Method for recycling active metals of lithium secondary batteries

Abstract

A method for recovering active metals of a lithium secondary battery according to an exemplary embodiment can include preparing a primary cathode active material mixture including a lithium complex oxide and a binder, removing the binder from the primary cathode active material mixture through heat treatment in a fluidized bed reactor to form a cathode active material mixture, and recovering a lithium precursor from the cathode active material mixture. Accordingly, active metals of a lithium secondary battery can be recovered with high purity and high efficiency.

Description

[0001] Cross-reference to related applications

[0002] This application is a divisional application of Chinese Patent Application No. 202180018831X, filed on March 4, 2021, entitled "Method for Recycling Active Metals from Lithium Secondary Batteries". This application claims priority to KR10-2020-0028136 (March 6, 2020). Technical Field

[0003] This invention relates to a method for recovering active metals from lithium secondary batteries. More specifically, this invention relates to a method for recovering active metals from a mixture of positive electrode active materials obtained from lithium secondary batteries. Background Technology

[0004] With the development of information and display technologies, rechargeable and dischargeable secondary batteries have been widely used in mobile electronic devices such as portable cameras, mobile phones, and laptops. Secondary batteries include, for example, lithium-ion batteries, nickel-cadmium batteries, and nickel-metal hydride batteries. Lithium-ion batteries are being actively developed and applied due to their high operating voltage and energy density per unit weight, high charge rate, and compact size.

[0005] A lithium secondary battery may include an electrode assembly and an electrolyte immersing the electrode assembly, the electrode assembly including a positive electrode, a negative electrode, and a separator layer (separator). The lithium secondary battery may further include a housing having, for example, a pouch shape.

[0006] Lithium metal oxides can be used as positive electrode active materials in lithium secondary batteries. Lithium metal oxides may further contain transition metals, such as nickel, cobalt, and manganese.

[0007] Lithium metal oxides, which are positive electrode active materials, can be prepared by reacting lithium precursors with nickel-cobalt-manganese (NCM) precursors containing nickel, cobalt, and manganese.

[0008] Because the aforementioned high-cost metals are used in cathode active materials, the cost of manufacturing cathode materials is prohibitively high. Furthermore, due to recent concerns about environmental protection, methods for recycling cathode active materials are being researched. Recycling cathode active materials requires the efficient and high-purity production of lithium precursors from spent cathode materials.

[0009] For example, Korean Patent Application No. 2015-0002963 discloses a method for recovering lithium using a wet process. However, lithium is recovered from waste liquid remaining after the extraction of cobalt, nickel, etc., through wet extraction, resulting in excessively low recovery rates and the potential generation of a large number of impurities from the waste liquid. Summary of the Invention

[0010] [Technical Objectives]

[0011] According to one aspect of the present invention, a method for recovering active metals from lithium secondary batteries with high efficiency and high yield is provided.

[0012] [Technical means]

[0013] In a method for recovering active metals from lithium-ion secondary batteries, a primary cathode active material mixture comprising lithium composite oxide and a binder can be prepared. The binder can be removed from the primary cathode active material mixture by heat treatment in a fluidized bed reactor to form the cathode active material mixture. Lithium precursors can be recovered from the cathode active material mixture.

[0014] In some embodiments, preparing a primary positive electrode active material mixture may include removing elements of the current collector from the positive electrode, which includes a positive electrode current collector and a layer of positive electrode active material, through physical pretreatment.

[0015] In some implementations, forming a mixture of positive electrode active materials may include injecting a non-reactive fluidizing gas into a fluidized bed reactor.

[0016] In some embodiments, the non-reactive fluidizing gas may include at least one selected from helium (He), nitrogen (N2), neon (Ne), argon (Ar), krypton (Kr), and xenon (Xe).

[0017] In some implementations, the heat treatment can be carried out in a temperature range of 100°C to 550°C.

[0018] In some implementations, the binder can be decomposed by heat treatment, and the temperature rise within the fluidized bed reactor caused by the decomposition of the binder can be less than 15°C.

[0019] In some implementations, the primary cathode active material mixture may further include a carbon-based conductive material, and the conductive material may also be removed by heat treatment in a fluidized bed reactor.

[0020] In some embodiments, recovering lithium precursors may include reducing a mixture of positive electrode active materials to form an active metal precursor mixture comprising lithium precursors and transition metal precursors, and collecting lithium precursors from the active metal precursor mixture.

[0021] In some implementations, the reduction process can be carried out in a temperature range of 300°C to 700°C.

[0022] In some implementations, the reduction process can be carried out in a fluidized bed reactor used to form a mixture of positive electrode active materials.

[0023] In some implementations, collecting lithium precursors may include washing the active metal precursor mixture with water.

[0024] [Effects of the Invention]

[0025] In the method for recovering active metals from lithium secondary batteries according to the above exemplary embodiments, the binder contained in the primary positive electrode active material mixture can be removed by heat treatment in a fluidized bed reactor, and side reactions caused by the heat of decomposition generated when the binder decomposes (e.g., particle agglomeration due to excessive reduction of active metals, etc.) can be minimized.

[0026] In the method for recovering active metals from lithium secondary batteries according to the above exemplary embodiment, the reduced positive electrode active material mixture in slurry form can be easily recovered. Therefore, the recovery efficiency of the active metal recovery process from lithium secondary batteries can be improved. Attached Figure Description

[0027] Figure 1 and Figure 2 This is a schematic flowchart describing a method for recovering active metals from lithium secondary batteries according to an exemplary embodiment. Detailed Implementation

[0028] An embodiment of the present invention provides a method for recovering lithium precursors, wherein a primary cathode active material mixture comprising lithium composite oxide and binder is prepared, the binder is removed from the primary cathode active material mixture by heat treatment in a fluidized bed reactor to form a cathode active material mixture, and the lithium precursor is recovered from the cathode active material mixture.

[0029] In the following, embodiments of the invention will be described in detail with reference to the accompanying drawings. However, these embodiments are provided by way of example, and the invention is not limited to the specific embodiments described herein.

[0030] As used herein, the term "precursor" is used in general to refer to a compound that contains a specific metal to provide a specific metal contained in an electrode active material.

[0031] Figure 1 and Figure 2 This is a schematic flowchart for describing a method for recycling lithium precursors from lithium secondary batteries according to an exemplary embodiment.

[0032] Reference Figure 1 A primary positive electrode active material mixture comprising lithium composite oxide and binder can be prepared (e.g., in step S10).

[0033] In an exemplary embodiment, a primary positive electrode active material mixture comprising lithium composite oxide and binder can be prepared from a lithium secondary battery.

[0034] A lithium secondary battery may include an electrode assembly including a positive electrode, a negative electrode, and a separator layer interposed between the positive electrode and the negative electrode. The positive electrode and the negative electrode may respectively include a positive electrode active material layer coated on a positive electrode current collector and a negative electrode active material layer coated on a negative electrode current collector.

[0035] For example, the positive electrode active material contained in the positive electrode active material layer may include a lithium composite oxide containing lithium and a transition metal.

[0036] In some embodiments, the lithium composite oxide may include a compound represented by the following Chemical Formula 1.

[0037] [Chemical Formula 1]

[0038] Li x M1 a M2 b M3 c O y

[0039] In Chemical Formula 1, M1, M2 and M3 may include at least one element selected from Ni, Co, Mn, Na, Mg, Ca, Ti, V, Cr, Cu, Zn, Ge, Sr, Ag, Ba, Zr, Nb, Mo, Al, Ga and B. In Chemical Formula 1, 0<x≤1.1, 2≤y≤2.02, 0<a<1, 0<b<1, 0<c<1, and 0<a+b+c≤1.

[0040] In some embodiments, the positive electrode active material may be an NCM-based lithium oxide including nickel, cobalt and manganese. The NCM-based lithium oxide as the lithium composite oxide may be prepared by causing a lithium precursor and an NCM precursor (e.g., an NCM oxide) to react with each other through a coprecipitation reaction.

[0041] However, the embodiments of the present disclosure may be generally applied not only to positive electrode materials including the lithium composite oxide, but also to lithium-containing positive electrode materials.

[0042] For example, the positive electrode may be separated from the lithium secondary battery. The positive electrode may include a positive electrode current collector (e.g., aluminum (Al)) and the positive electrode active material layer as described above, and the positive electrode active material layer may include a conductive material and a binder as well as the positive electrode active material as described above.

[0043] In some exemplary embodiments, the positive electrode active material mixture may further include a carbon-based conductive material and a binder in addition to the lithium composite oxide.

[0044] The carbon-based conductive material may include, for example, carbon-based materials such as graphite, carbon black, graphene, carbon nanotubes, and the like.

[0045] Adhesives may include resin materials such as polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinylidene fluoride (PVDF), polyacrylonitrile, polymethyl methacrylate, etc.

[0046] A primary cathode active material mixture can be prepared from the recovered cathode. In some embodiments, the primary cathode active material mixture can be prepared into powder form, and the elements of the current collector can be removed from the cathode from the powder form of the primary cathode active material mixture by physical methods. For example, non-limiting examples of physical methods may include crushing, pulverizing, desorption, stripping, etc.

[0047] As described above, the primary cathode active material mixture may include lithium composite oxide powder and binder powder. For example, the primary cathode active material mixture may include NCM-based lithium oxide powder (e.g., Li(NCM)O2) and binder powder.

[0048] In some embodiments, the recovered positive electrode can be heat-treated before pulverization. Therefore, the desorption of the positive electrode current collector can be promoted during pulverization, and at least partially removed from the binder and conductive materials. For example, the heat treatment temperature can be in the range of about 100°C to 500°C, preferably from about 350°C to 450°C.

[0049] In some embodiments, a primary cathode active material mixture can be obtained after immersing the recovered cathode in an organic solvent. For example, the recovered cathode can be immersed in an organic solvent to separate and remove the cathode current collector, and the primary cathode active material mixture containing lithium composite oxide and binder can be selectively extracted by centrifugation.

[0050] Through the above process, positive electrode current collector components such as aluminum can be essentially completely separated and removed, and a primary positive electrode active material mixture with reduced carbon-based component content derived from the binder can be obtained.

[0051] In this case, in addition to particles derived from lithium composite oxides and particles derived from binders, the primary cathode active material mixture may further include particles derived from carbon-based conductive materials.

[0052] Reference Figure 1 The positive electrode active material mixture can be formed by removing the binder from the primary active material mixture through heat treatment in a fluidized bed reactor (e.g., in step S20).

[0053] For example, a primary positive electrode active material mixture 50 containing lithium composite oxide 60 and binder 70 can be injected into a fluidized bed reactor 100.

[0054] For example, fluidized bed reactor 100 can refer to a reactor that fluidizes the primary positive electrode active material mixture 50 by passing a fluid (gas or liquid) through an injected primary positive electrode active material mixture 50. For example, the fluid can be a non-reactive fluidizing gas, which will be described below.

[0055] In this case, the binder 70 can be removed while the primary positive electrode active material mixture 50 in the fluidized bed reactor 100 is in a fluidized state, so that the heat of decomposition generated during the removal of the binder 70 can be uniformly dispersed throughout the primary positive electrode active material mixture 50.

[0056] Therefore, the temperature rise in the reactor caused by the heat of decomposition can be minimized. Therefore, particle aggregation caused by side reactions of the primary positive electrode active material mixture 50 caused by the heat of decomposition (e.g., excessive reduction reaction due to the heat of decomposition of the binder) can be minimized.

[0057] In some exemplary embodiments, a non-reactive fluidizing gas may be injected into the fluidized bed reactor 100 to form a positive electrode active material.

[0058] For example, the primary positive electrode active material mixture 50 can be injected into the fluidized bed reactor 100 through the upper inlet 108a located at the top of the fluidized bed reactor 100.

[0059] For example, non-reactive fluidizing gas can be injected into the reactor body 110 of the fluidized bed reactor 100 through the gas inlet 104 located at the bottom of the fluidized bed reactor 100.

[0060] The non-reactive fluidizing gas may include at least one selected from helium (He), nitrogen (N2), neon (Ne), argon (Ar), krypton (Kr), and xenon (Xe).

[0061] Since non-reactive fluidizing gas can be injected into the fluidized bed reactor 100, the primary positive electrode active material mixture 50 injected into the fluidized bed reactor 100 can be fluidized.

[0062] For example, the fluidized bed reactor 100 may include an expansion tube 120 at its upper part, which has a diameter larger than that of the reactor body 110.

[0063] The expansion tube 120 can have a larger diameter than the reactor body 110, allowing for a reduction in the flow rate of the non-reactive fluidizing gas injected from the lower part of the fluidized bed reactor 100 to move upwards. Therefore, it can effectively prevent a decrease in recovery rate due to the increased injection rate of the non-reactive fluidizing gas as the primary positive electrode active material mixture 50 flows out of the reactor body 110.

[0064] For example, the primary cathode active material mixture 50 can be fluidized after injection into the fluidized bed reactor 100, and then the binder 70 can be removed by heat treatment. In this case, the binder 70 can be removed from the primary cathode active material mixture to form the cathode active material mixture 90. The cathode active material mixture 90 may include particles derived from the lithium composite oxide 60, and may substantially exclude particles derived from the binder 70.

[0065] For example, the fluidized bed reactor 100 may include a heating unit capable of controlling the internal temperature of the reactor body 110.

[0066] For example, the heat treatment temperature can be in the range of about 100°C to 550°C, more preferably from about 400°C to 500°C. Within the above temperature range, the decomposition of the binder can be initiated, while side reactions caused by the increase in temperature inside the reactor body 110 are minimized.

[0067] For example, if the heat treatment temperature is below the aforementioned range, undecomposed binders may remain. If the heat treatment temperature exceeds the aforementioned range, lithium carbonate (Li₂CO₃) may form due to excessive reduction reaction, potentially leading to particle agglomeration. Therefore, the recovery efficiency of lithium precursors may be reduced.

[0068] In some exemplary embodiments, the binder 70 can be decomposed by heat treatment, and the temperature rise in the fluidized bed reactor 100 due to the decomposition of the binder 70 can be less than about 15°C, preferably less than about 10°C. The lower limit of the temperature rise can be very small, but can be more than about 1°C.

[0069] In this case, the decomposition of binder 70 can take place inside the fluidized bed reactor 100, so that the heat of decomposition of binder 70 can be dispersed throughout the fluidized primary positive electrode active material mixture 50 to minimize the temperature rise caused by the heat of decomposition.

[0070] Therefore, side reactions of the primary cathode active material mixture 50 caused by the decomposition of binder 70 (e.g., excessive reduction of lithium composite oxide by carbon) can be minimized, thereby improving the process efficiency of lithium precursor recovery as described below.

[0071] In some exemplary embodiments, the primary cathode active material mixture 50 may further include a carbon-based conductive material 80, and the conductive material 80 may also be removed by heat treatment in the fluidized bed reactor 100. Therefore, the active metal recovery efficiency of the lithium secondary battery can be further improved.

[0072] In some exemplary embodiments, the average diameter (D50, e.g., based on cumulative volume distribution) of the formed positive electrode active material mixture can be in the range of about 1 μm to 100 μm. Within this range, the contact area between the reducing gas and the positive electrode active material mixture can be increased in the reduction process described below, and the collection efficiency of the lithium precursor can be improved.

[0073] For example, when the positive electrode active material mixture 90 is formed in a non-fluidized reactor, during the removal of binder 70 from the primary positive electrode active material 50, side reactions (e.g., excessive reduction of carbon) may occur due to the heat of decomposition of binder 70, thus causing particle aggregation contained in the positive electrode active material mixture 90.

[0074] In this case, the diameter of the particles contained in the positive electrode active material mixture 90 can increase to more than 1 cm. Therefore, fluidization of the positive electrode active material mixture 90 for carrying out the reduction reaction described below may not be possible, and thus the process efficiency of the reduction reaction may be reduced.

[0075] In some exemplary embodiments, the particle size distribution of the positive electrode active material mixture 90 can be greater than about 0 μm and less than about 500 μm.

[0076] Within the aforementioned particle size distribution range, the positive electrode active material mixture can be completely and uniformly reduced. Therefore, the heat generated during the reduction reaction can be uniformly dispersed throughout the entire positive electrode active material mixture, and side reactions caused by the heat generated during the reduction reaction can be minimized. Thus, the yield of lithium precursors can be further improved.

[0077] For example, the positive electrode active material mixture 90 can be collected through the outlet 108b of the fluidized bed reactor 100. The collected positive electrode active material mixture 90 can be injected into a lithium precursor recovery process described below.

[0078] In one embodiment, the positive electrode active material mixture 90 can be held inside the fluidized bed reactor 100, and a lithium precursor recovery process can be carried out inside the fluidized bed reactor 100 in which the positive electrode active material mixture 90 is formed.

[0079] Reference Figure 1 and Figure 2Lithium precursors can be collected from the positive electrode active material mixture 90 (e.g., in step S30).

[0080] In this case, the positive electrode active material mixture 90 formed in the fluidized bed reactor 100 can have a uniform particle distribution, thereby enabling a reduction process for collecting lithium precursors and increasing the contact area with the reducing gas.

[0081] Furthermore, the binder 70, which has a high heat of decomposition, can be removed from the positive electrode active material mixture 90, thereby minimizing the temperature rise inside the reduction reactor 200 caused by the heat generated during the decomposition of the binder 70 in the lithium precursor recovery process. Therefore, side reactions in the positive electrode active material mixture 90 caused by the heat of decomposition of the binder 70 (e.g., over-reduction of the positive electrode active material) can be minimized. Thus, the collection efficiency of the lithium precursor can be improved.

[0082] Lithium precursors may include lithium hydroxide (LiOH), lithium oxide (Li2O), or lithium carbonate (Li2CO3). From the perspectives of charge / discharge characteristics, lifetime characteristics, and high-temperature stability, lithium precursors may include lithium hydroxide.

[0083] In one implementation, lithium carbonate may be essentially excluded because it causes a deposition reaction on the membrane layer, thereby reducing lifetime stability.

[0084] In some embodiments, during the recovery of lithium precursors, the positive electrode active material mixture 90 can be reduced to form an active metal precursor mixture including lithium precursors and transition metal precursors (e.g., in step S32).

[0085] For example, a mixture of positive electrode active materials (e.g., positive electrode active materials) can be reduced with hydrogen in reduction reactor 200 to form an active metal precursor mixture. Hydrogen can be injected into reactor body 210 via gas injector 204 located at the bottom of reduction reactor 200.

[0086] The hydrogen reduction reaction can be carried out at a temperature of about 300°C to 700°C, preferably 400°C to 550°C. In this case, the reduction reactor 200 may include a separate heating unit for increasing the internal temperature. Within the above temperature range, the yield of the active precursor mixture produced by the positive electrode active material mixture 90 can be increased.

[0087] Furthermore, the positive electrode active material mixture 90 can be substantially free of binders, thereby preventing the internal temperature of the reduction reactor 200 from rising due to the heat of decomposition of the binders. Therefore, over-reduction of the positive electrode active material mixture 90 due to the heat of decomposition can be prevented, thus minimizing particle aggregation caused by the bonding between nickel (Ni) and cobalt (Co) contained in the positive electrode active material mixture 90. Additionally, the slurry-like active metal precursor mixture formed by reducing the positive electrode active material mixture 90 can be collected more easily.

[0088] The additional temperature increase in the reduction reactor 200 caused by the hydrogen reduction reaction can be about 30°C, preferably below about 25°C. There is no particular limitation on the lower limit of the additional temperature increase, but it can be above about 1°C.

[0089] In some exemplary embodiments, the reduction reactor 200 may be a fluidized bed reactor. In this case, hydrogen and non-reactive fluidizing gas may be injected together through a gas inlet located at the bottom of the fluidized bed reactor.

[0090] For example, the expansion tube 220 can be located at the top of the reduction reactor 200. The flow rate of the non-reactive fluidizing gas injected from the bottom of the reduction reactor 200 can be reduced by the expansion tube 220, so that leakage of the positive electrode active material mixture 90 can be effectively prevented during the fluidization process.

[0091] The active precursor mixture may include primary lithium precursors and primary transition metal precursors, which may be products of the hydrogen reduction reaction of lithium composite oxides contained in the positive electrode active material mixture.

[0092] Primary lithium precursors may include lithium hydroxide, lithium oxide, and / or lithium carbonate. In an exemplary embodiment, the primary lithium precursor can be obtained via a hydrogen reduction reaction, thereby reducing the mixed content of lithium carbonate.

[0093] Primary transition metal precursors can include Ni, Co, NiO, CoO, MnO, etc.

[0094] For example, the active precursor mixture can be formed by the reduction of a positive electrode active material mixture 90 that is substantially free of binders, and therefore, it can substantially exclude nickel (Ni)-cobalt (Co) bonds formed by excessive reduction of the positive electrode active material mixture 90. Therefore, the active precursor mixture in slurry form can be more easily recovered.

[0095] In some exemplary embodiments, the reduction reaction can be carried out inside the fluidized bed reactor 100 that performs the process of forming the positive electrode active material mixture. In this case, the formation and reduction reactions of the positive electrode active material mixture can be carried out in the same reactor, thereby preventing partial loss of the positive electrode active material mixture during the transfer of the formed mixture. Therefore, the recovery efficiency of the lithium precursor can be further improved.

[0096] In some exemplary embodiments, the positive electrode active material mixture 90 can be injected into the reduction reactor 200 through the upper inlet 208a located at the top of the reduction reactor 200. The active metal precursor mixture can be collected through the outlet 208b located at the bottom of the reduction reactor 200. The collected active metal precursor mixture can be injected into the lithium precursor collection process described below.

[0097] For example, water and non-reactive fluidizing gas can be injected into the reduction reactor 200 before collecting the active metal precursor mixture to form it into a slurry state. In this case, the aggregation of the active metal precursor mixture caused by the reduction reaction can be loosened. Therefore, the active metal precursor mixture in a slurry state can be collected more easily.

[0098] For example, water can be injected into the reduction reactor 200 through the upper inlet 208a, and non-reactive fluidizing gas can be injected into the reduction reactor 200 through the gas inlet 204 located at the bottom of the reduction reactor 200.

[0099] For example, the active metal precursor mixture in slurry form can be collected through outlet 208b located at the bottom of reduction reactor 200.

[0100] In one embodiment, the resulting active metal precursor mixture may not be collected separately from the reduction reactor 200, but may be located within the reduction reactor 200, and the lithium precursor collection process described below may be carried out within the reduction reactor 200.

[0101] In some exemplary embodiments, lithium precursors can be collected from the active metal precursor mixture (e.g., in step S34).

[0102] For example, lithium precursors can be collected by reacting a mixture of active metal precursors formed by the hydrogen reduction reaction as described above with a leachate.

[0103] For example, a mixture of active metal precursors can react with a leachate to form a solution containing dissolved lithium precursors and a precipitate containing primary transition metal precursors.

[0104] For example, lithium oxide reacts with the leachate to form lithium hydroxide, which can be dissolved in the leachate.

[0105] For example, lithium carbonate may have poor solubility in the leachate. Therefore, lithium carbonate can precipitate and can be removed from the primary precursor mixture.

[0106] In some embodiments, the leachate may include water. In this case, the active metal precursor mixture can be washed with water. Through the washing process, the active metal precursor mixture and water can react to form a lithium precursor, wherein lithium hydroxide is dissolved in the water.

[0107] In some exemplary embodiments, the leachate may further include dimethyl carbonate or diethyl carbonate.

[0108] For example, dimethyl carbonate or diethyl carbonate can promote the reaction between primary lithium precursors and water. Therefore, the separation efficiency of lithium precursors can be improved.

[0109] In some implementations, the precipitate may include a slurry comprising a primary lithium precursor mixture.

[0110] For example, primary transition metal precursors that may not dissolve in the leaching solution can be dispersed in the leaching solution to form a slurry. Therefore, lithium precursors can be collected by separating the slurry from the solution containing the dissolved lithium precursors.

[0111] In one implementation, the precipitated primary transition metal precursor can be collected to form a transition metal precursor. For example, the primary transition metal precursor can react with an acidic solution to form a transition metal precursor.

[0112] In one embodiment, sulfuric acid can be used as an acidic solution. In this case, the transition metal precursor may include a transition metal sulfate. For example, transition metal sulfates may include NiSO4, MnSO4, CoSO4, etc.

[0113] The reaction of the primary precursor mixture and the leachate can be carried out in a reduction reactor 200 in which a hydrogen reduction process is performed, or in a fluidized bed reactor 100 in which a positive electrode active material mixture formation process is performed. In this case, after the process of forming the positive electrode active material mixture, the process of forming the primary lithium precursor, or the process of forming the precursor mixture, a collection step for each product is not required, thereby minimizing the reduction in lithium precursor recovery rate caused by the transfer of each product.

[0114] Preferred embodiments are presented below to describe the invention in more detail. However, the following examples are merely illustrative, and those skilled in the art will clearly understand that various changes and modifications can be made within the scope and spirit of the invention. Such changes and modifications are suitably included in the appended claims.

[0115] Example 1

[0116] The 1 kg of positive electrode material separated from waste lithium secondary batteries is cut into small units and then ground to form a primary positive electrode active material mixture containing Li-Ni-Co-Mn oxides and binders (polyvinylidene fluoride, PVDF).

[0117] 0.2 kg of a primary positive electrode active material mixture was injected into a fluidized bed reactor. N2 gas was injected into the lower part of the fluidized bed reactor to fluidize the primary positive electrode active material mixture, and the internal temperature of the fluidized bed reactor was raised to 450°C to thermally decompose the binder contained in the primary positive electrode active material mixture, thereby preparing the positive electrode active material mixture.

[0118] A mixture of positive electrode active materials is fluidized in a fluidized bed reactor and reacted with hydrogen to form a mixture of active metal precursors including lithium hydroxide. The internal temperature of the fluidized bed reactor is maintained at 450°C.

[0119] Water and nitrogen are added to the active metal precursor to form a slurry. The slurry is collected and washed with water to obtain an aqueous lithium precursor solution.

[0120] Comparative Example 1

[0121] The lithium precursor was obtained by the same method as in Example 1, except that a non-fluidized reactor was used for the thermal decomposition process of the binder used to prepare the positive electrode active material mixture.

[0122] Comparative Example 2

[0123] The lithium precursor was obtained using the same method as in Example 1, except that the thermal decomposition process of the binder was not performed when preparing the positive electrode active material mixture.

[0124] For each of Example 1 and Comparative Examples 1 and 2, the changes in internal temperature (°C) in the fluidized bed reactor, the average diameter of the positive electrode active material mixture particles, the particle size distribution, the generation of by-products, and the binder removal rate measured during the preparation of the positive electrode active material mixture are shown in Table 1.

[0125] In addition, the maximum temperature change in the reactor during the reduction process and the recovery rate of the lithium precursor after washing with water were measured and are shown in Table 1.

[0126] [Table 1]

[0127]

[0128] Referring to Table 1, in Example 1, an improved lithium precursor recovery rate was obtained by performing a fluidized bed thermal decomposition process to remove the binder contained in the primary cathode active material mixture.

[0129] However, in Comparative Example 1, which involved a non-fluidized thermal decomposition process, the positive electrode active material mixture aggregated with each other due to side reactions (e.g., over-reduction) in the thermal decomposition process. Therefore, the positive electrode active material mixture was difficult to fluidize, thereby reducing the efficiency of the hydrogen reduction process.

[0130] Furthermore, in Comparative Example 2, which did not undergo a thermal decomposition process, the metal active material mixture aggregated due to side reactions caused by the heat of decomposition from the binder during the hydrogen reduction process (e.g., over-reduction of the cathode active material mixture). Therefore, the over-reduced metal active material mixture was difficult to convert into a slurry state, thereby reducing the recovery rate of the lithium precursor.

Claims

1. A method for recovering active metals from lithium secondary batteries, comprising: A mixture of primary positive electrode active materials comprising lithium composite oxide and binder was prepared; The positive electrode active material mixture is formed by removing the binder from the primary positive electrode active material mixture through heat treatment in a fluidized bed reactor; as well as The lithium precursor was recovered from the mixture of positive electrode active materials. The recovery of the lithium precursor includes: By reducing the mixture of positive electrode active materials, an active metal precursor mixture comprising lithium precursor and transition metal precursor is formed; and The lithium precursor is collected from the active metal precursor mixture; The formation of the positive electrode active material mixture includes injecting a non-reactive fluidizing gas into the fluidized bed reactor.

2. The method for recovering active metals from lithium secondary batteries according to claim 1, wherein, The preparation of the primary positive electrode active material mixture includes removing the elements of the current collector from the positive electrode, which includes the positive electrode current collector and the positive electrode active material layer, through physical pretreatment.

3. The method for recovering active metals from lithium secondary batteries according to claim 1, wherein, The non-reactive fluidizing gas includes at least one selected from helium (He), nitrogen (N2), neon (Ne), argon (Ar), krypton (Kr), and xenon (Xe).

4. The method for recovering active metals from lithium secondary batteries according to claim 1, wherein, The heat treatment is carried out in a temperature range of 100°C to 550°C.

5. The method for recovering active metals from lithium secondary batteries according to claim 4, wherein, The adhesive decomposes through the heat treatment, and the temperature rise within the fluidized bed reactor caused by the decomposition of the adhesive is less than 15°C.

6. The method for recovering active metals from lithium secondary batteries according to claim 1, wherein, The primary positive electrode active material mixture further includes a carbon-based conductive material, and The conductive material is also removed by heat treatment in the fluidized bed reactor.

7. The method for recovering active metals from lithium secondary batteries according to claim 1, wherein, The reduction process is carried out in a temperature range of 300°C to 700°C.

8. The method for recovering active metals from lithium secondary batteries according to claim 1, wherein, The reduction process is carried out in a fluidized bed reactor used to form the positive electrode active material mixture.

9. The method for recovering active metals from lithium secondary batteries according to claim 1, wherein, Collecting the lithium precursor involves washing the active metal precursor mixture with water.

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