Cathode active material, method for recycling cathode active material and secondary battery containing the same

Abstract

The present invention relates to a positive electrode active material, a method for regenerating the same, and a secondary battery including the same. More specifically, the invention relates to a positive electrode active material selected from the group consisting of a lithium nickel oxide (LNO)-based positive electrode active material, a nickel-cobalt-manganese (NCM)-based positive electrode active material, a nickel-cobalt-aluminum (NCA)-based positive electrode active material, a lithium iron phosphate compound, and a nickel-cobalt-manganese-aluminum (NCMA)-based positive electrode active material, wherein the positive electrode active material contains crystalline LiF and has a fluorine (F) content of 0.50 to 0.55 weight%, a method for regenerating the same, and a secondary battery including the same. According to the present invention, a waste cathode, particularly a waste cathode made of high-nickel (High-Ni) cathode material, is subjected to oxidation heat treatment by introducing oxygen, then immediately added a lithium precursor without a washing process, annealed, and washed with a small amount of washing solution to contain a predetermined crystalline phase LiF on the surface of the regenerated cathode active material and control the residual fluorine (F) content within a predetermined range, thereby providing a cathode active material with excellent capacity and resistance characteristics and significantly reduced wastewater generation. Furthermore, since acid is not used in the recovery and regeneration process, it is environmentally friendly, and since neutralization and wastewater treatment are not required, process costs are reduced. Additionally, since the cathode active material is regenerated as is without decomposition, no metal elements are wasted, and since organic solvents are not used, there is no risk of toxic gas generation or explosion. In particular, since the washing process is omitted, the economic efficiency and productivity are greatly improved, and there is an effect of providing a method for regenerating a cathode active material.

Description

Technology Field

[0001] The present invention relates to a positive electrode active material, a method for regenerating the same, and a secondary battery including the same. More specifically, the invention relates to a positive electrode active material having excellent capacity and resistance characteristics and significantly reduced wastewater generation by oxidizing a waste electrode using a high-nickel (High-Ni) positive electrode material by introducing oxygen for oxidative heat treatment, then immediately adding a lithium precursor without a washing process, annealing, and washing with a small amount of washing solution to contain a predetermined crystalline LiF on the surface of the regenerated positive electrode active material and controlling the residual fluorine (F) content within a predetermined range. The invention also relates to a method for regenerating a positive electrode active material that is environmentally friendly as it does not use acid in the recovery and regeneration process, thereby reducing process costs as neutralization and wastewater treatment are not required, regenerating the positive electrode active material as is without decomposition so that no metal elements are wasted, and not using organic solvents so that there is no risk of toxic gas generation or explosion, and in particular, significantly improved economic efficiency and productivity as the washing process is omitted. Background Technology

[0003] A lithium secondary battery is largely composed of a positive electrode in which a positive active material layer is coated on a metal foil such as aluminum, a negative electrode in which a negative active material layer is coated on a metal foil such as copper, a separator that prevents the positive and negative electrodes from mixing with each other, and an electrolyte that enables the movement of lithium ions between the positive and negative electrodes.

[0004] The above positive electrode active material layer mainly uses lithium-based oxides as active materials, and the above negative electrode active material layer mainly uses carbon materials as active materials. Since the lithium-based oxides generally contain rare metals such as cobalt, nickel, or manganese, much research is being conducted to recover and recycle rare metals from the positive electrodes of lithium secondary batteries that are discarded after use or from positive electrode scrap generated during the lithium secondary battery manufacturing process (hereinafter referred to as "waste positive electrodes").

[0005] Most conventional technologies for recovering rare metals from spent anodes involve dissolving the spent anodes in hydrochloric acid, sulfuric acid, or nitric acid, then extracting cobalt, manganese, nickel, etc., using organic solvents to reuse them as raw materials for the synthesis of anode active materials.

[0006] However, the extraction method for rare metals using acids poses a problem of environmental pollution and significantly increases process costs due to the mandatory need for neutralization and wastewater treatment processes; furthermore, it has the disadvantage of being unable to recover lithium, the main metal of the cathode active material.

[0007] In order to overcome these disadvantages, a direct recycling method is currently being studied to regenerate the cathode active material directly from the spent cathode without decomposing it. There are about four main methods introduced for this purpose, including calcination, solvent dissolution, aluminum foil dissolution, and crushing and screening.

[0008] However, although the above calcination method is simple, it has the disadvantages of generating foreign substances on the surface of the regenerated cathode active material that degrade the battery's output performance, producing waste gas, and consuming a large amount of energy.

[0009] In addition, while the above solvent dissolution method can obtain a regenerated cathode active material with a relatively clean surface, it has the disadvantage of poor stability because the solvent used to dissolve the binder, such as N-methyl-2-pyrrolidone (NMP), is a toxic gas and poses an explosion risk, and a high-cost solvent recovery process is required.

[0010] In addition, while the above-mentioned aluminum foil melting method offers good process stability, low process costs, and easy binder removal, it has disadvantages such as the generation of difficult-to-remove foreign substances on the surface of the regenerated cathode active material and the risk of explosion due to the generation of hydrogen gas during the aluminum foil removal process.

[0011] Finally, the above crushing and screening method has the advantage of being the simplest process, but it is difficult to completely separate the current collector and the positive active material, and it has the disadvantage that the particle size distribution of the positive active material changes during the crushing process and the binder remains, causing the battery characteristics of the regenerated positive active material to deteriorate.

[0012] Therefore, there is an urgent need to develop a method to safely and environmentally regenerate cathode active materials with improved output performance from waste cathodes, without wasting metal elements, and with minimal processing and cost. The problem to be solved

[0014] In order to solve the problems of the prior art as described above, the present invention aims to provide a method for regenerating an anode active material that has excellent capacity and resistance characteristics and significantly reduces wastewater generation by oxidizing a waste anode using a high-nickel (High-Ni) anode material by introducing oxygen, then immediately adding a lithium precursor without a washing process, annealing, and washing with a small amount of washing solution to contain a predetermined crystalline LiF on the surface of the regenerated anode active material and controlling the residual fluorine (F) content within a predetermined range. Furthermore, the method is environmentally friendly as it does not use acid in the recovery and regeneration process of the anode active material, and thus reduces process costs as neutralization and wastewater treatment are not required. Additionally, the method regenerates the anode active material as is without decomposing it, so there are no discarded metal elements, and does not use organic solvents, so there is no risk of toxic gas generation or explosion. In particular, the method is designed to provide a method for regenerating an anode active material that significantly improves economic efficiency and productivity by omitting the washing process.

[0015] In addition, the present invention aims to provide a secondary battery with excellent capacity and resistance characteristics.

[0016] The above and other objectives of the present invention can all be achieved by the present invention described below. means of solving the problem

[0018] To achieve the above objective, I) the present invention provides a positive electrode active material characterized by being one or more selected from the group consisting of a lithium nickel oxide (LNO)-based positive electrode active material, a nickel-cobalt-manganese (NCM)-based positive electrode active material, a nickel-cobalt-aluminum (NCA)-based positive electrode active material, a lithium iron phosphate compound, and a nickel-cobalt-manganese-aluminum (NCMA)-based positive electrode active material, containing crystalline LiF, and having a fluorine (F) content of 0.50 to 0.55 weight%.

[0019] II) In the above I), the positive electrode active material may contain 60 mol% or more of nickel (Ni) based on 100 mol% of the total remaining metals excluding lithium (Li).

[0020] III) In I) or II) above, the crystalline phase LiF may preferably have a peak in the XRD spectrum based on 2theta appearing at 38 to 40°.

[0021] IV) In I) to III) above, the positive active material may preferably have its surface coated with a coating agent containing metal or carbon.

[0022] V) In I) to IV) above, the metal may be boron (B), tungsten (W), or a mixture thereof.

[0023] VI) In I) to V) above, the positive active material may preferably be a regenerated positive active material.

[0024] In addition, VII) The present invention provides a method for regenerating an anode active material, characterized by comprising: a step of recovering an anode active material within an anode active material layer by oxidizing a waste anode in which an anode active material layer is formed on a current collector by introducing oxygen and thermally decomposing a binder and a conductive material within the anode active material layer; a step of adding a lithium precursor to the recovered anode active material and annealing it in oxygen or air at 400 to 1000 ℃; and a step of washing the annealed anode active material.

[0025] VIII) In the above VII), the positive active material layer may contain 60 mol% or more of nickel (Ni) based on 100 mol% of the total remaining metals excluding lithium (Li).

[0026] IX) In V) to VIII) above, the heat treatment can preferably be performed at 300 to 650 ℃.

[0027] X) In VI) to IX) above, the heat treatment may preferably be performed by first heat treatment at 300 to 450 ℃ and then second heat treatment at 500 to 650 ℃.

[0028] XI) In VI) to X) above, the first heat treatment is preferably performed for 10 minutes to 3 hours, and the second heat treatment can be performed for 10 minutes to 2 hours.

[0029] XII) In the above VI) to XI), the recovered anode active material from the annealing step may preferably contain crystalline LiF.

[0030] XIII) In VI) to XII) above, the lithium precursor may preferably include one or more of LiOH, Li2CO3, LiNO3, and Li2O.

[0031] XIV) In the above VI) to XIII), the lithium precursor may preferably be added in an amount that can provide 1 mol% to 40 mol% of lithium when the total lithium in the raw material cathode active material is 100 mol%.

[0032] XV) In the above VI) to XIV), the annealing can preferably be performed at 450 to 710 °C.

[0033] XVI) In the above VI) to XV), the weight ratio of the annealed positive active material and the washing solution in the washing step may preferably be 1:0.5 to 1:10.

[0034] XVII) In the above VI) to XVI), the method for regenerating the positive active material may preferably include a step of surface coating the washed positive active material.

[0035] XVIII) In the above VI) to XVII), the surface coating can preferably be coated on the surface in a solid or liquid manner with one or more of metals, organometallics, and carbon components, and then heat-treated at 100 to 1200 ℃.

[0036] In addition, XIX) The present invention provides a secondary battery characterized by comprising a positive active material according to any one of claims I) to VI). Effects of the invention

[0038] According to the present invention, a waste cathode using a high-nickel (High-Ni) cathode material is subjected to oxidation heat treatment by introducing oxygen, then immediately added a lithium precursor without a washing process, annealed, and washed with a small amount of washing solution to contain a predetermined crystalline LiF on the surface of the regenerated cathode active material and control the residual fluorine (F) content within a predetermined range, thereby providing a cathode active material with excellent capacity and resistance characteristics and significantly reduced wastewater generation. Furthermore, the recovery and regeneration process of the cathode active material is environmentally friendly as it does not use acid, and process costs are reduced because neutralization and wastewater treatment are not required. Additionally, the cathode active material is regenerated as is without decomposition, so no metal elements are wasted, and organic solvents are not used, so there is no risk of toxic gas generation or explosion. In particular, the washing process is omitted, so economic efficiency and productivity are significantly improved.

[0039] In addition, the method for regenerating the cathode active material of the present invention has the effect of lowering the resistance of the battery by reducing fluorine compounds generated during the heat treatment process of a waste cathode using high-nickel (High-Ni) cathode material. Brief explanation of the drawing

[0041] The following drawings attached to this specification illustrate embodiments of the present invention and serve to further enhance understanding of the technical concept of the present invention in conjunction with the detailed description provided below; therefore, the present invention should not be interpreted as being limited to the matters described in these drawings. Figure 1 is a drawing showing anode scrap that is discarded after cutting the electrode plate from the anode sheet. Figure 2 is a graph showing the capacity retention rate (%) according to the number of cycles, as a result of performing charge-discharge cycles on monocells to which the regenerated positive active material from Example 1 and Comparative Examples 1 to 3 was applied. Figure 3 is a graph showing the resistance increase rate (%) according to the number of cycles, as a result of performing charge-discharge cycles of CHC (Coin Half Cell) to which the regenerated positive active material from Example 1 and Comparative Examples 1 to 3 was applied. Figure 4 is a graph showing the efficiency (EF, %), charge capacity (%), and normalized in situ retention (%) as a result of performing charge-discharge cycles on CHCs (Coin Half Cells) to which the regenerated positive active materials from Example 1 and Comparative Examples 1 to 3 were applied. FIG. 5 is a flowchart of the regeneration process of the positive electrode active material according to the present invention. Specific details for implementing the invention

[0042] While researching a direct recycling method to regenerate a positive electrode active material with excellent rate performance without decomposing the positive electrode active material from a waste positive electrode, the inventors confirmed that when a waste positive electrode using a high-nickel (High-Ni) positive electrode is subjected to oxidative heat treatment by introducing oxygen, a lithium precursor is added immediately without a washing process, annealed, and then washed with a small amount of washing solution to contain a predetermined crystalline LiF on the surface of the regenerated positive electrode active material and control the residual fluorine (F) content within a predetermined range, the battery characteristics of the regenerated positive electrode active material are improved and the generation of wastewater is significantly reduced. Based on this, they further devoted themselves to research and completed the present invention.

[0044] The positive active material of the present invention, a method for regenerating the same, and a secondary battery including the same will be described in detail below.

[0045] However, terms and words used in this specification and claims cannot be interpreted as being limited to their ordinary or dictionary meanings, and must be interpreted in a meaning and concept consistent with the technical spirit of the invention, based on the principle that the inventor may appropriately define the concept of the terms to best describe his application. Accordingly, it should be understood that the embodiments described in this specification and the configurations illustrated in the drawings are merely one embodiment of the invention and do not represent all of the technical spirit of the invention, and that there may be various equivalents and modifications that can replace them, and that they may be arranged, replaced, combined, separated, or designed into various other configurations.

[0046] All technical and scientific terms used in this description have the same meaning as commonly understood by those skilled in the art to which the present invention belongs, unless otherwise defined.

[0048] positive electrode active material

[0049] The positive electrode active material of the present invention is one or more selected from the group consisting of a lithium nickel oxide (LNO)-based positive electrode active material, a nickel-cobalt-manganese (NCM)-based positive electrode active material, a nickel-cobalt-aluminum (NCA)-based positive electrode active material, a lithium iron phosphate compound, and a nickel-cobalt-manganese-aluminum (NCMA)-based positive electrode active material, and is characterized by containing crystalline LiF and having a fluorine (F) content of 0.50 to 0.55 weight%, in which case the capacity characteristics and resistance characteristics are excellent.

[0051] The above-mentioned positive active material may preferably include one or more selected from the group consisting of: lithium cobalt oxide such as LiCoO2 (hereinafter referred to as 'LCO'); lithium manganese oxide such as LiMnO2 or LiMn2O4; lithium iron phosphate compound such as LiFePO4; lithium nickel cobalt aluminum oxide (NCA); lithium nickel oxide such as LiNiO2; nickel manganese-based lithium composite metal oxide in which a portion of nickel (Ni) in the above-mentioned lithium nickel oxide is substituted with manganese (Mn); and NCM-based lithium composite transition metal oxide in which a portion of nickel (Ni) in the above-mentioned lithium nickel oxide is substituted with manganese (Mn) and cobalt (Co). In this case, the electrochemical performance, resistance characteristics, and capacitance characteristics are excellent.

[0052] The above positive active material is, as a specific example, the following chemical formula 1

[0053] [Chemical Formula 1]

[0054] Li a Ni x Mn y Co z M w O 2+δ

[0055] (In the above chemical formula 1, M comprises one or more selected from the group consisting of B, W, Al, Ti, and Mg, and 1 <a≤1.1, 0<x<0.95, 0<y<0.8, 0<z<1.0, 0≤w≤0.1, -0.02≤δ≤0.02, x+y+z+w=1이다.)로 표시되는 화합물을 포함할 수 있고, 이 경우 전기화학적 성능, 저항 특성 및 용량 특성 등이 우수한 효과가 있다.

[0057] The above positive active material contains, for example, 60 mol% or more of Ni based on 100 mol% of the total remaining metal excluding Li, preferably 80 mol% or more of Ni, and more preferably 81 mol% or more, and within this range, has excellent effects in terms of initial discharge capacity, output performance, capacity characteristics, and resistance characteristics.

[0058] In the description, the Ni content is not particularly limited when measured using a measurement method such as IC (Ion Chromatography) commonly used in the technical field to which the present invention belongs, and as specific examples, it can be measured using an IC-ICP (Inductively Coupled Plasma) analyzer, an IC-ICP-MS analyzer, or an IC-ICP-AEC analyzer.

[0060] In this description, the high-nickel cathode active material refers to a cathode active material containing 60 mol% or more of nickel.

[0062] The above crystalline LiF can be defined as having a peak in the XRD spectrum based on 2theta appearing at 38 to 40°, preferably at 38.5 to 39°, and in this case, it has excellent effects in terms of initial discharge capacity, output performance, capacitance characteristics, and resistance characteristics.

[0063] The above crystalline LiF may be included, for example, in an amount of 0.1 to 1 weight% with respect to the total weight of the positive electrode active material, preferably in an amount of 0.3 to 1 weight%, and more preferably in an amount of 0.3 weight% or more to less than 1 weight%, and within this range, there is an effect of excellent initial discharge capacity, output performance, capacity characteristics, and resistance characteristics.

[0064] In this description, the crystalline LiF content is not particularly limited when measured using a measurement method such as IC (Ion Chromatography) commonly used in the technical field to which the present invention belongs, and as specific examples, it can be measured using an IC-ICP (Inductively Coupled Plasma) analyzer, an IC-ICP-MS analyzer, or an IC-ICP-AEC analyzer. Here, the crystalline phase of LiF is confirmed by an XRD spectrum, and the content of LiF can be measured using a measurement method such as IC.

[0066] The above crystalline LiF may be included on the surface of the positive active material in, for example, 0.1 to 10 weight%, preferably 0.1 to 8 weight%, more preferably 0.1 to 7 weight% based on the XPS surface analysis spectrum, and within this range, there is an effect of excellent initial discharge capacity, output performance, capacity characteristics, and resistance characteristics.

[0067] In the present invention, the crystalline LiF content on the surface of the positive electrode active material can be measured using an XPS (X-ray photoelectron spectroscopy) surface analysis spectrum (K-alpha, Nexsa (Thermo Fisher Scientific)), and the XPS surface analysis spectrum can quantify the composition ratio or elements of constituent elements using the area or height of photoelectrons emitted from the surface of the sample.

[0069] For example, the above positive active material may have a fluorine (F) content of 0.50 to 0.55 weight%, preferably 0.50 to 0.53 weight%, and within this range, excellent resistance and capacitance characteristics are achieved.

[0071] The above-mentioned positive electrode active material may, for example, have its surface coated with metal or carbon, and preferably with metal. In this case, the structural stability of the positive electrode active material is improved without chemical or physical changes to the positive electrode active material itself, thereby enhancing electrochemical properties such as output performance, lifespan characteristics, and capacity. Additionally, physicochemical properties are improved through the substitution of heterogeneous elements on the surface of the positive electrode active material, resulting in a reduction in residual lithium content and pH.

[0073] The above metal is preferably one or more selected from the group consisting of B, W, Al, Ti, Mg, Ni, Co, Mn, Si, Zr, Ge, Sn, Cr, Fe, V, and Y, more preferably one or more selected from the group consisting of B, W, Al, Ti, and Mg, even more preferably boron (B), tungsten (W), or a mixture thereof, and even more preferably tungsten (W) and boron (B), and a specific example is tungsten boride (WB), in which case resistance characteristics and lifespan characteristics are improved.

[0075] The above coating agent may be, for example, 0.001 to 0.3 parts by weight, more preferably 0.01 to 0.3 parts by weight, and even more preferably 0.1 to 0.3 parts by weight based on 100 parts by weight of the total positive active material, and within this range, it has the effect of improving structural stability and electrochemical performance while maintaining the properties of the positive active material itself.

[0077] The above surface coating is preferably applied to the surface in a solid or liquid manner using a coating agent comprising one or more of metals, organometallics, and carbon components, and then heat-treated at 100 to 1200 ℃. In this case, it has the effect of improving structural stability and electrochemical performance while maintaining the properties of the anode active material itself.

[0079] The above-mentioned positive electrode active material may preferably be a regenerated positive electrode active material, in which case there is an advantage of excellent economic efficiency and productivity.

[0081] Method for regenerating positive electrode active material

[0082] The method for regenerating a positive electrode active material according to the present invention comprises the steps of: recovering the positive electrode active material by oxidizing a waste positive electrode in which a positive electrode active material layer is formed on a current collector by introducing oxygen to thermally decompose the binder and conductive material within the positive electrode active material layer; adding a lithium precursor to the recovered positive electrode active material and annealing it in oxygen or air at 400 to 1000 ℃; and washing the annealed positive electrode active material. In this case, by incorporating a predetermined crystalline LiF on the surface of the regenerated positive electrode active material, a positive electrode active material with excellent capacity and resistance characteristics is provided. Furthermore, the process of recovering and regenerating the positive electrode active material is environmentally friendly as it does not use acid, and process costs are reduced because neutralization and wastewater treatment are not required. Additionally, the positive electrode active material is regenerated as is without decomposition, so no metal elements are wasted, and organic solvents are not used, so there is no risk of toxic gas generation or explosion. In particular, the washing process is omitted, which has the advantage of significantly improving economic efficiency and productivity.

[0084] The method for regenerating the positive electrode active material is explained in detail below, divided into steps.

[0086] (a) A step of recovering positive electrode active material from waste positive electrodes

[0087] According to the present invention, the step of (a) recovering the positive active material from a waste positive electrode may preferably be a step of recovering the positive active material within the positive active material layer by oxidizing a waste positive electrode, in which a positive active material layer is formed on a current collector, by introducing oxygen and heat treating the waste positive electrode, and then thermally decomposing the binder and conductive material within the positive active material layer. In this case, the process is simple and has the effect of cleanly removing the binder, conductive material, and current collector.

[0088] The above waste anode may preferably be an anode separated from a lithium secondary battery that has been disposed of after use, a defective anode sheet or anode scrap generated during the lithium secondary battery manufacturing process, and more preferably, it may be anode scrap remaining after punching out an anode plate from an anode sheet.

[0090] The positive active material layer of step (a) above may preferably include a positive active material, a binder, and a conductive material.

[0091] The above-mentioned positive active material may preferably be one or more selected from the group consisting of lithium cobalt oxide such as LiCoO2 (hereinafter referred to as 'LCO'); lithium manganese oxide such as LiMnO2 or LiMn2O4; lithium iron phosphate compound such as LiFePO4; lithium nickel cobalt aluminum oxide (NCA); lithium nickel oxide such as LiNiO2; nickel manganese-based lithium composite metal oxide in which a portion of nickel (Ni) in the above-mentioned lithium nickel oxide is substituted with manganese (Mn); and NCM-based lithium composite transition metal oxide in which a portion of nickel (Ni) in the above-mentioned lithium nickel oxide is substituted with manganese (Mn) and cobalt (Co). More preferably, it may be a nickel manganese-based lithium composite metal oxide, an NCM-based lithium composite transition metal oxide, or a mixture thereof, in which case it has excellent reversible capacity and thermal stability.

[0092] As another specific example, the above positive active material is the following chemical formula 1

[0093] [Chemical Formula 1]

[0094] Li a Ni x Mn y Co z M w O 2+δ

[0095] (In the above chemical formula 1, M comprises one or more selected from the group consisting of B, W, Al, Ti, and Mg, and 1 <a≤1.1, 0<x<0.95, 0<y<0.8, 0<z<1.0, 0≤w≤0.1, -0.02≤δ≤0.02, x+y+z+w=1이다.)로 표시되는 화합물일 수 있다.

[0097] The above positive active material contains, for example, 60 mol% or more of Ni based on 100 mol% of the total remaining metal excluding Li, preferably 80 mol% or more of Ni, and more preferably 81 mol% or more, and within this range, has excellent effects in terms of initial discharge capacity, output performance, capacity characteristics, and resistance characteristics.

[0098] In the description, the Ni content is not particularly limited when measured using a measurement method such as IC (Ion Chromatography) commonly used in the technical field to which the present invention belongs, and as specific examples, it can be measured using an IC-ICP (Inductively Coupled Plasma) analyzer, an IC-ICP-MS analyzer, or an IC-ICP-AEC analyzer.

[0100] The above conductive material may be, for example, a carbon-based conductive material, and preferably may be carbon black, carbon nanotubes (CNT), or a mixture thereof.

[0101] The binder may be, for example, a polymer binder, preferably polyvinylidene fluoride (PVdF), acrylonitrile-butadiene rubber (NBR), or a mixture thereof, and more preferably polyvinylidene fluoride.

[0103] The above oxidation heat treatment may be, for example, 300 to 650 ℃, preferably 400 to 600 ℃, more preferably 500 to 600 ℃, and even more preferably 530 to 580 ℃. Within this range, the current collector does not melt, and carbon materials in the binder or conductive material react with oxygen to burn into CO and CO2 gases and are removed, so there is an advantage that almost all of the binder and conductive material are easily removed without any residue.

[0104] The oxidation heat treatment time may preferably be 10 minutes to 5 hours, more preferably 30 minutes to 5 hours, even more preferably 30 minutes to 2 hours, and even more preferably 30 minutes to 1 hour. Within this range, the current collector does not melt, and only the binder, etc., is removed, so that the positive active material is easily separated from the current collector.

[0105] In this description, the oxidation heat treatment time refers to the time processed at the corresponding oxidation heat treatment temperature, and the time to reach the corresponding heat treatment temperature is not calculated.

[0106] The above oxidation heat treatment can be performed in two stages, for example, and preferably, a first heat treatment can be performed at 300 to 450 ℃ followed by a second heat treatment at 500 to 650 ℃. In this case, the process is simple, and there is an advantage of cleanly removing the binder, conductive material, and current collector, and reducing fluorine (F) and residual lithium generated during the pyrolysis process.

[0108] The above first heat treatment temperature may preferably be 300 to 430 ℃, more preferably 320 to 400 ℃, and within this range, there is an advantage that the thermal decomposition of binders and organic materials occurs smoothly.

[0109] The above first heat treatment time may preferably be 10 minutes to 3 hours, more preferably 20 minutes to 160 minutes, and within this range, the current collector does not melt and only the binder, etc. is removed, so there is an advantage that the positive active material is easily separated from the current collector.

[0110] The above secondary heat treatment temperature may preferably be 510 to 630 ℃, more preferably 520 to 630 ℃, and within this range, the binder and conductive material are completely combusted, and there is an advantage that fluorine (F) and residual lithium generated during the pyrolysis process are reduced.

[0111] The above second heat treatment time may preferably be 10 minutes to 2 hours, more preferably 20 minutes to 100 minutes, and within this range, the current collector does not melt and only the binder, etc. is removed, so there is an advantage that the positive active material is easily separated from the current collector.

[0112] The total sum of the first heat treatment time and the second heat treatment time may be, for example, 20 minutes to 5 hours, preferably 30 minutes to 4 hours, and within this range, the current collector is not melted and only the binder, etc. is removed, so that the positive active material is easily separated from the current collector and there is an advantage of reducing fluorine (F) and residual lithium generated during the thermal decomposition process.

[0113] In this description, the heat treatment time refers to the time processed at the corresponding heat treatment temperature, and the time to reach the corresponding heat treatment temperature is not calculated.

[0114] The above oxygen may, for example, have a purity of 59% or more, preferably 80% or more, more preferably 90% or more, and even more preferably 90 to 99%, and within this range, it is removed without residue of binder and conductive material, and there is an advantage of increased stability of Ni in the active material and reduced crystal size.

[0115] The purity % of the above oxygen may be volume % or mol %.

[0116] The purity of the oxygen described herein is not particularly limited when measured by a measurement method commonly used in the technical field to which the present invention belongs.

[0118] The above second heat treatment can preferably be carried out by raising the temperature immediately after the above first heat treatment is completed, in which case almost all of the binder and conductive material are removed without residue.

[0120] The above-mentioned recovered cathode active material can be provided directly to annealing without, for example, washing, and in this case, the cathode active material contains crystalline LiF, which has the advantage of excellent capacitance and resistance characteristics and does not generate wastewater.

[0122] Figure 1 below shows anode scrap that is discarded after cutting the anode plate from the anode sheet.

[0123] Referring to FIG. 1, an anode sheet (30) is manufactured by coating an anode active material layer (20) containing an anode active material, a conductive material, a binder, etc., onto an aluminum foil (10), which is a long sheet-type anode current collector, and then the anode sheet (40) is produced by punching it into a certain size, and then anode scrap (50) is generated from the remaining part. The punching is a means of cutting the anode sheet.

[0124] In addition, the above positive active material layer (20) is formed by coating a slurry mixed with a positive active material, a conductive material, a binder, and a solvent onto an aluminum foil (10). Since the slurry is very sensitive to environmental conditions such as temperature, it is very difficult to establish coating conditions, and thus waste positive sheets are generated until conditions are found to manufacture a positive sheet (30) of the desired quality through a predetermined test.

[0125] For reference, in the following examples, anode scrap was used as the waste anode.

[0127] (b) a step of adding a lithium precursor to the recovered positive electrode active material and annealing.

[0128] The method for regenerating a positive electrode active material according to the present invention comprises the step of (b) adding a lithium precursor to the recovered positive electrode active material and annealing it in oxygen or air at 400 to 1000 ℃, wherein the surface of the regenerated positive electrode active material contains a predetermined crystalline phase LiF, thereby providing a positive electrode active material with excellent capacity and resistance characteristics, and the washing process of the recovered active material is omitted, which has the advantage of greatly improving economic efficiency and productivity.

[0130] The above-mentioned recovered cathode active material may preferably contain crystalline LiF, and in this case, there is an advantage of providing a regenerated cathode active material with excellent capacity and resistance characteristics.

[0131] For example, the crystalline phase LiF above has a peak in the XRD spectrum based on 2theta at 38 to 40°, preferably at 38.5 to 39°, and in this case, has excellent effects in terms of initial discharge capacity, output performance, capacitance characteristics, and resistance characteristics.

[0132] The above crystalline LiF may be included, for example, in an amount of 0.1 to 1 weight% with respect to the total weight of the positive electrode active material, preferably in an amount of 0.3 to 1 weight%, and more preferably in an amount of 0.3 weight% or more to less than 1 weight%, and within this range, there is an effect of excellent initial discharge capacity, output performance, capacity characteristics, and resistance characteristics.

[0134] The above lithium precursor may preferably be one or more selected from the group consisting of LiOH, Li2CO3, LiNO3, and Li2O, and in this case, there is an advantage that the battery characteristics of the regenerated cathode active material are improved.

[0136] The above lithium precursor can preferably be added in an amount of lithium reduced from the molar ratio of lithium in the cathode active material of step (a) based on the amount of lithium in the recovered cathode active material, and more preferably in an amount such that the molar ratio of lithium in the cathode active material of step (a) is 0.0001 to 0.2. Within this range, the insufficient lithium in the regenerated cathode active material is supplemented, and the crystallinity is improved, such as by increasing crystallinity or recovering the crystal structure, thereby having the advantage of improving the battery characteristics of the regenerated cathode active material.

[0137] The above lithium precursor can preferably be added in an amount that provides 1 to 40 mol% of lithium when the total lithium in the raw material cathode active material is 100 mol%, more preferably in an amount corresponding to 1 to 15 mol%, and even more preferably in an amount corresponding to 7 to 11 mol%, and within this range, no residual precursor that can increase resistance remains in the regenerated cathode active material, which is very useful for improving battery characteristics.

[0139] The above annealing can be performed, for example, in oxygen or air under conditions of 400 to 1000 ℃, preferably under conditions of 400 to 900 ℃, more preferably under conditions of 400 to 800 ℃, and even more preferably under conditions of 450 to 710 ℃, and within this range, the crystal structure is recovered, resulting in excellent output performance of the battery.

[0140] Preferably, the annealing temperature can be controlled within a limited range depending on the melting point of the lithium precursor, for example, in the case of LiCO3, the melting point is 723 °C, preferably 600 to 900 °C, more preferably 600 to 800 °C, More preferably, annealing can be performed at 650 to 715 ℃, and in the case of LiOH, the melting point is 462 ℃, so annealing can be performed at 400 to 600 ℃, more preferably at 450 to 480 ℃, and within this range, the crystal structure is recovered, resulting in excellent output performance of the battery.

[0141] The annealing temperature above may preferably be a temperature exceeding the melting point of the lithium precursor, provided that if it exceeds 1000°C, thermal decomposition of the positive electrode active material may occur, causing a decrease in the performance of the battery, so it may be preferable to have a temperature of 1000°C or lower.

[0143] (c) Step of washing the annealed positive electrode active material

[0144] The method for regenerating the positive electrode active material of the present invention includes (c) a step of washing the annealed positive electrode active material, wherein the lithium precursor that is prone to remaining is removed, thereby having the advantage of preventing the degradation of battery performance and gas generation caused by the reaction between the residual lithium precursor and the electrolyte thereafter.

[0146] The above washing step may, for example, have a weight ratio of annealed positive electrode active material to washing solution of 1:0.5 to 1:10, preferably 1:0.5 to 1:7, more preferably 1:0.5 to 1:5, even more preferably 1:1 to 1:3, even more preferably 1:1.5 to 1:3, and particularly preferably 1:1.5 to 1:2.5. In this case, there is an advantage that lithium precursors such as LiOH, Li2CO3, etc., which are more likely to remain due to the excess lithium added to suppress the cation mixing phenomenon that is prone to occur in positive electrode active materials, particularly high-nickel positive electrode active materials, are effectively removed. This cation mixing phenomenon occurs because the particle sizes of nickel and lithium are similar.

[0147] In this description, a high-nickel (High-Ni) cathode active material refers to a cathode active material containing 60 mol% or more of nickel.

[0149] In particular, when the annealed active material and the washing solution are mixed in a weight ratio of 1:1.5 to 1:3, preferably 1:1.5 to 2.5, the initial discharge capacity (DCH) and efficiency of the regenerated positive electrode active material are further improved.

[0150] The above washing solution may preferably be water, more preferably distilled water or deionized water, and in this case, lithium precursors such as LiOH, Li2CO3, etc., which are more likely to remain due to the excess lithium added to suppress the cation mixing phenomenon that is likely to occur in the positive active material, particularly in high-nickel positive active material, are effectively removed.

[0152] The washing step described above may include, for example, a step of mixing an annealed positive electrode active material with a washing solution and then filtering, and a step of drying the solid positive electrode active material obtained after filtration. In this case, there is an effect of effectively removing excess lithium that is prone to remaining in the positive electrode active material.

[0153] The above filtration may preferably be vacuum filtration using a filter.

[0154] The above drying may preferably be at 100 to 500 ℃, more preferably at 120 to 400 ℃, even more preferably at 120 to 300 ℃, and even more preferably at 120 to 200 ℃.

[0155] The above drying can preferably be carried out in a vacuum drying process.

[0156] In this description, vacuum drying is not particularly limited to vacuum drying commonly practiced in the technical field to which the present invention belongs.

[0158] (d) A step of surface coating the washed positive active material

[0159] The method for regenerating the positive electrode active material of the present invention includes (d) a step of surface coating the washed positive electrode active material, and in this case, has the effect of improving structural stability and electrochemical performance while maintaining the properties of the positive electrode active material itself.

[0160] The above surface coating is preferably applied to the surface in a solid or liquid manner using a coating agent comprising one or more of metals, organometallics, and carbon components, and then heat-treated at 100 to 1200 ℃. In this case, it has the effect of improving structural stability and electrochemical performance while maintaining the properties of the anode active material itself.

[0162] The coating agent containing the above metal is preferably a coating agent comprising one or more selected from the group consisting of B, W, Al, Ti, Mg, Ni, Co, Mn, Si, Zr, Ge, Sn, Cr, Fe, V, and Y, more preferably a coating agent comprising one or more selected from the group consisting of B, W, Al, Ti, and Mg, even more preferably a coating agent comprising boron (B), tungsten (W), or a mixture thereof, and even more preferably a coating agent containing tungsten (W) and boron (B), and a specific example is a coating agent containing tungsten boride (WB), in which case resistance characteristics and lifespan characteristics are improved.

[0163] The coating agent containing the above metal may be, for example, an oxide or acid containing the metal as an element within the molecule.

[0164] The above-mentioned coating agent containing the organometallic compound is not particularly limited as long as it is a coating agent that is commonly used in the technical field to which the present invention belongs and contains the organometallic compound containing the metal, and specific examples may include metal alkoxides, etc.

[0165] The coating agent containing the carbon component mentioned above is not particularly limited to coating agents containing carbon components commonly used in the technical field to which the present invention belongs, and specific examples may include sugars such as sucrose.

[0167] The above coating agent may be, for example, 0.001 to 1 part by weight, preferably 0.001 to 0.3 parts by weight or 0.001 to 0.7 parts by weight, more preferably 0.01 to 0.3 parts by weight or 0.01 to 0.5 parts by weight, and even more preferably 0.1 to 0.3 parts by weight based on 100 parts by weight of the total positive active material, and within this range, it has the effect of improving structural stability and electrochemical performance while maintaining the properties of the positive active material itself.

[0169] The above heat treatment temperature may preferably be 100 to 1000 ℃, more preferably 200 to 1000 ℃, and even more preferably 200 to 500 ℃, and within this range, there is an effect of improving structural stability and electrochemical performance without performance degradation due to thermal decomposition of the cathode active material.

[0170] The above heat treatment time can preferably be carried out for 1 to 16 hours, more preferably for 3 to 7 hours, and within this range, it has the effect of improving structural stability and electrochemical performance while maintaining the properties of the anode active material itself.

[0172] The above coating method is not particularly limited to coating methods commonly used in the technical field to which the present invention belongs, and may be, for example, a liquid-phase method in which a liquid coating agent is prepared and mixed with an anode active material, a mechanochemical method utilizing high mechanical energy of ball milling, a fluidized bed coating method, a spray drying method, a precipitation method in which a coating agent is precipitated onto the surface of an anode active material in an aqueous solution, a method utilizing a reaction between a gaseous coating agent and an anode active material, or a sputtering method.

[0174] The above metal, organometallic, and carbon components may be, for example, spherical, plate-shaped, angular, or needle-shaped, and such shapes can be controlled by changing process conditions during the manufacturing process, and the definition of each shape is not particularly limited as long as it follows the definitions commonly accepted in the technical field to which the present invention belongs.

[0175] The coating agent may preferably have an average diameter of 1 to 1000 nm and a specific surface area of ​​10 to 100 m² / g, and more preferably an average diameter of 10 to 100 nm and a specific surface area of ​​20 to 100 m² / g, and may be uniformly attached to the surface of the positive active material within this range to provide structural stability to the positive active material, thereby improving the problems of lifespan characteristics and electrochemical performance degradation caused by lattice deformation or collapse of the crystal structure of the positive active material.

[0176] In this description, the average diameter can be measured using a measurement method commonly used in the technical field to which the present invention belongs, for example, by using a laser diffraction method. Specifically, after dispersing particles of the positive active material in a dispersion medium, they are introduced into a commercially available laser diffraction particle size measuring device such as Microtrac MT 3000, and ultrasound of about 28 kHz is irradiated at an output of 60 W, and the average particle diameter (D50) at the 50% reference of the particle diameter distribution in the measuring device can be calculated.

[0177] In this description, the specific surface area can be measured by a measurement method commonly used in the technical field to which the present invention belongs, for example, by the BET (Brunauer-Emmett-Teller) method, and specifically, it can be calculated from the amount of nitrogen gas adsorbed at liquid nitrogen temperature (77K) using BEL Japan's BELSORP-mino II.

[0179] Figure 5 below is a flowchart of a regeneration process for a positive electrode active material as one embodiment according to the present invention.

[0180] Referring to FIG. 5, anode scrap is first prepared from waste anodes (step S10). For example, a slurry prepared by adding NMP (N-methyl pyrrolidone) to NCM-based lithium composite transition metal oxide, carbon black, and polyvinylidene fluoride is coated onto aluminum foil and dried in a vacuum oven at approximately 120°C to produce an anode sheet. After punching out an anode plate of a certain size from this, the remaining anode scrap can be prepared.

[0181] The above-mentioned anode scrap has an anode active material layer on aluminum foil, and the anode active material layer has a structure in which a binder binds the anode active material and the conductive material after solvent volatilization. Therefore, when the binder is removed, the anode active material is separated from the aluminum foil.

[0183] Next, the prepared anode scrap is crushed into a suitable size (step S20). Here, crushing includes cutting or shredding the anode scrap into a size that is easy to handle. As a specific example, the crushed anode scrap may be 1 cm x 1 cm in size. The crushing may be performed using various dry crushing equipment such as a hand mill, pin mill, disc mill, cutting mill, or hammer mill, for example, or a high-speed cutter may be used to increase productivity.

[0184] The above crushing can preferably be performed or the size of the pieces can be determined by considering the characteristics required by the equipment used in the handling of anode scrap and subsequent processes. For example, if equipment capable of continuous processing is used, the anode scrap must be crushed into smaller pieces because fluidity must be good.

[0186] Next, the anode scrap is subjected to oxidative heat treatment by introducing oxygen to remove the binder and conductive material (step S30). Here, the first heat treatment is performed to remove the binder and conductive material.

[0187] The above oxidation heat treatment is preferably performed in oxygen with a purity of 80% or higher, and more preferably in oxygen with a purity of 90% or higher. In this case, Ni stability can be ensured in waste anodes, particularly waste anodes using high-nickel (High-Ni) anode materials, and the binder and conductive material are effectively removed cleanly. If heat treatment is performed in a reducing gas or inert gas atmosphere, the binder and conductive material are carbonized without thermal decomposition. When carbonized, carbon components remain on the surface of the anode active material, which degrades the performance of the reusable anode active material. However, if oxidation heat treatment is performed by introducing oxygen, the carbon components in the binder and conductive material react with oxygen and disappear as gases such as CO and CO2, thereby removing both the binder and the conductive material.

[0188] The above oxidation heat treatment is preferably performed at 300 to 650 ℃, and as a specific example, at 590 ℃. Below 300 ℃, it is difficult to remove the binder and thus the current collector cannot be separated, and above 650 ℃, the current collector melts and a problem arises in which the current collector cannot be separated.

[0189] The above oxidation heat treatment is preferably performed at a temperature rise rate of 1 to 20 ℃ / min, more preferably at a temperature rise rate of 3 to 10 ℃ / min, and as a specific example, 5 ℃ / min. Within this range, it can be implemented without putting strain on the heat treatment equipment and has the advantage of not causing thermal shock to the anode scrap.

[0190] The above oxidation heat treatment can be performed for a period of time sufficient for the binder to be sufficiently decomposed, for example, preferably for 30 minutes or more, more preferably for 30 minutes to 5 hours, and a specific example is around 30 minutes, within this range, the binder is sufficiently decomposed and the decomposition efficiency is excellent.

[0192] The above oxidation heat treatment step can preferably be carried out in two stages, and more preferably, a first oxidation heat treatment can be performed at 300 to 430 ℃ followed by a second heat treatment at 510 to 630 ℃. In this case, the fluorine (F) and residual lithium generated during the thermal decomposition process are reduced through the two-stage heat treatment, which has the advantage of reducing the amount of fluorine (F) and residual lithium.

[0193] The above first heat treatment temperature can preferably be performed at 300 to 430 ℃, more preferably at 320 to 400 ℃, and as a specific example, at 350 ℃.

[0194] The above first heat treatment time can preferably be carried out for 10 minutes to 3 hours, more preferably for 20 minutes to 160 minutes, and as a specific example, for 30 minutes.

[0195] The above secondary oxidation heat treatment temperature may more preferably be 520 to 630 ℃, and as a specific example, it may be performed at 590 ℃. Within this range, the binder and the conductive material are sufficiently thermally decomposed, and there is an advantage that the fluorine (F) and residual lithium generated during the thermal decomposition process are reduced and the crystal size becomes smaller.

[0196] The above second heat treatment time may preferably be 10 minutes to 2 hours, more preferably 20 minutes to 100 minutes, and as a specific example, 30 minutes. Within this range, the current collector does not melt, and only the binder, etc. is removed, so there is an advantage that the positive active material is easily separated from the current collector.

[0198] The above oxidation heat treatment is preferably performed at a temperature rise rate of 1 to 20 ℃ / min, more preferably at a temperature rise rate of 3 to 10 ℃ / min, and as a specific example, 5 ℃ / min. Within this range, it can be implemented without putting strain on the heat treatment equipment and has the advantage of not causing thermal shock to the anode scrap.

[0199] The above oxidation heat treatment is performed using various types of furnaces, for example, a box-type furnace, and, considering productivity, a rotary kiln capable of continuous processing is used.

[0200] After the above oxidation heat treatment, slow cooling or rapid cooling can be performed in the atmosphere.

[0202] Next, a lithium precursor is added to the recovered positive electrode active material and annealed (step S40).

[0203] In the above annealing step, it is important to add a lithium precursor directly to the recovered cathode active material and anneale it without a washing process. In this case, the crystalline LiF formed on the surface of the cathode active material in the preceding heat treatment step S30 is retained in the regenerated cathode active material, which has the advantage of improving battery characteristics when applied to a secondary battery.

[0205] In addition, since lithium is lost within the cathode active material during the preceding step S30, step S40 replenishes such lost lithium. Furthermore, because a deformed structure (e.g., Co3O4 in the case of LCO active material) may appear on the surface of the cathode active material during the preceding step, step S40 restores the crystal structure of the cathode active material through annealing to improve the battery characteristics of the regenerated cathode active material or restore it to the level of the newly produced cathode active material. Here, 'newly produced' is a concept opposite to 'regeneration,' meaning that it is created for the first time, and is synonymous with terms such as 'raw material' used in the examples.

[0206] LiOH is used as a specific example of the above lithium precursor.

[0207] It is desirable to add the above lithium precursor in an amount equal to at least the molar ratio of the lost lithium, relative to the molar ratio of lithium and other metals in the newly generated cathode active material used in the cathode active material layer. Adding an excessive amount of lithium precursor compared to the amount of lost lithium leaves unreacted lithium precursor in the regenerated cathode active material, which acts to increase resistance; therefore, it is necessary to add an appropriate amount of lithium precursor.

[0208] In one embodiment, based on the case where the molar ratio of lithium in the newly formed cathode active material is 1 relative to another metal (M), an amount of lithium precursor can be added such that the lithium has a molar ratio of 0.001 to 0.4, preferably an amount such that the lithium has a molar ratio of 0.01 to 0.4, and more preferably an amount such that the lithium has a molar ratio of 0.09 to 0.2. As a specific example, if a lithium precursor is added in an amount equal to the ratio lost relative to the lithium content in the newly formed cathode active material based on ICP analysis results, a capacity improvement effect equivalent to that of the newly formed cathode active material is achieved. Here, the ICP analysis results have an error value of approximately ±0.02.

[0210] In one embodiment, the lithium precursor may be added in an amount that provides 1 to 40 mol% of lithium when the total lithium in the raw material cathode active material is 100 mol%, more preferably in an amount corresponding to 1 to 15 mol%, and even more preferably in an amount corresponding to 7 to 11 mol%. Within this range, no residual precursor that can increase resistance remains in the regenerated cathode active material, which is very useful for improving battery characteristics. Here, the raw material cathode active material may refer to the cathode active material prior to the recovery step or prior to disposal.

[0212] The above annealing is performed, for example, in oxygen or air under conditions of 400 to 1000 ℃, preferably under conditions of 400 to 900 ℃, more preferably under conditions of 400 to 800 ℃, and even more preferably under conditions of 450 to 710 ℃, and this temperature must be modified within a limited range depending on the type of lithium precursor.

[0213] The above annealing temperature is preferably a temperature exceeding the melting point of the lithium precursor. However, since thermal decomposition of the cathode active material occurs at temperatures exceeding 1000°C, leading to performance degradation, the temperature should not exceed 1000°C. Accordingly, when Li2CO3 is used as the lithium precursor, the annealing temperature is 600 to 900°C, and more preferably 650 to 715°C. In addition, when LiOH is used as the lithium precursor, the annealing temperature is 400 to 600°C, more preferably 450 to 480°C, and most preferably 470 to 480°C.

[0215] The above annealing time is preferably 1 hour or more, preferably 15 hours or less, and more preferably 4 to 6 hours. Although a longer annealing time allows for sufficient recovery of the crystal structure, annealing for a long time does not significantly affect performance. At this time, the annealing equipment may be the same or similar equipment as that used in the heat treatment step S30.

[0217] Next, the annealed positive active material is washed (step S50).

[0218] In the annealing step S40 above, lithium precursors that did not participate in the reaction exist on the surface of the positive electrode active material in the form of LiOH and Li2CO3, so a residual lithium removal process is required to remove them. In particular, high-content Ni-based positive electrode active materials require an excess amount of Li due to cation mixing phenomena, which makes it easy for lithium impurities such as lithium carbonate (Li2CO3) to remain on the surface. Since these impurities can later react with the electrolyte to degrade the performance of the battery and generate gas, they must be thoroughly removed.

[0219] The above washing can preferably be performed using distilled water, which has the advantage of being safe and inexpensive while not leaching out transition metals present in the positive electrode active material.

[0221] The above washing process preferably involves mixing an annealed positive electrode active material and a washing solution in a weight ratio of 1:2, filtering the mixture, and then drying the obtained solid positive electrode active material.

[0222] The mixing of the annealed anode active material and the washing solution is preferably carried out by stirring, and the stirring is not particularly limited but is mechanical stirring, magnetic stirring, or ultrasonic stirring.

[0223] The above mechanical stirring includes, for example, an impeller and is preferably carried out under conditions of 250 to 350 RPM and 3 to 10 minutes.

[0224] The above filtration is preferably vacuum filtration using a filter, and the above drying is vacuum drying at 120 to 140°C.

[0226] Next, as an optional step, a surface coating can be performed on the washed positive active material (step S60).

[0227] The above surface coating involves, for example, coating a surface with a coating agent containing a metal, organometallic, or carbon component in a solid or liquid manner and then heat-treating it; however, if the heat treatment temperature is too low, a surface protective layer made of the desired dissimilar metal is not formed, and if the heat treatment temperature is too high, the performance of the battery is degraded due to the thermal decomposition of the positive electrode active material.

[0228] Specifically, when metal oxides such as B, W, BW, or acid are coated onto a washed positive active material and then heat-treated, a surface protective layer such as a lithium borosilicate layer is formed on the surface of the positive active material.

[0229] The solid or liquid method of the above surface coating may be, for example, a method such as mixing, milling, spray drying, or grinding.

[0231] If the molar ratio of lithium to other metals in the positive electrode active material is made 1:1 in the annealing step S40, the lithium in the positive electrode active material reacts with the coating agent in the surface coating step S60, causing the molar ratio of lithium to other metals in the positive electrode active material to become less than 1:1, and such a regenerated positive electrode active material cannot fully exert 100% of its battery capacity. However, if an excess amount of lithium precursor is added in the annealing step S50 such that it is included in a molar ratio of 0.0001 to 0.1 more than other metals in the positive electrode active material, a surface protective layer is formed in the surface coating step S60, naturally making the molar ratio of lithium to other metals in the positive electrode active material 1:1, thereby preventing a decrease in battery capacity.

[0233] secondary battery

[0234] The secondary battery of the present invention includes the above-mentioned positive active material, and in this case, by incorporating a predetermined crystalline LiF on the surface of the positive active material, the capacity and resistance characteristics are excellent and the generation of wastewater is significantly reduced. Furthermore, since acids and organic solvents are not used in the recovery and regeneration process of the positive active material, it is environmentally friendly, and in particular, the initial washing process is omitted, resulting in excellent economic efficiency and productivity.

[0236] The secondary battery of the present invention may, for example, have a charging efficiency of 91% or less and a charging capacity of 224.5 mAh / g or more, preferably a charging efficiency of 89.5 to 91% and a charging capacity of 224.5 to 230 mAh / g, and has the advantage of excellent capacity characteristics, resistance characteristics, and lifespan characteristics within this range.

[0238] The secondary battery of the present invention may include all the contents of the positive electrode active material and the method for regenerating the same described above. Therefore, a redundant description thereof is omitted herein.

[0240] Hereinafter, preferred embodiments are presented to aid in understanding the present invention; however, the following embodiments are merely illustrative of the invention, and it is obvious to those skilled in the art that various changes and modifications are possible within the scope and spirit of the invention, and that such variations and modifications fall within the scope of the appended claims.

[0242] [Example]

[0243] Example 1

[0244] The discarded anode scrap (current collector: aluminum foil, anode active material: NCM-based lithium composite transition metal oxide with a nickel content of 85 mol%) after anode plate stamping was crushed, and then heat-treated at 350°C for 2 hours with 95% pure oxygen introduced, followed by raising the temperature to 590°C and heat-treating for 30 minutes to remove the binder and conductive material, separate the current collector and the anode active material, and recover the anode active material. Here, the rate of temperature increase to reach the heat treatment temperature was 5°C / min, and oxygen was supplied at 3 L / min. In addition, the purity of the oxygen under the above oxygen atmosphere was 95%.

[0245] LiOH, a lithium precursor, was added to the recovered cathode active material in an amount capable of providing 12 mol% of lithium when the total lithium in the raw material cathode active material is 100 mol%, and the material was annealed in air at a calcination temperature of 700 ℃ for 5 hours. Here, air was supplied at a rate of 3 L / min.

[0246] The annealed positive electrode active material and distilled water were mixed in a weight ratio of 1:2 and stirred for 5 minutes under conditions of 300 rpm, after which a solid was obtained by vacuum filtration. The solid was vacuum dried at 130 ℃ for 12 hours to obtain a washed positive electrode active material.

[0247] The above-mentioned washed cathode active material was coated with boric acid and heated at 300°C for 5 hours to produce a final regenerated cathode active material. Here, boric acid was added in an amount corresponding to 0.1 parts by weight based on 100 parts by weight of the total cathode active material, the temperature rise rate until reaching the heat treatment temperature was 2°C / min, and air was supplied at 3 L / min.

[0248] Here, the molar ratio of lithium to other metals within the positive electrode active material was measured using an IC analyzer. While general IC analyzers commonly used in laboratories can be used for these measurements, there is no variation depending on the measuring device or method.

[0250] Example 2

[0251] The discarded anode scrap (current collector: aluminum foil, anode active material: NCM-based lithium composite transition metal oxide with a nickel content of 85 mol%) after anode plate die stamping was crushed, and oxidative heat treatment was performed at 590°C for 30 minutes with the introduction of 95% pure oxygen to remove the binder and conductive material, separate the current collector and the anode active material, and then recover the anode active material. Here, the temperature rise rate until reaching the heat treatment temperature was 5°C / min, and oxygen was supplied at 3 L / min.

[0252] LiOH, a lithium precursor, was added to the recovered cathode active material in an amount capable of providing 12 mol% of lithium when the total lithium in the raw material cathode active material is 100 mol%, and the material was annealed in air at a calcination temperature of 700 ℃ for 5 hours. Here, air was supplied at a rate of 3 L / min.

[0253] The annealed positive electrode active material and distilled water were mixed in a weight ratio of 1:2 and stirred for 5 minutes under conditions of 300 rpm, after which a solid was obtained by vacuum filtration. The solid was vacuum dried at 130 ℃ for 12 hours to obtain a washed positive electrode active material.

[0254] The above-mentioned washed cathode active material was coated with boric acid and heated at 300°C for 5 hours to produce a final regenerated cathode active material. Here, boric acid was added in an amount corresponding to 0.1 parts by weight based on 100 parts by weight of the total cathode active material, the temperature rise rate until reaching the heat treatment temperature was 2°C / min, and air was supplied at 3 L / min.

[0256] Comparative Example 1

[0257] The discarded anode scrap (current collector: aluminum foil, anode active material: NCM-based lithium composite transition metal oxide with a nickel content of 85 mol%) after anode plate die-cutting was crushed and heat-treated in air at 590°C for 30 minutes to remove the binder and conductive material, separate the current collector and the anode active material, and then recover the anode active material. Here, the temperature rise rate until reaching the heat treatment temperature was 5°C / min, and air was supplied at 3 L / min.

[0258] LiOH, a lithium precursor, was added to the recovered cathode active material in an amount capable of providing 12 mol% of lithium when the total lithium in the raw material cathode active material is 100 mol%, and the material was annealed in air at a calcination temperature of 700 ℃ for 5 hours. Here, air was supplied at a rate of 3 L / min.

[0259] The annealed positive electrode active material and distilled water were mixed in a weight ratio of 1:2 and stirred for 5 minutes under conditions of 300 rpm, after which a solid was obtained by vacuum filtration. The solid was vacuum dried at 130 ℃ for 12 hours to obtain a washed positive electrode active material.

[0260] The above-mentioned washed cathode active material was coated with boric acid and heated at 300°C for 5 hours to produce a final regenerated cathode active material. Here, boric acid was added in an amount corresponding to 0.1 parts by weight based on 100 parts by weight of the total cathode active material, the temperature rise rate until reaching the heat treatment temperature was 2°C / min, and air was supplied at 3 L / min.

[0262] Comparative Example 2

[0263] The above Comparative Example 1 was carried out in the same manner as Comparative Example 1, except that the annealing step was performed at 730 ℃.

[0265] Comparative Example 3

[0266] The above Comparative Example 1 was carried out in the same manner as Comparative Example 1, except that the annealing step was performed at 750 ℃.

[0268] [Test Example I: Residual Fluorine (F) Content]

[0269] The fluorine (F) content remaining in the regenerated cathode active materials obtained in Examples 1 and 2 and Comparative Examples 1 to 3 was measured using an IC analyzer, and the results are shown in Table 1 below. At this time, the measurement can be performed using a general IC analyzer commonly used in laboratories, but there is no deviation depending on the measuring device or method.

[0271] division F (weight%) Example 1 0.52 Example 2 0.55 Comparative Example 1 0.69 Comparative Example 2 0.66 Comparative Example 3 0.62

[0272] As can be seen in Table 1 above, it was found that the residual fluorine content of Examples 1 and 2 according to the present invention was reduced compared to Comparative Examples 1 to 3. In particular, Example 1, in which the oxidation heat treatment step was divided into two stages, showed a greater reduction in residual fluorine content.

[0274] [Test Example II: CHC Cell Evaluation]

[0275] The electrochemical performance of the regenerated cathode active materials obtained in Example 1 and Comparative Examples 1 to 3 was measured through CHC cell evaluation as described below, and the results are shown in Figures 2 to 4 below.

[0276] * CHC cell manufacturing: 97.5 wt% of regenerated cathode active material, 1.15 wt% of carbon black as a conductive material, and 1.35 wt% of PVdF as a binder were weighed and mixed with NMP to make a slurry. The cathode was manufactured by coating this onto aluminum foil, and a cell (Coin Half Cell, CHC) was manufactured including an electrolyte with a weight ratio of ethylene carbonate (EC):dimethyl carbonate (DMC):ethyl methyl carbonate (EMC) = 3:4:3 and other additives. The manufactured CHC was aged at 25°C for 10 hours, then charged to 4.25 V with a 0.05 C cut-off using a constant current of 0.1 C in CC-CV mode, discharged until it reached 3 V using a constant current of 0.1 C to undergo activation, and then a cycle evaluation was performed.

[0277] * Measurement of capacity retention rate at high temperature (45 ℃): Each CHC prepared from the regenerated cathode active material obtained in Example 1 and Comparative Examples 1 to 3 was formed at a rate of 0.1C, and then charged to 4.25 V with a constant current of 0.33C at 45 ℃ with a 0.05C cut-off. Afterward, discharge was performed to 2.5 V with a constant current of 0.33C. The above charging and discharging behavior was defined as one cycle, and this cycle was repeated 100 or 200 times. The discharge capacity after one cycle and the discharge capacity after 100 or 200 cycles were measured using a PNE-05-0.1 charge / discharger (Manufacturer: PNE Solution Co., Ltd., 5V, 0.1A), and the discharge capacity after one cycle was set as the initial capacity. Afterwards, the capacity retention rate was calculated by comparing the 100th or 200th discharge capacity with the initial capacity (100%) using the following mathematical formula 1, and the results are shown in Figure 2 below.

[0278] [Mathematical Formula 1]

[0279] Capacity Retention Rate (%) = (Discharge Capacity after High-Temperature Cycle / Initial Discharge Capacity) * 100

[0280] * Measurement of resistance increase rate at high temperature (45 ℃): Each CHC prepared from the regenerated cathode active material obtained in Example 1 and Comparative Examples 1 to 3 was formed at a rate of 0.1C, and then charged to 4.25 V with a constant current of 0.33C at 45 ℃ with a 0.05C cut-off. Subsequently, discharge was performed to 2.5 V with a constant current of 0.33C. The above charging and discharging behavior was defined as one cycle, and the degree of resistance increase was measured while repeating this cycle 100 or 200 times. The resistance increase rate was calculated using the following Equation 2, and the results are shown in Figure 3 below.

[0281] [Mathematical Formula 2]

[0282] Resistance increase rate (%) = {(DCIR2 - DCIR1) / DCIR1} * 100

[0283] (In the above Equation 2, DCIR1 represents the measured resistance (Ohm) at 1 cycle, and DCIR2 represents the measured resistance (Ohm) at 100 or 200 cycles.)

[0284] * Normalized in situ retention (%): The normalized in situ retention was calculated using the following mathematical formula 4.

[0285] [Mathematical Formula 4]

[0286] Normalized In-situ Retention Rate (%) = [{(Real-time capacity in the corresponding cycle / Capacity in the first cycle) * 100} / Capacity retention rate of fresh cathode active material] * 100

[0288] As shown in Figure 2 below, Example 1 according to the present invention had a superior capacity retention rate compared to Comparative Examples 1 to 3.

[0289] In addition, as shown in Figure 3 below, it was confirmed that Example 1 according to the present invention had a lower resistance increase rate compared to Comparative Examples 1 to 3.

[0290] In addition, as shown in Fig. 4 below, Example 1 according to the present invention had superior efficiency, charging capacity, and normalized in situ retention rate compared to Comparative Examples 1 to 3. Explanation of the symbols

[0292] 10 : Whole house 20: Active material layer 30: Anode sheet 40 : Positive plate 50 : Anode Scrap

Claims

Claim 1 delete Claim 2 delete Claim 3 delete Claim 4 delete Claim 5 delete Claim 6 delete Claim 7 A method for regenerating an anode active material, comprising: a step of recovering an anode active material within a layer formed on a current collector by oxidizing a waste anode by introducing oxygen to perform oxidative heat treatment, thereby thermally decomposing a binder and a conductive material within the anode active material layer; a step of adding a lithium precursor to the recovered anode active material and annealing it in oxygen or air at 400 to 1000 ℃; and a step of washing the annealed anode active material; wherein the oxidative heat treatment is characterized by performing a first heat treatment at 300 to 450 ℃ for 10 minutes to 3 hours, followed by a second heat treatment at 500 to 650 ℃ for 10 minutes to 2 hours. Claim 8 A method for regenerating a positive electrode active material according to claim 7, characterized in that the positive electrode active material layer contains 60 mol% or more of nickel (Ni) based on 100 mol% of the total remaining metals excluding lithium (Li). Claim 9 delete Claim 10 delete Claim 11 delete Claim 12 A method for regenerating an anode active material according to claim 7, characterized in that the anode active material recovered from the annealing step contains crystalline LiF. Claim 13 A method for regenerating a positive electrode active material according to claim 7, characterized in that the lithium precursor comprises one or more of LiOH, Li2CO3, LiNO3, and Li2O. Claim 14 A method for regenerating a positive electrode active material according to claim 7, wherein the lithium precursor is added in an amount capable of providing 1 mol% to 40 mol% of lithium when the total lithium in the positive electrode active material layer formed on the current collector is 100 mol%. Claim 15 A method for regenerating an anode active material according to claim 7, characterized in that the annealing is performed at 450 to 710 ℃. Claim 16 A method for regenerating an anode active material according to claim 7, characterized in that the weight ratio of the anode active material annealed in the washing step to the washing solution is 1:0.5 to 1:

10. Claim 17 A method for regenerating an anode active material according to claim 7, characterized in that the method for regenerating the anode active material includes the step of surface coating the washed anode active material. Claim 18 A method for regenerating an anode active material according to claim 17, characterized in that the surface coating comprises coating one or more of a metal, an organometallic component, and a carbon component on the surface in a solid or liquid manner, followed by heat treatment at 100 to 1200 ℃. Claim 19 delete

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