Recycling method for waste lithium ion secondary battery and electrode material for lithium ion secondary battery obtained therefrom

Abstract

To provide: a method for economically and eco-friendly recovering positive electrode and negative electrode materials from waste lithium ion secondary batteries, which are produced the pyrolysis of a waste lithium ion secondary batteries; and positive electrode and negative electrode raw materials obtained therefrom.SOLUTION: In order to achieve the object, a recycling method for waste lithium ion secondary batteries according to the present invention includes the steps of: (a) loading the waste lithium ion secondary batteries into a pyrolysis furnace; (b) increasing an internal temperature of the pyrolysis furnace to induce self-heating of the waste lithium ion secondary batteries; (c) maintaining the self-heating reaction of the waste lithium ion secondary batteries; (d) discharging a first powder produced after completing the self-heating reaction of the waste lithium ion secondary batteries; and (e) injecting the first powder into water, dissolving the lithium component contained in the first powder, and separating and recovering a lithium aqueous solution, a precipitate settled in the lithium aqueous solution and a floating material floating on a surface of the lithium aqueous solution.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a method for recycling used lithium ion batteries and an electrode material for lithium ion secondary batteries obtained therefrom, and more particularly, to a recycling method that can recover electrode materials in an environmentally friendly and economical manner through low-temperature pyrolysis and water separation of used lithium ion secondary batteries, and an electrode material obtained therefrom. [Background technology]

[0002] As the automobile industry shifts from internal combustion engine vehicles to electric vehicles, Europe and China, which are the growth centers of global electric vehicles and secondary batteries, are promoting the widespread use and competitiveness of electric vehicles through carbon dioxide regulation proposals and environmentally friendly vehicle roadmaps. This is expected to lead to rapid growth in the global electric vehicle market.

[0003] Electric vehicle batteries are usually discarded after 5 to 10 years of use, so the waste battery market is expected to take off. The amount of waste electric vehicle batteries generated globally is expected to reach approximately 1.6 million tons by 2030, and many countries, mainly in Europe, are making large-scale investments in the development of a system to recover valuable metals from waste batteries.

[0004] Unlike reuse, the waste battery recycling industry recovers valuable metals from waste batteries and recycles them as raw materials, which simultaneously solves environmental problems and ensures a stable supply of valuable resources.

[0005] Recycling waste batteries generally involves discharging, dismantling and crushing the batteries, followed by a hydrometallurgical or pyrometallurgical process to extract valuable metals. However, the pyrometallurgical process, which is suitable for large-volume processing and has a high recovery rate, is attracting attention.

[0006] In dry smelting, the powder obtained by crushing is heated at high temperatures to burn off the organic compounds and polymer components contained in the crushed powder, and then it is crushed again and valuable metals are extracted using a wet method with strong acid.

[0007] Such a dry smelting process requires a lot of time and equipment for discharge and pulverization, and subsequent complicated processes are required, making it less economical. The resultant product discharged after heating at high temperatures contains a large amount of impurities, the extraction ratio of valuable components obtained from the entire powder is low, and since it exists in a lump-like state, further pulverization and the use of strong acids are unavoidable in order to extract valuable components from it, which creates environmental problems. Summary of the Invention [Problem to be solved by the invention]

[0008] The present invention aims to provide a method for recovering electrode materials for positive and negative electrodes from used lithium ion secondary batteries, which are produced by pyrolyzing used lithium ion secondary batteries, in an economical and environmentally friendly manner, and to provide electrode raw materials for positive and negative electrodes obtained therefrom. [Means for solving the problem]

[0009] In order to achieve the above-mentioned object, the method for recycling used lithium ion secondary batteries according to the present invention may include the steps of: (a) loading used lithium ion secondary batteries into a pyrolysis furnace; (b) increasing an internal temperature of the pyrolysis furnace to induce self-heating of the used lithium ion secondary batteries; (c) sustaining the self-heating reaction of the used lithium ion secondary batteries; (d) discharging a first powder produced after the self-heating reaction of the used lithium ion secondary batteries is completed; and (e) putting the first powder into water to dissolve the lithium component contained in the first powder, and separating and recovering a lithium aqueous solution, a precipitate that sinks in the lithium aqueous solution, and a floating matter that rises to the surface of the lithium aqueous solution.

[0010] In addition, in the method for recycling used lithium ion secondary batteries according to an embodiment of the present invention, the temperature of the water into which the first powder is introduced in step (e) may be 30° C. or less.

[0011] In addition, in the method for recycling used lithium ion secondary batteries according to an embodiment of the present invention, in step (e), fine bubbles of 20 microns or less may be injected into a slurry prepared after the first powder is added to the water.

[0012] In addition, the method for recycling used lithium ion secondary batteries according to an embodiment of the present invention may further include recovering lithium carbonate by evaporating water from the lithium aqueous solution.

[0013] In addition, the method for recycling used lithium ion secondary batteries according to an embodiment of the present invention may further include the step of adding an alkali to the lithium aqueous solution to increase the pH, thereby precipitating and recovering the lithium component as lithium hydroxide.

[0014] In addition, the method for recycling used lithium ion secondary batteries according to an embodiment of the present invention may further include the step of introducing the precipitate into an acidic aqueous solution and recovering a metal aqueous solution in which metal components contained in the precipitate are dissolved.

[0015] In the method for recycling used lithium ion secondary batteries according to an embodiment of the present invention, the precipitate may include metallic nickel and cobalt.

[0016] In the method for recycling used lithium ion secondary batteries according to an embodiment of the present invention, the precipitate may include metallic iron.

[0017] In addition, in the method for recycling used lithium ion secondary batteries according to an embodiment of the present invention, in step (a), the used lithium ion secondary batteries may be charged together with water into a pyrolysis furnace.

[0018] In addition, in the method for recycling used lithium ion secondary batteries according to an embodiment of the present invention, the amount of water input in step (a) may be in the range of 1 to 10 parts by mass per 100 parts by mass of the positive electrode material contained in the used lithium ion batteries input into the pyrolysis furnace.

[0019] In the method for recycling used lithium ion secondary batteries according to an embodiment of the present invention, in the step (a), the used lithium ion secondary batteries may not be in a discharged state.

[0020] In addition, in the method for recycling used lithium ion secondary batteries according to an embodiment of the present invention, in the step (a), the used lithium ion secondary batteries may not have been subjected to a pulverization process.

[0021] In addition, in the method for recycling used lithium ion secondary batteries according to an embodiment of the present invention, the used lithium ion secondary batteries in the step (a) may include used lithium ion secondary batteries that are discarded as defective during a manufacturing process of lithium ion secondary batteries.

[0022] In the method for recycling used lithium ion secondary batteries according to an embodiment of the present invention, in the step (a), the used lithium ion secondary batteries may include used lithium ion secondary batteries in a powder state that have been disassembled and pulverized.

[0023] In the method for recycling used lithium ion secondary batteries according to an embodiment of the present invention, the internal temperature in the step (b) may be 400° C. or less.

[0024] In addition, in the method for recycling used lithium ion secondary batteries according to an embodiment of the present invention, the pyrolysis furnace does not need to be heated in the step (c).

[0025] In addition, in the method for recycling used lithium ion secondary batteries according to an embodiment of the present invention, the step (c) may last for 10 to 24 hours.

[0026] In addition, in the method for recycling used lithium ion secondary batteries according to an embodiment of the present invention, the step (c) may be performed in an inert gas atmosphere.

[0027] According to the present invention, there can be provided a metal powder recovered from used lithium ion secondary batteries having magnetism, which contains metallic Ni and Co as the precipitate recovered through the above-mentioned recycling method for used lithium ion secondary batteries.

[0028] The metal powder according to one embodiment of the present invention may have a saturation magnetization value of 15 emu / g or more.

[0029] The metal powder according to an embodiment of the present invention may have an average particle size of 20 μm or less and a standard deviation in particle size distribution of 10 μm or less, as measured by a particle size analyzer using laser diffraction.

[0030] In the metal powder according to one embodiment of the present invention, the molar ratio of the metal Ni to the metal Co (M Ni / M Co , M Ni and M. Co are respectively the molar fraction of the metal Ni and the molar fraction of the metal Co in the metal reduced powder as a first molar ratio (M1), and the molar ratio of Ni to Co in the positive electrode material of the waste lithium ion secondary battery before thermal decomposition (m Ni / m Co , m ni and m Co and the molar fraction of Co in the positive electrode material) is a second molar ratio (M2), the difference between the first molar ratio and the second molar ratio may be 10% or less of the value of the second molar ratio.

[0031] The metal powder according to one embodiment of the present invention may contain no metal ions other than Li, Ni, Co, Fe, and Al, and may contain F. - and Cl - The anion may not be included.

[0032] According to the present invention, it is possible to provide iron powder recovered from waste lithium ion secondary batteries containing metallic iron or iron oxide as the precipitate recovered through the above-mentioned method for recycling waste lithium ion secondary batteries.

[0033] According to the present invention, the suspended matter recovered through the above-mentioned recycling method for used lithium ion secondary batteries may be carbon powder recovered from used lithium ion secondary batteries containing graphite or graphite and silica.

[0034] The carbon powder according to an embodiment of the present invention may have an average particle size of 20 μm or less and a standard deviation in particle size distribution of 10 μm or less, as measured by a particle size analyzer using laser diffraction.

[0035] According to the present invention, it is possible to provide a recycled powder of used lithium ion secondary batteries containing lithium carbonate, metallic nickel and metallic cobalt as the first powder recovered through the above-mentioned recycling method of used lithium ion secondary batteries. Effect of the Invention

[0036] The recycling method for used lithium ion secondary batteries according to the present invention is economical and environmentally friendly, so that it can increase the recycling rate of used lithium ion secondary batteries and solve environmental problems that may occur during recycling.

[0037] Furthermore, the valuable element components obtained according to the present invention can be used to produce economical cathode or anode materials through electrode raw materials for cathode or anode. [Brief description of the drawings]

[0038] [Figure 1] 2 is a flowchart illustrating a method for recycling used lithium ion secondary batteries according to an embodiment of the present invention. [Diagram 2] FIG. 2 is a schematic diagram illustrating a process of obtaining lithium carbonate in a method for recycling used lithium ion secondary batteries according to an embodiment of the present invention. [Diagram 3] 1 is a graph showing an X-ray diffraction analysis result of lithium carbonate obtained through a method for recycling used lithium ion secondary batteries according to an embodiment of the present invention. [Figure 4]1 is a graph showing a particle size analysis result using laser diffraction for a precipitate obtained through a method for recycling used lithium ion secondary batteries according to an embodiment of the present invention. [Diagram 5] 4 is a graph showing a result of measuring saturation magnetization of a powder immediately after pyrolysis and a precipitate recovered after treatment with water, which are obtained through a method for recycling used lithium ion secondary batteries according to an embodiment of the present invention; [Figure 6] 4A and 4B are transmission electron microscope images and diffraction pattern analysis results of a precipitate obtained through a method for recycling used lithium ion secondary batteries according to an embodiment of the present invention. [Figure 7] 4A and 4B are transmission electron microscope images and diffraction pattern analysis results of a precipitate obtained through a method for recycling used lithium ion secondary batteries according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0039] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will now be described in detail with reference to the accompanying drawings, in order to enable those skilled in the art to easily carry out the present invention. However, the present invention may be embodied in many different forms and is not limited to the embodiments set forth herein.

[0040] Throughout this specification, when a part "comprises" a certain element, this does not mean that it excludes other elements, but that it may further include other elements, unless specifically stated to the contrary.

[0041] The terms of degree used in this specification, such as "about," "substantially," and the like, are used in a numerical value or a close numerical value when the manufacturing and material tolerances inherent in the referred meaning are given, and are used to prevent unscrupulous infringers from unfairly using the disclosure content in which precise and absolute numerical values ​​are mentioned to aid in the understanding of this application. In addition, throughout this specification, "the step of" or "the step of" does not mean "the step for".

[0042] Throughout this specification, the term "combination thereof" in a Markush-style expression means a mixture or combination of one or more selected from the group of elements set forth in a Maxi-style expression, and means including at least one selected from the group of elements.

[0043] Throughout this specification, the term "A and / or B" means "A or B" or "A and B."

[0044] The recycling method for used lithium ion secondary batteries that can be provided by the present invention includes the steps of (a) loading used lithium ion secondary batteries into a pyrolysis furnace, (b) increasing the internal temperature of the pyrolysis furnace to induce self-heating of the used lithium ion secondary batteries, (c) sustaining the self-heating reaction of the used lithium ion secondary batteries, (d) discharging a first powder produced after the self-heating reaction of the used lithium ion secondary batteries is completed, and (e) putting the first powder into water to dissolve the lithium component contained in the first powder, and separating and recovering a lithium aqueous solution, a precipitate that sinks in the lithium aqueous solution, and a floating matter that rises to the surface of the lithium aqueous solution.

[0045] In the recycling method of used lithium ion secondary batteries according to the present invention, the batteries are heated at a relatively low temperature to induce pyrolysis through self-heating of the positive electrode material, binder, electrolyte, etc. contained in the batteries. In particular, when the used lithium ion secondary batteries are charged into the pyrolysis furnace to increase the internal temperature, the batteries can be rotated through stirring to induce a uniform reaction.

[0046] Meanwhile, black mass, which is a powder produced by disassembling and crushing used lithium-ion secondary batteries, can also generate heat due to the positive electrode material, binder, electrolyte, etc. inside, so it is possible to induce a reaction through low-temperature heating. In this case, it is preferable that the black mass is not subjected to heat treatment during the treatment process of used lithium-ion batteries.

[0047] In order to facilitate the self-heating reaction, the waste lithium ion secondary batteries can be charged into a pyrolysis furnace without being discharged and the temperature can be increased. Such waste lithium ion secondary batteries that have not been discharged have a high energy state, so that self-heating can easily occur even when heated at a low temperature, making pyrolysis possible. In particular, since no discharge treatment is required, unlike conventional pyrolysis methods, no device or process for discharging is required, and the process cost can be significantly reduced.

[0048] In addition, the used lithium ion secondary batteries input in the recycling method of the used lithium ion secondary batteries according to the present invention may be in an unpulverized state. In the conventional recycling method, the used lithium ion secondary batteries are crushed and then heated at high temperature, but in the recycling method of the present invention, the batteries are charged into a pyrolysis furnace in an unpulverized state. After the self-heating reaction is completed, the positive electrode material, negative electrode material, electrolyte, etc. in the used lithium ion secondary batteries are decomposed into a powder state, but the battery case and current collector can maintain their shape. As a result, the positive electrode material, negative electrode material, etc. that have been powdered after the low-temperature self-heating can be easily separated from the case and current collector that maintain their shape. As such, a crushing device and process are not required, and the process cost can be reduced.

[0049] Meanwhile, the waste lithium ion secondary batteries input in the method for recycling waste lithium ion secondary batteries according to the present invention may be black mass, which is a powder produced by disassembling and crushing waste lithium ion secondary batteries. Since the black mass can also generate heat due to the positive electrode material, binder, electrolyte, etc. inside, it is possible to induce a reaction through low-temperature heating. In this case, it is preferable that the black mass is not subjected to heat treatment during the treatment process of waste lithium ion batteries.

[0050] In addition, the used lithium ion secondary batteries input in the recycling method for used lithium ion secondary batteries according to the present invention include used lithium ion secondary batteries that are discarded due to defects during the manufacturing process of secondary batteries. The manufacturing process of secondary batteries is divided into a plate process, an assembly process, a chemical formation process, etc., and the used lithium ion secondary batteries as intermediate waste including the plate coated with the positive electrode material in each of these processes may all be recycled through the recycling method for used lithium ion secondary batteries according to the present invention.

[0051] In the conventional high-temperature pyrolysis process, not only the positive electrode material and the negative electrode material contained in the waste lithium ion battery are agglomerated, but also the case, the current collector, etc. Therefore, in order to separate valuable components from the agglomerated materials, a crushing process is required for the agglomerated materials not only before but also after the heat treatment process, and many impurities are contained in the crushed materials. In contrast, the recycling method according to the present invention can easily separate valuable element components contained in the positive electrode material or the negative electrode material by powdering them through a self-heating process.

[0052] In addition, in the recycling method according to the present invention, since pyrolysis is performed through self-heating of materials in the waste lithium ion secondary batteries, there is no need to raise the temperature to a high temperature compared to conventional recycling methods, thereby reducing energy costs.

[0053] The first powder collected after the self-heating is completed contains metal elements such as nickel, cobalt, manganese, aluminum, and iron in the form of metal or oxide, which may be contained in the positive electrode material of the waste lithium-ion secondary battery. In particular, nickel, cobalt, iron, etc. may be reduced to metallic nickel, cobalt, iron, etc. through a carbon-thermal reduction reaction through carbon components such as the separator and negative electrode material contained in the waste lithium-ion secondary battery, and may be contained in the first powder. Meanwhile, lithium in the positive electrode material and electrolyte is converted to lithium carbonate (Li2CO3) during the self-heating reaction, and a portion of the negative electrode material is decomposed and volatilized and removed, while the remainder remains in the first powder as graphite or silica.

[0054] When the first powder, which contains various valuable components, is put into pure water, the lithium carbonate contained therein dissolves in the water to form a lithium aqueous solution. Nickel, cobalt, manganese, aluminum, iron, and other elements contained in the first powder in the form of metal or oxide precipitate and sink to the bottom. Graphite and silica, which are components of the negative electrode material, have low density and therefore float on the surface of the water.

[0055] Therefore, in the step (e), the valuable element components may be recovered from the waste lithium ion secondary batteries as an aqueous lithium solution, a precipitate, or a suspended solid. Lithium may be recovered from the aqueous lithium solution, and the raw materials for the positive electrode material, such as nickel, cobalt, manganese, aluminum, or iron, may be recovered from the precipitate. In addition, graphite and / or silica, which are the materials for the negative electrode material, may be recovered from the suspended solid that rises to the surface of the water.

[0056] The above-mentioned method for recycling used lithium ion secondary batteries according to the present invention is shown in the flow chart of FIG.

[0057] Meanwhile, the lower the temperature of the water into which the first powder is added in step (e), the more advantageous it is for the lithium aqueous solution, because the solubility of lithium carbonate is higher in water with a lower temperature. Therefore, in the method for recycling used lithium ion secondary batteries according to the present invention, the temperature of the water into which the first powder is added is preferably 30° C. or less, more preferably 25° C. or less, and even more preferably 10° C. or less. The lower the temperature, the more advantageous it is, but considering the process cost, it is advantageous to adjust the temperature to an appropriate temperature or less.

[0058] In addition, for effective and rapid dissolution of lithium and effective separation into suspended matter and precipitate, fine bubbles of 20 microns or less may be supplied to the slurry prepared by adding the first powder to water. The fine bubbles thus supplied cause a slurry flow within the slurry, induce rapid dissolution of lithium carbonate, and effectively assist separation of precipitate and suspended matter. The size of the fine bubbles is preferably 20 microns or less, because if the size is larger than this, the fine bubbles quickly rise to the surface of the slurry, making it difficult to obtain the effect of the fine bubbles.

[0059] Meanwhile, the slurry prepared after adding the first powder to water may be effectively separated into a lithium aqueous solution in which lithium carbonate is dissolved, suspended matter, and precipitates through stirring or ultrasonic treatment.

[0060] In order to recover lithium from the lithium aqueous solution, all the water contained in the lithium aqueous solution is evaporated and the lithium carbonate (Li2CO3) is recovered. After the lithium carbonate contained in the first powder is dissolved in water and separated into a lithium aqueous solution, the water is removed again and the lithium carbonate can be recovered as pure lithium carbonate.

[0061] FIG. 2 is a schematic diagram illustrating a method for obtaining pure lithium carbonate by dissolving a first powder obtained by completing the thermal decomposition in low-temperature water according to the method for recycling used lithium ion secondary batteries according to the present invention, separating the lithium aqueous solution, and evaporating water from the lithium aqueous solution.

[0062] Lithium may also be recovered from an aqueous lithium solution by adding an alkali such as sodium hydroxide or calcium hydroxide to the solution to increase the pH, and precipitating the lithium ions contained in the solution in the form of lithium hydroxide (LiOH).

[0063] Meanwhile, in the recycling method of used lithium ion secondary batteries according to the present invention, water may be input into the pyrolysis furnace together with the used lithium ion secondary batteries in the step (a). The input water may react with the carbon components in the used lithium ion secondary batteries to generate methane (CH4) gas, which may facilitate the reduction of nickel or cobalt components contained in the positive electrode material in the used lithium ion batteries.

[0064] Although a sufficient effect can be obtained even with a small amount of water, it may be in the range of 1 to 10 parts by mass per 100 parts by mass of the positive electrode material contained in the waste lithium-ion secondary battery. If the amount is too small, it is difficult to obtain the methane gas effect, and if the amount is too large, the energy cost for thermal decomposition increases, which is not preferable.

[0065] In addition, in the method for recycling used lithium ion secondary batteries according to the present invention, the heating for pyrolysis can be performed at 400° C. or less, so that the energy cost for pyrolysis can be reduced. The heating for pyrolysis can be performed at 300° C. or less, or 200° C. or less.

[0066] After the self-heating starts after heating, the artificial heating for pyrolysis can be stopped to continue the self-heating reaction of the waste lithium ion secondary battery. This reaction may be continued for 10 to 24 hours. If the reaction time is too short, there is a high possibility of impurities being generated due to a rapid reaction, and if it is too long, the process productivity decreases, which is undesirable. The reaction time may be adjusted by adjusting the internal temperature and atmosphere in the pyrolysis furnace in steps (b) and (c).

[0067] The pyrolysis reaction after self-heating may be carried out in an inert gas atmosphere, and the inert gas may be nitrogen, helium or argon.

[0068] Meanwhile, the precipitate recovered in step (e) contains nickel, cobalt, manganese, aluminum, iron, etc., which are raw materials for the positive electrode material, but the precipitate may be dissolved in an acid such as sulfuric acid, hydrochloric acid, or nitric acid to separate valuable metal components using a wet method. When the waste lithium-ion secondary battery to be recycled uses a ternary positive electrode material (NCA, NCM, etc.), nickel, cobalt, manganese, and aluminum may be recovered, and when an iron phosphate positive electrode material (LFP) is used, iron may be recovered.

[0069] In the conventional method of pyrolysis at high temperature, the valuable metal components contained in the positive electrode material cannot be separated using water, and can only be separated through crushing and wet treatment with strong acid. However, in the recycling method according to the present invention, the valuable metal components of the positive electrode material can be simply separated using water. Therefore, the precipitate according to the present invention is in powder form and does not contain metal ions other than Li, Ni, Co, Mn, Al, and Fe, and does not require wet treatment, so it can be easily separated using SO4 2- , F - , Cl - It is not necessary to include an anion such as

[0070] In the case where the cathode material of the waste lithium ion secondary battery to be recycled in the present invention is a ternary cathode material, the recovered precipitate may be a metallic powder containing metallic nickel and cobalt and having magnetic properties, because nickel and cobalt contained in the cathode material may be reduced to a metallic phase by a carbon-thermal reduction reaction caused by the anode material, conductive material, etc. in the battery through a low-temperature pyrolysis process.

[0071] Such metal powder is magnetic, and its saturation magnetization value may be 15 emu / g or more, and more preferably 30 emu / g or more.

[0072] The high content of metals Ni and Co contained in the metal powder as the precipitate according to the present invention are ferromagnetic materials and therefore have a high level of saturation magnetization, but aluminum, manganese oxides, etc. that are not magnetic and remain partially play a role in lowering the saturation magnetization. The metal powder according to the present invention has a low content of residual substances other than Ni and Co and has a relatively high saturation magnetization, preferably 15 emu / g or more, and more preferably 30 emu / g or more. Using such magnetism, oxides contained in the precipitate may be removed through magnetic separation, and only the metal components may be further classified and separated.

[0073] In addition, the metal powder according to the present invention may have an average particle size of 20 μm or less and a standard deviation in particle size distribution of 10 μm or less, as measured through a particle size analyzer using laser diffraction.

[0074] In the conventional high-temperature pyrolysis process, the resultant material is agglomerated after the process due to the high temperature, and a crushing process is unavoidable to powderize it. However, the metal powder according to the present invention is obtained through a low-temperature pyrolysis process, and is characterized by a small particle size, making an additional crushing process unnecessary.

[0075] In addition, the smaller the particle size of the metal powder for recycling such used lithium ion secondary batteries, the more advantageous it is for extracting valuable metals by post-treatment. Therefore, the metal powder of the present invention has an average particle size of 20 μm or less. In addition, the standard deviation in the particle size distribution is uniform at 10 μm or less, making the powder easy to handle.

[0076] On the other hand, the metallic Ni and Co contained in the metal powder according to the present invention are derived from the Ni and Co contained in the positive electrode material of the used lithium ion secondary battery. Therefore, their ratios follow the ratios in the positive electrode material of the used lithium ion secondary battery before pyrolysis. Since the metal powder according to the present invention has a very high recovery rate of Ni and Co from the used lithium ion secondary battery, the ratios of Ni and Co in the used lithium ion secondary battery before pyrolysis do not show a large difference from the ratios of Ni and Co in the metal powder after pyrolysis.

[0077] Therefore, in the metal powder according to the present invention, the molar ratio of metallic Ni to metallic Co (M Ni / M Co , M Ni and M. Co are the molar fractions of metallic Ni and metallic Co in the metal powder, respectively, as the first molar ratio (M1), and the molar ratio of Ni to Co in the positive electrode material of the waste lithium-ion secondary battery before thermal decomposition (m Ni / m Co , m ni and m Co are the molar fractions of Ni and Co in the positive electrode material, respectively, as a second molar ratio (M2). The difference between the first molar ratio and the second molar ratio may be 10% or less of the value of the second molar ratio, and more preferably, may be 5% or less.

[0078] In addition, the valuable metals nickel and cobalt in the metal powder according to the present invention are in a metallic state, and therefore can be easily extracted by a weak acid treatment compared to oxides. Therefore, sulfides, nitrides, or chlorides containing nickel or cobalt can be effectively obtained by wet extraction of the reduced metal powder according to the present invention. Such metal compounds may be used again as raw materials for cathode materials for lithium ion secondary batteries.

[0079] In addition, when the cathode material of the waste lithium ion secondary battery to be recycled in the present invention is an iron phosphate-based cathode material, the recovered precipitate may be a metal powder containing iron metal or iron oxide, because the iron contained in the cathode material may be reduced to a metal phase by a carbothermal reduction reaction through a low-temperature pyrolysis process, as with the ternary cathode material, or may be contained in the precipitate in the form of iron oxide.

[0080] Meanwhile, the suspended matter recovered in the recycling method according to the present invention is a negative electrode material, which may be low-density graphite or carbon powder containing graphite and silica. By collecting and drying the suspended carbon powder, graphite or silicon that can be recycled as a negative electrode material can be recovered.

[0081] Such carbon powder may have an average particle size of 20 μm or less, and a standard deviation in the particle size distribution of 10 μm or less, as measured through a particle size analyzer also using laser diffraction.

[0082] [Example] A waste lithium ion secondary battery having a positive electrode made of a ternary metal (NCM) positive electrode material was treated by the recycling method according to the present invention to recover a first powder. A waste lithium ion secondary battery that had not been discharged was placed in a pyrolysis furnace, and the heat wire temperature of the pyrolysis furnace was adjusted to 300°C or less to induce a self-heating reaction of the waste lithium ion secondary battery. After the self-heating reaction was initiated, the internal temperature was adjusted so that the pyrolysis reaction continued for 12 hours. After the reaction was completed, the powdered material was separated and recovered to obtain a first powder.

[0083] The obtained powder was added to water maintained at 4°C and ultrasonically treated. The treated solution was left for a certain period of time to separate into precipitates and suspended matter. The precipitates, lithium aqueous solution, and suspended matter were then filtered and separated.

[0084] Water was removed from the resulting lithium aqueous solution by evaporation to obtain lithium carbonate. The resulting lithium carbonate powder was subjected to component analysis using X-ray diffraction analysis and ICP-OES (Inductively Coupled Plasma-Optical Emission Spectroscopy). Figure 3 shows the results of the X-ray diffraction analysis, which shows that all of the lithium carbonate powder obtained through the two experiments was pure lithium carbonate, and the ICP-OES results also showed that there were no impurities other than lithium (see Table 1).

[0085] [Table 1]

[0086] The particle size of the recovered precipitate was measured as shown in Figure 4. The precipitate metal powder was generally spherical, and the average particle size of the reduced metal powder was 14.8 μm with no wide distribution.

[0087] FIG. 5 is a graph showing the measurement results of the saturation magnetization of the first powder discharged after the reaction in the pyrolysis furnace was completed and the precipitate separated by dissolving in water.

[0088] It was found that the saturation magnetization value of the precipitated metal powder was significantly higher than that of the powder before dissolution. Compared to the first powder, the precipitate has a high saturation magnetization value (34.02 emu / g) because the lithium carbonate and anode materials graphite and silicon are separated into a lithium aqueous solution and suspended matter, respectively, and contain high amounts of metallic Ni and Co.

[0089] 6 and 7 show the results of a transmission electron microscope image and a diffraction pattern analysis of the precipitate according to the present invention. The diffraction pattern confirmed metallic Ni with an fcc structure.

Claims

1. (a) charging waste lithium ion secondary batteries into a pyrolysis furnace; (b) increasing an internal temperature of the pyrolysis furnace to induce self-heating of the waste lithium ion secondary batteries; (c) sustaining the self-heating reaction of the waste lithium ion secondary batteries; (d) discharging a first powder produced after the self-heating reaction of the waste lithium ion secondary batteries is completed; (e) putting the first powder into water to dissolve the lithium component contained in the first powder, and separating and recovering an aqueous lithium solution, a precipitate that sinks in the aqueous lithium solution, and a floating matter that rises to the surface of the aqueous lithium solution.

2. 2. The method of claim 1, wherein in step (e), the temperature of the water into which the first powder is added is 30° C. or less.

3. 2. The method of claim 1, wherein in step (e), fine bubbles of 20 microns or less are injected into a slurry prepared after the first powder is added to the water.

4. 2. The method for recycling used lithium ion secondary batteries according to claim 1, further comprising the step of evaporating water from the lithium aqueous solution to recover lithium carbonate.

5. 2. The method for recycling used lithium ion secondary batteries according to claim 1, further comprising the step of: adding an alkali to the lithium aqueous solution to increase pH, thereby precipitating and recovering the lithium component as lithium hydroxide.

6. 2. The method of claim 1, further comprising the step of: introducing the precipitate into an acidic aqueous solution to recover an aqueous metal solution in which metal components contained in the precipitate are dissolved.

7. 2. The method for recycling used lithium ion secondary batteries according to claim 1, wherein the precipitate contains metallic nickel and cobalt.

8. The method for recycling used lithium ion secondary batteries according to claim 1 , wherein the precipitate contains metallic iron.

9. The method for recycling used lithium ion secondary batteries according to claim 1, wherein in step (a), the used lithium ion secondary batteries are charged into a pyrolysis furnace together with water.

10. 10. The method for recycling used lithium ion secondary batteries according to claim 9, wherein an amount of water introduced in step (a) is in the range of 1 to 10 parts by mass per 100 parts by mass of a positive electrode material contained in the used lithium ion batteries introduced into a pyrolysis furnace.

11. 2. The method of claim 1, wherein in step (a), the used lithium ion secondary batteries are in a state where they have not been discharged.

12. 2. The method for recycling used lithium ion secondary batteries according to claim 1, wherein in the step (a), the used lithium ion secondary batteries are not subjected to a pulverization process.

13. 2. The method of claim 1, wherein the used lithium ion secondary batteries in the step (a) include used lithium ion secondary batteries that are discarded as defective during a manufacturing process of the lithium ion secondary batteries.

14. 2. The method of claim 1, wherein the used lithium ion secondary batteries in the step (a) include used lithium ion secondary batteries in a powder state that have been disassembled and pulverized.

15. 2. The method of claim 1, wherein in step (b), the internal temperature is 400° C. or less.

16. 2. The method for recycling used lithium ion secondary batteries according to claim 1, wherein the pyrolysis furnace is not heated in step (c).

17. 2. The method for recycling used lithium ion secondary batteries according to claim 1, wherein the step (c) lasts for 10 to 24 hours.

18. 2. The method for recycling used lithium ion secondary batteries according to claim 1, wherein the step (c) is carried out in an inert gas atmosphere.

19. 2. The method for recycling used lithium ion secondary batteries according to claim 1, wherein the precipitate recovered through the method for recycling used lithium ion secondary batteries is a metal powder recovered from used lithium ion secondary batteries, the metal powder containing metallic Ni and Co and having magnetic properties.

20. The metal powder recovered from waste lithium ion secondary batteries according to claim 19, wherein the metal powder has a saturation magnetization value of 15 emu / g or more.

21. 20. The metal powder recovered from used lithium ion secondary batteries according to claim 19, wherein the metal powder has an average particle size of 20 μm or less and a standard deviation in particle size distribution of 10 μm or less, as measured by a particle size analyzer using laser diffraction.

22. In the metal powder, the molar ratio of the metal Ni to the metal Co (M Ｎｉ / M Ｃｏ , M. Ｎｉ and M. Ｃｏ are the molar fractions of the metal Ni and the metal Co in the metal powder, respectively, in a first molar ratio (M １ ), and in the positive electrode material of the waste lithium ion secondary battery before thermal decomposition, the molar ratio of Ni to Co (m Ｎｉ / m Ｃｏ , m ｎｉ And Ｃｏ are the mole fractions of Ni and Co in the positive electrode material, respectively, in a second molar ratio (M ２ 20. The metal powder recovered from waste lithium ion secondary batteries according to claim 19, wherein the difference between the first molar ratio and the second molar ratio is 10% or less of the value of the second molar ratio.

23. The metal powder does not contain metal ions other than Li, Ni, Co, Fe, and Al, and does not contain F － and Cl － The metal powder recovered from waste lithium ion secondary batteries according to claim 19, which does not contain anions of the formula:

24. 2. The method for recycling used lithium ion secondary batteries according to claim 1, wherein the precipitate recovered through the method for recycling used lithium ion secondary batteries is an iron powder recovered from used lithium ion secondary batteries, the iron powder including metallic iron or iron oxide.

25. 2. The method for recycling used lithium ion secondary batteries according to claim 1, wherein the suspended matter separated and recovered through the method for recycling used lithium ion secondary batteries is a carbon powder recovered from used lithium ion secondary batteries, the carbon powder comprising graphite or graphite and silica.

26. The carbon powder recovered from waste lithium ion secondary batteries according to claim 25, wherein the carbon powder has an average particle size of 20 μm or less and a standard deviation in particle size distribution of 10 μm or less, as measured by a particle size analyzer using laser diffraction.

27. 2. A recycled powder of used lithium ion secondary batteries, comprising lithium carbonate, metallic nickel and metallic cobalt, as the first powder produced by the method for recycling used lithium ion secondary batteries according to claim 1.

Images