Method for remanufacturing positive electrode active material for lithium secondary battery through pretreatment and upcycling of waste positive electrode material, and positive electrode active material produced thereby

Abstract

The present invention relates to a method for remanufacturing a positive electrode active material for a lithium secondary battery using a waste positive electrode material and a positive electrode active material for a lithium secondary battery manufactured thereby, the method comprising: (a) a pretreatment step of, from a waste positive electrode material comprising a positive electrode active material, a binder, and a conductive material, removing impurities such as the binder and the conductive material and separating the positive electrode active material; and (b) a step of mixing the separated positive electrode active material with a lithium precursor and a nickel precursor and subjecting the mixture to heat treatment so as to synthesize the positive electrode active material. According to the present invention, pretreatment using N-methyl-2-pyrrolidone (NMP) or the like is performed without pulverizing and destroying a waste positive electrode material unlike the prior art, so as to effectively remove impurities adsorbed on the surface of the waste positive electrode material and interfering with the recycling process, after which the structure of the waste positive electrode material is restored, the content of nickel is increased to increase the capacity compared to conventional waste positive electrode materials, and through upcycling which converts positive electrode active material particles from secondary particles to primary particles and re-synthesizes same into positive electrode active materials having excellent degradation durability, positive electrode active materials having much better electrochemical performance than the prior art can be manufactured.

Description

Method for remanufacturing cathode active material for lithium secondary batteries through pretreatment and upcycling of waste cathode material and cathode active material manufactured thereby

[0001] The present invention relates to a method for manufacturing a positive electrode active material for a lithium secondary battery by recycling waste positive electrode material of a lithium secondary battery, and to a positive electrode active material for a lithium secondary battery manufactured thereby.

[0002] Lithium, considered a rare element, is the lightest metal and has a high specific capacity of 3.86 Ah / g and a very low electrode potential of -3.04 V compared to the standard hydrogen electrode (SHE), making it an ideal cathode material for high-voltage / high-energy batteries.

[0003] Lithium secondary batteries were first commercialized in 1991 and have been widely used in portable electronic devices. Recently, they have been used as power supplies for next-generation eco-friendly vehicles such as electric vehicles. Due to the rapid expansion of the plug-in hybrid electric vehicle (PHEV), hybrid electric vehicle (HEV), and electric vehicle (EV) markets, the demand for lithium secondary batteries is expected to increase rapidly in the future.

[0004] As the electric vehicle market grows rapidly, it is expected that approximately 1,000 GWh of waste batteries will be generated by 2030. Scrap of defective waste batteries generated during the lithium secondary battery manufacturing process, waste cathode materials, or waste scrap (black powder, etc.) of used lithium secondary batteries contain valuable metals such as nickel, cobalt, and manganese. Therefore, the importance of the resource recycling industry for waste batteries is increasing day by day due to the high dependence on imports for battery raw materials, price increases, and supply and demand instability.

[0005] Nickel-cobalt-manganese composite metal oxide cathode materials, which account for more than 60% of the cost of lithium secondary batteries, are no different from pure materials purified and recovered through recycling of used batteries. Therefore, secondary battery recycling is expected to become an essential technology as the size of the mid- to large-sized battery market expands, not only from the perspective of resource circulation but also in terms of securing cost stability of lithium secondary batteries.

[0006] Spent battery materials contain substances such as carbon, binders, metal oxides, and other metals used in the battery manufacturing process. Research is continuously being conducted to develop a waste cathode recycling technology that can remove these impurities and efficiently recover valuable metals. However, the existing waste cathode recycling technology is mainly a method that completely destroys the waste cathode to recover valuable metals and then uses them to manufacture new cathode active materials. This method has the disadvantage of high costs for resource recycling and excessive carbon dioxide emissions.

[0007] The technical problem to be solved by the present invention is to provide a method for recovering valuable metals from waste cathode materials in an eco-friendly and economically efficient manner by significantly reducing carbon dioxide emissions during the waste cathode material recycling process without crushing and destroying waste cathode materials unlike conventional technologies, and to remanufacture a cathode active material for a lithium secondary battery having significantly improved electrochemical performance through upcycling, and a cathode active material for a lithium secondary battery manufactured thereby.

[0008] In order to achieve the above technical task, the present invention proposes a method for remanufacturing a cathode active material for a lithium secondary battery using a waste cathode material, comprising (a) a pretreatment step of removing impurities such as a binder and a conductive material from a waste cathode material including a cathode active material, a binder, and a conductive material and separating the cathode active material, and (b) a step of mixing the separated cathode active material with a lithium precursor and a nickel precursor and heat-treating the mixture to synthesize the cathode active material.

[0009]

[0010] In the above step (a), a pre-treatment process is performed to separate the positive electrode active material from the waste positive electrode material by removing polymer and carbon impurities such as binder and conductive material from the waste positive electrode material composed of positive electrode active material, binder and conductive material.

[0011]

[0012] At this time, in the above step (a), the waste cathode material provided for pretreatment is characterized in that it is a waste cathode material that has not undergone a crushing or shredding process after being separated from the current collector.

[0013]

[0014] In the above step (a), the process of separating the positive electrode active material from the waste positive electrode material can be carried out by placing the waste positive electrode material in a solvent and performing ultrasonic treatment to remove the binder and / or conductive material bound to the positive electrode active material from the positive electrode active material. In this case, the solvent is preferably N-Methyl-2-Pyrrolidone (NMP).

[0015]

[0016] Furthermore, in the step (a), a process of heat-treating the positive electrode active material obtained by ultrasonic treatment in a solvent may be additionally performed to remove impurities such as binders and conductive agents remaining on the surface of the positive electrode active material by thermal decomposition even after ultrasonic treatment in a solvent.

[0017] At this time, the heat treatment temperature and heat treatment time of the positive electrode active material from which the impurities have been removed are not particularly limited as long as the temperature and time are sufficient to calcinate and remove the polymer and carbon-based impurities remaining on the surface of the positive electrode active material. For example, the heat treatment may be performed for 1 to 5 hours in a temperature range of 250 to 500°C.

[0018]

[0019] Meanwhile, the cathode active material included in the waste cathode material is a compound capable of reversible intercalation and deintercalation of lithium, and specifically may include a lithium composite metal oxide containing lithium and one or more metals such as nickel, cobalt, manganese, or aluminum. More specifically, the lithium composite metal oxide may be a lithium-manganese oxide (LiMnO2, LiMn2O4, etc.), a lithium-cobalt oxide (LiCoO2, etc.), a lithium-nickel oxide (LiNiO2, etc.), a lithium-nickel-manganese oxide (LiNi 1-X Mn X O2(0 <X<1), LiMn 2-x NixO4(0<x<2) etc.), lithium-nickel-cobalt oxide (LiNi 1-x CoxO2(0 <x<1) 등), 리튬-망간-코발트계 산화물(예를 들면, LiCo 1-x Mn x O2(0 <x<1), LiMn 2-x Co x O4(0<x<2) etc.), lithium-nickel-manganese-cobalt oxide (Li(Ni a Co b Mn c )O2(0<a<1, 0<b<1, 0<c<1, a+b+c=1), Li(Ni a Co b Mn c )O4(0<a<2, 0<b<2, 0<c<2, a+b+c=2) etc.), or lithium-nickel-cobalt-manganese-transition metal (M) oxide (Li(Ni a Co b Mn c M d)O2(M is selected from the group consisting of Al, Fe, V, Cr, Ti, Ta, Mg and Mo, and 0<a<1, 0<b<1, 0<c<1, 0<d<1, a+b+c+d=1) etc.), and one or more compounds of these may be included.

[0020]

[0021] In addition, the binder included in the above-mentioned waste cathode material is an element that contributes to the bonding of the active material and the conductive material and the bonding to the current collector, and may include polyvinylidene fluoride, polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinyl pyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene terpolymer (EPDM), sulfonated EPDM, styrene-butadiene rubber, fluororubber, and combinations of two or more thereof.

[0022]

[0023] In addition, the conductive material included in the waste cathode material may include carbon-based materials such as graphite, carbon nanotubes, carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, and thermal black; conductive fibers such as carbon fibers or metal fibers; metal powders such as fluorinated carbon, aluminum, and nickel powders; conductive metal oxides such as titanium oxide; and conductive polymers such as polyphenylene derivatives. Specific examples of commercially available conductive materials include acetylene black series products such as Chevron Chemical Company, Denka Singapore Private Limited, and Gulf Oil Company products), Ketjenblack, EC series (Armak Company products), Vulcan XC-72 (Cabot Company products), and Super P (Timcal products).

[0024]

[0025] Next, in the step (b), an upcycling process is performed in which a lithium precursor and a nickel precursor are added to the positive electrode active material obtained by pretreating the waste positive electrode material in the previous step and heat-treating the same to synthesize a positive electrode active material with an increased nickel content.

[0026]

[0027] For reference, in the present specification, upcycling does not simply refer to recycling that restores the structure of waste positive electrode active materials with relatively low nickel content, but also refers to a technology that increases the nickel content of the positive electrode active material to create a new positive electrode active material with improved capacity.

[0028]

[0029] More specifically, in the step (b), a nickel precursor is added together with a lithium precursor to the cathode active material separated from the waste cathode material and heat-treated to increase the nickel content and synthesize a cathode active material with improved capacity, and a cathode active material particle having a secondary particle form in which a large number of fine cathode active material particles are aggregated is single-crystallized to enable it to withstand the high-pressure rolling process during cathode manufacturing, thereby obtaining a cathode active material suitable for manufacturing a lithium secondary battery having a high energy density.

[0030]

[0031] At this time, the heat treatment performed after mixing the positive electrode active material separated from the waste positive electrode material in the step (b) with the lithium precursor and the nickel precursor is preferably performed for 3 to 5 hours in a temperature range of 900 to 1000°C, at which a sintering phenomenon occurs between secondary particles, so that a positive electrode active material in the form of coarse primary particles composed of single crystals can be synthesized from a positive electrode active material in the form of secondary particles in which fine positive electrode active material particles are aggregated.

[0032] In addition, after the first heat treatment for the above single crystallization, a second heat treatment is performed at a temperature range of 750 to 850°C for 5 to 20 hours so that a positive electrode active material with a high layered crystallinity can be synthesized by performing the heat treatment at a lower temperature for a longer period of time, thereby obtaining an upcycled positive electrode active material.

[0033]

[0034] Meanwhile, in the step (b), the lithium precursor may be at least one selected from the group consisting of lithium-containing oxides, sulfates, nitrates, acetates, carbonates, oxalates, citrates, halide hydroxides, and oxyhydroxides. In addition, the nickel precursor may be at least one selected from the group consisting of nickel-containing oxides, sulfates, nitrates, acetates, carbonates, oxalates, citrates, halide hydroxides, and oxyhydroxides.

[0035]

[0036] In addition, the content of the lithium precursor and nickel precursor mixed with the positive electrode active material separated from the waste positive electrode material to synthesize the positive electrode active material in the above step (b) is not particularly limited, and the mixing ratio of the positive electrode active material separated from the waste positive electrode material, the lithium precursor, and the nickel precursor can be set according to the composition of the positive electrode active material to be finally synthesized according to the present invention.

[0037]

[0038] And, in another aspect of the present invention, a positive electrode active material for a lithium secondary battery is provided manufactured by a method for remanufacturing a positive electrode active material for a lithium secondary battery using the waste positive electrode material.

[0039] According to the present invention, unlike the conventional technology, waste cathode materials are not destroyed by crushing, but rather pretreated using N-methyl-2-pyrrolidone (NMP) or the like to effectively remove impurities that are adsorbed on the surface of the waste cathode material and interfere with the recycling process, and then the structure of the waste cathode material is restored and the nickel content is increased to increase the capacity compared to the existing waste cathode material, and the cathode active material particles are converted from secondary particles to primary particles and re-synthesized into cathode active materials with excellent deterioration durability, thereby manufacturing a cathode active material having electrochemical performance much superior to that of the conventional technology through upcycling.

[0040] Figure 1 is a conceptual diagram sequentially illustrating the steps of manufacturing a new cathode active material in the form of single crystal primary particles through an upcycling step of pretreating waste cathode material with N-methyl-2-pyrrolidone (NMP), adding a lithium precursor and a nickel precursor, and then performing a heat treatment in the present invention.

[0041] Figure 2 is a scanning electron microscope (SEM) photograph showing the microstructure of a waste cathode active material before and after pretreatment using NMP in an example of the present invention.

[0042] Figure 3 shows the thermogravimetric analysis (TGA) results for each of the waste cathode active materials and commercial NCM622 before and after pretreatment using NMP in the present example.

[0043] Figure 4 shows the results of a charge / discharge experiment on a lithium secondary battery having a positive electrode including each of the waste positive electrode active materials before and after pretreatment using NMP in the present invention.

[0044] Fig. 5(a) is a scanning electron microscope (SEM) photograph of a cathode active material that was heat-treated for structural recovery and shape control without a pretreatment process using NMP in an example of the present invention, and Fig. 5(b) is a result of a charge / discharge experiment on a lithium secondary battery equipped with a cathode including the cathode active material.

[0045] Fig. 6(a) is a scanning electron microscope (SEM) photograph of a positive electrode active material that was subjected to a pretreatment process using NMP and heat treatment for structural recovery and shape control in an example of the present invention, and Fig. 6(b) is a result of a charge / discharge experiment on a lithium secondary battery equipped with a positive electrode including the positive electrode active material.

[0046] In describing the present invention, if it is determined that a detailed description of a related known function or configuration may unnecessarily obscure the gist of the present invention, the detailed description will be omitted.

[0047]

[0048] Embodiments according to the concept of the present invention may be modified in various ways and take various forms. Therefore, specific embodiments are illustrated in the drawings and described in detail in this specification or application. However, this is not intended to limit embodiments according to the concept of the present invention to specific disclosed forms, and it should be understood that all modifications, equivalents, and alternatives included within the spirit and technical scope of the present invention are included.

[0049]

[0050] The terminology used herein is for the purpose of describing specific embodiments only and is not intended to limit the present invention. The singular expressions include plural expressions unless the context clearly indicates otherwise. In this specification, it should be understood that the terms "comprises" or "has" indicate the presence of a described feature, number, step, operation, component, part, or combination thereof, but do not preclude the presence or addition of one or more other features, numbers, steps, operations, components, parts, or combinations thereof.

[0051]

[0052] Hereinafter, the present invention will be described in more detail by way of examples.

[0053]

[0054] The embodiments described herein may be modified in various ways, and the scope of this specification is not limited to the embodiments described below. The embodiments described herein are provided to provide a more complete description of this specification to those of ordinary skill in the art.

[0055]

[0056] <Example>

[0057] As illustrated in Fig. 1, in this example, a new cathode active material in the form of a single crystal primary particle was manufactured through an upcycling process in which waste cathode material was pretreated with N-methyl-2-pyrrolidone (NMP), a lithium precursor and a nickel precursor were added, and heat treatment was performed.

[0058]

[0059] More specifically, after preparing waste cathode materials scraped from electrodes, waste cathode powder was added to NMP solvent at a weight ratio of 1:10 and an ultrasonic process was performed at 38.4 KHz for 1 hour. After the NMP treatment, heat treatment was performed at 400 ℃ for 2 hours in an oxygen atmosphere. The waste cathode materials prepared in this way were mixed with lithium hydroxide and nickel oxide according to the composition of the final cathode material to be synthesized, and then a primary heat treatment was performed at 950 ℃ for 3 hours and a secondary heat treatment was performed at 750 ℃ ​​for 10 hours to manufacture a cathode active material.

[0060]

[0061] Table 1 below shows the results of ICP (inductively coupled plasma spectrometry) analysis before and after NMP pretreatment of the waste cathode material used in this example. According to this, the waste cathode material is estimated to have a composition of NCM523.

[0062]

[0063] [Table 1]

[0064]

[0065]

[0066] Figure 2 is a scanning electron microscope (SEM) photograph showing the microstructure of a waste cathode active material before and after pretreatment using NMP in an example of the present invention.

[0067] Referring to Fig. 2, it was confirmed that the dark-colored impurities present on the surface of the waste cathode material before NMP treatment were removed after NMP treatment.

[0068]

[0069] Figure 3 shows the thermogravimetric analysis (TGA) results for each of the waste cathode active materials and commercial NCM622 before and after pretreatment using NMP in the present example.

[0070] Referring to Fig. 3, in the case of the waste cathode material before NMP treatment, a large weight loss occurs due to the removal of impurity materials (conductive material and binder) in the temperature range of 500 to 600°C, but in the case of the waste cathode material after NMP treatment, the weight loss was relatively small, and it was confirmed from this that carbon impurities were effectively removed from the waste cathode material through NMP treatment.

[0071]

[0072] Figure 4 and Table 2 show the results of charge / discharge experiments on lithium secondary batteries equipped with positive electrodes each including waste positive electrode active materials before and after pretreatment using NMP in the present invention.

[0073] Referring to Fig. 4 and Table 2, it was confirmed that the electrochemical performance was noticeably improved from 154 mAh / g to 171.8 mAh / g by removing only impurities from the waste cathode material through NMP treatment.

[0074]

[0075] [Table 2]

[0076]

[0077]

[0078] Fig. 5(a) is a scanning electron microscope (SEM) photograph of a cathode active material that was heat-treated for structural recovery and shape control without a pretreatment process using NMP in the present invention, and Fig. 5(b) and Table 3 show the results of a charge / discharge experiment on a lithium secondary battery equipped with a cathode including the cathode active material.

[0079]

[0080] Referring to Fig. 5(b) and Table 3, the discharge capacity of the secondary battery using the positive electrode active material manufactured through the upcycling process directly without the pretreatment process using NMP was confirmed to be 161.2 mAh / g, which falls short of the target NCM 622 capacity (~180 mAh / g).

[0081]

[0082] [Table 3]

[0083]

[0084]

[0085] In addition, according to Fig. 5(a), the positive electrode active material particles finally obtained were found to have maintained the secondary particle shape, not the single crystal primary particle shape, and thus upcycling was not performed.

[0086]

[0087] Fig. 6(a) is a scanning electron microscope (SEM) photograph of a positive electrode active material that was subjected to a pretreatment process using NMP and heat treatment for structural recovery and shape control in an example of the present invention, and Fig. 6(b) and Table 4 show the results of a charge / discharge experiment on a lithium secondary battery equipped with a positive electrode including the positive electrode active material.

[0088]

[0089] [Table 4]

[0090]

[0091]

[0092] According to Fig. 6(a) and Fig. 6(b) and Table 4, when the waste cathode material was pretreated using NMP and then the upcycling process was performed, single crystals with a particle size of 5 to 6 ㎛ were synthesized, and the discharge capacity reached the target of 180 mAh / g, confirming that upcycling was achieved, unlike the cathode active material that did not undergo the pretreatment process.

[0093]

[0094] While the embodiments of the present invention have been described above with reference to the attached drawings, those skilled in the art will appreciate that the present invention can be implemented in other specific forms without altering the technical spirit or essential characteristics thereof. Therefore, the embodiments described above should be understood to be illustrative in all respects and not restrictive.

[0095] The present invention can manufacture a cathode active material having electrochemical performance much superior to that of conventional technologies through pretreatment and upcycling of waste cathode materials.

Claims

1. (a) a pretreatment step for removing impurities including a binder and a conductive agent from a waste cathode material including a cathode active material, a binder and a conductive agent, and separating the cathode active material; and (b) a step of synthesizing a cathode active material by mixing and heat-treating the cathode active material, a lithium precursor, and a nickel precursor; A method for remanufacturing a cathode active material for a lithium secondary battery using waste cathode material.

2. In paragraph 1, In the above step (a), The above-mentioned waste cathode material is characterized by being sonicated in a solvent containing N-Methyl-2-Pyrrolidone (NMP) to remove impurities including a binder and a conductive agent and to separate the cathode active material. A method for remanufacturing a cathode active material for a lithium secondary battery using waste cathode material.

3. In paragraph 2, A method characterized by heat-treating a cathode active material separated from the above waste cathode material. A method for remanufacturing a cathode active material for a lithium secondary battery using waste cathode material.

4. In paragraph 1, In the above step (b), The above lithium precursor is at least one selected from the group consisting of lithium-containing oxides, sulfates, nitrates, acetates, carbonates, oxalates, citrates, halide hydroxides and oxyhydroxides, The nickel precursor is characterized in that it is at least one selected from the group consisting of nickel-containing oxides, sulfates, nitrates, acetates, carbonates, oxalates, citrates, halide hydroxides and oxyhydroxides. A method for remanufacturing a cathode active material for a lithium secondary battery using waste cathode material.

5. In paragraph 1, The above lithium precursor is lithium acetate, The nickel precursor is characterized in that it is nickel oxide. A method for remanufacturing a cathode active material for a lithium secondary battery using waste cathode material.

6. A cathode active material for a lithium secondary battery manufactured by a method according to any one of claims 1 to 5.

Images