METHOD AND SYSTEM FOR SEPARATING CATHODE MATERIAL OF WASTE LITHIUM SECONDARY BATTERY USING OXIDATION REACTION OF ANODE MATERIAL AND REDUCTION REACTION OF CATHODE MATERIAL

Abstract

Proposed are a method and a system for separating a cathode material of a waste lithium secondary battery using an oxidation reaction of an anode material and a reduction reaction of the cathode material. When lithium is heated to a level where lithium can undergo an explosive reaction using the low-temperature pyrolysis system, the binder, the electrolyte, and the separator contained in the waste lithium secondary battery are gasified into syngas by the explosive reaction of lithium and the resulting syngas is removed. The reduction reaction of the cathode material and the oxidation reaction of the anode material are promoted by the continuous explosive reaction of lithium and the stirring action of the spiral. As a result, the black powder and the current collector mixture are extracted. Therefore, it is possible to improve the recovery rate of valuable metals to more than 97%, thereby improving recycling efficiency.

Claims

1. A method of separating a cathode material of a waste lithium secondary battery using an oxidation reaction of an anode material and a reduction reaction of the cathode material, the method recovering cathode active materials (Co, Ni, and Mn) from black powder in which raw materials (Co, Ni, Mn, Li, and C) for the cathode and anode materials are mixed, the method comprising: (a) introducing a waste lithium secondary battery scrap into a low-temperature pyrolysis furnace (110) of the low-temperature pyrolysis system, sealing inside of the low-temperature pyrolysis furnace (110), rotating and heating the low-temperature pyrolysis furnace (110) to a temperature at which an explosive reaction of lithium occurs (S10); (b) stopping the heating of the low-temperature pyrolysis furnace (110) when the low-temperature pyrolysis furnace (110) reaches a predetermined temperature, causing the explosive reaction of lithium contained in the waste lithium secondary battery scrap, inducing an increase in internal temperature of the low-temperature pyrolysis furnace (110) by allowing the explosive reaction of lithium to continue while continuously rotating the low-temperature pyrolysis furnace (110), and gasifying an electrolyte, a separator, and a binder separated from the waste lithium secondary battery scrap and discharging the resulting syngas to outside of the low-temperature pyrolysis furnace (110) (S20); (c) preparing the black powder so that the cathode actives materials (Co, Ni, and Mn) of the cathode material recover magnetism (or ferromagnetism) by reducing the cathode material through an oxidation-reduction reaction between the cathode material and the anode material in the black powder (S30); (d) extracting the black powder and a current collector mixture (Cu and Al) and transferring and discharging the black powder and the current collector mixture to outside of the low-temperature pyrolysis furnace (110) (S40); and (e) performing a magnetic separation process to separate the black powder into the cathode active materials (Co, Ni, and Mn) moved in the direction of a magnetic force and an anode active material (C) moved in the opposite direction of the magnetic force (S50).

2. The method of claim 1, wherein in step (c), under constant temperature and pressure conditions, the following Chemical Formula 1 is used,
Chemical Formula 1: Li(Ni.sub.xCo.sub.yMn.sub.z)O.sub.2+2C=Li+xNi+yCo+zMn+2CO.

3. The method of claim 1, wherein in step (a), a surface temperature of the low-temperature pyrolysis furnace (110) is maintained at 120° C. to 200° C., and an internal temperature of the low-temperature pyrolysis furnace (110) is maintained at 140° C. to 300° C.

4. The method of claim 1, wherein in step (a), the low-temperature pyrolysis furnace (110) is heated to the temperature at which the explosive reaction of lithium occurs for 1 to 4 hours using an electric heating device (130); and in step (b), power of the electric heating device (130) is cut off, and the binder, the electrolyte, and the separator are gasified for 2 to 8 hours and discharged as the temperature is continuously increased due to occurrence of the explosive reaction of lithium.

5. The method of claim 1, wherein in step (c), the temperature is continuously increased due to the explosive reaction of lithium, and the reduction reaction of the cathode material and the oxidation reaction of the anode material are simultaneously performed for 10 to 18 hours through a stirring action by rotation of a spiral (140) installed inside the low-temperature pyrolysis furnace (110).

6. The method of claim 1, wherein the low-temperature pyrolysis furnace (110) is rotated in a predetermined direction in steps (a), (b), and (c), and the low-temperature pyrolysis furnace (110) is rotated in the opposite direction in step (d).

7. A method of separating a cathode material of a waste lithium secondary battery using an oxidation reaction of an anode material and a reduction reaction of the cathode material, the method recovering cathode active materials (Co, Ni, and Mn) from black powder in which raw materials (Co, Ni, Mn, Li, and C) for the cathode and anode materials are mixed, the method comprising: introducing a waste lithium secondary battery scrap into a low-temperature pyrolysis furnace (110) of a low-temperature pyrolysis system (100): and extracting the black powder and a current collector mixture (Cu and Al) by causing an explosive reaction of lithium contained in a waste lithium secondary battery scrap, wherein the cathode material is reduced through an oxidation-reduction reaction between the cathode material and the anode material in the black powder so that the cathode active materials (Co, Ni, and Mn) recover magnetism (or ferromagnetism), after which a magnetic separation process is performed to separate the black powder into the cathode active materials (Co, Ni, and Mn) moved in the direction of a magnetic force and an anode active material (C) moved in the opposite direction of the magnetic force.

8. A system for separating a cathode material of a waste lithium secondary battery using an oxidation reaction of an anode material and a reduction reaction of the cathode material, the system recovering cathode active materials (Co, Ni, and Mn) from black powder in which raw materials (Co, Ni, Mn, Li, and C) for the cathode and anode materials are mixed, the system comprising: a low-temperature pyrolysis furnace (110) rotatably supported on a base frame (1), and configured to heat and gasify a binder, an electrolyte, and a separator, which are organic compounds contained in a waste lithium secondary battery scrap, inside the low-temperature pyrolysis furnace (110) into syngas, remove the resulting syngas, and extract the black powder and a current collector mixture (Cu and Al), the low-temperature pyrolysis furnace having an annular flange (F) extended at each of front and rear ends thereof, an inlet (112) formed at the front end thereof and into which the waste lithium secondary battery scrap is introduced, and a closed space (113) formed therein; a low-temperature pyrolysis furnace rotation module (120) configured to rotate the low-temperature pyrolysis furnace (110) in a predetermined direction or in the opposite direction; an electric heating device (130) fixedly installed on the base frame (1) to surround an outside of the low-temperature pyrolysis furnace (110), and configured to heat the low-temperature pyrolysis furnace (110); a spiral (140) installed inside the low-temperature pyrolysis furnace (110), and configured to stir the waste lithium secondary battery scrap and the black powder and to promote the reduction reaction of the cathode material and the oxidation reaction of the anode material; a bucket (150) fixedly installed on an inner wall of the low-temperature pyrolysis furnace (110) and configured to extract the black powder and the current collector mixture; a screw conveyor (160) installed horizontally at the rear end of the low-temperature pyrolysis furnace (110), with an end being inserted into the low-temperature pyrolysis furnace (110), and configured to transfer the black powder and the current collector mixture; a syngas storage tank (170) connected to the screw conveyor (160) and a syngas discharge connection pipe (171) and configured to store the syngas discharged from the low-temperature pyrolysis furnace (110); a main hopper (180) configured to store the black powder and the current collector mixture extracted by the low-temperature pyrolysis furnace (110); and a magnetic separator (190) configured to separate the black powder into the cathode active materials (Co, Ni, and Mn) moved in the direction of a magnetic force and an anode active material (C) moved in the opposite direction of the magnetic force.

9. The system of claim 8, wherein an insulating material (114) is installed on an outer periphery of the electric heating device (130) to prevent heat loss during low-temperature pyrolysis of the waste lithium secondary battery scrap.

10. The system of claim 8, wherein the low-temperature pyrolysis furnace rotation module (120) comprises: a support roller (121) rotatably supporting a lower outer peripheral surface of each of the respective flanges (F) of the low-temperature pyrolysis furnace (110); a ring gear (122) installed on an outer periphery of the flange (F) at the rear end of the low-temperature pyrolysis furnace (110); a pinion gear (123) fixedly installed on the base frame (1) to be meshed with the ring gear (122); and a reduction geared motor (124) fixedly installed on the base frame (1) and configured to rotate the pinion gear (123).

11. The system of claim 10, wherein the ring gear (122) and the respective support rollers (121) are installed to be spaced apart from the low-temperature pyrolysis furnace (110) to minimize heat conduction.

12. The system of claim 10, wherein the electric heating device (130) is installed to surround the entire outer peripheral surface of the low-temperature pyrolysis furnace (110), and the electric heating device (130) is configured to be in close contact with the outer peripheral surface of the low-temperature pyrolysis furnace (110) or to be spaced apart a predetermined gap (G) from the outer peripheral surface of the low-temperature pyrolysis furnace (110).

13. The system of claim 8, wherein the syngas generated as a result of heating and the explosive reaction of lithium in the low-temperature pyrolysis furnace (110) is introduced into the syngas storage tank (170) through the syngas discharge connection pipe (171) in a state in which a pressure of the low-temperature pyrolysis furnace (110) is higher than atmospheric pressure, and then is compressed and stored in the syngas storage tank (170) by a vacuum pump (172).

14. The system of claim 8, wherein the screw conveyor (160) comprises: a transfer screw (161) configured to transfer the black powder and the current collector mixture; a transfer pipe (162) having a transfer screw (161) therein, an inlet (162a) at a front end thereof, and an outlet (162b) at a lower portion thereof; a transfer screw driving motor (163) configured to rotate the transfer screw (161); and an opening/closing valve (164) installed at the outlet (162b).

15. The system of claim 14, wherein the inlet (162a) is formed at an upper side of the front end of the transfer pipe (162), the spiral (140) moves the black powder and the current collector mixture toward the screw conveyor (160) when the low-temperature pyrolysis furnace (110) is rotated, and the bucket (150) introduces the black powder and the current collector mixture into the inlet (162a) while being moved from bottom to top inside the low-temperature pyrolysis furnace (110) when the low-temperature pyrolysis furnace (110) is rotated.

16. A system for separating a cathode material of a waste lithium secondary battery using an oxidation reaction of an anode material and a reduction reaction of the cathode material, the system recovering cathode active materials (Co, Ni, and Mn) from black powder in which raw materials (Co, Ni, Mn, Li, and C) for the cathode and anode materials are mixed, the system comprising: a low-temperature pyrolysis furnace (110) having an inlet (112) into which a waste lithium secondary battery scrap is introduced, and a closed space (113) formed therein; an electric heating device (130) installed on an outside of the low-temperature pyrolysis furnace (110), and configured to heat the low-temperature pyrolysis furnace (110); a screw conveyor (160) installed at a rear end of the low-temperature pyrolysis furnace (110) and configured to transfer the black powder and the current collector mixture; and a magnetic separator (190) configured to separate the black powder into the cathode active materials (Co, Ni, and Mn) moved in the direction of a magnetic force and an anode active material (C) moved in the opposite direction of the magnetic force.

17. The system of claim 16, further comprising: a low-temperature pyrolysis furnace rotation module (120) configured to rotate the low-temperature pyrolysis furnace (110) in a predetermined direction or in the opposite direction; a spiral (140) installed inside the low-temperature pyrolysis furnace (110), and configured to stir the waste lithium secondary battery scrap and the black powder and to promote the reduction reaction of the cathode material and the oxidation reaction of the anode material; a bucket (150) installed inside the low-temperature pyrolysis furnace (110) and configured to extract the black powder and the current collector mixture; a main hopper (180) configured to store the black powder and the current collector mixture extracted by the low-temperature pyrolysis furnace (110).

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0114] The above and other objectives, features, and other advantages of the present disclosure will be more clearly understood from the following detailed description when taken in conjunction with the accompanying drawings, in which:

[0115] FIG. 1 is a configuration view schematically illustrating a system for separating a cathode material of a waste lithium secondary battery using an oxidation reaction of an anode material and a reduction reaction of the cathode material according to the present disclosure;

[0116] FIG. 2 is a flowchart illustrating a method of separating a cathode material of a waste lithium secondary battery using an oxidation reaction of an anode material and a reduction reaction of the cathode material according to the present disclosure;

[0117] FIG. 3 is a block diagram illustrating the method of separating the cathode material of the waste lithium secondary battery using the oxidation reaction of the anode material and the reduction reaction of the cathode material according to the present disclosure;

[0118] FIG. 4 is a flowchart illustrating the method of separating the cathode material of the waste lithium secondary battery using the oxidation reaction of the anode material and the reduction reaction of the cathode material according to the present disclosure, in which black powder and a current collector mixture are separated, after which a cathode active material and an anode active material are separated through a magnetic separation process;

[0119] FIGS. 5 and 6 are configuration views specifically illustrating the system for separating the cathode material of the waste lithium secondary battery using the oxidation reaction of the anode material and the reduction reaction of the cathode material according to the present disclosure, in which FIG. 5 illustrates a configuration in which an electric heating device is in close contact with an outer circumferential surface of a low-temperature pyrolysis furnace, and FIG. 6 illustrates a configuration in which the electric heating device is installed with a predetermined gap from the outer circumferential surface of the low-temperature pyrolysis furnace; and

[0120] FIG. 7 is a side view of FIG. 5.

DETAILED DESCRIPTION OF THE INVENTION

[0121] Hereinafter, a method and a system for separating a cathode material of a waste lithium secondary battery using an oxidation reaction of an anode material and a reduction reaction of the cathode material according to the present disclosure will be described in detail with reference to the accompanying drawings.

[0122] Wherever possible, the same reference numerals will be used throughout the drawings and the description to refer to the same or like elements or parts. It will be understood that, when the functions of conventional elements and the detailed description of elements related with the present disclosure may make the gist of the present disclosure unclear, a detailed description of those elements will be omitted.

[0123] Unless the context clearly indicates otherwise, it will be further understood that the terms “comprises”, “comprising”, “includes”, and/or “including”, when used herein, specify the presence of stated features or components, but do not preclude the presence or addition of one or more other features or components.

[0124] FIG. 1 is a configuration view schematically illustrating the system for separating the cathode material of the waste lithium secondary battery using the oxidation reaction of the anode material and the reduction reaction of the cathode material according to the present disclosure. FIG. 2 is a flowchart illustrating a method of separating a cathode material of a waste lithium secondary battery using an oxidation reaction of an anode material and a reduction reaction of the cathode material according to the present disclosure. FIG. 3 is a block diagram illustrating the method of separating the cathode material of the waste lithium secondary battery using the oxidation reaction of the anode material and the reduction reaction of the cathode material according to the present disclosure.

[0125] The method of separating the cathode material of the waste lithium secondary battery according to the present disclosure is a method of recovering, using the oxidation reaction of the anode material and the reduction reaction of the cathode material, cathode active materials (Co, Ni, and Mn), which are valuable metals, from black powder in which raw materials (Co, Ni, Mn, Li, and C) for the cathode and anode materials are mixed.

[0126] As illustrated in FIG. 2, the method of separating the cathode material of the waste lithium secondary battery according to the present disclosure has a technical feature in that a waste lithium secondary battery scrap is introduced into a low-temperature pyrolysis furnace 110 of a low-temperature pyrolysis system 100 illustrated in FIG. 1, and then the black powder and a current collector mixture (metal mixture) (Cu and Al) are extracted by causing an explosive reaction of lithium contained in the waste lithium secondary battery scrap. Here, the cathode material is reduced through an oxidation-reduction reaction between the cathode material and the anode material in the black powder so that the cathode active materials (Co, Ni, and Mn) recover magnetism (or ferromagnetism). After that, through a magnetic separation process, the black powder is easily separated into the cathode active materials (Co, Ni, and Mn) moved in the direction of a magnetic force and the anode active material (C) moved in the opposite direction of the magnetic force.

[0127] As for the low-temperature pyrolysis furnace 110, for example, a set of two low-temperature pyrolysis furnaces 110 may be used. The low-temperature pyrolysis furnace 110 may perform a cycle of introduction, heating, and stirring on the first day, and perform a cycle of extraction, introduction, heating, and stirring on the second day.

[0128] As illustrated in FIGS. 2 and 3, the method of separating the cathode material of the waste lithium secondary battery according to the present disclosure includes: (a) introducing the lithium waste secondary battery scrap into the low-temperature pyrolysis furnace 110 of the low-temperature pyrolysis system 100 illustrated in FIG. 1, sealing the inside of the low-temperature pyrolysis furnace 110, and rotating and heating the low-temperature pyrolysis furnace 110 to a temperature at which an explosive reaction of lithium occurs (S10); (b) stopping the heating of the low-temperature pyrolysis furnace 110 when the low-temperature pyrolysis furnace 110 reaches a predetermined temperature, causing the explosive reaction of lithium contained in the waste lithium secondary battery scrap, inducing an increase in the internal temperature of the low-temperature pyrolysis furnace 110 by allowing the explosive reaction of lithium to continue while continuously rotating the low-temperature pyrolysis furnace 110, and gasifying an electrolyte, a separator, and a binder separated from the waste lithium secondary battery scrap and discharging the resulting syngas to the outside of the low-temperature pyrolysis furnace 110 (S20); (c) preparing the black powder so that the cathode actives materials (Co, Ni, and Mn) of the cathode material recover magnetism (or ferromagnetism) by reducing the cathode material through the oxidation-reduction reaction between the cathode material and the anode material in the black powder (S30); (d) extracting the black powder and the current collector mixture (Cu and Al) and transferring and discharging the black powder and the current collector mixture to the outside of the low-temperature pyrolysis furnace 110 (S40); and (e) performing the magnetic separation process to separate the black powder into the cathode active materials (Co, Ni, and Mn) moved in the direction of the magnetic force and the anode active material (C) moved in the opposite direction of the magnetic force (S50).

[0129] With reference to FIGS. 1 to 3, the method of separating the cathode material of the waste lithium secondary battery using the oxidation reaction of the anode material and the reduction reaction of the cathode material according to the present disclosure will be described in detail as follows.

[0130] First, in step (a), the waste lithium secondary battery scrap is introduced into the low-temperature pyrolysis furnace 110 of the low-temperature pyrolysis system 100. As the waste lithium secondary battery scrap, a defective product (process scrap) generated during the production of lithium secondary batteries or a used lithium secondary battery (waste scrap) that has been used for electric vehicles, etc. and has reached the end of its lifespan is used.

[0131] The process scrap contains about 6% of a binder and a separator. The waste lithium secondary battery scrap contains about 4.7% of a binder and a separator, about 6% of a pouch packaging material, and about 15% of an electrolyte. After sealing the inside of the low-temperature pyrolysis furnace 110, the low-temperature pyrolysis furnace 110 is rotated and heated to the temperature at which the explosive reaction of lithium occurs (S10).

[0132] In step (a), the low-temperature pyrolysis furnace 110 is heated to the temperature at which the explosive reaction of lithium occurs for 1 to 4 hours using an electric heating device 130.

[0133] Here, to maintain the temperature at which the explosive reaction of lithium occurs, the surface temperature of the low-temperature pyrolysis furnace 110 may be maintained at 120° C. to 200° C., and the internal temperature of the low-temperature pyrolysis furnace 110 may be maintained at 140° C. to 300° C.

[0134] In step (b), the heating of the low-temperature pyrolysis furnace 110 is stopped when the low-temperature pyrolysis furnace 110 reaches the predetermined temperature, and the explosive reaction explosive reaction of lithium contained in the waste lithium secondary battery scrap is caused. The explosive reaction of lithium is allowed to continue while continuously rotating the low-temperature pyrolysis furnace 110, thereby inducing the increase in the internal temperature of the low-temperature pyrolysis furnace 110. The electrolyte, the separator, and the binder separated from the waste lithium secondary battery scrap are gasified into syngas and the resulting syngas is discharged to the outside of the low-temperature pyrolysis furnace 110 (S20).

[0135] In step (b), the power of the electric heating device 130 is cut off. As the temperature is continuously increased due to the occurrence of the explosive reaction of lithium, the binder, the electrolyte, and the separator are gasified for 2 to 8 hours into syngas, and the resulting syngas is discharged.

[0136] The syngas thus generated inside the low-temperature pyrolysis furnace 110 by the heating through the electric heating device 130 is stored in a syngas storage tank 170 through a synthesis discharge connection pipe 171 by compression of a pump 172. The syngas may be used as renewable energy afterwards.

[0137] As described above, on the first day, the waste lithium secondary battery scrap (for example, 15 tons) is introduced into the low-temperature pyrolysis furnace 110 and heated through the electric heating device 130 for about 1 to 4 hours to create an atmosphere in which the explosive reaction. As the internal temperature of the low-temperature pyrolysis furnace 110 is increased to 140° C. to 300° C. by the explosive reaction of lithium, the binder, the electrolyte, and the separator are gasified into syngas by pyrolysis and the resulting syngas is discharged and removed. Here, it is preferable that the external temperature (surface temperature) of the low-temperature pyrolysis furnace 110 is 120° C. to 200° C. This is because when the external temperature of the low-temperature pyrolysis furnace 110 is less than 120° C., the explosive reaction of lithium does not occur efficiently, so that the electrolyte and the separator are not gasified and the binder is not separated. When the external temperature of the low-temperature pyrolysis furnace 110 exceeds 200° C., the excessive explosive reaction of lithium causes a rapid increase in the internal temperature of the low-temperature pyrolysis furnace 110, so that the cathode material and the current collector mixture become agglomerated and cannot be separated.

[0138] When the low-temperature pyrolysis furnace 110 is continuously rotated by driving a low-temperature pyrolysis furnace rotation module 120, the waste lithium secondary battery scrap is stirred by a spiral 140 installed inside the low-temperature pyrolysis furnace 110, and the explosive reaction of lithium is continuously induced. As the temperature is continuously increased, a condition is created in which the cathode material is reduced and the anode material is oxidized.

[0139] In step (c), the black powder is prepared so that the cathode actives materials (Co, Ni, and Mn) of the cathode material recover magnetism (or ferromagnetism) by reducing the cathode material through the oxidation-reduction reaction between the cathode material and the anode material in the black powder (S30).

[0140] In step (c), under constant temperature and pressure conditions, the following Chemical Formula 1 may be used.

Li(Ni.sub.xCo.sub.yMn.sub.z)O.sub.2+2C=Li+xNi+yCo+zMn+2CO  Chemical Formula 1:

[0141] In step (c), the temperature is continuously increased due to the explosive reaction of lithium, and the reduction reaction of the cathode material and the oxidation reaction of the anode material are simultaneously performed for 10 to 18 hours through a stirring action by the rotation of the spiral 140 (see FIG. 5) installed inside the low-temperature pyrolysis furnace 110.

[0142] Oxidation occurs when an element is combined with oxygen to form an oxide, and reduction occurs when oxygen is removed from an oxide to form an element. Each of the oxidation and reduction reactions is called a half-reaction, which is because the reactions always occur simultaneously. The oxidation and reduction reactions are collectively called an oxidation-reduction (redox) reaction.

[0143] Oxidation can be defined as the loss of one or more electrons in a substance (element, compound, ion, etc.) while reduction can be defined as the gain of one or more electrons in a substance. That is, the oxidation-reduction reaction consists of one oxidation half-reaction and one reduction half-reaction. When one atom loses one or more electrons, another atom has to gain those electrons.

[0144] Therefore, the oxidation-reduction reaction is a process in which electrons are transferred from one substance to another. In general, metal loses electrons and acts as a reducing agent, and non-metals with strong reactivity, such as oxygen and halogen elements, accept electrons and act as an oxidizing agent.

[0145] A substance that loses electrons to cause reduction is called a reducing agent, and a substance that gains electrons and causes oxidation is called an oxidizing agent. For example, an iron atom acts as the reducing agent in rusting of iron, and a carbon atom acts as the reducing agent while an iron atom acts as the oxidizing agent in the production of iron metal.

[0146] The cathode material of a lithium secondary battery is attached in an oxidized state of valuable metals, and carbon that can be used as an oxidizing agent is accumulated in the anode material. Thus, the cathode material may be reduced through an oxidation-reduction reaction between the cathode material and the anode material.

[0147] Lithium is used as a strong reducing agent in chemical reactions because it can be widely used in the form of lithium organic compounds such as n-butyllithium (CH.sub.3 (CH.sub.2).sub.3Li), lithium hydrogen (LiH), lithium aluminum hydride (LiAlH.sub.4), etc.

[0148] As described above, under constant temperature and pressure conditions, the following Chemical Formula 1 may be used.

Li(Ni.sub.xCo.sub.yMn.sub.z)O.sub.2+2C=Li+xNi+yCo+zMn+2CO  Chemical Formula 1:

[0149] In Chemical Formula 1, 2CO is in an unstable state, so it strongly binds to oxygen. Also, 2CO binds to oxygen particles contained in the cathode material because oxygen does not exist inside the sealed low-temperature pyrolysis furnace 110. As a result, 2CO acts as a catalyst to promote the reduction reaction of the cathode material, and is converted into carbon dioxide by gaining oxygen as illustrated in Chemical Formula 2 below to promote stabilization.

2CO+O.sub.2=2CO.sub.2↑  Chemical Formula 2:

[0150] Through the process of Chemical Formula 2, the cathode material is reduced to a state in which it can be recovered as a metal (reduced metal), and a portion of graphite, which is the anode material, is oxidized and converted into carbon dioxide.

[0151] In step (d), the black powder and the current collector mixture (Cu and Al) are extracted and discharged to the outside of the low-temperature pyrolysis furnace 110 (S40).

[0152] For example, on the second day, the low-temperature pyrolysis furnace 110 is rotated in the opposite direction, causing the spiral 140 installed inside the low-temperature pyrolysis furnace 110 to discharge the black powder and the current collector mixture.

[0153] Referring to FIGS. 5 and 6, a bucket 150 installed on an inner wall of the low-temperature pyrolysis furnace 110 scoops the black powder and the current collector mixture in the low-temperature pyrolysis furnace 110 and pours the same into an inlet 162a of a transfer screw conveyor 160. As a transfer screw 161 is rotated by a transfer screw driving motor 163, the black powder and the current collector mixture are discharged through an outlet 162b. An opening/closing valve 164 prevents the leakage of syngas, prevents external air from being arbitrarily introduced into the low-temperature pyrolysis furnace 110, and is configured to be selectively opened when discharging the extracted black powder and current collector mixture to the outside of the low-temperature pyrolysis furnace 110. The temperature for the extraction of the black powder and the current collector mixture is preferably 70° C. to 130° C. A specific configuration of the transfer screw conveyor 160 will be described later.

[0154] In step (e), the magnetic separation process is performed to separate the black powder into the cathode active materials (Co, Ni, and Mn) moved in the direction of the magnetic force and the anode active material (C) moved in the opposite direction of the magnetic force (S50).

[0155] In step (e), the black powder (Co, Ni, Mn, Li, and C) and the current collector mixture (Cu and Al) are separated by particle size. The current collector mixture is shredded and then separated into copper (Cu) and aluminum (Al) by a vibration specific gravity separation method, for example. The black powder is separated into a first part containing cobalt (Co), nickel (Ni), and manganese (Mn) that has recovered magnetism (or ferromagnetism) and a second part containing lithium (Li) and graphite (C) and separated from the first part by the magnetic force.

[0156] In addition, the black powder and the current collector mixture (Cu and Al) may be easily discharged to the outside of the low-temperature pyrolysis furnace 110 by performing stirring by rotating the low-temperature pyrolysis furnace 110 in a predetermined direction in steps (a), (b), and (c) and then by rotating the low-temperature pyrolysis furnace 110 in the opposite direction in step (d).

[0157] FIG. 4 is a flowchart illustrating the method of separating the cathode material of the waste lithium secondary battery using the oxidation reaction of the anode material and the reduction reaction of the cathode material according to the present disclosure, in which the black powder and the current collector mixture (Cu and Al) are separated, after which the cathode active materials (Co, Ni and Mn) and the anode active material (C) are separated through a magnetic separation process.

[0158] Referring to FIG. 1, the black powder and the current collector mixture (Cu and Al) are extracted, discharged the outside of the low-temperature pyrolysis furnace 110, and fed to a main hopper 180. Here, the black powder and the current collector mixture (Cu and Al) account for 94% of the total weight of the waste secondary battery.

[0159] As illustrated in FIG. 4, the black powder and the current collector mixture (Cu and Al) are introduced into a primary particle separation device (e.g., a three to four stage twist vibrating separator: Φ=1,200 and H=1,000), which is a component of a magnetic separator (190), and are separated by size (S300).

[0160] In step S300, large particles of the black powder are not separated by primary particle separation, but remain mixed with the current collector mixture in step S310. Therefore, the current collector mixture and unseparated black powder are finely grinded by a grinder which is a component of the magnetic separator 190 (S320).

[0161] Thereafter, the grinded current collector mixture and unseparated black powder are introduced into a secondary particle separation device (e.g., a three-stage vibrating particle separator), which is a component of the magnetic separator 190, and are separated by size (S330), so that the current collector mixture not mixed with the black powder is obtained (S340). Small particles of the black powder are separated by the primary particle separation to separate the black powder again (S310). Thereafter, the current collector mixture, which accounts for 15% of the total weight of the waste secondary battery, is introduced into a vibration specific gravity separator, which is a component of the magnetic separator 190, and is separated by specific gravity under vibration into copper (Cu) and aluminum (Al) (S350).

[0162] Thereafter, the black powder in which the raw materials (Co, Ni, Mn, Li, and C) for the cathode material and the anode material are mixed is subjected to the magnetic separation process, so that cobalt (Co), nickel (Ni), and manganese (Mn) that have recovered magnetism (or ferromagnetism) by the reduction reaction are separated from lithium (Li) and graphite (carbon) (C) (S360).

[0163] In step S360, since the raw materials for the cathode material recover magnetism (or ferromagnetism) through the reduction reaction in the previous process, the cathode active materials (Co, Ni, and Mn) attracted by the magnetic force are separated from the anode active material (C) moved in the opposite direction of the magnetic force during the magnetic separation process. As a result, the cathode active materials (Co, Ni, and Mn), which are valuable metals, can be easily extracted, thereby securing the economic feasibility of recycling waste lithium secondary batteries.

[0164] Furthermore, although not illustrated in the drawings, lithium (Li) may be extracted by performing dust collection during the particle separation process and the magnetic separation process.

[0165] FIGS. 5 and 6 are configuration views specifically illustrating the system for separating the cathode material of the waste lithium secondary battery using the oxidation reaction of the anode material and the reduction reaction of the cathode material according to the present disclosure, in which FIG. 5 illustrates a configuration in which an electric heating device is in close contact with an outer circumferential surface of a low-temperature pyrolysis furnace, and FIG. 6 illustrates a configuration in which the electric heating device is installed with a predetermined gap from the outer circumferential surface of the low-temperature pyrolysis furnace. FIG. 7 is a side view of FIG. 5.

[0166] Referring to FIGS. 5 to 7, the system for separating the cathode material of the waste lithium secondary battery using the oxidation reaction of the anode material and the reduction reaction of the cathode material according to the present disclosure is an apparatus for separating a cathode material of a waste lithium secondary battery to recover cathode active materials (Co, Ni, and Mn) from black powder in which cathode and anode materials (Co, Ni, Mn, Li, and C) are mixed. The system may include a low-temperature pyrolysis furnace 110, a low-temperature pyrolysis furnace rotation module 120, an electric heating device 130, a spiral 140, a bucket 150, a screw conveyor 160, a syngas storage tank 170, a main hopper 180, and a magnetic separator 190.

[0167] Hereinafter, the configuration of the system for separating the cathode material of the waste lithium secondary battery according to the present disclosure will be described in detail as follows.

[0168] First, the low-temperature pyrolysis furnace 110 is rotatably supported on a base frame 1. The low-temperature pyrolysis furnace 110 heats and gasifies a binder, an electrolyte, and a separator, which are organic compounds contained in a waste lithium secondary battery scrap, inside the low-temperature pyrolysis furnace 110 into syngas, removes the resulting syngas, and extracts the black powder and a current collector mixture (metal mixture) (Cu and Al).

[0169] The low-temperature pyrolysis furnace 110 has an annular flange F extended at each of front and rear ends thereof, an inlet 112 formed at the front end thereof and into which the waste lithium secondary battery scrap is introduced, and a closed space 113 formed therein.

[0170] The low-temperature pyrolysis furnace 110 may be configured as, for example, a rotary kiln.

[0171] In detail, the low-temperature pyrolysis furnace 110 may have a cylindrical shape to accommodate a predetermined amount (e.g., 15 tons) of waste lithium secondary battery scrap, and is configured to be rotatable by the low-temperature pyrolysis furnace rotation module 120.

[0172] The respective annular flanges F are formed at the front and rear ends of the low-temperature pyrolysis furnace 110. The inlet 112 at the front end of the low-temperature pyrolysis furnace 110 is configured to be opened and closed so that the low-temperature pyrolysis furnace 110 is blocked after the introduction of the waste lithium secondary battery scrap. The reason for providing the annular flanges F is to prevent heat loss by preventing a support roller 121 from direct contact with the low-temperature pyrolysis furnace 110 under high temperature.

[0173] The low-temperature pyrolysis furnace 110 is preferably designed with a large capacity (e.g., about 40 m.sup.3, diameter 3.200 mm, and length 5,000 mm) to accommodate a large amount of waste lithium secondary battery scrap in one operation.

[0174] The airtightness inside the low-temperature pyrolysis furnace 110 has to be continuously maintained to achieve efficient pyrolysis by an explosive reaction of lithium and to facilitate the reduction reaction of the cathode material and the oxidation reaction of anode material. To prevent heat loss during low-temperature pyrolysis of the waste lithium secondary battery scrap, an insulating material 114 is preferably installed on the outer periphery of the electric heating device 130.

[0175] In addition, the low-temperature pyrolysis furnace rotation module 120 is a device for rotating the low-temperature pyrolysis furnace 110 in a predetermined direction or in the opposite direction.

[0176] As illustrated in FIGS. 1, 5 and 7, the low-temperature pyrolysis furnace rotation module 120 may include the support roller 121 rotatably supporting a lower outer peripheral surface of each of the flanges F of the low-temperature pyrolysis furnace 110; a ring gear 122 installed on the outer periphery of the flange F at the rear end of the low-temperature pyrolysis furnace 110; a pinion gear 123 fixedly installed on the base frame 1 to be meshed with the ring gear 122; and a reduction geared motor 124 fixedly installed on the base frame 1 to rotate the pinion gear 123.

[0177] In a state in which the respective support rollers 121 rotatably support the lower outer peripheral surfaces of the flanges F of the low-temperature pyrolysis furnace 110, as the reduction geared motor 124 rotates the pinion gear 123, the ring gear 122 meshed with the pinion gear 123 is rotated to cause rotation of the low-temperature pyrolysis furnace 110. The installation position and number of the support rollers 121 may vary depending on design conditions. The support rollers 121 are preferably made of a material with low heat conduction to minimize heat conduction.

[0178] To minimize heat conduction from the low-temperature pyrolysis furnace 110, the ring gear 122 and the support rollers 121 are configured to be in contact the outer peripheral surfaces of the annular flanges F extended at the front and rear ends of the low-temperature pyrolysis furnace 110.

[0179] Furthermore, to minimize heat loss of the low-temperature pyrolysis furnace 110, it is preferable that the outer peripheral surface of the low-temperature pyrolysis furnace 110 is spaced apart a predetermined distance from the base frame 1, and the ring gear 122 is made of a material with low heat conduction.

[0180] The electric heating device 130 may be installed on the outside of the low-temperature pyrolysis furnace 110 to heat the low-temperature pyrolysis furnace 110.

[0181] Since the electric heating device 130 uses an electric heating method, the heating time is greatly reduced to 2 hours, and it is not necessary to separately discharge exhaust gas inside the low-temperature pyrolysis furnace 110. In addition, the internal temperature of the low-temperature pyrolysis furnace 110 is maintained constantly at a high temperature of 140° C. to 300° C.

[0182] The electric heating device 130 is installed to surround the entire outer peripheral surface of the low-temperature pyrolysis furnace 110, and is fixed to the base frame 1.

[0183] The electric heating device 130 may be configured to be in close contact with the outer peripheral surface of the low-temperature pyrolysis furnace 110 (refer to FIG. 5) or may be configured to be spaced apart a predetermined gap G from the outer peripheral surface of the low-temperature pyrolysis furnace 110 (refer to FIG. 6).

[0184] The spiral 140 is fixedly installed on an inner wall of the low-temperature pyrolysis furnace 110 in a spiral structure to stir the waste lithium secondary battery scrap and the black powder and to promote the reduction reaction of the cathode material and the oxidation reaction of the anode material.

[0185] The screw conveyor 160 is installed horizontally at the rear end of the low-temperature pyrolysis furnace 110, with an end being inserted into the low-temperature pyrolysis furnace 110. The screw conveyor 160 transfers the black powder and the current collector mixture.

[0186] The screw conveyor 160 is installed horizontally and provides a passage for allowing the black powder (Co, Ni, Mn, Li, and C) and the current collector mixture (metal mixture) (Cu and Al), and syngas to be discharged therethrough. The black powder (Co, Ni, Mn, Li, and C) and the current collector mixture (metal mixture) (Cu and Al) are generated in the low-temperature pyrolysis furnace 110 as a result of pyrolysis and an oxidation-reduction reaction of metal, and the syngas is generated in the low-temperature pyrolysis furnace 110.

[0187] The screw conveyor 160 may include: a transfer screw 161 for transferring the black powder and the current collector mixture; a transfer pipe 162 having a transfer screw 161 therein and an outlet 162b at a lower portion thereof; a transfer screw driving motor 163 for rotating the transfer screw 161; and an opening/closing valve 164 installed at the outlet 162b.

[0188] A bearing B is installed between the transfer pipe 162 and the flanges F of the low-temperature pyrolysis furnace 110 to enable rotation of the low-temperature pyrolysis furnace 110. A gasket (not illustrated), etc. is installed to prevent a gap (to prevent gas leakage) between the transfer pipe 162 and the low-temperature pyrolysis furnace 110.

[0189] The transfer screw 161 is installed in the transfer pipe 162. The transfer screw 161 is configured to be rotatable by the transfer screw driving motor 163. The power of the transfer screw driving motor 163 is transmitted to the transfer screw 161 through a belt 165.

[0190] An inlet 162a is formed at an upper side of a front end of the transfer pipe 162, and the bucket 150 is installed on the inner wall of the low-temperature pyrolysis furnace 110. Therefore, when the low-temperature pyrolysis furnace 110 is rotated, the spiral 140 moves the black powder and the current collector mixture toward the screw conveyor 160, and the bucket 150 repeats the process of introducing the black powder and the current collector mixture into the inlet 162a while being moved from bottom to top inside the low-temperature pyrolysis furnace 110.

[0191] The syngas storage tank 170 is connected to the screw conveyor 160 and a syngas discharge connection pipe 171 to store the syngas discharged from the low-temperature pyrolysis furnace 110. The syngas compressed and stored in the syngas storage tank 170 may be used as renewable energy afterwards.

[0192] The syngas generated as a result of heating and the explosive reaction of lithium in the low-temperature pyrolysis furnace 110 is introduced into the syngas storage tank 170 through the syngas discharge connection pipe 171 in a state in which the pressure of the low-temperature pyrolysis furnace 110 is higher than atmospheric pressure (e.g., about 0.02 MPa), and then is compressed and stored in the syngas storage tank 170 by a vacuum pump 172.

[0193] The black powder and the current collector mixture extracted by the low-temperature pyrolysis furnace 110 are supplied to the main hopper 180.

[0194] The main hopper 180 may be made of metal because the black powder (Co, Ni, Mn, Li, and C) and the current collector mixture (Cu and Al) are in a very hot state (e.g., 80 to 150° C.) at the time of extraction.

[0195] The black powder (Co, Ni, Mn, Li, and C) and the current collector mixture (Cu and Al) may be transferred to the magnetic separator 190 using a transfer means (not illustrated) such as the screw conveyor 160, an elevator conveyor, or a blower.

[0196] The magnetic separator 190 separates the black powder into the cathode active materials (Co, Ni, and Mn) moved in the direction of a magnetic force from and the anode active material (C) moved in the opposite direction of the magnetic force.

[0197] As described above, the present disclosure has the following advantages.

[0198] First, when lithium is heated to a level where lithium can undergo an explosive reaction using the low-temperature pyrolysis system, the binder, the electrolyte, and the separator contained in the waste lithium secondary battery are gasified into syngas by the explosive reaction of lithium and the resulting syngas is removed. The reduction reaction of the cathode material and the oxidation reaction of the anode material are promoted by the continuous explosive reaction of lithium and the stirring action of the spiral. As a result, the black powder and the current collector mixture are extracted. Therefore, it is possible to improve the recovery rate of valuable metals to more than 97%, thereby improving recycling efficiency. In addition, the valuable metals of the cathode material contained in the black powder recover magnetism (or ferromagnetism), which is a characteristic of the raw materials, through the reduction reaction, so it is possible to easily separate the expensive cathode material through magnetic separation, thereby greatly improving the economic efficiency of recycling waste lithium secondary batteries.

[0199] Second, while a conventional process takes about 2 to 3 days, the process according to the present disclosure is completed in one day through introduction (2 hr), heating and reduction (2 hr), stirring (12 hr), and discharge (2 hr), thereby greatly reducing the overall process time.

[0200] Third, the conventional process requires cooling of black powder in a heating furnace, so there is a limit to reducing the process time. However, in the present disclosure, the black powder is discharged directly into the main hopper, so the cooling time is not necessary, thereby greatly reducing the process time. In addition, the black powder is extracted at a high temperature and stored in the main hopper, so it is possible to more easily separate the cathode material from the anode material.

[0201] Fourth, the conventional process uses a gas heating method, so the heating time is 4 to 5 hours and exhaust gas inside the heating furnace has to be separately discharged. However, the present disclosure uses an electric heating method, so it is possible to reduce the heating time to 2 hours, and it is not necessary to separately discharge exhaust gas inside the low-temperature pyrolysis furnace. Also, it is possible to constantly maintain the internal temperature of the low-temperature pyrolysis furnace 110 at a high temperature of 140° C. to 300° C.

[0202] Although preferred embodiments of the present disclosure has been described for illustrative purposes, those skilled in the art will appreciate that various modifications, additions, and substitutions are possible, without departing from the scope and spirit of the disclosure as defined in the accompanying claims.