Battery disposal method

Abstract

This invention provides a battery processing method that can separate the active material layer from the electrode substrate while reducing environmental impact. [Solution] The battery processing method includes the steps of: discharging a secondary battery to reduce its voltage to a predetermined value or less; crushing the secondary battery to obtain a pulverized material containing an active material, a binder, an electrolyte, and a metal foil; heating the pulverized material at a first temperature under reduced pressure to evaporate the electrolyte; and further crushing the pulverized material after the step of evaporating the electrolyte to separate the active material from the metal foil.

Description

[Technical Field]

[0001] This disclosure relates to a battery processing method for peeling off an active material layer from an electrode substrate. [Background technology]

[0002] Rechargeable batteries, which house an electrolyte and battery components inside a casing, are widely used as power sources for electronic devices such as video cameras, laptops, and mobile phones, as well as electric and hybrid vehicles. Therefore, recovering valuable metals and other recycled materials from used rechargeable batteries or batteries discarded before use is considered important from the perspective of efficient resource utilization.

[0003] Thus, as a battery processing method for recovering recycled materials such as valuable metals, Japanese Patent Publication No. 2012-195073 (Patent Document 1) discloses a method in which a secondary battery is crushed to remove the separator, the crushed material containing the electrode substrate and active material layer is heated in the range of 400°C to 550°C, and the heated crushed material is further crushed. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2012-195073 [Overview of the Initiative] [Problems that the invention aims to solve]

[0005] However, the battery processing method disclosed in Patent Document 1 consumes a large amount of thermal energy because it heats to 400°C to 550°C to decompose the binder contained in the active material layer. In addition, a large amount of binder is decomposed, and carbon dioxide is easily emitted. As a result, the burden on the environment becomes large.

[0006] This disclosure has been made in view of the above-mentioned problems, and the purpose of this disclosure is to provide a battery processing method that can peel off the active material layer from the electrode substrate while reducing the environmental burden. [Means for solving the problem]

[0007] The battery processing method of this disclosure comprises the steps of: preparing a pulverized material comprising an electrode substrate and an active material layer containing a resin component and provided on the electrode substrate; heating the pulverized material at a temperature above the decomposition start temperature of the resin component and below the decomposition peak temperature of the resin component; and grinding the pulverized material. In the heating step, the resin component is softened, and in the grinding step, the active material layer is peeled off the electrode substrate by grinding the pulverized material in which the resin component has been softened.

[0008] With the above configuration, the pulverized material is heated at a temperature above the decomposition start temperature of the resin component and below the decomposition peak temperature of the resin component. This allows the resin component to be softened at a low temperature while suppressing the consumption of thermal energy. Furthermore, since the decomposition of the resin component is suppressed, the amount of carbon dioxide emitted can also be reduced. In addition, by pulverizing the pulverized material in which the resin component has been softened, the active material layer can be peeled off from the electrode substrate. In this way, the active material layer can be peeled off from the electrode substrate while reducing the environmental burden.

[0009] In the battery processing method described herein, when the fragments of the electrode substrate from which the active material layer has been peeled off are spread out in a planar manner, the particle size of the fragments is 400 mm. 2 Above 1000mm 2 The following applies, and the peeling rate of the active material layer from the electrode substrate may be 80% or more.

[0010] With the above configuration, even if the fragments of the electrode substrate from which the active material layer has been peeled off are relatively large, the active material layer can be efficiently peeled off from the electrode substrate.

[0011] In the battery processing method described herein, the heating step and the pulverizing step may be performed simultaneously.

[0012] With the above configuration, heating and pulverization are performed simultaneously, eliminating the need to heat the pulverized material and then transport the heated pulverized material to the pulverization process, thus simplifying the processing steps.

[0013] In the battery processing method described above, the heating step and the pulverizing step may be performed repeatedly.

[0014] With the above configuration, the resin components contained in the active material layer attached to the crushed electrode substrate fragments can be further softened, allowing the active material layer to be further peeled off from the electrode substrate fragments.

[0015] In the battery processing method of the present disclosure described above, it is preferable to prepare a pulverized material containing a separator in the preparation step, and it is preferable that the separator, the electrode substrate, and the active material layer are separated in the pulverization step.

[0016] According to the above configuration, the pulverized material can be heated at a low temperature, preventing the separator from welding to the active material layer. Even if the pulverized material contains a separator, the active material layer can be separated from the electrode plate. Therefore, the step of removing the separator beforehand is unnecessary, and the processing steps can be simplified. [Effects of the Invention]

[0017] According to this disclosure, it is possible to provide a battery processing method that can separate the active material layer from the electrode substrate while reducing the environmental impact. [Brief explanation of the drawing]

[0018] [Figure 1] This is a flowchart showing the steps of the battery processing method according to Embodiment 1. [Figure 2]It is a schematic diagram showing the step of heating the pulverized material according to Embodiment 1. [Figure 3] It is a schematic diagram showing the step of pulverizing according to Embodiment 1. [Figure 4] It is a schematic diagram in the case where the step of heating the pulverized material and the step of pulverizing are simultaneously carried out in the battery treatment method according to the modified example. [Figure 5] It is a flowchart showing the steps of the battery treatment method according to Embodiment 2. [Figure 6] It is a diagram showing the conditions and results of an experiment conducted using the battery treatment method according to the example and the battery treatment method in the comparative example. [Figure 7] It is a diagram plotting the relationship between the particle size and the peeling rate in each of Comparative Examples 1-8 and Examples 1-2 shown in FIG. 6.

MODE FOR CARRYING OUT THE INVENTION

[0019] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. In the embodiments shown below, the same or common parts are denoted by the same reference numerals in the drawings, and the description thereof will not be repeated.

[0020] (Embodiment 1) FIG. 1 is a flowchart showing the steps of the battery treatment method according to Embodiment 1. Referring to FIG. 1, the battery treatment method according to Embodiment 1 will be described.

[0021] The battery treatment method according to Embodiment 1 is a method used to recover an active material layer containing valuable metals and the like.

[0022] The battery targeted by the battery treatment method is, for example, a secondary battery such as a lithium ion battery. The secondary battery includes a battery element, an electrolytic solution, and an exterior case that houses the battery element and the electrolytic solution.

[0023] The battery element is configured by laminating a positive electrode and a negative electrode with a separator interposed therebetween.

[0024] The positive electrode includes a sheet-like member as an electrode substrate and a positive electrode active material layer. The sheet-like member is made of a metal foil, such as aluminum foil. The positive electrode active material layer may be formed on both sides of the sheet-like member. The positive electrode active material layer includes a positive electrode active material and a binder as a resin component.

[0025] The positive electrode active material is typically a lithium (Li)-containing metal oxide. Specifically, positive electrode active materials include, for example, lithium cobalt oxide-based materials, lithium manganese oxide-based materials, and lithium nickel cobalt manganese oxide-based materials.

[0026] The binder may be, for example, carboxymethylcellulose (CMC), styrene-butadiene rubber (SBR), polyacrylic acid (PAA), etc.

[0027] The negative electrode includes a sheet-like member and a negative electrode active material layer. The sheet-like member is made of, for example, a metal foil such as copper foil. The negative electrode active material layer may be formed on both sides of the sheet-like member.

[0028] The negative electrode active material layer comprises a negative electrode active material and a binder. The negative electrode active material may be a carbon-based negative electrode active material such as graphite, easily graphitizable carbon, or poorly graphitizable carbon, or it may be an alloy-based negative electrode active material containing silicon (Si), tin (Sn), etc.

[0029] The binder may be, as described above, for example, carboxymethylcellulose (CMC), styrene-butadiene rubber (SBR), polyacrylic acid (PAA), etc.

[0030] A separator is an electrically insulating porous film. The separator is made from a resin such as polyethylene (PE) and polypropylene (PP). A separator may be made from a porous PE film alone, or from a combination of a porous PE film and a porous PP film. For example, a separator may be formed by laminating a porous PP film, a porous PE film, and a porous PP film in that order. For example, a separator may be formed by laminating a porous PE membrane and a porous PP membrane.

[0031] The electrolyte used is, for example, a lithium salt such as lithium hexafluoride phosphate (LiPF6) dissolved in a mixed solvent such as ethylene carbonate (EC)-dimethyl carbonate (DMC), but other compositions may also be used. The outer casing is made of a metal such as aluminum.

[0032] As shown in Figure 1, in carrying out the battery processing method according to Embodiment 1, first, in step (S10), the crushed material is prepared.

[0033] In order to carry out process (S10), first, in process (S11), the secondary battery is deactivated. Specifically, discharge or other processes are performed to reduce the voltage of the secondary battery to below a predetermined level so that it ceases to function as a battery.

[0034] Next, in step (S12), the secondary battery is crushed. For example, the secondary battery may be crushed using a single-shaft shear crusher or a twin-shaft shear crusher, or it may be crushed using a hammer mill or other crushing machine.

[0035] Next, in step (S13), the electrolyte is recovered. Specifically, the pulverized material obtained in step (S12) is heated under reduced pressure to distill the electrolyte. At this time, solvents with relatively low boiling points of about 90°C to 110°C, such as DMC and EMC (ethyl methyl carbonate), contained in the electrolyte are easily recovered, while solvents with relatively high boiling points of about 240°C, such as EC, contained in the electrolyte may remain without being recovered.

[0036] Through the above-described process, a pulverized material 1 (see Figure 2) is prepared, which includes the sheet-like member and an active material layer provided on the sheet-like member and containing a binder. More specifically, a pulverized material 1 containing a positive electrode active material and a positive electrode sheet member is prepared. The pulverized material 1 may also contain a separator. In Embodiment 1, the pulverized material 1 prepared is a primary pulverized material obtained by pulverizing a secondary battery.

[0037] Figure 2 is a schematic diagram showing the process of heating the pulverized material according to Embodiment 1. As shown in Figures 1 and 2, in step (S20), the pulverized material 1 is subsequently heated at a temperature above the binder decomposition start temperature and below the binder decomposition peak temperature. The binder decomposition start temperature is, for example, about 120°C, and the binder decomposition peak temperature is, for example, about 400°C.

[0038] In step (S20), the temperature range for heating the pulverized material is preferably around 120°C to 180°C in order to soften the binder with lower thermal energy. Furthermore, if the pulverized material contains a separator, the temperature is preferably around 120°C to 160°C, and more preferably around 120°C to 140°C, in order to suppress the melting of the separator. Moreover, if the pulverized material 1 contains a separator, it is even more preferable to heat the pulverized material 1 at a temperature above the decomposition start temperature of the binder and below the melting point of the separator.

[0039] When heating the pulverized material 1, for example, the pulverized material 1 is placed in a heating chamber 10 and heated by a heat source 20 such as a heater. Heating of the pulverized material 1 is not limited to heating by a heater, and any appropriate heating method such as convection heating, far-infrared heating, or steam heating can be used. The heating time is, for example, about one hour.

[0040] By heating the pulverized material 1 within the temperature range described above, the binder softens, making it easier to separate the active material layer from the sheet-like member.

[0041] Figure 3 is a schematic diagram showing the crushing process according to Embodiment 1. As shown in Figures 1 and 3, in the subsequent step (S30), the heated crushed material 1 is crushed. Specifically, for example, the heated crushed material 1 is placed in the crushing chamber 30 and crushed using the crusher 40. The crusher 40 can be any suitable crusher such as a hammer crusher. When using a hammer crusher, the friction applied to the crushed material 1 can be increased.

[0042] In step (S30), the pulverized material 1 is pulverized while the binder is softened, so the impact applied to the pulverized material 1 allows the active material layer to be peeled off from the sheet-like member.

[0043] In the above example, the case in which process (S30) is performed after process (S20) was illustrated, but as shown in the modified example, processes (S20) and (S30) may be performed simultaneously. In this case, since the heating and grinding of the pulverized material 1 are performed simultaneously, it becomes unnecessary to transport the heated pulverized material 1 to the grinding process after heating, thus simplifying the processing steps.

[0044] Figure 4 is a schematic diagram of a modified battery processing method in which the heating and grinding steps of the pulverized material are carried out simultaneously. When the heating and grinding steps of the pulverized material are carried out simultaneously, as shown in Figure 4, a heat source 20 such as a heater is installed in the grinding chamber 30, and the pulverized material 1 is heated while the pulverized material 1 is ground by the grinder 40. As described above, the heating of the pulverized material 1 is not limited to heating by a heater, but any appropriate heating method such as convection heating, far-infrared heating, or steam heating can be used.

[0045] Next, in step (S35), it is confirmed whether steps (S20) and (S30) have been performed a predetermined number of times. The predetermined number of times may be one or two or more.

[0046] If steps (S20) and (S30) above are performed a predetermined number of times (step (S35): YES), then step (S40) is performed.

[0047] On the other hand, if steps (S20) and (S30) have not been performed the predetermined number of times (step (S35): NO), steps (S20) and (S30) are repeated until the predetermined number of times is reached.

[0048] When steps (S20) and (S30) are repeated in this manner, the resin components contained in the active material layer attached to the crushed electrode substrate fragments are further softened, and by crushing the fragments, the active material layer can be further peeled off from the electrode substrate fragments.

[0049] Next, in step (S40), the crushed material 1 is separated. Specifically, a sieve or the like is used to separate the sheet-like member from the active material layer. At this time, in addition to the sheet-like member and the active material layer, the separator and the components that make up the outer case are also separated. The crushed material 1 separated in Embodiment 1 is the secondary crushed material that is produced when the primary crushed material is crushed, and in step (S40), the secondary crushed material is separated.

[0050] As described above, in the battery processing method according to Embodiment 1, the pulverized material is heated at a temperature above the decomposition start temperature of the resin component and below the decomposition peak temperature of the resin component. Therefore, the consumption of thermal energy is suppressed, and the resin component contained in the active material layer can be softened at a low temperature. Furthermore, since the decomposition of the resin component is suppressed, the amount of carbon dioxide emitted can also be reduced. In addition, by pulverizing the pulverized material in which the resin component has been softened, the active material layer can be peeled off from the electrode substrate. In this way, the active material layer can be peeled off from the electrode substrate while reducing the environmental burden.

[0051] Furthermore, when fragments of a sheet-like member (a sheet-like member for a positive electrode) from which the active material layer (more specifically the positive electrode active material layer) has been peeled off are spread out in a planar manner, the particle size of the fragments is 400 mm. 2 Above 1000mm 2 The following conditions apply, and it is preferable that the peeling rate of the active material layer from the sheet-like member is 80% or higher.

[0052] The particle size of the above fragments can be calculated as follows. First, in process (S40), fragments (particles) of multiple sheet-like members from which the active material layer has peeled off are sampled, and these multiple sheet-like member fragments are unfolded in a planar manner. Then, the size of the unfolded multiple sheet-like member fragments is calculated using the image analysis software WinROOF (manufactured by Mitani Corporation).

[0053] Particle size (mm) 2 ) can be obtained, for example, by calculating the sum of values ​​obtained by dividing the area of ​​each particle (projected area) by the total area of ​​multiple particles (total projected area). More specifically, it can be calculated by the following equation (1). TIFF2026074322000002.tif17147

[0054] Furthermore, the peeling rate can be calculated by using the image analysis software described above to determine the total area of ​​the active material layer remaining on the fragments (particles) of the multiple sheet-like members, and then using the following formula (2).

[0055] Peeling rate (%) = (Total area of ​​multiple (n) particles - Total area of ​​the active material layer remaining on multiple (n) particles) / Total area of ​​multiple particles × 100 ... (Equation 2) (Embodiment 2) Figure 5 is a flowchart showing the steps of the battery processing method according to Embodiment 2. The battery processing method according to Embodiment 2 will be described with reference to Figure 5.

[0056] As shown in Figure 5, the battery processing method according to Embodiment 2 differs from the battery processing method according to Embodiment 1 in the step of preparing the crushed material (S10A). The other steps are almost the same.

[0057] In carrying out the battery processing method according to Embodiment 2, first, the crushed material is prepared in step (S10A). In carrying out step (S10A), steps (S11) to (S13) are carried out in substantially the same manner as in Embodiment 1.

[0058] Next, in step (S14), the crushed secondary battery is further crushed. Specifically, the primary crushed material produced in step (S13) is crushed. In step (S14), the primary crushed material is crushed using an appropriate crusher.

[0059] Next, in step (S15), the secondary battery crushed in step (S14) is separated. Specifically, the secondary crushed material generated by crushing the primary crushed material is separated. This prepares a crushed material that includes a sheet-like member and an active material layer containing a binder and provided on the sheet-like member. Thus, the crushed material prepared in Embodiment 2 is a sheet member having the active material layer separated from the secondary crushed material. Preferably, the sheet-like member is a positive electrode sheet member, and preferably, the active material layer is a positive electrode active material layer containing a binder. The prepared crushed material may also contain a separator.

[0060] Next, steps (S20) to (S40) are carried out in substantially the same manner as in Embodiment 1. As described above, even when the battery processing method according to Embodiment 2 is carried out, substantially the same effects as in Embodiment 1 can be obtained. In steps (S20) to (S40), as described above, a sheet member having an active material layer is used as the pulverized material, so by carrying out step (S40), the sheet member and the active material layer are separated.

[0061] (Verification experiment) Figure 6 shows the conditions and results of experiments conducted using the battery processing method in the examples and the battery processing method in the comparative examples. Figure 7 is a plot of the relationship between particle size and peeling rate in each of the comparative examples 1-8 and examples 1-2 shown in Figure 6. The verification experiments will be explained with reference to Figures 6 and 7.

[0062] As shown in Figure 6, in Comparative Examples 1 to 6, compared to the battery processing method according to Embodiment 1 described above, the heating step (S20) was omitted, and the pulverized material prepared in the preparation step (S10) was pulverized in the pulverization step (S30) without heating. In Comparative Examples 1 to 6, the pulverization conditions were changed to obtain fragments (particles) of different particle sizes. After pulverization, the sheet-like member (sheet-like member for positive electrode) and the active material layer (positive electrode active material) were separated using a sieve or the like, and the particle size of the sheet-like member fragments and the peeling rate of the active material layer were calculated using the calculation method described above.

[0063] In Comparative Examples 7 and 8, compared to the battery processing method according to Embodiment 1 described above, the temperature at which the pulverized material was heated in the heating step (S20) was set to 110°C, which is lower than the decomposition start temperature of the resin component (binder), and the pulverized material heated at 110°C was pulverized in the pulverization step (S30). In Comparative Examples 7 and 8, the pulverization conditions were changed to obtain fragments (particles) of different particle sizes. After pulverization, the sheet-like member and the active material layer were separated using a sieve or the like, and the particle size of the sheet-like member fragments and the peeling rate of the active material layer were calculated using the calculation method described above.

[0064] In Examples 1 and 2, the battery processing was carried out based on the steps of the battery processing method according to Embodiment 1 described above. In this process, the heating temperature of the pulverized material in the heating step (S20) was set to 180°C and 300°C. These temperatures are all above the decomposition start temperature of the resin components and below the decomposition peak temperature of the resin components.

[0065] The material was pulverized in a process (S30) where the pulverized material was heated at 180°C and 300°C. After pulverization, the sheet-like material and the active material layer were separated using a sieve or the like, and the particle size of the sheet-like material fragments and the peeling rate of the active material layer were calculated using the calculation method described above.

[0066] As shown in Figures 6 and 7, the particle size is approximately 149.3 mm, as in Comparative Example 2. 2 In this case, a peeling rate of approximately 87.4% was obtained. However, by grinding the material to reduce the particle size, materials constituting the outer casing or copper constituting the negative electrode were mixed into the active material layer, and the separation of these from the active material layer deteriorated.

[0067] In order to suppress the incorporation of foreign matter into the active material layer, when the particle size was increased as in Comparative Examples 1 and 3-6, heating was omitted, resulting in a high viscosity of the active material layer, and a tendency was observed for the peeling rate to decrease as the particle size increased. Specifically, when the particle size was 380 mm 2 Beyond a certain point, the peeling rate fell below 50%.

[0068] As in Comparative Example 7, the particle size is approximately 140.7 mm. 2 In this case, a peeling rate of approximately 81.8% was obtained. However, as the particle size decreased, materials constituting the outer casing or copper constituting the negative electrode were mixed into the active material layer, and the separation of these from the active material layer deteriorated.

[0069] When the particle size was increased, as in Comparative Example 8, to suppress the incorporation of foreign matter into the active material layer, the peeling rate decreased compared to Comparative Example 8, becoming approximately 59.0%.

[0070] In contrast, in Example 1, the particle size was approximately 404.6 mm 2 and the peeling rate was 88.6%, which was higher than those of Comparative Examples 1 to 8. Similarly, in Example 2, the particle size was approximately 909.5 mm 2 and the peeling rate was 95.2%, which was higher than those of Comparative Examples 1 to 8.

[0071] Also, in Examples 1 and 2, since the particle sizes were relatively large, it was possible to suppress the mixing of the material constituting the exterior case or copper constituting the negative electrode into the active material layer.

[0072] As described above, by heating the pulverized material at a temperature not lower than the decomposition start temperature of the resin component and lower than the decomposition peak temperature of the resin component, suppressing the consumption of thermal energy, softening the resin component contained in the active material layer at a low temperature, and pulverizing the pulverized material, it has been experimentally confirmed that the active material layer can be peeled from the sheet-like member while reducing the environmental load.

[0073] The embodiments and modifications disclosed this time are illustrative in all respects and not restrictive. The scope of the present invention is indicated by the claims, and includes all modifications within the meaning and scope equivalent to the claims.

Explanation of Reference Numerals

[0074] 1 Pulverized material, 10 Heating chamber, 20 Heat source, 30 Pulverizing chamber, 40 Pulverizer.

Claims

1. A process of discharging the secondary battery to reduce its voltage to below a predetermined value, The process involves crushing the aforementioned secondary battery to obtain a pulverized material containing an active material, a binder, an electrolyte, and a metal foil. A step of heating the pulverized material under reduced pressure at a first temperature to evaporate the electrolyte, A battery processing method comprising the step of further grinding the pulverized material after the step of evaporating the electrolyte to remove the active material from the metal foil.

2. The battery processing method according to claim 1, further comprising the step of heating the pulverized material at a second temperature which is above the decomposition start temperature of the binder and above the first temperature, after the step of evaporating the electrolyte and before the step of peeling the active material from the metal foil.

3. The battery processing method according to claim 2, wherein the first temperature is 90°C or higher and 110°C or lower.

4. The battery processing method according to claim 3, wherein the second temperature is 120°C or higher and 180°C or lower.

5. The battery processing method according to any one of claims 1 to 4, further comprising the step of separating the metal foil and the active material after the step of peeling the active material from the metal foil.

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