Regenerating method of lithium-ion secondary battery

Abstract

To provide a regenerating method of a lithium-ion secondary battery that can improve implementation efficiency.SOLUTION: A regenerating method of a lithium-ion secondary battery disclosed herein includes a Li deposition process in which a lithium-ion secondary battery is subjected to pulse charging and discharging in a low-temperature environment such that Li is deposited in a negative electrode, and an active material decaying process in which the lithium-ion secondary battery is repeatedly charged and discharged within a range in which the positive electrode is in a low potential region such that the positive electrode active material decays.SELECTED DRAWING: Figure 1

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. Various materials containing valuable metals such as Ni and Co are used in these lithium-ion secondary batteries. For example, 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 as the positive electrode active material. Also, aluminum or the like is used for the positive electrode core. On the other hand, a carbon material or the like is used for the negative electrode active material. And copper or the like is used for the negative electrode core. Further, aluminum or the like is also used for the battery case that houses these electrodes.

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

[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 discharged.

Prior Art Documents

Patent Document

[0005]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0006] However, as a result of the inventor's intensive studies, it has been found that in the prior art, there is a problem that the implementation efficiency of the regeneration process is insufficient, for example, it takes a long time to acid-leach metal components from the black mass.

[0007] The technology disclosed herein is made to solve the above problems, and an object thereof is to provide a method for regenerating a lithium-ion secondary battery that can improve the implementation efficiency.

Means for Solving the Problems

[0008] 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 so that Li precipitates at the negative electrode, and a step of repeating charge and discharge on the lithium-ion secondary battery within a range where the positive electrode is in a low potential region so that the positive electrode active material collapses.

[0009] According to such a configuration, it is possible to provide a method for regenerating a lithium-ion secondary battery that can improve the implementation efficiency.

Brief Description of the Drawings

[0010]

Figure 1

Figure 2

Figure 3

Embodiments for Carrying Out the Invention

[0011] Hereinafter, embodiments according to the present disclosure will be described with reference to the drawings. Matters not mentioned in this specification but 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 the relevant field. The present invention can be implemented based on the content disclosed in this specification and the common general knowledge in the relevant field. Also, in the following drawings, members and parts having the same function 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. Note that the numerical range expressed as "A to B" in this specification includes A and B.

[0012] In this specification, the "secondary battery" refers to a rechargeable power storage device. Also, in this specification, the "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 associated with lithium ions between the positive and negative electrodes.

[0013] Each step of the method for regenerating a lithium-ion secondary battery according to this embodiment, as an example of the method for regenerating a lithium-ion secondary battery according to the present disclosure, is shown in the flowchart of FIG. 1. The method for regenerating a lithium-ion secondary battery according to this embodiment includes, as essential steps, an Li precipitation step S101 of performing pulse charge and discharge on the lithium-ion secondary battery in a low-temperature environment so that Li precipitates at the negative electrode, and 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 so that the positive electrode active material disintegrates.

[0014] In the example shown in FIG. 1, the method for recycling a lithium-ion secondary battery according to the present embodiment further includes, as optional steps, a roasting step S103 of heating the lithium-ion secondary battery that has undergone the active material disintegration step S102 at a predetermined temperature, a black mass recovery step S104 of recovering the black mass 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 mass in an acid solution to obtain an acid leachate 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 leachate.

[0015] That is, the Li precipitation step S101 and the active material disintegration step S102 can also 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 the present 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 carried out.

[0016] The method for recycling a lithium-ion secondary battery according to the present embodiment mainly targets material recycling. The recycling method according to the present embodiment is typically used to obtain raw materials for the positive electrode active material by recovering valuable metals such as transition metals (e.g., Ni, Co, Mn) from the lithium-ion secondary battery, and can also be used to obtain raw materials for other constituent members of the lithium-ion secondary battery. However, the content of recycling the lithium-ion secondary battery is not limited to this. First, a specific example of the lithium-ion secondary battery used in the recycling method according to the present embodiment will be described.

[0017] 1. Lithium-Ion Secondary Battery FIG. 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 the present embodiment. FIG. 3 is a perspective view schematically showing the electrode body of the lithium-ion secondary battery shown in FIG. 2. As shown in FIG. 2, the lithium-ion secondary battery 1 includes an exterior body 10, an electrode body 20, and an electrolyte (not shown).

[0018] (1) Outer casing The outer casing is not particularly limited as long as it is a container for housing the electrode body and the electrolyte. For example, the outer casing 10 shown in FIG. 2 is a box-shaped case. For this box-shaped outer casing 10, for example, a metal material (such as aluminum (Al)) having a certain strength is used. As shown in FIG. 2, a positive electrode terminal 12 and a negative electrode terminal 14 are attached to the outer casing 10. The positive electrode terminal 12 and the negative electrode terminal 14 are connected to the electrode body 20 inside the outer casing 10. Specifically, the positive electrode terminal 12 is connected to the positive electrode plate 30 (see FIG. 3) of the electrode body 20. Aluminum (Al) or the like is used for this positive electrode terminal 12. On the other hand, the negative electrode terminal 14 is connected to the negative electrode plate 40 of the electrode body 20. Copper (Cu) or the like is used for this negative electrode terminal 14.

[0019] Furthermore, a liquid injection hole 16 is formed in the outer casing 10 shown in FIG. 2. This liquid injection hole 16 is an opening that communicates the inside and outside of the outer casing 10. In the manufacture of the lithium ion secondary battery 1, the inside of the outer casing 10 is filled with an electrolyte through this liquid injection hole 16. Then, the liquid injection hole 16 is sealed with a sealing plug 17 after the filling of the electrolyte.

[0020] (2) Electrode body The electrode body 20 is a power generation element of the lithium ion secondary battery 1. As shown in FIG. 3, the electrode body 20 includes a positive electrode plate 30, a negative electrode plate 40, and a separator 50. Note that the electrode body 20 shown in FIG. 3 is a wound electrode body. This wound electrode body is obtained 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. Note that the structure of the electrode body 20 is not limited to the wound electrode body, and other conventionally known structures (such as a laminated electrode body) may be used.

[0021] 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. Aluminum (Al) or the like is used for the positive electrode core 32. 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). Examples of such positive electrode active materials include 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. Further, other examples of the positive electrode active material include lithium transition metal phosphate compounds such as lithium iron phosphate, lithium manganese phosphate, and lithium manganese iron phosphate. Examples of the conductive material include carbon materials such as acetylene black and graphite. Examples of the binder include resin materials such as polyvinylidene fluoride (PVdF).

[0022] 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.

[0023] On one 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. Copper (Cu) or the like is used for the negative electrode core 42. Further, 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. Examples of the negative electrode active material include graphite. The graphite may be natural graphite or artificial graphite, or may be amorphous carbon-coated graphite in which the graphite is coated with an amorphous carbon material. Another example of the negative electrode active material includes other carbon materials such as hard carbon and soft carbon. Still another example of the negative electrode active material includes lithium titanate (LTO), silicon carbide (SiC), a composite containing carbon and silicon, silicon oxide (SiO X ). Also, as the binder, styrene-butadiene rubber (SBR) or the like is used. As the thickener, carboxymethyl cellulose (CMC) or the like is used.

[0024] The separator 50 is an insulating sheet interposed between the positive electrode plate 30 and the negative electrode plate 40. For this separator 50, resin materials such as polyethylene (PE), polypropylene (PP), polyester, cellulose, and polyamide are used, for example. Further, a heat-resistant layer containing an inorganic filler may be formed on the surface of the separator 50. Examples of such inorganic fillers include inorganic oxides such as aluminum oxide, magnesium oxide, silicon oxide, and titanium oxide, nitrides such as aluminum nitride and silicon nitride, metal hydroxides such as calcium hydroxide, magnesium hydroxide, and aluminum hydroxide, and clay minerals such as mica, talc, boehmite, zeolite, apatite, and kaolin.

[0025] (3) Electrolyte In this lithium-ion secondary battery 1, an electrolyte exists 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. Note that the form of the electrolyte is not limited to the technology disclosed herein, and a conventionally known form can be adopted without particular limitation. Examples of such forms of the electrolyte include non-aqueous electrolytes, gel electrolytes, and solid electrolytes.

[0026] The lithium-ion secondary battery 1 is preferably used for in-vehicle applications (i.e., as a driving power source for vehicles such as battery electric vehicles (BEVs), hybrid electric vehicles (HEVs), plug-in hybrid electric vehicles (PHEVs), etc.), but is not limited thereto. The lithium-ion secondary battery 1 may also be used as a power source for electronic devices or the like.

[0027] 2. Method for Recycling Lithium-Ion Secondary Batteries Hereinafter, each step of the method for recycling lithium-ion secondary batteries according to the present embodiment will be described in detail. As shown in FIG. 1, the lithium-ion secondary battery according to the present embodiment includes a Li precipitation step S101 and an active material disintegration step S102 as essential steps, and a baking step S103, a black mass recovery step S104, an acid leaching step S105, and a metal recovery step S106 as optional steps.

[0028] Thus, in the recycling method according to 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 refers to the refinement of the particles of the positive electrode active material due to cracking or the like (i.e., the particle size (specifically, the median diameter D50 measured by the laser diffraction scattering method) becomes smaller).

[0029] Here, when the lithium-ion secondary battery is charged and discharged in the low potential region of the positive electrode, the crystallite size changes due to the insertion and desorption of Li into the positive electrode active material. Therefore, by repeating the charge and discharge in the low potential region of the positive electrode, the change in the crystallite size can be utilized to disintegrate the crystal structure of the positive electrode active material and cause cracking or the like of the particles.

[0030] However, when a lithium-ion secondary battery is used over a long period of time, Li ions released from the positive electrode active material are immobilized on the negative electrode active material or the surface of the negative electrode, resulting in a decrease in the number of ions re-stored in the positive electrode active material. As a result, the potential of the positive electrode active material cannot return to a low state. Consequently, when attempting to lower the battery voltage, in order to balance by increasing the negative electrode potential, the low potential region of the positive electrode cannot be fully utilized for charge and discharge.

[0031] Therefore, in the regeneration method according to this embodiment, first, Li is 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 metallic lithium has a lower potential than the negative electrode active material, if this deposited Li is made to function as the negative electrode and an ion exchange is performed with the positive electrode, it becomes possible to charge and discharge the positive electrode in the low potential region.

[0032] In a lithium-ion secondary battery, Li deposition on the negative electrode is usually avoided from the viewpoints of capacity reduction, short circuit due to dendrite growth of metallic lithium, etc. Nevertheless, for the above reasons, in the regeneration method according to this embodiment, the Li deposition step is performed first.

[0033] (1) Li deposition step S101 The lithium-ion secondary battery used in the Li deposition step S101 is preferably a used lithium-ion secondary battery, but is not particularly limited. It may also be an unused lithium-ion secondary battery that was regarded as a defective product during manufacturing and could not be shipped. This can reduce the environmental burden while manufacturing the materials used in the lithium-ion secondary battery.

[0034] In the Li deposition step S101, the lithium-ion secondary battery is subjected to pulse charge and discharge in a low-temperature environment. Here, the deposition conditions of Li strictly vary depending on the battery design. Therefore, the deposition conditions of Li can be appropriately set according to the battery design.

[0035] Here, an amount of Li sufficient to cause the function as the negative electrode is deposited on the negative electrode. Li is more likely to be deposited at a lower temperature. Therefore, for example, when pulse charge and discharge are performed at room temperature (that is, about 25°C ± 10°C), a sufficient amount of Li cannot be deposited. For this reason, in the regeneration method according to this embodiment, pulse charging is performed in a low-temperature environment, whereby a sufficient amount of Li can be deposited.

[0036] As the temperature in this low-temperature environment (that is, the temperature of pulse charge and discharge), 10°C or lower is preferable, 5°C or lower is more preferable, and 0°C or lower is even more preferable. On the other hand, the temperature in the low-temperature environment is not particularly limited, but from the viewpoints of ease of obtaining a low temperature, energy consumption for lowering the temperature, etc., it is preferably -30°C or higher. Therefore, the low-temperature environment is preferably a temperature environment of -30°C to 10°C, more preferably a temperature environment of -30°C to 5°C, and even more preferably a temperature environment where the low-temperature environment is -30°C to 0°C.

[0037] Also, in order to deposit metallic Li, pulse charge and discharge are adopted as the charge and discharge. Here, the higher the charge and discharge rate, the easier it is for metallic Li to be deposited. Therefore, the current value (that is, the current amplitude) during pulse charge and discharge is not particularly limited as long as Li is deposited on the negative electrode. For example, it is 2.5C to 200C, preferably 3C to 150C, and even more preferably 5C to 100C. Note that 1C means the current value that can charge the battery capacity (Ah) predicted from the theoretical capacity of the positive electrode in 1 hour.

[0038] In pulse charge and discharge, the switching time of charge and discharge (that is, the pulse width) is not particularly limited as long as Li is deposited on the negative electrode. For example, it is 0.01 second to 20 seconds, preferably 0.1 second to 10 seconds.

[0039] The number of cycles in pulse charge and discharge is not particularly limited as long as Li is deposited on the negative electrode. For example, it is 50 cycles or more, preferably 100 cycles or more, more preferably 500 cycles or more, still more preferably 800 cycles or more, and particularly preferably 1000 cycles or more. Also, the number of cycles in pulse charge and discharge may be 3000 cycles or less, may be 2000 cycles or less, and may be 1500 cycles or less.

[0040] The state of charge (SOC) of the lithium-ion secondary battery when performing pulse charge and discharge is not particularly limited as long as the above-mentioned pulse charge and discharge are possible. The SOC of the lithium-ion secondary battery may be within the range of 1% to 99%, may be within the range of 10% to 90%, may be within the range of 50% or less, and may be within the range of 30% or less.

[0041] The Li deposition step S101 can be performed, for example, by placing the lithium-ion secondary battery in a low-temperature thermostat, a low-temperature constant-temperature chamber, etc. and using a charging device such as a known charger.

[0042] (2) Active material disintegration step S102 In the active material disintegration step S102, a charge and discharge treatment different from that in the Li deposition step S101 is performed. In the active material disintegration step S102, within the range where the positive electrode is in the low potential region, the lithium-ion secondary battery is repeatedly charged and discharged to disintegrate the positive electrode active material.

[0043] Since the charge and discharge conditions vary depending on the battery design, 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 3.7 V (vsLi + / Li) or less. Specifically, for example, the upper limit of the voltage during charging is set to the voltage at which the positive electrode potential is 3.7 V (vsLi + / Li). On the other hand, the lower limit of the voltage during discharge is such that the positive electrode potential is within the range of 1.5 V (vsLi + / Li) to 3.0 V (vsLi + / Li) (for example, 1.5 V (vsLi + / Li), preferably 2.5 V (vsLi +Let the voltage be such that it becomes (vs 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 within this range.

[0044] The charge-discharge rate is not particularly limited as long as the positive electrode active material disintegrates. Since the positive electrode resistance is high, the charge-discharge rate is usually very low. The charge-discharge current value is, for example, 0.001 C to 0.1 C, preferably 0.005 C to 0.05 C, and more preferably 0.05 to 0.02 C.

[0045] By repeatedly charging and discharging in the low potential region of the positive electrode as described above, the positive electrode active material can be disintegrated by utilizing the change in the crystallite size due to the insertion and desorption of Li into and from the positive electrode active material. The number of charge-discharge cycles is not particularly limited as long as the positive electrode active material disintegrates. The disintegration of the positive electrode active material can be caused by charge-discharge cycles of about 5 cycles. Therefore, the number of charge-discharge cycles is, for example, 5 cycles or more, preferably 7 cycles or more, and more preferably 10 cycles or more.

[0046] The temperature condition of the active material disintegration step S102 is not particularly limited. The active material disintegration step S102 may be performed at room temperature (for example, 25 °C ± 10 °C).

[0047] The active material disintegration step S102 can be performed using a charging device such as a known charger.

[0048] In addition, 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 by 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 suitable, and lithium nickel cobalt manganese composite oxide is particularly suitable. Also, the negative electrode active material may be graphite.

[0049] By performing the above lithium 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 decrease in the particle size and / or the increase in the surface area of the positive electrode active material accompanying the refinement contribute to improving the implementation efficiency of the subsequent steps (i.e., the steps for regeneration). For example, when performing the step of acid leaching the metal component from the black mass, the dissolution rate of the metal component increases, so the implementation efficiency of this step is improved. In addition, as the positive electrode active material is refined, the separation between the positive electrode active material layer and the positive electrode core becomes likely to occur, and the recovery amount and recovery efficiency of the black mass are improved.

[0050] After the lithium precipitation step S101 and the active material disintegration step S102, according to the material to be regenerated, known steps can be appropriately selected and implemented to regenerate the lithium-ion secondary battery. In the example shown in FIG. 1, a roasting step S103, a black mass recovery step S104, an acid leaching step S105, and a metal recovery step S106 are performed.

[0051] (3) Roasting step S103 In the roasting step S103, the lithium-ion secondary battery that has undergone the above lithium precipitation step S101 and active material disintegration step S102 (i.e., the lithium-ion secondary battery in which the positive electrode active material has been disintegrated) is heated at a predetermined temperature. Thereby, the liquid components (e.g., electrolyte solution, etc.) in the lithium-ion secondary battery can be removed, and the resin components (e.g., binder, separator, etc.) can be carbonized. In addition, by performing the roasting step S103, the function as a battery can be stopped. Thereby, the subsequent steps can be safely implemented.

[0052] The roasting step S103 can be carried out according to a known method. Here, when the heating temperature in the roasting step S103 is increased, the transfer of oxygen elements from the oxide of valuable metals (e.g., transition metal composite oxides, etc.) to the carbon material (e.g., negative electrode active material, etc.) is likely to occur. Thereby, the valuable metals can be reduced to the metallic state. Since the positive electrode active material is refined by the active material disintegration step S102, the valuable metals in this metallic state are also refined. Therefore, in the acid leaching step S105 described later, the valuable metals in this metallic state can be dissolved at a high dissolution rate, and the implementation efficiency of the regeneration method is further improved.

[0053] From the viewpoint of efficiently reducing valuable metals, the heating temperature in the roasting step S103 is preferably 400 °C or higher, more preferably 500 °C or higher, still more preferably 600 °C or higher, and particularly preferably 700 °C or higher.

[0054] On the other hand, from the viewpoint of reducing valuable metals, the upper limit of the heating temperature is not particularly limited. The heating temperature may be 1500 °C or lower, 1400 °C or lower, or 1300 °C or lower. In consideration of the cost required for temperature increase, 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.

[0055] Also, from the viewpoint 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% by volume or less, preferably 3% by volume or less, more preferably 1% by volume or less, and particularly preferably 0.1% by volume or less). Therefore, the roasting step S103 is preferably carried out in an inert atmosphere such as argon or nitrogen.

[0056] (4) Black mass recovery step S104 In the black mass recovery step S104, black mass is recovered from the lithium-ion secondary battery that has undergone the roasting step S103. Black mass is a powder containing the constituent metals of the positive electrode active material, and is usually black, so this powder is called black mass. The black mass recovery step S104 can be performed according to a known method (for example, recovery of powder by pulverization and sieving of a lithium-ion secondary battery).

[0057] For example, in the lithium-ion secondary battery 1 shown in FIG. 2, the electrode body 20 is housed inside the case 10. Therefore, first, the case 10 is crushed, and then the internal electrode body 20 is further finely crushed. The obtained solid content is sieved to remove the case 10, the positive electrode core 32, and the negative electrode core 42. Thereby, a powder containing the constituent metals of the positive electrode active material (that is, black mass) can be recovered. In this way, by crushing the case 10 and the electrode body 20, it becomes easier to remove the case 10, the positive electrode core 32, and the negative electrode core 42, the content of impurities (Al, Cu, etc.) in the black mass can be easily reduced, and the recovery efficiency of valuable metals (Li, Co, Ni, Mn, etc.) can be improved. In the recycling method according to the present embodiment, by making the positive electrode active material finer in the active material disintegration step S102, the valuable metals in the metallic state generated in the roasting step S103 are also made finer. Therefore, the sieving efficiency is improved. As a result, in the recycling method according to the present embodiment, the implementation efficiency is improved. Further, since the positive electrode active material is made finer, the positive electrode active material layer is likely to peel off from the positive electrode core, and for this reason, the recovery amount and recovery efficiency of the black mass are also improved.

[0058] Note that in the black mass recovery step S104, impurities such as Al and Cu may not be completely separated from the black mass. Although it will be described in detail later, even if these impurities are contained in the black mass, the impurities can be removed by 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, it is also possible to omit the black mass recovery step S104.

[0059] (5) Acid Leaching Step S105 In the acid leaching step S105, the black mass obtained in the black mass recovery step S104 is immersed in an acid solution. As a result, an acid leaching solution in which metal components (such as Li, Ni, Co, Mn, Cu, Al, etc.) in the black mass are dissolved in the acid solution can be prepared. On the other hand, since carbon in the black mass does not dissolve in the acid solution, it precipitates as a residue. Thereby, carbon can be removed.

[0060] The acid leaching step S105 can be carried out according to a known method. As an example, the pH of the acid solution is preferably -1.5 to 1.5 (more preferably -0.5 to 0.5). Thereby, the metal components in the black mass can be preferably dissolved. Specific examples of the acid 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. Further, 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. The temperature of the acid 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 S60 can be shortened. The upper limit of the temperature of the acid solution is not particularly limited and may be 90°C or lower, 85°C or lower, or 80°C or lower.

[0061] In the recycling method according to the present embodiment, by miniaturizing the positive electrode active material in the active material disintegration step S102, the valuable metals in the metallic state generated in the roasting step S103 are also miniaturized. Therefore, the specific surface area of the valuable metals is increased, and the acid leaching rate is extremely increased. For this reason, in the recycling method according to 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 miniaturized, the acid leaching rate is extremely increased.

[0062] (6) Metal Recovery Step S106 In the metal recovery step S106, the constituent metals of the positive electrode active material are separated and recovered. As described above, the acid leaching solution 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. Preferably, each of these metal components contained in the acid leaching solution is separated. Thereby, valuable metals can be recovered from the acid leaching solution. In addition, in the metal recovery step S106, a conventionally known treatment technique that can be used for metal extraction can be adopted without particular limitation.

[0063] For example, in the metal recovery step S106 in the present embodiment, depending on the type of metal to be recovered, a neutralization precipitation step, an Mn extraction step, a Co extraction step, an Ni extraction step, a Li separation step, etc. are carried out. Hereinafter, these steps will be specifically described.

[0064] (a) Neutralization precipitation step In the neutralization precipitation step, a neutralizing agent is added to the acid leaching solution obtained in the acid leaching step S106. As a result, a precipitate containing aluminum hydroxide (Al(OH)3) precipitates in the acid leaching solution. As a result, most of the Al in the acid leaching solution is removed, and Al can be recovered. 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 such an alkaline solution include an aqueous sodium hydroxide solution, calcium hydroxide, and ammonia. Also, in this step, it is preferable to filter the acid leaching solution to separate the precipitate. Thereby, Al(OH)3 can be efficiently removed from the acid leaching solution.

[0065] (b) Mn extraction step In the Mn extraction step, Mn is extracted from the acid leaching solution. For example, in this step, an organic solvent (first extraction solution) with high extractability for Mn and low extractability for Li, Al, Cu, Co, and Ni may be added to the acid leaching solution. Then, the acid leaching solution and the first extraction solution are stirred and suspended. As a result, Mn in the acid leaching solution dissolves into the first extraction solution. After that, it is left to stand until the two liquids separate. In this way, an Mn solution with Mn dissolved in the first extraction solution and an acid leaching solution from which Mn has been removed can be obtained. As the first extraction solution, a phosphoric acid ester extractant, an oxime extractant, etc. can be used. Specific examples of the phosphoric acid ester extractant include di-2-ethylhexyl phosphoric acid (D2EHPA), etc. Specific examples of the oxime extractant include 2-hydroxy-5-nonylacetophenone oxime (LIX84), 5-dodecylsalicylaldoxime (LIX860), 5-nonylsalicylaldoxime (ACORGA M5640), etc. Also, as the first extraction solution, a mixture and dilution of these extractants may be used.

[0066] Also, in the Mn extraction step, a back-extraction treatment may 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 an acidic aqueous solution are stirred and mixed. Then, it is left to stand until the two liquids separate. In this way, an aqueous Mn solution with Mn dissolved in the acidic aqueous solution can be obtained. As the acidic aqueous solution used in the back-extraction treatment, sulfuric acid, hydrochloric acid, etc. (especially sulfuric acid) can be mentioned.

[0067] (c) Co extraction step In the Co extraction step, Co is extracted from the acid leaching solution. Specifically, in this step, an organic solvent (second extraction solution) with high extractability for Co and low extractability for Li, Al, Cu, and Ni may be added to the acid leaching solution. Thereby, Co is separated from the acid leaching solution, and a Co solution in which Co is dissolved in the second extraction solution can be obtained. Specific examples of the second extraction solution include phosphonic acid esters such as 2-ethylhexyl phosphonic acid 2-ethylhexyl (PC-88A). Further, a back-extraction treatment may also be performed on the Co solution (second extraction solution containing Co) after extraction. Thereby, an aqueous Co solution can be obtained.

[0068] (d) Ni extraction step In the Ni extraction step, Ni is extracted from the acid leaching solution. Specifically, in this step, an organic solvent (third extraction solution) with high extractability for Ni and low extractability for Li, Al, and Cu is added to the acid leaching solution. Thereby, Ni is separated from the acid leaching solution, and a Ni solution in which Ni is dissolved in the third extraction solution can be obtained. Specific examples of the third extraction solution include carboxylic acid-based extractants such as neodecanoic acid and naphthenic acid. Further, a back-extraction treatment may also be performed on the Ni solution (third extraction solution containing Ni) after extraction. Thereby, an aqueous Ni solution can be obtained.

[0069] (e) Li separation step When the above Mn extraction step, Co extraction step, Ni extraction step, etc. are performed, since Ni, Co, Mn, etc. are removed from the acid leaching solution, the main metal components in the acid leaching solution are Li, Al, and Cu. In the Li separation step, Cu and Al are removed from this acid leaching solution. The means for removing Cu and Al is not particularly limited, and conventionally known means such as solvent extraction and ion exchange can be appropriately adopted.

[0070] As described above, the constituent metals of the positive electrode active material can be separated and recovered from the acid leaching solution, 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.

[0071] For example, the constituent metals of the recovered positive electrode active material can be used for the production of the positive electrode active material according to known methods. Specifically, for example, by performing the following crystallization step and firing step using the constituent metals of the recovered positive electrode active material, the positive electrode active material can be produced.

[0072] (A) Crystallization step In the crystallization step, a precursor of the positive electrode active material is produced using the constituent metals of the positive electrode active material. The precursor of the positive electrode active material is typically a hydroxide and may be a carbonate. The crystallization step can be carried out according to known methods. For example, when producing a lithium nickel cobalt manganese composite oxide as the positive electrode active material, in this crystallization step, 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. As a result, crystals of nickel cobalt manganese composite hydroxide (NCM precursor) are precipitated. In the preparation of the mixed solution, the mixing ratio of each of the Co solution, the Ni solution, and the Mn solution may be changed as necessary. And in the adjustment of pH, it is preferable to drop the mixed solution into the reaction tank together with an alkaline solution (aqueous ammonia, aqueous sodium hydroxide solution).

[0073] (B) Firing step In the firing step, the precursor of the positive electrode active material and a lithium source are mixed and fired. The firing step can be carried out according to known methods. Specifically, for example, when producing a lithium nickel cobalt manganese composite oxide as the positive electrode active material, the NCM precursor obtained above and a Li compound (e.g., lithium carbonate, etc.) are mixed and fired. The Li compound is preferably obtained using the Li recovered in the metal recovery step S106, but is not limited thereto. By this firing, the positive electrode active material of the lithium ion secondary battery (that is, the lithium transition metal composite oxide) can be produced.

[0074] Using the obtained positive electrode active material, a lithium ion secondary battery can be produced according to known methods.

[0075] The above describes the method for regenerating a lithium-ion secondary battery according to the present embodiment. According to the method for regenerating a lithium-ion secondary battery according to the present embodiment, since the positive electrode active material is refined, a decrease in the particle size and / or an increase in the surface area of the positive electrode active material contribute to improving the implementation efficiency of the subsequent steps (i.e., the steps for regeneration) as described above.

[0076] 3. Other Embodiments The above describes one embodiment of the method for regenerating a lithium-ion secondary battery according to the present disclosure. Note that the method for regenerating a lithium-ion secondary battery according to the present disclosure is not limited to the above-described embodiment, and includes other embodiments in which various configurations are changed.

[0077] For example, in the regeneration method according to the above-described embodiment, after performing the active material disintegration step S102, the baking step S103, the black mass recovery step S104, the acid leaching step S105, and the metal recovery step S106 are performed. However, the above-described embodiment is not intended to limit the steps after performing the active material disintegration step S102. That is, in the method for regenerating a lithium-ion secondary battery according to the present disclosure, the steps after the active material disintegration step S102 can be added / deleted / changed as necessary.

[0078] For example, after performing the active material disintegration step S102, the lithium-ion secondary battery may be disassembled, the positive electrode may be taken out, and the positive electrode may be processed according to a known method to recover the constituent metals of the positive electrode active material. Also in this case, since the positive electrode active material is refined, the implementation efficiency is improved.

[0079] Moreover, the various processes carried out in the metal recovery step S106 are not limited to the neutralization precipitation step, Ni extraction step, Co extraction step, Mn extraction step, and Li separation step described above. Also, it is not necessary to perform all of these steps. For example, a battery using lithium nickel manganese composite oxide as the positive electrode active material contains almost no cobalt (Co). When such a battery is the object of recovery, the Co extraction step can be omitted. As described above, the steps after the active material disintegration step S102 can be appropriately changed according to the constituent elements of the object to be recovered (battery), and are not limited to specific steps.

[0080] (1) Regarding the object to be recovered The configuration of the lithium-ion secondary battery used in the recycling method according to the present disclosure is not limited to the lithium-ion secondary battery 1 shown in FIGS. 2 and 3. 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 may be a cylindrical case. For example, the exterior body may be made of resin. For example, the exterior body may be a laminated exterior body. This laminated exterior body is formed by opposing two laminated films with the electrode body sandwiched therebetween and welding the outer peripheral edge portions of the pair of laminated films.

[0081] [Test Example] Hereinafter, test examples regarding the recycling method of the lithium-ion secondary battery of the present disclosure will be described. Note that the content of the test examples described below is not intended to limit the recycling method of the lithium-ion secondary battery of the present disclosure.

[0082] 1. Preparation of test battery In this test, a predetermined 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, lithium nickel cobalt manganese composite oxide (LiNi 1 / 3 Co 1 / 3 Mn 1 / 3O2) was used. For the positive electrode core, aluminum foil was used. On the other hand, for the negative electrode active material, graphite was used. For the negative electrode core, copper foil was used. And for the separator, a separator with a three-layer structure of PP / PE / PE was used. Also, for the exterior body, a rectangular aluminum case was used. That is, the main components of the test battery in this test were Li, Ni, Co, Mn, Cu, Al, and C. Also, the voltage of the prepared test battery was 3.2V.

[0083] 2. Performing Charge and Discharge The processes related to charge and discharge shown in Table 1 were carried out using a thermostat and a charger. Specifically, in Example 1, in the first process, the test battery was placed in a thermostat at -30°C, and charge and discharge with the amplitude (C) and pulse width (seconds) shown in Table 1 were carried out for 1000 cycles (that is, charging at 100C for 0.1 seconds and discharging at 100C for 0.1 seconds were repeated 1000 times). In the second process, the test battery was placed at room temperature, and constant current charging up to 3.2V with a current value of 0.01C and constant current discharging up to 1V with a current value of 0.01C were repeated for 10 cycles. Note that in the case of a voltage of 3.2V, since the negative electrode potential is 0.5V (vsLi + / Li), the positive electrode potential based on lithium is 3.7V (vsLi + / Li). For Examples 2 to 7, the same processing as in Example 1 was carried out except that the processing conditions were changed to the conditions shown in Table 1. In Comparative Example 1, the cut-off current was set to 0.1C, and constant current - constant voltage (CC - CV) discharge was carried out until 0V. In Comparative Example 2, constant current (CC) discharge at 5C was carried out for 0.02 seconds. In Comparative Example 3, after performing the same pulse charge and discharge as in the first process of Example 1, the same constant current - constant voltage discharge as in the first process of Comparative Example 1 was carried out.

[0084] 3. Performing Post - processes Next, the test battery after the above processing was heated (calcined) in an electric furnace at 800°C. Then, the exterior body was crushed. The crushed material was sieved to recover the black mass, and its weight was measured. The recovery rate (%) of the black mass was calculated from (weight of the recovered black mass / designed weight) × 100. The results are shown in Table 1.

[0085] 100 g of black mass was weighed and acid leaching was performed by immersing it in sulfuric acid. As an index of the dissolution rate, the time until the metal component disappeared visually was measured. The results are shown in Table 1.

[0086] [Table 1]

[0087] In Table 1, the first treatment (i.e., pulse charge and discharge) of Examples 1 to 7 and Comparative Example 3 is the charge and discharge condition under which lithium is deposited on the negative electrode. Also, the second treatment of Examples 1 to 7 is the charge and discharge condition under which the positive electrode active material collapses. As shown by the results in Table 1, when pulse charge and discharge was performed on the test battery in a low-temperature environment so that Li was deposited on the negative electrode, and charge and discharge was repeated on the test battery within the range where the positive electrode was in the low potential region so that the positive electrode active material collapsed (i.e., Examples 1 to 7), it can be seen that the dissolution rate of the black mass is improved. Also, it can be seen that the recovery rate of the black mass is increased.

[0088] From the above, it can be seen that according to the method for regenerating a lithium-ion secondary battery of the present disclosure, the implementation efficiency can be improved.

[0089] As described above, specific examples of the present disclosure have been described in detail, but these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and changes of the specific examples illustrated above.

[0090] That is, the method for regenerating a lithium-ion secondary battery of the present disclosure is as follows in items [1] to [9]. [1] A lithium deposition step of performing pulse charge and discharge on a lithium-ion secondary battery in a low-temperature environment so that Li is deposited on the negative electrode, An active material collapse step of repeatedly charging and discharging the lithium-ion secondary battery within the range where the positive electrode is in a low potential region so that the positive electrode active material collapses, A method for regenerating a lithium-ion secondary battery, comprising: [2] The method for regenerating a lithium-ion secondary battery according to item [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 item [1] or [2], wherein the current value during the pulse charge and discharge is 2.5C to 200C. [4] In the active material disintegration step, the lithium-ion secondary battery is charged and discharged repeatedly within a range where the potential of the positive electrode is 1.5V (vsLi + / Li) to 3.7V (vsLi + / Li). The method for regenerating a lithium-ion secondary battery according to any one of items [1] to [3]. [5] The method for regenerating a lithium-ion secondary battery according to any one of items [1] to [4], wherein in the active material disintegration step, the lithium-ion secondary battery is charged and discharged 5 cycles or more. [6] The method for regenerating 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. [7] The method for regenerating 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. [8] The method for regenerating a lithium-ion secondary battery according to any one of items [1] to [7], wherein the negative electrode contains graphite as a negative electrode active material. [9] A roasting step of heating the lithium-ion secondary battery that has undergone the active material disintegration step at a predetermined temperature, and A black mass recovery step of recovering a black mass containing the constituent metals of the positive electrode active material from the lithium-ion secondary battery that has undergone the roasting step, and An acid leaching step of immersing the obtained black mass in an acid solution to obtain an acid leaching solution containing the constituent metals of the positive electrode active material, and A metal recovery step of separating and recovering the constituent metals of the positive electrode active material from the acid leaching solution. The method for regenerating a lithium-ion secondary battery according to any one of items [1] to [8], further including the above steps.

Description of Symbols

[0091] 1 Lithium-ion secondary battery 10 cases 12 positive electrode terminals 14 negative electrode terminals 20 electrode body 30 positive electrode plate 32 positive electrode core 34 positive electrode active material layer 40 negative electrode plate 42 negative electrode core 44 negative electrode active material layer 50 separator

Claims

1. A lithium-ion secondary battery, comprising: a Li deposition step of performing pulse charge and discharge in a low-temperature environment so that Li is deposited on the negative electrode; and an active material disintegration step of repeatedly charging and discharging the lithium-ion secondary battery within a range where the positive electrode is in a low potential region so that the positive electrode active material disintegrates; A method for regenerating a lithium-ion secondary battery, comprising the above steps.

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. In the active material disintegration step, the lithium ion secondary battery is charged and discharged within a range where the potential of the positive electrode is 1.5 V (vs Li ＋ / Li) to 3.7 V (vs Li ＋ / Li). The method for regenerating a lithium ion secondary battery according to claim 1.

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 charged and discharged 5 cycles or more.

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 a 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. A baking step of heating the lithium-ion secondary battery that has undergone the active material disintegration step at a predetermined temperature; A black mass recovery step of recovering black mass containing the constituent metals of the positive electrode active material from the lithium-ion secondary battery that has undergone the baking step; An acid leaching step of immersing the obtained black mass in an acid solution to obtain an acid leaching solution containing the constituent metals of the positive electrode active material; A metal recovery step of separating and recovering the constituent metals of the positive electrode active material from the acid leaching solution; The method for regenerating a lithium-ion secondary battery according to claim 1, further comprising the above steps.

Images