Lithium-ion secondary battery recycling method

Abstract

A lithium-ion secondary battery recycling method, according to one embodiment of the present invention, may comprise the steps of: leaching lithium by inputting waste battery crushed material into a leach solution; drying residue which is obtained by filtering the solution; preparing a NCM solution by inputting the dried residue in a leach solution and leaching same for 3-5 hours; forming an AlOH3 residue by increasing the pH of the NCM solution to 5 or higher; crystallizing the AlOH3 residue into Al2O3 by heat-treating same at 200°C or higher; mixing the crystallized powder with the waste battery crushed material; and heat-treating the mixed waste battery crushed material at 400-1000°C.

Description

Lithium-ion secondary battery recycling method

[0001] The present invention relates to a method for recycling waste lithium-ion secondary batteries, specifically a method for recycling waste lithium-ion secondary batteries that reduces the amount of tar generated during the heat treatment process of waste batteries.

[0002] With the recent explosive increase in demand for electric vehicles, interest in recycling methods for batteries from end-of-life electric vehicles (EVs) has also surged. EV batteries contain large quantities of valuable metals such as nickel, cobalt, manganese, and lithium, making their recycling value very high. While these metals are essential for the battery manufacturing process, their production can have harmful environmental impacts. In particular, environmental issues such as greenhouse gas emissions and ecosystem destruction arising from mining operations are serious. Therefore, the development of recycling technologies for end-of-life batteries is essential for sustainable future development.

[0003] Waste batteries consist of five major components: current collectors, cathode materials, anode materials, separators, and electrolytes. Therefore, when cells are shredded, these five materials are primarily produced as waste. However, when battery packs or modules are shredded, various outer materials such as plastic, aluminum, and iron are additionally included. Among these outer materials, thermosetting plastics such as polystyrene and polyurethane, which possess excellent heat resistance, pose a particular problem.

[0004] As the content of these plastics in shredded batteries increases, they become a major source of environmental pollutant emissions during the black powder manufacturing process. Although a heat treatment process is essential for black powder production, thermosetting plastics contained in waste batteries do not completely decompose by heat and form tar. The generation of tar reduces process efficiency and causes additional environmental pollution problems.

[0005] The objective of the present invention to solve the aforementioned problem is to provide a method for recycling lithium-ion secondary batteries that reduces tar generated during heat treatment of waste batteries by using an NCM leaching agent extracted from waste batteries as a catalyst.

[0006] However, the problems that the present invention aims to solve are not limited to those mentioned above, and other unmentioned problems will be clearly understood by those skilled in the art from the description below.

[0007] As a means to achieve the above-mentioned purpose, a lithium-ion secondary battery recycling method according to one embodiment of the present invention may include the steps of: introducing crushed waste battery material into a leaching solution to leach lithium; drying the residue obtained by filtering the solution; introducing the dried residue into a leaching solution and leaching for 3 to 5 hours to prepare an NCM solution; raising the pH of the NCM solution to 5 or higher to form an AlOH3 residue; heat-treating the AlOH3 residue at 200°C or higher to crystallize it into Al2O3; mixing the crystallized powder with crushed waste battery material; and heat-treating the mixed crushed waste battery material at 400 to 1000°C.

[0008] In a method for recycling a lithium-ion secondary battery according to one embodiment of the present invention, the lithium leaching step may include leaching the crushed waste battery material in a sulfuric acid solution of 1.0 to 2.0 M for 1.5 to 2.5 hours.

[0009] In a method for recycling a lithium-ion secondary battery according to one embodiment of the present invention, the step of preparing the NCM solution may include leaching the dried residue in a 1.5 to 2.5 M sulfuric acid solution for 3.5 to 4.5 hours.

[0010] In a method for recycling a lithium-ion secondary battery according to one embodiment of the present invention, the AlOH3 residue may comprise, in weight%, Ni: 2.00 to 5.00%, Co: 0.20 to 0.60%, Mn: 0.20 to 0.60%, Al: 25.0 to 40.0%, and Fe: 2.00 to 4.00%.

[0011] In a method for recycling a lithium-ion secondary battery according to one embodiment of the present invention, a catalyst comprising Ni, Co, and Mn can be entirely dispersed on the surface of Al2O3.

[0012] In a method for recycling a lithium-ion secondary battery according to one embodiment of the present invention, the powder in the step of mixing the crystallized powder with the waste battery crushed material may be added in an amount of 0.5% by weight or more.

[0013] In a method for recycling lithium-ion secondary batteries according to one embodiment of the present invention, the weight loss may be 10.00% or less when performing thermogravimetric analysis (TGA) before and after the heat treatment step of the mixed waste battery crushed material.

[0014] According to one embodiment of the present invention, a method for recycling lithium-ion secondary batteries can be provided that reduces tar generated during heat treatment of waste batteries by using an NCM leaching agent extracted from waste batteries as a catalyst.

[0015] The effects obtainable from this invention are not limited to those mentioned above, and other unmentioned effects will be clearly understood by those skilled in the art to which this invention pertains from the description below.

[0016] Figure 1 (a) shows the results of thermogravimetric analysis (TGA) after heat treatment of crushed waste batteries before catalyst addition, and (b) shows the results of thermogravimetric analysis (TGA) after heat treatment of crushed waste batteries after catalyst addition.

[0017] Preferred embodiments of the present invention are described below. However, embodiments of the present invention may be modified in various other forms, and the technical concept of the present invention is not limited to the embodiments described below. Furthermore, the embodiments of the present invention are provided to more completely explain the present invention to those with average knowledge in the relevant technical field.

[0018] The terms used in this application are used merely to describe specific examples. For this reason, singular expressions include plural expressions unless the context clearly requires them to be singular. Additionally, it should be noted that terms such as “comprising” or “comprising” used in this application are used to clearly indicate the presence of features, steps, functions, components, or combinations thereof described in the specification, and are not used to preliminarily exclude the existence of other features, steps, functions, components, or combinations thereof.

[0019] Meanwhile, unless otherwise defined, all terms used in this specification shall be understood to have the same meaning as generally understood by those skilled in the art to which the present invention pertains. Accordingly, unless explicitly defined in this specification, specific terms should not be interpreted in an overly ideal or formal sense.

[0020] Additionally, terms such as "about," "substantially," etc., in this specification are used to mean at or near the stated value when inherent manufacturing and material tolerances are presented in the said sense, and are used to prevent unscrupulous infringers from unfairly exploiting the disclosed content in which precise or absolute values ​​are mentioned to aid in understanding the invention.

[0021] Unless otherwise specifically stated in this specification, the % indicating the content of each element is based on weight. The reasons for limiting the compositional range of each alloying element are explained below.

[0022] The general process for recycling waste batteries is as follows. First, the modules within the battery pack are separated, and then the modules are broken down into individual cells. Subsequently, the cells are completely discharged through a saltwater discharge process and then crushed to produce black powder. Black powder is a composite material containing various metals, from which valuable metals can be extracted through a metal recovery process. However, this process requires significant labor and suffers from low efficiency because it necessitates breaking down the materials down to the cell level.

[0023] Cell-to-pack technology is garnering attention due to recent advancements in battery technology. This technology eliminates the battery module stage by directly assembling battery cells into a pack. In conventional battery pack designs, battery cells are first assembled into modules, and then these modules are assembled into a pack. However, by integrating cells directly into a pack without modules, cell-to-pack technology can improve space efficiency and energy density. Nevertheless, as battery pack structures become more robust to safely protect batteries from external impacts, disassembling them at the cell level is becoming increasingly difficult. Consequently, many researchers are focusing on developing processes to crush entire battery packs or modules to produce black powder.

[0024] Waste batteries contain five major components: current collectors, cathode materials, anode materials, separators, and electrolytes. Therefore, when cells are shredded, these five materials are primarily produced as waste. However, when battery packs or modules are shredded, various outer materials such as plastic, aluminum, and iron are additionally included. Among these outer materials, thermosetting plastics such as polystyrene and polyurethane, which possess excellent heat resistance, pose a particular problem.

[0025] As the content of these plastics in shredded batteries increases, they become a major source of environmental pollutant emissions during the black powder manufacturing process. Although a heat treatment process is essential for black powder production, thermosetting plastics contained in waste batteries do not completely decompose by heat and form tar. The generation of tar reduces process efficiency and causes additional environmental pollution problems.

[0026] The Ni, Co, and Mn metals contained in spent batteries can act as catalysts to crack hydrocarbons and form H2, CO2, CO, and the like. During the process of converting black powder into raw materials, a leaching process is performed to dissolve valuable metals using acid; since the resulting solution contains Ni, Co, and Mn metals, it can be utilized as a catalyst. This catalyst is not only economical as it does not require high purity, but also eliminates the need for additional post-use processing since it contains only components derived from spent batteries, even when mixed into the recycling process. Therefore, using NCM-based catalysts made from spent batteries allows for the economical reduction of tar generation by cracking hydrocarbons released during the decomposition of thermosetting plastics.

[0027] A lithium-ion secondary battery recycling method according to one embodiment of the present invention may use an NCM leaching agent extracted from a waste battery as a catalyst and Al2O3 as a catalyst support. Accordingly, the catalyst can reduce the amount of tar generated by cracking hydrocarbons that occur during the heat treatment of thermosetting plastics in the waste battery.

[0028] Hereinafter, embodiments according to the present invention will be described in detail with reference to the attached drawings.

[0029] A method for recycling a lithium-ion secondary battery according to one embodiment of the present invention may include the steps of: introducing crushed waste battery material into a leaching agent to leach lithium; drying a residue obtained by filtering the solution; introducing the dried residue into a leaching agent and leaching for 3 to 5 hours to prepare an NCM solution; raising the pH of the NCM solution to 5 or higher to form an AlOH3 residue; heat-treating the AlOH3 residue at 200°C or higher to crystallize it into Al2O3; mixing the crystallized powder with crushed waste battery material; and heat-treating the mixed crushed waste battery material at 400 to 1000°C.

[0030] Waste batteries can be prepared by completely discharging, dismantling, and crushing them. Crushing the waste batteries increases the surface area in contact with oxygen, thereby improving reaction efficiency.

[0031] The above waste battery crushed material may include not only crushed materials of the current collector, positive electrode material, negative electrode material, separator, and electrolyte as described above, but also defective products generated during the manufacturing process, residues within the manufacturing process, and generated debris.

[0032] The above-mentioned crushed waste battery material can be introduced into a leaching solution to leach lithium. The leaching agent included in the leaching solution is preferably an acid selected from sulfuric acid, hydrochloric acid, nitric acid, methanesulfonic acid, oxalic acid, and citric acid, or a combination of at least two of these, for example, a combination of nitric acid and hydrochloric acid. In another preferred embodiment, the leaching agent may include an inorganic acid such as sulfuric acid, hydrochloric acid, or nitric acid; an organic acid such as methanesulfonic acid, oxalic acid, citric acid, aspartic acid, malic acid, ascorbic acid, or glycine; or a base such as ammonia, an aqueous amine solution, ammonia, ammonium carbonate, or a mixture of ammonia and carbon dioxide. In one embodiment, the leaching agent includes an aqueous acid such as an inorganic or organic aqueous acid. In another embodiment, the leaching agent includes a base, preferably ammonia or an amine.

[0033] In a method for recycling a lithium-ion secondary battery according to one embodiment of the present invention, the lithium leaching step may include leaching in a 1.0 to 2.0 M sulfuric acid solution for 1.5 to 2.5 hours. The residue obtained by filtering the solution may be dried at about 100°C.

[0034] The above-mentioned dried residue may be introduced into a leaching solution and leached for 3 to 5 hours to prepare an NCM solution. The leaching agent included in the leaching solution is preferably an acid selected from sulfuric acid, hydrochloric acid, nitric acid, methanesulfonic acid, oxalic acid, and citric acid, or a combination of at least two of these, for example, a combination of nitric acid and hydrochloric acid. In another preferred form, the leaching agent is an inorganic acid such as sulfuric acid, hydrochloric acid, or nitric acid; an organic acid such as methanesulfonic acid, oxalic acid, citric acid, aspartic acid, malic acid, ascorbic acid, or glycine; or a base such as ammonia, an aqueous solution of an amine, ammonia, ammonium carbonate, or a mixture of ammonia and carbon dioxide. In one form, the leaching agent comprises an aqueous acid such as an inorganic or organic aqueous acid. In another form, the leaching agent comprises a base, preferably ammonia or an amine.

[0035] In a method for recycling a lithium-ion secondary battery according to one embodiment of the present invention, the step of preparing the NCM solution may include leaching the dried residue in a 1.5 to 2.5 M sulfuric acid solution for 3.5 to 4.5 hours.

[0036] Ni, Co, Mn, etc. contained in the dried residue can be leached out through the above leaching step. The Ni, Co, and Mn obtained from the waste battery can subsequently act as catalysts during the heat treatment of the crushed waste battery material. Thermosetting plastics such as polystyrene and polyurethane within the crushed waste battery material do not completely decompose by heat and form tar. At this time, the catalyst increases the reaction rate of cracking hydrocarbons, thereby reducing incomplete combustion and reducing the amount of tar produced.

[0037] The pH value of the above NCM solution can be adjusted to 5 or higher, preferably 5.0 to 5.5, to form an AlOH3 residue. The pH value can be determined by conventional means, for example, by potential measurement, and refers to the pH value of the continuous liquid phase at 20°C. Adjustment of the pH value is generally performed by dilution with water, addition of a base, addition of an acid, or a combination thereof. Examples of suitable bases are ammonia and alkali metal hydroxides, for example, LiOH, NaOH, or KOH, in solid form, for example, pellets, or preferably as aqueous solutions. A combination of at least two of these, for example, a combination of ammonia and aqueous caustic soda, is also possible. Preferably, this is performed by the addition of one or more of sodium hydroxide, lithium hydroxide, ammonia, and potassium hydroxide.

[0038] In a method for recycling a lithium-ion secondary battery according to one embodiment of the present invention, the AlOH3 residue may comprise, in weight%, Ni: 2.00 to 5.00%, Co: 0.20 to 0.60%, Mn: 0.20 to 0.60%, Al: 25.0 to 40.0%, and Fe: 2.00 to 4.00%.

[0039] Table 1 below shows the results of inductively coupled plasma analysis of the main components in the AlOH3 residue in a lithium-ion secondary battery recycling method according to one embodiment of the present invention.

[0040] Ni (wt%) Co (wt%) Mn (wt%) Al (wt%) Fe (wt%) Content 3.36 0.34 0.31 36.32 48

[0041] The above AlOH3 residue can be crystallized into Al2O3 by heat-treating it at 200°C or higher. Through the above heat treatment, AlOH3 particles Ni, Co, and Mn catalysts fixed to the surface can aggregate on the surface of Al2O3 particles.

[0042] In a method for recycling a lithium-ion secondary battery according to one embodiment of the present invention, a catalyst comprising Ni, Co, and Mn can be entirely dispersed on the surface of Al2O3.

[0043] As Al2O3 particles obtained from crushed waste batteries act as a catalyst support, the catalyst can be fixed in the reaction environment to prevent loss. Additionally, since the catalyst containing Ni, Co, and Mn is dispersed evenly on the surface of the Al2O3 particles, the surface area of ​​the catalyst is increased, thereby increasing the reaction rate.

[0044] The powder containing the crystallized Al2O3 mentioned above can be mixed with crushed waste battery material.

[0045] In a method for recycling a lithium-ion secondary battery according to one embodiment of the present invention, the powder in the step of mixing the crystallized powder with the waste battery crushed material may be added in an amount of 0.5% by weight or more.

[0046] The above-mentioned mixed crushed waste battery material can be heat-treated at 400 to 1000°C. The heat treatment can be performed in an Ar atmosphere. Thermal decomposition of plastics within the crushed waste battery material can occur at 400 to 1000°C. At this time, the cracking of hydrocarbons can be promoted by a catalyst containing Ni, Co, and Mn dispersed on the surface of Al2O3 particles. Consequently, incomplete combustion of plastics within the crushed waste battery material is reduced, thereby reducing the amount of tar generated.

[0047] In a method for recycling lithium-ion secondary batteries according to one embodiment of the present invention, the weight loss may be 10.00% or less when performing thermogravimetric analysis (TGA) before and after the heat treatment step of the mixed waste battery crushed material.

[0048] Figure 1(a) shows the results of thermogravimetric analysis (TGA) after heat-treating the waste battery crushed material mixed with the catalyst before catalyst addition at 600°C or higher in an Ar atmosphere. Figure 1(b) shows the results of thermogravimetric analysis (TGA) after heat-treating the waste battery crushed material after catalyst addition. In Figures 1(a) and (b), the solid line represents the weight of the waste battery crushed material, and the dotted line represents the temperature.

[0049] Referring to Figures 1 (a) and (b), in case (a) where no catalyst was added, incompletely combusted thermosetting plastic in the shredded waste battery remained in the form of tar, resulting in a weight loss of 21.84% of the shredded waste battery reactant. On the other hand, in case (b) where a catalyst was added according to one embodiment of the present invention, the thermal decomposition of plastic occurred well due to the catalyst, resulting in a weight loss of 4.32% of the shredded waste battery reactant.

[0050] Although exemplary embodiments of the present invention have been described above, the present invention is not limited thereto, and those skilled in the art will understand that various changes and modifications are possible within the scope and concept of the claims set forth below.

Claims

1. A step of immersing crushed waste batteries in a leaching solution to leach lithium; A step of drying the residue obtained by filtering the above solution; A step of preparing an NCM solution by introducing the dried residue into an leaching solution and leaching for 3 to 5 hours; A step of raising the pH of the above NCM solution to 5 or higher to form an AlOH3 residue; A step of crystallizing AlOH3 residue into Al2O3 by heat-treating it at 200℃ or higher; A step of mixing the crystallized powder with crushed waste battery material; and A method for recycling lithium-ion secondary batteries, comprising the step of heat-treating mixed waste battery crushed material at 400 to 1000°C.

2. In Claim 1, A method for recycling lithium-ion secondary batteries, wherein the lithium leaching step comprises leaching the crushed waste battery material in a 1.0 to 2.0 M sulfuric acid solution for 1.5 to 2.5 hours.

3. In Claim 1, A method for recycling a lithium-ion secondary battery, wherein the step of preparing the above NCM solution comprises leaching the dried residue in a 1.5 to 2.5 M sulfuric acid solution for 3.5 to 4.5 hours.

4. In Claim 1, A method for recycling a lithium-ion secondary battery, wherein the above AlOH3 residue comprises, in weight%, Ni: 2.00 to 5.00%, Co: 0.20 to 0.60%, Mn: 0.20 to 0.60%, Al: 25.0 to 40.0%, and Fe: 2.00 to 4.00%.

5. In Claim 1, A method for recycling lithium-ion secondary batteries in which a catalyst containing Ni, Co, and Mn is entirely dispersed on the surface of the above Al2O3.

6. In Claim 1, A method for recycling lithium-ion secondary batteries, comprising adding at least 0.5% by weight of the powder in the step of mixing the crystallized powder with crushed waste battery material.

7. In Claim 1, A lithium-ion secondary battery recycling method in which the weight loss is 10.00% or less when analyzed by thermogravimetric analysis (TGA) before and after the heat treatment step of the mixed waste battery crushed material.

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