Recovery method and recovery device of positive electrode active material

Abstract

The invention provides a recovery method and a recovery device of a positive electrode active material. The recycling method comprises the steps that the positive pole piece is placed in a solvent to be soaked at the high temperature of 100-180 DEG C to obtain the positive pole piece with the binder removed, the solvent is a good solvent of the binder in the positive pole piece, and the high-temperature soaking temperature is 100-180 DEG C; drying the positive pole piece from which the binder is removed, and eluting and removing powder to obtain slurry; and drying the slurry, and recovering to obtain the positive electrode active material. And the impurity content in the recycled positive electrode active material is reduced.

Description

Technical Field

[0001] The present application relates to the field of battery technology, and in particular to a method and device for recovering positive electrode active materials. Background Art

[0002] With the rapid development of the new energy vehicle industry, the number of scrapped lithium-ion power batteries is expected to surge. Consequently, there will be a huge market demand for power battery recycling. Power battery recycling primarily involves two technical aspects: first, recycling active materials in battery materials, such as ternary lithium materials, lithium iron phosphate materials, and current collector metal materials, to reduce resource waste; second, establishing effective power battery recycling methods to minimize the environmental impact of waste lithium-ion batteries, such as pollution from organic matter, dust, and heavy metals, to achieve the healthy and sustainable development of lithium-ion power batteries. Summary of the Invention

[0003] The present application provides a method and apparatus for recovering positive electrode active materials, so as to reduce the impurity content in the recovered positive electrode active materials.

[0004] The first aspect of the present application provides a method for recovering positive electrode active materials, which includes: placing a positive electrode plate in a solvent for high-temperature immersion to obtain a positive electrode plate with the binder removed, the solvent is a good solvent for the binder in the positive electrode plate, and the temperature of the high-temperature immersion is 100°C-180°C; drying the positive electrode plate with the binder removed, washing and removing powder to obtain a slurry; drying the slurry, and recovering the positive electrode active material.

[0005] The above-mentioned recovery method subjects the positive electrode sheets to a high-temperature soaking treatment. On the one hand, the positive electrode sheets do not undergo a crushing treatment or ultrasonic treatment, so the current collector of the positive electrode sheets does not form debris and form an intermixing with the positive electrode active material. On the other hand, the high-temperature soaking causes the binder in the positive electrode sheets to quickly dissolve into the solvent, and the positive electrode active material can be adsorbed on the positive electrode current collector due to the pressure during the preparation of the positive electrode sheets. The positive electrode sheets are then dried, washed and de-powdered, and the binder content in the resulting slurry is extremely low. Therefore, the separation of the positive electrode active material and the liquid in the slurry is relatively easy, and the content of impurities such as metals and binders in the recovered positive electrode active material is extremely low.

[0006] In any embodiment of the first aspect, the high-temperature immersion time is 0.5 h to 3 h, and the ratio of the positive electrode sheet to the solvent during the high-temperature immersion is 1 g:10 mL to 1 g:30 mL, so as to further improve the recovery efficiency.

[0007] In any embodiment of the first aspect, the high-temperature immersion is performed under gas protection, and the gas includes nitrogen or an inert gas. The above gas is used to isolate the air and improve operational safety.

[0008] In any embodiment of the first aspect, the binder in the positive electrode sheet is an oil-soluble binder, and the solvent includes N-methylpyrrolidone.

[0009] In any embodiment of the first aspect, the positive electrode sheet from which the binder is removed is vacuum dried at 100° C.-150° C.

[0010] In any embodiment of the first aspect, the solvent in the drying process of the positive electrode sheet after the binder is removed is collected and returned to the high-temperature soaking process as a solvent, thereby saving reagent costs and reducing pollution caused by solvent volatilization.

[0011] In any embodiment of the first aspect, the eluting and removing the powder comprises spraying the dried positive electrode sheet with water.

[0012] In any embodiment of the first aspect, the process of drying the slurry comprises: filtering the slurry to obtain a filter cake and a filtrate; and vacuum drying the filter cake to recover the positive electrode active material.

[0013] In any embodiment of the first aspect, the filtrate is returned to the elution and de-powdering process to be used for spraying the dried positive electrode sheet.

[0014] In any embodiment of the first aspect, the recovery method further comprises the process of crushing and demagnetizing the recovered positive electrode active material.

[0015] The second aspect of the present application provides a recovery device for positive electrode active materials, which includes: a soaking unit, the soaking unit including a soaking container for soaking positive electrode sheets and a heating device for heating the soaking container; a first drying unit, arranged downstream of the soaking unit, for drying the positive electrode sheets to remove the binder; an elution unit, arranged downstream of the first drying unit, for eluting and de-powdering the dried positive electrode sheets to obtain a slurry; and a second drying unit, arranged downstream of the elution unit, for drying the slurry to recover the positive electrode active material.

[0016] The above-mentioned immersion unit of the recovery device is used to perform high-temperature immersion treatment on the positive electrode sheet. On the one hand, the positive electrode sheet does not undergo crushing treatment and ultrasonic treatment, so the current collector of the positive electrode sheet will not form debris and be mixed with the positive electrode active material. On the other hand, the high-temperature immersion allows the binder in the positive electrode sheet to be quickly dissolved into the solvent, and the positive electrode active material can be adsorbed on the positive electrode collector due to the pressure during the preparation of the positive electrode sheet; then the positive electrode sheet is dried, eluted and de-powdered using the first drying unit and the elution unit. The content of binder in the obtained slurry is extremely small, so it is easier to separate the positive electrode active material and the liquid in the slurry, and the content of impurities such as metal and binder in the recovered positive electrode active material is extremely small.

[0017] In any embodiment of the second aspect, the immersion container has a gas inlet, and the immersion unit further includes a gas supply device connected to the gas inlet for supplying gas into the immersion container, wherein the gas supply device is a nitrogen supply device or an inert gas supply device. The gas provided by the gas supply device isolates the air, thereby improving operational safety.

[0018] In any embodiment of the second aspect, the first drying unit is a first vacuum drying unit, and the first drying unit further includes a steam condensation device connected to the immersion container for returning the collected condensate to the immersion container for recycling.

[0019] In any embodiment of the second aspect, the elution unit includes a high-pressure spray device, which is used to spray the dried positive electrode sheet.

[0020] In any embodiment of the second aspect, the second drying unit includes: a filter press device; and a vacuum drying device disposed downstream of the filter press device for drying a filter cake from the filter press device.

[0021] In any embodiment of the second aspect, the filter press equipment includes a filtrate collector, which is connected to the elution unit for returning the collected filtrate to the elution unit for elution and de-powdering of the positive electrode sheet.

[0022] In any embodiment of the second aspect, the recovery device further includes a pulverizing device and a demagnetizing device sequentially arranged downstream of the second drying unit. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following is a brief introduction to the drawings required for use in the embodiments of the present application. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on the drawings without creative work.

[0024] Figure 1 A flow chart of a method for recovering positive electrode active materials provided in some embodiments of the present application.

[0025] Figure 2 Flowchart of a method for recovering positive electrode active materials provided in some other embodiments of the present application.

[0026] Figure 3 This is a structural block diagram of a positive electrode active material recovery device provided in some embodiments of the present application.

[0027] Figure 4 This is a structural block diagram of a positive electrode active material recovery device provided in some other embodiments of the present application.

[0028] In the drawings, the drawings are not drawn to scale.

[0029] Description of reference numerals:

[0030] 10 soaking unit; 11 soaking container; 12 heating equipment; 13 gas supply equipment; 20 first drying unit; 21 steam condensation equipment; 30 elution unit; 31 high-pressure spraying equipment; 40 second drying unit; 41 filter press equipment; 411 filtrate collector; 42 vacuum drying equipment; 50 crushing unit; 60 demagnetization unit. DETAILED DESCRIPTION

[0031] The following detailed description of the embodiments of the present application is provided in conjunction with the accompanying drawings and examples. The following detailed description of the embodiments and the accompanying drawings are used to illustrate the principles of the present application, but are not intended to limit the scope of the present application, that is, the present application is not limited to the described embodiments.

[0032] Below, with appropriate reference to the accompanying drawings, the embodiments of the positive electrode active material recovery method and recovery device of the present application are described in detail. However, there may be cases where unnecessary detailed descriptions are omitted. For example, there may be cases where detailed descriptions of well-known matters and repeated descriptions of actually the same structures are omitted. This is to avoid the following description from becoming unnecessarily lengthy and to facilitate the understanding of those skilled in the art. In addition, the drawings and the following description are provided to enable those skilled in the art to fully understand the present application and are not intended to limit the subject matter described in the claims.

[0033] " range " disclosed in the present application is limited in the form of lower limit and upper limit, and given range is limited by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundary of special range. The scope limited in this way can be to include end value or not include end value, and can be arbitrarily combined, that is, any lower limit can form a range with any upper limit combination. For example, if the scope of 60-120 and 80-110 is listed for specific parameters, it is understood that the scope of 60-110 and 80-120 is also expected. In addition, if the minimum range value 1 and 2 are listed, and if the maximum range value 3,4 and 5 are listed, then the following range can all be expected: 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5. In this application, unless otherwise specified, the numerical range " ab " represents the abbreviation of any real number combination between a and b, wherein a and b are all real numbers. For example, a numerical range of "0-5" indicates that all real numbers between "0-5" are listed herein, and "0-5" is simply an abbreviation for these numerical combinations. Furthermore, when a parameter is expressed as an integer ≥ 2, this is equivalent to disclosing that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0034] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0035] Unless otherwise specified, all technical features and optional technical features of this application can be combined with each other to form a new technical solution.

[0036] Unless otherwise specified, all steps of the present application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially. For example, the method may further include step (c), indicating that step (c) may be added to the method in any order, for example, the method may include steps (a), (b) and (c), or may include steps (a), (c) and (b), or may include steps (c), (a) and (b), etc.

[0037] If there is no special explanation, the "include" and "comprising" mentioned in this application are open-ended. For example, the "include" and "comprising" may mean that other components not listed may also be included or comprised.

[0038] Unless otherwise specified, the term "or" is inclusive in this application. For example, any of the following conditions satisfies the condition "A or B": A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or both A and B are true (or exist).

[0039] [Secondary battery]

[0040] Secondary batteries, also known as rechargeable batteries or storage batteries, are batteries that can be recharged to activate the active materials after discharge and continue to be used.

[0041] Typically, a secondary battery includes a positive electrode sheet, a negative electrode sheet, a separator, and an electrolyte. During the battery's charge and discharge process, active ions (such as lithium ions) are embedded and released back and forth between the positive and negative electrode sheets. The separator is set between the positive and negative electrode sheets, mainly to prevent the positive and negative electrodes from short-circuiting, while allowing active ions to pass through. The electrolyte is between the positive and negative electrode sheets, mainly to conduct active ions.

[0042] [Positive electrode]

[0043] The positive electrode sheet generally includes a positive electrode current collector and a positive electrode film layer disposed on at least one surface of the positive electrode current collector, wherein the positive electrode film layer includes a positive electrode active material.

[0044] As an example, the positive electrode current collector has two surfaces opposite to each other in its thickness direction, and the positive electrode film layer is disposed on either or both of the two opposite surfaces of the positive electrode current collector.

[0045] In some embodiments, the positive electrode current collector may be a metal foil or a composite current collector. For example, aluminum foil may be used as the metal foil. The composite current collector may include a polymer material base and a metal layer formed on at least one surface of the polymer material base. The composite current collector may be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0046] In some embodiments, the positive electrode active material may adopt the positive electrode active material for batteries that is well known in the art. As an example, when the secondary battery is a lithium ion secondary battery, the positive electrode active material may include at least one of the following materials: lithium phosphates containing olivine structure, lithium transition metal oxides and their respective modified compounds. However, the present application is not limited to these materials, and other traditional materials that can be used as positive electrode active materials for batteries may also be used. These positive electrode active materials may be used alone or in combination of two or more. Among them, examples of lithium transition metal oxides may include but are not limited to lithium cobalt oxide (such as LiCoO2), lithium nickel oxide (such as LiNiO2), lithium manganese oxide (such as LiMnO2, LiMn2O4), lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide (such as LiNi 1 / 3 Co 1 / 3Mn 1 / 3 O2 (also referred to as NCM 333 ), LiNi 0.5 Co 0.2 Mn 0.3 O2 (also referred to as NCM 523 ), LiNi 0.5 Co 0.25 Mn 0.25 O2 (also referred to as NCM 211 ), LiNi 0.6 Co 0.2 Mn 0.2 O2 (also referred to as NCM 622 ), LiNi 0.8 Co 0.1 Mn 0.1 O2 (also referred to as NCM 811 ), lithium nickel cobalt aluminum oxide (such as LiNi 0.85 Co 0.15Al 0.05 O2) and its modified compounds. Examples of olivine-structured lithium-containing phosphates may include, but are not limited to, at least one of lithium iron phosphate (such as LiFePO4 (also referred to as LFP)), a composite material of lithium iron phosphate and carbon, lithium manganese phosphate (such as LiMnPO4), a composite material of lithium manganese phosphate and carbon, lithium iron manganese phosphate, and a composite material of lithium iron manganese phosphate and carbon.

[0047] When the secondary battery is a sodium-ion secondary battery, as an example, the positive electrode active material of the sodium-ion secondary battery may include at least one of the following materials: a sodium transition metal oxide, a polyanionic compound, and a Prussian blue compound. However, the present application is not limited to these materials, and other conventionally known materials that can be used as positive electrode active materials for sodium-ion batteries may also be used.

[0048] As an optional technical solution of the present application, in the sodium transition metal oxide, the transition metal can be at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr and Ce. Sodium transition metal oxide is, for example, Na x MO2, wherein M is one or more of Ti, V, Mn, Co, Ni, Fe, Cr and Cu, and 0<x≤1.

[0049] As an optional technical solution of the present application, the polyanionic compound can be a compound having sodium ions, transition metal ions and tetrahedral (YO4) n- A class of compounds with anionic units. The transition metal can be at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr and Ce; Y can be at least one of P, S and Si; n represents (YO4) n- valence.

[0050] Polyanionic compounds can also be sodium ions, transition metal ions, tetrahedral (YO4) n- A class of compounds containing anion units and halogen anions. The transition metal can be at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce; Y can be at least one of P, S, and Si, and n represents (YO4) n- valence state; the halogen may be at least one of F, Cl and Br.

[0051] The polyanionic compound can also be a compound having sodium ions, tetrahedral (YO4)n-anion units, polyhedral units (ZO y ) m+ and an optional halogen anion. Y can be at least one of P, S and Si, and n represents (YO4) n-valence state; Z represents a transition metal, which may be at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr and Ce, and m represents (ZO y ) m+ valence state; the halogen may be at least one of F, Cl and Br.

[0052] Polyanionic compounds include NaFePO4, Na3V2(PO4)3 (sodium vanadium phosphate, abbreviated as NVP), Na4Fe3(PO4)2(P2O7), NaM'PO4F (M' is one or more of V, Fe, Mn and Ni) and Na3(VO y )2(PO4)2F 3-2y At least one of (0≤y≤1).

[0053] Prussian blue compounds can be compounds containing sodium ions, transition metal ions, and cyanide ions (CN-). The transition metal can be at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce. Prussian blue compounds are, for example, Na a Me b Me' c (CN)6, wherein Me and Me' are each independently at least one of Ni, Cu, Fe, Mn, Co and Zn, 0<a≤2, 0<b<1, 0<c<1.

[0054] In some embodiments, the positive electrode film layer may further optionally include a binder. The binder may be an oily binder or an aqueous binder. For example, the oily binder may include polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and at least one of a fluorinated acrylate resin. For example, the aqueous binder may include any one or more of polyacrylic acid, styrene-butadiene rubber, and styrene-butadiene rubber.

[0055] In some embodiments, the positive electrode film layer may further include a conductive agent. For example, the conductive agent may include at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0056] In some embodiments, the positive electrode sheet can be prepared by the following method: the components for preparing the positive electrode sheet, such as the positive electrode active material, the conductive agent, the binder and any other components, are dispersed in a solvent (such as N-methylpyrrolidone) to form a positive electrode slurry; the positive electrode slurry is coated on the positive electrode current collector, and after drying, cold pressing and other processes, the positive electrode sheet can be obtained.

[0057] [Recovery Method of Positive Electrode Active Material]

[0058] At present, the positive electrode active material recovery process crushes the positive electrode sheet into fragments before de-powdering. The metal shavings formed by the current collector during the crushing process are all mixed into the positive electrode active material. The fragments are then ultrasonically immersed in a solvent for de-powdering. The ultrasonic vibration will also further break the metal foil or metal shavings into smaller particles. After filtration, the small particles of metal shavings are mixed into the positive electrode active material, resulting in a large amount of metal shavings mixed into the positive electrode active material. Therefore, these metal shavings need to be removed before the subsequent repair of the positive electrode active material, otherwise it will affect the repair and reuse of the positive electrode active material. In the above de-powdering process, the binder and the positive electrode active material are peeled off from the current collector together, resulting in a large amount of binder residue in the positive electrode active material, which also affects subsequent repair. In addition, because the binder is dissolved in the solvent, the filtration speed is slow and the recovery efficiency is low.

[0059] In order to reduce the impurity content in the recovered positive electrode active material, the first embodiment of the present application provides a method for recovering the positive electrode active material, such as Figure 1 As shown, the recycling method includes: placing the positive electrode sheet in a solvent for high-temperature immersion to obtain a positive electrode sheet with the binder removed, the solvent is a good solvent for the binder in the positive electrode sheet, and the temperature of the high-temperature immersion is 100°C-180°C; drying the positive electrode sheet with the binder removed, washing and de-powdering to obtain a slurry; drying the slurry, and recovering the positive electrode active material.

[0060] The above-mentioned recovery method performs a high-temperature immersion treatment on the positive electrode sheets. On the one hand, the positive electrode sheets do not undergo a pulverization treatment and an ultrasonic treatment (such as a static high-temperature immersion treatment), so the current collector of the positive electrode sheets will not form debris and be mixed with the positive active material. On the other hand, the high-temperature immersion causes the binder in the positive electrode sheets to quickly dissolve into the solvent, and the positive electrode active material can be adsorbed on the positive electrode collector due to the pressure during the preparation of the positive electrode sheets; then the positive electrode sheets are dried, washed and de-powdered, and the content of the binder in the obtained slurry is extremely small, so it is easier to separate the positive electrode active material and the liquid in the slurry, and the content of impurities such as metals and binders in the recovered positive electrode active materials is extremely small.

[0061] The definition of the good solvent is the conventional definition in this field, that is, a solvent that has a strong dissolving ability for the binder and an interaction parameter χ with the binder is less than 0.5.

[0062] If the temperature of the high-temperature immersion is too high, the solvent will be in a boiling state, resulting in increased operational risks.

[0063] During high-temperature immersion treatment, the binder dissolves at a faster rate. On the basis of dissolving the binder as completely as possible, in order to further improve the recovery efficiency, in some embodiments, the high-temperature immersion time is 0.5h-3h, and the ratio of the positive electrode sheet to the solvent during high-temperature immersion is 1g:10mL-1g:30mL.

[0064] When the flash point of the selected solvent is lower than the high-temperature soaking temperature, in some embodiments, the high-temperature soaking is performed under a protective gas atmosphere, such as nitrogen or an inert gas, to improve operational safety. Using such a gas to isolate the solvent from the air improves operational safety.

[0065] The solvent used in the recovery method of the present application is a good solvent for the binder, so the corresponding good solvent can be selected according to the specific binder. As an example, when the binder of the positive electrode plate is a soluble binder, the binder may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer and fluorine-containing acrylate resin, and the solvent may optionally include N-methylpyrrolidone. N-methylpyrrolidone is a commonly used good solvent for the above-mentioned binders.

[0066] In some embodiments, in order to accelerate the drying speed of the positive electrode sheet after the binder is removed, the positive electrode sheet after the binder is removed is vacuum dried at 100° C.-150° C.

[0067] In some embodiments, in order to save reagent costs and reduce pollution caused by solvent volatilization, the solvent in the drying process of the positive electrode sheet after removing the binder is collected and returned to the high-temperature soaking process as a solvent.

[0068] In some embodiments, the elution and de-powdering process includes spraying the dried positive electrode sheet with water. The high pressure generated by the spraying process is used to wash the positive electrode active material from the current collector. This process is simple and easy to implement without damaging the current collector.

[0069] The drying process of the slurry can be carried out using a drying process commonly used in the art, such as using sedimentation, filtration, or filter pressing to perform preliminary solid-liquid separation, followed by heating and drying or vacuum drying. In some embodiments, to improve drying efficiency, the slurry drying process includes: filtering the slurry to obtain a filter cake and a filtrate; and vacuum drying the filter cake to recover the positive electrode active material.

[0070] There is a physical interaction between the water used for the above-mentioned spraying and the positive electrode active material, so the water can be collected and reused repeatedly. In some embodiments, the filtrate is returned to the elution and de-powdering process to spray the dried positive electrode sheets, thereby further reducing the recycling cost.

[0071] In some embodiments, in order to further improve the purity of the positive electrode active material, as Figure 2 As shown, the recycling method also includes the process of crushing and demagnetizing the recovered positive electrode active material.

[0072] [Recovery device]

[0073] The second embodiment of the present application provides a recovery device for positive electrode active materials. Those skilled in the art can use any of the following recovery devices provided in the second embodiment to implement the recovery method provided in the first embodiment. Figure 3 As shown, the recovery device includes: a soaking unit 10, a first drying unit 20, an elution unit 30 and a second drying unit 40, the soaking unit includes a soaking container 11 for soaking the positive electrode sheet and a heating device 12 for heating the soaking container; the first drying unit 20 is arranged downstream of the soaking unit 10 for drying the positive electrode sheet to remove the binder; the elution unit 30 is arranged downstream of the first drying unit 20 for eluting and de-powdering the dried positive electrode sheet to obtain a slurry; the second drying unit 40 is arranged downstream of the elution unit 30 for drying the slurry to recover the positive electrode active material.

[0074] The above-mentioned soaking unit 10 of the above-mentioned recovery device is used to perform high-temperature soaking treatment on the positive electrode sheet. On the one hand, the positive electrode sheet does not undergo crushing treatment and ultrasonic treatment (such as static high-temperature soaking treatment), so the current collector of the positive electrode sheet will not form debris and be mixed with the positive active material. On the other hand, the high-temperature soaking allows the binder in the positive electrode sheet to be quickly dissolved into the solvent. The positive electrode active material can be adsorbed on the positive electrode collector due to the pressure during the preparation of the positive electrode sheet; then the first drying unit 20 and the elution unit 30 are used to dry, elute and de-powder the positive electrode sheet. The content of binder in the obtained slurry is extremely small, so it is easier to separate the positive electrode active material and the liquid in the slurry, and the content of impurities such as metal and binder in the recovered positive electrode active material is extremely small.

[0075] When the flash point of the solvent selected for high temperature soaking is lower than the temperature of the above high temperature soaking, in order to improve the safety of operation, in some embodiments, reference Figure 4The immersion container 11 has a gas inlet, and the immersion unit 10 further includes a gas supply device 13 connected to the gas inlet for supplying gas to the immersion container 11. The gas supply device 13 is a nitrogen supply device or an inert gas supply device. The gas provided by the gas supply device isolates the air, thereby improving operational safety.

[0076] In some embodiments, in order to accelerate the drying speed of the positive electrode sheet after removing the binder, the first drying unit is a first vacuum drying unit.

[0077] In some embodiments, in order to save reagent costs and reduce pollution caused by solvent volatilization, reference Figure 4 The first drying unit 20 further includes a steam condensing device 21, which is connected to the soaking container 11 and is used to return the collected condensate to the soaking container for recycling.

[0078] In some embodiments, reference Figure 4 The elution unit 30 includes a high-pressure spray device 31, which is used to spray the dried positive electrode sheet. The high pressure generated by the spray is used to wash the positive electrode active material on the positive electrode sheet from the current collector. The process is simple and easy to implement, and will not damage the current collector.

[0079] The second drying unit 40 can be realized by assembling a drying device commonly used in the art, such as using a sedimentation device, a filtering device or a filter press device to perform a preliminary solid-liquid separation, and then using a heating device or a vacuum drying device for further drying. Figure 4 The second drying unit 40 includes a filter press device 41 and a vacuum drying device 42. The vacuum drying device is arranged downstream of the filter press device to dry the filter cake of the filter press device.

[0080] In order to further reduce the recycling cost, in some embodiments, reference Figure 4 The filter press device includes a filtrate collector 411, which is connected to the elution unit 30 and is used to return the collected filtrate to the elution unit for elution and de-powdering of the positive electrode sheet.

[0081] In order to further improve the purity of the positive electrode active material, in some embodiments, reference Figure 4 The recovery device further includes a crushing unit 50 and a demagnetization unit 60 sequentially arranged downstream of the second drying unit.

[0082] [Example]

[0083] Below, the embodiment of the present application is described. The embodiment described below is exemplary and is only used to explain the present application, and is not to be construed as limiting the present application. Where specific techniques or conditions are not specified in the embodiments, the techniques or conditions described in the literature in this area or the product specifications are used. Reagents or instruments used that do not specify the manufacturer are conventional products that can be obtained commercially.

[0084] The mass proportion of the active material in the positive electrode sheets recovered in the following examples and comparative examples is 90.5%, the mass proportion of the aluminum foil is 8%, and the mass proportion of the adhesive is 1.5%. The current collector is aluminum foil, and the active material is LiNi 0.5 Co 0.2 Mn 0.3 O2.

[0085] Example 1

[0086] use Figure 4 The recycling device shown here performs recycling operations according to the following process:

[0087] The positive electrode sheet is immersed in the organic solvent N-methylpyrrolidone (NMP). The ratio of the ternary positive electrode sheet to N-methylpyrrolidone is 1g:20mL. The immersion temperature is controlled at 100℃-130℃, and the nitrogen atmosphere is protected. The immersion time is 3 hours. The immersion process fully dissolves the binder in the ternary active material in NMP, destroying the bonding between the active material and the current collector, and the bonding between the active material particles.

[0088] After the positive electrode sheet is soaked in NMP, it is taken out and vacuum dried at 120℃-150℃ to completely volatilize the NMP to obtain a vacuum-dried positive electrode sheet. The NMP vapor is collected by a condensation device and recycled to the high-temperature soaking step for reuse.

[0089] The vacuum-dried positive electrode sheets are washed by spraying with a high-pressure water gun, and the active materials fall off the current collector to form an active material slurry with water as the solvent. After the positive electrode sheets are sprayed to remove powder, the entire current collector aluminum foil is separated and compressed into blocks for recovery.

[0090] The active material slurry with water as the solvent is transported to the filter press through a pipeline for filtration to obtain a filter cake of the active material, which is then vacuum dried, crushed to a particle size Dv50: 4-8μm, and demagnetized using a 200-mesh sieve to obtain recovered active material; the water after filtration can be recycled and sprayed for water washing.

[0091] Example 2

[0092] The only difference from Example 1 is that the positive electrode sheet is immersed in an organic solvent, N-methylpyrrolidone (NMP), at a temperature of 150° C. to 180° C., under nitrogen atmosphere, for 0.5 h. The rest is the same as Example 1.

[0093] Example 3

[0094] The only difference from Example 1 is that the ratio of the positive electrode sheet to N-methylpyrrolidone is 1 g:10 mL, and the immersion time is 3 h.

[0095] Example 4

[0096] The only difference from Example 1 is that the ratio of the positive electrode sheet to N-methylpyrrolidone is 1 g:30 mL, and the immersion time is 3 h.

[0097] Example 5

[0098] The only difference from Example 1 is that the ratio of the positive electrode sheet to N-methylpyrrolidone is 1 g:40 mL, and the immersion time is 3 h.

[0099] Example 6

[0100] The only difference from Example 1 is that the ratio of the positive electrode sheet to N-methylpyrrolidone is 1 g:8 mL, and the immersion time is 5 h.

[0101] Comparative Example 1

[0102] The only difference from Example 1 is that the positive electrode sheet was immersed in the organic solvent N-methylpyrrolidone (NMP) at a temperature of 80°C-95°C, under a nitrogen atmosphere, for 4 hours. The rest of the process was the same as in Example 1, with a trace amount of active material remaining on the positive electrode sheet after high-pressure water jet spraying.

[0103] Comparative Example 2

[0104] Ultrasonic treatment was performed simultaneously with high-temperature immersion at the same temperature and time as in Example 1. After the ultrasonic treatment, a large area of ​​active material was found to have fallen off the surface of the current collector. There was also significant insoluble matter in the NMP, and the viscosity increased, indicating that the active material had entered the NMP. Therefore, no further treatment was performed.

[0105] Comparative Example 3

[0106] The same high-temperature soaking temperature and duration as in Example 1 were followed by stirring at 50 rpm. After stirring, a large area of ​​active material was observed to have fallen off from the current collector surface. Significant insoluble matter was present in the NMP, and the viscosity increased, indicating that the active material had entered the NMP. Therefore, no further treatment was performed.

[0107] The binder content was determined using differential scanning calorimetry (DSTA). The aluminum impurity content was determined using inductively coupled plasma optical emission spectroscopy (ICP-OES). Recovery rate: the ratio of the powder removal amount by this process to the actual powder content in the recovered electrode.

[0108] Table 1

[0109] Although the present application has been described with reference to preferred embodiments, various modifications may be made thereto and components may be substituted with equivalents without departing from the scope of the present application. In particular, the various technical features described in the various embodiments may be combined in any manner as long as there are no structural conflicts. The present application is not limited to the specific embodiments disclosed herein, but encompasses all technical solutions within the scope of the claims.

Claims

1. A method for recovering positive electrode active materials, wherein: The recovery method comprises: placing the positive electrode sheet in a solvent for high-temperature soaking to obtain a positive electrode sheet with the binder removed, wherein the solvent is a good solvent for the binder in the positive electrode sheet, and the temperature of the high-temperature soaking is 100° C.-180° C.; Drying, washing and removing powder from the positive electrode sheet from which the binder has been removed to obtain a slurry; The slurry is dried and recovered to obtain the positive electrode active material.

2. The recycling method according to claim 1, wherein: The high-temperature immersion time is 0.5h-3h, and the ratio of the positive electrode sheet to the solvent during the high-temperature immersion is 1g:10mL-1g:30mL.

3. The recovery method according to claim 1 or 2, wherein: The high-temperature soaking is performed under gas protection, and the gas includes nitrogen or an inert gas.

4. The recovery method according to any one of claims 1 to 3, wherein The binder in the positive electrode plate is an oil-soluble binder, and the solvent includes N-methylpyrrolidone.

5. The recovery method according to any one of claims 1 to 4, wherein The positive electrode sheet from which the binder has been removed is vacuum dried at 100° C.-150° C.

6. The recovery method according to any one of claims 1 to 5, wherein The solvent in the drying process of the positive electrode sheet from which the binder has been removed is collected, and the collected solvent is returned to the high-temperature soaking process as a solvent.

7. The recovery method according to any one of claims 1 to 6, wherein The elution and de-powdering process includes spraying the dried positive electrode sheet with water.

8. The recovery method according to any one of claims 1 to 7, wherein The process of drying the slurry comprises: Performing filter pressing on the slurry to obtain a filter cake and a filtrate; The filter cake is vacuum dried to recover the positive electrode active material.

9. The recovery method according to any one of claims 1 to 8, wherein The filtrate is returned to the elution and de-powdering process to be used for spraying the dried positive electrode sheets.

10. The recovery method according to any one of claims 1 to 9, wherein The recycling method further comprises the steps of crushing and demagnetizing the recovered positive electrode active material.

11. A device for recovering positive electrode active materials, wherein: The recovery device comprises: A soaking unit, comprising a soaking container for soaking the positive electrode sheet and a heating device for heating the soaking container; a first drying unit, disposed downstream of the soaking unit and configured to dry the positive electrode sheet from which the binder has been removed; an elution unit, disposed downstream of the first drying unit, for eluting and removing powder from the dried positive electrode sheet to obtain a slurry; The second drying unit is provided downstream of the elution unit and is used to dry the slurry to recover the positive electrode active material.

12. The recovery device according to claim 11, wherein: The immersion container has a gas inlet, and the immersion unit further includes a gas supply device, which is connected to the gas inlet and is used to supply gas to the immersion container. The gas supply device is a nitrogen supply device or an inert gas supply device.

13. The recovery device according to claim 11 or 12, wherein: The first drying unit is a first vacuum drying unit. The first drying unit further includes a steam condensation device. The steam condensation device is connected to the immersion container and is used to return the collected condensate to the immersion container for recycling.

14. The recovery device according to any one of claims 11 to 13, wherein: The elution unit includes a high-pressure spraying device, which is used to spray the dried positive electrode sheet.

15. The recovery device according to any one of claims 11 to 14, wherein: The second drying unit comprises: filter press equipment; The vacuum drying device is arranged downstream of the filter press device and is used for drying the filter cake of the filter press device.

16. The recovery device according to claim 15, wherein: The filter press equipment includes a filtrate collector, which is connected to the elution unit and is used to return the collected filtrate to the elution unit for elution and de-powdering of the positive electrode sheet.

17. The recovery device according to any one of claims 11 to 16, wherein: The recovery device further includes a crushing device and a demagnetizing device sequentially arranged downstream of the second drying unit.

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