KR20250089964A - Method for remanufacturing cathode active material for lithium secondary battery through pretreatment and upcycling of waste cathode active material and cathode active material manufactured thereby - Google Patents

Abstract

The present invention relates to a method for remanufacturing a cathode active material for a lithium secondary battery using a waste cathode material, and a cathode active material for a lithium secondary battery manufactured thereby, comprising (a) a pretreatment step of removing impurities such as 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 mixing the separated cathode active material with a lithium precursor and a nickel precursor and performing heat treatment to synthesize the cathode active material. According to the present invention, unlike the prior art, the waste cathode material is not destroyed by crushing, but is pretreated using N-Methyl-2-Pyrrolidone (NMP), etc., to effectively remove impurities that are adsorbed on the surface of the waste cathode material and interfere with the recycling process, and then, through upcycling, 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 to resynthesize the cathode active material with excellent deterioration durability, thereby achieving much better performance than the prior art. A cathode active material having electrochemical performance can be manufactured.

Description

Method for remanufacturing cathode active material for lithium secondary battery through preprocessing and upcycling of waste cathode material and cathode active material manufactured thereby {METHOD FOR REMANUFACTURING CATHODE ACTIVE MATERIAL FOR LITHIUM SECONDARY BATTERY THROUGH PRETREATMENT AND UPCYCLING OF WASTE CATHODE ACTIVE MATERIAL AND CATHODE ACTIVE MATERIAL MANUFACTURED THEREOF}

The present invention relates to a method for manufacturing a cathode active material for a lithium secondary battery by recycling waste cathode materials from lithium secondary batteries, and to a cathode active material for a lithium secondary battery manufactured thereby.

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.

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 eco-friendly next-generation automobiles 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.

As the electric vehicle market grows rapidly, it is expected that about 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 import dependency on battery raw materials, price increases, and supply and demand instability.

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

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 mainly involves completely destroying the waste cathode to recover valuable metals and then using them to manufacture new cathode active materials. This method has the disadvantage of high costs required for resource recycling and excessive carbon dioxide emissions.

Korean Patent Publication No. 10-2022-0070764 (Publication Date: 2022.05.31) Korean Patent Registration No. 10-1328585 (Registration Date: 2013.11.06)

The technical problem to be solved by the present invention is to provide a method for recovering valuable metals from waste cathode materials, which is not only environmentally friendly but also economically efficient by significantly reducing carbon dioxide emissions during the waste cathode material recycling process without crushing and destroying waste cathode materials unlike the prior art, and for remanufacturing 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.

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, the method 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 performing a heat treatment to synthesize the cathode active material.

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

At this time, in the 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 crushing process after being separated from the current collector.

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. At this time, the solvent is preferably N-Methyl-2-Pyrrolidone (NMP).

Furthermore, in the step (a), a process of heat-treating the positive electrode active material obtained by ultrasonic treatment in a solvent can 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.

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 at a temperature range of 250 to 500°C for 1 to 5 hours.

Meanwhile, the cathode active material included in the above-mentioned waste cathode material is a compound capable of reversible intercalation and deintercalation of lithium, and specifically may include a lithium composite metal oxide including lithium and one or more metals such as nickel, cobalt, manganese, or aluminum. More specifically, the lithium composite metal oxide is a lithium-manganese oxide (LiMnO ₂ , LiMn ₂ O ₄ , etc.), a lithium-cobalt oxide (LiCoO ₂ , etc.), a lithium-nickel oxide (LiNiO ₂ , etc.), a lithium-nickel-manganese oxide (LiNi _1-x Mn _X O ₂ (0<X<1), LiMn _2-x NixO ₄ (0＜x＜2)), etc.), a lithium-nickel-cobalt oxide (LiNi _1-x CoxO ₂ (0<x<1)), a lithium-manganese-cobalt oxide (for example, LiCo _1-x Mn _x O ₂ (0<x<1), LiMn _2-x Co _x O ₄ (0＜x＜2)), etc.), a lithium-nickel-manganese-cobalt oxide (Li(Ni _a Co _b Mn _c )O ₂ (0＜a＜1, 0＜b＜1, 0＜c＜1, a+b+c=1), Li(Ni _a Co _b Mn _c )O ₄ (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 )O ₂ (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.

In addition, the binder included in the 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.

In addition, the conductive material included in the above-mentioned waste cathode material may be a carbon-based material such as graphite, carbon nanotubes, carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, thermal black, etc.; conductive fibers such as carbon fibers or metal fibers; metal powders such as fluorinated carbon, aluminum, and nickel powder; 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 (Chevron Chemical Company, Denka Singapore Private Limited, Gulf Oil Company products, etc.), Ketjenblack, EC series (Armak Company product), Vulcan XC-72 (Cabot Company product), and Super P (Timcal product).

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 it to synthesize a positive electrode active material with an increased nickel content.

For reference, in the specification of this document, upcycling does not simply mean 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.

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 plurality of fine cathode active material particles having a secondary particle form in which the cathode active material particles are aggregated are single-crystallized to enable the cathode to withstand a high-pressure rolling process during the cathode manufacturing process, thereby obtaining a cathode active material suitable for the manufacture of a lithium secondary battery having a high energy density.

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

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 cathode active material with a high layered crystallinity can be synthesized by performing the heat treatment at a lower temperature for a long period of time, thereby obtaining an upcycled cathode active material.

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.

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

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

According to the present invention, unlike the conventional technology, waste cathode materials are not destroyed by crushing, but are pretreated using N-methyl-2-pyrrolidone (NMP), etc., thereby effectively removing impurities that are adsorbed to 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.

Figure 1 is a conceptual diagram sequentially illustrating the steps of manufacturing a new cathode active material in the form of primary single-crystal particles through an upcycling step of pretreating waste cathode material with N-methyl-2-pyrrolidone (NMP), then adding a lithium precursor and a nickel precursor and performing a heat treatment in an example of the present invention.
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.
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 invention.
Figure 4 shows the results of a charge/discharge experiment on a lithium secondary battery equipped with a cathode including each of the waste cathode active materials before and after pretreatment using NMP in the present invention.
FIG. 5(a) is a scanning electron microscope (SEM) image 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.
Fig. 6(a) is a scanning electron microscope (SEM) image of a cathode 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 cathode including the cathode active material.

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.

Since embodiments according to the concept of the present invention can have various changes and can take various forms, 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 it includes all modifications, equivalents, or substitutes included in the spirit and technical scope of the present invention.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the present invention. The singular expression includes the plural expression unless the context clearly indicates otherwise. It should be understood that, as used herein, the terms "comprises" or "has" and the like are intended to specify the presence of a described feature, number, step, operation, component, part, or combination thereof, but do not exclude in advance the possibility of the presence or addition of one or more other features, numbers, steps, operations, components, parts, or combinations thereof.

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

The embodiments according to this specification can be modified in many different forms, and the scope of this specification is not construed as being limited to the embodiments described below. The embodiments of this specification are provided to more completely explain this specification to a person having average knowledge in the art.

<Example>

As illustrated in Fig. 1, in this example, a novel cathode active material in the form of single-crystal primary particles 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 then heat-treated.

More specifically, after preparing the waste cathode material scraped from the electrode, the waste cathode material powder was added to the 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 material thus prepared, lithium hydroxide, and nickel oxide were mixed according to the composition of the final cathode material to be synthesized, and then the first heat treatment was performed at 950 ℃ for 3 hours and the second heat treatment was performed at 750 ℃ for 10 hours to manufacture the cathode active material.

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.

[Table 1]

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.

Referring to Figure 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.

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 invention.

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 from this, it was confirmed that carbon impurities were effectively removed from the waste cathode material through NMP treatment.

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

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

[Table 2]

FIG. 5(a) is a scanning electron microscope (SEM) image 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.

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).

[Table 3]

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

Fig. 6(a) is a scanning electron microscope (SEM) image of a cathode 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 cathode including the cathode active material.

[Table 4]

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 180 mAh/g, confirming that upcycling was achieved, unlike the cathode active material that did not undergo the pretreatment process.

Above, the embodiments of the present invention have been described with reference to the attached drawings, but those skilled in the art to which the present invention pertains will understand that the present invention can be implemented in other specific forms without changing the technical idea or essential features thereof. Therefore, it should be understood that the embodiments described above are exemplary in all respects and not restrictive.

Claims (6)

(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.
In the first paragraph,
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.
In the second paragraph,
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.
In the first paragraph,
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.
In the first paragraph,
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.
A cathode active material for a lithium secondary battery manufactured by a method according to any one of claims 1 to 5.