Fluidized bed reactor and method for recovering active metals from lithium secondary batteries using the same

Abstract

A method for recovering active metals from lithium secondary batteries according to an embodiment of the present invention includes preparing a spent positive electrode active material mixture obtained from spent positive electrodes of the lithium secondary batteries, reacting the spent positive electrode active material mixture with a reaction gas in a fluidized bed reactor to form a primary precursor mixture, and selectively recovering a lithium precursor from the primary precursor mixture. The fluidized bed reactor includes a reactor body and a horizontal expanded bed, wherein the ratio of the diameter of the horizontal expanded bed to the diameter of the reactor body is 3 or greater, thereby improving the recovery efficiency of the lithium secondary batteries.

Description

Technical Field

[0001] The present invention relates to a method for recovering active metals from lithium secondary batteries. More specifically, the present invention relates to a method for recovering active metals from lithium secondary batteries using a fluidized bed reactor. Background Art

[0002] Recently, secondary batteries have been widely used as power sources for mobile electronic devices such as camcorders, mobile phones, and laptop computers, as well as vehicles such as electric vehicles and hybrid vehicles. Lithium secondary batteries have attracted much attention among secondary batteries due to their advantages, such as high operating voltage, high energy density per unit weight, high charging rate, and compact size.

[0003] Lithium metal oxides can be used as active materials for positive electrodes of lithium secondary batteries. Lithium metal oxides may further contain transition metals such as nickel, cobalt, and manganese.

[0004] Since these high-cost precious metals are used in the positive electrode active material, the production of the positive electrode material requires more than 20% of the production cost. In addition, due to the recent attention paid to environmental protection, the recycling method of the positive electrode active material is being studied.

[0005] Conventionally, a method for sequentially recovering valuable metals by leaching spent positive electrode active material in a strong acid such as sulfuric acid has been used. However, wet methods can be disadvantageous in terms of regeneration selectivity and regeneration time, and can cause environmental pollution. Therefore, methods for recovering valuable metals using dry reactions by contact with a reaction gas are being studied.

[0006] However, as the size of active material particles supplied for dry reactions becomes smaller, non-uniform reactions may occur due to aggregation. In addition, the recovery rate of the active material may be reduced due to local non-uniform supply of reaction gas in the reactor.

[0007] For example, Korean Registered Patent Publication No. 10-0709268 discloses an apparatus and method for recycling waste manganese batteries and alkaline batteries, but does not provide a dry method for regenerating valuable metals with high selectivity and high yield. Summary of the Invention

[0008] [Technical Goals]

[0009] According to one aspect of the present invention, a method for recovering active metals of a lithium secondary battery with improved recovery efficiency is provided.

[0010] [Technical means]

[0011] In a method for recovering active metals from lithium secondary batteries, a spent positive electrode active material mixture is prepared from spent positive electrodes of the lithium secondary batteries. The spent positive electrode active material mixture is reacted with a reaction gas in a fluidized bed reactor to form a primary precursor mixture. A lithium precursor is selectively recovered from the primary precursor mixture. The fluidized bed reactor includes a reactor body and a horizontal expanded bed, wherein the ratio of the diameter of the horizontal expanded bed to the diameter of the reactor body is 3 or greater.

[0012] In some embodiments, forming the primary precursor mixture may include lowering the spent positive active material mixture or the primary precursor mixture ascending from the reactor body to the horizontal expanded bed by the reaction gas to be collected in the reactor body.

[0013] In some embodiments, the ratio of the diameter of the horizontal expanded bed relative to the diameter of the reactor body may be 3 to 10.

[0014] In some embodiments, the fluidized bed reactor may further include a vertical expansion pipe connecting the reactor body and the horizontal expanded bed.

[0015] In some embodiments, the inclination angle of the vertical expansion tube may be 45° to 80°.

[0016] In some embodiments, the reactant gas may include hydrogen.

[0017] In some embodiments, when recovering the lithium precursor, the primary precursor mixture may be washed with water.

[0018] A fluidized bed reactor according to an embodiment of the present invention includes a reactor body; a horizontal expanded bed connected to the reactor body, the diameter of the horizontal expanded bed being at least three times the diameter of the reactor body; a vertical expansion pipe connecting the reactor body and the horizontal expanded bed; and a gas injection path for injecting reaction gas into the reactor body.

[0019] [Effects of the Invention]

[0020] In the method for recovering active metals from lithium secondary batteries according to an exemplary embodiment, a fluidized bed reactor in which the ratio of the diameter of the horizontal expanded bed to the diameter of the reactor body is 3 or greater can be used to prevent the primary precursor mixture from leaking to the outside or accumulating on the wall surface during the formation of the primary precursor mixture. The injection rate of the reaction gas injected into the fluidized bed reactor can be increased, thereby making it easier to form the fluidized bed and thus improving the recovery efficiency of the lithium precursor.

[0021] In a method for recovering active metals from lithium secondary batteries according to an exemplary embodiment, a fluidized bed reactor including a vertical expansion tube having a specific inclination angle can be used to reduce the amount of a primary precursor mixture leaking to the outside. Furthermore, the primary precursor mixture can be guided back into the reactor body along the inclined surface of the vertical expansion tube to improve the recovery efficiency of the lithium precursor. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 is a schematic diagram for describing a fluidized bed reactor and a method of recovering active metals of a lithium secondary battery using the fluidized bed reactor according to an exemplary embodiment. DETAILED DESCRIPTION

[0023] An embodiment of the present invention provides a method for recovering active metals with high purity and high yield using a fluidized bed reactor in which the ratio of the diameter of a horizontal expanded bed relative to the diameter of a reactor body is 3 or more.

[0024] 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.

[0025] 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.

[0026] Reference Figure 1 , the spent positive electrode active material mixture may be prepared from the spent positive electrode of the lithium secondary battery (eg, in the process of S10 ).

[0027] A lithium secondary battery may include an electrode assembly including a positive electrode, a negative electrode, and a separator layer interposed between the positive electrode and the negative electrode. The positive electrode and the negative electrode may 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.

[0028] For example, the positive electrode active material included in the positive electrode active material layer may include an oxide containing lithium and a transition metal.

[0029] In some embodiments, the positive active material may include a compound represented by the following Chemical Formula 1.

[0030] [Chemical Formula 1]

[0031] Li x M1 a M2 b M3 c O y

[0032] In Chemical Formula 1, M1, M2, and M3 can each be a transition metal 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, 0 < x ≤ 1.1, 2 ≤ y ≤ 2.02, 0 < a < 1, 0 < b < 1, 0 < c < 1, and 0 < a + b + c ≤ 1.

[0033] In some embodiments, the positive electrode active material can be an NCM-based lithium oxide including nickel, cobalt, and manganese.

[0034] The waste positive electrode can be recovered by separating the positive electrode from the waste lithium secondary battery. The waste positive electrode can include the 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 can include a conductive material, an adhesive, and the positive electrode active material as described above.

[0035] The conductive material can include, for example, a carbon-based material such as graphite, carbon black, graphene, and carbon nanotubes. The adhesive can include a resin material such as polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinylidene fluoride (PVDF), polyacrylonitrile, polymethyl methacrylate, etc.

[0036] In an exemplary embodiment, the recovered waste positive electrode can be pulverized to produce a waste positive electrode active material mixture. Accordingly, the waste positive electrode active material mixture can be prepared in a powder form. As described above, the waste positive electrode active material mixture can include powders of lithium-transition metal oxides such as powders of NCM-based lithium oxides (e.g., Li(NCM)O2).

[0037] The term "waste positive electrode active material mixture" used in the present application can refer to the raw material input into the fluidized bed reaction treatment described later after the positive electrode current collector is substantially removed from the waste positive electrode. In one embodiment, the waste positive electrode active material mixture can include positive electrode active material particles such as NCM-based lithium oxides. In one embodiment, the waste positive electrode active material mixture can include component parts derived from the adhesive or the conductive material. In one embodiment, the waste positive electrode active material mixture can consist essentially of positive electrode active material particles.

[0038] In some embodiments, the average particle size (D50) of the waste positive electrode active material mixture can be 5 μm to 100 μm. Within the above range, the lithium-transition metal oxides to be recovered such as Li(NCM)O2 can be easily separated from the positive electrode current collector, the conductive material, and the adhesive contained in the waste positive electrode active material mixture.

[0039] In some embodiments, the spent positive electrode active material mixture may be heat treated before being introduced into the fluidized bed reactor described below. This heat treatment can substantially remove or reduce impurities such as conductive materials and binders contained in the spent positive electrode active material mixture, thereby allowing the lithium-transition metal oxide to be introduced into the fluidized bed reactor at a high purity.

[0040] The temperature of the heat treatment may be, for example, about 100° C. to 500° C., preferably about 350° C. to 450° C. Within the above range, impurities may be substantially removed while preventing the lithium-transition metal oxide from decomposing and breaking.

[0041] For example, during S20 , the spent positive electrode active material mixture may react with the reaction gas in the fluidized bed reactor 100 to form the primary precursor mixture 80 .

[0042] like Figure 1 As shown, the fluidized bed reactor 100 may be divided into a reactor body 110, a lower reactor section 120, and a horizontal expanded bed 130. The reactor body 110 may include a heating means such as a heater or may be integrated with a heating means such as a heater.

[0043] A lower portion below the dispersion plate 50 in the reactor body 110 may be defined as a lower reactor portion 120 .

[0044] The spent positive electrode active material mixture can be supplied to the reactor body 110 through the supply flow path 108a. The spent positive electrode active material mixture can be dripped through the supply flow path 108a connected to the upper portion of the reactor body 110. In one embodiment, the spent positive electrode active material mixture can also be introduced through a supply flow path (not shown) connected to the lower portion of the reactor body 110.

[0045] The reaction gas for converting the spent positive active material mixture into the primary precursor can be supplied to the reactor body 110 through the gas flow path 104 connected to the lower reactor part 120. In an exemplary embodiment, the reaction gas may include a reducing gas. For example, hydrogen (H2) can be supplied.

[0046] The reaction gas may be discharged into the reactor body 110 through the injection column 60 included in the dispersion plate. The reaction gas may be supplied from the bottom of the fluidized bed reactor 100 to contact the spent positive electrode active material mixture, so that the spent positive electrode active material mixture may react with the reaction gas while moving to the horizontal expanded bed 130 to be converted into the primary precursor mixture 80.

[0047] For example, the ratio of the diameter of the horizontal expanded bed 130 to the diameter of the reactor body 110 may be 3 or more. Preferably, the diameter ratio may be 3 to 10, and more preferably, the diameter ratio may be 3 to 5.

[0048] The diameter can be measured based on the central axis of the fluidized bed reactor 100 and the inner wall of the fluidized bed reactor 100. In this case, the flow rate of the primary precursor mixture 80 or the reaction gas moving from the reactor body 110 to the horizontal expanded bed 130 can be rapidly reduced. Therefore, the moving speed of the primary precursor mixture 80 can be less than the terminal speed (u t ), thereby effectively reducing the amount of the primary precursor mixture 80 leaking from the reactor body 110.

[0049] For example, the ratio of the diameter of the horizontal expanded bed 130 to the diameter of the reactor body 110 may be 3 to 10. For example, if the diameter ratio is less than 3, the diameter of the horizontal expanded bed 130 of the fluidized bed reactor 100 may not be sufficiently increased, and a sufficient velocity reduction effect may not be achieved. If the diameter ratio exceeds 10, the size of the horizontal expanded bed 130 may be excessively increased, thereby reducing the overall process efficiency.

[0050] For example, the fluidized bed reactor 100 may further include a vertical expansion pipe 140 connecting the reactor body 110 and the horizontal expanded bed 130. The vertical expansion pipe 140 may refer to a region in which the diameter of the vertical expansion pipe 140 gradually increases at a constant inclination angle (a) as the diameter of the horizontal expanded bed 130 increases relative to the diameter of the reactor body 110. For example, the inclination angle (a) may be defined as the angle formed between a vertical extension line relative to the side surface of the reactor body 110 and the inclined surface of the vertical expansion pipe 140.

[0051] For example, the inclination angle (a) of the vertical expansion pipe 140 may be approximately 45° to 80°. More preferably, the inclination angle (a) of the vertical expansion pipe 140 may be approximately 60° to 80°. For example, within the inclination angle range, effective velocity reduction of the primary precursor mixture 80 may be achieved without increasing the area of ​​the horizontal expanded bed 130 included in the fluidized bed reactor 100.

[0052] Furthermore, the descending primary precursor mixture 80 having a reduced velocity may be reintroduced into the reactor body 110 along the inclined surface of the vertical expansion tube 140 , thereby further improving the recovery efficiency of the lithium precursor.

[0053] In some exemplary embodiments, the fluidized bed reactor 100 may include a gas injection path 104 for injecting a reaction gas into the reactor body 110 .

[0054] The reaction gas may be injected into the reactor body 110 by sequentially passing through the gas injection path 104 , the bottom plate 50 , and the injection column 60 .

[0055] In some embodiments, the lithium-transition metal oxide can be reduced by hydrogen to produce a primary lithium precursor including, for example, lithium hydroxide (LiOH), a lithium oxide (e.g., LiO 2 ), and a transition metal or transition metal oxide. For example, Ni, Co, NiO, CoO, and MnO can be produced together with the primary lithium precursor by a reduction reaction.

[0056] The reduction reaction in the reactor body 110 may be performed at a temperature of about 400° C. to 700° C., preferably 450° C. to 550° C. Within the reaction temperature range, the reduction reaction may be promoted without causing reaggregation and recombination of the primary lithium precursor and the transition metal / transition metal oxide.

[0057] In some embodiments, a carrier gas may be supplied together with the reaction gas from the lower reactor section 120. For example, the carrier gas may be supplied together with the reaction gas through the gas flow path 104. For example, the carrier gas may include an inert gas such as nitrogen (N2) or argon (Ar). The carrier gas may also be discharged and supplied through the injection column 60 of the dispersion plate to promote the formation of the fluidized bed. For example, the formation of a cyclone may be promoted by the carrier gas.

[0058] A primary precursor mixture 80 including a primary lithium precursor and a primary transition metal precursor (eg, a transition metal or transition metal oxide) may be formed in the reactor body 110. The primary lithium precursor may include, for example, lithium hydroxide, lithium oxide, and / or lithium carbonate.

[0059] For example, it is possible to cool the primary precursor mixture 80. In this case, the primary precursor mixture 80 may be cooled using a gaseous refrigerant or a liquid refrigerant.

[0060] For example, the primary precursor mixture 80 may be cooled to below about 100° C. More preferably, the primary precursor mixture 80 may be cooled to a temperature in the range of about 50° C. to 100° C. For example, if the primary precursor mixture 80 is cooled to the above temperature range, when the lithium precursor is recovered, the recovery efficiency of the lithium precursor may be improved, as will be described later.

[0061] The lithium precursor may be selectively recovered from the cooled primary precursor mixture 80 (eg, during S30 ).

[0062] In some embodiments, the cooled primary precursor mixture 80 can be washed with water. Primary lithium precursor particles in the form of lithium hydroxide (LiOH) can be substantially dissolved in water by the washing process, separated from the transition metal precursor, and recovered in advance. A lithium precursor consisting essentially of lithium hydroxide can be obtained by a crystallization process, such as dissolving lithium hydroxide in water.

[0063] In one embodiment, the primary lithium precursor particles in the form of lithium oxide and lithium carbonate may be substantially removed by the washing process. In one embodiment, the primary lithium precursor particles in the form of lithium oxide and lithium carbonate may be at least partially converted into lithium hydroxide by the washing process.

[0064] In some embodiments, the primary lithium precursor can be reacted with a carbon-containing gas such as carbon monoxide (CO), carbon dioxide (CO2), etc. to obtain lithium carbonate (e.g., Li2CO3) as a lithium precursor. A crystalline lithium precursor can be obtained by reacting with the carbon-containing gas. For example, lithium carbonate can be collected by injecting a carbon-containing gas during the washing process.

[0065] In some embodiments, the transition metal precursor can be obtained from a primary transition metal precursor (eg, during S40 ).

[0066] For example, the primary lithium precursor may be collected from outlet 108b, and the primary transition metal precursor may then be recovered. Thereafter, the primary transition metal precursor may be treated with an acid solution to form an acid salt form of each transition metal.

[0067] In one embodiment, sulfuric acid can be used as the acid solution. In this case, NiSO4, MnSO4 and CoSO4 can each be recovered as a transition metal precursor.

[0068] As described above, the lithium precursor can be collected through a dry process, and then the transition metal precursor can be selectively extracted using an acid solution, thereby improving the purity and selectivity of each metal precursor, reducing the load of the wet process, and reducing the amount of wastewater and by-products.

[0069] Hereinafter, preferred embodiments are presented to more specifically describe the present invention. However, the following examples are provided merely to illustrate the present invention, and those skilled in the relevant art will clearly understand that these examples do not limit the appended claims, but rather 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.

[0070] Example 1

[0071] 100 kg of cathode material separated from waste lithium secondary batteries was heat-treated at 450° C. for 1 hour. The heat-treated cathode material was cut into small units and ground to obtain a sample of Li-Ni-Co-Mn oxide cathode active material.

[0072] 10 kg of the positive electrode active material sample was placed in a fluidized bed reactor in which the ratio of the diameter of the horizontal expanded bed to the diameter of the reactor body was 4. Nitrogen was injected from the bottom of the reactor at a flow rate of 100 L / min. The temperature inside the reactor was maintained at 450°C.

[0073] The amount of the positive electrode active material leaked to the outside of the reactor was measured, and the result of calculating the leakage amount per hour is shown in Table 1 below.

[0074] Examples 2 to 3 and Comparative Example 1

[0075] The amount of positive active material leaked to the outside of the reactor was measured by the same method as in Example 1 except that the ratio of the diameter of the horizontal expanded bed to the diameter of the reactor body was adjusted as shown in Table 1, and the leakage amount per hour was calculated.

[0076] [Table 1]

[0077]

[0078] Referring to Table 1, when the ratio of the diameter of the horizontal expanded bed to the diameter of the reactor body is 3 or more, the amount of the positive electrode active material flowing out of the reactor decreases.

[0079] [Explanation of Reference Numerals]

[0080] 50: bottom plate 60: injection column

[0081] 80: Primary precursor mixture 100: Fluidized bed reactor

[0082] 104: Gas flow path 110: Reactor body

[0083] 120: Lower reactor section 130: Horizontal expanded bed

[0084] 140: Vertical expansion pipe a: Inclination

Claims

1. A method for recovering active metals from a lithium secondary battery, comprising: preparing a waste positive electrode active material mixture obtained from waste positive electrodes of lithium secondary batteries; forming a primary precursor mixture by reacting the spent positive electrode active material mixture with a reaction gas in a fluidized bed reactor; and selectively recovering a lithium precursor from the primary precursor mixture, The fluidized bed reactor comprises a reactor body, a horizontal expanded bed, and a vertical expansion pipe connecting the reactor body and the horizontal expanded bed, and the ratio of the diameter of the horizontal expanded bed to the diameter of the reactor body is 3 to 5. The inclination angle of the vertical expansion pipe is 45° to 80°.

2. The method for recovering active metals from lithium secondary batteries according to claim 1, wherein the forming of the primary precursor mixture comprises lowering the spent positive electrode active material mixture or the primary precursor mixture that is raised from the reactor body to the horizontal expanded bed by the reaction gas to be collected in the reactor body. 3 . The method for recovering active metals of a lithium secondary battery according to claim 1 , wherein the reaction gas comprises hydrogen. 4 . The method for recovering active metals of lithium secondary batteries according to claim 1 , wherein the recovering of the lithium precursor comprises washing the primary precursor mixture with water.

5. A fluidized bed reactor comprising: Reactor body; a horizontal expanded bed connected to the reactor body, wherein the diameter of the horizontal expanded bed is three to five times the diameter of the reactor body; a vertical expansion pipe connecting the reactor body and the horizontal expanded bed; and a gas injection path for injecting reaction gas into the reactor body, The inclination angle of the vertical expansion pipe is 45° to 80°.

Images