Method for recovering active metals from lithium secondary batteries

Abstract

A method of recovering active metals of lithium secondary batteries, the method including the steps of: preparing a primary cathode active material mixture from a cathode of a waste lithium secondary battery; fluidizing the primary cathode active material mixture by a gas containing oxygen in a fluidized bed reactor to form a cathode active material mixture; injecting a reducing gas into the fluidized bed reactor to form a primary precursor mixture from the fluidized cathode active material mixture; and recovering a lithium precursor from the primary precursor mixture.

Description

Technical Field

[0001] 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 the waste positive electrode of lithium secondary batteries. Background Technology

[0002] Rechargeable batteries are batteries that can be repeatedly charged and discharged. With the development of the information communication and display industries, rechargeable batteries are widely used in portable electronic communication devices, such as portable cameras, mobile phones, and laptops. Examples of rechargeable batteries include lithium batteries, nickel-cadmium batteries, and nickel-metal hydride batteries. Among them, lithium batteries have high operating voltage and energy density per unit weight, and are advantageous for charging speed and lightweight design. Therefore, lithium batteries are being actively developed and applied.

[0003] A lithium secondary battery may include an electrode assembly and an electrolyte impregnating the electrode assembly, wherein the electrode assembly includes a positive electrode, a negative electrode, and a separator. The lithium secondary battery may also include, for example, a pouch-type outer packaging material housing the electrode assembly and the electrolyte.

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

[0005] The lithium metal oxide, which is 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] Because the aforementioned high-cost metals are used in the positive electrode active material, the preparation of the positive electrode material requires excessively high costs. Furthermore, due to the increasing prominence of environmental issues in recent years, methods for recycling positive electrode active materials are being researched. To recycle the positive electrode active material, it is necessary to regenerate the lithium precursor from waste positive electrodes with high efficiency and high purity. Summary of the Invention

[0007] Technical problems to be solved

[0008] One technical problem of the present invention is to provide a method for recovering active metals from lithium secondary batteries with high efficiency and high purity.

[0009] Technical solution

[0010] In a method for recovering active metals from lithium secondary batteries according to an embodiment of the present invention, a primary positive electrode active material mixture is prepared from the positive electrode of a waste lithium secondary battery; the primary positive electrode active material mixture is fluidized in a fluidized bed reactor by passing an oxygen-containing gas to form a positive electrode active material mixture; a reducing gas is injected into the fluidized bed reactor to form a primary precursor mixture from the fluidized positive electrode active material mixture; and lithium precursors are recovered from the primary precursor mixture.

[0011] In some embodiments, the positive electrode may include: a positive current collector; and a positive active material layer, the positive active material layer being formed on the positive current collector and comprising a binder, a conductive material, and the positive active material. The step of preparing the primary positive active material mixture may include removing the positive current collector from the positive electrode. The primary positive active material mixture may comprise the binder, the conductive material, and the positive active material.

[0012] In some embodiments, the step of fluidizing the primary positive electrode active material mixture with the oxygen-containing gas may include decomposing or burning the binder and the conductive material in the fluidized bed reactor.

[0013] In some embodiments, the oxygen-containing gas may comprise oxygen (O2) and a non-reactive gas. The non-reactive gas may comprise at least one selected from helium (He), nitrogen (N2), neon (Ne), argon (Ar), krypton (Kr), and xenon (Xe).

[0014] In some embodiments, the volume ratio of oxygen relative to the total volume of the oxygen-containing gas can be 10-30% by volume, and the volume ratio of the non-reactive gas can be 70-90% by volume.

[0015] In some embodiments, the step of fluidizing the primary positive electrode active material mixture with the oxygen-containing gas can be carried out at a temperature of 100-600°C.

[0016] In some embodiments, the step of fluidizing the primary positive electrode active material mixture with the oxygen-containing gas may include heating from a temperature below 50°C to a target temperature in the range of 400-600°C for 1-2 hours.

[0017] In some embodiments, the step of forming the primary positive electrode active material mixture may include heat treatment at the target temperature for 2-5 hours.

[0018] In some implementations, the reducing gas may contain hydrogen.

[0019] In some embodiments, the step of forming the primary precursor mixture can be carried out at a temperature in the range of 400-500°C.

[0020] In some embodiments, the steps of fluidizing the primary positive electrode active material mixture with the oxygen-containing gas and forming the primary precursor mixture can be carried out continuously in-situ in the fluidized bed reactor.

[0021] In some embodiments, the primary precursor mixture may comprise primary lithium precursor particles and particles containing a transition metal. The particles containing the transition metal may comprise Ni, Co, NiO, CoO, and MnO.

[0022] In some embodiments, the primary lithium precursor particles may comprise at least one of lithium hydroxide, lithium oxide, or lithium carbonate.

[0023] In some implementations, the step of recovering the lithium precursor may include washing the primary lithium precursor particles with water to collect the lithium hydroxide.

[0024] Beneficial effects

[0025] According to the exemplary embodiments described above, lithium precursors can be recovered from the positive electrode active material of spent lithium secondary batteries by introducing an oxygen-containing gas to decompose and burn the binder and conductive materials through a fluidization process and a hydrogen reduction process. Therefore, particle aggregation caused by side reactions (e.g., excessive reduction of lithium) resulting from the heat of decomposition generated during binder decomposition and the heat of combustion generated during the combustion of conductive materials can be minimized.

[0026] Furthermore, the conductive material can react with oxygen in an oxygen-containing gas to burn, thus preventing the generation of carbon-based byproducts (e.g., lithium carbonate) originating from the conductive material. Therefore, the recovery rate of the desired lithium precursor can be improved, and no subsequent processes for byproduct removal are required, thereby improving the economics and long-term operability of the process. Attached Figure Description

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

[0028] Figure 2 This is a schematic flowchart illustrating a method for recovering active metals from lithium secondary batteries according to some implementation schemes. Detailed Implementation

[0029] The embodiments of the present invention provide a method for recovering active metals from the positive electrode of waste lithium secondary batteries with high purity and high yield.

[0030] The embodiments of the present invention will now be described in detail. The present invention can be modified in various ways and can take many forms. Specific embodiments are illustrated in the accompanying drawings and described in detail herein. However, it should be understood that this is not intended to limit the invention to the specific forms disclosed, but rather to encompass all modifications, equivalents, and substitutions included within the spirit and scope of the present invention.

[0031] Unless otherwise defined, all terms used herein, including technical and scientific terms, shall have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. Terms as defined in commonly used dictionaries shall be interpreted as having a meaning consistent with their meaning in the context of the relevant art, and shall not be construed as having an idealized or overly formal meaning unless expressly defined herein.

[0032] As used in this specification, the term "precursor" refers to a compound containing a specific metal in order to provide a specific metal contained in an electrode active material.

[0033] Figure 1 This is a schematic flowchart illustrating a method for recovering active metals from lithium secondary batteries according to an exemplary embodiment.

[0034] Reference Figure 1 Primary cathode active material mixture 50 (e.g., waste cathode active material mixture) can be prepared from the waste cathode of a lithium secondary battery (e.g., process S10).

[0035] A lithium secondary battery may include an electrode assembly comprising a positive electrode, a negative electrode, and a separator between the positive and negative electrodes. The positive and negative electrodes may each comprise a positive active material layer and a negative active material layer coated on a positive current collector and a negative current collector, respectively.

[0036] For example, the positive electrode active material contained in the positive electrode active material layer may contain oxides containing lithium and transition metals.

[0037] In some implementations, the positive electrode active material may comprise a compound represented by the following chemical formula 1.

[0038] [Chemical Formula 1]

[0039] Li x M1 a M2 b M3 c O y

[0040] In Chemical Formula 1, M1, M2, and M3 can be transition metals selected from Ni, Co, Mn, Na, Mg, Ca, Ti, V, Cr, Cu, Zn, Ge, Sr, Ag, Ba, Zr, Nb, Mo, Al, Ga, or B. In Chemical Formula 1, M1, M2, and M3 can be 0. <x≤1.1,2≤y≤2.02,0<a<1,0<b<1,0<c<1,0<a+b+c≤1。

[0041] In some implementations, the positive electrode active material can be an NCM-based lithium oxide containing nickel, cobalt, and manganese.

[0042] The positive electrode can be separated from waste lithium secondary batteries for recycling. As described above, the waste positive electrode may include a positive electrode current collector (e.g., aluminum (Al)) and a positive electrode active material layer, and the positive electrode active material layer may contain the aforementioned positive electrode active material as well as conductive materials and binders.

[0043] The conductive material may include, for example, carbon-based materials such as graphite, carbon black, graphene, and carbon nanotubes. The adhesive may include, for example, resins such as vinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinylidene fluoride (PVDF), polyacrylonitrile, and polymethyl methacrylate.

[0044] According to an exemplary embodiment, a primary cathode active material mixture 50 can be formed by pulverizing the recycled waste cathode. Therefore, the primary cathode active material mixture 50 can be made into powder form. As described above, the primary cathode active material mixture 50 may contain lithium-transition metal oxide powder, such as NCM-based lithium oxide powder (e.g., Li(NCM)O2), binder powder, and conductive material powder.

[0045] The term "primary cathode active material mixture" as used in this invention can refer to the raw material added to the fluidized process described below using an oxygen-containing gas after the cathode current collector has been substantially removed from the waste cathode. In one embodiment, the primary cathode active material mixture 50 may comprise cathode active material particles such as the NCM-based lithium oxide. In one embodiment, the primary cathode active material mixture 50 may also comprise a portion of components derived from the binder 70 or the conductive material 80.

[0046] In some embodiments, the average particle size (D50) of the primary cathode active material mixture 50 can be 5-100 μm. Within this range, lithium-transition metal oxides, such as Li(NCM)O2, which are intended for recycling, can be readily separated from the cathode current collector, binder 70, and conductive material 80 contained in the primary cathode active material mixture 50.

[0047] In some embodiments, the recovered positive electrode may be heat-treated prior to the pulverization process. This facilitates the shedding of the positive electrode current collector during the pulverization process and removes at least a portion of the binder 70 and conductive material 80. The heat treatment temperature may be, for example, at about 100-500°C, preferably at about 350-450°C.

[0048] In some embodiments, the primary positive electrode active material mixture 50 can be obtained by impregnating the recovered positive electrode in an organic solvent. For example, the recovered positive electrode can be impregnated in an organic solvent to separate and remove the positive electrode current collector, and the primary positive electrode active material mixture 50 containing positive electrode active material particles, binder, and conductive material can be selectively extracted by centrifugation.

[0049] Through the above process, positive electrode current collector components such as aluminum can be substantially completely separated and removed, and a primary positive electrode active material mixture 50 with reduced carbon-based content derived from binder 70 and / or conductive material 80 can be obtained.

[0050] An oxygen-containing gas can be injected into the fluidized bed reactor 100 to fluidize the primary positive electrode active material mixture 50 to form a positive electrode active material mixture 90 (e.g., process S20).

[0051] As used in this invention, the term "fluidized bed reactor" can refer to a reactor in which a fluid (gas or liquid) is passed through an injected primary positive electrode active material mixture 50 to fluidize the primary positive electrode active material mixture 50. For example, the fluid can be an oxygen-containing gas.

[0052] In an exemplary embodiment, a primary positive electrode active material mixture 50 comprising positive electrode active material particles 60, binder 70 and conductive material 80 may be injected into the fluidized bed reactor 100.

[0053] For example, the primary positive electrode active material mixture 50 can be injected into the fluidized bed reactor 100 through the upper injection port 108a located at the top of the fluidized bed reactor 100.

[0054] In an exemplary embodiment, an oxygen-containing gas may be injected into the fluidized bed reactor 100.

[0055] The oxygen-containing gas can be injected into the reactor body 110 of the fluidized bed reactor 100 through the gas injection port 104 located at the bottom of the fluidized bed reactor 100.

[0056] In an exemplary embodiment, the oxygen-containing gas may be a mixture of oxygen (O2) and a non-reactive gas. The non-reactive gas may include at least one selected from helium (He), nitrogen (N2), neon (Ne), argon (Ar), krypton (Kr), and xenon (Xe).

[0057] For example, relative to the total volume of the oxygen-containing gas, the volume ratio of oxygen can be 10-30% by volume, and the volume ratio of non-reactive gases can be 70-90% by volume.

[0058] As the oxygen-containing gas is 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.

[0059] For example, the upper part of the fluidized bed reactor 100 may also include a diffuser section 120, which has a diameter larger than that of the reactor body 110. The diffuser section 120 has a larger diameter than the reactor body 110, thus reducing the flow rate of the oxygen-containing gas injected from the bottom and rising from the fluidized bed reactor 100. Therefore, it can effectively prevent a decrease in recovery rate caused by leakage of the primary positive electrode active material mixture 50 to the outside of the reactor body 110 as the injection rate of the oxygen-containing gas increases.

[0060] In an exemplary embodiment, the step of fluidizing the primary positive electrode active material mixture 50 with the oxygen-containing gas may further include heat-treating the binder and the conductive material in the fluidized bed reactor to decompose or burn them. For example, the conductive material 80 may react with the oxygen contained in the oxygen-containing gas to burn into carbon monoxide (CO) or carbon dioxide (CO2) and be removed.

[0061] Therefore, the generation of carbon-derived byproducts (e.g., lithium carbonate) can be reduced in the hydrogen reduction process described below. In this case, for example, the content of lithium hydroxide, a primary lithium precursor, is increased, thereby improving the recovery rate of the lithium precursor, and, for example, eliminating the need for subsequent processes to remove byproducts, thus improving process economics and long-term operability.

[0062] For example, the decomposition rate of the adhesive 70 after heat treatment can be 95% or more, preferably 99% or more.

[0063] For example, the combustion rate of the conductive material 80 after heat treatment can be 95% or more, preferably 99% or more.

[0064] In some embodiments, the adhesive 70 and the conductive material 80 can be simultaneously decomposed or burned by the fluidized heat treatment described above.

[0065] In an exemplary embodiment, the heat treatment temperature can be about 100-600°C, more preferably about 400-600°C. In this case, the fluidized bed reactor 100 may include a heating device that can adjust the temperature inside the reactor body 110.

[0066] Within the aforementioned temperature range, for example, the decomposition of the adhesive 70 and the combustion reaction of the conductive material 80 can be initiated.

[0067] For example, when the heat treatment temperature meets the above range, the residual rate of binder 70 and conductive material 80 in the positive electrode active material mixture 90 can be significantly reduced.

[0068] For example, when binder 70 remains in the positive electrode active material mixture 90, excessive reduction may occur in the hydrogen reduction process described below, for example, due to the heat of decomposition of the binder 70, and particle aggregation may occur, thereby reducing the recovery rate of lithium precursor.

[0069] For example, if conductive material 80 remains in the positive electrode active material mixture 90, the content of carbon-derived byproducts such as lithium carbonate (Li2CO3) may increase in the hydrogen reduction process described below, and the process stability and lithium precursor recovery rate may decrease. In this case, a subsequent process (e.g., a filtration process) to remove the carbon-derived byproducts may be added, but the economics and process stability of the method for recovering the active metal of the lithium secondary battery may decrease.

[0070] According to some implementation schemes, when the heat treatment temperature exceeds 600°C, lithium carbonate may be formed through side reactions of the positive electrode active material particles 60 (e.g., excessive reduction caused by carbon), and the particles may aggregate. In this case, the reduction rate of the positive electrode active material particles decreases, thereby potentially reducing the recovery rate of the lithium precursor.

[0071] In an exemplary embodiment, the step of fluidizing the primary positive electrode active material mixture 50 with an oxygen-containing gas may include heating from a temperature below 50°C to a target temperature in the range of 400-600°C for 1-2 hours.

[0072] In this case, for example, heat treatment at the target temperature for 2-5 hours may also be included.

[0073] In some exemplary embodiments, the heat treatment decomposes the binder 70 and burns the conductive material 80, and due to the decomposition of the binder 70 and the combustion of the conductive material 80, the temperature of the fluidized bed reactor 100 can rise to below about 50°C, preferably below about 30°C. A lower lower limit for the temperature rise is more advantageous, but it can be above about 1°C.

[0074] The decomposition of the binder 70 and the combustion of the conductive material 80 can occur inside the fluidized bed reactor 100, thus dispersing the heat of decomposition of the binder 70 and the heat of combustion of the conductive material 80 throughout the primary cathode active material mixture 50, thereby minimizing the temperature rise caused by the heat of decomposition and the heat of combustion. Therefore, the melting and aggregation of particles caused by side reactions in the primary cathode active material mixture 50 (e.g., excessive reduction reactions due to the heat of decomposition and the heat of combustion) can be suppressed, thereby improving the reduction rate in the hydrogen reduction process described below.

[0075] In some embodiments, the average diameter of the positive electrode active material mixture 90 can be about 1-100 μm. Within this range, the contact area between the reducing gas and the positive electrode active material mixture 90 can be increased in the reduction process described below, and the recovery rate of the lithium precursor can be improved.

[0076] In some exemplary embodiments, the particle size distribution of the positive electrode active material mixture 90 can be from more than 0 μm to less than 500 μm.

[0077] When the particle size distribution range described above is met, for example, the positive electrode active material mixture 90 can be reduced uniformly throughout. Therefore, the heat generated during the reduction reaction is uniformly distributed throughout the entire positive electrode active material mixture 90, thereby minimizing side reactions caused by the heat generated during the reduction reaction. Therefore, the recovery rate of the lithium precursor can be improved.

[0078] In a comparative example, the binder 70 and conductive material 80 can be decomposed and combusted by heat treatment in a non-fluidized bed reactor. However, in the case of the non-fluidized bed reactor described above, the heat of decomposition of the binder 70 and the heat of combustion of the conductive material 80 are not dispersed throughout the reactor, and the temperature rise caused by the concentration of the heat of decomposition and combustion may lead to the aforementioned side reactions, and the particles contained in the primary positive electrode active material mixture 50 may melt and aggregate.

[0079] In this case, the diameter of the particles contained in the primary cathode active material mixture 50 may increase to more than 1 cm. Therefore, it is impossible to refluidize the primary cathode active material mixture 50 used for the reduction reaction described below, which may reduce the process efficiency of the reduction reaction and the recovery rate of lithium precursors.

[0080] In a comparative example, the primary cathode active material mixture 50 can be prepared by heat treatment in a separate combustion furnace instead of the fluidized bed reactor 100. However, in this case, aggregation of metal (e.g., Ni and Co) particles contained in the cathode active material mixture 90 may occur, and the reduction rate may decrease when the aggregated particles are added to carry out the reduction process described below, thereby potentially reducing the recovery rate of the lithium precursor.

[0081] In an exemplary embodiment, the positive electrode active material mixture 90 formed by process S20 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 the hydrogen reduction process described below.

[0082] In an exemplary embodiment, the positive electrode active material mixture 90 may be reduced to form a primary precursor mixture comprising primary lithium precursor particles and particles containing transition metals (e.g., process S30).

[0083] For example, the particles containing transition metals may include Ni, Co, NiO, CoO, and MnO.

[0084] For example, the primary lithium precursor particles may contain at least one of lithium hydroxide (LiOH), lithium oxide (Li2O), and lithium carbonate (Li2CO3). The lithium precursor may contain lithium hydroxide to improve the charge / discharge characteristics, lifespan characteristics, and high-temperature stability of lithium secondary batteries.

[0085] In an exemplary embodiment, the steps of fluidizing the primary positive electrode active material mixture 50 with an oxygen-containing gas and forming the primary precursor mixture can be carried out continuously in situ within the fluidized bed reactor 100. In this case, the formation of the positive electrode active material mixture 90 and the hydrogen reduction reaction occur in the same reactor, thus preventing the loss of a portion of the positive electrode active material mixture 90 during transport. Therefore, the recovery rate of the lithium precursor can be further improved.

[0086] The positive electrode active material mixture 90 can be reduced by a reducing gas to form a primary precursor mixture, which is injected into the reactor body 110 through a gas inlet 104 located at the bottom of the fluidized bed reactor 100.

[0087] As a reducing gas, a mixture of hydrogen and the non-reactive gas can be injected, wherein the volume ratio of hydrogen can be 5-40% and the volume ratio of the non-reactive gas can be 60-95% relative to the total volume of the mixture.

[0088] The hydrogen reduction reaction can be carried out at a temperature of about 300-700°C, preferably at a temperature of 400-500°C. Within the above temperature range, the yield of the primary precursor mixture formed from the positive electrode active material mixture 90 can be increased.

[0089] In some embodiments, due to the hydrogen reduction reaction, the temperature of the fluidized bed reactor 100 can be further increased by about 10°C or less, preferably by about 5°C or less. The lower limit of the aforementioned further temperature increase is not particularly limited, but can be above about 1°C.

[0090] For example, the positive electrode active material mixture 90 may substantially be free of binders, in which case an increase in the internal temperature of the fluidized bed reactor 100 due to the heat of decomposition of the binders can be prevented. Therefore, excessive reduction of the positive electrode active material mixture 90 due to the heat of decomposition is prevented, thereby minimizing particle aggregation caused by the bonding between nickel (Ni) and cobalt (Co) contained in the positive electrode active material mixture 90. Furthermore, the primary precursor mixture formed by reducing the positive electrode active material mixture 90 can be more easily collected in a slurry state.

[0091] For example, the positive electrode active material mixture 90 may substantially not contain conductive material 80, and the content of byproducts (e.g., lithium carbonate) formed by the reduction reaction caused by carbon can be reduced. In this case, the mixed content of lithium hydroxide in the primary precursor mixture is increased, which has high solubility in the leachate, thereby increasing the recovery rate of lithium precursors in the following lithium precursor recovery step.

[0092] In some embodiments, the positive electrode active material mixture 90 does not substantially contain conductive material 80, thus reducing the heat of reaction generated by the reduction reaction of carbon, and in this case, suppressing part of the temperature rise caused by the reduction reaction.

[0093] According to an exemplary embodiment, water and non-reactive gases can be injected into the fluidized bed reactor 100 before collecting the formed primary precursor mixture to make the primary precursor mixture into a slurry state. In this case, the aggregation of the primary precursor mixture by the hydrogen reduction reaction can be eliminated, and the primary precursor mixture can be collected more easily in a slurry state.

[0094] For example, water can be injected into the fluidized bed reactor 100 through the upper inlet 108a, and the non-reactive gas can be injected into the fluidized bed reactor 100 through the gas inlet 104 located at the bottom of the fluidized bed reactor 100.

[0095] For example, the primary precursor mixture in slurry form can be collected through the outlet 108b located at the bottom of the fluidized bed reactor 100. The collected primary precursor mixture can be injected into the lithium precursor collection process described below.

[0096] According to some embodiments, the formed primary precursor mixture may not be collected separately from the fluidized bed reactor 100, but may be located inside the fluidized bed reactor 100, and the lithium precursor collection process described below may be carried out inside the fluidized bed reactor 100. In this case, the problem of loss of a portion of the primary precursor mixture during the transportation of the formed primary precursor mixture can be prevented. Therefore, the recovery rate of lithium precursors can be further improved.

[0097] According to an exemplary implementation, lithium precursors can be collected from a primary precursor mixture (e.g., process S40).

[0098] For example, the primary precursor mixture formed by the above-mentioned hydrogen reduction reaction can be reacted with the leachate to collect lithium precursors.

[0099] For example, the primary precursor mixture can react with the leachate to form a precipitate containing a solution of dissolved lithium precursors and transition metal precursor precipitates.

[0100] For example, lithium oxide can react with the leachate to form lithium hydroxide, and the formed lithium hydroxide can dissolve in the leachate.

[0101] In some embodiments, the leachate may contain water. In this case, the primary precursor mixture may be washed with water. Through this washing process, the primary precursor mixture reacts with water to form a lithium precursor in which lithium hydroxide is dissolved in water.

[0102] In some exemplary embodiments, the leachate may further contain dimethyl carbonate or diethyl carbonate.

[0103] For example, dimethyl carbonate or diethyl carbonate can promote the reaction of the primary precursor mixture with water. Therefore, the separation efficiency of lithium precursors can be improved.

[0104] In some embodiments, the precipitate may comprise a slurry containing a mixture of primary precursors.

[0105] For example, the slurry can be formed by dispersing particles containing transition metals that are insoluble in the leaching solution in the leaching solution. Therefore, the lithium precursor can be collected by separating the slurry from a solution containing the dissolved lithium precursor.

[0106] In some implementations, the precipitated particles containing transition metals can be collected to form transition metal precursors. For example, the particles containing transition metals can react with an acid solution to form transition metal precursors.

[0107] In an exemplary embodiment, the acid solution can be sulfuric acid. In this case, the transition metal precursor may comprise a transition metal sulfate. For example, the transition metal sulfate may comprise NiSO4, MnSO4, and CoSO4, etc.

[0108] The reaction between the primary precursor mixture and the leachate can be carried out inside the fluidized bed reactor 100 where the process for forming the positive electrode active material mixture 90 is performed. In this case, it is not necessary to collect each product separately after the process for forming the positive electrode active material mixture 90, the hydrogen reduction process, or the process for forming the primary precursor mixture, thereby minimizing the reduction in lithium precursor recovery rate that may occur during the transport of the products.

[0109] Figure 2 This is a schematic flowchart illustrating a method for recovering active metals from lithium secondary batteries according to some implementation schemes.

[0110] Reference Figure 2 In some embodiments, the positive electrode active material mixture 90 can be collected through a gas injection port 104 located at the bottom of the fluidized bed reactor 100, and the collected positive electrode active material mixture 90 can be added to a separate reduction reactor 200 and subjected to the above-described reduction process.

[0111] For example, the positive electrode active material mixture 90 can be injected into the reduction reactor 200 through the upper injection port 208a located at the top of the reduction reactor 200, and the hydrogen gas can be injected into the reactor body 210 through the gas injection port 204 located at the bottom of the reduction reactor 200.

[0112] For example, the expansion section 220 can be located at the top of the reduction reactor 200. The expansion section 220 can reduce the flow rate of the reducing gas injected from the bottom of the reduction reactor 200, thereby effectively preventing the positive electrode active material mixture 90 from leaking to the outside during the process of refluidizing the positive electrode active material mixture 90 located inside the reduction reactor 200.

[0113] In some embodiments, water and non-reactive gases may be injected into the reduction reactor 200 before collecting the primary precursor mixture to make the primary precursor mixture a slurry. In this case, the aggregation of the primary precursor mixture by the reduction reaction can be eliminated, and the primary precursor mixture can be collected more easily in a slurry state.

[0114] For example, water can be injected into the reduction reactor 200 through the upper inlet 208a, and the non-reactive gas can be injected into the reduction reactor 200 through the gas inlet 204 located at the bottom of the reduction reactor 200.

[0115] For example, the primary precursor mixture in slurry form can be collected through the outlet 208b located at the bottom of the reduction reactor 200. The collected primary precursor mixture can be injected into the lithium precursor collection process described above.

[0116] According to one embodiment, the formed primary precursor mixture may not be collected separately from the reduction reactor 200, but may be located inside the reduction reactor 200, and the above-mentioned process for collecting lithium precursors may also be carried out inside the reduction reactor 200.

[0117] In this case, there is no need to collect each product separately after the process of forming the primary precursor mixture, thereby preventing a decrease in lithium precursor recovery rate that may occur during the transportation of the products.

[0118] The following experimental examples, including specific embodiments and comparative examples, are presented to aid in understanding the present invention. However, these are merely illustrative of the invention and not intended to limit the scope of the claims. Various changes and modifications can be made to the embodiments within the scope of the invention and its technical concept, which will be obvious to those skilled in the art, and such changes and modifications also fall within the scope of the claims.

[0119] Example 1

[0120] 1 kg of positive electrode material separated from waste lithium secondary batteries is cut into small units and pulverized by grinding to obtain a primary positive electrode active material mixture containing Li-Ni-Co-Mn oxide, binder (polyvinylidene fluoride, PVDF) and conductive material (carbon black) (process S10).

[0121] 0.2 kg of the obtained primary positive electrode active material mixture is injected into a fluidized bed reactor, and a mixture of 20% by volume oxygen and 80% by volume nitrogen is injected from the bottom of the reactor to fluidize the primary positive electrode active material mixture. The internal temperature of the fluidized bed reactor is raised from 20°C to 500°C and maintained at 500°C for 3 hours, thereby removing the binder contained in the primary positive electrode active material mixture by thermal decomposition and combustion of the conductive material, thus forming the positive electrode active material mixture (process S20).

[0122] A mixture of 20% by volume hydrogen and 80% by volume nitrogen is injected through a gas inlet located at the bottom of the fluidized bed reactor for 4 hours to fluidize the mixture in the reactor and react with the hydrogen to form a primary precursor mixture containing lithium hydroxide. During this time, the internal temperature of the fluidized bed reactor is maintained at 460°C (process S30).

[0123] Water and nitrogen are added to the formed primary precursor mixture to form a slurry-like primary precursor mixture. The slurry-like primary precursor mixture is collected and further washed with water to obtain an aqueous lithium precursor solution (process S40).

[0124] Example 2

[0125] Except that the heat treatment temperature is set to 650°C in the heat treatment process of the primary positive electrode active material mixture used to prepare the positive electrode active material mixture, the lithium precursor aqueous solution is obtained by the same method as in Example 1.

[0126] Comparative Example 1

[0127] Except that the heat treatment process of the primary positive electrode active material mixture is not performed when preparing the positive electrode active material mixture, the lithium precursor aqueous solution is obtained by the same method as in Example 1.

[0128] Comparative Example 2

[0129] Except that the heat treatment process for the primary positive electrode active material mixture used to prepare the positive electrode active material mixture is carried out by using a separate combustion furnace instead of a fluidized bed reactor, and then the resulting positive electrode active material mixture is added to the fluidized bed reactor and subjected to a hydrogen reduction reaction, the lithium precursor aqueous solution is obtained by the same method as in Example 1.

[0130] Comparative Example 3

[0131] Except that in the heat treatment process of the primary positive electrode active material mixture used to prepare the positive electrode active material mixture, only nitrogen (a non-reactive gas) without oxygen is used instead of oxygen-containing gas for fluidization, the lithium precursor aqueous solution is obtained by the same method as in Example 1.

[0132] Experimental Example

[0133] (1) Measurement of temperature change deviation

[0134] The deviation between the minimum and maximum temperatures during the reaction process is calculated by measuring the internal temperature of the fluidized bed reactor.

[0135] (2) Measurement of average diameter

[0136] The diameter of the positive electrode active material mixture particles was measured using a Mastersizer 3000 laser diffraction scattering device from Malvern.

[0137] (3) Measurement of particle size distribution range

[0138] The positive electrode active material mixture particles were ultrasonically treated in an aqueous medium to ensure thorough dispersion, and the results were measured using a Malvern Mastersizer 3000 laser diffraction scattering device.

[0139] (4) Measurement of adhesive removal rate

[0140] The binder removal rate is measured by measuring the mass of binder contained in the positive electrode active material mixture relative to the mass of binder contained in the primary positive electrode active material mixture.

[0141] (5) Measurement of conductive material removal rate

[0142] The conductive material removal rate is measured by measuring the mass of conductive material contained in the positive electrode active material mixture relative to the mass of conductive material contained in the primary positive electrode active material mixture.

[0143] (6) Evaluate whether lithium carbonate (Li2CO3) is formed.

[0144] The obtained slurry-state primary precursor mixture aqueous solution was further mixed with 19 times (by weight) of water and stirred. The formation of lithium carbonate was then evaluated by measuring the weight of carbonate ions dissolved in the water.

[0145] (7) Measurement of lithium precursor recovery rate

[0146] The obtained slurry-state primary precursor mixture aqueous solution was further mixed with 19 times (by weight) of water and stirred. The lithium precursors dissolved in the water were then recovered from lithium hydroxide and lithium carbonate. The recovery rate of the lithium precursors was calculated by measuring the weight of lithium dissolved in the water relative to the weight of lithium in the initial positive electrode active material sample.

[0147] (8) Measurement of selectivity of lithium carbonate (Li2CO3)

[0148] The weight of 19 times the amount of water (based on weight) was added to the obtained slurry-state primary precursor mixture aqueous solution and stirred. The weight of carbonate ions dissolved in the water was then measured, and the proportion of lithium carbonate generated in the recovered lithium precursor was calculated.

[0149] For the above embodiments and comparative examples, the maximum deviation of the internal temperature change of the fluidized bed reactor, the average diameter of the particles of the formed positive electrode active material mixture, the particle size distribution, the binder removal rate, the conductive material removal rate, whether by-products (Li2CO3) are generated, and the selectivity of lithium carbonate, which were measured in the process of preparing the primary positive electrode active material mixture, are recorded in Table 1.

[0150] In addition, the maximum deviation of the internal temperature change of the reduction reactor during the reduction process and the recovery rate of the lithium precursor after water washing were measured and recorded in Table 1.

[0151] [Table 1]

[0152]

[0153] Referring to Table 1, in Example 1, an excellent recovery rate of lithium precursors was achieved by performing a fluidized bed thermal treatment process to remove binders and conductive materials contained in the primary cathode active material mixture, and the generation of byproducts such as lithium carbonate was reduced in the reduction process.

[0154] Furthermore, in Example 2, where a heat treatment process for preparing a primary cathode active material mixture was carried out at 650°C, lithium carbonate was generated as a byproduct due to side reactions at high temperatures, thus reducing the recovery rate of lithium precursors in the lithium precursor recovery process.

[0155] However, in Comparative Example 1, which did not undergo a thermal decomposition process, side reactions (e.g., over-reduction of the positive electrode active material mixture) occurred during the hydrogen reduction process due to the heat of decomposition generated by the decomposition of the binder, and the resulting metal active material mixture aggregated. Therefore, the over-reduced metal active material mixture was difficult to convert into a slurry state. Consequently, the recovery rate of the lithium precursor decreased.

[0156] Furthermore, in Comparative Example 2, where a non-fluidized heat treatment process was performed in a separate combustion furnace prior to the reduction process, the resulting positive electrode active material mixture agglomerated due to side reactions (e.g., over-reduction) during the thermal decomposition process, forming aggregates with a diameter of 5 cm. Consequently, the positive electrode active material mixture was difficult to fluidize, leading to a decrease in the reduction rate of the hydrogen reduction process and thus a decrease in the recovery rate of the lithium precursor.

[0157] In Comparative Example 3, where only a non-reactive gas (N2) without oxygen was injected instead of a gas containing oxygen, lithium carbonate was generated as a byproduct during the hydrogen reduction process because the conductive material was not removed. Therefore, the mixed content of lithium hydroxide in the primary precursor mixture decreased, resulting in a slight decrease in the recovery rate of the lithium precursor. Furthermore, lithium carbonate is insoluble in the leachate, thus requiring a separate subsequent filtration process, which reduces the economics and long-term operability of the process.

[0158] In Comparative Examples 1 and 2, the conductive material was not removed, resulting in the formation of lithium carbonate as a byproduct. Therefore, as in Comparative Example 3, the recovery rate of the lithium precursor was reduced, and the economics and long-term operability of the process were also reduced.

Claims

1. A method for recovering active metals from lithium secondary batteries, comprising the following steps: A mixture of primary positive electrode active materials is prepared from the positive electrode of a waste lithium secondary battery; The primary positive electrode active material mixture is fluidized in a fluidized bed reactor by passing an oxygen-containing gas to form a positive electrode active material mixture. Injecting a reducing gas into the fluidized bed reactor to form a primary precursor mixture from the positive electrode active material mixture; and The lithium precursor is recovered from the primary precursor mixture. The steps of fluidizing the primary positive electrode active material mixture with the oxygen-containing gas and forming the primary precursor mixture are carried out continuously in the fluidized bed reactor.

2. The method for recovering active metals from lithium secondary batteries according to claim 1, wherein, The positive electrode includes: a positive electrode current collector; and a positive electrode active material layer, the positive electrode active material layer being formed on the positive electrode current collector and comprising a binder, a conductive material, and the positive electrode active material. The step of preparing the primary positive electrode active material mixture includes removing the positive electrode current collector from the positive electrode. The primary positive electrode active material mixture includes the binder, the conductive material, and the positive electrode active material.

3. The method for recovering active metals from lithium secondary batteries according to claim 2, wherein, The step of fluidizing the primary positive electrode active material mixture with the oxygen-containing gas includes decomposing or burning the binder and the conductive material in the fluidized bed reactor.

4. The method for recovering active metals from lithium secondary batteries according to claim 1, wherein, The oxygen-containing gas includes oxygen (O2) and non-reactive gases. The non-reactive 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 4, wherein, The volume ratio of oxygen relative to the total volume of the oxygen-containing gas is 10-30% by volume, and the volume ratio of the non-reactive gas is 70-90% by volume.

6. The method for recovering active metals from lithium secondary batteries according to claim 1, wherein, The step of fluidizing the primary positive electrode active material mixture with the oxygen-containing gas is carried out at a temperature of 100-600°C.

7. The method for recovering active metals from lithium secondary batteries according to claim 6, wherein, The step of fluidizing the primary positive electrode active material mixture with the oxygen-containing gas includes heating from a temperature below 50°C to a target temperature in the range of 400-600°C for 1-2 hours.

8. The method for recovering active metals from lithium secondary batteries according to claim 7, wherein, The step of fluidizing the primary positive electrode active material mixture with the oxygen-containing gas includes heat treatment at the target temperature for 2-5 hours.

9. The method for recovering active metals from lithium secondary batteries according to claim 1, wherein, The reducing gas contains hydrogen.

10. The method for recovering active metals from lithium secondary batteries according to claim 9, wherein, The step of forming the primary precursor mixture is carried out at a temperature in the range of 400-500°C.

11. The method for recovering active metals from lithium secondary batteries according to claim 1, wherein, The steps of fluidizing the primary positive electrode active material mixture with the oxygen-containing gas and forming the primary precursor mixture are performed in situ.

12. The method for recovering active metals from lithium secondary batteries according to claim 9, wherein, The primary precursor mixture comprises primary lithium precursor particles and particles containing transition metals. The particles containing transition metals include Ni, Co, NiO, CoO, and MnO.

13. The method for recovering active metals from lithium secondary batteries according to claim 12, wherein, The primary lithium precursor particles comprise at least one of lithium hydroxide, lithium oxide, or lithium carbonate.

14. The method for recovering active metals from lithium secondary batteries according to claim 13, wherein, The step of recovering the lithium precursor includes washing the primary lithium precursor particles with water to collect the lithium hydroxide.

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