Method for regenerating lithium ion secondary battery

Abstract

The invention provides a method for regenerating a lithium ion secondary battery, which can improve the implementation efficiency. A method for regenerating a lithium ion secondary battery disclosed herein includes: a Li deposition step in which a lithium ion secondary battery is subjected to pulsed charging and discharging in a low-temperature environment so as to deposit Li in a negative electrode; and an active material disintegration step in which the positive electrode active material is disintegrated by repeatedly charging and discharging the lithium ion secondary battery in a range in which the positive electrode is located in a low potential region.

Description

Technical Field

[0001] The present disclosure relates to a method for recycling a lithium-ion secondary battery. Background Art

[0002] Lithium-ion secondary batteries are widely used in various fields. These lithium-ion secondary batteries use various materials containing valuable metals such as Ni and Co. For example, as the positive electrode active material, lithium transition metal composite oxides such as lithium nickel composite oxide, lithium cobalt composite oxide, lithium nickel cobalt composite oxide, and lithium nickel cobalt manganese composite oxide are used. In addition, aluminum or the like is used for the positive electrode core. On the other hand, carbon materials or the like are used for the negative electrode active material. Moreover, copper or the like is used for the negative electrode core. Further, aluminum or the like is used for the battery case housing these electrodes.

[0003] In recent years, the development of recycling technologies for recovering valuable metals from used lithium-ion secondary batteries and reusing them as battery materials has been progressing. In this recycling technology, first, the used lithium-ion secondary battery is calcined. Then, a black powder (so-called black mass) containing valuable metals of the positive electrode active material is recovered from the calcined lithium-ion secondary battery, and the black mass is subjected to acid leaching. Thereby, a metal solution in which metal components (Li, Ni, Co, Mn, Al, Cu, etc.) in the black mass are dissolved in an acidic solution can be obtained. In addition, the carbon component in the black mass can be separated by this acid leaching. On the other hand, various separation treatments (neutralization precipitation, solvent extraction, etc.) are performed on the metal solution after acid leaching. Thereby, the desired metal components can be extracted and reused as battery materials.

[0004] Examples of such recycling technologies are disclosed in Patent Documents 1 to 3. In these patent documents, it is described that when recycling a lithium-ion secondary battery, first, the lithium-ion secondary battery is subjected to a discharging treatment.

[0005] Prior Art Documents

[0006] Patent Documents

[0007] Patent Document 1: Japanese Unexamined Patent Application Publication No. 2022-163095

[0008] Patent Document 2: Japanese Unexamined Patent Application Publication No. 2021-72157

[0009] Patent Document 3: Japanese Unexamined Patent Application Publication No. 2013-101830 Summary of the Invention

[0010] However, as a result of intensive studies by the present inventors, it has been found that there are problems such as insufficient implementation efficiency in the recycling process, for example, a long time is required for acid leaching of metal components from the black mass, in the prior art.

[0011] The technology disclosed herein is completed to solve the above problems, and aims to provide a method for regenerating a lithium-ion secondary battery that can improve the implementation efficiency.

[0012] The method for regenerating a lithium-ion secondary battery disclosed herein includes: a Li precipitation step of performing pulse charge and discharge on the lithium-ion secondary battery in a low-temperature environment to precipitate Li in the negative electrode; and an active material disintegration step of repeatedly performing charge and discharge on the lithium-ion secondary battery within a range where the positive electrode is in a low potential region to disintegrate the positive electrode active material.

[0013] According to such a configuration, a method for regenerating a lithium-ion secondary battery that can improve the implementation efficiency can be provided. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 is a flowchart showing the respective steps of a method for regenerating a lithium-ion secondary battery according to one embodiment.

[0015] Figure 2 is a longitudinal sectional view schematically showing an internal structure of an example of a lithium-ion secondary battery used in a method for regenerating a lithium-ion secondary battery according to one embodiment.

[0016] Figure 3 is schematically showing Figure 2 a perspective view of an electrode body of the lithium-ion secondary battery shown. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0017] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. It should be noted that matters not mentioned in this specification and necessary for the implementation of the present disclosure can be grasped as design matters of those skilled in the art based on the prior art in this field. The present invention can be implemented based on the content disclosed in this specification and common technical knowledge in this field. In addition, in the following drawings, components and parts having the same functions are denoted by the same reference numerals for description. In addition, the dimensional relationships (length, width, thickness, etc.) in each drawing do not reflect the actual dimensional relationships. It should be noted that the numerical range expressed as "A to B" in this specification includes A and B.

[0018] It should be noted that in this specification, a "secondary battery" refers to a power storage device that can be repeatedly charged and discharged. In addition, in this specification, a "lithium-ion secondary battery" refers to a secondary battery that uses lithium ions as charge carriers and realizes charge and discharge by the movement of charges of lithium ions between the positive and negative electrodes.

[0019] As an example of the method for regenerating a lithium-ion secondary battery of the present disclosure, the respective steps of the method for regenerating a lithium-ion secondary battery of the present embodiment are shown in Figure 1Flowchart. The method for recycling a lithium-ion secondary battery according to this embodiment must include: a Li precipitation step S101 of performing pulse charge and discharge on the lithium-ion secondary battery in a low-temperature environment to precipitate Li in the negative electrode; an active material disintegration step S102 of repeatedly performing charge and discharge on the lithium-ion secondary battery within a range where the positive electrode is in a low potential region to disintegrate the positive electrode active material.

[0020] In Figure 1 In the example shown, the method for recycling a lithium-ion secondary battery according to this embodiment further includes, as an optional step: a roasting step S103 of heating the lithium-ion secondary battery that has undergone the active material disintegration step S102 at a specified temperature; a black substance recovery step S104 of recovering a black substance containing the constituent metal of the positive electrode active material from the lithium-ion secondary battery that has undergone the roasting step S103; an acid leaching step S105 of immersing the obtained black substance in an acidic solution to obtain an acid leaching solution containing the constituent metal of the positive electrode active material; and a metal recovery step S106 of separating and recovering the constituent metal of the positive electrode active material from the acid leaching solution.

[0021] That is, the Li precipitation step S101 and the active material disintegration step S102 can be regarded as a pretreatment method for the lithium-ion secondary battery to be recycled. Therefore, in the method for recycling a lithium-ion secondary battery according to this embodiment, a pretreatment method for the lithium-ion secondary battery to be recycled including the Li precipitation step S101 and the active material disintegration step S102 is implemented.

[0022] The method for recycling a lithium-ion secondary battery according to this embodiment mainly targets material recovery. The recycling method according to this embodiment can typically be used, for example, to obtain raw materials for positive electrode active materials by recovering valuable metals such as transition metals (e.g., Ni, Co, Mn) from lithium-ion secondary batteries, and can also be used to obtain raw materials for other components of lithium-ion secondary batteries. However, the content of recycling lithium-ion secondary batteries is not limited to this. First, a specific example is given to illustrate the lithium-ion secondary battery used in the recycling method according to this embodiment.

[0023] 1. Lithium-ion secondary battery

[0024] Figure 2 is a longitudinal sectional view schematically showing the internal structure of an example of the lithium-ion secondary battery used in the recycling method according to this embodiment. Figure 3 Schematically shows Figure 2 a perspective view of the electrode body of the lithium-ion secondary battery shown in Figure 2 As shown in

[0025] (1) Outer package

[0026] Regarding the exterior body, as long as it is a container for housing the electrode body and the electrolyte, it is not particularly limited. For example, Figure 2 the exterior body 10 shown is a box-shaped housing. This box-shaped exterior body 10 is made of a metal material (such as aluminum (Al)) having a certain strength, for example. As Figure 2 shown, a positive terminal 12 and a negative terminal 14 are attached to the exterior body 10. This positive terminal 12 and negative terminal 14 are connected to the electrode body 20 inside the exterior body 10. Specifically, the positive terminal 12 is connected to the positive electrode plate 30 of the electrode body 20 (refer to Figure 3 ). This positive terminal 12 is made of aluminum (Al) or the like. On the other hand, the negative terminal 14 is connected to the negative electrode plate 40 of the electrode body 20. This negative terminal 14 is made of copper (Cu) or the like.

[0027] And, in Figure 2 the exterior body 10 shown, a liquid injection hole 16 is formed. This liquid injection hole 16 is an opening that communicates the inside and outside of the exterior body 10. In the manufacture of the lithium ion secondary battery 1, an electrolyte is filled into the interior of the exterior body 10 through this liquid injection hole 16. Then, the liquid injection hole 16 is sealed by a sealing plug 17 after the electrolyte is filled.

[0028] (2) Electrode body

[0029] The electrode body 20 is a power generation element of the lithium ion secondary battery 1. As Figure 3 shown, the electrode body 20 includes a positive electrode plate 30, a negative electrode plate 40, and a separator 50. It should be noted that Figure 3 the electrode body 20 shown is a wound electrode body. This wound electrode body is an electrode body formed by winding a long strip-shaped laminate in which the positive electrode plate 30, the negative electrode plate 40, and the separator 50 are laminated. It should be noted that the structure of the electrode body 20 is not limited to the wound electrode body and may be other conventionally known structures (such as a laminated electrode body).

[0030] The positive electrode plate 30 includes a foil-shaped positive electrode core 32 and a positive electrode active material layer 34 provided on the surface of the positive electrode core 32. The positive electrode core 32 is made of aluminum (Al) or the like. In addition, the positive electrode active material layer 34 is a composite material layer containing a positive electrode active material, a conductive material, a binder, and the like. The positive electrode active material is a metal material containing at least lithium (Li). As an example of the positive electrode active material, lithium transition metal composite oxides such as lithium nickel composite oxide, lithium cobalt composite oxide, lithium manganese composite oxide, lithium nickel manganese composite oxide, lithium manganese cobalt composite oxide, lithium nickel cobalt composite oxide, lithium nickel cobalt manganese composite oxide, and lithium nickel cobalt aluminum composite oxide can be cited. In addition, as other examples of the positive electrode active material, lithium transition metal phosphate compounds such as lithium iron phosphate, lithium manganese phosphate, and lithium manganese iron phosphate can be cited. In addition, as the conductive material, carbon materials such as acetylene black and graphite can be cited. As the binder, resin materials such as polyvinylidene fluoride (PVdF) can be cited.

[0031] From the viewpoint of the ease of disintegration of the positive electrode active material, the crystal structure of the positive electrode active material is preferably a layered structure. As the positive electrode active material, lithium nickel cobalt manganese composite oxide and lithium nickel cobalt aluminum composite oxide are preferred, and lithium nickel cobalt manganese composite oxide is more preferred.

[0032] On the other hand, the negative electrode plate 40 includes a foil-shaped negative electrode core 42 and a negative electrode active material layer 44 provided on the surface of the negative electrode core 42. The negative electrode core 42 is made of copper (Cu) or the like. In addition, the negative electrode active material layer 44 is a composite material layer containing a negative electrode active material, a binder, a thickener, and the like. As an example of the negative electrode active material, graphite can be cited. The graphite can be natural graphite or artificial graphite, and the graphite can be amorphous carbon-coated graphite in the form of being covered with an amorphous carbon material. As other examples of the negative electrode active material, other carbon materials such as hard carbon and soft carbon can be cited. In addition, as still other examples of the negative electrode active material, lithium titanate (LTO), silicon carbide (SiC), a composite containing carbon and silicon, silicon oxide (SiO X ) and the like can be cited. In addition, as the binder, styrene-butadiene rubber (SBR) or the like is used. As the thickener, carboxymethyl cellulose (CMC) or the like is used.

[0033] The separator 50 is an insulating sheet interposed between the positive electrode plate 30 and the negative electrode plate 40. For example, resin materials such as polyethylene (PE), polypropylene (PP), polyester, cellulose, and polyamide are used for the separator 50. In addition, a heat-resistant layer containing inorganic fillers can be formed on the surface of the separator 50. As the inorganic fillers, inorganic oxides such as alumina, magnesia, silica, and titania, nitrides such as aluminum nitride and silicon nitride, metal hydroxides such as calcium hydroxide, magnesium hydroxide, and aluminum hydroxide, clay minerals such as mica, talc, boehmite, zeolite, apatite, and kaolin can be cited.

[0034] (3) Electrolyte

[0035] In the present lithium ion secondary battery 1, an electrolyte is present between the positive electrode plate 30 and the negative electrode plate 40. Thereby, charge carriers (Li ions) can move between the positive electrode plate 30 and the negative electrode plate 40. It should be noted that the form of the electrolyte is not limited to the technology disclosed herein and can be adopted in a conventionally known form without particular limitation. As an example of the form of the above electrolyte, a non-aqueous electrolyte, a gel-like electrolyte, a solid electrolyte, etc. can be cited.

[0036] The lithium ion secondary battery 1 is preferably for in-vehicle use (i.e., for use as a drive power source for vehicles such as electric vehicles (BEV), hybrid electric vehicles (HEV), plug-in hybrid electric vehicles (PHEV), etc.), but is not limited thereto. The lithium ion secondary battery 1 can be used as a power source for electronic devices and the like.

[0037] 2. Method for regenerating a lithium ion secondary battery

[0038] Hereinafter, each step of the method for regenerating the lithium ion secondary battery of the present embodiment will be described in detail. As Figure 1 shown, the method for regenerating the lithium ion secondary battery of the present embodiment includes a Li precipitation step S101 and an active material disintegration step S102 as essential steps, and a roasting step S103, a black substance recovery step S104, an acid leaching step S105, and a metal recovery step S106 as optional steps.

[0039] Thus, in the regeneration method of the present embodiment, first, the Li precipitation step S101 and the active material disintegration step S102 are performed. In this specification, the disintegration of the positive electrode active material means that the particles of the positive electrode active material are refined due to rupture or the like (i.e., the particle size (specifically, the median particle size D50 measured by the laser diffraction scattering method) becomes smaller).

[0040] Here, when charging and discharging the lithium ion secondary battery in the low potential region of the positive electrode, the crystal size changes due to the insertion and extraction of Li into and from the positive electrode active material. Therefore, by repeatedly charging and discharging in the low potential region of the positive electrode, the crystal structure of the positive electrode active material can be disintegrated by the change in crystal size, and particle rupture or the like can occur.

[0041] However, when a lithium ion secondary battery has been used for a long time, since the Li ions released from the positive electrode active material are immobilized on the negative electrode active material or the negative electrode surface, the number of ions re-stored in the positive electrode active material becomes smaller. As a result, the potential of the positive electrode active material cannot be restored to a low state. As a result, when attempting to make the battery voltage a low voltage, since the negative electrode potential rises to achieve balance, the low potential region of the positive electrode cannot be fully utilized for charging and discharging.

[0042] Therefore, in the regeneration method of the present embodiment, Li is first deposited on the negative electrode. At this time, by performing pulse charge and discharge in a low-temperature environment, a large amount of Li can be deposited on the surface of the negative electrode. Since the potential of metallic lithium is lower than that of the negative electrode active material, if the deposited Li is made to function as the negative electrode and the exchange between the positive electrode and Li ions is performed, the positive electrode can be charged and discharged in a low-potential region.

[0043] In a lithium-ion secondary battery, regarding the deposition of Li on the negative electrode, it is usually avoided from the viewpoints of capacity reduction and short circuit caused by dendritic growth of metallic lithium. Nevertheless, for the above reasons, in the regeneration method of the present embodiment, the Li deposition step is first performed.

[0044] (1) Li deposition step S101

[0045] The lithium-ion secondary battery used for the Li deposition step S101 is preferably a used lithium-ion secondary battery, but is not particularly limited. It can also be an unused lithium-ion secondary battery that is considered a defective product during manufacturing and has not been shipped. Thus, while reducing the burden on the environment, materials for lithium-ion secondary batteries can be manufactured.

[0046] In the Li deposition step S101, pulse charge and discharge are performed on the lithium-ion secondary battery in a low-temperature environment. Here, the deposition conditions of Li are strictly speaking different according to the battery design. Therefore, the deposition conditions of Li can be appropriately set according to the battery design.

[0047] Here, an amount of Li that generates a degree of function as the negative electrode is deposited on the negative electrode. Li is likely to deposit at low temperatures. Therefore, for example, when pulse charge and discharge are performed at room temperature (i.e., around 25°C ± 10°C), an insufficient amount of Li can be deposited. Therefore, in the regeneration method of the present embodiment, pulse charging is performed in a low-temperature environment, whereby an insufficient amount of Li can be deposited.

[0048] As the temperature in this low-temperature environment (i.e., the temperature of pulse charge and discharge), it is preferably 10°C or lower, more preferably 5°C or lower, and further preferably 0°C or lower. On the other hand, the temperature in the low-temperature environment is not particularly limited, but from the viewpoints of ease of obtaining low temperature and energy consumption for low temperature, it is preferably -30°C or higher. Therefore, as the low-temperature environment, a temperature environment of -30°C to 10°C is preferred, a temperature environment of -30°C to 5°C is more preferred, and a low-temperature environment of -30°C to 0°C is further preferred.

[0049] In addition, in order to precipitate metallic Li, pulse charge and discharge is adopted as the charge and discharge method. Here, the higher the charge and discharge rate, the easier it is to precipitate metallic Li. Therefore, the current value (i.e., current amplitude) during pulse charge and discharge is not particularly limited as long as it is within the range where Li is precipitated at the negative electrode. For example, it is 2.5C to 200C, preferably 3C to 150C, and more preferably 5C to 100C. It should be noted that 1C refers to the current value capable of charging the battery capacity (Ah) predicted based on the theoretical capacity of the positive electrode in 1 hour.

[0050] In pulse charge and discharge, the charge and discharge switching time (i.e., pulse width) is not particularly limited as long as it is within the range where Li is precipitated at the negative electrode. For example, it is 0.01 second to 20 seconds, preferably 0.1 second to 10 seconds.

[0051] The number of cycles of pulse charge and discharge is not particularly limited as long as it is within the range where Li is precipitated at the negative electrode. For example, it is 50 cycles or more, preferably 100 cycles or more, more preferably 500 cycles or more, further preferably 800 cycles or more, and particularly preferably 1000 cycles or more. In addition, the number of cycles of pulse charge and discharge can be 3000 cycles or less, can be 2000 cycles or less, or can be 1500 cycles or less.

[0052] The state of charge (SOC) of the lithium ion secondary battery during pulse charge and discharge is not particularly limited as long as it is within the range where the above-mentioned pulse charge and discharge can be performed. The SOC of the lithium ion secondary battery can be within the range of 1% to 99%, can be within the range of 10% to 90%, can be within the range of 50% or less, or can be within the range of 30% or less.

[0053] The Li precipitation step S101 can be carried out, for example, in a low-temperature thermostat, a low-temperature constant-temperature chamber, etc., by disposing a lithium ion secondary battery and using a charging device such as a known charger.

[0054] (2) Active material disintegration step S102

[0055] In the active material disintegration step S102, charge and discharge processing different from that in the Li precipitation step S101 is carried out. In the active material disintegration step S102, the lithium ion secondary battery is repeatedly charged and discharged within the range where the positive electrode is in the low potential region to disintegrate the positive electrode active material.

[0056] The charge and discharge conditions vary depending on the battery design, so they can be appropriately set according to the battery design. The range of the low potential region of the positive electrode is, for example, a range where the positive electrode potential (lithium reference) is 3.7V (vs Li + / Li) or less. Specifically, for example, the upper limit of the voltage during charging is set so that the positive electrode potential becomes 3.7V (vs Li +On the other hand, the lower limit of the voltage during discharge is set such that the positive electrode potential is 1.5 V (vs Li + / Li) to 3.0 V (vs Li + / Li) (for example, 1.5 V (vs Li + / Li), preferably 2.5 V (vs Li + / Li)). Therefore, in the active material disintegration step S102, the potential of the positive electrode is, for example, 1.5 V (vs Li + / Li) to 3.7 V (vs Li + / Li), preferably 2.5 V (vs Li + / Li) to 3.7 V (vs Li + / Li), and the lithium ion secondary battery is repeatedly charged and discharged.

[0057] The rate of charge and discharge is not particularly limited as long as it is within the range where the positive electrode active material disintegrates. Regarding the rate of charge and discharge, since the positive electrode resistance is high, the rate is usually very low. The current value of charge and discharge is, for example, 0.001 C to 0.1 C, preferably 0.005 C to 0.05 C, and more preferably 0.005 to 0.02 C.

[0058] As described above, by repeatedly charging and discharging in the low potential region of the positive electrode, the positive electrode active material can be disintegrated by utilizing the change in the crystal grain size caused by the insertion and extraction of Li into and from the positive electrode active material. The number of cycles of this charge and discharge is not particularly limited as long as it is within the range where the positive electrode active material disintegrates. The disintegration of the positive electrode active material can be caused by about 5 cycles of charge and discharge. Therefore, the number of cycles of charge and discharge is, for example, 5 cycles or more, preferably 7 cycles or more, and more preferably 10 cycles or more.

[0059] The temperature condition of the active material disintegration step S102 is not particularly limited. The active material disintegration step S102 can be carried out at room temperature (for example, 25 °C ± 10 °C).

[0060] The active material disintegration step S102 can be carried out using a known charging device such as a charger.

[0061] It should be noted that when the crystal structure of the positive electrode active material is a layered structure, it is very easy to disintegrate the positive electrode active material through the active material disintegration step S102. As the positive electrode active material, lithium nickel cobalt manganese composite oxide and lithium nickel cobalt aluminum composite oxide are preferred, and lithium nickel cobalt manganese composite oxide is particularly preferred. In addition, the negative electrode active material can be graphite.

[0062] By implementing the above-mentioned Li precipitation step S101 and active material disintegration step S102, the positive electrode active material can be disintegrated and refined in the lithium-ion secondary battery. Therefore, the reduction in the particle size and / or the increase in the surface area of the positive electrode active material due to refinement contribute to improving the implementation efficiency of subsequent steps (i.e., the steps for regeneration). For example, in the case of performing the step of acid leaching the metal component from the black material, since the dissolution rate of the metal component increases, the implementation efficiency of this step is improved. In addition, by refining the positive electrode active material, the positive electrode active material layer and the positive electrode core become easily peeled off, thereby increasing the recovery amount and recovery efficiency of the black material.

[0063] After the Li precipitation step S101 and the active material disintegration step S102, known steps can be appropriately selected and implemented according to the material to be regenerated as desired, and the lithium-ion secondary battery can be regenerated. In Figure 1 the example shown, a roasting step S103, a black material recovery step S104, an acid leaching step S105, and a metal recovery step S106 are performed.

[0064] (3) Roasting step S103

[0065] In the roasting step S103, the lithium-ion secondary battery that has undergone the above-mentioned Li precipitation step S101 and active material disintegration step S102 (i.e., the lithium-ion secondary battery in which the positive electrode active material is disintegrated) is heated at a specified temperature. Thereby, while removing the liquid components (such as the electrolyte solution, etc.) in the lithium-ion secondary battery, the resin components (such as the binder, separator, etc.) can be carbonized. In addition, by implementing the roasting step S103, its function as a battery can be stopped. Thereby, subsequent steps can be safely implemented.

[0066] The roasting step S103 can be performed according to a known method. Here, if the heating temperature of the roasting step S103 is increased, the transfer of oxygen elements from the oxide of the valuable metal (such as transition metal composite oxide, etc.) to the carbon material (such as the negative electrode active material, etc.) is likely to occur. Thereby, the valuable metal can be reduced to the metallic state. By the active material disintegration step S102, the positive electrode active material is refined, so the valuable metal in the metallic state is also refined. Therefore, the valuable metal in the metallic state can be dissolved at a high dissolution rate in the subsequent acid leaching step S105, further improving the implementation efficiency of the regeneration method.

[0067] From the viewpoint of efficiently reducing the valuable metal, the heating temperature of the roasting step S103 is preferably 400 °C or higher, more preferably 500 °C or higher, further preferably 600 °C or higher, and particularly preferably 700 °C or higher.

[0068] On the other hand, from the perspective of reducing valuable metals, the upper limit of the heating temperature is not particularly limited. The heating temperature can be 1500 °C or lower, can be 1400 °C or lower, or can be 1300 °C or lower. It should be noted that if the cost required for heating up is considered, the upper limit of the heating temperature is preferably 1200 °C or lower, more preferably 1100 °C or lower, and particularly preferably 1000 °C or lower.

[0069] In addition, from the perspective of reducing valuable metals, the roasting step S103 is preferably carried out in an atmosphere with a low oxygen concentration (for example, an oxygen concentration of 5 vol% or less, preferably 3 vol% or less, more preferably 1 vol% or less, and particularly preferably 0.1 vol% or less). Therefore, the roasting step S103 is preferably carried out in an inert atmosphere such as argon or nitrogen.

[0070] (4) Black substance recovery step S104

[0071] In the black substance recovery step S104, the black substance is recovered from the lithium-ion secondary battery that has undergone the roasting step S103. The black substance is a powder containing the constituent metals of the positive electrode active material. Generally, since it is black, this powder is called the black substance. The black substance recovery step S104 can be carried out according to a known method (for example, powder recovery based on the pulverization and screening of a lithium-ion secondary battery).

[0072] For example, in Figure 2 the lithium-ion secondary battery 1 shown, the electrode body 20 is housed inside the housing 10. Therefore, first, the housing 10 is broken, and then the internal electrode body 20 is further finely broken. The obtained solid components are screened to remove the housing 10, the positive electrode core 32, and the negative electrode core 42. Thus, a powder containing the constituent metals of the positive electrode active material (i.e., the black substance) can be recovered. In this way, by breaking the housing 10 and the electrode body 20, it becomes easier to remove the housing 10, the positive electrode core 32, and the negative electrode core 42, and it is possible to easily reduce the content of impurities (such as Al and Cu) in the black substance, and improve the recovery efficiency of valuable metals (such as Li, Co, Ni, and Mn). In the regeneration method of the present embodiment, by making the positive electrode active material finer in the active material disintegration step S102, the valuable metals in the metal state generated in the roasting step S103 are also made finer. Therefore, the screening efficiency is improved. As a result, the implementation efficiency in the regeneration method of the present embodiment is improved. In addition, since the positive electrode active material is made finer, the positive electrode active material layer becomes easier to peel off from the positive electrode core, and thus, the recovery amount and recovery efficiency of the black substance are also improved.

[0073] It should be noted that in the black substance recovery step S104, impurities such as Al and Cu may not be completely separated from the black substance. As will be described in detail later, even if these impurities are contained in the black substance, the impurities can be removed through subsequent steps (acid leaching step S105, metal recovery step S106, etc.). Therefore, in the method for recycling a lithium-ion secondary battery according to the present embodiment, the black substance recovery step S104 may also be omitted.

[0074] (5) Acid leaching step S105

[0075] In the acid leaching step S105, the black substance obtained in the black substance recovery step S104 is immersed in an acidic solution. Thereby, an acid leaching solution in which metal components (Li, Ni, Co, Mn, Cu, Al, etc.) in the black substance are dissolved in the acidic solution can be prepared. On the other hand, carbon in the black substance is not dissolved in the acidic solution and thus precipitates as a residue. Thereby, carbon can be removed.

[0076] The acid leaching step S105 can be carried out according to a known method. As an example, the pH of the acidic solution is preferably -1.5 to 1.5 (more preferably -0.5 to 0.5). Thereby, the metal components in the black substance can be appropriately dissolved. It should be noted that specific examples of the acidic solution include inorganic acids such as sulfuric acid, nitric acid, hydrochloric acid, and phosphoric acid, and organic acids such as citric acid, ascorbic acid, oxalic acid, and acetic acid. In addition, in the acid leaching step S105, it is preferable to perform a filtration treatment on the acid leaching solution after acid leaching. Thereby, undissolved components (especially carbon components) can be efficiently removed. It should be noted that the temperature of the acidic solution is preferably 50°C or higher (more preferably 55°C or higher, particularly preferably 60°C or higher). Thereby, the time required for the acid leaching step S105 can be shortened. In addition, the upper limit of the temperature of the acidic solution is not particularly limited and can be 90°C or lower, 85°C or lower, or 80°C or lower.

[0077] In the recycling method of the present embodiment, by making the positive electrode active material finer in the active material disintegration step S102, the valuable metals in the metal state generated in the roasting step S103 are also made finer. Therefore, the specific surface area of the valuable metals increases, and the acid leaching rate can be very high. Therefore, in the recycling method of the present embodiment, the implementation efficiency of acid leaching is improved. Even when the positive electrode active material is directly subjected to acid leaching, since the positive electrode active material is made finer, the acid leaching rate is very high.

[0078] (6) Metal recovery step S106

[0079] In the metal recovery step S106, the constituent metals of the positive electrode active material are separated and recovered. As described above, the acid leachate obtained in the acid leaching step S105 contains metal components such as Li, Al, Cu, Co, Ni, and Mn. In the metal recovery step S106, at least one of the constituent metals of the positive electrode active material is separated from these metal components. It is preferable to separate each of these metal components contained in the acid leachate. Thereby, valuable metals can be recovered from the acid leachate. It should be noted that in the metal recovery step S106, conventionally known treatment techniques applicable to metal extraction can be employed without particular limitation.

[0080] For example, in the metal recovery step S106 of the present embodiment, a neutralization precipitation step, a Mn extraction step, a Co extraction step, a Ni extraction step, a Li separation step, etc. are carried out according to the type of metal to be recovered. Hereinafter, these steps will be specifically described.

[0081] (a) Neutralization precipitation step

[0082] In the neutralization precipitation step, a neutralizing agent is added to the acid leachate obtained in the acid leaching step S105. As a result, a precipitate containing aluminum hydroxide (Al(OH)3) precipitates in the acid leachate. As a result, most of the Al in the acid leachate is removed and Al can be recovered. It should be noted that as the neutralizing agent used in this step, an alkaline solution with a pH of 11 to 14 (preferably pH 12 to 14) can be used. Specific examples of the above alkaline solution include an aqueous sodium hydroxide solution, calcium hydroxide, ammonia water, etc. In addition, in this step, it is preferable to filter the acid leachate to separate the precipitate. Thereby, Al(OH)3 can be efficiently removed from the acid leachate.

[0083] (b) Mn extraction step

[0084] In the Mn extraction process, Mn is extracted from the acid leachate. For example, in this process, an organic solvent (the first extraction solution) with high extractability for Mn and low extractability for Li, Al, Cu, Co, and Ni can be added to the acid leachate. Then, the acid leachate and the first extraction solution are stirred to make them suspended. As a result, Mn in the acid leachate dissolves in the first extraction solution. Then, it is left to stand until the two solutions are separated. Thus, an Mn solution with Mn dissolved in the first extraction solution and an acid leachate from which Mn has been removed can be obtained. It should be noted that as the first extraction solution, a phosphoric acid ester-based extractant, an oxime-based extractant, etc. can be used. Specific examples of the phosphoric acid ester-based extractant can include bis(2-ethylhexyl) phosphate (D2EHPA), etc. In addition, specific examples of the oxime-based extractant can include 2-hydroxy-5-nonylacetophenone oxime (LIX84), 5-dodecylsalicylaldehyde oxime (LIX860), 5-nonylsalicylaldehyde oxime (ACORGAM5640), etc. In addition, the first extraction solution can use a solution obtained by mixing and diluting these extractants.

[0085] In addition, in the Mn extraction process, a back-extraction treatment can be performed on the extracted Mn solution (the first extraction solution containing Mn). In this back-extraction treatment, first, the Mn solution (organic phase) and the acidic aqueous solution are stirred and mixed. Then, it is left to stand until the two solutions are separated. Thus, an aqueous Mn solution with Mn dissolved in the acidic aqueous solution can be obtained. It should be noted that as the acidic aqueous solution used in the back-extraction treatment, sulfuric acid, hydrochloric acid, etc. (especially sulfuric acid) can be cited.

[0086] (c) Co extraction process

[0087] In the Co extraction process, Co is extracted from the acid leachate. Specifically, in this process, an organic solvent (the second extraction solution) with high extractability for Co and low extractability for Li, Al, Cu, and Ni can be added to the acid leachate. Thus, while separating Co from the acid leachate, a Co solution with Co dissolved in the second extraction solution can be obtained. It should be noted that specific examples of the second extraction solution can include phosphonic acid esters such as bis(2-ethylhexyl) 2-ethylhexylphosphonate (PC-88A), etc. In addition, a back-extraction treatment can be performed on the extracted Co solution (the second extraction solution containing Co). Thus, an aqueous Co solution can be obtained.

[0088] (d) Ni extraction process

[0089] In the Ni extraction process, Ni is extracted from the acid leachate. Specifically, in this process, an organic solvent (the third extraction solution) with high extractability for Ni and low extractability for Li, Al, and Cu can be added to the acid leachate. Thereby, while separating Ni from the acid leachate, a Ni solution in which Ni is dissolved in the third extraction solution can be obtained. It should be noted that as a specific example of the third extraction solution, carboxylic acid-based extractants such as neodecanoic acid and naphthenic acid can be cited. In addition, a back-extraction treatment can be performed on the extracted Ni solution (the third extraction solution containing Ni). Thereby, an aqueous Ni solution can be obtained.

[0090] (e) Li separation process

[0091] In the case where the above-mentioned Mn extraction process, Co extraction process, Ni extraction process, etc. have been carried out, since Ni, Co, Mn, etc. have been removed from the acid leachate, among the metal components in the acid leachate, Li, Al, and Cu become the main components. In the Li separation process, Cu and Al are removed from this acid leachate. It should be noted that the means for removing Cu and Al are not particularly limited, and conventionally known means such as solvent extraction method and ion exchange method can be appropriately adopted.

[0092] As described above, the constituent metals of the positive electrode active material can be separated from the acid leachate and recovered, and Li and Al can also be recovered. These recovered metals can be used as materials for lithium-ion secondary batteries according to known methods.

[0093] For example, the constituent metals of the recovered positive electrode active material can be used in the manufacture of the positive electrode active material according to known methods. Specifically, for example, by performing the following crystallization process and firing process using the constituent metals of the recovered positive electrode active material, the positive electrode active material can be manufactured.

[0094] (A) Crystallization process

[0095] In the crystallization process, a precursor of the positive electrode active material is manufactured using the constituent metals of the positive electrode active material. The precursor of the positive electrode active material can typically be a hydroxide or a carbonate. This crystallization process can be carried out according to known methods. For example, when manufacturing a lithium nickel cobalt manganese composite oxide as the positive electrode active material, in this crystallization process, a mixed solution in which a Co solution, a Ni solution, and a Mn solution are mixed is prepared. Then, the pH of this mixed solution is controlled to be alkaline. Thereby, crystals of nickel cobalt manganese composite hydroxide (NCM precursor) are precipitated. It should be noted that in the preparation of the mixed solution, the respective mixing ratios of the Co solution, the Ni solution, and the Mn solution can be changed as needed. Moreover, in the adjustment of the pH, the mixed solution can be dropped into the reaction tank together with an alkali solution (ammonia water, sodium hydroxide aqueous solution).

[0096] (B) Firing process

[0097] In the firing process, a precursor of a positive electrode active material and a lithium source are mixed and fired. This firing process can be carried out according to a known method. Specifically, for example, in the case of manufacturing a lithium nickel cobalt manganese composite oxide as the positive electrode active material, the NCM precursor obtained through the above is mixed with a Li compound (such as lithium carbonate, etc.) and fired. The Li compound is preferably a compound obtained by using the Li recovered in the metal recovery process S106, but is not limited thereto. Through this firing, the positive electrode active material of the lithium ion secondary battery (i.e., a lithium transition metal composite oxide) can be manufactured.

[0098] Using the obtained positive electrode active material, a lithium ion secondary battery can be manufactured according to a known method.

[0099] As described above, the method for recycling a lithium ion secondary battery according to the present embodiment has been described. According to the method for recycling a lithium ion secondary battery according to the present embodiment, since the positive electrode active material is refined, the reduction in the particle size and / or the increase in the surface area of the positive electrode active material contribute to improving the implementation efficiency of the subsequent processes (i.e., the processes for recycling) as described above.

[0100] 3. Other Embodiments

[0101] As described above, one embodiment of the method for recycling a lithium ion secondary battery according to the present disclosure has been described. It should be noted that the method for recycling a lithium ion secondary battery according to the present disclosure is not limited to the above embodiment, and includes other embodiments in which various configurations are changed.

[0102] For example, in the recycling method of the above embodiment, after performing the active material disintegration process S102, the roasting process S103, the black substance recovery process S104, the acid leaching process S105, and the metal recovery process S106 are performed. However, the above embodiment is not intended to limit the processes after performing the active material disintegration process S102. That is, in the method for recycling a lithium ion secondary battery according to the present disclosure, the processes after the active material disintegration process S102 can be added, deleted, or changed as needed.

[0103] For example, after performing the active material disintegration process S102, the lithium ion secondary battery is disassembled, the positive electrode is taken out, and the positive electrode is processed according to a known method, and the constituent metals of the positive electrode active material can be recovered. In this case, since the positive electrode active material is refined, the implementation efficiency is improved.

[0104] In addition, the various processes implemented in the metal recovery process S106 are not limited to the above neutralization precipitation process, Ni extraction process, Co extraction process, Mn extraction process, and Li separation process. Additionally, it is not necessary to perform all of these processes. For example, a battery using a lithium nickel manganese composite oxide as the positive electrode active material hardly contains cobalt (Co). In the case of using such a battery as the recovery target, the Co extraction process can be omitted. As described above, the processes after the active material disintegration process S102 can be appropriately changed according to the constituent elements of the recovery target (battery), and are not limited to specific processes.

[0105] (1) Regarding the recovery target

[0106] The structure of the lithium ion secondary battery used in the recycling method of the present disclosure is not limited to Figure 2 and Figure 3 the lithium ion secondary battery 1 shown. For example, in the above-described embodiment, an aluminum box-shaped case is used as the exterior body. However, the shape and material of the exterior body are not limited thereto. For example, the exterior body can be a cylindrical case. For example, the exterior body can be made of resin. For example, the exterior body can be a laminated exterior body. The laminated exterior body is formed by opposing two laminated sheets with the electrode body sandwiched therebetween and fusing the outer peripheral portions of the pair of laminated sheets.

[0107] [Test example]

[0108] Hereinafter, test examples related to the recycling method of the lithium ion secondary battery of the present disclosure will be described. It should be noted that the content of the test examples described below does not intentionally limit the recycling method of the lithium ion secondary battery of the present disclosure.

[0109] Preparation of test battery

[0110] In this test, a prescribed test battery was prepared. Hereinafter, the materials of the test battery used in this test will be described. In the test battery of this test, a lithium nickel cobalt manganese composite oxide (LiNi 1 / 3 Co 1 / 3Mn 1 / 3 O2) was used as the positive electrode active material. An aluminum foil was used for the positive electrode core. On the other hand, graphite was used as the negative electrode active material. A copper foil was used for the negative electrode core. Moreover, a separator having a three-layer structure of PP / PE / PE was used. In addition, an aluminum square case was used as the exterior body. That is, the main components of the test battery in this test are Li, Ni, Co, Mn, Cu, Al, and C. Additionally, the voltage of the prepared test battery was 3.2V.

[0111] 2. Implementation of charge and discharge

[0112] Regarding the charge and discharge treatment shown in Table 1, it was carried out using a thermostatic bath and a charger. Specifically, in Example 1, in the first treatment, the test battery was placed in a thermostatic bath at -30°C, and 1000 charge and discharge cycles of the amplitude (C) and pulse width (seconds) shown in Table 1 were performed (that is, 100C charging for 0.1 second and 100C discharging for 0.1 second were repeated 1000 times). In the second treatment, the test battery was placed at room temperature, and constant current charging to 3.2V at a current value of 0.01C and constant current discharging to 1V at a current value of 0.01C were repeated 10 times. It should be noted that in the case of a voltage of 3.2V, since the negative electrode potential is 0.5V (vs Li + / Li), the positive electrode potential based on lithium becomes 3.7V (vsLi + / Li). Regarding Examples 2 to 7, except that the treatment conditions were changed to the conditions shown in Table 1, the same treatment as in Example 1 was carried out. In Comparative Example 1, the cut-off current was set to 0.1C, and constant current - constant voltage (CC - CV) discharge to 0V was performed. In Comparative Example 2, constant current (CC) discharge of 5C for 0.02 seconds was performed. In Comparative Example 3, after the same pulse charge and discharge as in the first treatment of Example 1, the same constant current - constant voltage discharge as in the first treatment of Comparative Example 1 was performed.

[0113] 3. Implementation of subsequent processes

[0114] Next, the test battery after the above treatment was heated (calcined) in an electric furnace at 800°C. Then, the outer package was broken. The black substance was recovered by sieving the broken material, and its weight was measured. The recovery rate (%) of the black substance was calculated according to (weight of the recovered black substance / designed weight) × 100. The results are shown in Table 1.

[0115] 100 g of the black substance was weighed and subjected to acid leaching by immersion in sulfuric acid. As an index of the dissolution rate, the time when the metal components disappeared was measured by visual observation. The results are shown in Table 1.

[0116] [Table 1]

[0117]

[0118] In Table 1, the first treatment (i.e., pulse charge and discharge) of Examples 1 to 7 and Comparative Example 3 was the charge and discharge condition for lithium precipitation on the negative electrode. In addition, the second treatment of Examples 1 to 7 was the charge and discharge condition for the disintegration of the positive electrode active material. As shown in the results of Table 1, it can be seen that when the test battery is pulse charged and discharged in a low-temperature environment to precipitate Li on the negative electrode and the test battery is repeatedly charged and discharged within the range where the positive electrode is in a low potential region to cause the disintegration of the positive electrode active material (i.e., Examples 1 to 7), the dissolution rate of the black substance increases. In addition, it can also be seen that the recovery rate of the black substance also increases.

[0119] From the above, it can be seen that the regeneration method of the lithium-ion secondary battery according to the present disclosure can improve the implementation efficiency.

[0120] The specific examples of the present disclosure have been described in detail above, but these are only examples and do not limit the scope of the claims. The technology described in the scope of the claims includes technologies that are variously modified and changed from the above-described specific examples.

[0121] That is, the regeneration method of the lithium-ion secondary battery of the present disclosure is as follows in items [1] to [9].

[0122] [1] A regeneration method of a lithium-ion secondary battery, comprising:

[0123] A Li precipitation step of performing pulse charge and discharge on the lithium-ion secondary battery in a low-temperature environment to precipitate Li on the negative electrode;

[0124] An active material disintegration step of repeatedly charging and discharging the lithium-ion secondary battery within the range where the positive electrode is in a low potential region to cause the disintegration of the positive electrode active material.

[0125] [2] The regeneration method of the lithium-ion secondary battery according to item [1], wherein the low-temperature environment is a temperature environment of -30°C to 10°C.

[0126] [3] The regeneration method of the lithium-ion secondary battery according to item [1] or [2], wherein the current value during the pulse charge and discharge is 2.5C to 200C.

[0127] [4] The regeneration method of the lithium-ion secondary battery according to any one of items [1] to [3], wherein in the active material disintegration step, the lithium-ion secondary battery is repeatedly charged and discharged within the range where the potential of the positive electrode is 1.5V (vs Li + / Li) to 3.7V (vs Li + / Li).

[0128] [5]The method for recycling a lithium-ion secondary battery according to any one of items [1] to [4], wherein, in the active material disintegration step, charge and discharge of the lithium-ion secondary battery are performed for 5 cycles or more.

[0129] [6]The method for recycling a lithium-ion secondary battery according to any one of items [1] to [5], wherein the crystal structure of the positive electrode active material is a layered structure.

[0130] [7]The method for recycling a lithium-ion secondary battery according to any one of items [1] to [6], wherein the positive electrode active material is a lithium nickel cobalt manganese composite oxide.

[0131] [8]The method for recycling a lithium-ion secondary battery according to any one of items [1] to [7], wherein the negative electrode has graphite as the negative electrode active material.

[0132] [9]The method for recycling a lithium-ion secondary battery according to any one of items [1] to [8], further comprising:

[0133] A roasting step of heating the lithium-ion secondary battery that has undergone the active material disintegration step at a prescribed temperature;

[0134] A black substance recovery step of recovering a black substance containing the constituent metals of the positive electrode active material from the lithium-ion secondary battery that has undergone the roasting step;

[0135] An acid leaching step of immersing the obtained black substance in an acidic solution to obtain an acid leaching solution containing the constituent metals of the positive electrode active material;

[0136] A metal recovery step of separating and recovering the constituent metals of the positive electrode active material from the acid leaching solution.

Claims

1. A method for regenerating a lithium-ion secondary battery, comprising: Li precipitation step, performing pulse charge and discharge on the lithium ion secondary battery in a low temperature environment to precipitate Li in the negative electrode; and The active material disintegration step is to repeatedly charge and discharge the lithium ion secondary battery within a range where the positive electrode is in a low potential region so as to disintegrate the positive electrode active material.

2. The method for regenerating a lithium-ion secondary battery according to claim 1, wherein: The low temperature environment is a temperature environment of -30°C to 10°C.

3. The method for regenerating a lithium-ion secondary battery according to claim 1, wherein: The current value during the pulse charge and discharge is 2.5C to 200C.

4. The method for regenerating a lithium-ion secondary battery according to claim 1, wherein: In the active material disintegration step, the potential of the positive electrode is relative to Li / Li + The lithium ion secondary battery is repeatedly charged and discharged within a range of 1.5 V to 3.7 V relative to the reference electrode.

5. The method for regenerating a lithium-ion secondary battery according to claim 1, wherein: In the active material disintegration step, the lithium ion secondary battery is subjected to five or more cycles of charge and discharge.

6. The method for regenerating a lithium-ion secondary battery according to claim 1, wherein: The crystal structure of the positive electrode active material is a layered structure.

7. The method for regenerating a lithium-ion secondary battery according to claim 1, wherein: The positive electrode active material is lithium nickel cobalt manganese composite oxide.

8. The method for regenerating a lithium-ion secondary battery according to claim 1, wherein: The negative electrode contains graphite as a negative electrode active material.

9. The method for regenerating a lithium-ion secondary battery according to claim 1, wherein: Also includes: A calcination step of heating the lithium ion secondary battery after the active material disintegration step at a predetermined temperature; A black matter recovery step of recovering black matter containing a constituent metal of the positive electrode active material from the lithium ion secondary battery that has undergone the calcination step; an acid leaching step of immersing the obtained black substance in an acid solution to obtain an acid leaching solution containing the constituent metals of the positive electrode active material; and The metal recovery step is to separate and recover the constituent metals of the positive electrode active material from the acid leaching solution.

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