or crush the cell after removing the shell to obtain waste materials, and then recover the positive electrode active material from the waste materials. Although this treatment is more efficient, it also brings problems such as difficulty in removing some impurities, large loss of lithium, etc. SUMMARY

[0004] One of the main purposes of the present application is to provide a recycling method of positive electrode active material which can realize effective recovery of positive electrode active material.

[0005] To achieve the above application purposes, the present application adopts the following technical solutions:

[0006] According to one aspect of the present application, a recycling method of positive electrode active material is provided, comprising:

[0007] calcining the disassembled positive electrode sheet so that boehmite included in the positive electrode sheet is dehydrated and decomposed, and calcium hydroxide wrapped by the boehmite is exposed, and the calcining temperature is greater than or equal to 300°C and less than or equal to 600°C;

[0008] immersing the calcined positive electrode sheet in an alkali solution to dissolve the calcium hydroxide and absorb aluminum oxide after dehydration and decomposition of the boehmite, and the pH value of the alkali solution is greater than or equal to 12 and less than or equal to 14;

[0009] filtering the residue in the soaking liquid and drying the residue to obtain the positive electrode active material.

[0010] In the embodiment of the present application, the calcination in the protective gas environment can avoid damage to the foil and other materials of the positive electrode sheet, and at the same time, the binder on the positive electrode sheet is decomposed, which facilitates the positive active material to fall off from the foil, and at the same time, the boehmite is dehydrated to alumina during calcination, so that the calcium hydroxide wrapped by the boehmite is exposed, thereby facilitating subsequent processing. When the calcined positive electrode sheet is immersed in an alkali solution, the alkali solution can absorb the alumina on the positive electrode sheet, and the exposed calcium hydroxide can be dissolved in the alkali solution, and at the same time, the positive active material falls off in the immersion solution, so as to achieve the removal of calcium in the positive active material. Then, the filter residue can be obtained by filtration, and after drying, the positive active material is obtained, so as to ensure the recovery efficiency while improving the quality of the positive active material.

[0011] According to an embodiment of the present application, the calcination temperature of the positive electrode sheet is greater than or equal to 400°C and less than or equal to 500°C, and the calcination time is greater than or equal to 1h and less than or equal to 3h.

[0012] In the embodiment of the present application, by limiting the calcination temperature and calcination time of the positive electrode sheet, the decomposition of the binder included in the positive electrode sheet is ensured, and the boehmite can be completely dehydrated, thereby facilitating the subsequent falling off of the positive active material from the foil and the processing of the exposed calcium hydroxide, and improving the quality of the recovered positive active material.

[0013] According to an embodiment of the present application, the protective gas is nitrogen or argon.

[0014] According to an embodiment of the present application, the alkali solution is selected from at least one of sodium hydroxide and potassium hydroxide.

[0015] According to an embodiment of the present application, before calcining the positive electrode sheet, the method comprises: disassembling the positive electrode sheet, and crushing the disassembled positive electrode sheet.

[0016] In the embodiment of the present application, for the disassembled positive electrode sheet, after the crushing treatment, the size of the positive electrode sheet to be calcined is reduced, and the exposed area is increased, thereby improving the calcination effect.

[0017] According to an embodiment of the present application, the pH value of the immersion solution is less than or equal to 14.

[0018] In the embodiment of the present application, by limiting the maximum value of the pH of the immersion solution, the absorption of the alkali solution to the positive active material (such as the reaction of calcium hydroxide and lithium iron phosphate) is reduced, thereby improving the recovery efficiency of the positive active material.

[0019] According to an embodiment of the present application, filtering the filter residue in the immersion solution and drying the filter residue comprises:

[0020] Filtering the immersion solution to obtain a filter cake formed by the filter residue.

[0021] The filter cake is dried and then ground into powder to obtain the positive electrode active material.

[0022] In this embodiment, the soaking solution after soaking can be filtered by pressure filtration to improve the filtration rate. In addition, positive electrode active material in the form of filter cake is obtained after pressure filtration, which facilitates the transfer from the pressure filtration equipment to the drying equipment, thereby simplifying the process operation of positive electrode active material in the recycling process.

[0023] According to one embodiment of this application, the process before drying the filter cake includes:

[0024] The filter cake is rinsed with clean water to remove impurities.

[0025] In this embodiment of the application, rinsing the filter cake can effectively remove residual impurities on the filter cake, thereby further improving the quality of the recovered positive electrode active material.

[0026] According to one embodiment of this application, filtering the filter residue in the soaking solution and drying the filter residue includes:

[0027] Filter the soaking solution to obtain filter residue;

[0028] The filter residue is rinsed with clean water to remove impurities.

[0029] The filter residue after drying and removing impurities is used to obtain the positive electrode active material.

[0030] In this embodiment, since the filter residue after filtration is granular, impurities in the filter residue can be effectively removed by rinsing. After drying, granular positive electrode active material can be directly obtained, thereby improving the quality of the positive electrode active material while reducing the complexity of the recycling process.

[0031] According to one embodiment of this application, the water content of the positive electrode active material is less than or equal to 100 ppm.

[0032] In this embodiment of the application, the quality of the recovered positive electrode active material is improved by limiting the water content in the dried positive electrode active material.

[0033] According to one embodiment of this application, the positive electrode active material includes at least one of lithium cobalt oxide, lithium iron phosphate, lithium manganese oxide, and lithium manganese iron phosphate.

[0034] In this embodiment of the application, by explaining the positive electrode active material, the recycling method can be used to recycle the positive electrode active material included in different types of positive electrode sheets, thereby improving the applicability of the recycling method.

[0035] It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the application, as claimed. BRIEF DESCRIPTION OF DRAWINGS

[0036] The above and other features and advantages of the present application will become more apparent by describing in detail exemplary embodiments thereof. Reference will be made to the accompanying drawings to

[0037] Figure 1 is a structural schematic diagram of a positive electrode sheet according to an exemplary embodiment.

[0038] Figure 2 is a flow schematic diagram of a positive electrode active material recovery according to an exemplary embodiment.

[0039] In the drawings:

[0040] 10, positive electrode sheet;

[0041] 1, foil; 2, positive electrode paste; 3, insulating material. DETAILED DESCRIPTION

[0042] Example embodiments will now be described more fully with reference to the accompanying drawings. Example embodiments, however, can be implemented in many different forms and should not be construed as limited to the implementations set forth in this disclosure; rather, these implementations are provided so that this disclosure will be thorough and complete, and will fully convey the inventive concept of example embodiments to those skilled in the art. Like reference numerals refer to like elements throughout the specification.

[0043] As shown in Figure 1 , the positive electrode sheet 10 includes a foil 1, a positive electrode paste 2 coated on the foil, and an insulating material 3 coated on both sides of the positive electrode paste 2 in the width direction of the foil. The positive electrode paste 2 includes a positive electrode active material, the insulating material 3 is boehmite (soft water aluminum (γ-AlOOH, hydrated aluminum oxide), and the boehmite is wrapped with calcium hydroxide.

[0044] In the recovery of the positive electrode active material included in the positive electrode paste 2, only the removal of the boehmite is considered in the related art, and how to remove the calcium hydroxide wrapped with the boehmite is not considered, thereby causing the calcium in the recovered positive electrode active material to exceed the standard, and further affecting the quality of the positive electrode active material.

[0045] To this end, the present application provides a recovery method of a positive electrode active material, which can effectively reduce the content of calcium in the positive electrode active material, thereby improving the quality of the positive electrode active material while ensuring the recovery efficiency. As shown in Figure 2 , the recovery method includes the following steps S201-S203.

[0046] Step S201, calcining the positive electrode sheet, so that the boehmite included in the positive electrode sheet is dehydrated and decomposed, and the calcium hydroxide wrapped by the boehmite is exposed, and the calcination temperature of the positive electrode sheet is greater than or equal to 300°C and less than or equal to 600°C.

[0047] Step S202, soaking the calcined positive electrode sheet in an alkali solution to dissolve the calcium hydroxide and absorb the aluminum oxide after the dehydration and decomposition of the boehmite, and the pH value of the alkali solution is greater than or equal to 12 and less than or equal to 14.

[0048] Step S203, filtering the residue in the soaking liquid, and drying the residue to obtain the positive electrode active material.

[0049] In the embodiments of the present application, the calcination in a protective gas environment can avoid damage to the foil and the like of the positive electrode sheet, and at the same time, the binder on the positive electrode sheet can be decomposed, which facilitates the positive electrode active material to fall off from the foil, and at the same time, the boehmite is dehydrated to aluminum oxide during calcination, so that the calcium hydroxide wrapped by the boehmite is exposed, thereby facilitating subsequent processing; when the calcined positive electrode sheet is soaked in an alkali solution, the alkali solution can absorb the aluminum oxide on the positive electrode sheet, and the exposed calcium hydroxide can be dissolved in the alkali solution, and at the same time, the positive electrode active material falls off in the soaking liquid, so as to realize the removal of calcium in the positive electrode active material; then the residue can be obtained by filtering, and the positive electrode active material can be obtained after drying, so as to ensure the recovery efficiency while improving the quality of the positive electrode active material.

[0050] In the embodiments of the present application, the positive electrode active material recovered by the recovery method includes at least one of lithium cobaltate, lithium iron phosphate, lithium manganate, and lithium iron manganate, so that the positive electrode active material included in the positive electrode sheet of different types of single batteries can be recovered by the recovery method, so as to improve the applicability of the recovery method.

[0051] In the step S201, the protective gas selected during calcination of the positive electrode sheet can be at least one of nitrogen and a noble gas, so as to avoid oxidation of the foil during calcination.

[0052] In the embodiments of the present application, the positive electrode sheet can be calcined in a calcination furnace, or can be calcined in an atmosphere furnace.

[0053] When the positive electrode sheet is calcined in the calcination furnace, the protective gas can be continuously introduced into the calcination furnace due to the poor sealing property of the calcination furnace. The introduction rate of the protective gas can be determined according to actual needs (such as the sealing property of the calcination furnace, the volume of the calcination furnace, etc.), and for example, the protective gas is nitrogen, and the introduction rate of the nitrogen is 2 liters per minute.

[0054] When the positive electrode sheet is calcined in the atmosphere furnace, the atmosphere furnace has better sealing performance, so the atmosphere furnace can be filled with protective gas for replacement before calcining the positive electrode sheet to avoid the formation of oxidizing conditions in the atmosphere furnace. Of course, the atmosphere furnace can also be filled with protective gas during the calcination of the positive electrode sheet, and the embodiments of the present application do not limit this.

[0055] In the above step S201, calcination is mainly used to achieve the decomposition of the binder and the dehydration of boehmite, so that the calcination temperature of the positive electrode sheet can be determined in advance according to the decomposition temperature of the binder and the dehydration temperature of boehmite. Alternatively, the calcination temperature of the positive electrode sheet is greater than or equal to 300°C. When the positive electrode sheet is calcined, in order to avoid damage to the foil of the positive electrode sheet caused by a high temperature environment (the higher the temperature, the more easily the foil is decomposed), the calcination temperature of the positive electrode sheet cannot be too high. Alternatively, the calcination temperature of the positive electrode sheet is less than or equal to 600°C. That is, the calcination temperature of the positive electrode sheet is greater than or equal to 300°C and less than or equal to 600°C.

[0056] Preferably, the calcination temperature of the positive electrode sheet is greater than or equal to 400°C and less than or equal to 500°C to further ensure the calcination effect of the positive electrode sheet. For example, the calcination temperature of the positive electrode sheet is 400°C, 420°C, 440°C, 460°C, 480°C, 500°C, etc.

[0057] When the positive electrode sheet is calcined, in order to ensure that the binder included in the positive electrode sheet can be completely decomposed and the boehmite can be completely dehydrated, the positive electrode sheet can be calcined for a certain length of time (the higher the calcination temperature, the shorter the calcination time). Alternatively, the calcination time of the positive electrode sheet is greater than or equal to 1h. For example, the calcination time of the positive electrode sheet is 1h, 1.5h, 2h, 2.5h, etc. In order to avoid wasting resources due to too long a time, the longest calcination time of the positive electrode sheet can be controlled. Alternatively, the calcination time of the positive electrode sheet is less than or equal to 3h.

[0058] It should be noted that when the positive electrode sheet is calcined, the smaller the size of the positive electrode sheet, the greater the exposed area of the positive electrode sheet, and thus the better the calcination effect. Therefore, before the above step S201, the positive electrode sheet can also be disassembled and the disassembled positive electrode sheet can be crushed (such as cutting or cutting treatment, etc.). In this way, the crushing treatment of the disassembled positive electrode sheet improves the calcination effect.

[0059] In the above step S202, since the positive electrode active material is basically not dissolved in the alkali solution (or only partially dissolved in the alkali solution), when the calcined positive electrode sheet is soaked in the alkali solution, the positive electrode active material will fall off from the foil and precipitate in the soaking solution.

[0060] The pH value of the alkali solution is greater than or equal to 12 and less than or equal to 14. In this way, when the calcined positive electrode sheet is soaked in the alkali solution, the alumina after decomposition of boehmite can be effectively absorbed, and the exposed calcium hydroxide on the positive electrode sheet can be dissolved, so as to minimize the residual aluminum and calcium in the precipitate (positive active material falling off in the soaking solution) of the soaking solution.

[0061] In addition, when the calcined positive electrode sheet is soaked in the alkali solution, in order to ensure that the alkali solution can completely absorb the alumina after decomposition of boehmite and dissolve the exposed calcium hydroxide on the positive electrode sheet, the ratio of the mass (in grams) of the positive electrode sheet selected before calcination to the volume (in milliliters) of the alkali solution is less than or equal to 2.

[0062] Of course, in the embodiments of the present application, the pH value of the alkali solution can also be slightly less than 12, such as the pH value of the alkali solution being 11, and the like, which is not limited in the embodiments of the present application. When the pH value of the alkali solution is 11, with the dissolution of calcium hydroxide in the alkali solution, the pH value of the alkali solution will increase, thereby ensuring the absorption of the alumina by the alkali solution.

[0063] In some embodiments, the alkali solution is selected from at least one of sodium hydroxide and potassium hydroxide. That is, the alkali solution can be at least one of a sodium hydroxide solution and a potassium hydroxide solution.

[0064] Taking the sodium hydroxide solution as an example, after the calcined positive electrode sheet is soaked in the sodium hydroxide solution, the alumina reacts with the sodium hydroxide to generate sodium aluminate and water, and the reaction chemical formula is:

[0065] Al2O3+2NaOH=2NaAlO2+H2O.

[0066] In some embodiments, after the calcined positive electrode sheet is soaked in the alkali solution, the pH of the soaking solution is less than or equal to 14, so as to reduce the absorption of the alkali solution to the positive active material (such as the reaction of sodium hydroxide with lithium iron phosphate), thereby improving the recovery efficiency of the positive active material.

[0067] In the above step S203, for the positive active material precipitated in the soaking solution, the wet positive active material can be obtained by filtration, and then the filter residue after filtration is dried to remove the water in the positive active material, thereby improving the quality of the recovered positive active material. Alternatively, the water content of the positive active material is less than or equal to 100 ppm.

[0068] In some embodiments, the step S203 comprises: filtering the soaking liquid to obtain filter cake formed by filter residue; drying the filter cake, and grinding the dried filter cake into powder to obtain the positive electrode active material. In this way, the soaking liquid after the step S202 can be filtered by pressure filtration to improve the filtration rate. In addition, the positive electrode active material in the form of filter cake is obtained after pressure filtration, which facilitates the transfer from the pressure filtration equipment to the drying equipment, thereby simplifying the process operation of the positive electrode active material in the recycling process.

[0069] Optionally, in order to avoid the impurities remaining on the filter cake, thereby affecting the quality of the recycled positive electrode active material, the filter cake after pressure filtration can be washed with clean water before drying to remove the impurities on the filter cake.

[0070] In some embodiments, the filter cake can be washed with distilled water, hydrogen peroxide or the like for multiple times to improve the washing effect of the impurities on the filter cake.

[0071] In some embodiments, the step S203 comprises: filtering the soaking liquid to obtain filter residue; washing the filter residue with clean water to remove the impurities in the filter residue; drying the filter residue after removing the impurities to obtain the positive electrode active material. In this way, after the filter residue is obtained by filtration, the impurities in the filter residue can be effectively removed by washing the filter residue since the filter residue is in the form of particles. After drying, the positive electrode active material in the form of particles is directly obtained, which improves the quality of the positive electrode active material and reduces the complexity of the process in recycling.

[0072] In some embodiments, the washing liquid used for washing the filter residue can be distilled water, hydrogen peroxide or the like, and the filter residue can be washed for multiple times to improve the washing effect of the filter residue.

[0073] Next, the recycling of the positive electrode active material is explained by actual application.

[0074] Example 1

[0075] Take 1 kg of positive electrode sheet in the atmosphere furnace, wherein the mass of boehmite is: 10g; the mass of calcium hydroxide is: 1g. The weighed positive electrode sheet is placed in the atmosphere furnace for calcination, the calcination temperature is 400℃ respectively, the corresponding calcination time is 3h, the protective gas introduced in the atmosphere furnace is nitrogen, and the flow rate of the protective gas is 2L / min; 500ml of sodium hydroxide solution is configured, the pH of the sodium hydroxide solution is 14, the calcined positive electrode sheet is cooled to room temperature, and then is placed in the sodium hydroxide solution for immersion at room temperature, the stirring rate in the immersion process is 60r / min, and the immersion time is 10min, at this time the pH of the immersion solution after immersion is 14; the immersion solution after immersion is filtered by a filter press to obtain positive electrode active material in the form of filter cake, the filter cake is dried and ground into powder to obtain granular positive electrode active material. The mass of the positive electrode active material is 900g, the mass of aluminum is less than or equal to 100ppm, the mass of calcium is less than or equal to 20, and the water content is less than 1000ppm. It can be seen that the recovered positive electrode active material has high quality.

[0076] Example 2

[0077] Take 1 kg of positive electrode sheet in the atmosphere furnace, wherein the mass of boehmite is: 10g; the mass of calcium hydroxide is: 1g. The weighed positive electrode sheet is placed in the atmosphere furnace for calcination, the calcination temperature is 400℃ respectively, the corresponding calcination time is 3h, the protective gas introduced in the atmosphere furnace is nitrogen, and the flow rate of the protective gas is 2L / min; 500ml of sodium hydroxide solution is configured, the pH of the sodium hydroxide solution is 14, the calcined positive electrode sheet is cooled to room temperature, and then is placed in the sodium hydroxide solution for immersion at room temperature, the stirring rate in the immersion process is 60r / min, and the immersion time is 10min, at this time the pH of the immersion solution after immersion is 14; the immersion solution after immersion is filtered by a filter press to obtain positive electrode active material in the form of filter cake, the filter cake is dried and ground into powder to obtain granular positive electrode active material. The mass of the positive electrode active material is 900g, the mass of aluminum is less than or equal to 100ppm, the mass of calcium is less than or equal to 20, and the water content is less than 1000ppm. It can be seen that the recovered positive electrode active material has high quality.

[0078] Example 3

[0079] Take 1 kg of positive electrode sheet into the atmosphere furnace, wherein the mass of boehmite is: 10 g; the mass of calcium hydroxide is: 1 g. The weighed positive electrode sheet is placed in the atmosphere furnace for calcination, the calcination temperature is 500 DEG C respectively, the corresponding calcination time is 2 h, the protective gas introduced into the atmosphere furnace is nitrogen, and the flow rate of the protective gas is 2 L / min; 500 milliliters of sodium hydroxide solution is configured, the pH of the sodium hydroxide solution is 14, the calcined positive electrode sheet is cooled to room temperature, and then placed into the sodium hydroxide solution for immersion at room temperature, the stirring rate in the immersion process is 60 revolutions / min, and the immersion time is 10 min, at this time the pH of the immersion solution after immersion is 14; the immersion solution after immersion is filtered by a filter press to obtain positive active material in the form of filter cake, the filter cake is dried and polished into powder to obtain granular positive active material. The mass of the positive active material is 900 g, the mass of aluminum is less than or equal to 100 ppm, the mass of calcium is less than or equal to 20, and the water content is less than 1000 ppm. It can be seen that the recovered positive active material has high quality.

[0080] In the embodiments of the application, the terms "first", "second", "third" are only used for descriptive purposes and should not be construed as indicating or implying relative importance; the term "multiple" refers to two or more, unless otherwise explicitly limited. The terms "mounting", "connecting", "connecting", "fixing" and the like should be interpreted broadly, for example, "connecting" can be fixed connection, or detachable connection, or integrally connected; "connected" can be directly connected, or indirectly connected through an intermediate medium. For those skilled in the art, the specific meaning of the above terms in the embodiments of the application can be understood according to the specific circumstances.

[0081] In the description of the embodiments of the application, it should be understood that the terms "upper", "lower", "left", "right", "front", "back" and the like indicate the orientation or positional relationship shown in the drawings, and are only used for the purpose of facilitating the description of the embodiments of the application and simplifying the description, and therefore, cannot be understood as indicating or implying that the devices or units referred to must have a particular direction, be constructed and operated in a particular orientation, therefore, cannot be understood as limiting the embodiments of the application.

[0082] In the description of the present specification, the description of the terms "one embodiment", "some embodiments", "a specific embodiment" and the like means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the application. In the present specification, the illustrative description of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0083] The above merely provides preferred embodiments of the application, and is not intended to limit the application. The application can be variously changed and modified by those skilled in the art. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the application shall fall within the protection scope of the application.

Claims

1. A recovery method of a positive electrode active material, characterized by, The application relates to a preparation method of a positive electrode active material. The positive electrode sheet is calcined in a protective gas environment, so that boehmite included in the positive electrode sheet is dehydrated and decomposed, and calcium hydroxide wrapped by the boehmite is exposed, the calcination temperature is greater than or equal to 300 DEG C and less than or equal to 600 DEG C; The calcined positive electrode sheet is soaked in an alkali solution to dissolve the calcium hydroxide and absorb aluminum oxide after dehydration and decomposition of the boehmite, the pH value of the alkali solution is greater than or equal to 12 and less than or equal to 14; The filter residue in the soaking liquid is filtered and dried to obtain the positive electrode active material.

2. The recycling method of claim 1, wherein, The calcination temperature of the positive electrode sheet is greater than or equal to 400 DEG C and less than or equal to 500 DEG C, and the calcination time is greater than or equal to 1 h and less than or equal to 3 h.

3. The recycling method of claim 1, wherein, The protective gas is nitrogen or argon.

4. The recycling method of claim 1, wherein, The alkali solution is at least one selected from sodium hydroxide and potassium hydroxide.

5. The recycling method of claim 1, wherein, Before the positive electrode sheet is calcined, the positive electrode sheet is disassembled and crushed.

6. The recovery method according to any one of claims 1 to 5, characterized in that, The filter residue in the soaking liquid is filtered and dried, including: The soaking liquid is pressure-filtered to obtain filter cake formed by the filter residue; The filter cake is dried and ground into powder after drying to obtain the positive electrode active material.

7. The recycling method of claim 6, wherein, Before the filter cake is dried, the method comprises: The filter cake is washed with clean water to remove impurities on the filter cake.

8. The recycling method according to any one of claims 1 to 5, characterized in that, The filter residue in the soaking liquid is filtered and dried, including: The soaking liquid is filtered to obtain filter residue; The filter residue is washed with clean water to remove impurities in the filter residue; The filter residue after impurities are removed is dried to obtain the positive electrode active material.

9. The recycling method of claim 1, wherein, The water content of the positive electrode active material is less than or equal to 100 ppm.

10. The recycling method of claim 1, wherein, The positive electrode active material comprises at least one of lithium cobaltate, lithium iron phosphate, lithium manganate and lithium iron manganese phosphate.

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