Method for recycling waste resulting from the manufacture of lithium-ion batteries

Abstract

To provide a method for recycling waste that arises from the manufacture of electrodes for lithium-ion accumulators.SOLUTION: The method comprises separately collecting wastes for recycling, the wastes being pieces 2 of material strips generated during the manufacture of the material strips, material strips including foil made of a metallic material 4 coated with an electrode active material 6. Each piece 2 includes a foil piece to which the electrode active material 6 is applied. The pieces 2 are subjected to a thermal treatment to detach the electrode active material 6 from the foil sections in order to recycle the pieces.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method for recycling waste generated during the manufacture of electrodes for lithium-ion batteries. [Background technology]

[0002] Lithium-ion batteries are now widely used. They are used, inter alia, in motor vehicles, for example as so-called traction batteries, i.e. as energy storage devices for supplying electric drive machines.

[0003] Depending on the application, a lithium-ion battery may comprise one or more battery cells, each of which typically comprises a positive electrode, a negative electrode, a separator, and an electrolyte as its basic components. Various embodiments are known regarding the exact structure.

[0004] For example, the manufacture of lithium ion batteries is outlined in Non-Patent Document 1. [Prior art documents] [Non-patent literature]

[0005] [Non-Patent Document 1] Heimes, Heiner Hans; Kampker, Achim; Lienemann, Christoph; Locke, Marc; Offermanns, Christian; Michaelis, Sarah; Rahimzei, Ehsan (2018): Heimes, Heiner Hans; Kampker, Achim; Lienemann, Christoph; Locke, Marc; Summary of the Invention [Problem to be solved by the invention]

[0006] The object of the present invention is to provide a method for recycling waste products resulting from the production of lithium-ion batteries. [Means for solving the problem]

[0007] This problem is solved by a device with the features of patent claim 1. Advantageous embodiments with practical developments of the invention are set out in the dependent claims.

[0008] In this case, the method according to the invention serves to recycle waste products that arise during the manufacture of electrodes for lithium-ion batteries, and is therefore a recycling method.

[0009] In this regard, methods for producing electrodes for lithium-ion batteries, i.e., manufacturing methods, are basically known, in which material strips are first produced and then electrodes are cut from these material strips by a separation process, also known as cutting. Such manufacturing methods are outlined in [1].

[0010] During the production of electrodes, waste material is also generated, including fragments of material strips, i.e., waste pieces. The corresponding material strips are strip materials having foils made of metal material, such as copper or aluminum foil. In this case, the foils are coated on at least one side with an active material, i.e., the so-called electrode active material. Furthermore, each of the aforementioned waste pieces has a foil fragment to which the electrode active material is applied.

[0011] These waste pieces, or short pieces, are collected separately during the recycling process, i.e., the pieces are collected separately from other waste so that the waste is, so to speak, separated as a single waste. Thus, for the purposes of this application, waste is formed by the pieces, and possibly by foil pieces that do not contain electrode active material and / or electrode active material that do not contain foil pieces.

[0012] The waste collected in this way is finally subjected to a heat treatment during the recycling process, whereby the electrode active material is separated from the foil pieces in the waste pieces.

[0013] The aforementioned fragments, i.e., waste pieces generated as waste during the manufacture of electrodes, can typically be divided into three types: strips, sections, and swarf. Depending on the application, recycling methods apply to only one type of waste piece, two types of waste piece, in particular strips and sections, or all three types of waste piece.

[0014] If the recycling method is applied to at least two types of waste pieces, further collection of the fragments and heat treatment of each type is carried out according to at least one embodiment of the method, in which case the variant in which waste pieces of the swarf type are collected and heat treated separately from the other waste pieces is particularly preferred.

[0015] Strip-type pieces are whole sections of material strip, i.e. complete material strips that have been removed, for example because the coating of electrode active material does not comply with quality requirements. Such pieces typically have a length of 100 m or more, in particular 1000 m or more.

[0016] Sectioned pieces are sections of the material strip that have been cut from the material strip, for example, because the electrode active material coating in this section does not meet quality requirements or because the foil has torn. Sectioned pieces also typically include sections of the material strip called starting material or starting material. Such pieces typically have a length of 5 m or more, especially 20 m or more.

[0017] A chip-type fragment is a piece of material strap that remains as chip from one of the aforementioned separation processes, i.e., cutting.

[0018] Regardless of what type of waste pieces are utilized using the recycling method, or what type of waste pieces are utilized using the recycling method, a heat treatment is performed during the recycling method, which heat treatment causes the electrode active material to be stripped from the foil pieces in the waste pieces, as previously described.

[0019] In this case, the recycling method is preferably applied to waste pieces in which the foil pieces and the metal materials of the electrode active material have different thermal expansion properties, in particular different linear expansion coefficients, and in this case the different thermal expansion properties, in particular different linear expansion coefficients, are utilized to peel the electrode active material from the foil pieces.

[0020] More preferably, the recycling method is applied to waste pieces in which the metal material of the foil pieces has a linear expansion coefficient α1 and the electrode active material has a linear expansion coefficient α2, and at least at room temperature, α1=f*α2 or α2=f*α1, where the coefficient f is 1.2 or more, in particular 1.5 or more.

[0021] In some cases, the waste pieces are further subjected to a heat treatment, starting from room temperature and heating to a heat treatment temperature T. In this case, waste heat generated during the production of the electrodes, i.e. during the manufacturing method, is preferably used for heating. Regardless of this, the heat treatment temperature T is typically in the range of 100°C to 300°C, in particular in the range of 200°C to 300°C.

[0022] Furthermore, in some cases, the heat treatment is carried out under special ambient conditions, and in these cases it is useful that the waste pieces are not exposed to the ambient air. Instead, the heat treatment is carried out, for example, under a protective gas atmosphere or under vacuum conditions.

[0023] Depending on the application, the waste pieces are further heated starting from room temperature to a heat treatment temperature TW and maintained at the heat treatment temperature TW for a time t, for example, 2 minutes or more, 5 minutes or more, 10 minutes or more, or 20 minutes or more.

[0024] According to at least one embodiment variant, heating to the heat treatment temperature TW is carried out at a heating rate of 1° C. / s or less or 0.5° C. / s or less.

[0025] According to an alternative embodiment, the heat treatment is carried out by applying liquid nitrogen to the waste pieces at room temperature.

[0026] It is further advantageous if, during the recycling process, the electrode active material is separated from the foil portion using at least one gas stream, for example an air jet.

[0027] Also useful are recycling embodiments in which the electrode active material is separated from the foil portion by brushing or removing the foil portion.

[0028] In particular, when the recycling method is applied to strip-type and / or section-type waste pieces, it is also advantageous if the heat treatment of each waste piece is carried out in a roll-to-roll process and then the corresponding waste piece is pre-clamped for the roll-to-roll process.

[0029] In an advantageous further development, a foil, i.e. an uncoated foil, is thus recovered from the metal material, which foil is preferably then re-coated with electrode active material and then reused to produce an electrode.

[0030] When the recycling method is applied to waste pieces of the swarf type, a variant is useful in which the waste pieces are crushed, in particular shredded, before the heat treatment. In this case too, it is further advantageous if, in the course of further implementation of the recycling method, the electrode active material is separated from the foil portions using at least one gas stream, for example an air jet.

[0031] Regardless, in at least some applications, the stripped and separated electrode active material is ground in a further step of the recycling process. Typically, the electrode active material is mixed with a solvent and ground in the solvent.

[0032] In an advantageous further development, the pulverized electrode active material is used in a further step of the recycling method as a component for a suspension of electrode active material, which is then used again to produce electrodes.

[0033] The foil pieces that have been removed from the electrode active material by heat treatment of the waste pieces are also conveniently reused. In this case, strip-type foil pieces are preferably fed back into the coating process. This also preferably corresponds to section-type foil pieces. In this case, these section-type foil pieces are typically joined together into larger pieces in an intermediate treatment process, for example by so-called splicing techniques. Scrap-type foil pieces and other types of foil pieces that cannot be directly reused are typically fed to metal recycling.

[0034] Further advantages, features and details of the invention will become apparent from the claims, the following description of preferred embodiments and the schematic drawings. [Brief explanation of the drawings]

[0035] [Figure 1] FIG. 1 shows a side view of a first station for recycling waste generated during the manufacture of electrodes for lithium-ion batteries. [Figure 2] FIG. 1 shows a side view of a second station for recycling waste generated during the manufacture of electrodes for lithium-ion batteries. DETAILED DESCRIPTION OF THE INVENTION

[0036] Corresponding parts are given the same reference numerals in all figures.

[0037] The method described below is used by way of example to recycle waste generated during the manufacture of electrodes for lithium-ion batteries, which waste comprises fragments 2 of material strips, i.e. waste pieces.

[0038] The corresponding material strip is a strip material comprising a foil of a metal material 4, for example a copper or aluminum foil, which is coated on at least one side with an active material, i.e., a so-called electrode active material 6. The waste pieces or fragments 2 then comprise pieces of foil to which the electrode active material 6 has been applied.

[0039] Here, the fragments are collected separately during the process, i.e., fragments 2 are collected separately from other waste materials, so that the waste materials are classified as a single waste material. The collected waste materials are then subjected to a heat treatment, whereby the electrode active material 6 is peeled off from the metal material 4 in the fragments 2.

[0040] In this example, three types of fragments 2 can be distinguished: strip, section, and chip. The strip and section fragments 2 are collected and fed to a first station 8 for heat treatment, shown in Figure 1. The chip fragments 2 are collected separately from the remaining fragments 2 and fed to a second station 10 for heat treatment, shown generally in Figure 2.

[0041] Strip-type pieces 2 are whole pieces of material strip, i.e. complete material strips that have been removed, for example because the coating of electrode active material 6 does not comply with quality requirements. Such pieces 2 typically have a length of 100 m or more, in particular 1000 m or more.

[0042] The sectioned pieces 2 are sections of the material strip that have been cut from the material strip, for example, because the coating of the electrode active material 6 in this section does not meet quality requirements or because the foil has torn. Sectioned pieces also typically include sections of the material strip called starting material or starting material. Such pieces 2 typically have a length of 5 m or more, in particular 20 m or more.

[0043] The chip-type fragments 2 are fragments of the material strap that remain as chips.

[0044] As mentioned above, all pieces 2 are heat-treated during the process. In this case, the heat treatment is used to peel the electrode active material 6 from the metal material 4. Here, the different linear expansion coefficients of the electrode active material 6 and the metal material 4 are utilized.

[0045] In an embodiment, the heat treatment of the pieces 2 is carried out by starting from room temperature and heating them to a heat treatment temperature TW. For this purpose, each of the stations 8, 10 has a heating unit 12. In this case, the heat treatment temperature TW is typically in the range of 100°C to 300°C, in particular in the range of 200°C to 300°C.

[0046] Furthermore, after peeling, the electrode active material 6 and the metal material 4 are separated. For this purpose, in the case of the first station 8, a gas flow, for example an air jet, is used. The first station 8 therefore has a blower 13, through which the electrode active material 6 is transported into a collection container 14.

[0047] In contrast, in the case of the second station 10, a vibration unit 16, which is a combination of a vibrating screen and a conveyor belt, is used for separation. In this case, the electrode active material 6 then arrives in a first collection container 18, and the metal material 4 arrives in a second collection container 20.

[0048] Furthermore, the heat treatment of the strip and section pieces 2 is carried out in a roll-to-roll process, for which each corresponding piece is pre-clamped, as shown in Figure 1. In this way, a foil made of metal material 4, i.e., an uncoated foil, is recovered, which can be reused to produce an electrode, preferably by being coated again with electrode active material 6.

[0049] The heat treatment of the chip-type pieces 2 is not carried out in a roll-to-roll process. Instead, the pieces 2 are crushed before the heat treatment. For this purpose, the second station 10 has a shredder 18. The waste material crushed in the shredder 18 then falls onto a conveyor belt 20, where it is heat treated using the heating unit 12 while still on the conveyor belt 20, and then falls into the vibrating unit 16. The present application relates to the invention described in the claims, but also includes the following as other aspects. 1. A method for recycling waste generated during the manufacture of electrodes for lithium ion batteries, comprising: The method comprises: During production, strips of material are produced, Each material strip comprises a foil of metal material (4) coated with an electrode active material (6); During production, fragments of material strips (2) are generated as waste and are separated and collected for recycling, Each piece (2) comprises a piece of foil coated with electrode active material (6); and For recycling, the pieces (2) are subjected to a heat treatment to peel off the electrode active material (6) from the foil portion. A method characterized by: 2. 2. The method according to claim 1, wherein the metal material (4) and the electrode material (6) have different thermal expansion properties, and the heat treatment is carried out so that the different thermal expansion properties are used to exfoliate. 3. 3. The method according to claim 1 or 2, wherein the fragment (2) is heated from room temperature to a heat treatment temperature during the heat treatment. 4. 3. The method according to claim 1 or 2, wherein liquid nitrogen is applied to the pieces (2) for heat treatment at room temperature. 5. 5. The method according to any one of the above 1 to 4, wherein the electrode active material (6) is separated from the foil pieces using a gas stream for recycling. 6. 6. The method according to any one of 1 to 5 above, wherein the electrode active material (6) is brushed off from the foil pieces for recycling. 7. 7. The method according to any one of 1 to 6 above, wherein the heat treatment is carried out in a roll-to-roll process in which the pieces (2) are clamped. 8. 8. The method according to any one of the above 1 to 7, wherein the peeled electrode active material (6) is pulverized for recycling. 9. 8. The method according to any one of the above 1 to 7, wherein the exfoliated electrode active material (6) is ground in a solvent for recycling. 10. 10. The method according to claim 8 or 9, wherein the pulverized electrode active material (6) is used as a component of a suspension of electrode active material for recycling. [Explanation of symbols]

[0050] 2 Fragments 4 Metal materials 6 Electrode active material 8. First Station 10 Second Station 12 Heating unit 13 Blower 14 Collection containers 16 vibration unit 18 First Collection Container 20 Second collection container 22 Shredder 24 Conveyor Belt

Claims

1. A method for recycling waste generated during the manufacture of electrodes for lithium ion batteries, comprising: During production, strips of material are produced, Each material strip comprises a foil of metal material (4) coated with an electrode active material (6); During production, pieces of material strip (2) are generated as waste and are collected separately for recycling, Each piece (2) comprises a piece of foil coated with an electrode active material (6); and For recycling, the pieces (2) are subjected to a heat treatment to peel off the electrode active material (6) from the foil portion. In the method, The fragments (2) are strip-type fragments (2) having a length of 100 m or more or 1000 m or more, or section-type fragments (2) having a length of 5 m or more or 20 m or more; The heat treatment is carried out in a roll-to-roll process in which the pieces (2) are clamped, The heating rate to the heat treatment temperature (TW) is 1°C / s or less, or 0.5°C / s or less; A method characterized by:

2. 2. The method of claim 1, wherein the metal material (4) and the electrode material (6) have different thermal expansion properties and the heat treatment is performed such that the different thermal expansion properties are used to delaminate.

3. 3. The method according to claim 1 or 2, wherein the pieces (2) are heated from room temperature to the heat treatment temperature during the heat treatment.

4. 3. The method according to claim 1 or 2, wherein liquid nitrogen is applied to the pieces (2) for heat treatment at room temperature.

5. 3. The method according to claim 1 or 2, wherein the electrode active material (6) is separated from the foil pieces using a gas stream for recycling.

6. 3. The method according to claim 1 or 2, wherein the electrode active material (6) is brushed off from the foil pieces for recycling.

7. 2. The method according to claim 1, wherein the exfoliated electrode active material (6) is pulverized for recycling.

8. 2. The method according to claim 1, wherein the exfoliated electrode active material (6) is ground in a solvent for recycling.

9. 9. The method according to claim 7 or 8, wherein the pulverized electrode active material (6) is used as a component of a suspension of electrode active material for recycling.

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