Method for recovering active metals from lithium secondary batteries

Abstract

According to an exemplary embodiment of the present invention, a method for recovering an active metal for a lithium secondary battery includes preparing a preliminary cathode active material mixture including a lithium composite oxide and a binder, removing the binder from the preliminary cathode active material mixture by 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, thereby recovering the active metal for a lithium secondary battery with high purity and high efficiency.

Description

[Technical field]

[0001] 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 technology]

[0002] Secondary batteries are batteries that can be repeatedly charged and discharged, and have been widely applied to portable electronic communication devices such as camcorders, mobile phones, and notebook computers with the development of the information and communication and display industries. Examples of secondary batteries include lithium secondary batteries, nickel-cadmium batteries, nickel-hydrogen batteries, etc. Among them, lithium secondary batteries have been actively developed and applied because of their high operating voltage and high energy density per unit weight, as well as their advantages in terms of charging speed and weight reduction.

[0003] The lithium secondary battery may include an electrode assembly including a positive electrode, a negative electrode, and a separator, and an electrolyte impregnated in the electrode assembly. The lithium secondary battery may further include, for example, a pouch-shaped exterior material that contains the electrode assembly and the electrolyte.

[0004] The positive electrode active material of the lithium secondary battery may be a lithium metal oxide, which may further contain a transition metal such as nickel, cobalt, or manganese.

[0005] The lithium metal oxide as the positive electrode active material can be prepared by reacting a lithium precursor with a nickel-cobalt-manganese (NCM) precursor containing nickel, cobalt, and manganese.

[0006] The use of the high-cost valuable metals in the positive electrode active material results in a high cost for the production of the positive electrode material. In addition, in recent years, as interest in environmental protection has increased, research into methods for recycling the positive electrode active material has been progressing. In order to recycle the positive electrode active material, it is necessary to regenerate the lithium precursor from the waste positive electrode with high efficiency and high purity.

[0007] For example, Korean Patent Publication No. 2015-0002963 discloses a method for recovering lithium using a wet method. However, since cobalt, nickel, etc. are extracted and lithium is recovered from the remaining waste liquid by wet extraction, the recovery rate may be excessively low and a large amount of impurities may be generated from the waste liquid. Summary of the Invention [Problem to be solved by the invention]

[0008] An object of the present invention is to provide a method for collecting active metals of a lithium secondary battery with high efficiency and high yield. [Means for solving the problem]

[0009] In a method for recovering active metals for a lithium secondary battery according to an exemplary embodiment, a preliminary positive electrode active material mixture including a lithium composite oxide and a binder may be prepared. The binder may be removed from the preliminary positive electrode active material mixture by heat treatment in a fluidized bed reactor to form a positive electrode active material mixture. A lithium precursor may be recovered from the positive electrode active material mixture.

[0010] In some embodiments, preparing the positive electrode active material mixture can include removing elements of the positive electrode current collector from a positive electrode including a positive electrode current collector and a positive electrode active material layer by physical pretreatment.

[0011] In some embodiments, forming the cathode active material mixture can include injecting a non-reactive fluidizing gas into the fluidized bed reactor.

[0012] In some embodiments, the non-reactive fluidizing gas is helium (He), nitrogen (N 2 The gas may include at least one selected from the group consisting of neon (Ne), argon (Ar), krypton (Kr) and xenon (Xe).

[0013] In some embodiments, the heat treatment may be carried out at a temperature in the range of 100 to 550°C.

[0014] In some embodiments, the heat treatment decomposes the binder, and the decomposition of the binder may result in a temperature increase in the fluidized bed reactor of 15° C. or less.

[0015] In some embodiments, the preliminary positive electrode active material mixture further includes a carbon-based conductive material, and the conductive material can be removed by the heat treatment in the fluidized bed reactor.

[0016] In some embodiments, recovering the lithium precursor can be by reducing the positive electrode active material mixture to form an active metal precursor mixture containing a lithium precursor and a transition metal precursor, and collecting the lithium precursor from the active metal precursor mixture.

[0017] In some embodiments, the reduction treatment can be carried out at 300 to 700°C.

[0018] In some embodiments, the reduction process can be carried out in the fluidized bed reactor used to form the cathode active material mixture.

[0019] In some embodiments, collecting the lithium precursor may include washing the active metal precursor mixture with water. Effect of the Invention

[0020] In the method for recovering active metals of a lithium secondary battery according to the above-described exemplary embodiment, the binder included in the preliminary positive electrode active material mixture is removed by heat treatment in a fluidized bed reactor, and the aggregation of particles due to side reactions (e.g., over-reduction of active metals) caused by heat generated by decomposition of the binder can be minimized.

[0021] In the method for recovering active metals of a lithium secondary battery according to an exemplary embodiment, the reduced positive electrode active material mixture can be easily recovered in a slurry state, thereby improving the recovery efficiency of the process for recovering active metals of a lithium secondary battery. [Brief description of the drawings]

[0022] [Figure 1] FIG. 1 is a schematic flow chart illustrating a method for recovering active metals from a lithium secondary battery according to an exemplary embodiment. [Diagram 2] FIG. 2 is a schematic flow chart illustrating a method for recovering active metals from a lithium secondary battery according to an exemplary embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0023] An exemplary embodiment of the present invention provides a method for collecting a lithium precursor, comprising: preparing a preliminary cathode active material mixture including a lithium composite oxide and a binder; removing the binder from the preliminary cathode active material mixture by 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.

[0024] Hereinafter, embodiments of the present invention will be described in more detail with reference to the drawings. However, these embodiments are merely illustrative of the present invention and are not intended to limit the present invention.

[0025] The term "precursor" as used herein may refer collectively to a compound containing a specific metal to provide the specific metal contained in the electrode active material.

[0026] 1 and 2 are schematic process flow diagrams illustrating a method for collecting a lithium precursor according to an exemplary embodiment.

[0027] Referring to FIG. 1, a preliminary positive electrode active material mixture including a lithium composite oxide and a binder can be prepared (eg, step S10).

[0028] According to an exemplary embodiment, a preliminary positive electrode active material mixture including a lithium composite oxide and a binder can be prepared from a lithium secondary battery.

[0029] The lithium secondary battery may include an electrode assembly including a positive electrode, a negative electrode, and a separator interposed between the positive electrode and the negative electrode, the positive electrode and the negative electrode including a positive electrode active material layer and a negative electrode active material layer coated on a positive electrode current collector and a negative electrode current collector, respectively.

[0030] 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.

[0031] In some embodiments, the lithium composite oxide may include a compound represented by the following Chemical Formula 1:

[0032] [Chemical formula 1] Li x M1 a M2 b M3 c O y

[0033] In Chemical Formula 1, M1, M2, and M3 can include at least one 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、0<a+b+c≦1であってもよい。

[0034] In some embodiments, the lithium composite oxide may be an NCM-based lithium oxide containing 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, for example, by a co-precipitation reaction.

[0035] However, the embodiment of the present invention can be commonly applied not only to the cathode material containing the lithium composite oxide, but also to any lithium-containing cathode material.

[0036] For example, the positive electrode can be separated from the lithium secondary battery. The positive electrode includes a positive electrode current collector (e.g., aluminum (Al)) and a positive electrode active material layer as described above, and the positive electrode active material layer can include both a conductive material and a binder in addition to the positive electrode active material described above.

[0037] 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.

[0038] The carbon-based conductive material may include, for example, carbon-based materials such as graphite, carbon black, graphene, and carbon nanotubes.

[0039] The binder may include, for example, a resin material such as vinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinylidene fluoride (PVDF), polyacrylonitrile, or polymethylmethacrylate.

[0040] A preliminary positive electrode active material mixture can be prepared from the recovered positive electrode. In some embodiments, the preliminary positive electrode active material mixture can be prepared in a powder form by removing elements of the current collector from the positive electrode by a physical method. Non-limiting examples of the physical method include crushing, grinding, desorption, and peeling.

[0041] The preliminary positive electrode active material mixture includes a powder of a lithium composite oxide and a binder as described above, and is, for example, an NCM-based lithium oxide powder (e.g., Li(NCM)O 2 ) and a binder powder.

[0042] In some embodiments, the recovered positive electrode may be heat-treated before the pulverization treatment. This can promote detachment of the positive electrode current collector during the pulverization treatment, and can at least partially remove the binder and conductive material. The temperature of the heat treatment may be, for example, about 100 to 500°C, preferably about 350 to 450°C.

[0043] In some embodiments, the preliminary positive electrode active material mixture can be obtained after immersing the recovered positive electrode 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 preliminary positive electrode active material mixture including the lithium composite oxide and the binder can be selectively extracted by centrifugation.

[0044] Through the above process, the preliminary positive electrode active material mixture can be obtained in which the positive electrode current collector components, such as aluminum, are substantially completely separated and removed, and the content of the carbonaceous components derived from the binder is reduced.

[0045] In this case, the preliminary positive electrode 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 binder.

[0046] Referring to FIG. 1, the binder may be removed from the preliminary active material mixture by heat treating it in a fluidized bed reactor to form a positive active material mixture (eg, step S20).

[0047] For example, a preliminary positive electrode active material mixture 50 including a lithium composite oxide 60 and a binder 70 can be injected into the fluidized bed reactor 100 .

[0048] For example, the fluidized bed reactor 100 may refer to a reactor that passes a fluid (gas or liquid) through the injected preliminary positive active material mixture 50 to fluidize the preliminary positive active material mixture 50. For example, the fluid may be a non-reactive fluidizing gas, which will be described later.

[0049] In this case, since the binder 70 is removed from the preliminary positive electrode active material mixture 50 in the fluidized bed reactor 100 in a fluidized state, the decomposition heat generated in the process of removing the binder 70 can be evenly distributed throughout the preliminary positive electrode active material mixture 50.

[0050] Therefore, the temperature rise in the reactor due to the decomposition heat can be minimized, and thus the aggregation of particles due to a side reaction of the preliminary positive electrode active material mixture 50 due to the decomposition heat (for example, an over-reduction reaction due to the decomposition heat of the binder) can be minimized.

[0051] In some exemplary embodiments, a non-reactive fluidizing gas can be injected into the fluidized bed reactor 100 to form the cathode active material.

[0052] For example, preliminary positive electrode active material mixture 50 may be injected into fluidized bed reactor 100 through upper inlet 108 a located at the top of fluidized bed reactor 100 .

[0053] For example, the non-reactive fluidizing gas can be injected into the reactor body 110 of the fluidized bed reactor 100 through a gas inlet 104 located at the bottom of the fluidized bed reactor 100 .

[0054] The non-reactive fluidizing gas is helium (He), nitrogen (N 2 The gas may include at least one selected from the group consisting of: neon (Ne), argon (Ar), krypton (Kr), and xenon (Xe).

[0055] The non-reactive fluidizing gas is injected into the fluidized bed reactor 100, thereby fluidizing the preliminary positive electrode active material mixture 50 injected into the fluidized bed reactor 100.

[0056] For example, the fluidized bed reactor 100 may include an expanded section 120 at the top having a larger diameter than the reactor body 110 .

[0057] The expansion section 120 has a diameter larger than that of the reactor body 110, and can reduce the flow rate of the non-reactive fluidizing gas that is injected into the lower part of the fluidized bed reactor 100 and rises upward. This increases the injection rate of the non-reactive fluidizing gas, and effectively prevents the preliminary positive electrode active material mixture 50 from flowing out of the reactor body 110, thereby preventing a decrease in recovery rate.

[0058] For example, the binder 70 may be removed by injecting the preliminary positive electrode active material mixture 50 into the fluidized bed reactor 100, fluidizing the mixture, and then subjecting the mixture to a heat treatment. In this case, a positive electrode active material mixture 90 may be formed in which the binder 70 has been removed from the preliminary positive electrode active material mixture 50. The positive electrode active material mixture 90 may include particles derived from the lithium composite oxide 60, and may be substantially free of particles derived from the binder 70.

[0059] For example, the fluidized bed reactor 100 may include a heating means capable of adjusting the temperature within the reactor body 110 .

[0060] For example, the heat treatment can be performed at a temperature of about 100 to 550° C., and more preferably, at about 400 to 500° C. Within this temperature range, decomposition of the binder can be initiated, and side reactions due to a temperature rise in the reactor body 110 can be minimized.

[0061] For example, if the temperature of the heat treatment is below the above range, the binder may remain without being decomposed, whereas if the temperature exceeds the above range, lithium carbonate (Li 2 CO 3 ) may be formed and the particles may aggregate, which may reduce the recovery efficiency of the lithium precursor.

[0062] In some exemplary embodiments, the heat treatment decomposes the binder 70, and the temperature rise in the fluidized bed reactor 100 due to the decomposition of the binder 70 may be about 15° C. or less, and preferably about 10° C. or less. The temperature rise may be about 1° C. or more, although a lower limit is advantageous.

[0063] In this case, since the decomposition of the binder 70 is carried out in the fluidized bed reactor 100, the heat of decomposition of the binder 70 is dispersed throughout the fluidized preliminary positive electrode active material mixture 50, thereby minimizing the temperature rise due to the heat of decomposition.

[0064] This minimizes side reactions of the preliminary positive active material mixture 50 caused by decomposition of the binder 70 (eg, over-reduction of lithium composite oxide by carbon), and improves the process efficiency of the lithium precursor recovery process described below.

[0065] In some exemplary embodiments, preliminary positive electrode active material mixture 50 further includes carbon-based conductive material 80, and conductive material 80 can also be removed by the heat treatment in fluidized bed reactor 100. This can further improve the recovery efficiency of active metals of lithium secondary batteries.

[0066] In some exemplary embodiments, the formed cathode active material mixture may have an average diameter (D50, e.g., based on cumulative volume distribution) of about 1 to 100 μm. In this range, the contact area between the reduction gas and the cathode active material mixture during the reduction process described below is increased, and the collection efficiency of the lithium precursor may be improved.

[0067] For example, when the formation of the positive electrode active material mixture 90 is performed in a non-fluidized reactor, in the process of removing the binder 70 from the preliminary positive electrode active material 50, a side reaction (e.g., over-reduction by carbon) may occur due to the heat of decomposition of the binder 70, and the particles contained in the positive electrode active material mixture 90 may aggregate with each other.

[0068] In this case, the diameter of the particles contained in the positive electrode active material mixture 90 may increase to 1 cm or more, which may prevent the positive electrode active material mixture 90 from being fluidized for the reduction reaction described below, thereby decreasing the process efficiency of the reduction reaction described below.

[0069] In some exemplary embodiments, the particle size distribution of the formed positive electrode active material mixture 90 may be greater than about 0 μm to about 500 μm or less.

[0070] When the particle size distribution range is satisfied, the cathode active material mixture can be reduced uniformly throughout, whereby heat generated during the reduction reaction is uniformly distributed throughout the cathode active material mixture, minimizing side reactions caused by the heat generated during the reduction reaction, thereby further improving the yield of the lithium precursor.

[0071] For example, the formed 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.

[0072] In one embodiment, the positive electrode active material mixture 90 may be placed directly in the fluidized bed reactor 100, and the lithium precursor recovery process may be performed in the fluidized bed reactor 100 in which the positive electrode active material mixture 90 is formed.

[0073] 1 and 2, the lithium precursor may be collected from positive electrode active material mixture 90 (eg, step S30).

[0074] In this case, since the positive electrode active material mixture 90 formed in the fluidized bed reactor 100 has a uniform particle distribution, a reduction process for collecting the lithium precursor can be performed, and the contact area with the reducing gas can be increased.

[0075] In addition, since the binder 70, which generates a large amount of heat of decomposition, is removed from the positive electrode active material mixture 90, it is possible to minimize an increase in the internal temperature of the reduction reactor 200 due to heat generated by the decomposition of the binder 70 in the lithium precursor recovery process. This makes it possible to minimize a side reaction of the positive electrode active material mixture 90 (e.g., over-reduction of the positive electrode active material) due to the heat of decomposition of the binder 70. This makes it possible to improve the efficiency of collecting the lithium precursor.

[0076] The lithium precursor may be lithium hydroxide (LiOH), lithium oxide (Li 2 O) or lithium carbonate (Li 2 CO 3 From the viewpoints of the charge / discharge characteristics, life characteristics, high-temperature stability, etc. of the lithium secondary battery, the lithium precursor may contain lithium hydroxide.

[0077] In one embodiment, lithium carbonate may cause a deposition reaction on the separator, which may reduce the life stability. Therefore, lithium carbonate (Li 2 CO 3 ) may be substantially free of.

[0078] In some embodiments, the recovery of the lithium precursor can be performed by reducing the positive electrode active material mixture 90 to form an active metal precursor mixture including a lithium precursor and a transition metal precursor (eg, step S32).

[0079] For example, the positive electrode active material mixture (e.g., positive electrode active material) may be reduced with hydrogen in the reduction reactor 200 to form the active metal precursor mixture. The hydrogen may be injected into the reactor body 210 through a gas injector 204 located at the bottom of the reduction reactor 200.

[0080] The hydrogen reduction reaction can be carried out at a temperature of about 300 to 700° C., preferably 400 to 550° C. In this case, the reduction reactor 200 can include a separate heating means for increasing the internal temperature. In this temperature range, the yield of the active precursor mixture produced from the positive electrode active material mixture 90 can be improved.

[0081] In addition, since the positive electrode active material mixture 90 does not substantially contain a binder, it is possible to prevent a temperature rise in the reduction reactor 200 due to the decomposition heat of the binder. This prevents over-reduction of the positive electrode active material mixture 90 due to the decomposition heat, and minimizes particle aggregation due to bonding between nickel (Ni) and cobalt (Co) contained in the positive electrode active material mixture 90. In addition, the active metal precursor mixture formed by the reduction of the positive electrode active material mixture 90 can be more easily collected in a slurry state.

[0082] The additional temperature rise in the reduction reactor 200 due to the hydrogen reduction reaction may be about 30° C., and preferably about 25° C. or less. The lower limit of the additional temperature rise is not particularly limited, but may be about 1° C. or more.

[0083] In some exemplary embodiments, the reduction reactor 200 may be a fluidized bed reactor, in which case hydrogen and the non-reactive fluidizing gas may be injected together through a gas inlet located at the bottom of the fluidized bed reactor.

[0084] For example, an expansion tube section 220 may be located at the upper part of the reduction reactor 200. The expansion tube section 220 reduces the flow rate of the non-reactive fluidizing gas injected from the lower part of the reduction reactor 200, and can effectively prevent the positive electrode active material mixture 90 from leaking out during the process of fluidizing the positive electrode active material mixture 90 located in the reduction reactor 200.

[0085] The active precursor mixture may include a preliminary lithium precursor and a preliminary transition metal precursor that are hydrogen reduction products of the lithium composite oxide included in the positive electrode active material mixture.

[0086] The reserve lithium precursor may include lithium hydroxide, lithium oxide, and / or lithium carbonate. According to an exemplary embodiment, the reserve lithium precursor is obtained by a hydrogen reduction reaction, so that the mixed content of lithium carbonate can be reduced.

[0087] The preliminary transition metal precursors can include Ni, Co, NiO, CoO, MnO, and the like.

[0088] For example, since the active precursor mixture is formed by reduction of the positive electrode active material mixture 90 that is substantially free of the binder, the active precursor mixture may be substantially free of nickel (Ni)-cobalt (Co) bonds formed by over-reduction of the positive electrode active material mixture 90. This allows the active precursor mixture to be more easily recovered in a slurry state.

[0089] In some exemplary embodiments, the reduction reaction may be performed in the fluidized bed reactor 100 in which the cathode active material mixture is formed. In this case, the formation of the cathode active material mixture and the reduction reaction are performed in the same reactor, which may prevent a problem of a portion of the cathode active material mixture being lost during the transport of the formed cathode active material mixture. This may further improve the recovery efficiency of the lithium precursor.

[0090] In some exemplary embodiments, the positive electrode active material mixture 90 can be injected into the reduction reactor 200 through an upper inlet 208a located at the top of the reduction reactor 200. The active metal precursor mixture can be collected through an outlet 208b located at the bottom of the reduction reactor 200. The collected active metal precursor mixture can be injected into a lithium precursor collection step described below.

[0091] For example, before collecting the active metal precursor mixture, water and a non-reactive fluidizing gas may be injected into the reduction reactor 200 to make the active metal precursor mixture into a slurry state. In this case, the active metal precursor mixture that has been aggregated by the reduction reaction may be deagglomerated. This allows the active metal precursor mixture to be more easily collected in a slurry state.

[0092] For example, water can be injected into the reduction reactor 200 through the upper inlet 208a of the reduction reactor 200, and the 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.

[0093] For example, the slurry state active metal precursor mixture can be collected through the outlet 208b located at the bottom of the reduction reactor 200.

[0094] According to one embodiment, the formed active metal precursor mixture is not collected separately from the reduction reactor 200, but is located within the reduction reactor 200, and the lithium precursor collection step described below can also be performed within the reduction reactor 200.

[0095] According to some exemplary embodiments, the lithium precursor may be collected from the active metal precursor mixture (eg, step S34).

[0096] For example, lithium precursors can be collected by reacting the active metal precursor mixture formed from the hydrogen reduction reaction described above with the leachate.

[0097] For example, the active metal precursor mixture can react with the leachate to form a solution in which the lithium precursor is dissolved and a precipitate in which the preliminary transition metal precursor is precipitated.

[0098] For example, lithium oxide may react with the leachate to form lithium hydroxide, which may dissolve in the leachate.

[0099] For example, lithium carbonate may have low solubility in the leachate, allowing it to be precipitated and removed from the pre-precursor mixture.

[0100] In some embodiments, the leachate may include water. In this case, the active metal precursor mixture may be washed with water, which may cause the active metal precursor mixture to react with water to form a lithium precursor in which lithium hydroxide is dissolved in water.

[0101] In some exemplary embodiments, the leachate may further include dimethyl carbonate or diethyl carbonate.

[0102] For example, dimethyl carbonate or diethyl carbonate can promote the reaction of the reserve lithium precursor with water, thereby improving the separation efficiency of the lithium precursor.

[0103] In some embodiments, the precipitate may comprise a slurry comprising a preliminary lithium precursor mixture.

[0104] For example, the slurry may be formed by dispersing a pre-transition metal precursor in the leachate that is insoluble in the leachate, such that the lithium precursor can be collected by separating the slurry from the solution in which the lithium precursor is dissolved.

[0105] In one embodiment, the precipitated pre-transition metal precursor can be collected to form the transition metal precursor, for example, the pre-transition metal precursor can be reacted with an acid solution to form the transition metal precursor.

[0106] In one embodiment, the acid solution may be sulfuric acid. In this case, the transition metal precursor may include a transition metal sulfate. For example, the transition metal sulfate may be NiSO 4 , MnSO 4 and CoSO 4 etc.

[0107] The reaction between the preliminary precursor mixture and the leachate can be carried out in the reduction reactor 200 where the hydrogen reduction process is carried out or in the fluidized bed reactor 100 where the positive active material mixture formation process is carried out. In this case, the process of forming the positive active material mixture, the process of forming the preliminary lithium precursor, or the process of collecting each product after the process of forming the precursor mixture is not required, and a decrease in the recovery rate of the lithium precursor that may occur during the transport of each product can be minimized.

[0108] In the following, specific examples are presented to aid in understanding the present invention, but these examples are merely illustrative of the present invention and do not limit the scope of the appended claims. It is clear to those skilled in the art that various changes and modifications can be made to these examples within the scope of the scope and technical ideas of the present invention, and it is natural that these changes and modifications fall within the scope of the appended claims.

[0109] Example 1 1 kg of the positive electrode material separated from the waste lithium secondary batteries was cut into small units and pulverized by milling to obtain a preliminary positive electrode active material mixture containing Li-Ni-Co-Mn oxide and a binder (polyvinylidene fluoride, PVDF).

[0110] 0.2 kg of the preliminary positive electrode active material mixture was poured into a fluidized bed reactor. N 2 The preliminary positive active material mixture was fluidized by injecting gas, and the internal temperature of the fluidized bed reactor was increased to 450° C. to pyrolyze the binder contained in the preliminary positive active material mixture, thereby preparing a positive active material mixture.

[0111] The positive electrode active material mixture was fluidized in the fluidized bed reactor and reacted with hydrogen gas to form an active metal precursor mixture containing lithium hydroxide. The internal temperature of the fluidized bed reactor was maintained at 450°C.

[0112] Water and nitrogen were added to the formed active metal precursor to form a slurry of the active metal precursor, which was then collected and washed with water to obtain an aqueous lithium precursor solution.

[0113] Comparative Example 1 A lithium precursor was obtained in the same manner as in Example 1, except that the thermal decomposition step of the binder for producing the positive electrode active material mixture was carried out using a non-fluidized reactor.

[0114] Comparative Example 2 A lithium precursor was obtained in the same manner as in Example 1, except that the thermal decomposition step of the binder was not carried out during the preparation of the positive electrode active material mixture.

[0115] For Example 1 and Comparative Examples 1 and 2, the deviation value (°C) of the internal temperature change of the fluidized bed reactor measured during the positive electrode active material mixing process, the average diameter of the formed positive electrode active material mixture particles, particle size distribution, the presence or absence of by-products, and the binder removal rate are shown in Table 1.

[0116] In addition, the maximum deviation value of the temperature change inside 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.

[0117] [Table 1]

[0118] Referring to Table 1, in Example 1, in which a fluidization pyrolysis process was performed to remove the binder contained in the preliminary positive active material mixture, an excellent lithium precursor recovery rate was achieved.

[0119] In contrast, in Comparative Example 1, in which a non-fluidized pyrolysis step was performed, the positive electrode active material mixture formed aggregated together due to a side reaction (e.g., over-reduction) in the pyrolysis step, and therefore the positive electrode active material mixture could not be easily fluidized, decreasing the efficiency of the hydrogen reduction step.

[0120] In addition, in Comparative Example 2 in which the thermal decomposition step was not performed, the produced metal active material mixture may aggregate due to a side reaction (e.g., an over-reduction reaction of the positive electrode active material mixture) caused by the heat of decomposition due to the decomposition of the binder during the hydrogen reduction step. Therefore, the over-reduced metal active material mixture cannot be easily changed into a slurry state, and the recovery rate of the lithium precursor is reduced.

Claims

1. providing a preliminary positive electrode active material mixture including a lithium composite oxide and a binder; removing the binder from the preliminary cathode active material mixture by 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; The step of recovering the lithium precursor comprises: reducing the positive electrode active material mixture to form an active metal precursor mixture containing the lithium precursor and a transition metal precursor; collecting the lithium precursor from the active metal precursor mixture; The method for recovering active metals from a lithium secondary battery, wherein the reduction treatment is carried out in the fluidized bed reactor used in the step of forming the positive electrode active material mixture.

2. 2. The method for recovering active metals of a lithium secondary battery according to claim 1, wherein the step of preparing the preliminary positive electrode active material mixture comprises removing elements of the positive electrode current collector from a positive electrode including a positive electrode current collector and a positive electrode active material layer by physical pretreatment.

3. 3. The method for recovering active metals of a lithium secondary battery according to claim 2, wherein the step of forming the positive electrode active material mixture comprises injecting a non-reactive fluidizing gas into the fluidized bed reactor.

4. The non-reactive fluidizing gas may be helium (He), nitrogen (N ２ 4. The method for recovering active metals from a lithium secondary battery according to claim 3, wherein the active metal comprises at least one selected from the group consisting of neon (Ne), argon (Ar), krypton (Kr) and xenon (Xe).

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

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

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

8. 2. The method for recovering active metals from a lithium secondary battery according to claim 1, wherein the reduction treatment is carried out at 300 to 700° C.

9. 2. The method for recovering active metals of a lithium secondary battery according to claim 1, wherein the step of collecting the lithium precursor comprises washing the active metal precursor mixture with water.

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