Battery processing method and battery processing system

Abstract

This invention provides a battery processing method that can efficiently recover lithium from lithium-ion batteries. [Solution] A battery processing method for a lithium-ion battery having a plurality of battery cells 3, each containing a positive electrode material 31 and a negative electrode material 35, wherein the positive electrode material 31 and the negative electrode material 35 are stacked in the stacking direction A, and gas is generated inside, includes a gas extrusion step of pushing the gas toward the peripheral edge of the battery cell in a plane perpendicular to the stacking direction A, and a lithium deposition step of charging the lithium-ion battery and depositing lithium on the negative electrode material 35.

Description

Technical Field

[0001] The present invention relates to a battery processing method and a battery processing system.

Background Art

[0002] In recent years, the adoption of lithium-ion batteries as in-vehicle batteries for electric vehicles such as electric cars and hybrid vehicles has been expanding. Lithium-ion batteries contain valuable substances containing lithium. It is required to recycle resources by recycling valuable substances from used lithium-ion batteries.

[0003] Patent Document 1 discloses a method of increasing the amount of lithium contained in a positive electrode material by discharging a used lithium-ion battery and then recovering lithium from the positive electrode material.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] The positive electrode material is generally composed of forming a positive electrode active material on a current collector foil such as aluminum. The positive electrode active material contains valuable substances such as nickel, manganese, cobalt, etc. in the case of a ternary system (NMC), for example. To recover valuable substances from the positive electrode active material, the positive electrode material is baked together with a reducing agent, pulverized, and then a black mass containing the positive electrode active material is sorted. Next, the black mass is subjected to solvent extraction step by step, and manganese, cobalt, and nickel are sequentially extracted, and finally lithium is extracted. For this reason, it has been particularly laborious to recover lithium.

[0006] The object of this invention is to provide a battery processing method and a battery processing system that can efficiently recover lithium from lithium-ion batteries. [Means for solving the problem]

[0007] One aspect of the present invention is, A battery processing method for a lithium-ion battery comprising a positive electrode material and a negative electrode material, wherein the positive electrode material and the negative electrode material are stacked in a stacking direction, and gas is generated inside the battery, A gas extrusion step in which the gas is pushed toward the peripheral edge of the lithium-ion battery in a plane perpendicular to the stacking direction, A lithium deposition step is performed, which involves charging the lithium-ion battery and depositing lithium on the negative electrode material. The present invention provides a battery processing method that includes [a specific component].

[0008] Other aspects of the present invention include: A charging device for a lithium-ion battery which includes a positive electrode material and a negative electrode material, wherein the positive electrode material and the negative electrode material are stacked in a stacking direction, and gas is generated inside the battery. A gas extruder that pushes the gas toward the peripheral edge of the lithium-ion battery in a plane perpendicular to the stacking direction, We provide a battery processing system that includes the following features. [Effects of the Invention]

[0009] According to the present invention, lithium can be efficiently recovered from the negative electrode of a lithium-ion battery. [Brief explanation of the drawing]

[0010] [Figure 1] A schematic block diagram illustrating the reuse system according to the first embodiment. [Figure 2] A perspective view showing the schematic configuration of a lithium-ion battery. [Figure 3] A cross-sectional view showing the general configuration of a battery cell. [Figure 4] A diagram showing the schematic configuration of a gas extrusion apparatus. [Figure 5] A flowchart schematically showing the process of reusing a lithium-ion battery. [Figure 6A] A diagram schematically showing an example of the operation of a gas extrusion device. [Figure 6B] A diagram schematically showing an example of the operation of the gas extrusion device following FIG. 6A. [Figure 7A] A diagram schematically showing another example of the operation of the gas extrusion device. [Figure 7B] A diagram schematically showing another example of the operation of the gas extrusion device following FIG. 7A. [Figure 7C] A diagram schematically showing another example of the operation of the gas extrusion device following FIG. 7B.

Embodiments for Carrying Out the Invention

[0011] The inventors of the present invention have conducted intensive research to efficiently recover lithium from a lithium-ion battery. They have found that by intentionally causing lithium precipitation (such as dendrites), which is not desirable in a normal charging reaction, to occur on the negative electrode material, lithium can be efficiently recovered from the lithium-ion battery. Based on this finding, the inventors of the present invention have completed a battery treatment method capable of efficiently recovering lithium from a lithium-ion battery.

[0012] A method for reusing a lithium-ion battery according to an embodiment of the present invention is a battery treatment method for treating a lithium-ion battery including a positive electrode material and a negative electrode material, wherein the positive electrode material and the negative electrode material are laminated in a stacking direction and gas is generated inside, a gas extrusion step of extruding the gas toward the peripheral edge of the lithium-ion battery in a plane perpendicular to the stacking direction, and a lithium precipitation step of charging the lithium-ion battery to precipitate lithium on the negative electrode material and includes.

[0013] Hereinafter, a lithium-ion battery reuse system according to a first embodiment of the present invention will be described while referring to the accompanying drawings. FIG. 1 is a block diagram schematically showing a reuse system 100 for a lithium-ion battery 1. As shown in FIG. 1, the reuse system 100 includes a reuse unit 10 that reuses the lithium-ion battery 1 that has been used once, for example, in an electric vehicle, and a recycling unit 20 that recovers lithium from the reused lithium-ion battery 1. That is, the reuse system 100 is a battery processing system for reusing the lithium-ion battery 1 and then recovering lithium from the lithium-ion battery 1, in other words, for processing the lithium-ion battery 1.

[0014] The reuse unit 10 reuses the once-used lithium-ion battery 1 as a power storage device. Generally, the state of deterioration of a lithium-ion battery for an electric vehicle is determined based on the SOH (State Of Health) indicating how much capacity it has, for example, when fully charged compared to when it was new. When the lithium-ion battery 1 is determined to be inappropriate for use in an electric vehicle based on the degree of deterioration, it is removed from the vehicle and used in the reuse unit 10 as a power storage device for various secondary uses such as the storage of renewable energy such as solar power generation and wind power generation, or a backup power source during disasters. For example, when the SOH becomes 70% or less, it may be determined that it is not appropriate for primary use, that is, for use in an electric vehicle.

[0015] The reuse unit 10 includes a lithium-ion battery 1 reused as a power storage device, a charging device 12, and a gas extrusion device 301. The charging device 12 is configured to be able to charge the lithium-ion battery 1 with an arbitrary charging pattern by adjusting the voltage and current. For example, the lithium-ion battery 1 can be continuously charged with a predetermined voltage and current, and can also be charged (also called pulse charging) with a predetermined voltage and current intermittently. The upper limit of the charging voltage by the charging device 12 is below the withstand voltage of the lithium-ion battery 1, for example, 4.3V or less. The gas extrusion device 301 will be described in detail after the structure of the lithium-ion battery 1 is described.

[0016] The recycling unit 20 includes a dismantling device 21 that dismantles the lithium-ion battery 1 into positive electrode material 31 and negative electrode material 35, etc., through a lithium deposition process described later, if it is determined that the lithium-ion battery 1 cannot be properly reused even in the above secondary reuse, for example, based on SOH; an extraction device 22 that extracts lithium from the dismantled negative electrode material 35; and a recovery device 23 that recovers the extracted lithium. For example, it may be determined that the battery cannot be properly reused even in secondary reuse if the SOH is 40% or less.

[0017] Figure 2 schematically shows a lithium-ion battery 1 installed in an electric vehicle. The lithium-ion battery 1 is a battery pack in which multiple battery modules 4, each incorporating functions such as a charge / discharge circuit and a cooling mechanism, are connected to each other and housed in a case. The battery module 4 is composed of multiple battery cells 3 connected to each other in series or parallel, and is adjusted to the desired capacity and voltage.

[0018] Lithium-ion battery 1 is a rechargeable lithium-ion secondary battery. In this specification, unless otherwise specified, the term lithium-ion battery may collectively refer to battery cells, battery modules, and battery packs.

[0019] Figure 3 is a schematic cross-sectional view of the battery cell 3. As shown in Figure 3, the battery cell 3 according to this embodiment is of the laminated type. The battery cell 3 has a laminated electrode body 38 in which a positive electrode material 31, a separator 34, and a negative electrode material 35 are stacked in this order in the stacking direction A, and a case 40 in which the laminated electrode body 38 is housed.

[0020] In this embodiment, the laminated electrode body 38 is constructed by stacking multiple sets of positive electrode material 31, separator 34, and negative electrode material 35 in the stacking direction A. The battery cell 3 is elongated rectangular in the width direction B when viewed from the stacking direction A.

[0021] The positive electrode material 31 comprises a positive electrode current collector 32 and a positive electrode active material 33 disposed on the surface of the positive electrode current collector 32 facing the separator 34. Multiple positive electrode current collectors 32 have positive electrode current collector ends 32a that are connected to each other at one end (left side in Figure 3) in the width direction B perpendicular to the stacking direction. Suitable metal foils for positive electrodes can be preferably used for the positive electrode current collector 32. Materials used as positive electrode active materials for lithium-ion secondary batteries can be used for the positive electrode active material 33. In this embodiment, the positive electrode current collector 32 is made of aluminum, and the positive electrode active material 33 is made of NMC (nickel, manganese, cobalt).

[0022] The negative electrode material 35 comprises a negative electrode current collector 36 and a negative electrode active material 37 disposed on the surface of the negative electrode current collector 36 facing the separator 34. Multiple negative electrode current collectors 36 have negative electrode current collector ends 36a that are connected to each other at their other ends (right side in Figure 3) in the width direction B. A metal foil suitable for a negative electrode can preferably be used for the negative electrode current collector 36. A material used as a negative electrode active material for lithium-ion secondary batteries can be used for the negative electrode active material 37. In this embodiment, the negative electrode current collector 36 is made of copper, and the negative electrode active material 37 is a carbon material (graphite) with a layered structure.

[0023] The positive electrode active material 33 and the negative electrode active material 37 contain an electrolyte 39. The electrolyte 39 is, for example, an organic solvent on which lithium ions can move. In this embodiment, the electrolyte 39 contains dimethyl carbonate (DMC), ethylene carbonate (EC), and diethyl carbonate (DEC) in a volume ratio of 1:1:1, and lithium hexafluoride phosphate (LiPF6) at a concentration of 1 mol / L.

[0024] The separator 34 is positioned between the positive electrode material 31 and the negative electrode material 35, physically and electrically separating them. The separator 34 may be a porous material having multiple minute pores through which lithium ions can pass. In this embodiment, the separator 34 is a porous membrane made of polyolefin.

[0025] Case 40 has a pair of first cases 41 and second cases 42 provided on both sides of the stacking direction A of the stacked electrode body 38. The first case 41 and the second case 42 are formed in a hat-shaped cross section. The first case 41 has a pair of flange portions 41a located at both ends in the width direction B, and a main body portion 41b located between the pair of flange portions 41a and bulging in a direction away from the second case 42 in the stacking direction A. Similarly, the second case 42 has a pair of flange portions 42a and a main body portion 42b bulging in a direction away from the first case 41.

[0026] Case 40 is formed by joining a first case 41 and a second case 42 with the positive electrode current collector end 32a and the negative electrode current collector end 36a sandwiched between their respective flange portions 41a and 42a. That is, with the laminated electrode body 38 housed in case 40, the positive electrode current collector end 32a and the negative electrode current collector end 36a are sandwiched between the pair of flange portions 41a and 42a, and the remaining portion of the laminated electrode body 38 is housed in the space defined between the pair of main body portions 41b and 42b. With the laminated electrode body 38 housed in case 40, it is pressed against the pair of main body portions 41b and 42b at a predetermined pressure in the stacking direction A. An example of the tab 43 according to the present invention is formed by the portion of the battery cell 3 sandwiched between the pair of flange portions 41a and 42a.

[0027] In this embodiment, it is assumed that gas is generated inside the lithium-ion battery 1, which is deemed unsuitable for proper reuse. When gas is generated inside the lithium-ion battery 1, the outside of the lithium-ion battery 1 swells, so the generation of gas can be confirmed by the appearance of the lithium-ion battery 1. In addition, since the internal pressure of the lithium-ion battery 1 fluctuates due to the generation of gas, the generation of gas can also be confirmed by the fluctuation in the pressing force of the gas extrusion device 301 described later.

[0028] Generally, when gas is generated within the lithium-ion battery 1, the movement of electrons between the positive electrode material 31 and the negative electrode material 35 is inhibited by the gas, making it difficult for charge-discharge reactions to occur. This gas is a by-product generated from the electrolyte 39 during the charge-discharge reactions in the primary and secondary use of the lithium-ion battery 1. This gas is, for example, methane and / or carbon dioxide.

[0029] Next, the gas extrusion device 301 will be described. The gas extrusion device 301 is a device that presses the battery cells 3 in the stacking direction A with a predetermined pressing force. The gas extrusion device 301 may be installed in the lithium-ion battery 1 that has been primarily used in an electric vehicle in order to generate a charge-discharge reaction within the lithium-ion battery 1, or it may be installed in the lithium-ion battery 1 that has been secondarily used in the reuse section 10. Alternatively, a separate gas extrusion device that can adjust the pressing force automatically or manually may be provided. The gas extrusion device 301 is not particularly limited, and any actuator such as a hydraulic cylinder or a pneumatic cylinder can be used.

[0030] Figure 4 is a schematic diagram of the gas extruder 301. Figure 4 also schematically shows the battery cells 3 that are pressed by the gas extruder 301. As shown in Figure 4, the gas extruder 301 has a pair of presser pairs 302, which are provided on both sides of the stacking direction A of the battery cells 3 and are divided in the width direction B of the battery cells 3. In this embodiment, the gas extruder 301 has a central presser pair 302A located in the center of the width direction B, a side presser pair 302B located on one side of the width direction B (left side in Figure 4), and a other side presser pair 302C located on the other side of the width direction B (right side in Figure 4). The presser pairs 302 are not limited to three, but may be divided into two or four or more.

[0031] Next, the reuse of the lithium-ion battery 1 will be explained. Figure 5 is a flowchart that schematically shows the flow of reuse of the lithium-ion battery 1. As shown in Figure 5, if the lithium-ion battery 1 that was installed in the electric vehicle is determined to be in a deteriorated state that is unsuitable for use in the electric vehicle, for example based on the State of Health (SOH), a reuse process (step S1) is carried out. In reuse process S1, the lithium-ion battery 1 is removed from the electric vehicle and put to secondary use in the reuse unit 10.

[0032] When the lithium-ion battery 1 is used for secondary purposes and is used as an energy storage device 11, and is determined to be in a predetermined state of deterioration, the reuse section 10 performs a gas extrusion process (step S2) to push the gas inside the lithium-ion battery 1 towards the peripheral edge 3z, following the secondary use.

[0033] In the gas extrusion process S2, the gas generated inside the battery cell 3 is pushed out toward the peripheral edge 3z by sequentially operating the presser pairs 302 of multiple sets of presser pairs 302 from one end 3b to the other end 3c in the width direction B, or sequentially operating them from the central part 3a in the width direction B to both sides 3b and 3c in the width direction B. Therefore, the battery processing method of this embodiment further includes a gas extrusion process in which the gas is pushed toward the peripheral edge 3z of the battery cell 3 in an in-plane direction perpendicular to the stacking direction A.

[0034] In the gas extrusion step S2, the battery cell 3 is pressed with a pressing force sufficient to allow the gas inside the battery cell 3 to move. In order to generate a charge-discharge reaction within the lithium-ion battery 1 in the subsequent lithium deposition step S3, the pressing force is preferably at least 10 kPa. For example, the pressing force is 10 kPa or more and 1 MPa or less.

[0035] For example, as shown in Figure 6A, the central part 3a in the width direction B of the battery cell 3 may be pressed first, and then, as shown in Figure 6B, the sides 3b and 3c in the width direction B may be pressed as well. As a result, the gas is pushed out from the central part 3a side to the sides 3b and 3c side of the battery cell 3 in the width direction B. Note that the parts 3a, 3b, and 3c of the battery cell 3 remain pressed to prevent the pushed-out gas from flowing back into the central part 3a, etc. of the battery cell 3.

[0036] Furthermore, as shown in Figure 7A, after pressing one end 3b in the width direction B of the battery cell 3, the central part 3a in the width direction may be additionally pressed as shown in Figure 7B, and the other end 3c in the width direction B may be additionally pressed as shown in Figure 7C. As a result, the gas is pushed out from the end 3b side to the other end 3c side in the width direction B. Note that the parts 3a, 3b, and 3c of the battery cell 3 remain pressed to prevent the pushed-out gas from flowing back into the central part 3a, etc. of the battery cell 3.

[0037] While parts 3a, 3b, and 3c of the battery cell 3 are being pressed by the gas extrusion process S2, a lithium deposition process (step S3) is performed to deposit lithium onto the negative electrode material 35. In the lithium deposition process S3, the lithium-ion battery 1 is charged in such a way that lithium is deposited onto the negative electrode material 35.

[0038] In this embodiment, lithium is deposited on the negative electrode material 35 by charging the lithium-ion battery 1 using high-rate charging. High-rate charging means charging with a large current that intentionally generates lithium on the negative electrode material 35 during charging.

[0039] For example, if the lithium-ion battery 1 is a so-called capacity type (also called energy type) installed in an electric vehicle, it is preferable to charge it with a current of 2C or more. Also, if the lithium-ion battery 1 is a so-called high-output type (also called power type) installed in a hybrid vehicle, it is preferable to charge it with a current of 10C or more. Here, a current of 1C means the current required to fully charge each lithium-ion battery in one hour. By continuously charging at a high rate for a predetermined period of time, lithium can be deposited on the negative electrode material 35.

[0040] In this specification, a lithium-ion battery 1 is considered to be a capacity-type battery if its energy density is 600 Wh / L or higher. Furthermore, a lithium-ion battery 1 is considered to be a high-power type battery if its power density is 4000 kW / L or higher.

[0041] If the charging current becomes excessive due to high-rate charging, undesirable side reactions may occur, such as gasification of the electrolyte 39 due to heat generation, deformation and damage to each component, and excessive charging current is undesirable from the standpoint of energy saving. For example, if the lithium-ion battery 1 is a capacity type, it is preferable to set the upper limit of the charging current to about 3C. On the other hand, if the lithium-ion battery 1 is a high-output type, it is preferable to set the upper limit of the charging current to about 20C.

[0042] In this embodiment, the electrolyte 39 is easily present around the negative electrode material 35 by pushing the gas that inhibits the charge-discharge reaction toward the peripheral portion 3z. As a result, even in a battery cell 3 that generates gas, a charging reaction can be generated in the negative electrode material 35. Therefore, even in a battery cell 3 that generates gas, the charging reaction can be promoted by high-rate charging. As a result, lithium is easily deposited in the negative electrode material 35.

[0043] Next, the lithium-ion battery 1 is removed from the reuse section 10 and the battery dismantling process (step S4) is performed by the dismantling device 21. In the battery dismantling process S4, the lithium-ion battery 1 is dismantled into its constituent components, such as the positive electrode material 31, separator 34, negative electrode material 35, and case 40. If the intention is to recover only lithium, at least the negative electrode material 35 may be dismantled. The dismantling device 21 may be any device that automatically dismantles the lithium-ion battery 1. Alternatively, the lithium-ion battery 1 may be dismantled manually using tools or the like without using the dismantling device 21.

[0044] Next, a lithium extraction process (step S5) is carried out. In lithium extraction process S5, lithium is extracted from the disassembled negative electrode material 35. In lithium extraction process S5, the negative electrode current collector 36 and negative electrode active material 37 are removed from the negative electrode material 35 by the extraction device 22, which then filters the negative electrode material 35 after it has been leached with water, thereby extracting an aqueous solution containing lithium ions.

[0045] Finally, a lithium recovery process (step S6) is carried out. In lithium recovery process S6, lithium is recovered from an aqueous solution containing lithium ions. In lithium recovery process S6, the lithium is dissolved in carbonated water by the recovery device 23 and then filtered to recover lithium as lithium carbonate.

[0046] In the above embodiment, the case in which the presser pair 302 is divided in the width direction B of the battery cell 3 was described as an example, but it may also be divided in the height direction C which is perpendicular to the stacking direction A and the width direction B of the battery cell 3, or it may even be divided in both the width direction B and the height direction C.

[0047] In other words, the battery processing method according to this embodiment is A battery processing method for a lithium-ion battery 1 comprising a positive electrode material 31 and a negative electrode material 35, wherein the positive electrode material 31 and the negative electrode material 35 are stacked in the stacking direction A, and gas is generated inside the battery, A gas extrusion step S2 is performed in which gas is pushed out toward the peripheral edge 3z of the lithium-ion battery 1 in a plane perpendicular to the stacking direction A, A lithium deposition process S3 is performed in which lithium is deposited on the negative electrode material 35 by charging the lithium-ion battery 1. It includes.

[0048] As a result, since the negative electrode material 35 is generally constructed by laminating graphite in layers on a current collector foil such as copper, it contains fewer valuable substances compared to the positive electrode material 31, which contains multiple valuable substances such as cobalt, nickel, and manganese. Therefore, unlike when recovering lithium from the positive electrode material 31, there is no need to perform stepwise solvent extraction of multiple valuable metals, and lithium can be efficiently recovered from the negative electrode material 35. Furthermore, even in the case of a lithium-ion battery 1 that generates gas, the gas can be pushed towards the peripheral edge 3z by the gas extrusion device 301, thereby inducing a charging reaction in the negative electrode material 35. As a result, lithium is easily deposited in the negative electrode material 35.

[0049] The lithium-ion battery 1 reuse system 100 relating to this disclosure is not limited to the configuration described in the above embodiment, and various modifications are possible.

[0050] In the above embodiment, a laminated lithium-ion battery was described as an example, but it is not limited to this. For example, a cylindrical or rectangular lithium-ion battery may be used, which is constructed by winding a strip-shaped laminated electrode body, in which a strip-shaped positive electrode material, a strip-shaped separator, and a strip-shaped negative electrode material are stacked in the stacking direction A, into a cylindrical or rectangular shape. In the case of cylindrical and rectangular types, the stacking direction corresponds to the radial direction perpendicular to the winding direction.

[0051] Although the explanation was given on a cell-by-cell basis, it can also be done on a module-by-module or battery pack-by-battery basis. If done on a battery pack basis, a pressing device may be pre-installed inside the battery pack. [Explanation of Symbols]

[0052] 1. Lithium-ion battery 3 battery cells 4 Battery Modules 10. Reuse Department 12 Charging device 20 Recycling Department 21 Demolition equipment 22 Extraction device 23 Recovery device 31 Positive electrode material 34 Separator 35. Negative electrode material 38. Stacked electrode body 39 Electrolyte 40 cases 100 Reuse Systems 301 Gas extruder

Claims

1. A battery processing method for a lithium-ion battery comprising a positive electrode material and a negative electrode material, wherein the positive electrode material and the negative electrode material are stacked in a stacking direction, and gas is generated inside the battery, A gas extrusion step in which the gas is pushed toward the peripheral edge of the lithium-ion battery in a plane perpendicular to the stacking direction, A lithium deposition step is performed, which involves charging the lithium-ion battery and depositing lithium on the negative electrode material. A battery processing method, including the following.

2. In the gas extrusion step, the gas is extruded from the central part of the lithium-ion battery in the plane. The battery processing method according to claim 1.

3. The aforementioned battery processing method is: Following the lithium deposition step, a battery dismantling step is performed, in which at least the negative electrode material is dismantled from the lithium-ion battery. A lithium extraction step for extracting lithium from the negative electrode material, The battery processing method according to claim 1 or 2, further comprising:

4. A charging device for a lithium-ion battery which includes a positive electrode material and a negative electrode material, wherein the positive electrode material and the negative electrode material are stacked in a stacking direction, and gas is generated inside the battery. A gas extruder that pushes the gas toward the peripheral edge of the lithium-ion battery in a plane perpendicular to the stacking direction, A battery processing system equipped with the following features.

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