Method for treating waste lithium-ion batteries

Abstract

To provide a processing method for a waste lithium-ion battery, which can inhibit degradation of collected resources and deterioration of a working environment.SOLUTION: A processing method for a waste lithium-ion battery includes a step of discharging residual electric power of the waste lithium-ion battery by immersing it in an amine-based solution including a carbamate anion or a bicarbonate ion. Preferably, the amine-based solution is an amine-based absorbing liquid that absorbs carbon dioxide.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a method for treating waste lithium-ion batteries.

Background Art

[0002] A lithium-ion battery is composed of a positive electrode material in which lithium, cobalt, nickel, etc. are coated on an aluminum foil, a negative electrode material in which graphite, etc. are coated on a copper foil, an electrolyte solution, a separator, etc. Therefore, valuable substances such as lithium, cobalt, nickel, and copper are contained in the lithium-ion battery. Therefore, recycling waste lithium-ion batteries (waste lithium-ion batteries) to recover these valuable substances is extremely beneficial for our country with scarce resources.

[0003] Waste lithium-ion batteries are difficult to handle because there is a risk of ignition, electric shock, and generation of hydrogen fluoride during recycling. Therefore, after the waste lithium-ion battery is heated and detoxified by roasting or the like, separation and recovery are performed by crushing or pulverizing, sieving, sorting, etc.

[0004] However, if a waste lithium-ion battery in a charged state is directly heated at a high temperature, there is a risk that the waste lithium-ion battery will generate heat and explode. Therefore, by discharging the waste lithium-ion battery before the heat treatment, rapid heat generation during heating can be suppressed. Generally, discharging is performed by a method of connecting to an electric circuit, but since it takes a long time, it is not realistic to use this method in a recycling system.

[0005] Therefore, Patent Documents 1 to 3 disclose that the waste lithium-ion battery is immersed in an aqueous sodium chloride solution or the like to discharge the waste lithium-ion battery. Patent Documents 2 to 4 disclose that the waste lithium-ion battery is immersed in an aqueous solution of an inorganic compound such as sodium sulfate, ammonium nitrate, sodium carbonate, sodium hydrogen carbonate, calcium carbonate, or magnesium oxide to discharge the waste lithium-ion battery. Further, Patent Document 3 discloses that the waste lithium-ion battery is immersed in an aqueous solution of an organic acid such as an acetic acid aqueous solution to discharge the waste lithium-ion battery.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Summary of the Invention

Problems to be Solved by the Invention

[0007] However, when an aqueous solution of an inorganic compound is used as the discharge liquid, the inorganic compound remains after the heat treatment, so there is a risk that the quality of the recovered resources will deteriorate. In particular, when an aqueous solution of sodium chloride is used as the discharge liquid, the heating furnace used in the subsequent heat treatment process may be corroded. Further, when an aqueous solution of an organic acid is used as the discharge liquid, since the electrolytic solution used in a lithium ion battery is equivalent to kerosene, there is a risk of deteriorating the working environment, such as ignition during the discharge process.

[0008] An object of the present invention is to provide a method for treating a waste lithium ion battery capable of suppressing a decrease in the quality of recovered resources and deterioration of the working environment.

Means for Solving the Problems

[0009] The method for treating a waste lithium ion battery of the present invention includes a step of immersing the waste lithium ion battery in an amine-based aqueous solution containing a carbamate anion or a bicarbonate ion to discharge the residual power of the waste lithium ion battery.

[0010] According to the method for treating a used lithium-ion battery of the present invention, since an amine-based aqueous solution containing a carbamate anion or a bicarbonate ion is used as a discharging solution, the residue of the discharging solution does not contain an inorganic compound, so there is no risk of deterioration in the quality of the recovered resources after the heat treatment. Further, since the residue of the discharging solution does not contain chloride, there is no risk of corrosion of the heating furnace for performing the heat treatment. Further, even if the water concentration of the amine-based aqueous solution is high, it is possible to sufficiently discharge, so it is possible to suppress deterioration of the working environment due to ignition or the like.

[0011] In the method for treating a used lithium-ion battery of the present invention, it is preferable that the amine-based aqueous solution is an amine-based absorption liquid that has absorbed carbon dioxide.

[0012] In this case, by using, as a discharging solution, an amine-based absorption liquid that is used in a carbon dioxide separation and recovery system and has been discarded due to a decrease in the ability to absorb carbon dioxide, the discarded amine-based absorption liquid can be reused, and it is possible to reduce the cost required for the discharging solution.

[0013] Further, in the method for treating a used lithium-ion battery of the present invention, it is preferable that the amine-based aqueous solution has a water content of 60% by weight or more.

[0014] In this case, since the water concentration of the amine-based aqueous solution is high, it is possible to further suppress deterioration of the working environment due to ignition or the like during discharging of the lithium-ion battery.

Embodiments for Carrying Out the Invention

[0015] A method for treating a used lithium-ion battery according to an embodiment of the present invention will be described.

[0016] In this treatment method, first, a discharging step is performed in which a used and discarded lithium-ion battery (used lithium-ion battery) is immersed in an amine-based aqueous solution and discharged. Details of the discharging step will be described later. It is preferable to wash the discharged used lithium-ion battery with water to remove the amine-based aqueous solution as much as possible.

[0017] Next, a heat treatment step of baking the used lithium-ion battery that has undergone the discharge treatment is performed. By heating the used lithium-ion battery, the electrolyte inside is removed, and the used lithium-ion battery is rendered harmless. Note that the type and shape of the heating furnace used in the heat treatment step are not particularly limited.

[0018] Next, a crushing step is performed in which the baked used lithium-ion battery is crushed to an appropriate size using a crusher, a disintegrator, etc. Then, a classification step is performed in which this crushed material is classified using a sieve, an air classifier, etc. Further, a separation step is performed in which various metals and the like are separated by component using a magnet, etc. As a result, rare metals such as cobalt and base metals such as copper and iron contained in the used lithium-ion battery can be recovered for each material. Note that the heat treatment step, the crushing step, the classification step, and the separation step may be performed in the same manner as in the prior art, the order of these may be changed, and further, other steps may be added.

[0019] Hereinafter, the discharge step of the method for treating a used lithium-ion battery according to the embodiment will be described in detail.

[0020] In the discharge step, the used lithium-ion battery is immersed in an amine-based aqueous solution to discharge the remaining power of the used lithium-ion battery. Here, the amine-based aqueous solution is an amine-based aqueous solution containing a carbamate anion (RNHCOO - ) or a bicarbonate ion (HCO3 - ). As the amine-based aqueous solution, for example, an aqueous solution of an amine compound having a carbamate anion group is suitable.

[0021] Primary amines and secondary amines generate carbamate anions when they absorb carbon dioxide (CO2). On the other hand, tertiary amines generate bicarbonate ions when they absorb carbon dioxide. Therefore, it is preferable to use an amine-based aqueous solution that has absorbed carbon dioxide as the amine-based aqueous solution.

[0022] In particular, it is preferable to use an amine-based absorbent that is used in a carbon dioxide capture and storage (CCS) system and is discarded due to a decrease in its ability to absorb carbon dioxide. This enables the reuse of the discarded amine-based absorbent and helps reduce the cost required for the discharge liquid.

[0023] The amine-based absorbent used for separating and recovering carbon dioxide from combustion exhaust gas generates ions such as carbamate anions and bicarbonate ions by absorbing carbon dioxide, resulting in an increase in electrical conductivity. Therefore, instead of using a new amine-based absorbent, a used amine-based absorbent with increased electrical conductivity after absorbing carbon dioxide is used as the discharge liquid.

[0024] As the amine-based absorbent, for example, monoethanolamine (MEA), methyldiethanolamine (MDEA), 2-amino-2-methyl-1-propanol (AMP), piperazine (PZ / PIPA), etc. are suitable, but not limited to these. Also, these may be used in combination.

[0025] The amine-based aqueous solution preferably has an electrical conductivity of 0.2 S / m or more. This is because the higher the electrical conductivity, the faster the discharge of the spent lithium-ion battery can be completed. If the electrical conductivity is 0.2 S / m or more, the discharge will be completed after soaking for about 20 hours, which is reasonable for an actual system.

[0026] Unlike the conventional technologies described above, such an amine-based aqueous solution does not contain inorganic compounds, so there is no risk of the quality of the recovered resources after heat treatment being reduced due to the residues of the discharge liquid. Also, since the residues of the discharge liquid do not contain chlorides, there is no risk of corrosion of the heating furnace for heat treatment. Moreover, since the amine-based aqueous solution can be discharged sufficiently even when the water concentration is high, it is possible to suppress the deterioration of the working environment due to ignition or the like. In particular, by setting the amine-based aqueous solution to 60% by weight or more, the risk of ignition can be further suppressed.

[0027] Note that the present invention is not limited to the method for treating waste lithium-ion batteries specifically described in the above-described embodiments, and can be appropriately changed within the scope described in the claims.

Example

[0028] Hereinafter, examples and comparative examples of the method for treating waste lithium-ion batteries of the present invention will be described.

[0029] As waste lithium-ion batteries, used in-vehicle lithium-ion batteries were prepared at 1.5 kg (one 40V lithium-ion battery) each. When these were measured with a residual voltage meter, the average residual voltage was 39.4V.

[0030] In Example 1, as the amine-based aqueous solution of the present invention, a used amine-based absorbent solution containing 30% by weight of MEA and absorbing carbon dioxide was prepared. When this amine-based absorbent solution was measured with an infrared spectrometer, the presence of carbamate anions was confirmed. When this amine-based absorbent solution was measured with a conductivity meter, the electrical conductivity was 3.3 [S / m].

[0031] Then, 30 [L] of the amine-based aqueous solution was poured into a container made of plastic, and the waste lithium-ion battery was immersed in this amine-based aqueous solution.

[0032] Then, every minute, the residual voltage of the waste lithium-ion battery was measured with a residual voltage meter. The time when the average value of the measured residual voltage reached 0.5 [V] was regarded as the completion of discharge. It took 1.2 [hours] until the completion of discharge.

[0033] In Example 2, as the discharge liquid, a used amine-based absorbent solution containing 15% by weight each of MEA and diethanolamine (DEA) and absorbing carbon dioxide was prepared. When this amine-based absorbent solution was measured with an infrared spectrometer, the presence of carbamate anions was confirmed. The electrical conductivity was 0.8 [S / m].

[0034] Then, in the same manner as in Example 1, a spent lithium-ion battery was immersed in this used MEA and DEA mixed aqueous solution. When 7.0 [hours] had elapsed, the average residual voltage of the spent lithium-ion battery became 0.5 [V] or less, and it was considered that the discharge was completed.

[0035] In Example 3, as the discharge liquid, a used amine-based absorption liquid containing 15% by weight each of DEA and MDEA and having absorbed carbon dioxide was prepared. When this amine-based absorption liquid was measured with an infrared spectrometer, the presence of carbamate anions was confirmed. The electrical conductivity was 0.3 [S / m].

[0036] Then, in the same manner as in Example 1, a spent lithium-ion battery was immersed in this used DEA and MDEA mixed aqueous solution. When 14.0 [hours] had elapsed, the average residual voltage of the spent lithium-ion battery became 0.5 [V] or less, and it was considered that the discharge was completed.

[0037] In Comparative Example 1, as the discharge liquid, a new amine-based absorption liquid containing 30% by weight of MEA and not having absorbed any carbon dioxide was used. When this amine-based absorption liquid was measured with an infrared spectrometer, the presence of carbamate anions was not confirmed. The electrical conductivity was 0.0 [S / m].

[0038] Then, in the same manner as in Examples 1 to 3, a spent lithium-ion battery was immersed in this new amine-based absorption liquid. However, even after 48 [hours] had elapsed, the average residual voltage of the spent lithium-ion battery did not become 0.5 [V] or less, so it was determined that discharge could not be performed.

[0039] In Comparative Example 2, industrial water was used as the discharge liquid. The electrical conductivity was 0.0 [S / m].

[0040] Then, in the same manner as in Examples 1 to 3, a spent lithium-ion battery was immersed in industrial water. However, even after 48 [hours] had elapsed, the average residual voltage of the spent lithium-ion battery did not become 0.5 [V] or less, so it was determined that discharge could not be performed.

[0041] In Comparative Example 3, an aqueous sodium chloride solution (brine) containing 3% by weight of sodium chloride (NaCl) was used as the discharge liquid. The electrical conductivity was 5.0 [S / m].

[0042] Then, in the same manner as in Examples 1 to 3, a used lithium-ion battery was immersed in this aqueous sodium chloride solution. When 1.0 [hour] had elapsed, the average residual voltage of the used lithium-ion battery became 0.5 [V] or less, and it was considered that the discharge was completed.

[0043] The results of Examples 1 to 3 and Comparative Examples 1 to 3 were summarized in Table 1.

[0044]

Table 1

[0045] From Table 1, in Examples 1 to 3 using the used amine-based absorbent, unlike Comparative Example 1 using a new amine-based absorbent and Comparative Example 2 using industrial water, the discharge was completed in a reasonable time of 14 [hours] or less. From this, it was found that it is reasonable to use the used amine-based absorbent as the discharge liquid.

[0046] Also, from Table 1, Example 1 using the used amine-based absorbent took a longer time to complete the discharge compared to Comparative Example 3 using an aqueous sodium chloride solution, but it was only slightly longer. In Comparative Example 3, since an aqueous sodium chloride solution is used, there is a risk of deterioration in the quality of the recovered resources due to residual chlorides after heat treatment and corrosion of the heating furnace. On the other hand, if the used amine-based absorbent is used as the discharge liquid, such problems do not occur, which is preferable.

Claims

1. A method for treating a waste lithium-ion battery, comprising a step of immersing the waste lithium-ion battery in an amine-based aqueous solution containing a carbamate anion to discharge the residual power of the waste lithium-ion battery, wherein the amine-based aqueous solution is an amine-based absorbent that has absorbed carbon dioxide.

2. The method for treating a waste lithium-ion battery according to claim 1, wherein the amine-based aqueous solution has a water content of 60% by weight or more.

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