Classifier for positive electrode active material and method for regenerating lithium precursor using the same

Abstract

In the lithium precursor regeneration method, an active material powder containing lithium composite oxide particles and a positive electrode active material mixture containing dust particles are prepared. The dust particles are separated from the positive electrode active material mixture using a classifier, and the active material powder is collected. The active material powder is subjected to a reduction treatment to form a pre-precursor mixture. The lithium precursor is recovered from the pre-precursor mixture. A high-purity, high-yield lithium precursor can be obtained.

Description

[Technical field]

[0001] The present invention relates to a classifier for positive electrode active materials and a method for regenerating lithium precursors using the same, and more particularly to a classifier for positive electrode active materials and a method for regenerating lithium precursors from waste lithium-containing compounds using the same. [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 accounts for more than 20% of the manufacturing cost. In addition, in recent years, as interest in environmental protection has increased, research into methods for recycling positive electrode active materials 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. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Korean Patent Publication No. 2015-0002963 Summary of the Invention [Problem to be solved by the invention]

[0009] An object of the present invention is to provide a classifier for recovering a lithium precursor with high purity and in high yield from a lithium-containing compound, and a method for regenerating a lithium precursor using the same. [Means for solving the problem]

[0010] In a method for regenerating a lithium precursor according to an embodiment of the present invention, an active material powder including lithium composite oxide particles and a positive active material mixture including dust particles are prepared. The dust particles are separated from the positive active material mixture using a classifier to collect the active material powder. The active material powder is reduced to form a preliminary precursor mixture. The lithium precursor is recovered from the preliminary precursor mixture.

[0011] In an exemplary embodiment, the dust particles can include particles derived from the carbon-based conductive material and the binder.

[0012] In an exemplary embodiment, collecting the active material powder can include classifying the active material powder into a first active material powder and a second active material powder, which are then collected separately.

[0013] In one exemplary embodiment, the average particle size of the second active material powder may be smaller than the average particle size of the first active material powder.

[0014] In an exemplary embodiment, the collected first active material powder may be reduced to form a pre-precursor mixture, and the collected second active material powder may be acid solution treated.

[0015] In an exemplary embodiment, the separation of the dust particles and the classification of the first and second active material powders can occur together in the classifier.

[0016] In an exemplary embodiment, the reduction process of the active material powder can be carried out in a fluidized bed reactor using a reducing reactant gas.

[0017] In an exemplary embodiment, recovering the lithium precursor from the pre-precursor mixture may include washing the pre-precursor mixture with water.

[0018] In an exemplary embodiment, a classifier for a positive electrode active material may include an active material inlet into which a positive electrode active material mixture including an active material powder including lithium composite oxide particles and dust particles is inject|poured, a classifying body including a classifying sieve which classifies the positive electrode active material mixture into a first active material powder and a second active material powder, an upper discharge outlet located at an upper part of the classifying body and through which the dust particles in the positive electrode active material mixture are scattered and discharged, an active material discharge outlet connected to a center part of the classifying body and through which the first active material powder is discharged, and a lower discharge outlet connected to a lower part of the classifying body and through which the second active material powder in the positive electrode active material mixture is discharged.

[0019] In an exemplary embodiment, the classification body may further include a fluid inlet located at a lower portion thereof and through which a fluid is injected. Effect of the Invention

[0020] According to the above exemplary embodiment, the classifier can be used to separate dust particles from the positive active material mixture, and an active material powder including lithium composite oxide particles can be collected. In this case, the active material powder has excellent efficiency in the reduction process, and a lithium precursor with high yield and purity can be more easily obtained.

[0021] In some embodiments, the dust particles may include particles derived from a carbon-based conductive material and a binder. In this case, the carbon-based particles are separated from the positive electrode active material mixture, and an active material powder having a low concentration of carbon-based particles may be collected. This minimizes side reactions that may occur during the reduction process, and further improves the recovery rate of the lithium precursor.

[0022] In some embodiments, the active material powder can be separated into a first active material powder and a second active material powder having a smaller average particle size than the first active material powder, in which case only the first active material powder having a relatively larger average particle size can be made fluidizable.

[0023] Thereby, the lithium precursor can be recovered from the first active material powder by a reduction reaction, and the lithium precursor can be recovered from the second active material powder by an acid treatment step. [Brief description of the drawings]

[0024] [Figure 1] FIG. 1 is a schematic flow chart illustrating a method for regenerating a lithium precursor according to an exemplary embodiment. [Diagram 2] FIG. 2 is a schematic cross-sectional view for explaining a classifier according to an exemplary embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0025] An embodiment of the present invention provides a method for regenerating a lithium precursor with high purity and high efficiency using an active material powder in which dust particles have been removed from a positive electrode active material mixture using a classifier.

[0026] 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.

[0027] As used herein, the term "precursor" is used to collectively refer to a compound containing a specific metal to provide the specific metal contained in the positive electrode active material.

[0028] FIG. 1 is a schematic flow chart illustrating a method for regenerating a lithium precursor according to an exemplary embodiment.

[0029] According to an exemplary embodiment, a positive electrode active material mixture may be prepared that includes an active material powder including a lithium composite oxide and dust particles. The positive electrode active material mixture may include a lithium-containing compound obtained or regenerated from an electric element, a chemical element, etc. The positive electrode active material mixture may include various lithium-containing compounds, such as lithium oxide, lithium carbonate, and lithium hydroxide, as non-limiting examples.

[0030] According to an exemplary embodiment, the positive electrode active material mixture may include active material powder and dust particles obtained from waste lithium secondary batteries (eg, step S10).

[0031] The waste 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, and the positive electrode and the negative electrode may include 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.

[0032] 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.

[0033] In some embodiments, the positive electrode active material may include a lithium composite oxide represented by the following Chemical Formula 1:

[0034] [Chemical formula 1] Li x M1 a M2 b M3 c O y

[0035] In Chemical Formula 1, M1, M2, and M3 may 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. <x≦1.1、2≦y≦2.2、0<a<1、0<b<1、0<c<1、0<a+b+c≦1であってもよい。

[0036] In some embodiments, the positive electrode active material can include an NCM-based lithium composite oxide that includes nickel, cobalt, and manganese. The NCM-based lithium composite oxide can be prepared by reacting a lithium precursor and an NCM precursor (e.g., an NCM oxide) together, for example, by a co-precipitation reaction.

[0037] However, the embodiment of the present invention can be commonly applied not only to the cathode material containing the NCM-based lithium composite oxide, but also to the cathode material of lithium-containing lithium composite oxide.

[0038] For example, the positive electrode can be separated from the used lithium secondary battery to recover the used positive electrode. 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.

[0039] 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.

[0040] The carbon-based conductive material may include, for example, a carbon-based material such as graphite, carbon black, graphene, carbon nanotubes, etc. The binder may include, for example, a resin material such as vinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinylidene fluoride (PVDF), polyacrylonitrile, polymethylmethacrylate, etc.

[0041] A positive electrode active material mixture can be prepared from the recovered positive electrode. In some embodiments, the positive electrode active material mixture can be manufactured into a powder form by a physical method such as a grinding process. The positive electrode active material mixture can include an active material powder including lithium composite oxide particles derived from the positive electrode active material. For example, the lithium composite oxide particles can include an NCM-based lithium oxide powder (e.g., Li(NCM)O2).

[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 positive electrode active material mixture can be obtained after immersing the recovered positive electrode in an organic solvent, for example, by immersing the recovered positive electrode in an organic solvent to separate and remove the positive electrode current collector, and selectively extracting the positive electrode active material mixture by centrifugation.

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

[0045] For example, the positive electrode active material mixture may include dust particles. For example, the dust particles may include particles (e.g., carbon black) derived from the carbon-based conductive material and the binder. The dust particles may include powder formed by pulverizing the carbon-based conductive material and the binder by a physical method.

[0046] In an exemplary embodiment, a classifier 100 can be used to separate dust particles 60 from the positive electrode active material mixture and collect active material powder 70 including lithium composite oxide particles (eg, step S20).

[0047] FIG. 2 is a schematic cross-sectional view of a classifier according to an exemplary embodiment.

[0048] For example, the classifier 100 may include an active material inlet 150 into which a positive electrode active material mixture including an active material powder 70 containing lithium composite oxide particles and dust particles 60 is inject|poured, a classifying body 110 including a classifying sieve 115 which classifies the active material powder 70 into a first active material powder and a second active material powder, an upper discharge outlet 120 located at the upper part of the classifying body 110 and through which the dust particles 60 are scattered and discharged from the positive electrode active material mixture, an active material discharge outlet 140 connected to the center of the classifying body 110 and through which the first active material powder is discharged, and a lower discharge outlet 130 connected to the lower part of the classifying body 110 and through which the second active material powder is discharged.

[0049] In some exemplary embodiments, the classifier 100 may further include a fluid inlet 160 located at the bottom of the classifying body 110 through which a fluid is injected.

[0050] For example, the classifier 100 can remove dust particles 60 from the positive active material mixture by the fluid flowing into the classification body 110. In this case, active material powder 70 from which at least a portion of the dust particles 60 has been removed can be collected.

[0051] In this case, the dust particles 60 have a smaller density than the active material powder 70, and therefore can be scattered and removed from the positive electrode active material mixture by the fluid.

[0052] As a result, in the case where the dust particles 60 contained in the active material powder 70 include particles derived from the carbon-based conductive material and the binder, when the dust particles 60 contained in the active material powder 70 are separated, the particles derived from the carbon-based conductive material and the binder are separated in the active material powder 70, so that side reactions that may occur in the hydrogen reduction process described below are suppressed and the recovery efficiency of the lithium precursor can be improved.

[0053] For example, the fluid may be a liquid or a gas. For example, the fluid may be a non-reactive fluidizing gas. For example, the non-reactive fluidizing gas may include nitrogen (N2), helium (He), neon (Ne), argon (Ar), krypton (Kr), or xenon (Xe).

[0054] The fluid may form a cyclone by a propeller or the like located inside the classifying body 110. In this case, the cyclone may remove dust particles 60 from the positive active material mixture.

[0055] In some exemplary embodiments, the dust particles 60 may be scattered to the upper part of the classification body 110 and discharged through the upper discharge port 120 located at the upper part of the classification body 110. The dust particles 60 discharged from the upper discharge port 120 may be moved to the dust collecting section 200 and collected.

[0056] For example, the dust collecting unit 200 may form a negative pressure inside the upper exhaust port 120 to suck in the dust particles 60. For example, the dust particles 60 sucked into the upper exhaust port 120 may be collected by static electricity formed in the dust collecting unit 200.

[0057] In some exemplary embodiments, active material powder 70 obtained by separating dust particles 60 from the positive electrode active material mixture can include lithium composite oxide particles derived from the positive electrode active material.

[0058] For example, the lithium composite oxide particles may include first lithium composite oxide particles 80 and second lithium composite oxide particles 90 having different average particle sizes. For example, the first lithium composite oxide particles 80 may have an average particle size D50 larger than that of the second lithium composite oxide particles 90.

[0059] In this case, the first lithium composite oxide particles 80 may have an appropriate particle size value, which means fluidization-compatible particles that can be easily fluidized in a fluidized bed reactor, and the second lithium composite oxide 90 may have an average particle size D50 smaller than that of the first lithium composite oxide particles 80, which may mean fine particles that fly off instead of being fluidized in the fluidized bed reactor.

[0060] In this case, the first lithium composite oxide particles 80 may have an average particle size D50 of about 10 μm to 100 μm and a particle size distribution PSD of about 10 to 300 μm, and the second lithium composite oxide particles 90 may have an average particle size D50 of about 1 to 5 μm and a particle size distribution PSD of about 0.1 to 10 μm.

[0061] In some exemplary embodiments, the active material powder 70 may be classified into a first active material powder and a second active material powder, which may then be collected separately. In this case, the first active material powder and the second active material powder may be classified by a classifying sieve 115.

[0062] For example, the first active material powder can be defined as an active material powder that is easily fluidized in a fluidized bed reactor, and the second active material powder can be defined as an active material powder that scatters in the fluidized bed reactor.

[0063] For example, the first active material powder can include first lithium composite oxide particles 80 , and the second active material powder can include second lithium composite oxide particles 90 .

[0064] For example, the first active material powder and the second active material powder include both first lithium composite oxide particles 80 and second lithium composite oxide particles 90, but the first active material powder has a high proportion of the first lithium composite oxide particles 80 and is easily fluidized in a fluidized bed reactor, and the second active material powder has a high proportion of the second lithium composite oxide particles 90 and can be dispersed in the fluidized bed reactor.

[0065] For example, the classifying sieve 115 may be a porous plate having fine holes formed therein that allow only particles that fall within a predetermined particle size range to pass through. In this case, the active material powder 70 can be classified into the first active material powder and the second active material powder by the classifying sieve 115. For example, the classifying sieve 115 vibrates three-dimensionally by eccentric rotation of a rotary weight located at the bottom of the classifying sieve 115, and the three-dimensional vibration of the classifying sieve 115 can classify the active material powder 70 into the first active material powder and the second active material powder.

[0066] For example, the three-dimensional vibration may include circular vibration, elliptic vibration, and linear vibration caused by eccentric rotation of the rotary weight.

[0067] For example, the separation efficiency of the classifying sieve 115 according to particle size may be 60 to 90%. For example, the classifying sieve 115 may include holes. For example, the shape of the holes may be quadrangular (e.g., square).

[0068] For example, the size of the holes may be about 5 to 60 μm, preferably about 15 to 50 μm, and more preferably about 25 to 40 μm.

[0069] In some exemplary embodiments, the classifying sieve 115 may have a multi-stage structure in which a plurality of sieves are stacked. For example, the multi-stage structure may include 5 or more sieves. Preferably, the multi-stage structure may include 10 or more sieves, and more preferably, the multi-stage structure may include 20 or more sieves.

[0070] For example, when the classifying sieve 115 has the multi-stage structure, the efficiency of separating the first active material powder and the second active material powder can be further improved.

[0071] In some exemplary embodiments, the average particle size D50 of the second active material powder may be smaller than the average particle size D50 of the first active material powder.

[0072] For example, the active material powder that did not pass through the classifying sieve 115 can be defined as a first active material powder, and the active material powder that passed through the classifying sieve 115 can be defined as a second active material powder. In this case, most of the second lithium composite oxide particles 90 can pass through the classifying sieve 115 contained in the classification body 110, but only a portion of the first lithium composite oxide particles 80 may pass through the classifying sieve 115, and most of the first lithium composite oxide particles 80 may not pass through.

[0073] In some exemplary embodiments, the ratio of the hole size to the average particle size D50 of the second active material powder may be about 1.5 to 5. Preferably, the ratio of the hole size to the average particle size D50 of the second active material powder may be 2.5 to 4.

[0074] For example, when the ratio of the size of the holes to the average particle size D50 of the second active material powder satisfies the above range, the second active material powder can be separated from the first active material powder with higher efficiency. For example, when the ratio satisfies the above range, the separation rate of the second active material powder may be 90% or more.

[0075] Thereby, the first active material powder may have a higher proportion of first lithium composite oxide particles 80 than the second active material powder, and the second active material powder may have a higher proportion of second lithium composite oxide particles 90 than the first active material powder.

[0076] For example, the first active material powder has a high proportion of first lithium composite oxide particles 80 that are easily fluidized, and therefore can further improve the efficiency of the reduction step described below and the recovery efficiency of the lithium precursor. For example, the second active material powder has a high proportion of second lithium composite oxide particles 90 that are not easily fluidized, and therefore may not be suitable for the reduction step described below. In this case, the second active material powder can be treated with acid to recover the lithium precursor.

[0077] In some exemplary embodiments, the ratio of the average particle size of the first lithium composite oxide particles 80 to the particle size of the second lithium composite oxide particles 90 may be about 2 to 100. Within this particle size ratio range, the content of the first lithium composite oxide particles 80 contained in the first active material powder can be maximized, and the content of the first lithium composite oxide particles 80 contained in the second active material powder can be minimized. This can further improve the recovery efficiency of the lithium precursor.

[0078] For example, the ratio of the first lithium composite oxide particles 80 among the lithium composite oxide particles contained in the first active material powder may be 95% or more. For example, the ratio of the second lithium composite oxide particles 90 among the lithium composite oxide particles contained in the second active material powder may be 50% or more. Within the above range, excellent lithium precursor recovery efficiency can be more easily achieved.

[0079] In some exemplary embodiments, the first active material powder may be discharged from an active material outlet 140 connected to the center of the classifying body 110, and the second active material powder may be discharged from a lower outlet 130 connected to the lower part of the classifying body 110.

[0080] In some exemplary embodiments, the separated second active material powder can be treated with an acid solution. In this case, the lithium precursor can be recovered from the second active material powder by the acid solution treatment. This can further improve the recovery efficiency of the lithium precursor.

[0081] In particular, when the second active material powder is added to the raw material for the reduction process described below, the recovery efficiency of the lithium precursor may decrease due to impurities and scattering of the second active material powder, but by using the second active material powder as a raw material for a wet metal extraction process (e.g., acid solution treatment), the recovery efficiency of the lithium precursor can be further improved.

[0082] For example, the acid solution treatment may be a leaching process using an acid extractant. For example, the acid solution treatment may involve mixing the second active material powder with an acid extractant diluted with a diluent, and then adjusting the equilibrium pH to extract the lithium precursor. The second active material powder from which the lithium precursor has been extracted may be mixed with sulfuric acid, which is a removing agent, to extract the transition metal.

[0083] For example, the acidic extractant may include at least one selected from the group consisting of di-2-ethylhexylphosphoric acid, 2-ethylhexyl phosphonic acid mono-2-ethylhexyl ester, a mixture of di-2-ethylhexylphosphoric acid and tri-butyl-phosphate, and a mixture of 2-ethylhexyl phosphonic acid mono-2-ethylhexyl ester and tri-butyl-phosphate.

[0084] For example, the diluent may include dearomatized hydrocarbons.

[0085] For example, the equilibrium pH may be about 5.5 to 6.5. In this equilibrium pH range, the extraction rate of lithium can be effectively increased.

[0086] In some exemplary embodiments, the separation of dust particles 60 and the classification of the first and second active material powders can be performed together in the classifier 100. This can simplify the process of the lithium precursor recovery step and further improve the process efficiency.

[0087] According to an exemplary embodiment, a preliminary precursor mixture may be produced (e.g., step S30) from active material powder 70. In an exemplary embodiment, the preliminary precursor mixture may be produced by subjecting the first active material powder to a hydrogen reduction treatment.

[0088] In some embodiments, the hydrogen reduction treatment can be performed in a fluidized bed reactor. For example, the active material powder can be placed in the fluidized bed reactor, and hydrogen gas can be injected from the bottom of the fluidized bed reactor.

[0089] For example, when the first active material powder is used, the first active material powder can be fluidized more easily since the ratio of the first lithium composite oxide particles 80 is high, which can further improve the process efficiency of the hydrogen reduction step and the recovery efficiency of the lithium precursor.

[0090] The hydrogen gas forms a cyclone at the bottom of the fluidized bed reactor and contacts the active material powder 70 to produce the pre-precursor mixture. In this case, the active material powder 70 does not contain dust particles 60 or contains a trace amount of dust particles 60, so that unnecessary side reactions other than hydrogen reduction are prevented from occurring. This can further improve the yield of the lithium precursor.

[0091] In some embodiments, a carrier gas can be mixed and injected together with the hydrogen gas at the bottom of the fluidized bed reactor. This allows the fluidized bed to promote gas-solid mixing to promote the reaction and facilitate the formation of a reaction layer of the pre-precursor mixture in the fluidized bed reactor. The carrier gas can include, for example, an inert gas such as nitrogen (N2), argon (Ar), etc.

[0092] The preliminary precursor mixture may include a hydrogen reduction reactant of the lithium-transition metal oxide included in the active material powder 70. When an NCM-based lithium oxide is used as the lithium-transition metal oxide, the preliminary precursor mixture may include a preliminary lithium precursor and a transition metal-containing reactant.

[0093] 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.

[0094] The transition metal-containing reactant may include Ni, Co, NiO, CoO, MnO, and the like.

[0095] The hydrogen reduction reaction can be carried out at about 400 to 700°C, preferably 450 to 550°C.

[0096] According to an exemplary embodiment, after the pre-precursor mixture is collected, a water rinsing process may be performed (eg, step S40).

[0097] The water washing process can convert the preliminary lithium precursor into a lithium precursor substantially composed of lithium hydroxide. For example, lithium oxide and lithium carbonate mixed in the preliminary lithium precursor can be converted into lithium hydroxide by reacting with water, or can be removed by washing with water. This can produce a high-purity lithium precursor converted into the desired form of lithium hydroxide.

[0098] The reserve lithium precursor can react with water to dissolve and produce a substantially aqueous lithium hydroxide solution.

[0099] The transition metal-containing reactant contained in the preliminary precursor mixture can be precipitated without dissolving or reacting in water by the water washing process, and thus the transition metal-containing reactant can be separated by a filtration process to obtain a lithium precursor containing high purity lithium hydroxide.

[0100] In some embodiments, the water washing process can be performed under conditions where carbon dioxide (CO2) is excluded. For example, the water washing process can be performed in a CO2-free atmosphere (e.g., an air atmosphere from which CO2 has been removed), thereby preventing regeneration of lithium carbonate.

[0101] In one embodiment, the water provided during the water rinsing process can be purged with a CO2-depleted gas (eg, nitrogen purging) to provide a CO2-free atmosphere.

[0102] In some embodiments, the precipitated transition metal-containing reactant can be treated with an acid solution to form a precursor in the form of an acid salt of each transition metal. In one embodiment, sulfuric acid can be used as the acid solution. In this case, NiSO4, MnSO4, and CoSO4 can be recovered as the transition metal precursors.

[0103] As described above, the pre-precursor mixture produced by hydrogen reduction can be washed with water to obtain a lithium precursor substantially composed of lithium hydroxide, which prevents the by-production of other forms of lithium precursor such as lithium carbonate and provides a positive electrode active material with a higher capacity and a longer life.

[0104] The lithium precursor may include lithium hydroxide (LiOH), lithium oxide (Li2O) or lithium carbonate (Li2CO3). In terms of charge / discharge characteristics, life characteristics, high temperature stability, etc. of a lithium secondary battery, lithium hydroxide is advantageous as a lithium precursor. For example, lithium carbonate may cause a precipitation reaction on the separator, thereby reducing life stability.

[0105] Thus, according to embodiments of the present invention, a method for regenerating lithium hydroxide as a lithium precursor with high selectivity can be provided. [Explanation of symbols]

[0106] 100: Classifier 110: Classification body 115: Classifying sieve 120: Upper outlet 130: Lower outlet 140: Active material outlet 150: Active material injection port 160:Fluid inlet 60: Dust particles 70: Active material powder 80: First lithium composite oxide particles 90: Second lithium composite oxide particles

Claims

1. Preparing a positive electrode active material mixture including an active material powder containing lithium composite oxide particles and dust particles; separating the dust particles from the positive electrode active material mixture using a classifier and collecting the active material powder; reducing the active material powder to form a pre-precursor mixture; and recovering a lithium precursor from the pre-precursor mixture. The method for regenerating a lithium precursor, wherein the step of collecting the active material powder includes a step of classifying the active material powder into a first active material powder and a second active material powder and collecting each of the first active material powder and the second active material powder.

2. 2. The method for regenerating a lithium precursor according to claim 1, wherein the dust particles comprise particles derived from a carbon-based conductive material and a binder.

3. The method for regenerating a lithium precursor according to claim 1 , wherein the average particle size of the second active material powder is smaller than the average particle size of the first active material powder.

4. 2. The method for regenerating lithium precursors according to claim 1, wherein the collected first active material powder is subjected to a reduction treatment to form a pre-precursor mixture, and the collected second active material powder is subjected to an acid solution treatment.

5. 2. The method for regenerating a lithium precursor according to claim 1, wherein the separation of the dust particles and the classification of the first active material powder and the second active material powder are carried out together in the classifier.

6. The method for regenerating a lithium precursor according to claim 1 , wherein the reduction treatment of the active material powder is carried out in a fluidized bed reactor using a reducing reaction gas.

7. 2. The method for regenerating a lithium precursor according to claim 1, wherein recovering the lithium precursor from the pre-precursor mixture comprises washing the pre-precursor mixture with water.

8. The method for regenerating a lithium precursor according to claim 1, comprising the steps of: an active material injection port into which the active material powder containing the lithium composite oxide particles and the positive electrode active material mixture containing the dust particles are injected; a classification body including a classification sieve for classifying the active material powder into the first active material powder and the second active material powder; an upper outlet located at an upper portion of the classification body, through which the dust particles in the positive electrode active material mixture are scattered and discharged; an active material discharge port connected to a center portion of the classifying body and through which the first active material powder is discharged; a lower discharge port connected to a lower portion of the classifying body, through which the second active material powder in the positive active material mixture is discharged.

9. 9. The classifier of claim 8, further comprising a fluid inlet located at a lower portion of the classifying body and through which a fluid is injected.

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