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 comprising a positive electrode material 31, a negative electrode material 35, and an electrolyte 39, wherein the positive electrode material 31 and the negative electrode material 35 are stacked in the stacking direction A, includes a lithium deposition step in which the lithium-ion battery is charged by increasing the pressing force in the stacking direction A in the central part in a plane perpendicular to the stacking direction A compared to the remaining part, thereby 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 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 processing a lithium-ion battery comprising a positive electrode material, a negative electrode material, and an electrolyte, wherein the positive electrode material and the negative electrode material are stacked in a stacking direction, A lithium deposition process is performed by charging the lithium-ion battery 1 by increasing the pressing force in the stacking direction in the central part of the plane perpendicular to the stacking direction compared to the remaining part, thereby 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 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, A pressing device that presses the central portion of the lithium-ion battery in a plane perpendicular to the stacking direction with a pressing force in the stacking direction that is increased compared to the remaining portion, and 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 showing the reuse system according to this 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 the pressing device. [Figure 5]A flowchart illustrating the general process of reusing lithium-ion batteries. [Modes for carrying out the invention]

[0011] The inventors have diligently conducted research to efficiently recover lithium from lithium-ion batteries and have discovered that lithium can be efficiently recovered from lithium-ion batteries by intentionally inducing lithium deposition (e.g., dendrites), which is undesirable in normal charging reactions, on the negative electrode material. Based on this finding, the inventors have completed a battery processing method that can efficiently recover lithium from lithium-ion batteries.

[0012] A method for reusing lithium-ion batteries according to one embodiment of the present invention is: A battery processing method for processing a lithium-ion battery comprising a positive electrode material, a negative electrode material, and an electrolyte, wherein the positive electrode material and the negative electrode material are stacked in a stacking direction, A lithium deposition process is performed by charging the lithium-ion battery 1 by increasing the pressing force in the stacking direction in the central part of the plane perpendicular to the stacking direction compared to the remaining part, thereby depositing lithium on the negative electrode material. It includes.

[0013] The lithium-ion battery reuse system according to this embodiment will be described below with reference to the attached drawings. Figure 1 is a schematic block diagram showing the lithium-ion battery reuse system 100. As shown in Figure 1, the reuse system 100 has a reuse unit 10 that reuses a lithium-ion battery 1 that has been used primarily in, for example, an electric vehicle, and a recycling unit 20 that recovers lithium from the reused lithium-ion battery 1. In other words, the reuse system 100 is a battery processing system for reusing a lithium-ion battery 1 and then recovering lithium from the lithium-ion battery 1, or in other words, for processing a lithium-ion battery 1.

[0014] The reuse unit 10 reuses the once - used lithium - ion battery 1 as a power storage device. Generally, for a lithium - ion battery used in an electric vehicle, the degradation state is judged based on the SOH (State Of Health) which indicates how much capacity there is, for example, compared to when it is new at full charge. When the lithium - ion battery 1 is judged not to be suitable for use in an electric vehicle based on the degree of degradation, it is removed from the vehicle and used in the reuse unit 10 as a power storage device for various secondary uses such as storing renewable energy like solar power generation and wind power generation, or as a backup power source during disasters. For example, when the SOH becomes 70% or less, it may be judged that it is not suitable 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 pressing device 301. The charging device 12 is configured to adjust voltage and current to be able to charge the lithium - ion battery 1 in an arbitrary charging pattern. For example, the lithium - ion battery 1 can be continuously charged at a predetermined voltage and current, and can also be charged intermittently at a predetermined voltage and current (also called pulse charging). 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 pressing device 301 will be described in detail after the structure of the lithium - ion battery 1 is explained.

[0016] When it is judged that the lithium - ion battery 1 cannot be properly used even in the above - mentioned secondary use, for example, based on the SOH, the recycling unit 20 has a disassembling device 21 that disassembles the lithium - ion battery 1 into a positive electrode material 31, a negative electrode material 35, etc. through a lithium precipitation process described later, an extraction device 22 that extracts lithium from the disassembled negative electrode material 35, and a recovery device 23 that recovers the extracted lithium. For example, when the SOH becomes 40% or less, it may be judged that it cannot be properly used even in secondary use.

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

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

[0019] Figure 3 is a cross-sectional view schematically showing the battery cell 3. As shown in Figure 3, the battery cell 3 according to this embodiment is a laminate 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 laminated in this order in the lamination 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 constituted by a plurality of sets of a positive electrode material 31, a separator 34, and a negative electrode material 35 laminated in the lamination direction A. The battery cell 3 has an elongated rectangular shape in the width direction B when viewed from the lamination direction A.

[0021] The positive electrode material 31 has 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. The plurality of positive electrode current collectors 32 have a positive electrode current collecting end portion 32a connected to each other at one end portion (the left side in Figure 3) in the width direction B orthogonal to the lamination direction. For the positive electrode current collector 32, a metal foil suitable for the positive electrode can be preferably used. For the positive electrode active material 33, a material used as the positive electrode active material of a lithium-ion secondary battery can be used. 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 the lithium-ion battery 1 has deteriorated relatively quickly, and in particular, that the electrolyte 39 has depleted at the peripheral portion 3z of the battery cell 3.

[0028] Next, the pressing device 301 will be described. The pressing device 301 is a device that presses the battery cells 3 in the stacking direction A with a predetermined pressing force. The pressing device 301 may be installed in the lithium-ion battery 1 that was first 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 was secondarily used in the reuse section 10. Alternatively, a separate pressing device that can adjust the pressing force automatically or manually may be provided. The pressing device 301 is not particularly limited, and any actuator such as a hydraulic cylinder or a pneumatic cylinder can be used.

[0029] Figure 4 is a schematic diagram of the pressing device 301. Figure 4 also schematically shows the battery cell 3 that is pressed by the pressing device 301. As shown in Figure 4, the pressing device 301 has a pair of presser pairs 302 provided on both sides of the stacking direction A of the battery cell 3, and divided in the width direction B of the battery cell 3. In this embodiment, the pressing device 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.

[0030] 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.

[0031] When the lithium-ion battery 1 is used for secondary purposes and is determined to be in a predetermined state of degradation after being used as an energy storage device, the reuse section 10 performs a lithium deposition process (step S2) following the secondary use. In the lithium deposition process S2, the lithium-ion battery 1 is charged while being pressed in the stacking direction A under predetermined pressing conditions.

[0032] In the lithium deposition process S2, the battery cell 3 is locally pressed by activating at least some of the multiple pairs of pressers 302. Specifically, as shown in Figure 4, by activating only the central presser pair 302A located in the center of the battery cell 3 in the width direction B and / or height direction C, only the central part 3a in the width direction B of the battery cell 3 is pressed. Therefore, in the lithium deposition process S2, the battery cell 3 is pressed by increasing the pressing force in the stacking direction A on the central part 3a in the plane perpendicular to the stacking direction A compared to the remaining parts 3b and 3c.

[0033] For example, if the presser pairs 302 are divided into four substantially equal parts along the width B, only the two inner presser pairs 302 in the width B may be activated. Alternatively, if the presser pairs 302 are divided into five substantially equal parts along the width B, only the three inner presser pairs 302 in the width B, or only the central presser pair 302 in the width B, may be activated. In other words, in the lithium deposition process S2, the portion of the battery cell 3 that includes the central part 3a but does not include the peripheral part 3z may be pressed.

[0034] Generally, in order to generate a charge-discharge reaction within the lithium-ion battery 1, the battery cells 3 need to be pressed (i.e., restrained) in the stacking direction. In the lithium deposition process S2, the battery cells 3 are pressed with a pressure at least sufficient to generate the charge-discharge reaction. For example, this pressure is between 10 kPa and 1 MPa.

[0035] "Increasing the pressing force in the central portion 3a in the stacking direction A compared to the remaining portions 3b and 3c" also means reducing the pressing force in the remaining portions 3b and 3c when the entire battery cell 3 is being pressed evenly. For example, in a lithium-ion battery 1 that is being reused in the reuse portion 10, i.e., is being pressed evenly throughout, reducing or releasing the pressing force in the remaining portions 3b and 3c is included in the lithium deposition process S2. In this way, when the lithium deposition process S2 is carried out using the pressing device provided in the lithium-ion battery 1 that has been reused, it is possible to carry out the work efficiently without the hassle of attaching a separate pressing device to the lithium-ion battery 1, compared to when the lithium deposition process S2 is carried out by attaching a separate pressing device to the lithium-ion battery 1.

[0036] In the lithium deposition process S2, the lithium-ion battery 1 is charged in such a way that lithium is deposited on the negative electrode material 35 while the central part 3a of the battery cell 3 is locally pressed by the pressing device 301.

[0037] 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.

[0038] 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.

[0039] 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.

[0040] 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.

[0041] Furthermore, when charging the lithium-ion battery 1, increasing the pressing force in the central part 3a promotes (concentrates) the charging reaction in the negative electrode material 35 corresponding to the central part 3a. In addition, while electrolyte tends to escape outward from the peripheral part 3z in both sides 3b and 3c of the battery cell 3, causing liquefaction depletion, the electrolyte 39 tends to remain in the central part 3a because it is separated from the peripheral part 3z. Therefore, increasing the pressing force in the central part 3a where the electrolyte 39 tends to remain makes it easier to efficiently deposit lithium in the negative electrode material 35 corresponding to the central part 3a. As a result, the charging current is concentrated in the area where the electrolyte 39 remains and the charging reaction is promoted, so high-rate charging is performed in a localized area, making it easier to deposit lithium locally.

[0042] In the lithium deposition step S2, the lithium-ion battery 1 only needs to be charged while being pressed. The pressing step of the lithium-ion battery 1 by the pressing device 301 and the charging step of the lithium-ion battery 1 by the charging device 12 may be started simultaneously, or one of them may be started first. That is, after the pressing step by the pressing device 301 is performed, the charging step by the charging device 12 may be performed while the pressing state by the pressing device 301 is maintained.

[0043] Next, the lithium-ion battery 1 is removed from the reuse section 10 and the battery dismantling process (step S3) is performed by the dismantling device 21. In the battery dismantling process S3, 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 S4) is performed. In lithium extraction process S4, lithium is extracted from the disassembled negative electrode material 35. In lithium extraction process S4, 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, after which the negative electrode material 35 is leached with water and then filtered, and an aqueous solution containing lithium ions is extracted. In lithium extraction process S4, lithium is selectively extracted from the portion of the negative electrode material 35 corresponding to the central portion 3a where lithium was locally deposited in the lithium deposition process S2. Of the multiple disassembled negative electrode materials 35, which portion of the negative electrode material 35 corresponds to the central portion 3a can be identified by visual inspection, or based on the portion pressed by the pressing device 301 (i.e., the central portion 3a). This allows for more efficient extraction of lithium.

[0045] Finally, a lithium recovery process (step S5) is carried out. In lithium recovery process S5, lithium is recovered from an aqueous solution containing lithium ions. In lithium recovery process S5, 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 processing a lithium-ion battery 1 comprising a positive electrode material 31, a negative electrode material 35, and an electrolyte 39, wherein the positive electrode material 31 and the negative electrode material 35 are stacked in the stacking direction A, In the lithium deposition step S2, the lithium-ion battery 1 is charged by increasing the pressing force in the stacking direction A on the central portion 3a in the plane perpendicular to the stacking direction A compared to the remaining portions 3b and 3c, thereby depositing lithium on the negative electrode material 35. 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 made of, for example, copper, it contains fewer valuable substances compared to the positive electrode material 31, which contains multiple types of valuable substances such as cobalt, nickel, and manganese. Therefore, as is the case when recovering lithium from the positive electrode material 31, it is not necessary to perform stepwise solvent extraction of multiple types of valuable metals, and lithium can be recovered efficiently from the negative electrode material 35. Furthermore, by increasing the pressing force in the central part 3a of the lithium-ion battery 1, where the electrolyte 39 tends to remain relatively well, lithium can be locally deposited in the portion of the negative electrode material 35 corresponding to the central part 3a. As a result, lithium can be recovered even more efficiently.

[0049] In lithium deposition process S2, charging is performed by high-rate charging. As a result, lithium can be intentionally deposited on the negative electrode material 35 by charging at a high charging rate.

[0050] In the lithium extraction process S4, lithium is selectively extracted from the portion of the negative electrode material 35 corresponding to the central part 3a. As a result, lithium can be extracted even more efficiently.

[0051] 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.

[0052] 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 batteries, the stacking direction corresponds to the radial direction perpendicular to the winding direction.

[0053] 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.

[0054] In the lithium deposition step S2, charging at a high rate is not required. That is, if the lithium-ion battery 1 is a capacity type, it may be charged with a current of less than 2C, for example. Also, if the lithium-ion battery 1 is a high-power type, it may be charged with a current of less than 10C, for example. [Explanation of Symbols]

[0055] 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 Pressing device

Claims

1. A battery processing method for processing a lithium-ion battery comprising a positive electrode material, a negative electrode material, and an electrolyte, wherein the positive electrode material and the negative electrode material are stacked in a stacking direction, A lithium deposition process is performed by charging the lithium-ion battery by increasing the pressing force in the stacking direction in the central part of the plane perpendicular to the stacking direction compared to the remaining part, thereby depositing lithium on the negative electrode material. A battery processing method, including the following.

2. In the lithium deposition process, charging is performed by high-rate charging. 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. In the lithium extraction step, lithium is selectively extracted from the portion of the negative electrode material corresponding to the central part. The battery processing method according to claim 3.

5. A charging device 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, A pressing device that presses the central portion of the lithium-ion battery in a plane perpendicular to the stacking direction with a pressing force in the stacking direction that is increased compared to the remaining portion, and A battery processing system equipped with the following features.

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