How to dispose of secondary batteries

Abstract

To provide a processing method for a secondary battery that can safely and efficiently recover a material constituting a secondary battery and contribute to energy efficiency.SOLUTION: A processing method for a secondary battery containing metallic lithium in a negative electrode includes a water vapor contacting step of contacting a battery cell with water vapor at 40 to 175°C.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a method for treating a secondary battery. [Background technology]

[0002] In recent years, research and development into secondary batteries that contribute to energy efficiency has been conducted in order to ensure that more people have access to affordable, reliable, sustainable and advanced energy.

[0003] Known secondary batteries include those that use metallic lithium as the negative electrode. Such secondary batteries contain many valuable materials, including metallic lithium, and it is therefore preferable to recover and reuse the valuable materials from used secondary batteries. However, when reusing secondary batteries that contain metallic lithium, it is highly dangerous to disassemble the battery cell while highly reactive metallic lithium remains inside the battery cell. Therefore, techniques have been proposed for deactivating metallic lithium remaining inside the battery cell and reducing its reactivity (see, for example, Patent Documents 1 to 3). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 06-338353 [Patent Document 2] Patent No. 7109702 [Patent Document 3] International Publication No. 2021 / 201055 Summary of the Invention [Problem to be solved by the invention]

[0005] Patent Document 1 discloses a technology for supplying a substance reactive to a negative electrode active material, with the aim of safely dismantling used lithium batteries. However, the technology requires dismantling the battery under an atmosphere of dry inert gas or the like, which requires time and cost for dismantling. Furthermore, Patent Document 1 does not mention conditions suitable for supplying the reactive substance, other than keeping the concentration of hydrogen gas during processing below the explosion limit.

[0006] Patent Document 2 discloses a technique for treating battery waste, which includes a first heat treatment step and a second heat treatment step of heating the battery waste in an atmosphere containing a larger amount of oxygen than that in the first heat treatment step. Patent Document 3 discloses a heat treatment method for heating battery waste while adjusting the oxygen partial pressure in a furnace, as a method for heat treating lithium-containing battery waste.

[0007] The technology disclosed in Patent Document 2 sets the maximum temperature of the battery waste to 400°C to 800°C, while the technology disclosed in Patent Document 3 sets the maximum temperature of the battery waste to 500°C to 650°C. However, in either of the above temperature ranges, there is a problem that the valuables cannot be efficiently recovered because the molten metallic lithium reacts with valuables other than metallic lithium. In addition, there is a problem that the energy consumption and CO2 emissions increase due to the high temperature treatment.

[0008] The present invention has been made in consideration of the above problems, and aims to provide a method for treating secondary batteries that can safely and efficiently recover materials that constitute secondary batteries and contribute to improving energy efficiency. [Means for solving the problem]

[0009] (1) The present invention relates to a method for treating a secondary battery containing metallic lithium in the negative electrode, the method comprising a water vapor contact step of contacting a battery cell with water vapor at 40-175°C.

[0010] According to the invention of (1), it is possible to provide a method for treating secondary batteries that can safely and efficiently recover materials constituting secondary batteries and contribute to improving energy efficiency.

[0011] (2) The method for treating a secondary battery according to (1), wherein the relative humidity of the gas contacting the battery cell in the water vapor contact step is 40% or more.

[0012] According to the invention of (2), secondary batteries can be treated more efficiently and with less energy.

[0013] (3) The method for treating a secondary battery according to (1) or (2), further comprising a water vapor contacting step of contacting the battery cell with water vapor at 40-70°C.

[0014] According to the invention of (3), the secondary battery can be processed with less energy.

[0015] (4) The method for treating a secondary battery according to any one of (1) to (3), further comprising, after the water vapor contact step, a recovery step of dissolving in water and recovering the deactivated battery cell constituent materials including the metallic lithium.

[0016] According to the invention of (4), the materials constituting the battery cells can be recovered more safely and the secondary batteries can be processed.

[0017] (5) The method for treating a secondary battery according to any one of (1) to (4), which does not include a roasting step of roasting the battery cells.

[0018] According to the invention of (5), by treating a secondary battery without roasting the battery cells, it is possible to treat the secondary battery more safely and with less energy. [Brief description of the drawings]

[0019] [Figure 1] 4 is a flowchart showing a method for treating a secondary battery according to the present embodiment. [Diagram 2]1 is a conceptual cross-sectional view showing a configuration of a secondary battery cell according to an embodiment of the present invention. [Diagram 3] 1 is a graph showing the relationship between the conditions of gas brought into contact with a negative electrode and the Li reaction rate. [Figure 4] 1 is a graph showing the relationship between the conditions of gas brought into contact with a battery cell and the Li reaction rate. [Diagram 5] 1 is a graph showing the relationship between the amount of water vapor brought into contact with a battery cell and the deactivation time. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0020] <Outline of secondary battery disposal method> The method for treating a secondary battery according to this embodiment is a method for treating a secondary battery that contains metallic lithium (Li) in the negative electrode by deactivating the metallic lithium (Li). The method for treating a secondary battery according to this embodiment includes a water vapor contact step S3 shown in Fig. 1. The water vapor contact step S3 is a step for contacting the battery cell with water vapor at 40-175°C.

[0021] The target of the secondary battery treatment method according to the present embodiment is a solid secondary battery having a solid electrolyte. Hereinafter, the secondary battery that is the target of the secondary battery treatment method according to the present embodiment will be described as a solid secondary battery. On the other hand, the secondary battery is not limited to a solid secondary battery, and may be, for example, a battery that uses an electrolytic solution as an electrolyte, or a polymer battery in which an electrolytic solution is contained in a polymer gel.

[0022] <Solid secondary battery> Fig. 2 is a cross-sectional view showing an outline of the configuration of a solid secondary battery included in the target of the secondary battery treatment method according to the present embodiment. As shown in Fig. 2, a battery cell 1 of the solid secondary battery has a negative electrode 2 including a negative electrode active material 21 and a negative electrode current collector 22, a positive electrode 3 including a positive electrode active material 31 and a positive electrode current collector 32, a solid electrolyte layer 4 laminated between the negative electrode 2 and the positive electrode 3, and exterior bodies 51 and 52 that house a laminate composed of the negative electrode 2, the solid electrolyte layer 4, and the positive electrode 3.

[0023] (Negative electrode layer) The negative electrode 2 includes, for example, a negative electrode current collector 22 and a negative electrode active material 21 laminated thereon. The negative electrode 2 may include, in addition to the above, a binder, a conductive assistant, an electrolyte, etc. The binder, conductive assistant, electrolyte, etc. are not particularly limited, and any substance known as an electrode material for a secondary battery can be used.

[0024] The negative electrode active material 21 essentially contains lithium metal. The negative electrode active material 21 may contain other negative electrode active materials in addition to lithium metal. Examples of negative electrode active materials other than lithium metal include lithium titanate (Li4Ti5O 12 transition metal oxides such as TiO2, Nb2O3 and WO3, metal sulfides, metal nitrides, carbon materials such as graphite, soft carbon and hard carbon, and metallic indium and lithium alloys.

[0025] The negative electrode current collector 22 is not particularly limited, and a material known as a negative electrode current collector for a solid secondary battery can be used. The negative electrode current collector preferably contains at least one selected from the group consisting of copper metal, stainless steel, and aluminum, and more preferably contains copper metal. This is because the method for treating a secondary battery according to this embodiment can preferably recover copper metal in a solid secondary battery containing copper metal as the negative electrode current collector.

[0026] (Positive electrode layer) The positive electrode 3 includes, for example, a positive electrode current collector 32 and a positive electrode active material 31 laminated thereon. The positive electrode 3 may contain, in addition to the above, a binder, a conductive additive, an electrolyte, etc. The binder, conductive additive, electrolyte, etc. are not particularly limited, and any substance known as an electrode material for a secondary battery can be used.

[0027] The positive electrode active material 31 is not particularly limited, and a material known as a positive electrode active material for a secondary battery can be used. As the positive electrode active material, for example, ternary cathode materials such as LiCoO2, LiNiO2, NCM (Li(NixCoyMnz)O2, (0 < x < 1, 0 < y < 1, 0 < z < 1, x + y + z = 1)), layered cathode active material particles such as LiVO2, LiCrO2, spinel-type cathode active materials such as LiMn2O4, Li(Ni 0.25 Mn 0.75 )2O4, LiCoMnO4, Li2NiMn3O8, olivine-type cathode active materials such as LiCoPO4, LiMnPO4, LiFePO4, etc. can be used.

[0028] The positive electrode current collector 32 is not particularly limited, and a material known as a positive electrode current collector for a secondary battery can be used. Examples of the positive electrode current collector 32 include metal foils such as stainless steel (SUS) foil and aluminum (Al) foil.

[0029] (Solid electrolyte layer) The solid electrolyte layer 4 is a layer containing a solid electrolyte as an essential component. The solid electrolyte is not particularly limited, and examples include sulfide-based solid electrolytes, oxide-based solid electrolytes, nitride-based solid electrolytes, halide-based solid electrolytes, etc. Among them, it is preferable to use a sulfide-based solid electrolyte as the solid electrolyte. This is because the method for treating a secondary battery according to this embodiment can control the generation of hydrogen sulfide that may occur during the treatment of the secondary battery even when a sulfide-based solid electrolyte is used as the solid electrolyte. Examples of the sulfide-based solid electrolyte include LPS-based halogens (Cl, Br, I), Li2S-P2S5, Li2S-P2S5-LiI, etc. Note that the description of "Li2S-P2S5" means a sulfide-based solid electrolyte material formed using a raw material composition containing Li2S and P2S5.

[0030] (Outer package) The exterior bodies 51 and 52 house the laminated negative electrode 2, solid electrolyte layer 4, and positive electrode 3. As the exterior bodies 51 and 52, for example, a pair of laminate films can be used, as shown in Fig. 2. The configuration of the exterior body is not particularly limited to the above, and a known exterior body applied to a secondary battery can be used.

[0031] <How to dispose of secondary batteries> The method for treating a secondary battery according to this embodiment essentially includes a water vapor contact step S3 shown in Fig. 1. The method for treating a secondary battery according to this embodiment preferably includes a module disassembly step S1, a film opening step S2, a water vapor contact step S3, and a recovery step S4 in this order, as shown in Fig. 1.

[0032] (Module dismantling process S1) The module dismantling step S1 is a step of dismantling a battery module composed of a plurality of battery cells into a plurality of battery cells and module constituent members. The module constituent members are not particularly limited, but may include, for example, bus bars, voltage detection wires, thermistors, bind bars, end plates, separators, harnesses, battery cases, battery case fixing members, cell voltage / temperature monitor units, etc. The secondary battery processing method according to this embodiment includes the module dismantling step S1, so that the time required for deactivation can be reduced.

[0033] On the other hand, the method for treating a secondary battery according to this embodiment does not necessarily have to include the module dismantling step S1, which can reduce the risk of work in the module dismantling step S1.

[0034] (Film opening process S2) The film opening step S2 is a step of opening at least a part of the exterior bodies 51 and 52 of the battery cell 1. Opening means that the laminated body made of the exterior bodies 51 and 52 is sealed to allow gas including water vapor to flow into the interior of the exterior bodies 51 and 52, and it is not necessary to completely separate the exterior bodies 51 and 52. In addition, the method of opening is not particularly limited, and the joint between the exterior bodies 51 and 52 may be peeled off, or holes may be made in any positions of the exterior bodies 51 and 52.

[0035] (Water vapor contact step S3) The water vapor contact step S3 is a step in which the battery cell 1 is brought into contact with water vapor at 40-175°C to deactivate the metallic lithium contained in the battery cell 1. By bringing the metallic lithium into contact with the water vapor, the metallic lithium reacts with water to produce lithium hydroxide. As the above reaction progresses, the reactivity of lithium can be reduced (deactivated).

[0036] The temperature of the water vapor that contacts the battery cell 1 in the water vapor contact step S3 is 40-175°C. This temperature range is below the melting point of metallic lithium (approximately 180°C), and therefore the water vapor contact step S3 can deactivate metallic lithium without melting it. If metallic lithium melts, there is a risk that the positive electrode active material (e.g., NCM) will react with the molten metallic lithium. In this case, the expensive positive electrode active material cannot be recovered in a state where its molecular structure is maintained, and the recovery efficiency of the positive electrode active material decreases. For the above reasons, the water vapor contact step S3 according to this embodiment can improve the recovery efficiency of the positive electrode active material.

[0037] The relative humidity of the gas (air) containing water vapor that contacts the battery cell 1 in the water vapor contact step S3 is preferably 40% or more. From the viewpoint of energy efficiency, it is preferable that the temperature of the water vapor in the water vapor contact step S3 is as low as possible. However, since the amount of saturated water vapor decreases as the temperature decreases, there are cases where the amount of water vapor required for efficient deactivation of metallic lithium cannot be secured. On the other hand, from the viewpoint of shortening the processing time, it is preferable that the temperature of the water vapor in the water vapor contact step S3 is as high as possible. By setting the relative humidity of the gas in the water vapor contact step S3 to 40% or more, even if the temperature of the gas containing water vapor is set to less than 90°C or 70°C or less, for example, the battery cell 1 can be efficiently deactivated from the viewpoint of energy efficiency, and is also preferable from the viewpoint of processing time. Note that, from the viewpoint of processing time only, the temperature of the water vapor may be set to 90°C to 175°C.

[0038] The amount of water vapor (g / m) that comes into contact with the battery cell 1 in the water vapor contact step S3 3 ) is calculated by the following formula (1). The amount of water vapor can be set from the viewpoint of the above-mentioned energy efficiency and processing time. The amount of water vapor may be set as a threshold value at which deterioration of the material constituting the battery cell 1 is suppressed. This makes it possible to set an optimal amount of water vapor taking into consideration the deactivation rate of metallic lithium and the suppression of material deterioration. Water vapor amount (g / m 3 ) = Amount of saturated water vapor at a given temperature (g / m 3 ) × relative humidity at a given temperature (%) (1)

[0039] (Recovery process S4) The recovery step S4 is a step of immersing the battery cell 1 (battery cell constituent material) that has been subjected to the water vapor contact step S3 in water. The recovery step S4 makes it possible to separate water-soluble substances, such as lithium hydroxide and sulfide-based solid electrolyte, generated in the water vapor contact step S3 from water-insoluble substances, such as the negative electrode current collector 22 and the positive electrode active material 31. In addition, by controlling the amount of gas generated in the water vapor contact step S3, it is possible to reduce the amount of gas generated in the recovery step S4.

[0040] The recovery step S4 includes a step of recovering a positive electrode material such as a positive electrode active material (e.g., NCM) which is a water-insoluble substance. In the recovery step S4, the positive electrode active material (e.g., NCM) can be recovered in a state where it is little damaged. The recovered positive electrode active material may be appropriately treated, such as by adding lithium again or by repairing the structure, depending on the recovered state. In addition, at the same timing as this step, a negative electrode current collector 22 (e.g., copper foil) which is a water-insoluble substance other than the positive electrode active material may be recovered. The recovery step S4 may include a step of recovering only lithium from the aqueous solution containing lithium and the like which is generated. In addition, it may include a step of separating and recovering other components from the solution after lithium is recovered.

[0041] The method for treating a secondary battery according to this embodiment may include any other steps as long as they do not impair the effects of the present invention. For example, a determination step of determining whether or not the metallic lithium contained in the battery cell 1 has been deactivated may be provided between the water vapor contact step S3 and the recovery step S4. In the determination step, for example, the voltage of the battery cell may be monitored, and a state in which the voltage is equal to or lower than a predetermined threshold value may be determined as the metallic lithium being deactivated.

[0042] On the other hand, the secondary battery processing method according to this embodiment preferably does not include a roasting step of roasting the battery cells 1 throughout all steps. By not including the roasting step, it is possible to reduce the energy required for processing and the generation of CO2.

[0043] The preferred embodiments of the present invention have been described above, but the present invention is not limited to the above-described embodiments, and includes modifications and improvements within the scope of the present invention that can achieve the object of the present invention. EXAMPLES

[0044] Next, an embodiment of the present invention will be described, but the present invention is not limited to this embodiment.

[0045] [Deactivation gas contact test for negative electrode] Fig. 3 is a graph showing the relationship between the reaction time (hr) and the Li reaction rate (%) when the negative electrode (negative electrode 2 in Fig. 1, which is configured as negative electrode current collector 22: copper foil, and negative electrode active material 21: metallic lithium) is contacted with water vapor (HO) as a deactivating gas under the conditions (temperature, temperature, and relative humidity) shown in Fig. 3. The Li reaction rate (%) is calculated by the following formula (2). Li reaction rate (%) = amount of Li hydroxide after deactivation treatment / amount of metallic Li before deactivation treatment × 100 (2)

[0046] The amount of Li hydroxide and the amount of metallic Li in the above formula (2) were measured by processing the observation area with a focused ion beam (FIB) and then measuring the Li reaction rate with an electron microscope using energy dispersive X-ray spectroscopy (SEM-EDX). A high-performance FIB-SEM hybrid device, Ethos NX5000 (manufactured by Hitachi High-Technologies), was used for the measurement.

[0047] [Deactivation gas contact test for battery cells] FIG. 4 is a graph showing the relationship between the reaction time (hr) and the Li reaction rate (%) in a battery cell (a battery cell 1 in which the respective components in FIG. 1 are configured as follows: anode current collector 22: copper foil, anode active material 21: metallic lithium, solid electrolyte layer 4: sulfide-based solid electrolyte, cathode active material 31: NCM (Li(NixCoyMnz)O2, and cathode current collector 32: aluminum foil) when a part of the exterior body is opened and water vapor (HO) is brought into contact with the battery cell under the conditions (temperature and relative humidity) shown in FIG. 4. That is, FIG. 4 corresponds to the water vapor contact step S3 in the above embodiment.

[0048] From the results in Figure 4, when using water vapor (HO) as the deactivation gas to deactivate metallic lithium contained in a battery cell, the amount of water vapor (g / m 3 ) is higher, the time required for Li deactivation is shorter, and the amount of water vapor (g / m 3 It is clear that the deactivation rate can be controlled by the amount of water vapor (g / m 3 The calculation method for is as described above.

[0049] [Setting the amount of water vapor (deactivation condition)] Figure 5 shows the relationship between the deactivation time (min) and the amount of water vapor (g / m), where the deactivation time is the time required for the metallic Li from the cell edge to the center to react with water vapor. 3 ) is a graph showing the relationship between

[0050] In the graph of Figure 5, the more the amount of water vapor is increased, the shorter the deactivation time becomes. Therefore, for example, a target time is set from the viewpoint of shortening the treatment time and from the viewpoint of energy efficiency, and the amount of water vapor (g / m) is set under the condition that the deactivation time is equal to or shorter than the target time. 3 ) conditions may be set. [Explanation of symbols]

[0051] 1 Battery Cell 2 negative electrode 21 Negative electrode active material (metallic lithium) S3 Steam contact process S4 Recovery process

Claims

1. A method for treating a secondary battery containing metallic lithium in a negative electrode, comprising the steps of: a film opening step of opening at least a portion of an exterior body of the battery cell; The method for treating a secondary battery includes a water vapor contacting step of contacting the opened battery cell with water vapor at 40 to 175°C.

2. 2. The method for treating a secondary battery according to claim 1, wherein the relative humidity of the gas contacting the battery cell in the water vapor contact step is 40% or more.

3. The method for treating a secondary battery according to claim 1 or 2, further comprising a water vapor contacting step of contacting the battery cell with water vapor at 40 to 70°C.

4. 3. The method for treating a secondary battery according to claim 1, further comprising, after the water vapor contact step, a recovery step of dissolving the deactivated battery cell constituent material containing the metallic lithium in water and recovering it.

5. The method for treating a secondary battery according to claim 1 , which does not include a roasting step of roasting the battery cells.

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