JP7120578B2 - Method for recycling lithium-ion batteries - Google Patents

Description

The present invention relates to a lithium ion battery treatment method and a metallic material for a nickel metal hydride battery or a metallic material for hydrogen storage.

For effective use of resources, a method has been proposed for recovering valuable elements such as nickel and cobalt from used nickel-hydrogen secondary batteries (eg, Patent Document 1). According to the method of Patent Document 1, metals are recovered by performing physical separation treatment, oxidation treatment, and reduction/melting treatment.

A method for recovering valuables from electrodes has also been proposed for non-aqueous electrolyte secondary batteries such as lithium ion batteries (for example, Patent Document 2). In the method described in Patent Document 2, an electrode provided with an active material layer provided on a current collecting member via an intermediate film is used, and by separating the intermediate film from the surface of the current collecting member, the valuable substance is removed from the electrode. are collected.

A used non-aqueous electrolyte secondary battery may be dismantled and discarded. Patent Document 3 proposes discharging part or all of the remaining power before dismantling the battery. In the method described in Patent Document 3, the voltage between the positive electrode and the negative electrode in the battery is set such that the negative electrode potential is lower than the elution potential of the current collector contained in the negative electrode and/or the metal part electrically connected to the negative electrode. The potential is controlled to be

JP-A-2000-067935 JP 2010-108716 A JP 2013-101830 A

In recent years, the amount of used lithium-ion batteries for automobiles is expected to increase rapidly. In recycling lithium ion batteries, reduction of environmental load and processing energy is required. Used lithium-ion batteries for automobiles contain less valuable materials (such as cobalt) per unit mass than other lithium-ion batteries for mobile use. Complicated and expensive separation and purification processes are required to recover valuable materials from used lithium-ion batteries for automobiles. For this reason, the separation and refinement costs are high and it is economically difficult, so there is a problem that valuable resources are not utilized because they are incinerated, turned into slag and used as a roadbed material.

Accordingly, the present invention provides a processing method for efficiently and simply recovering valuables from lithium ion batteries, and a high-quality metal material for nickel metal hydride batteries or a metal material for hydrogen storage containing the recovered valuables. With the goal.

A method for treating a lithium ion battery according to the present invention includes a positive electrode comprising a current collector containing Al and a positive electrode active material layer containing a lithium transition metal composite oxide containing Ni and/or Co as a positive electrode active material; A method for treating a lithium ion battery in which a negative electrode comprising a current collector and a negative electrode active material layer containing Discharging the lithium ion battery, following the discharging, dismantling the lithium ion battery to recover the positive electrode, and removing the Ni and/or Co from the recovered positive electrode so as to and obtaining a metal material containing

A metal material for a nickel metal hydride battery or a metal material for hydrogen storage according to the present invention contains Ni and/or Co and Cu, and the Cu content is 0.05% by mass or less. .

According to the present invention, a lithium ion battery containing Ni and/or Co as valuable materials in its positive electrode is discharged, dismantled, the positive electrode is recovered, and the metal material is obtained from the recovered positive electrode. , valuables can be efficiently and simply recovered from lithium-ion batteries.

A metal material for a nickel metal hydride battery or a metal material for hydrogen storage containing Ni and/or Co is obtained from the positive electrode recovered by disassembling the lithium ion battery. By setting the elution amount of Cu during discharge to 0.02% by mass or less with respect to the mass of the positive electrode, a good quality nickel metal hydride battery metal material or hydrogen with a Cu content of 0.05% by mass or less can be obtained. A storage metal material is obtained.

1 is a perspective view of a lithium-ion battery treated by the method of the present embodiment; FIG. It is a flow chart which shows the processing method concerning this embodiment. It is a graph (1) plotting the Cu content in the positive electrode. It is the graph (2) which plotted Cu content in a positive electrode. 4 is a graph showing remaining capacity of a lithium-ion battery after discharging. 7 is a graph (1) showing the P concentration in the recovered liquid after cleaning the inside of the battery case. Fig. 2 is a graph (2) showing the concentration of P in the recovered liquid after washing the inside of the battery case;

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

1. Overall Configuration FIG. 1 is a perspective view of a lithium ion battery (hereinafter also referred to as LiB) processed in this embodiment. The LiB 10 includes an electrode body (not shown) housed in the battery case 12 together with an electrolyte. Battery case 12 is made of an aluminum alloy and includes case body 14 and lid 16 . The case main body 14 and the lid body 16 are laser welded. A safety valve 18 , a positive electrode terminal 20 and a negative electrode terminal 22 are provided on the lid body 16 .

The electrode assembly includes a positive electrode and a negative electrode wound with a separator interposed therebetween. The positive electrode has a positive electrode current collector and a positive electrode active material layer. In this embodiment, the positive electrode current collector is an Al foil, and the mass ratio of the positive electrode current collector in the positive electrode is 5 to 25% by mass. The positive electrode active material layer contains a positive electrode active material, a conductive material, and a binder. The mass ratios of the conductive material and the binder in the positive electrode active material layer are 0 to 30 mass % and 0 to 20 mass %, respectively, of the positive electrode. In this embodiment, the positive electrode active material is a lithium-transition metal composite oxide containing transition metals such as Ni and Co, such as a lithium-nickel-cobalt-manganese composite oxide.

The negative electrode has a negative electrode current collector and a negative electrode active material layer. In this embodiment, the negative electrode current collector is Cu foil, and the negative electrode active material is graphite. As the separator, a porous membrane or non-woven fabric made of resin such as polyethylene (PE) or polypropylene (PP) is generally used.

Any lithium composite oxide containing Ni and/or Co can be used as the positive electrode active material. For example, it can be selected from lithium-nickel composite oxide, lithium-cobalt composite oxide, lithium-nickel-cobalt composite oxide, lithium-nickel-manganese composite oxide, lithium-nickel-cobalt-aluminum composite oxide, and the like.

The electrolytic solution is a non-aqueous electrolytic solution containing a non-aqueous solvent and a lithium salt (electrolyte) soluble in this non-aqueous solvent. In the LiB 10 processed in this embodiment, carbonates are used as the non-aqueous solvent and LiPF ₆ is used as the electrolyte. Carbonates are mixtures containing dimethyl carbonate (DMC). LiBF ₄ , LiTFSA (lithium trifluoromethanesulfonylamide), LiTFSI (lithium bis(trifluoromethane)sulfonimide), or the like can be used as the electrolyte.

In the method of the present embodiment, as shown in the flowchart of FIG. 2, LiB10 is processed according to steps SP1, SP2, SP3, and SP4 to obtain a metallic material containing Ni and/or Co. In step SP1, the LiB 10 is discharged. Next, in step SP2, the inside of the battery case is cleaned. In step SP3, LiB is dismantled and the positive electrode is recovered. Finally, the positive electrode recovered in step SP4 is subjected to a thermite reaction as a reduction reaction to obtain a metal material containing Ni and/or Co. In the present embodiment, used LiB will be described as an example, but batteries treated by the method of the present embodiment are not limited to used ones. An unused lithium-ion battery or the like whose defect has been confirmed after manufacturing can also be processed by the method of the present embodiment. Each step will be described in detail.

[Discharge]
Step SP1 will be explained. When processing LiB, dismantling LiB with residual charge may cause a short circuit and cause ignition. Therefore, prior to dismantling, the used LiB is discharged to reduce the residual charge. It is desirable that the residual charge be as small as possible. However, when the used LiB is over-discharged, Cu is eluted from the negative electrode current collector into the electrolyte, contaminating the positive electrode. When LiB is overdischarged, the potential of the positive electrode decreases, the potential of the negative electrode increases, the voltage of LiB approaches 0 V, and equipotentials between the positive and negative electrodes occur. When the potential of the negative electrode reaches the elution limit potential of Cu, Cu is electrochemically eluted from the negative electrode current collector.

In this embodiment, discharge is performed so that the amount of Cu eluted from the negative electrode current collector into the electrolytic solution is 0.02% by mass or less with respect to the mass of the positive electrode. The Cu elution amount can be set to 0.02% by mass or less with respect to the mass of the positive electrode by appropriately setting the discharge conditions, specifically the holding voltage and holding time. If the eluted amount of Cu is 0.02% by mass or less with respect to the mass of the positive electrode, the effect of Cu is small, and contamination of the positive electrode can be ignored. That is, the Cu content in the metal material obtained from the positive electrode by the thermite reaction in the subsequent steps can be made 0.17% by mass or less. In particular, the Cu content in the metal material can be reduced to 0.05% by mass or less by adjusting the amount of Cu eluted according to the mass ratio of the positive electrode current collector, the conductive material, and the binder in the positive electrode. A metal material having a Cu content of 0.05% by mass or less can be applied as a metal material for a nickel metal hydride battery and a metal material for hydrogen storage. If the Cu content in the metal material is more than 0.05% by mass, when the metal material is used as an electrode material for a nickel metal hydride battery, Cu elution may cause a short circuit.

The forced discharge method was verified using the collected battery pack (48-cell specification). The battery pack is EH5 (manufactured by Honda Motor Co., Ltd.). The device used for the discharge test is a high-voltage BATTERY discharger TYS-91GE002 manufactured by Toyo System Co., Ltd. This device is specialized for discharging battery packs. Specifically, this device uses a fixed resistance of 40Ω (voltage of 100V or higher) to discharge the charged energy as heat.

The voltage of the battery pack before the start of discharge was 3.6 V in terms of a single cell. Since the end-of-discharge voltage of a lithium-ion battery is usually about 2.7 V, the forced discharge test was conducted with the end-of-discharge voltage set to 129.6 V so that the end-of-discharge voltage was 2.7 V/cell. After forced discharge, the battery pack was disassembled into individual battery cell units, and CC discharge (constant current discharge) was performed at 1.0 V, 0.6 V, and 0 V under the condition of 1C. After resting for 60 seconds, the discharge conditions were verified by changing the holding time of CV discharge (constant voltage discharge).

In order to measure the Cu elution amount, first, the discharged battery cell was disassembled and the electrode assembly was taken out. The wound body containing the positive electrode was unwound, the positive electrode was taken out, and the obtained positive electrode was washed. After the positive electrode was washed, five points were punched out to obtain samples of 16 mm in diameter. Samples were punched out from different locations when the positive electrode was wound, specifically from the outermost, innermost, and middle portions. The resulting sample contains a positive electrode current collector and a positive electrode active material layer. This sample was weighed, thermally decomposed with sulfuric acid, hydrochloric acid, nitric acid and perchloric acid, and then treated with dilute nitric acid and hydrogen peroxide water to a constant volume. This constant volume solution was analyzed by an ICP mass spectrometer manufactured by Thermo Fisher Scientific (ELEMENT XR) to determine the amount of Cu per mass of the sample.

Cu contained in the positive electrode was eluted from the negative electrode current collector and migrated to the positive electrode. The results obtained by analyzing the samples are shown in FIG. "x" in the plot of FIG. 3 indicates the amount of Cu in the positive electrode that was taken out after being left for 24 hours after discharge. The remaining plots are the amount of Cu in the positive electrode taken out immediately after discharge.

When the voltage was set to 0.6 V and 1.0 V, the amount of Cu in the positive electrode was 6.4 to 6.8 μg/g, and no large difference was observed regardless of the holding time. Also, the positive electrode after being held at 0 V for 360 seconds and discharged for 24 hours was 7.4 μg/g, showing no significant change. From this result, it was confirmed that the amount of Cu does not increase even if the positive electrode is not taken out immediately after discharge. In the case of 0 V, the amount of Cu increased with the holding time and was 8.5 µg/g at 360 seconds.

FIG. 4 shows the amount of Cu when the holding voltage is set to 0 V and the holding time is extended. When the holding time is 360 seconds, the amount of Cu is 8.5 μg/g (see FIG. 3). When the holding time is 3600 seconds (1 hour), the amount of Cu significantly increases to 2500 μg/g. When the holding time is 86400 seconds (24 hours), the amount of Cu increases to 3133 μg/g. The amount of Cu contained in the positive electrode after discharge is allowed as long as it is 200 μg/g (0.02% by mass) or less. To achieve a Cu content of 200 μg/g or less, the discharge time is desired to be less than 3600 seconds. The discharge time is preferably 2000 seconds or less, more preferably 1000 seconds or less, and most preferably 360 seconds or less.

In the treatment method of the present embodiment, the metallic material is obtained from the positive electrode by the thermite reaction, so the amount of Cu contained in the positive electrode is reflected in the amount of Cu contained in the metallic material. By setting the Cu content in the positive electrode before the thermite reaction to 0.02% by mass or less, the Cu content in the metal material obtained after the thermite reaction can be made 0.17% by mass or less. Specifically, 0.02% by mass of Cu is contained in the positive electrode before the thermite reaction, the composition of the lithium composite oxide is LiNiO ₂ , and the mass ratio of the current collector in the positive electrode is 30% by mass (maximum ratio ), when the mass ratio of the conductive material in the positive electrode is 30% by mass (maximum ratio) and the mass ratio of the binder is 20% by mass (maximum ratio), the Cu content in the metal material is calculated to be about 0.17% by mass. be done. In this embodiment, the mass ratio of the current collector in the positive electrode is 20% by mass, the mass ratio of the conductive material in the positive electrode is 5% by mass, and the mass ratio of the binder is 5% by mass. In this case, when the composition of the lithium composite oxide is LiNiO ₂ and 0.02% by mass of Cu is contained in the positive electrode before the thermite reaction, the Cu content in the metal material is approximately 0.05%. Calculated as % by mass. By setting the Cu content in the metal material to 0.05% by mass or less, it is possible to reuse the metal material recovered from the positive electrode of the used lithium ion battery as an electrode material for the nickel metal hydride battery. be. The recovered metal material can also be reused as a hydrogen storage metal.

In order to suppress the elution of Cu during discharge, the holding voltage is preferably 0.6 V or more, but the amount of Cu does not increase even if the voltage is less than 0.6 V for a short period of time. According to FIG. 4, when the holding voltage is 0 V, the amount of Cu in the positive electrode can be made 200 μg/g by setting the holding time within the range of 30 to 360 seconds.

FIG. 5 shows changes in current when measuring the remaining capacity after performing CC discharge to 0.6 V at a rate of 1 C, resting for 30 seconds, and then performing CV discharge for 0.6 V-30 seconds. In this case, the remaining capacity after the discharge treatment is 207 mAh, which is a charge level equivalent to that of a AA manganese battery. The remaining capacity of LiB after discharging is preferably 10% or less at a state of charge (SOC). According to this embodiment, the charge level can be reduced to at least that of a manganese AA battery. A holding voltage of 0.6 V can be discharged to the desired charge level by setting the holding time to at least 30 seconds.

Based on the above, in the present embodiment, the holding voltage and the holding time are combined so that the Cu elution amount is 0.02% by mass or less with respect to the mass of the positive electrode and the SOC is 10% or less. to discharge the used LiB.

[Cleaning inside the battery case]
Electrolytes containing fluorine (F) such as LiPF ₆ generate hydrogen fluoride (HF) when reacting with moisture in the air, causing corrosion. In order to avoid corrosion of the processing equipment for the thermite reaction to obtain the metallic material, it is preferable to sufficiently remove the electrolyte by washing.

In step SP2, the inside of the LiB battery case after discharging is washed with a predetermined washing liquid. The cleaning liquid used in the present embodiment contains a mixed solvent of a first solvent having a high ability to promote dissociation of the electrolyte in the electrolytic solution and a second solvent that reduces the viscosity of the cleaning liquid. Solvents with a large relative permittivity tend to have a high ability to promote the dissociation of electrolytes. Therefore, in this embodiment, a solvent having a dielectric constant of 30 or higher is used as the first solvent. The second solvent has a viscosity of 0.8 mPa·s or less at 25°C. The cleaning liquid preferably contains the same solvent as the non-aqueous solvent used in the LiB electrolytic solution, but may not contain it.

First solvents include, for example, cyclic carbonates and lactones. Cyclic carbonates include, for example, ethylene carbonate (EC), propylene carbonate (PC), and butylene carbonate (BC). EC has a dielectric constant of 90, PC has a dielectric constant of 65, and BC has a dielectric constant of 53. A cyclic carbonate can be used as a 1st solvent individually or in combination of 2 or more types.

Lactones include, for example, γ-butyrolactone (GBL) and methyl-γ-butyrolactone (GVL). GBL has a dielectric constant of 39 and GVL has a dielectric constant of 34. A lactone can be used as the first solvent either alone or in combination of two or in combination with a cyclic carbonate.

A chain carbonate, for example, can be used as the second solvent. Linear carbonates include, for example, dimethyl carbonate (DMC), diethyl carbonate (DEC), and ethylmethyl carbonate (EMC). DMC, DEC, and EMC have viscosities at 25° C. of 0.59 mPa·s, 0.746 mPa·s, and 0.7 mPa·s, respectively. A chain carbonate can be used as a 2nd solvent individually or in combination of 2 or more types.

Additionally, dimethoxyethylene (DME), 1,3-dioxolane (DO _x ), tetrahydrofuran (THF) or methanol (MeOH) can also be used as the second solvent. DME, DO _x , THF and MeOH have viscosities at 25° C. of 0.455 mPa·s, 0.59 mPa·s, 0.46 mPa·s and 0.529 mPa·s, respectively.

The first solvent and the second solvent can be mixed at any ratio as long as the respective properties (dissociation promoting action, low viscosity) can be maintained. The cleaning liquid is a low-viscosity liquid that promotes dissociation. For example, when EC is used as the first solvent and DMC is used as the second solvent, the first solvent and the second solvent can be mixed at a volume ratio of 30:70 to 50:50. can. EC as the first solvent and DMC as the second solvent are preferably mixed at a volume ratio of 1:1.

When cleaning the inside of the battery case, first, the safety valve is opened to depressurize the inside of the battery case, and part of the electrolyte is discharged. Next, the cleaning liquid is injected and discharged through the safety valve. When the cleaning liquid injected into the battery case is discharged, the electrolyte moves from inside the battery case to outside the battery case. By repeating the injection and discharge of the cleaning liquid, the electrolyte in the battery case can be reduced. After injecting the cleaning liquid into the battery case, it is preferable to retain the cleaning liquid for a predetermined time while irradiating ultrasonic waves of about 20 to 200 kHz before discharging. Electrolyte in the battery case can be removed more efficiently by ultrasonic irradiation.

The result of cleaning the inside of the battery case can be confirmed based on the P concentration in the cleaning liquid (recovery liquid) discharged from the battery case. Using an actual sample, changes in P concentration in the recovered liquid were investigated. The results are shown in FIG. As a sample, LiB after discharging under the above conditions was used. Since the electrolyte in LiB contains 1M LiPF ₆ and non-aqueous solvents including DMC, EMC and PC, the amount of electrolyte can be determined by the P concentration in the recovered liquid.

Using a 1:1 mixed solvent of EC and DMC as a cleaning solution, the inside of the battery case was cleaned four times. After washing, the collected liquid discharged from the battery case was analyzed by an ICP mass spectrometer (ELEMENT XR) manufactured by Thermo Fisher Scientific to determine the P concentration. FIG. 6 shows the P concentrations in the cleaning solutions (recovery solutions) discharged for the third and fourth times, as well as the ratio of the P concentrations in these two cleaning solutions.

The first to third washings were performed by injecting a washing liquid into the battery case and discharging the injected washing liquid. Ultrasonic waves were not irradiated during the first to third cleanings. The fourth cleaning was performed while irradiating ultrasonic waves (78 Hz) from the bottom surface of LiB for a predetermined time. The irradiation times of ultrasonic waves are 0, 1, 3 and 10 minutes. When the irradiation time was 0 minute, the cleaning liquid was injected into the battery case and discharged after 15 minutes to carry out the fourth cleaning.

According to FIG. 6, when ultrasonic waves are applied for one minute for cleaning, the concentration of P in the recovery liquid is 1.66 times higher than when ultrasonic waves are not applied. When the ultrasonic wave irradiation time was 10 minutes, the P concentration in the collected liquid increased 1.85 times as much as when the ultrasonic wave was not irradiated. It can be seen that the longer the ultrasonic irradiation time, the better the cleaning efficiency.

FIG. 7 shows changes in the P concentration in the recovered liquid when washing was performed under the same conditions as described above, except that only DMC was used as the washing liquid. Even when ultrasonic waves were applied for 10 minutes, the P concentration in the recovered liquid remained 1.45 times higher than when ultrasonic waves were not applied.

A comparison of FIGS. 6 and 7 shows that the electrolyte in the battery case can be efficiently removed by using a mixed solvent of EC (first solvent) and DMC (second solvent) as the cleaning liquid. Moreover, when a mixed solvent containing DMC and EC is used as the cleaning liquid, the effect of ultrasonic irradiation is improved as compared to the case of using DMC alone.

By cleaning the inside of the battery case to reduce the amount of electrolyte, problems caused by the electrolyte can be avoided. As mentioned above, the electrolyte contained in the LiB being processed is _LiPF6 , so reducing the amount of this electrolyte reduces the amount of fluorine (F) in the LiB. The generation of corrosive hydrogen fluoride (HF) is suppressed, thereby avoiding corrosion of processing equipment.

[Dismantling]
Step SP3 will be explained. After cleaning the inside of the battery case to reduce the amount of electrolyte, the LiB is dismantled to recover the positive electrode. In dismantling, first, the welded portion of the battery case is cut and the battery case is opened. The welded portion of the battery case can be cut by end milling, laser irradiation, or the like. When cutting the weld, there is little risk of damage to the battery case. Since it is possible to re-weld the cut welds, the battery case can be reused as needed.

An electrode assembly including a positive electrode and a negative electrode is taken out from the opened battery case. The electrode assembly is also in good condition as it is not damaged when cutting the battery case. The positive electrode is separated from the electrode body and collected by unwinding the wound state. The recovered positive electrode has a mass about one-tenth that of LiB, which is light and can be easily transported at a low cost. By carrying out the dismantling process at multiple satellite facilities installed close to the LiB recovery area and transporting the dismantled lightweight positive electrode to the recycling plant, it is possible to shorten the transport distance for LiB, which has a large mass. , it is possible to reduce the processing cost. The negative electrode, the separator, and the components of the battery pack included in the electrode assembly can be reused as needed.

[Thermite reaction]
Step SP4 will be explained. The positive electrode recovered from the electrode body contains Al foil as a positive electrode current collector and a lithium transition metal composite oxide as a positive electrode active material. A case where LiNi _1/6 Co _2/3 Mn _1/6 O ₂ is used as the positive electrode active material will be described as an example. In this case, the Al of the positive electrode current collector acts as a reducing agent, and the following reaction occurs. As a result of the reaction, Ni _1/6 Co _2/3 Mn _1/6 is obtained as a metallic material containing Ni and/or Co. Quicklime (CaO) is preferable as a flux for turning alumina (Al ₂ O ₃ ) into a molten slag state.
_LiNi1 / _6Co2 / _3Mn1 / ₆ +Al->1/ _{2Li2O + Ni1} / _6Co2 / _3Mn1 / ₆ +1/2Al2O3
In the present embodiment, since the metal material containing Ni and/or Co is obtained by the thermite reaction, the Al of the positive electrode current collector can act as a reducing agent, and the reducing agent can be reduced without adding a separate reducing agent. reactions can be carried out.

35.4 g of CaO as a flux is added to 100 g of the positive electrode. A metal material containing Ni and/or Co is obtained by melting the positive electrode and the flux at 1500° C. in a high-frequency melting furnace to form an alloy, followed by cooling.

A metallic material obtained by the thermite reaction is an alloy containing Ni, Co and Mn. Inevitable impurities may be contained in the alloy, but there is no particular problem. The recoveries of Ni, Co, and Mn from the positive electrode were 99.7%, 91.3%, and 94.8%, respectively. Li in the positive electrode can be separated as _Li2O .

By the processing method of the present embodiment, a metal material containing Ni, Co, and Mn, which are components of the positive electrode active material of LiB, can be obtained as an alloy. Since Ni, Co and Mn are all recovered from the positive electrode at a high recovery rate of 90% or more, the resulting metal material can be used as a raw material for hydrogen storage alloys. Since the metal material has a Cu content of 0.05% by mass or less, it is suitable as an electrode for a nickel metal hydride battery.

2. Action and Effect According to the method of the present embodiment, when treating used LiB, first, the amount of Cu eluted from the negative electrode current collector is adjusted to 0.02% by mass or less with respect to the mass of the positive electrode. Discharge. This makes it possible to reduce the residual charge of LiB while avoiding contamination of the positive electrode with Cu. Since the LiB after discharge has an SOC of 10% or less, subsequent steps can be safely performed.

After discharge, the amount of electrolyte in LiB can be reduced by cleaning the inside of the battery case with a low-viscosity cleaning liquid that promotes dissociation. The cleaning liquid contains a mixed solvent of a first solvent having a dielectric constant of 30 or less and a second solvent having a viscosity of 0.8 mPa·s or less at 25°C. Since the electrolyte in LiB can be efficiently removed by using the cleaning liquid, corrosion of the positive electrode caused by the components of the electrolyte can be suppressed. The positive electrode is in good condition with no Cu contamination and no corrosion.

The LiB positive electrode treated by the method of the present embodiment contains Ni and/or Co as valuables, and is recovered in good condition. By subjecting such a positive electrode to a thermite reaction to obtain a metallic material containing Ni and/or Co, Ni and/or Co can be efficiently and simply recovered. During discharge, the elution of Cu is suppressed to 0.02% by mass or less with respect to the mass of the positive electrode, so the Cu content in the metal material can be 0.17% by mass or less. A metallic material with a Cu content reduced to 0.05% by weight or less is suitable as an electrode for a nickel metal hydride battery.

As described above, the method of the present embodiment is performed through the steps of discharge, disassembly, and thermite reaction. In the method of the present embodiment, the positive electrode containing Ni and/or Co is alloyed alone, so a metal material containing Ni and/or Co can be efficiently obtained. The method of the present invention makes it possible to process LiB at low cost. In addition, it has the advantages of reducing energy consumption and reducing the burden on the environment. The method of the present embodiment is particularly suitable for processing spent automotive LiB.

The metal material of the present embodiment obtained from LiB by such treatment contains valuables (Ni and/or Co) that are components of the positive electrode active material. Moreover, since the metal material of the present embodiment has a Cu content of 0.05% by mass or less, it can be effectively used as an electrode of a nickel metal hydride battery.

3. Modifications The present invention is not limited to the above-described embodiments, and can be modified as appropriate within the spirit and scope of the present invention.

In the above embodiment, graphite was used as the negative electrode active material contained in the negative electrode of LiB to be processed, but any negative electrode active material generally used for LiB can be used. Examples of usable negative electrode active materials include carbon materials such as amorphous carbon, Si-based materials, and lithium-titanium composite oxides.

Aprotic solvents such as esters, ethers, nitriles, sulfones, and lactones may be used as the non-aqueous solvent contained in the electrolytic solution.

The cleaning liquid used for cleaning the inside of the battery case may further contain a third solvent as long as the dissociation promoting action and low viscosity are not impaired. Examples of the third solvent include well-known solvents and additives. The ratio of the third solvent to the entire detergent is preferably 20% by mass or less, more preferably 10% by mass or less, and particularly preferably 5% by mass or less. A mixed solvent can be prepared by mixing the first solvent and the second solvent in an arbitrary ratio according to their types.

In the above embodiment, the metal material containing Ni and/or Co is obtained from the positive electrode recovered by the thermite reaction. Metal material can be obtained. For example, a metallic material containing Ni and/or Co can be obtained by mixing the collected positive electrode and a reducing agent, melting the mixture in a melting furnace to form an alloy, and then cooling the mixture.

Claims (4)

A positive electrode comprising a positive electrode current collector and a positive electrode active material layer containing, as a positive electrode active material, a positive electrode active material composed of a lithium transition metal composite oxide containing Ni and/or Co as a main component; and a negative electrode current collector containing Cu. A method for recycling a lithium ion battery in which a negative electrode having a negative electrode active material layer and an electrolyte are housed in a battery case,
a step of disassembling the lithium ion battery and recovering the positive electrode;
a step of obtaining the metal material containing Ni and/or Co as an alloy from the recovered positive electrode;
with
The step of obtaining the metal material as an alloy includes using Al contained in the positive electrode current collector as a reducing agent,
The metal material has a Cu content of 0.05% by mass or less, and is used as a metal material for a nickel metal hydride battery without being separated and purified. processing method. 2. The method for recycling lithium ion batteries according to claim 1, wherein the step of obtaining the metal material as an alloy uses a thermite reduction reaction or a smelting reduction reaction. A step of discharging the lithium ion battery so that the Cu elution amount is 0.02% by mass or less with respect to the mass of the positive electrode before the step of collecting the positive electrode. 3. The method for recycling lithium ion batteries according to claim 1 or 2. The lithium ion battery recycling method according to any one of claims 1 to 3, wherein the lithium ion battery is an automobile battery.

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