Methods for recovering valuable materials from lithium-ion secondary batteries

Abstract

To provide a method for recovering valuable materials from a lithium-ion secondary battery, where the recovery rate for copper can be improved.SOLUTION: A method for recovering valuable materials from a lithium-ion secondary battery comprises a heating step for heating a lithium-ion secondary battery, a crushing step for crushing after the heating, and any one or more steps for sieving, magnetic sorting and gravity sorting after the crushing. In the crushing step, the crushing is performed such that the size of crushed materials is 20 mm or less.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to a method for recovering valuable substances from a lithium-ion secondary battery.

Background Art

[0002] Conventionally, lithium-ion secondary batteries have been used as batteries for small mobile devices such as mobile phones, notebook computers, and video cameras. In recent years, as part of the efforts towards decarbonization, electric vehicles have been becoming more popular, and large in-vehicle lithium-ion secondary batteries are being mass-produced. Also, recently, in order to improve safety and volumetric energy density, research and development of new materials for the negative electrode and positive electrode and research on solid electrolytes have been actively carried out.

[0003] Generally, a lithium-ion secondary battery is composed of a positive electrode, a negative electrode, a separator, an electrolyte, etc. For the positive electrode, a material in which an active material such as lithium, cobalt, nickel, etc. is coated together with a binder on an aluminum foil (positive electrode current collector) is used. For the negative electrode, a material in which an active material such as graphite is coated together with a binder on a copper foil (negative electrode current collector) is used. And these are housed in a metal exterior material.

[0004] Since lithium-ion secondary batteries contain valuable substances such as lithium, cobalt, nickel, copper, and aluminum, after being repeatedly charged and discharged and becoming used, valuable substances are recovered from them. Regarding the recovery method, for example, Patent Document 1 describes a method for simply and efficiently recovering valuable substances such as copper and aluminum from a lithium-ion secondary battery. Also, Patent Documents 2 and 3 disclose methods for separating and recovering copper, aluminum, and an active material from a used lithium-ion battery.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

[0006] Generally, when recovering valuable materials from lithium-ion secondary batteries, the battery is first discharged until the voltage drops below a certain level, and then heated to decompose and remove the separator and electrolyte. Next, the battery is crushed while still contained in its casing, and then the metals contained in the casing, current collector, and active material (hereinafter also referred to as electrode powder) are separated by sieving, specific gravity separation, magnetic separation, etc. Through these processes, copper, aluminum, iron, electrode powder (lithium, nickel, cobalt, manganese, titanium, niobium and other rare metals, graphite, silicon, etc.) can be separated. Since the quality of rare metals contained in electrode powder is expected to decline in the future, the recovery of copper, aluminum, and iron is extremely important in the recycling of lithium-ion secondary batteries.

[0007] However, when the casing material of a lithium-ion secondary battery is crushed, as shown in Figure 1, the copper foil that makes up the current collector becomes embedded in the iron-based metals (steel, stainless steel, etc.) and aluminum chunks that make up the casing material. Furthermore, as shown in Figure 2, copper chunks such as sealing bolts and conductive busbars attached to the casing material cannot be separated individually from the casing material, resulting in a problem where the recovery rate of valuable copper is significantly reduced. In addition, copper embedded in iron-based metals is recycled from iron. This created a problem where it also hindered the process.

[0008] This invention has been made in view of these circumstances, and its objective is to provide a method for recovering valuable materials from lithium-ion secondary batteries that can improve the recovery rate of copper. [Means for solving the problem]

[0009] To solve the above problems, the present invention provides the following embodiments. [1] A method for recovering valuable materials from a lithium-ion secondary battery, comprising a heating step of heating the lithium-ion secondary battery, a crushing step of crushing the battery after heating, and one or more steps of sieving, magnetic separation, and specific gravity separation after crushing, characterized in that in the crushing step, the crushed material is crushed to a size of 20 mm or less. [2] The method for recovering valuable materials from lithium-ion secondary batteries according to [1] above, characterized in that a shear crusher is used in the crushing step. [3] A method for recovering valuable materials from lithium-ion secondary batteries according to [1] or [2] above, characterized in that a shear crusher capable of adjusting particle size is used in the crushing step. [4] A method for recovering valuable materials from lithium-ion secondary batteries according to [1] or [2] above, characterized in that a three-axis or four-axis shear crusher is used in the crushing step. [5] The method for recovering valuable materials from a lithium-ion secondary battery according to [1] above, characterized in that the crushing step includes two or more consecutive crushing steps. [6] After the crushing step, a step of sieving to separate the electrode material powder which is the subsieving product; a step of magnetically separating the sieving product separated by the sieving to separate the iron-based metal which is the magnetic material; a step of specific gravity separation of the non-magnetic material separated by the magnetic separation to separate the heavy product and the light product; a step of magnetically separating and / or specific gravity separation of the heavy product separated by the specific gravity separation to separate the copper lumps and aluminum lumps; and a step of separating the material separated by the specific gravity separation A method for recovering valuable materials from a lithium-ion secondary battery according to [1] above, characterized by comprising the steps of: crushing the light products; sieving the crushed material obtained by the crushing to separate the electrode material powder which is the sieved product; separating the heavy products and light products by specific gravity separation of the sieved products separated by the sieving; and magnetically separating the light products separated by specific gravity separation to separate the copper foil which is a non-magnetic material and the aluminum foil which is a magnetic material. [7] A method for recovering valuable materials from lithium-ion secondary batteries according to [1] or [6] above, characterized in that the specific gravity separation is performed using wind separation or an air table. [Effects of the Invention]

[0010] According to the present invention, a method for recovering valuable materials from lithium-ion secondary batteries has the excellent effect of improving the recovery rate of copper. Furthermore, because the recovery rate of copper is improved, the amount of copper embedded in the iron decreases, and as a result, the quality of the recovered iron also improves. [Brief explanation of the drawing]

[0011] [Figure 1] This is a photograph showing copper foil embedded in the exterior material (a photograph of copper foil embedded in aluminum). [Figure 2] This photograph shows a state where the copper block-like object has not been separated from the exterior material (a photograph showing sealing bolts and conductive busbars still attached to the exterior material). [Figure 3] This is a flowchart illustrating a method for recovering valuable materials from lithium-ion secondary batteries in examples and comparative examples. [Modes for carrying out the invention]

[0012] The present invention will be described in detail below. The following description of the constituent elements is an example (representative example) of an embodiment of the present invention, and the present invention is not limited to these contents. Furthermore, it can be implemented with various modifications within the scope of its gist.

[0013] Lithium-ion rechargeable batteries typically consist of a positive electrode, a negative electrode, an electrolyte, and a separator. The battery functions through the movement of lithium ions in the electrolyte between the positive and negative electrodes. Typically, the positive electrode is formed by coating an aluminum foil current collector with a binder containing a positive electrode material such as lithium, nickel, cobalt, or manganese. The negative electrode, on the other hand, is formed by coating a copper foil current collector with a negative electrode material such as graphite or silicon. Titanium and niobium are also sometimes used as negative electrode materials. The positive electrode, negative electrode, electrolyte, and separator are housed in an casing made of iron-based metal or aluminum to form a single battery cell. The casing is fitted with copper sealing bolts and conductive busbars.

[0014] Lithium-ion rechargeable batteries used in vehicles such as electric vehicles have various types of battery cells, including prismatic, cylindrical, and laminated types. Multiple battery cells are assembled to form a battery module, and multiple battery modules are assembled to form a battery pack. Generally, mobile phones, notebook computers, and video cameras use small, prismatic battery cells. When recovering valuable materials from lithium-ion rechargeable batteries, battery cells, battery modules, and battery packs are processed without any particular distinction.

[0015] When recovering valuable materials from a lithium-ion secondary battery, usually, it is heated to decompose and remove organic substances such as the separator and electrolyte inside. After heating, it is crushed together with the outer packaging material, and the current collector (copper foil, aluminum foil, etc.) inside is finely crushed (cut), and at the same time, the electrode material powder adhering to the current collector is peeled off. After crushing, by appropriately combining sieving, magnetic separation, and specific gravity separation, iron-based metals, copper lumps, aluminum blocks, copper foils and aluminum foils constituting the current collector, and lithium, nickel, cobalt, manganese, graphite, titanium, niobium, silicon, etc. constituting the electrode material powder are separated and recovered.

[0016] Hereinafter, the method for recovering valuable materials according to the embodiments of the present invention will be described in detail. [Heating step] In the heating step, as long as at least the separator, electrolyte, and other organic substances contained in the lithium-ion secondary battery can be burned and removed, there are no particular restrictions on the temperature and atmosphere during heating. For example, the heating temperature can be in the range of 400°C or higher and 600°C or lower. Also, it can be heated in an oxidizing atmosphere or a non-oxidizing atmosphere. The heating time can be appropriately adjusted according to the shape and size of the lithium-ion secondary battery, the amount of the object to be heated, etc., and for example, it can be 0.5 to 6 hours. It can be heated without particularly distinguishing between battery cells, battery modules, battery packs, etc.

[0017] Also, before the heating step, the lithium-ion secondary battery can be discharged to reduce the remaining battery level to a certain level or lower. This is to prevent accidents due to explosion, ignition, and electric shock in subsequent steps. However, since the heating step can almost completely lose the function of the battery, discharging is merely an optional step.

[0018] [Crushing step] The heated lithium-ion secondary battery is crushed along with its casing, and the current collector is removed from the inside and crushed, while the electrode material powder attached to the current collector is separated. At this time, if the casing is crushed together, the copper foil of the current collector becomes caught and crushed (entangled) in the pieces of ferrous metal and aluminum chunks that make up the casing. Once caught, it becomes extremely difficult to separate the copper foil in the subsequent sorting process. In addition, copper chunks such as sealing bolts and conductive busbars attached to the casing are caught in the ferrous metal and aluminum chunks during crushing, making it impossible to separate the copper chunks from the casing individually, and it becomes extremely difficult to separate the copper chunks in the subsequent sorting process. Therefore, the crushing process should be carried out to remove as much copper as possible. It is important to separate the individual components without biting them together.

[0019] In the crushing process, the crushed material is crushed while adjusting the particle size so that the size of the crushed material is 20 mm or less. By adjusting the size of the crushed material to the above range, the inclusion of copper foil and copper lumps can be significantly reduced, and the copper recovery rate can be increased. Preferably, the size of the crushed material is 15 mm or less. More preferably, the size of the crushed material is 1 mm or more.

[0020] When crushing using a shear-type crusher for particle size adjustment, a screen with an opening is installed below the crushing blade, and the crushed material is circulated until it reaches a size that can pass through the opening. At this time, it is important to set the screen opening to about 20 mm or 15 mm and repeatedly crush the material until it passes through the screen opening to standardize the size of the crushed material. This suppresses the jamming of copper foil into ferrous metals and aluminum ingots, and enables the separation of copper lumps individually. Furthermore, it improves the separation efficiency in subsequent sorting processes. In particular, standardizing the size of the crushed material allows subsequent air sorting and gravity sorting using air tables to work more effectively.

[0021] In the case of a crusher without a screen, crushing is performed only once, resulting in unevenly sized crushed material and making it difficult to separate individual copper particles. Therefore, it is preferable to use a crusher equipped with a mechanism to adjust particle size, such as a screen. In addition to shear-type crushers, impact-type crushers also exist, but when using an impact-type crusher, the outer material is crushed, making it impossible to separate individual copper lumps, and copper foil tends to get jammed more easily. Therefore, it is preferable to use a shear-type crusher in the crushing process.

[0022] In the case of a shredder with a screen, the material that does not pass through the screen opening circulates within the shredder and is repeatedly shredded. At this time, the material accumulates in the gap between the shafts of the shredder, but the rotation of the shafts detaches the electrode material powder adhering to the current collector, which actually increases the separation efficiency. To increase the separation efficiency, it is preferable to use a three-shaft or four-shaft shredder. Furthermore, it is effective to perform the shredding process multiple times, such as primary shredding and secondary shredding, by continuously installing shear shredders or replacing the screen to gradually narrow the screen opening.

[0023] [Sieving] In embodiments of the present invention, sieving is performed after crushing as necessary. The purpose of sieving is not particularly limited; for example, it may be for the purpose of separating electrode material powder adhering to the current collector. Alternatively, it may be for the purpose of obtaining crushed material of an optimal size for subsequent specific gravity separation or magnetic separation.

[0024] The mesh size of the sieve can be set appropriately according to its purpose. For example, when separating electrode material powder, the mesh size can be set to 1 mm or more and 10 mm or less, thereby separating the electrode material powder as a sub-sieve product and transferring the sieve-up product to a subsequent sorting process.

[0025] [Magnetic separation] In embodiments of the present invention, magnetic separation is performed after crushing as necessary. The purpose of magnetic separation is not particularly limited; for example, it may be aimed at separating ferrous metals constituting the exterior material as magnetically attached materials. Alternatively, aluminum foil may be separated as magnetically attached materials and copper foil as non-magnetically attached materials.

[0026] The magnetic force used for magnetic separation can be set appropriately according to the purpose. For example, when separating ferrous metals, a magnet with a surface magnetic flux density of 0.3 Tesla or less can be used. Also, when separating aluminum foil as the magnetic material and copper foil as the non-magnetic material, the surface Magnets with a magnetic flux density of 0.8 Tesla or higher can be used.

[0027] [Specific gravity sorting] In embodiments of the present invention, gravity separation is performed as needed after crushing. The purpose of gravity separation is not particularly limited; for example, lumpy materials such as exterior materials, bolts, and busbars can be separated as heavy products, and foil-like materials such as current collectors can be separated as light products.

[0028] The methods and conditions for specific gravity separation can be set appropriately according to the purpose. For example, it can be carried out using an air table, aerosol separator, fluidized bed separator, or heavy liquid separator. An air table, as described in Patent Document 1, separates objects using airflow and vibration. By performing this separation, copper lumps can be separated.

[0029] After crushing, various valuable materials can be separated and recovered by combining sieving, magnetic separation, and specific gravity separation as described above. There are no particular restrictions on the order or number of times sieving, magnetic separation, and specific gravity separation are performed, and they can be appropriately selected depending on the material. For example, after specific gravity separation, the method or conditions of specific gravity separation can be changed and specific gravity separation can be performed again. Alternatively, magnetic separation can be used to separate magnetically attached materials, followed by specific gravity separation, and then magnetic separation can be performed again to separate the magnetically attached materials.

[0030] Furthermore, after sieving, magnetic separation, and specific gravity separation, crushing can be performed again as needed. What is important in this disclosure is that, in the crushing before separation, the size of the crushed material is standardized to a certain range to reduce the inclusion of copper foil in ferrous metals and aluminum ingots, and to separate the copper ingots individually. Therefore, after separation with reduced inclusion, crushing or sieving can be performed again as needed.

[0031] While it is conceivable to separate copper foil embedded in iron-based metals or aluminum ingots by color sorting, as described in Patent Documents 1 and 3, this is extremely difficult because the copper foil is crushed into layers within the iron-based metals or aluminum ingots during the crushing process. In this embodiment, the crushing process is modified to suppress the embedding of copper foil, so color sorting is usually unnecessary.

[0032] [Recovered items] Through the above process, it is possible to separate ferrous metals, copper ingots, aluminum ingots, copper foil and aluminum foil that make up the current collector, and electrode material powders such as lithium, nickel, cobalt, manganese, graphite, silicon, titanium, niobium, and silicon. It is possible that electrode materials such as active materials may be changed in the future to improve the performance of lithium-ion secondary batteries. In this disclosure, it is sufficient that the recovered valuable material contains at least copper. [Examples]

[0033] The following explanation is based on examples. However, these examples are merely illustrative and do not limit the invention in any way. That is, the present invention is limited only by the claims and encompasses various modifications other than those included in the examples.

[0034] (Example 1) For lithium-ion secondary batteries, valuable materials were recovered according to the flow shown in Figure 3. First, a lithium-ion secondary battery, specifically an automotive battery module, was subjected to a 4-hour heat treatment using a hot air heating furnace capable of generating hot air at 400°C to 600°C. Afterward, the heat-treated battery module was subjected to primary crushing using a four-axis shear crushing device to reduce the size of the crushed material to 40 mm or less. Next, the crushed material obtained from the primary crushing was then processed. The material was subjected to secondary crushing using a four-shaft shear crusher to reduce it to a size of 15 mm or less. Next, the resulting crushed material was separated from the sieved product (polar material powder) using a primary sieve with a mesh size of 1.0 mm.

[0035] For the sieved products exceeding 1.0 mm obtained by the primary sieving process, ferrous metals, which are crushed exterior material and magnetically attached components, were removed using a suspended magnetic separation system with a magnetic flux density of 0.03 Tesla. For the non-magnetically attached materials, air separation was used to separate them into heavy and light products.

[0036] The heavy products obtained from the previous wind separation were subjected to removal of ferrous metals, which are magnetic components, using a drum-type magnetic separation system with a magnetic flux density of 0.15 Tesla. Meanwhile, the non-magnetic materials were separated into copper lumps and aluminum lumps using an air table.

[0037] The light products obtained from the previous wind separation were subjected to tertiary crushing using a single-shaft shear crusher. The resulting crushed material was separated from the subsieved products (electrode material powder) using a secondary sieve with a mesh size of 1.0 mm. The sieved products larger than 1.0 mm were separated by specific gravity to remove the heavy products, namely copper lumps and aluminum lumps. The resulting light products were then subjected to magnetic separation using a drum-type magnetic separation system with a magnetic flux density of 0.15 Tesla to remove the ferrous metal components that were magnetized. For the non-magnetic materials, copper foil and aluminum foil were separated using an ultra-high magnetic separation system with a magnetic flux density of 1 Tesla or more.

[0038] (Example 2) Except for limiting the size of the crushed material by primary crushing to 25 mm or less, valuable materials were recovered from lithium-ion secondary batteries under the same conditions as in Example 1.

[0039] (Comparative Example 1) Except for not performing secondary crushing, valuable materials were recovered from the lithium-ion secondary battery under the same conditions as in Example 1.

[0040] Table 1 shows the recovery rates and grades of copper in the form of copper ingots and copper foil, relative to the amount of copper in battery modules (lithium-ion secondary batteries) placed in a heating furnace. The various recovery rates and grades were calculated using the following formulas. Recovery rate of copper lumps (%) = Weight of recovered copper lumps / Weight of copper in secondary batteries × 100 Copper foil recovery rate (%) = Weight of recovered copper foil / Weight of copper in secondary battery × 100 Total copper recovery rate (%) = (Weight of recovered copper lumps + Weight of copper foil) / Weight of copper in secondary batteries × 100 Grade of copper ingots (%) = Weight of copper ingots / (Weight of air table heavy product) × 100 Copper foil quality (%) = Weight of copper foil / (Weight of non-magnetic material separated by magnetic force (ultra-high)) × 100

[0041] [Table 1]

[0042] In Example 1, the recovery rate for copper ingots was 34% and the quality was 91%, while the recovery rate for copper foil was 28% and the quality was 87%. The total recovery rate of copper from both copper ingots and copper foil was 62%. In Example 2, the recovery rate as copper ingots was 35%, and the quality was 84%, as copper foil. The recovery rate was 34%, the grade was 94%, and the recovery rate for copper, including both copper ingots and copper foil, was 69%. In Comparative Example 1, the recovery rate for copper ingots was 0%, the recovery rate for copper foil was 20%, the quality was 80%, and the total recovery rate of copper from both copper ingots and copper foil was 20%. From the above results, it can be seen that the copper recovery rate in Examples 1 and 2 was improved by approximately 40-50% compared to Comparative Example 1. As described above, by adjusting the particle size so that the size of the crushed material is 20 mm or less and crushing it, the separation of individual sealing bolts and conductive busbars is promoted, the recovery rate of copper lumps is improved, and the copper foil is less likely to become embedded in the exterior material, resulting in a significant improvement in the recovery rate of copper foil. [Industrial applicability]

[0043] According to the present invention, a method for recovering valuable materials from lithium-ion secondary batteries has the excellent effect of improving the copper recovery rate and reducing the copper content in iron-based metals, thereby improving their quality. It can be suitably used as a method for recovering valuable materials from automotive lithium-ion secondary batteries, a market expected to expand in the future.

Claims

1. A method for recovering valuable materials including copper from a lithium-ion secondary battery using ferrous metal and / or aluminum as the outer casing, wherein the lithium-ion secondary battery is crushed together with the outer casing using a shear crusher, a screen with an opening is installed below the crushing blade of the crusher, the crushed material is circulated until it is small enough to pass through the opening, the crushed material is crushed so that the maximum size of the crushed material is 20 mm or less, and then the following steps (1) to (3) are performed in any order or number of times. (1) A process of separating the sieved product from the unsieved product by sieving. (2) A process of separating magnetic and non-magnetic materials by magnetic sorting. (3) A process of separating heavy products from light products by specific gravity sorting.

2. The method for recovering valuable materials from lithium-ion secondary batteries according to claim 1, characterized in that a shear-type crusher capable of adjusting particle size is used in the crushing step.

3. The method for recovering valuable materials from a lithium-ion secondary battery according to claim 1, characterized in that a three-axis or four-axis shear crusher is used in the crushing step.

4. The method for recovering valuable materials from a lithium-ion secondary battery according to claim 1, characterized in that the crushing step includes two or more consecutive crushing steps.

5. A method for recovering valuable materials from a lithium-ion secondary battery according to claim 1, characterized in that specific gravity separation is performed using wind separation or an air table.

6. A method for recovering valuable materials from a lithium-ion secondary battery according to claim 1, comprising a heating step of heating the lithium-ion secondary battery before crushing.

7. A method for recovering valuable materials from a lithium-ion secondary battery according to claim 1, comprising the steps of crushing light products separated by specific gravity separation, and sieving the crushed material obtained by the crushing to separate electrode material powder, which is a sieved product.

8. A method for recovering valuable materials from a lithium-ion secondary battery according to claim 1, comprising the step of separating iron-based metals that are magnetically attached to the sieved products separated by sieving.

9. A method for recovering valuable materials from a lithium-ion secondary battery according to claim 8, comprising the steps of separating heavy products and light products by specific gravity separation of the non-magnetic material separated by magnetic separation, and separating copper lumps and aluminum lumps by magnetic separation and / or specific gravity separation of the heavy products.

10. A method for recovering valuable materials from a lithium-ion secondary battery according to claim 9, comprising the steps of crushing the light products separated by the gravity separation, and sieving the crushed material obtained by the crushing to separate the electrode material powder, which is a sieved product.

11. A method for recovering valuable materials from a lithium-ion secondary battery according to claim 10, comprising the steps of separating the sieved product separated by the sieving by specific gravity into heavy products and light products, and separating the light product separated by specific gravity into non-magnetic copper foil and magnetic aluminum foil.

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