Method for recovering active metal of lithium secondary battery

Abstract

A method for recovering an active metal of a lithium secondary battery according to an exemplary embodiment may include preparing a primary positive electrode active material mixture including a lithium composite oxide and a binder, removing the binder from the primary positive electrode active material mixture by heat treatment in the fluidized bed reactor to form a positive electrode active material mixture, and recovering the lithium precursor from the positive electrode active material mixture. Therefore, the active metal of the 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 invention patent application number 202180018831X, filed on March 4, 2021, entitled “Method for Recycling Active Metals from Lithium Secondary Batteries.” This application claims priority from patent application KR10-2020-0028136 (March 6, 2020). Technical Field

[0003] The present invention relates to a method for recovering active metals from a lithium secondary battery, and more particularly, to a method for recovering active metals from a positive electrode active material mixture obtained from a lithium secondary battery. Background Art

[0004] With the development of information technology and display technology, rechargeable and rechargeable secondary batteries have become widely used in mobile electronic devices such as camcorders, mobile phones, and laptop computers. Secondary batteries include, for example, lithium secondary batteries, nickel-cadmium batteries, and nickel-metal hydride batteries. Lithium secondary batteries are being actively developed and applied due to their high operating voltage and energy density per unit weight, high charging rate, and compact size.

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

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

[0007] Lithium metal oxide as a positive electrode active material can be prepared by reacting a lithium precursor with a nickel-cobalt-manganese (NCM) precursor containing nickel, cobalt, and manganese.

[0008] Because these high-cost precious metals are used in positive electrode active materials, the production costs of these materials are prohibitively high. Furthermore, with recent attention paid to environmental protection, research is underway to recover these materials. Recovering these materials requires efficient and high-purity lithium precursor production from spent positive electrodes.

[0009] For example, Korean Patent Application No. 2015-0002963 discloses a method for recovering lithium using a wet process. However, lithium is recovered by wet extraction from waste liquid remaining after extracting cobalt, nickel, etc., so the recovery rate is excessively reduced and a large amount of impurities may be generated in the waste liquid. Summary of the Invention

[0010] [Technical Goals]

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

[0012] [Technical means]

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

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

[0015] In some embodiments, forming the positive active material mixture may include injecting a non-reactive fluidizing gas into the fluidized bed reactor.

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

[0017] In some embodiments, the heat treatment may be performed at a temperature ranging from 100°C to 550°C.

[0018] In some embodiments, the binder may be decomposed by heat treatment, and the temperature rise in the fluidized bed reactor caused by the decomposition of the binder may be 15° C. or less.

[0019] In some embodiments, the primary positive 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 the lithium precursor may include forming an active metal precursor mixture including a lithium precursor and a transition metal precursor by performing a reduction treatment on the positive electrode active material mixture, and collecting the lithium precursor from the active metal precursor mixture.

[0021] In some embodiments, the reduction treatment may be performed at a temperature ranging from 300°C to 700°C.

[0022] In some embodiments, the reduction treatment may be performed in a fluidized bed reactor used to form the positive active material mixture.

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

[0024] [Effects of the Invention]

[0025] In the method for recovering active metals of lithium secondary batteries according to the above exemplary embodiment, 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 decomposition heat generated when the binder decomposes (for example, particle agglomeration due to excessive reduction of the active metal, etc.) can be minimized.

[0026] In the method for recovering active metals from a lithium secondary battery according to the exemplary embodiment, the reduced positive active material mixture in a slurry state can be easily recovered, thereby improving the recovery efficiency of the active metal recovery process for lithium secondary batteries. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 and Figure 2 is a schematic flow chart for describing a method of recovering active metals of a lithium secondary battery according to an exemplary embodiment. DETAILED DESCRIPTION

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

[0029] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. However, these embodiments are provided as examples, and the present invention is not limited to the specific embodiments described herein.

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

[0031] Figure 1 and Figure 2 is a schematic flowchart for describing a method of recycling a lithium precursor of a lithium secondary battery according to an exemplary embodiment.

[0032] Reference Figure 1 , a primary positive electrode active material mixture including a lithium composite oxide and a binder may be prepared (eg, in step S10 ).

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

[0034] A lithium secondary battery may include an electrode assembly, which includes 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 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, respectively.

[0035] For example, the positive electrode active material included 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 Chemical Formula 1 below.

[0037] [Chemical Formula 1]

[0038] Li ,

[0045] ,

[0044] M1 a M2 b M3 c O y <00,00091>

[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 reacting a lithium precursor and an NCM precursor (e.g., an NCM oxide) with each other through a coprecipitation reaction.

[0041] However, the embodiments of the present invention can be not only generally applied to the positive electrode material including a lithium composite oxide, but also applied to a lithium-containing positive electrode material.

[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, an adhesive, and the positive electrode active material as described above.

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

[0044] The carbon-based conductive material may include, for example, a carbon-based material such as graphite, carbon black, graphene, carbon nanotubes, etc.

[0045] The binder may include a resin material such as polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinylidene fluoride (PVDF), polyacrylonitrile, polymethylmethacrylate, or the like.

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

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

[0048] In some embodiments, the recovered positive electrode can be heat-treated before pulverization. Thus, the pulverization process can facilitate the desorption of the positive electrode current collector and at least partially remove the binder and conductive material. 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, the primary positive electrode active material mixture can be obtained after the recovered positive electrode is immersed in an organic solvent. For example, the recovered positive electrode can be immersed in an organic solvent to separate and remove the positive electrode current collector, and the primary positive electrode active material mixture containing the lithium composite oxide and the binder can be selectively extracted by centrifugation.

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

[0051] In this case, the primary positive active material mixture may further include particles derived from a carbon-based conductive material in addition to the particles derived from the lithium composite oxide and the particles derived from the binder.

[0052] Reference Figure 1 , the positive active material mixture may be formed by removing the binder from the primary active material mixture by heat treatment in a fluidized bed reactor (eg, in step S20 ).

[0053] For example, the primary positive active material mixture 50 including the lithium composite oxide 60 and the binder 70 may be injected into the fluidized bed reactor 100 .

[0054] For example, the fluidized bed reactor 100 may refer to a reactor that fluidizes the primary cathode active material mixture 50 by passing a fluid (gas or liquid) through the injected primary cathode active material mixture 50. For example, the fluid may 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 active material mixture 50 in the fluidized bed reactor 100 is in a fluidized state, so that the decomposition heat generated during the removal of the binder 70 can be uniformly dispersed throughout the primary positive active material mixture 50 .

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

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

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

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

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

[0062] For example, the fluidized bed reactor 100 may include an expansion pipe 120 having a larger diameter than that of the reactor body 110 at an upper portion thereof.

[0063] The expansion tube 120 may have a larger diameter than the reactor body 110, so that the flow rate of the non-reactive fluidizing gas injected from the lower portion of the fluidized bed reactor 100 to move upward can be reduced. Therefore, it is possible to effectively prevent the recovery rate from being reduced due to an increase in the injection rate of the non-reactive fluidizing gas when the primary positive active material mixture 50 flows out of the reactor body 110.

[0064] For example, the primary positive active material mixture 50 may be fluidized after being injected into the fluidized bed reactor 100, and then the binder 70 may be removed by heat treatment. In this case, the binder 70 may be removed from the primary positive active material mixture to form the positive active material mixture 90. The positive 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 temperature inside the reactor body 110 .

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

[0067] For example, if the heat treatment temperature is lower than the above range, undecomposed binder may remain. If the heat treatment temperature exceeds the above range, lithium carbonate (Li2CO3) may be formed due to excessive reduction reaction and may cause agglomeration of particles. As a result, the recovery efficiency of the lithium precursor may be reduced.

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

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

[0070] Therefore, side reactions of the primary positive active material mixture 50 (eg, excessive reduction of lithium composite oxide by carbon) caused by decomposition of the binder 70 can be minimized, thereby improving the efficiency of a process for recovering a lithium precursor to be described below.

[0071] In some exemplary embodiments, the primary positive 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 may be further improved.

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

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

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

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

[0076] Within the above-mentioned 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 evenly dispersed throughout the positive electrode active material mixture, and the side reactions caused by the heat generated during the reduction reaction can be minimized. As a result, the yield of the lithium precursor can be further improved.

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

[0078] In one embodiment, the positive active material mixture 90 may be maintained inside the fluidized bed reactor 100 , and the lithium precursor recovery process may be performed inside the fluidized bed reactor 100 in which the positive active material mixture 90 is formed.

[0079] Reference Figure 1 and Figure 2, the lithium precursor may be collected from the positive electrode active material mixture 90 (eg, in step S30 ).

[0080] In this case, the positive active material mixture 90 formed in the fluidized bed reactor 100 may have uniform particle distribution, so that a reduction process for collecting a lithium precursor may be performed and a contact area with a reducing gas may be increased.

[0081] In addition, the binder 70 having a high decomposition heat can be removed from the positive electrode active material mixture 90, thereby minimizing the increase in temperature within the reduction reactor 200 due to the heat generated when the binder 70 decomposes during the lithium precursor recovery process. Therefore, side reactions of the positive electrode active material mixture 90 (e.g., excessive reduction of the positive electrode active material) caused by the decomposition heat of the binder 70 can be minimized. Consequently, the collection efficiency of the lithium precursor can be improved.

[0082] The lithium precursor may include lithium hydroxide (LiOH), lithium oxide (Li2O), or lithium carbonate (Li2CO3). From the perspectives of charge / discharge characteristics, life characteristics, high temperature stability, etc., the lithium precursor may include lithium hydroxide.

[0083] In one embodiment, lithium carbonate may be substantially excluded because lithium carbonate may cause a deposition reaction on the separator layer, thereby reducing lifetime stability.

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

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

[0086] The hydrogen reduction reaction may be performed at a temperature of approximately 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 generated from the positive active material mixture 90 may be increased.

[0087] In addition, the positive electrode active material mixture 90 may substantially not include a binder, thereby preventing the internal temperature of the reduction reactor 200 from increasing due to the decomposition heat of the binder. Therefore, excessive reduction of the positive electrode active material mixture 90 due to the decomposition heat can be prevented, thereby minimizing particle aggregation caused by bonding between nickel (Ni) and cobalt (Co) contained in the positive electrode active material mixture 90. In addition, the active metal precursor mixture in a slurry state formed by reducing the positive electrode active material mixture 90 can be more easily collected.

[0088] The additional increase in temperature in the reduction reactor 200 caused by the hydrogen reduction reaction may be about 30° C., preferably about 25° C. or less. The lower limit of the additional increase in temperature is not particularly limited, but may be about 1° C. or more.

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

[0090] For example, the expansion tube 220 may be located at the upper portion of the reduction reactor 200. The flow rate of the non-reactive fluidizing gas injected from the lower portion of the reduction reactor 200 may be reduced by the expansion tube 220, thereby effectively preventing leakage of the positive electrode active material mixture 90 during fluidization of the positive electrode active material mixture 90.

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

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

[0093] The primary transition metal precursor may include Ni, Co, NiO, CoO, MnO, and the like.

[0094] For example, the active precursor mixture may be formed by reducing the positive electrode active material mixture 90, which may substantially exclude the binder, and thus may substantially exclude nickel (Ni)-cobalt (Co) bonds formed by over-reduction of the positive electrode active material mixture 90. Therefore, the active precursor mixture in a slurry state may be more easily recovered.

[0095] In some exemplary embodiments, the reduction reaction can be performed inside the fluidized bed reactor 100 that performs the process of forming the positive electrode active material mixture. In this case, the formation of the positive electrode active material mixture and the reduction reaction can be performed in the same reactor, thereby preventing partial loss of the positive electrode active material mixture caused by the transfer process of the formed positive electrode active material 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 may be injected into the reduction reactor 200 through an upper inlet 208a located at an upper portion of the reduction reactor 200. The active metal precursor mixture may be collected through an outlet 208b located at a lower portion of the reduction reactor 200. The collected active metal precursor mixture may be injected into a lithium precursor collection process to be described below.

[0097] For example, water and a non-reactive fluidizing gas may be injected into the reduction reactor 200 before collecting the active metal precursor mixture to form the active metal precursor mixture into a slurry state. In this case, the aggregates 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 more easily collected.

[0098] For example, water may be injected into the reduction reactor 200 through the upper inlet 208 a of the reduction reactor 200 , and a non-reactive fluidizing gas may 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 a slurry state may be collected through the outlet 208 b located at the lower portion of the reduction reactor 200 .

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

[0101] In some exemplary embodiments, the lithium precursor may be collected from the active metal precursor mixture (eg, in step S34).

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

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

[0104] For example, lithium oxide reacts with the leachate to form lithium hydroxide, which is soluble in the leachate.

[0105] For example, lithium carbonate may be poorly soluble in the leachate solution. Thus, the lithium carbonate may precipitate and may be removed from the primary precursor mixture.

[0106] In some embodiments, the leachate may include water. In this case, the active metal precursor mixture may be washed with water. Through the washing process, the active metal precursor mixture and water may 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 the primary lithium precursor and water, thereby improving the separation efficiency of the lithium precursor.

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

[0110] For example, a primary transition metal precursor that may not be dissolved in the leachate may be dispersed in the leachate to form a slurry. Thus, the lithium precursor may be collected by separating the slurry from the solution in which the lithium precursor is dissolved.

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

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

[0113] The reaction of the primary precursor mixture and the leachate can be performed in the reduction reactor 200 in which the hydrogen reduction process is performed, or in the fluidized bed reactor 100 in which the positive electrode active material mixture forming 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 process for each product may not be required, thereby minimizing the reduction in the lithium precursor recovery rate caused during the transfer of each product.

[0114] Hereinafter, preferred embodiments are set forth to more particularly describe the present invention. However, the following examples are intended to illustrate the present invention only, and those skilled in the art will clearly understand that various changes and modifications may be made within the scope and spirit of the present invention. Such changes and modifications are appropriately included in the appended claims.

[0115] Example 1

[0116] 1 kg of positive electrode material separated from waste lithium secondary batteries was cut into small units and pulverized by grinding to form a primary positive electrode active material mixture containing Li-Ni-Co-Mn oxide and a binder (polyvinylidene fluoride, PVDF).

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

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

[0119] Water and nitrogen are added to the active metal precursor to form a slurry of the active metal precursor. The slurry of the active metal precursor is collected and washed with water to obtain a lithium precursor aqueous 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 for preparing the positive active material mixture.

[0122] Comparative Example 2

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

[0124] For each of Example 1 and Comparative Examples 1 and 2, the change in the internal temperature (°C) in the fluidized bed reactor measured during the preparation of the positive electrode active material mixture, 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 are shown in Table 1.

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

[0126] [Table 1]

[0127]

[0128] Referring to Table 1, in Example 1 in which the fluidized thermal decomposition process was performed to remove the binder contained in the primary positive active material mixture, an improved recovery rate of the lithium precursor was obtained.

[0129] However, in Comparative Example 1, which performed a non-fluidized thermal decomposition process, the cathode active material mixture aggregated due to side reactions (e.g., over-reduction) during the thermal decomposition process. Therefore, the cathode active material mixture was not easily fluidized, thereby reducing the efficiency of the hydrogen reduction process.

[0130] In addition, in Comparative Example 2, where the thermal decomposition process was not performed, the metal active material mixture aggregated due to side reactions (e.g., over-reduction of the positive electrode active material mixture) caused by the decomposition heat caused by the decomposition of the binder during the hydrogen reduction process. As a result, 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: preparing a primary positive electrode active material mixture comprising a lithium composite oxide and a binder; removing the binder from the primary positive active material mixture by heat treatment in a fluidized bed reactor to form a positive active material mixture; as well as recovering a lithium precursor from the positive electrode active material mixture, Wherein, recovering the lithium precursor comprises: forming an active metal precursor mixture including a lithium precursor and a transition metal precursor by performing a reduction treatment on the positive electrode active material mixture; and The lithium precursor is collected from the active metal precursor mixture.

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

3. The method for recovering active metals from lithium secondary batteries according to claim 2, wherein: Forming the positive active material mixture includes injecting a non-reactive fluidizing gas into the fluidized bed reactor.

4. The method for recovering active metals from lithium secondary batteries according to claim 3, 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).

5. The method for recovering active metals from lithium secondary batteries according to claim 1, wherein: The heat treatment is performed at a temperature ranging from 100°C to 550°C.

6. The method for recovering active metals from lithium secondary batteries according to claim 5, wherein: The binder is decomposed by the heat treatment, and a temperature rise in the fluidized bed reactor caused by the decomposition of the binder is 15° C. or less.

7. The method for recovering active metals from lithium secondary batteries according to claim 1, wherein: The primary positive 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.

8. The method for recovering active metals from lithium secondary batteries according to claim 1, wherein: The reduction treatment is performed at a temperature ranging from 300°C to 700°C.

9. The method for recovering active metals from lithium secondary batteries according to claim 1, wherein: The reduction treatment is performed in a fluidized bed reactor for forming the positive electrode active material mixture.

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

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