Method for deactivating lithium-ion rechargeable batteries

Abstract

A method for deactivating a lithium ion secondary battery, the method comprising (A) a step for opening the lithium ion secondary battery in an alkali water solution or (B) a step for opening the lithium ion secondary battery in water under an inert gas atmosphere or a reductive gas atmosphere. By using said method, it is possible to easily and safely deactivate waste lithium ion secondary batteries.

Description

Technical Field

[0001] The present invention relates to a method for deactivating a lithium ion secondary battery.

Background Art

[0002] In modern society, the demand for lithium ion secondary batteries is increasing, and the importance of efficient recycling of used lithium ion secondary batteries (waste lithium ion secondary batteries) is also increasing. However, lithium ion secondary batteries contain highly reactive lithium (Li), and accidents of ignition due to improper handling have been reported. In the past, hydrogen explosions have also occurred during the treatment of waste lithium ion secondary batteries in the United States. For these reasons, especially for large lithium ion secondary batteries used in electric vehicles and the like, "safe deactivation and disassembly" is an issue. At present, it is assumed that waste lithium ion secondary batteries are incinerated at high temperature or treated with high-temperature steam, but large-scale treatment equipment is required for detoxification of harmful gases generated by combustion, decomposition, evaporation, etc. of organic solvents in lithium ion secondary batteries. In addition, treatment plants equipped with such large-scale equipment are located away from urban areas, and when transporting large waste lithium ion secondary batteries to the treatment plant, it is necessary to transport them in special containers to ensure safety. <00000!17> Under such circumstances, as a method for deactivating waste lithium ion secondary batteries for recycling, for example, Patent Document 1 describes incinerating waste lithium ion secondary batteries after discharging. Further, Patent Document 2 describes mechanically dry-grinding lithium ion secondary batteries in an atmosphere such as argon or carbon dioxide.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

[0005] Currently, much research, as described in Patent Document 1, is based on the premise of deactivating lithium by high-temperature incineration. However, this requires high-temperature incineration equipment, which inevitably necessitates large-scale processing facilities, making it unsuitable for decentralized processing in urban areas. Furthermore, it presents the challenge of neutralizing harmful fluorine-containing gases generated by the combustion of organic solvents contained in the electrolyte of lithium-ion secondary batteries. In addition, in the method described in Patent Document 1, lithium and graphite are distributed into the slag phase and cannot be recovered. On the other hand, the method described in Patent Document 2 is extremely dangerous because, even in an atmosphere of argon, carbon dioxide, etc., dry pulverization causes waste lithium-ion secondary batteries to ignite violently and generate heat, making it unsuitable for deactivating large lithium-ion secondary batteries. Therefore, to prevent heat generation and the generation of harmful gases, Patent Document 3 describes a method of cutting or crushing lithium-ion secondary batteries in liquid water, alcohol, acid, or an inert gas, while Patent Document 4 describes a method of shredding in water. However, if a lithium-ion secondary battery is disconnected in water or acid without controlling the atmosphere, gas will be generated due to the hydrolysis of organic solvents such as carbonates contained in the electrolyte, posing a risk to the storage and transportation of the deactivated liquid.

[0006] The present invention aims to solve the above-mentioned problems and provides a simple and safe method for deactivating waste lithium-ion secondary batteries. [Means for solving the problem]

[0007] As a result of diligent research to solve the above problems, the inventors of the present invention have found that waste lithium-ion secondary batteries can be easily and safely deactivated by opening the lithium-ion secondary battery in an alkaline aqueous solution, or by opening the lithium-ion secondary battery in water under an inert gas atmosphere or a reducing gas atmosphere. Based on these findings, the inventors of the present invention have conducted further research and completed the present invention. That is, the present invention encompasses the following aspects.

[0008] Item 1. A method for deactivating a lithium-ion secondary battery, (A) A step of opening the lithium-ion secondary battery in an alkaline aqueous solution, or (B) The process of opening the lithium-ion secondary battery in water under an inert gas atmosphere or a reducing gas atmosphere. A method that includes [a certain feature].

[0009] Item 2. The method according to Item 1, wherein the amount of alkaline aqueous solution used in step (A) and the amount of water used in step (B) is 10 mL or more per 1 Wh of the capacity of the lithium-ion secondary battery.

[0010] Item 3. The method according to item 1 or 2, wherein step (A) is carried out under an inert gas atmosphere or a reducing gas atmosphere.

[0011] Item 4. The method according to any one of items 1 to 3, wherein the pH of the alkaline aqueous solution in step (A) is 10 to 14, and the pH of the water in step (B) is 6 to 14.

[0012] Item 5. The method according to any one of items 1 to 4, wherein the alkali compound used as the alkaline aqueous solution is at least one selected from the group consisting of calcium hydroxide, calcium oxide, magnesium hydroxide, magnesium oxide, sodium hydroxide, potassium hydroxide, and lithium hydroxide.

[0013] Item 6. The method according to any one of items 1 to 5, wherein in step (A), the alkaline aqueous solution is limewater.

[0014] Item 7. The method according to any one of Items 1 to 6, wherein the content of the alkali compound in the aqueous alkali solution is greater than the saturation concentration.

[0015] Item 8. The method according to any one of Items 1 to 7, wherein the step of opening the lithium ion secondary battery is a step of crushing or cutting the lithium ion secondary battery, making a hole penetrating the casing of the lithium ion secondary battery, or opening a part or all of the casing of the lithium ion secondary battery.

[0016] Item 9. The method according to any one of Items 1 to 8, wherein the steps (A) and (B) are carried out at 10 to 80°C.

[0017] Item 10. The method according to any one of Items 1 to 9, wherein the time of completion of inactivation is determined from the generation state of bubbles from the opening.

[0018] Item 11. A method for visualizing the inactivation state of a lithium ion secondary battery, comprising: (A) a step of opening the lithium ion secondary battery in an aqueous alkali solution, or (B) a step of opening the lithium ion secondary battery in water under an inert gas atmosphere or a reducing gas atmosphere and visualizing the inactivation state of the lithium ion secondary battery by generating bubbles from the opening.

[0019] Item 12. A method for separating and recovering a metal element from a lithium ion secondary battery, comprising: a step of pulverizing and physically separating the inactivated lithium ion secondary battery after inactivating the lithium ion secondary battery by the method according to any one of Items 1 to 11 is provided.

[0020] Item 13. The method according to Item 12, wherein at least one selected from the group consisting of lithium, nickel, and cobalt is recovered as a solid oxide, and copper and / or aluminum is recovered as a metal.

[0021] Item 14. (A1) A process of sorting the casing with the control board attached from the solid material of the deactivated lithium-ion secondary battery by size and recovering the aluminum. (A2) A step of recovering at least one selected from the group consisting of copper scraps, aluminum scraps, and separator pieces from the solid material remaining in step (A1) by sieving (1). The method according to item 12 or 13, comprising:

[0022] Item 15. After the step (A2), (A3) A step of recovering separator pieces from the solid material remaining in the above step (A2) by sieving (2), and (A4) A step to separate copper scrap and aluminum scrap from the solid material remaining in step (A3) above. The method according to item 14, comprising:

[0023] Item 16. After the step (A2), (B3) A step of filtering the suspension of the deactivated lithium-ion secondary battery to separate at least one selected from the group consisting of lithium, cobalt, nickel and manganese oxides, graphite powder, aluminum hydroxide and calcium fluoride. The method according to item 14, comprising:

[0024] Item 17. A lithium-ion secondary battery deactivation device used to deactivate lithium-ion secondary batteries in an alkaline aqueous solution or in water, A chamber in which an alkaline aqueous solution or water is stored, A mechanism disposed within the chamber and for opening the lithium-ion secondary battery placed inside the chamber. A lithium-ion secondary battery deactivation device equipped with the following features.

[0025] Item 18. A lid that can be opened and closed, which is placed on the chamber and isolates the enclosed space formed on the alkaline aqueous solution or water from the outside, A gas supply unit that supplies an inert gas or reducing gas to the enclosed space. A lithium-ion secondary battery deactivation device as described in item 17, further comprising the above.

[0026] Item 19. A vehicle equipped with a lithium-ion secondary battery deactivation device as described in Item 17 or 18.

[0027] Item 20. A method for recycling lithium-ion secondary batteries using the method described in any one of items 1 to 11. [Effects of the Invention]

[0028] According to the present invention, waste lithium-ion secondary batteries can be deactivated simply and safely. Therefore, the deactivated materials can be transported simply and safely, and the recycling of waste lithium-ion secondary batteries can be promoted. [Brief explanation of the drawing]

[0029] [Figure 1] This shows the typical configuration of a small lithium-ion secondary battery and the raw material costs of each component. [Figure 2] This document presents an example of a method for separating and recovering metallic elements from lithium-ion secondary batteries. [Figure 3] This shows an example of a vehicle capable of deactivating and separating / recovering individual elements of waste lithium-ion secondary batteries on-site (e.g., at an automobile dismantling plant or accident site). [Figure 4] A schematic diagram of the lithium-ion secondary battery deactivation device of the present invention is shown. (a) External view. (b) Plan view. (c) Cross-sectional view. [Figure 5] This photograph illustrates the meanings of "no pretreatment," "opening," and "cutting" in this embodiment. [Figure 6] Comparative Example 3 shows the results when a lithium-ion secondary battery is cut using the dry method. [Figure 7] Example 2 shows the results when a lithium-ion secondary battery was opened in limewater. [Figure 8] In Test Example 1, the results of analyzing the oxygen and hydrogen concentrations during the deactivation process using gas chromatography (GC) are shown. [Figure 9] In Test Example 1, a flowchart of the deactivation and elemental separation processes for lithium-ion secondary batteries is shown. The appearance of the separated samples is also shown. [Figure 10] In Test Example 1, a flowchart of the deactivation and elemental separation processes for lithium-ion secondary batteries is shown. The recovery rate of the separated samples is also shown. [Figure 11] In Test Example 2, the ultraviolet-visible absorption spectrum is shown when ethylene carbonate is added to deionized water. [Figure 12] Test Example 3 shows the corrosion behavior of iron balls in limewater, hydrofluoric acid, and NaCl aqueous solution. [Modes for carrying out the invention]

[0030] In this specification, when a numerical range is expressed as "A~B", it means A or greater and B or less. Furthermore, "contains" encompasses all of "contains," "consist essentially of," and "consist of."

[0031] 1. Method for deactivating lithium-ion secondary batteries First, Figure 1 shows the typical configuration of a small lithium-ion secondary battery and the raw material costs of each component. When the resin casing is removed from a typical lithium-ion secondary battery, a casing made of aluminum or the like, with a control board attached, is revealed. This casing contains the positive electrode active material, positive electrode current collector (aluminum foil), negative electrode active material, negative electrode current collector (copper foil), electrolyte, separator, insulating film, etc. Comparing the raw material costs of each component, the positive electrode active material accounts for approximately 79% of the total, and all of them contain lithium. In other words, considering the recycling efficiency from lithium-ion secondary batteries, it is preferable to recover lithium, and it is even more preferable to recover the metallic elements in the positive electrode active material, especially nickel and cobalt.

[0032] On the other hand, many studies on conventional methods for deactivating lithium-ion secondary batteries, such as Patent Document 1, have been based on the premise of deactivating lithium by high-temperature incineration. In this case, high-temperature incineration equipment is required, and the need for large-scale processing equipment is unavoidable, making it unsuitable for decentralized processing in urban areas. Furthermore, it is necessary to neutralize the harmful fluorine-containing gas produced by the combustion of organic solvents contained in the electrolyte of lithium-ion secondary batteries.

[0033] As described in Patent Document 1, the method of deactivating lithium by high-temperature incineration involves heating and melting the lithium-ion secondary battery in a high-temperature furnace, dissolving valuable materials into the molten alloy. After this, the alloy is acid-leached, and each element is separated by solvent extraction. However, in the method of Patent Document 1, lithium and graphite are distributed into the slag phase and cannot be recovered. Therefore, the lithium contained in the lithium-ion secondary battery cannot be recovered. In other words, conventional methods for deactivating lithium-ion secondary batteries cannot be considered efficient recycling methods.

[0034] In contrast, the method for deactivating a lithium-ion secondary battery according to the present invention is: (A) A step of opening the lithium-ion secondary battery in an alkaline aqueous solution, or (B) The process of opening the lithium-ion secondary battery in water under an inert gas atmosphere or a reducing gas atmosphere. It is equipped with.

[0035] Thus, in the method for deactivating lithium-ion secondary batteries of the present invention, it is possible to gently deactivate the lithium contained in the lithium-ion secondary battery by opening the lithium-ion secondary battery in neutral or alkaline water or aqueous solution. Moreover, the method for deactivating lithium-ion secondary batteries of the present invention is also useful in that it is possible to recover lithium, nickel and cobalt as solid oxides, and copper and aluminum as metals.

[0036] The present invention provides a method for deactivating lithium-ion secondary batteries that does not generate toxic gases, can be performed using relatively small equipment, and allows for the safe dismantling of lithium-ion secondary batteries.

[0037] Therefore, lithium-ion secondary batteries can be dismantled easily and safely at various locations in urban areas, such as automobile dismantling yards, and can be dismantled and transported easily and safely.

[0038] (1-1) Alkaline aqueous solution and water In step (A), the lithium-ion secondary battery is opened in an alkaline aqueous solution. In step (B), the lithium-ion secondary battery is opened in water under an inert gas atmosphere or a reducing gas atmosphere.

[0039] The alkaline compound used as the alkaline aqueous solution in step (A) is not particularly limited as long as it is a compound that exhibits alkalinity (especially pH 10-14) when dissolved in water. Examples include calcium hydroxide, calcium oxide, magnesium hydroxide, magnesium oxide, sodium hydroxide, potassium hydroxide, and lithium hydroxide. These alkaline compounds can be used individually or in combination of two or more.

[0040] If an alkaline aqueous solution is used in process (A), the alkaline compound content in the aqueous solution will be below the saturation concentration, as the alkaline compound will be consumed by the reaction during the deactivation process of the lithium-ion secondary battery. This will be explained in detail below.

[0041] For example, if the carbonate in a lithium-ion secondary battery is ethylene carbonate, the carbonate is hydrolyzed in water, triggering the following reaction.

[0042] [ka]

[0043] The carbon dioxide produced at this time reacts with the alkali compound and precipitates, thus accelerating the hydrolysis of the carbonate in the above equation. For example, if the alkali compound is calcium hydroxide, it reacts with carbon dioxide to form calcium carbonate as follows.

[0044] [ka]

[0045] Furthermore, in addition to the carbonate decomposition reaction described above, alkali compounds are also consumed in the LiPF6 decomposition reaction described later. Therefore, if the alkali compound content in the alkaline aqueous solution is below the saturation concentration, the alkali compounds will be consumed by the reactions during the deactivation treatment of lithium-ion secondary batteries, making it difficult for the decomposition reactions of carbonate and LiPF6 to proceed, and potentially preventing complete detoxification.

[0046] Therefore, in step (A), it is preferable to set the content of the alkaline compound in the alkaline aqueous solution to a level greater than the saturation concentration, thereby precipitating some of the alkaline compound. This allows the concentration of the alkaline compound to be replenished by dissolving from the precipitate into the alkaline aqueous solution, even if the alkaline compound is consumed by the reaction during the deactivation treatment of the lithium-ion secondary battery.

[0047] For example, when calcium hydroxide is used as the alkaline compound, only 0.17 g of calcium hydroxide dissolves in 100 mL of water at room temperature. However, it is preferable to include an excess amount of calcium hydroxide in the alkaline aqueous solution, adding, for example, 0.17 to 100 g, particularly 0.4 to 10 g, of calcium hydroxide per 100 mL of water, including both dissolved and precipitated portions.

[0048] The pH of the alkaline aqueous solution used in step (A) is not particularly limited, but from the viewpoint of efficiency, safety, and economics of the deactivation treatment of lithium-ion secondary batteries, a pH of 10 to 14 is preferred, and 11 to 13 is more preferred.

[0049] There are no particular restrictions on the water used in process (B), and various types of water can be used, such as distilled water, tap water, industrial water, ion-exchanged water, deionized water, pure water, and electrolyzed water. It is preferable that the water used in process (B) is neutral or alkaline (6 ≤ pH ≤ 14).

[0050] Furthermore, it is preferable to use an excess amount of the alkaline aqueous solution in step (A) and the water in step (B). Specifically, this will be described in detail below.

[0051] In this invention, the active lithium in a lithium-ion secondary battery preferentially reacts with water upon contact, gradually deactivating while generating hydrogen. The reaction is represented by the following equation: LiC x +yH2O→y / 2H2+Li + +yOH - +xC The reaction proceeds accordingly. In this process, the flammable organic solvent contained in the electrolyte of the lithium-ion secondary battery is dissolved and diluted in water. Furthermore, the oxygen concentration remains constant before and after the reaction; that is, no oxygen is generated by the reaction. The alkaline aqueous solution or water also functions as a coolant to prevent a rapid rise in temperature, thus suppressing ignition and heat generation, making it a safe method. In addition, the presence of excess water prevents a shortage of water (H2O) in the above reaction.

[0052] Although hydroxide ions are generated in this reaction, they are consumed in the decomposition reactions of carbonate and LiPF6 described later. Therefore, it is possible to maintain the pH within an appropriate range between neutral and alkaline and continue the deactivation treatment.

[0053] Based on the above, it is preferable that the amount of alkaline aqueous solution used in step (A) and the amount of water used in step (B) be in excess, preferably 10 mL or more, more preferably 70 mL or more, and even more preferably 130 mL or more, per 1 Wh of the capacity of the target lithium-ion secondary battery. While the amount of alkaline aqueous solution used in step (A) and the amount of water used in step (B) should be as high as possible, and there is no particular upper limit, it is undesirable to use too much alkaline aqueous solution or water from the viewpoint of miniaturizing the device. Therefore, it is preferable that the amount of alkaline aqueous solution or water be 1000 mL or less per 1 Wh of the capacity of the target lithium-ion secondary battery. Typically, it is around 50 to 500 mL per 1 Wh of the capacity of the target lithium-ion secondary battery.

[0054] As described above, in the method for deactivating a lithium-ion secondary battery of the present invention, it is possible to gently deactivate the lithium contained in the lithium-ion secondary battery by opening the lithium-ion secondary battery in neutral or alkaline water or aqueous solution.

[0055] In particular, in the method for deactivating lithium-ion secondary batteries of the present invention, when step (A), that is, an alkaline aqueous solution, is used, the hydrolysis of organic solvents such as carbonate is accelerated, as described below, and the gas generation time can be shortened.

[0056] In aqueous solutions, carbonates and other organic solvents present in the electrolyte of lithium-ion secondary batteries undergo hydrolysis, gradually generating carbon dioxide. The expected decomposition reaction, for example, when the carbonate is ethylene carbonate, is represented by the following reaction equation.

[0057] [ka]

[0058] In the method for deactivating lithium-ion secondary batteries of the present invention, step (A), that is, when an alkaline aqueous solution is used, is useful in that the reaction time can be shortened and the generated carbon dioxide can be easily captured by reacting it with the alkaline aqueous solution (if limewater is used as the alkaline aqueous solution, it can be easily fixed as calcium carbonate), thus further shortening the exhaust time.

[0059] Furthermore, in aqueous solutions, LiPF6, which is present as an electrolyte salt in the electrolyte solution of lithium-ion secondary batteries, dissolves into the treatment solution during the deactivation treatment of lithium-ion secondary batteries. In this process, LiPF6 readily hydrolyzes while generating HF.

[0060] [ka]

[0061] In the method for deactivating lithium-ion secondary batteries of the present invention, when step (A), i.e., an alkaline aqueous solution is used, harmful fluoride ions are easily immobilized as salts. For example, when limewater is used as the alkaline aqueous solution, fluoride ions are easily immobilized in situ as calcium fluoride (CaF2), and the fluoride ion separation step can be omitted.

[0062] Furthermore, if step (B), i.e., water is used, it is preferable to use an alkaline aqueous solution in a later step to remove the generated fluoride ions. For this reason, even when using step (B), i.e., water, it is preferable to use an alkaline aqueous solution in combination, and therefore it is preferable to use step (A), i.e., an alkaline aqueous solution from the beginning.

[0063] Furthermore, in the method for deactivating lithium-ion secondary batteries of the present invention, if step (A), that is, an alkaline aqueous solution, is used, the iron-based material will not rust. Therefore, in lithium-ion secondary battery deactivation treatment facilities, etc., it is possible to use inexpensive iron-based materials for components that come into contact with the treatment solution, thus broadening the range of material selection.

[0064] (1-2) Atmosphere In the method for deactivating the lithium-ion secondary battery of the present invention, when step (A), that is, when an alkaline aqueous solution is used, the atmosphere is not particularly limited. Among these, an inert atmosphere such as a nitrogen gas atmosphere or an argon gas atmosphere, or a reducing gas atmosphere such as a hydrogen gas atmosphere is preferred.

[0065] On the other hand, when using step (B), that is, water, as a method for deactivating the lithium-ion secondary battery of the present invention, an inert atmosphere such as a nitrogen gas atmosphere or an argon gas atmosphere, or a reducing gas atmosphere such as a hydrogen gas atmosphere is used.

[0066] When such an atmosphere is adopted, the absence of oxygen in the atmosphere makes the hydrogen generated during the deactivation process of lithium-ion secondary batteries chemically stable, further reducing the risk of ignition and overheating of the lithium-ion secondary batteries.

[0067] (1-3)Temperature The temperature at which the lithium-ion secondary battery deactivation method of the present invention is performed is not particularly limited, and can be performed at room temperature, for example. In other words, high-temperature incineration, as in conventional methods, is unnecessary, making it possible to make it a simpler and safer method. Specifically, the temperature at which the lithium-ion secondary battery deactivation method of the present invention is performed can be, for example, 10 to 80°C, preferably 15 to 45°C.

[0068] (1-4) Opening treatment In the method for deactivating a lithium-ion secondary battery of the present invention, there are no particular limitations on the opening process of the lithium-ion secondary battery, and various methods can be employed. Specifically, these include crushing or cutting the lithium-ion secondary battery, making a hole that penetrates the casing of the lithium-ion secondary battery, or opening part or all of the casing of the lithium-ion secondary battery. Note that "crushing a lithium-ion secondary battery" means tearing and crushing the lithium-ion battery. Furthermore, "crushing or cutting a lithium-ion secondary battery" does not mean only crushing or cutting the casing of the lithium-ion secondary battery to expose the inside. "Crushing or cutting a lithium-ion secondary battery" also means crushing or cutting unspecified locations of the lithium-ion secondary battery, thereby also crushing or cutting housing components such as current collectors and separators that are arranged inside the casing.

[0069] Furthermore, in this invention, the number of times the lithium-ion secondary battery is crushed or cut is not particularly limited as long as it is one or more times, but it is preferable to crush or cut it multiple times. Moreover, when crushing or cutting the lithium-ion secondary battery multiple times, it is preferable to crush or cut it at different locations each time. This allows for rapid deactivation and enables rapid progress of processes such as physical sorting in the post-deactivation process.

[0070] In this case, by cutting part or all of the casing of the lithium-ion secondary battery, the lithium-ion secondary battery deactivation process of the present invention can be performed particularly safely among the lithium-ion secondary battery deactivation methods of the present invention.

[0071] Furthermore, by crushing or cutting the lithium-ion secondary battery, or by drilling holes through the lithium-ion secondary battery casing, the deactivation time can be particularly shortened among the lithium-ion secondary battery deactivation methods of the present invention. In conventional dry deactivation methods performed in air, if the lithium-ion secondary battery is crushed or cut, or if holes are drilled through the lithium-ion secondary battery casing, the lithium-ion secondary battery may ignite or generate heat. However, by employing the lithium-ion secondary battery deactivation method of the present invention, the lithium-ion secondary battery can be safely deactivated even if it is crushed or cut, or if holes are drilled through the lithium-ion secondary battery casing.

[0072] (1-5) Immersion treatment After the lithium-ion secondary battery has been subjected to the opening treatment described above, the active lithium in the lithium-ion secondary battery comes into contact with water and reacts preferentially, slowly deactivating while generating hydrogen. The reaction in this case is represented by the reaction equation: LiC x +yH2O→y / 2H2+Li + +yOH - +xC The process proceeds accordingly. In this process, the flammable organic solvent contained in the electrolyte of the lithium-ion secondary battery is dissolved and diluted in water. Furthermore, the oxygen concentration remains constant before and after the reaction; that is, no oxygen is generated by the reaction. The alkaline aqueous solution or water also functions as a coolant to prevent a rapid rise in temperature, thus suppressing ignition and heat generation, making it a safe method.

[0073] Furthermore, if the above reaction does not proceed, that is, if hydrogen is no longer generated, it can be determined that the deactivation process of the lithium-ion secondary battery is complete. Therefore, when bubbles no longer appear visually, it can be determined that the deactivation process of the lithium-ion secondary battery is complete. Thus, according to the present invention, the progress of the deactivation of the lithium-ion secondary battery can be visualized by the rate (condition) of bubble generation. As a result, a safer and more efficient process can be achieved compared to conventional processing methods.

[0074] From a safety standpoint, it is preferable to consider the deactivation process complete when the generation of bubbles has completely stopped. However, from the standpoint of work efficiency, deactivation may be considered complete when the bubble generation rate falls below a predetermined standard. In determining this standard, optical or quantitative methods can be employed. Optical methods may include, for example, measurement using a spectroscopic device, or observation by photography or visual inspection. Quantitative methods may involve, for example, collecting the generated bubbles and measuring the volume of bubbles generated within a predetermined time.

[0075] Furthermore, the generated hydrogen can be recovered.

[0076] Based on the above, it is preferable to immerse the lithium-ion secondary battery in an alkaline aqueous solution or water after the opening treatment until no more bubbles are visible. The specific immersion time can be, for example, 10 minutes to 24 hours, and particularly 30 minutes to 6 hours.

[0077] 2. Method for separating and recovering metallic elements from lithium-ion secondary batteries The present invention provides a method for deactivating lithium-ion secondary batteries that does not generate toxic gases, can be performed using relatively small equipment, and allows for the safe dismantling of lithium-ion secondary batteries.

[0078] Therefore, lithium-ion secondary batteries can be deactivated easily and safely at various locations in urban areas, such as automobile dismantling yards, and at the sites of automobile accidents. This allows for the easy and safe dismantling and transportation of lithium-ion secondary batteries, and enables the separation and recovery of various elements. An example of this separation and recovery method is shown in Figure 2.

[0079] Lithium-ion secondary batteries or their crushed materials, which have been safely deactivated in this manner, contain metallic elements such as lithium, aluminum, copper, nickel, cobalt, and manganese, and these can be separated and recovered by physical sorting or chemical treatment.

[0080] In the method for deactivating a lithium-ion secondary battery of the present invention, if, for example, a hole is made through the casing of the lithium-ion secondary battery, or part or all of the casing of the lithium-ion secondary battery is opened, it is preferable to reduce the particle size of the target material to facilitate subsequent processing. Figure 2 shows an example in which a lithium-ion secondary battery was deactivated by cutting using the attritor described in Figure 4.

[0081] Specifically, the casings with control boards can be sorted by size from the deactivated solid material. A large amount of aluminum can be recovered from this. After that, they can be cut to the desired size (20 mm x 20 mm in Figure 2) and then crushed using a ball mill with iron balls or the like.

[0082] Subsequently, copper scraps, aluminum scraps, separator pieces, and iron balls used in the ball mill can be recovered by sieving (1) with a mesh size of approximately 0.5 to 3 mm (1 mm in Figure 2). From this mixture, the iron balls can be recovered by magnetic separation, and the separator pieces can be recovered by sieving (2) with a mesh size of approximately 5 to 15 mm (10 mm in Figure 2). The remaining material is a mixture of copper scraps and aluminum scraps, which can be separated by physical separation such as eddy current separation and shipped to existing processing plants.

[0083] On the other hand, by filtering the suspension after the above sieving (1), oxides such as lithium, cobalt, nickel, and manganese, as well as graphite powder, aluminum hydroxide, and calcium fluoride, can be separated. These can be processed at medium-sized smelters specializing in waste lithium-ion secondary battery processing or at existing smelters. From this, approximately 70% of the lithium and almost all of the nickel and cobalt can be recovered.

[0084] Furthermore, most valuable elements can be recovered as solids, and the present invention is particularly useful because it allows for the concentration and separation of elements such as lithium and graphite, which are difficult to recover using conventional dry treatment methods, as solids. In addition, since copper and aluminum can be recovered as metals using the present invention, chemical treatments such as acid leaching and reduction, as in conventional methods, are unnecessary, and they can be easily recycled afterward.

[0085] From the above, the method for deactivating lithium-ion secondary batteries of the present invention makes it possible to realize a wet recycling process that is extremely compact and has a high recovery rate of valuable materials compared to conventional dry processes. Preferably, it can transform the transportation of large waste lithium-ion secondary batteries to aggregation facilities and smelters into a safe and simple process. For example, by setting up processing plants dispersed at various automobile dismantling sites and deactivating lithium-ion secondary batteries at each processing plant, it is possible to solve the problem of transporting waste lithium-ion secondary batteries, which has been a bottleneck.

[0086] Furthermore, by providing a vehicle equipped with a lithium-ion secondary battery deactivation device, as shown in Figure 3, it is possible to place waste lithium-ion secondary batteries from broken-down vehicles, etc., into a chamber containing an alkaline aqueous solution or water, then cut and crush the waste lithium-ion secondary batteries using a cutting and crushing section (for example, a pair of rollers facing a cutting blade), and then separate each element from the crushed material.

[0087] Here, the section into which the waste lithium-ion secondary batteries are placed is equipped with a lid that can be opened and closed to cover the top of the container. When the top of the container is closed with this lid, the space formed on the lid and the alkaline aqueous solution or water is sealed, creating a closed space isolated from the outside. In this state, when an inert gas (nitrogen gas) is supplied from the gas supply unit (nitrogen generator) via a tube, the closed space is filled with the inert gas, and an inert gas atmosphere is formed. Furthermore, if a reducing gas (for example, hydrogen gas) is supplied, the closed space is filled with the reducing gas, and a reducing gas atmosphere can be formed.

[0088] The vehicle is equipped with a single sieve or multiple sieves with different mesh sizes, allowing for the separation of crushed material as it passes through the chamber along with the alkaline aqueous solution or water. If multiple sieves with different mesh sizes are provided, the crushed material can be separated according to size. The alkaline aqueous solution or water from which the crushed material has been removed is then supplied back into the chamber.

[0089] Furthermore, the vehicle is equipped with a compressor and a hydrogen storage tank to recover hydrogen produced when lithium is deactivated. The compressor has the function of compressing hydrogen from a closed space and supplying it to the hydrogen storage tank. The vehicle may also be equipped with a fuel cell that uses hydrogen to generate electricity or for other purposes.

[0090] In other words, without the need to prepare separate processing equipment, it is possible to deactivate waste lithium-ion secondary batteries and recover each element within the vehicle shown in Figure 3, and this can be carried out at automobile dismantling sites and sites where waste lithium-ion secondary batteries are generated. Afterwards, the batteries can be transported to dedicated processing facilities or smelters for recycling of various metal elements and treatment of waste liquid. As a result, on-site crude separation processing with deactivation can be realized, and it can be used as a mobile primary smelter in various parts of the world, including developing countries. [Examples]

[0091] The present invention will be specifically described below with reference to examples and comparative examples, but the present invention is not limited to these examples.

[0092] In this embodiment, "no pretreatment" means that, as shown in the left diagram of Figure 5, no damage is made to the casing and the lithium-ion secondary battery present inside the casing is not exposed.

[0093] In this embodiment, "opening" means, as shown in the middle diagram of Figure 5, cutting away only a portion of the casing without damaging the lithium-ion secondary battery inside the casing, thereby exposing the lithium-ion secondary battery inside the casing.

[0094] In this embodiment, "cutting" means cutting the casing along with the lithium-ion secondary battery contained within it, as shown in the right diagram of Figure 5.

[0095] The lithium-ion rechargeable battery (3cm x 4cm x 0.7cm; nominal voltage 3.7V; charging capacity 895mAh; pre-charged) used as a sample was newly purchased and charged.

[0096] Comparative Example 1: No underwater pretreatment In a glove box under a nitrogen atmosphere (oxygen concentration: less than 1 volume%), the resin extracoating of the lithium-ion secondary battery was removed, and the casing was not cut off. 250 mL of deionized water was placed in a gas collecting bottle as the treatment solution, and the presence or absence of ignition and bubbles was checked when the lithium-ion secondary battery was immersed.

[0097] In this case, although there was no ignition, no bubbles were generated, and the deactivation of the lithium-ion secondary battery did not progress at all.

[0098] Comparative Example 2: No pretreatment in limewater In a glove box under a nitrogen atmosphere (oxygen concentration: less than 1 volume%), the resin extracoating of the lithium-ion secondary battery was removed, and the casing was not cut off. 250 mL of limewater containing calcium hydroxide (1 g of calcium hydroxide added to the treatment solution) was placed in a gas collecting bottle, and the presence or absence of ignition and bubbles was checked when the lithium-ion secondary battery was immersed in the solution.

[0099] In this case, although no fire occurred, bubbles continued to form for about 3 days to a week, and the battery cell voltage only dropped to about 1V. This indicates that at least 3 days are required to discharge a lithium-ion secondary battery, and even then, it was not possible to completely deactivate the lithium-ion secondary battery.

[0100] Comparative Example 3: Dry Cutting In a glove box under a nitrogen atmosphere (oxygen concentration: less than 1 volume%), the resin extracoating of the lithium-ion secondary battery was removed, and the casing, along with the internal lithium-ion secondary battery, was cut approximately 1 cm to confirm its reactivity. In other words, the same method as in Patent Document 2 was used.

[0101] As a result, it was found that cutting the wire immediately generated sparks, causing the entire lithium-ion secondary battery to overheat violently, producing white smoke and the casing to become red-hot, making this an extremely dangerous method. The results are shown in Figure 6.

[0102] Example 1: Underwater opening In a glove box under a nitrogen atmosphere (oxygen concentration: less than 1 volume%), the resin outer casing of the lithium-ion secondary battery was removed, and a portion of the casing (only the side) was cut away to avoid damaging the internal lithium-ion secondary battery. 250 mL of deionized water was then placed in a gas collecting bottle as the treatment solution, and the presence or absence of ignition and bubbles was checked.

[0103] In this case, a gas containing hydrogen gas was generated from the terminals and inside the cell, and deactivation progressed. Furthermore, no ignition occurred during the reaction, and the generation of bubbles ceased after approximately 16 hours. Therefore, it can be understood that the deactivation of the lithium-ion secondary battery was completed in approximately 16 hours.

[0104] Example 2: Limewater Opening In a glove box under a nitrogen atmosphere (oxygen concentration: less than 1 volume%), the resin outer casing of the lithium-ion secondary battery was removed, and a portion of the casing (only the side) was cut away without damaging the internal lithium-ion secondary battery. 250 mL of limewater containing calcium hydroxide (1 g of calcium hydroxide was added to the treatment solution) was placed in a gas collecting bottle as the treatment solution, and the presence or absence of ignition and bubbles was checked.

[0105] In this case, gas containing hydrogen gas was generated from the terminals and inside the cell, and deactivation progressed. During the reaction, there was no ignition, and no bubbles were generated after about 9 hours, the cell voltage fell to below 1V, and dropped to 0V after about 24-30 hours. Therefore, it can be understood that the deactivation of the lithium-ion secondary battery was completed in about 9 hours. At the end of the reaction, the aluminum material of the casing was oxidized, forming a white film, and the formation of LiAl2(OH)7(H2O)2 and CaCO3 was confirmed. Therefore, it is suggested that the deactivation of the lithium-ion secondary battery progressed faster than in Example 1 by the open immersion treatment using limewater. The results are shown in Figure 7.

[0106] Example 3: Cutting in lime underwater In a glove box under a nitrogen atmosphere (oxygen concentration: less than 1 volume%), the resin outer casing of the lithium-ion secondary battery was removed, the casing and the lithium-ion secondary battery inside were cut open by approximately 1 cm, 250 mL of limewater containing calcium hydroxide (1 g of calcium hydroxide was added to the treatment solution) was placed in a gas collecting bottle as the treatment solution, and the presence or absence of ignition and bubbles was checked.

[0107] In this case, gas containing hydrogen gas was generated from the terminals and inside the cell, and deactivation progressed. Furthermore, it can be understood that the deactivation of the lithium-ion secondary battery was completed when no ignition occurred during the reaction and no bubbles were generated after about one hour.

[0108] Test Example 1: Inactivation treatment and element recovery in limewater The deactivation behavior of lithium-ion secondary batteries when cut after being immersed in an aqueous solution was investigated at 23-25°C. Figure 2 shows the flowchart of the lithium-ion secondary battery deactivation process. The resin extracoating of the lithium-ion secondary battery was removed from the glove box under a nitrogen atmosphere (oxygen concentration: less than 1 vol%), exposing the aluminum casing. 300 mL of limewater containing calcium hydroxide (1 g of calcium hydroxide was added to the treatment solution) was filled into chamber 1 of the lithium-ion secondary battery cutting device (attritor) shown in Figure 4, and the lithium-ion secondary battery placed on the sample stage 2 was immersed in the solution. The device was then operated, and the lithium-ion secondary battery was cut by pressing it against a stainless steel blade 3 mounted inside chamber 1 with a rotating rod 4. To ensure safer operation, a drop lid 5 was placed inside chamber 1. If the lithium-ion secondary battery could not be cut in one operation of the device, the device was operated repeatedly until the lithium-ion secondary battery was cut.

[0109] After cutting, the lithium-ion secondary batteries were left immersed in the processing solution until the formation of bubbles ceased, and gas samples were taken as needed. The oxygen and hydrogen concentrations of the sampled gases were analyzed by gas chromatography (Shimadzu Corporation, GC-8A). The results are shown in Figure 8.

[0110] These results indicate that hydrogen gas was generated during the deactivation process, suggesting that the lithium in the negative electrode was deactivated by a reaction with water. Furthermore, the oxygen concentration remained nearly constant, suggesting that no decomposition of the positive electrode active material or oxidation of water occurred.

[0111] After the reaction was complete, the processing liquid and solid material were removed from the glove box and released into the atmosphere. The solid material was then manually sorted to remove aluminum casing fragments and cut into pieces approximately 2 cm x 2 cm in size. From the casing fragments removed in this way, it was possible to recover 86.7% of the aluminum as metallic aluminum. Next, the cut solid material was placed in a polypropylene bottle with approximately 20 iron balls (average diameter 0.9 cm) and 100 mL of deionized water, and a ball mill was performed for 10 hours. The pulverized solid material was separated using a sieve with a mesh size of 1 mm, and the solid on the sieve was further separated using magnetic separation and a sieve with a mesh size of 10 mm to separate it into iron balls, copper scraps, aluminum scraps, and separator fragments. A black suspension was recovered below the sieve, and this was filtered to recover a black powder and a clear ball mill liquid. A portion of these recovered materials was sampled and dissolved in a mixture of hydrochloric acid and hydrogen peroxide, and the metallic elements contained in each were quantified by the ICP-AES method. The results are shown in Figures 9 and 10. As a result, it was possible to recover 69% of lithium metal, 99.2% of nickel, and 98.9% of cobalt as solid oxides, and 94.2% of copper as metallic copper.

[0112] Test Example 2: Decomposition of carbonates in electrolyte solution In aqueous solutions, the carbonate contained as an organic solvent in the electrolyte of lithium-ion secondary batteries undergoes hydrolysis, gradually generating carbon dioxide. If the generation of carbon dioxide continues for a long period, concerns arise regarding the safety of storage and transportation of the processed solution. The expected decomposition reaction in this case, for example, when the carbonate is ethylene carbonate, is assumed to be as follows:

[0113] [ka]

[0114] Therefore, we added 8.8g of ethylene carbonate to 100mL of each solution and compared their behavior.

[0115] Figure 11 shows the ultraviolet-visible absorption spectra when ethylene carbonate is added to deionized water. Comparing the results after 1 hour, 18 hours, and 36 hours with the results after 3 months, the intensity of the absorption spectra decreased slightly. Therefore, it is suggested that in deionized water, the deactivation reaction of lithium-ion secondary batteries is not complete even after 36 hours, and the reaction proceeds gradually until 3 months, indicating that the decomposition of carbonate takes a long time.

[0116] Conversely, when 100 mL of limewater with calcium hydroxide precipitated (14 g of calcium hydroxide added to the treatment solution) was used, hydrolysis was completed in a short time of less than one hour, suggesting an advantage in terms of the safety of storage and transportation of the treatment solution.

[0117] Test Example 3: Use of iron-based materials in limewater treatment To investigate the use of steel materials in equipment such as reaction vessels for the deactivation of lithium-ion secondary batteries in aqueous solutions, the corrosion behavior of iron material samples in various solutions was studied.

[0118] Approximately 2g of iron balls (average diameter 5mm, SUJ-2) were placed in a polypropylene bottle, and 100mL of each aqueous solution was added and left to stand in the air. The aqueous solutions used in this test were limewater (10g of calcium hydroxide was added to the treatment solution), 0.01mM hydrofluoric acid, and 0.25M NaCl aqueous solution. The NaCl aqueous solution was chosen because saltwater is used in the discharge treatment of lithium-ion secondary batteries. The results are shown in Figure 12 and Table 1.

[0119] [Table 1]

[0120] These results suggest that iron-based materials cannot be used in hydrofluoric acid and NaCl aqueous solutions, as discoloration occurred after one day. On the other hand, no change occurred in limewater even after two months. Since no change occurred even in an atmospheric environment with oxygen present, it is suggested that similar no change would occur when using an inert or reducing atmosphere. Therefore, in the lithium-ion secondary battery deactivation method of the present invention, it is suggested that iron-based materials such as steel can be used for equipment materials including the reaction vessel, thus broadening the range of material selection. [Explanation of symbols]

[0121] 1 Chamber 2 Sample stage 3 blades 4 Rotating rods 5. Drop lid

Claims

1. A method for deactivating lithium-ion secondary batteries, Under an inert gas atmosphere or a reducing gas atmosphere, (A) The process of opening the lithium-ion secondary battery in an alkaline aqueous solution. A method that includes [a certain feature].

2. The method according to claim 1, wherein the amount of alkaline aqueous solution used in step (A) is 10 mL or more per 1 Wh of the capacity of the lithium-ion secondary battery.

3. The method according to claim 1 or 2, wherein the pH of the alkaline aqueous solution in step (A) is 10 to 14.

4. The method according to any one of claims 1 to 3, wherein the alkaline compound used as the alkaline aqueous solution is at least one selected from the group consisting of calcium hydroxide, calcium oxide, magnesium hydroxide, magnesium oxide, sodium hydroxide, potassium hydroxide, and lithium hydroxide.

5. The method according to any one of claims 1 to 4, wherein in step (A), the alkaline aqueous solution is limewater.

6. The method according to any one of claims 1 to 5, wherein the content of the alkali compound in the alkaline aqueous solution is greater than the saturation concentration.

7. The method according to any one of claims 1 to 6, wherein the step of opening the lithium-ion secondary battery is to crush or cut the lithium-ion secondary battery, to make a hole that penetrates the casing of the lithium-ion secondary battery, or to open part or all of the casing of the lithium-ion secondary battery.

8. The method according to any one of claims 1 to 7, wherein step (A) is performed at 10 to 80°C.

9. The method according to any one of claims 1 to 8, wherein the timing of completion of deactivation is determined from the state of bubble generation from the opening.

10. A lithium-ion secondary battery deactivation device used to deactivate lithium-ion secondary batteries in an alkaline aqueous solution, A chamber in which an alkaline aqueous solution is stored, A mechanism disposed within the chamber and for opening the lithium-ion secondary battery placed inside the chamber. A lid that can be opened and closed is placed on the chamber and isolates the enclosed space formed on the alkaline aqueous solution from the outside, A gas supply unit that supplies an inert gas or reducing gas to the enclosed space. A lithium-ion secondary battery deactivation device equipped with the following features.

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