KR20000019850A - Method for recycling exhausted lithium secondary battery - Google Patents

Abstract

PURPOSE: A method for recycling an exhausted lithium secondary battery is provided to recycle an exhausted lithium secondary battery by separating and extracting materials of the secondary battery. CONSTITUTION: A method for recycling an exhausted lithium secondary battery(S1) is followed below. A positive pole and a negative pole are separated from a lithium secondary battery, exhausted by a classification, a cutting of upper/lower section, centrifuging, and a handling classification. A mixture of an activating material, a conductive material, and a binding agent, which are cleared a current collector, is separated from the positive/negative poles by a dissolution of the binding agent, a stirring, a filtering, and a heat separation, and cutting. A positive pole activating material is separated from the mixture, and binds the positive activating material and a lithium, and processes by a heat. A separated positive activating material is processed electronically/chemically.

Description

Recycling of Discarded Lithium Secondary Batteries.

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a recycling method of a rechargeable lithium secondary battery that is in the spotlight as a mobile direct current power supply and a backup power supply.

More specifically, each component material is separated and extracted from the positive electrode / negative electrode of the discarded lithium secondary battery and the lithium secondary battery that is discarded due to poor performance during manufacturing, in a highly efficient manner, and among them, a battery can and a lithium-based positive electrode active material. The present invention relates to a method for treating a positive electrode current collector and a negative electrode current collector so as to be recycled for the battery industry and other uses.

In the "disposed lithium secondary battery" of the present invention, in addition to the lithium secondary battery that is discarded after being used for a mobile DC power supply or a backup power supply, a defective lithium secondary battery that is discarded or stored before being shipped to the market due to insufficient performance by a battery manufacturer. Included.

Generally, lithium secondary batteries contain a water-insoluble electrolyte and are manufactured using lithium-based oxides containing expensive cobalt as a positive electrode active material. Recently, with the trend toward miniaturization, light weight, and high performance of portable electronic devices, the demand for lithium secondary batteries having high density energy in terms of unit volume and unit weight is rapidly increasing. However, as described above, the lithium secondary battery uses a lithium oxide containing expensive cobalt as a positive electrode active material and an electrolyte based on lithium salt, an organic carbonate based solution, a lactone based solution, a formate solution, Due to the use of ester-based solutions or mixtures of these, disposal of landfills like other batteries is not only in line with the intention of recycling resources around the world in terms of the high cost of constituent materials. There is a risk of causing.

At present, a method of extracting only the positive electrode active material having the largest specific gravity of constituent material per cell from acid batteries and treating it with acid is known. However, such a method is not commercialized due to complicated processes and excessive cost. I can't do it.

Separation, extraction, and reprocessing of components from waste lithium secondary batteries require process operation and control techniques that must recover more than 90% of environmentally hazardous substances safely and inexpensively, and reliably restore recyclable materials. Advanced reprocessing techniques are required. In particular, the reprocessing technology of the positive electrode active material, which is considered as the most important technology in relation to the present invention, is to remove the impurity film formed on the surface of the active material, and to recharge the lithium ions according to the change in the chemical composition ratio of the active material, There is a need for advanced powder control and composition control techniques such as restoration, control of particle size and distribution.

Accordingly, an object of the present invention is to provide an optimized process in terms of safety, cost, and yield in separating, extracting, and reprocessing constituent materials of a discarded lithium secondary battery. It is another object of the present invention to extract a high value-added positive electrode active material and then efficiently reprocess it to restore the charge and discharge characteristics of a level that can be reused as a positive electrode of a lithium secondary battery. In addition, the positive electrode / negative electrode current collector and the battery can is efficiently collected and molded into an application and then used for other industries including the battery industry. Another object of the invention is to quickly and safely collect and dispose of an electrolyte solution which may cause soil contamination.

Each component of the discarded lithium secondary battery can be safely separated and extracted at low cost and high yield, and the charge and discharge characteristics of the extracted cathode active material can be restored to a high level that can be recycled to the cathode of the lithium secondary battery. The present invention provides a method for recycling a discarded lithium secondary battery.

1 is a process schematic diagram of the present invention.

FIG. 2 is an electron scanning microscope (SEM) photograph of a positive electrode active material (LiCoO ₂ ) regenerated by treatment of a discarded lithium secondary battery (18650, manufactured by Sony Corporation, Japan) by the method of the present invention.

3 is an electron scanning microscope (SEM) photograph of a positive electrode active material (LiCoO ₂ ) of a lithium secondary battery (Sumitomo Mining Co., Ltd.) before use.

* Explanation of symbols on the main parts of the drawings

1.Charge Discharger S1: Waste Lithium Ion Battery

2. Sorter S2: Lithium Raw Material

3. Upper lower cutter P1: Battery can

4. Centrifuge P2: Electrolyte Solution

5. Manual Sorting Process P3: Membrane and Other Interior Parts

6. Cutter P4: positive electrode, negative electrode current collector

7. Stirrer P5: washed positive electrode active material

8. Filter classifier P6: positive electrode active material

9. Thermal separator

10. Condenser A: First Separation Process

11.Vacuum device B: second separation process

12. Cutter C: Refilling Process of Positive Electrode Active Material

13. Atmosphere

14. Mixer

15. Atmosphere

16. Crushing Classifier

17. Electrochemical Filling Process

18. Performance Evaluation Test Process

The present invention relates to a method for recycling a discarded lithium secondary battery.

More specifically, the present invention relates to a method for recycling a discarded lithium secondary battery, characterized by the following process steps.

-Below-

[Iii] A first separation process in which a cathode and an anode are separated from a lithium secondary battery discarded by sorting, top and bottom cutting, centrifugation, and manual sorting, and then cut, [ii] binder dissolution, stirring, filtering, and thermal separation. And a second separation step of separating a mixture of the active material, the conductive material, and the binder from which the current collector has been removed from the positive electrode and the negative electrode by the cutting operation, and [iii] firing treatment to prepare the positive electrode active material from the mixture of the active material, the conductive material, and the binder. After the separation, the positive electrode active material and the lithium raw material are mixed, followed by heat treatment or recharging of the positive electrode active material which electrochemically treats the separated positive electrode active material.

Hereinafter, the present invention will be described in detail with reference to the drawings.

1 is a process schematic diagram of the present invention.

The waste battery discharged sufficiently by the waste battery (S1) or the charge-discharger (1) is moved along the tray to which the battery body is fixed from the side through a sorter (2) classified by producer, production year, size and shape. Then, the upper and lower cutters 3 separate the battery can P1 and the battery contents.

The sorter 2 may directly supply the discarded lithium secondary battery S1, or may supply the waste lithium secondary battery sufficiently discharged by the charge-discharger 1. The constant current at the time of discharge in the charge-discharger 1 is preferably adjusted to 0.5 mA / cm 2 or less and the voltage range is 2.0 to 4.0V. In addition, the discarded lithium secondary battery may be a discarded battery after use, or may be a poor performance battery generated in the manufacturing process. After the separation, the collected battery cans are formed into an application form through a heat treatment process, and the battery contents are moved to the centrifuge 4 along the tray. In the centrifuge the electrolyte (P2) is separated by more than 90% with some powder. At this time, the rotation speed of the centrifuge is preferably 100rpm or more. The use of a centrifuge for separation of electrolytes takes into account the safety of the operator in the subsequent manual work (5).

If you want to extract only electrolyte solution to prevent environmental pollution due to electrolyte solution, put the collected waste battery directly into liquid nitrogen and let it remain for at least 1 minute, take it out immediately and crush it by using a compactor. Use only, extract the electrolyte. At this time, the reason for putting the waste battery in the liquid nitrogen is to prevent the safety accidents caused by the activity of those that remain in a completely discharged state of the collected waste batteries, and to ensure that they break well when pressed.

On the other hand, the positive electrode and the negative electrode of the battery contents from which the electrolyte is removed by the centrifuge are separated by hand 5, and the separator and other internal parts P3 are collected and discarded. The separated positive electrode and the negative electrode are cut to a size of 4 cm 2 or less by using the cutter 6 in order to increase the efficiency of the work in the current collector separation process using a solvent to be described later. For convenience, the separation process thus far is referred to as a first separation process.

The positive electrode and the negative electrode separated through the first separation process are composed of an active material, carbon used as a conductive material, a binder for mechanically connecting the two materials and bonding the current collector, and a current collector. Looking at the constituent materials, as the positive electrode active material, LiCoO ₂ or LiMn ₂ O ₄ without addition or addition of metal components such as Ni, V, Cr, Fe, and Al is used, and as the negative electrode active material, a carbon-based material or a graphite-based material is used. A material is used, and polyvinylidene fluoride is used for both a positive electrode and a negative electrode, an aluminum film is used for the positive electrode collector, and a copper film is used for the negative electrode collector.

In the first separation process, the positive electrode and the negative electrode cut to 4 cm 2 or less are introduced into the stirrer 7. In the stirrer 7, a solvent capable of dissolving the binder is injected at a 5: 1 or more relative to the weight of the electrode.

When the positive electrode and negative electrode pieces introduced into the stirrer 7 are stirred for 10 minutes or more, the binder is dissolved and the active material and the conductive material are separated from the current collector. At this time, the solvent is dimethylformamide, dimethylracetamide, acetone, tetrahydrofuran, methyl ethyl ketone, N- methyl phyllolidon, isophorone, dioxane, methyl isobutyl ketone, cyclohexanone, diacetone alcohol, Sealane or a mixture thereof is used. Through the bottom of the stirrer, the solution including the current collector enters the filter separator 8 and the current collector is collected in a movable mesh having a size of 3 mm or less installed therein. The filtering driving force in the filter separator is then provided through a pneumatic pump attached to the top of the filter separator 8. The pressure pump is equipped with a pressure measuring device so that when the current collector is collected from the mesh to prevent the flow of the solution, the pressure rises above a certain level, thereby informing the mesh replacement point.

As a feature of the present invention, when the mesh is replaced, the solution including the current collector from the stirrer 7 is no longer injected into the filter separator 8 by returning back to the stirrer 7 by immediately operating the dipole valve. The concentrated solvent from the condenser 10 is sprayed through the bipolar valve to the filter separator and designed to first wash the collected current collector. The separated current collector P4 is secondly washed using the same kind of solvent injected into the stirrer 7, and is formed into an applied form through a heat treatment process.

After the first separation step, the steps up to here are the current collector separation process between the positive electrode and the negative electrode, and the following technique corresponds only to the separation and reprocessing process of the positive electrode active material. From the filter separator 8 the solution containing the positive electrode active material, the conductive material and the binder in the dissolved state enters the thermal separator 9. The solvent in the solution injected into the heat separator 9 operating at 150 ° C. or higher rapidly evaporates and is collected in the liquid phase in the condenser 10 by the vacuum device 11, recycled to the stirrer 7, and the filter separator 8. ) Can also be used as a cleaning liquid to clean the current collector. At the lower end of the heat separator 9, a mixture of the concentrated binder, the conductive material and the active material is extracted to the outside through the sludge pump and cut to a predetermined size through the cutter 12. The process up to here after the 1st separation process is called a 2nd separation process for convenience.

The mixed sludge of the binder, the conductive material, and the active material, which has undergone the second separation process, is calcined at 300 to 500 ° C. for 5 to 20 hours in an atmosphere furnace 13 having an oxygen atmosphere of 0.5 to 1 atmosphere, whereby the conductive material and the binder are oxidized and the positive electrode Only the active material remains. The extracted positive electrode active material is washed two or more times using ultra sonic with alcohol and secondary distilled water to remove lithium-based impurities. Since the waste batteries are not in a completely discharged state, the chemical composition ratio of the washed positive electrode active material P5 is in a state in which Li is lacking with respect to the original composition ratio. Therefore, in order to restore the battery positive electrode active material, lithium ions must be refilled into the crystal structure of the active material.

In the present invention, lithium ions are recharged into the crystal structure of the positive electrode active material P5 separated by the following two methods.

First, a common heat treatment method in which a lithium raw material (S2) is mixed with a washed positive electrode active material (P5) and then calcined. First, 0.5 to 2 moles of lithium raw materials are mixed in the mixer 14 in excess of 1 mole of the positive electrode active material so that lithium ions can be sufficiently filled into the crystal structure of the positive electrode active material during firing. Lithium carbonate, lithium nitrate, lithium hydroxide, lithium oxide, lithium acetate, lithium chloride, lithium citrate and the like can be used as a raw material for lithium. Thereafter, the mixture was first calcined for 1 to 50 hours at a temperature of 300 to 500 ° C. in an atmosphere furnace 15 having an oxygen atmosphere of 0 to 1 atmosphere, and the temperature was further raised to 500 to 900 ° C. for 2 to 20 hours. Fire. The rate of temperature change per hour at the time of temperature rise and temperature fall shall be 10 degrees C / min or less. During secondary firing, the sample may be intermittently taken out and pulverized and then refired. The calcined positive electrode active material is washed with secondary distilled water and ultra sonic, and lithium-based impurities derived from excessive lithium raw materials are removed in this process. Then, the positive electrode active material P6 classified into a predetermined size through the grinding classifier 16 is manufactured as an electrode and undergoes a performance evaluation test 18.

X-ray diffraction and Fourier Switched Infrared Spectroscopy (FTIR) were used to examine the samples before and after the washing, and it was confirmed that impurities from the excessive lithium raw materials were removed after washing. The washed samples were sorted to a certain size by crushing and classifying, and the crystal structure, shape, and chemical composition ratio were investigated by X-ray diffractometer, electron scanning microscope, and atomic adsorption spectroscopy. It was found that the primary firing was carried out at 450 DEG C for 10 hours under an oxygen 100% atmosphere, and then secondary firing at 650 DEG C for 5 hours. Acetylene black is used as the conductive material of the electrode prepared for the performance evaluation test, and polyvinylidene fluoride is used as the binder. For example, the electrode is made of 84% by weight of the restored positive electrode active material LiCoO ₂ , 10% by weight of acetylene black as a conductive material, and 6% by weight of polyvinylidene fluoride as a binder. For the performance evaluation test, an electrochemical cell employing a solution obtained by dissolving lithium metal as a negative electrode and 1 mol of lithium salt in an organic carbonate mixture as an electrolyte is used. In this case, as the organic carbonate-based mixture used as an electrolyte, a mixture of ethylene carbonate and dimethyl carbonate in a volume ratio of 1: 1 is used. The coefficient of performance of the positive electrode active material LiCoO ₂ restored by the method of the present invention is about 86% of that of the positive electrode active material LiCoO ₂ (Sumitomo Mining Products) before use. The coefficient of performance of the positive electrode active material is measured by the following equation.

Coefficient of Performance =

The second method provides a method of electrochemically recharging lithium ions. According to this method, the cleaned positive electrode active material P5 is directly manufactured as an electrode without undergoing a heat treatment method. The manufacturing method of the electrode is the same as the heat treatment method described above. For the electrochemical filling 17, a lithium metal is used as a negative electrode and 0.5 to 3 mol of a lithium salt is dissolved as an electrolyte, an organic carbonate solution, a lactone solution, a formate solution, an ester solution, or a mixture thereof. An electrochemical cell using a mixed solution is used. One charge and discharge charges lithium ions. In this case, the discharge constant current is very slow at a discharge time of 0.1 mA / cm 2 or less so that lithium ions in the electrolyte can be sufficiently diffused into the crystal structure of the active material. It is preferable that the voltage range at the time of charge and discharge shall be 2.0-4.0V. The first method and the second method described above may be performed separately or simultaneously.

Hereinafter, the present invention will be described in detail through Examples and Comparative Examples. However, the present invention is not limited only to the following examples.

Example 1

Ten collected lithium secondary batteries of Sony's 18650 size, Japan, were cut in a cutting machine equipped with a rotary saw blade and separated into battery cans and battery contents. The yield of the isolated battery can was 91% of the original volume. The battery contents were placed in a centrifuge rotating at 200 rpm to extract about 90% of the electrolyte with some active material and conductive material. The positive electrode and the negative electrode of the battery contents from which the electrolyte was removed by the centrifuge were separated by hand, and cut into an average size of 1 cm 2 using a cutter. Cut the positive electrode and the negative electrode pieces into each of the stirrers in which a solution containing acetone and N-methylpyrrolidone in a 1: 1 weight ratio (binder dissolving solution) was injected at a ratio of 10: 1 to the weight of the electrode. By stirring for a minute to dissolve the binder, the active material and the conductive material are separated from the current collector. The current collector was collected by sieving a solution including a current collector with a 2 mm sieve, and the collected current collector was washed with a mixed solution of acetone and N-methylpyrrolidone mixed in a 2: 1 weight ratio. Final yields of the washed positive electrode and the negative electrode current collector were 91% and 92%, respectively. The separated solution is dried in an oven connected to a condenser, a vacuum device and a collector. At this time, the drying temperature is 180 ℃. The yield of collected solvent was 74%. Higher yields are expected when introducing closed automated processes. The mixture of the concentrated binder, the conductive material and the active material is calcined at 450 ° C. for 20 hours under an atmosphere of 98% oxygen to oxidize the conductive material and the binder and detect only the positive electrode active material. The extracted positive electrode active material is washed twice with Ultrasonic with alcohol and secondary distilled water. X-ray diffraction (XRD) of the washed positive electrode active material showed the same crystal structure as LiCoO ₂ . In addition, it was confirmed that lithium ions were deficient in the crystal structure when the peak positions and intensities of the (003) plane were compared with those of the (104) plane. As a result of investigating the composition ratio of the metal components with the atomic absorption spectrometer (AA), it was found that Li: Co = 0.68: 1. In order to recharge lithium ions, a mixture is prepared by mixing 0.8 mol of lithium hydroxide with respect to 1 mol of the positive electrode active material. Subsequently, these mixtures were first calcined at a temperature of 450 ° C. for 10 hours under an oxygen atmosphere of 0.5 to 1 atmosphere, and then further calcined at 5 ° C. for 5 hours. The temperature change rate per hour at the time of temperature increase and temperature fall is adjusted by 5 degree-C / min. During the second firing, the sample was taken out during the firing, pulverized, and then refired once. The calcined samples were washed with distilled water and ultrasonic. X-ray diffraction and Fourier Switched Infrared Spectroscopy (FTIR) were used to examine the samples before and after the washing, and it was confirmed that impurities from the excessive lithium raw materials were removed after washing. An electrode composed of 84% by weight of the restored positive electrode active material LiCoO ₂ , 10% by weight of acetylene black as a conductive material, and 6% by weight of polyvinylidene fluoride as a binder was prepared for the performance evaluation test. For the electrochemical experiment, an electrochemical cell using a mixture of ethylene carbonate / dimethylmethyl carbonate (volume ratio = 1: 1) in which lithium metal is dissolved as a negative electrode and 1 mol of LiPF ₆ is dissolved as an electrolyte is used. All assembly work is done in a dry room to prevent contamination by moisture. The constant current used for charge and discharge is 0.1mA / cm 2, the voltage range is 4V, and the number of charge and discharge is 50 times. In addition, after manufacturing and testing the electrode of Sumitomo Mining Co., Ltd. LiCoO ₂ in Japan, the coefficient of performance was calculated and the coefficient of performance of the positive electrode active material LiCoO ₂ whose capacity and lifespan characteristics were restored by the present invention was Sumitomo Mining. It was about 86% compared to the positive electrode active material LiCoO2.

Example 2

The washed positive electrode active material of Example 1 is directly prepared as an electrode without undergoing a heat treatment method. The constituent material and the weight ratio of the electrode are the same as in Example 1. For electrochemical filling, use an electrochemical cell with a mixture of ethylene carbonate / dimethylmethyl carbonate (volume ratio = 1: 1) in which lithium metal is dissolved as a negative electrode and 2 mol of LiPF ₆ as an electrolyte. Perform on Charge and discharge constant current is 0.1mA / ㎠, 0.02mA / ㎠, voltage range is 3.5V, and the number of charge and discharge cycles is one. As a result of investigating the metal composition ratio of the positive electrode active material after the electrochemical filling was performed by adsorption spectroscopy, Li: Co = 0.91: 1, which was close to the metal composition ratio (Li: Co = 0.98: 1) of the positive electrode active material of Sumitomo Mining before use. It was confirmed that the ions were efficiently recharged.

Example 3

After collecting the positive electrode active material under the same conditions and processes as in Example 1, except that the collected waste lithium secondary battery was discharged to the lowest 0V using the charge-discharger 1 before being introduced into the sorter 2, Secondary firing treatment. The atomic ratio spectroscopy of the calcined positive electrode active material was examined by atomic adsorption spectroscopy to confirm that lithium ions were efficiently recharged with Li: Co = 0.9: 1.

Example 4

Electrochemical charging after extracting the positive electrode active material under the same conditions and processes as in Example 2, except that the collected waste lithium secondary battery was discharged to the lowest 0V using the charge-discharger 1 before being introduced into the sorter 2. Process. As a result of investigating the composition ratio of the metal component of the positive electrode active material in which the electrochemical charging was completed, it was confirmed that lithium ions were efficiently recharged with Li: Co = 0.9: 1.

The present invention can be safely separated and extracted more than 90% of the electrolyte solution from the discarded lithium secondary battery to prevent soil contamination even when disposed of landfill. In addition, the present invention can separate and extract the battery can, the positive electrode current collector and the negative electrode current collector at low cost and high yield (85% or more), so that they can be recycled to the battery and industrial. In addition, the present invention can be separated and extracted more than 70% of the positive electrode active material, it is possible to restore their charge and discharge characteristics to a high level that can be recycled to the positive electrode of the lithium secondary battery. The positive electrode active material restored by the present invention has a coefficient of performance of 85% or more as compared with a commercial positive electrode active material.

Claims (10)

Method for recycling the discarded lithium secondary battery, characterized in that consisting of the following process steps. -Below- [Iii] A first separation process in which a cathode and an anode are separated from a lithium secondary battery discarded by sorting, top and bottom cutting, centrifugation, and manual sorting, and then cut, [ii] binder dissolution, stirring, filtering, and thermal separation. And a second separation step of separating a mixture of the active material, the conductive material, and the binder from which the current collector has been removed from the positive electrode and the negative electrode by the cutting operation, and [iii] firing treatment to prepare the positive electrode active material from the mixture of the active material, the conductive material, and the binder. After the separation, the positive electrode active material and the lithium raw material are mixed, followed by heat treatment or recharging of the positive electrode active material which electrochemically treats the separated positive electrode active material. The method for recycling the discarded lithium secondary battery according to claim 1, wherein the lithium secondary battery is electrochemically charged and discharged prior to the sorting operation of the first separation process. The method for recycling the discarded lithium secondary battery according to claim 2, wherein the constant current during discharge is 0.5 mA / cm 2 or less and the voltage range is 0.2 to 4.0V. The method for recycling the discarded lithium secondary battery according to claim 1, wherein the discarded lithium secondary battery is a used lithium secondary battery or a lithium secondary battery which is defective in a manufacturing process. The method of claim 1, wherein a centrifugal separator of 100 rpm or more is used in the centrifugation operation during the first separation process. The method of claim 1, wherein during the recharging process of the positive electrode active material, the mixture of the active material, the conductive material, and the binder is calcined at 300 to 500 ° C. for 5 to 20 hours under an oxygen atmosphere of 0.5 to 1 atm. Method of recycling. The method of claim 1, wherein the positive electrode active material and the lithium raw material mixture separated during the recharging process of the positive electrode active material are first calcined at 300 to 500 ° C. for 1 to 50 hours under an oxygen atmosphere of 0.5 to 1 atmosphere, and then the temperature is 500 to 900. A method of recycling a discarded lithium secondary battery, characterized in that the secondary firing treatment for 1 to 20 hours by raising to ℃. The method of recycling the discarded lithium secondary battery according to claim 7, wherein the temperature change rate at the time of temperature increase or temperature decrease is 10 ° C / min or less. The method for recycling a discarded lithium secondary battery according to claim 1 or 7, wherein the lithium raw material is lithium carbonate, lithium nitrate, lithium hydroxide, lithium oxide, lithium acetate, lithium chloride or lithium citrate. The method of claim 1, wherein when the separated positive electrode active material is electrochemically recharged, the negative electrode is lithium metal, the electrolyte is 0.5-3 mol mol of lithium salt, organic carbonate solution, lactone solution, formate solution, A method of recycling a discarded lithium secondary battery, characterized by using an electrochemical cell which is an ester solution or a mixture thereof.