KR20240040270A - Method for rcycling cathode active material and rycycled cathode active material - Google Patents

Abstract

The present invention relates to a method for regenerating a positive electrode active material and a positive electrode active material recovered therefrom. More specifically, the present invention relates to a method of recovering the positive electrode active material by heat treating a waste positive electrode including a current collector and a positive electrode active material layer coated thereon under an oxygen atmosphere; A method of regenerating a positive electrode active material comprising the step of washing the recovered positive electrode active material with a washing solution, filtering it, and separating it into solids and a primary filtrate, wherein some of the recovered positive electrode active material is washed with the primary filtrate and then filtered to produce solids and 2. A method of regenerating a positive electrode active material comprising the step of separating it into a secondary filtrate. and a positive electrode active material recycled therefrom.
According to the present invention, the F component remaining on the surface of the recycled positive electrode active material is washed in multiple stages with a small amount of washing liquid and its filtrate, thereby significantly reducing the generation of wastewater and greatly shortening the washing time, resulting in loss of Li and increase in fine particles in the functional coating layer and lattice. It is environmentally friendly because it does not use acid, and process costs are reduced because there is no need for neutralization and wastewater treatment. There are no discarded metal elements because the cathode active material is recycled without decomposition, and it is recovered because the current collector is not dissolved. is possible, and there is no risk of toxic gas generation or explosion as it does not use organic solvents, and a method of regenerating positive electrode active materials suitable for mass production using easy-to-manage processes such as heat treatment or sedimentation, and electrochemical performance, electrochemical performance, and It has the effect of providing a positive electrode active material with excellent resistance and capacity characteristics.

Description

Method for regenerating positive electrode active material and positive active material recovered therefrom {METHOD FOR RCYCLING CATHODE ACTIVE MATERIAL AND RYCYCLED CATHODE ACTIVE MATERIAL}

The present invention relates to a method for regenerating a cathode active material and a cathode active material regenerated therefrom. More specifically, the present invention relates to a method for greatly reducing the generation of wastewater by washing the F component remaining on the surface of the regenerated cathode active material in multiple stages with a small amount of washing liquid and its filtrate. At the same time, the cleaning time is greatly shortened to minimize the loss of Li and the increase in fine particles in the functional coating layer and lattice. It is eco-friendly because it does not use acid, and the process cost is reduced because there is no need for neutralization and wastewater treatment, and it does not decompose the positive electrode active material. There are no metal elements that are discarded as they are recycled, recovery is possible because the current collector does not dissolve, there is no risk of toxic gases or explosions because no organic solvents are used, and by using processes that are easy to manage such as heat treatment or precipitation, It relates to a method for regenerating a positive electrode active material suitable for mass production and a positive electrode active material regenerated from the same with excellent electrochemical performance, resistance characteristics, and capacity characteristics.

Lithium secondary batteries largely consist of a positive electrode whose positive active material layer is coated on a metal foil such as aluminum, a negative electrode whose negative active material layer is coated on a metal foil such as copper, a separator that prevents the positive electrode and negative electrode from mixing with each other, and between the positive electrode and the negative electrode. It consists of an electrolyte solution that allows lithium ions to move.

The positive electrode active material layer mainly uses lithium-based oxide as an active material, and the negative electrode active material layer mainly uses carbon material as an active material. The lithium-based oxide generally contains rare metals such as cobalt, nickel, or manganese, and is used. Much research is being conducted to recover and recycle rare metals from the anodes of lithium secondary batteries that are discarded or from the anode scraps generated during the lithium secondary battery manufacturing process (hereinafter referred to as 'waste anodes').

Most conventional techniques for recovering rare metals from waste anodes include dissolving the waste anode in hydrochloric acid, sulfuric acid, or nitric acid, then extracting cobalt, manganese, nickel, etc. with an organic solvent and using them as raw materials for synthesizing positive electrode active materials. .

However, the extraction method of rare metals using acid has the problem of environmental pollution, requires a neutralization process and a wastewater treatment process, which significantly increases the process cost, and has the disadvantage of not being able to recover lithium, the main metal of the positive electrode active material.

In order to overcome these shortcomings, a direct recycling method has recently been studied in which waste cathodes are directly recycled into cathode active materials without decomposing the cathode active materials. This method largely involves calcination, solvent dissolution, and aluminum recycling. About four types are being introduced, including foil dissolution, crushing and screening.

However, although the above firing method is a simple process, it has the disadvantage of generating foreign substances such as LiF, which reduces the output performance of the battery, on the surface of the recycled positive electrode active material, generating waste gas, and consuming large amounts of energy. In particular, in order to remove foreign substances such as LiF, there is no choice but to use an excessive amount of washing water. In this case, not only the same amount of waste water is generated, but also the loss of Li in the functional coating layer and lattice of the recycled positive electrode active material and the increase in fine particles due to washing appear to be a major problem.

In addition, the solvent dissolution method can obtain a recycled positive electrode active material with a relatively clean surface, but the solvent such as N-methyl-2-pyrrolidone (NMP) used to dissolve the binder is a toxic gas and has the risk of explosion, so its stability is low. It has the disadvantage of requiring a poor and expensive solvent recovery process.

In addition, the aluminum foil dissolution method has good process stability, low process cost, and easy binder removal, but foreign substances that are difficult to remove are generated on the surface of the recycled positive electrode active material, and hydrogen gas is generated during the removal of the aluminum foil, raising the risk of explosion. There is a downside to this.

Lastly, the crushing and screen method has the advantage of being the simplest process, but it is difficult to completely separate the current collector and the positive electrode active material, and the particle size distribution of the positive electrode active material changes during the crushing process and the binder remains, resulting in recycled positive electrode active material. There is a disadvantage that the battery characteristics deteriorate.

Therefore, there is an urgent need to develop a method for safely recycling positive electrode active materials with improved output performance at low cost and in an environmentally friendly manner, without discarding metal elements from waste positive electrodes.

In order to solve the problems of the prior art as described above, the present invention greatly reduces the generation of wastewater by multi-step washing the F component remaining on the surface of the recycled positive electrode active material with a small amount of washing liquid and the filtrate, and at the same time greatly shortens the washing time to form a functional coating layer. It minimizes the loss of Li and the increase in fine particles in the lattice, and is environmentally friendly because it does not use acid. Process costs are reduced because there is no need for neutralization and wastewater treatment. The positive electrode active material is recycled without decomposition, so there are no discarded metal elements. , recovery is possible because the current collector is not dissolved, there is no risk of toxic gas generation or explosion because it does not use organic solvents, and it is a method of regenerating positive electrode active materials suitable for mass production by using easy-to-manage processes such as heat treatment or sedimentation. The purpose is to provide.

Additionally, the present invention aims to provide a positive electrode active material and secondary battery with excellent electrochemical performance, output performance, resistance characteristics, and capacity characteristics.

The above and other objects of the present invention can all be achieved by the present invention described below.

In order to achieve the above object, the present invention includes the steps of recovering the positive electrode active material by heat treating a waste positive electrode including a current collector and a positive electrode active material layer coated thereon under an oxygen atmosphere, and washing the recovered positive electrode active material with a cleaning solution. A method of regenerating a positive electrode active material that includes the step of filtering and separating into a solid content and a primary filtrate. Some of the recovered positive electrode active material is washed with the primary filtrate and then filtered to separate it into a solid content and a secondary filtrate. Provided is a method for regenerating a positive electrode active material including the step of:

II) In I), the method for regenerating the positive electrode active material may further include the step of washing some of the other recovered positive electrode active materials with the secondary filtrate and then filtering them to separate the solid content and the tertiary filtrate.

III) In I) to II), the method of regenerating the positive electrode active material may include mixing the respective solids obtained after washing with a washing liquid and a filtrate.

IV) In I) to III), the washing liquid may have a weight of 3 to 9 times the weight of the recovered positive electrode active material.

V) The washing liquid in I) to IV) may be at room temperature or at a temperature higher than room temperature.

VI) In I) to V), the washing liquid may be water, a basic lithium compound aqueous solution, or a salt aqueous solution.

VII) In I) to VI), the washing may include stirring the recovered positive electrode active material and the washing liquid or filtrate for 20 to 40 minutes.

VIII) In I) to VI), the solid content obtained after washing with the washing liquid and the filtrate may have an average fluorine (F) removal rate of 10% or more.

IX) In I) to VIII), the waste positive electrode is a positive electrode separated from a discarded lithium secondary battery after use, a defective positive electrode sheet generated in the lithium secondary battery manufacturing process, or positive electrode scrap remaining after punching out the positive plate from the positive electrode sheet. You can.

X) In I) to IX), the positive electrode active material is lithium cobalt oxide; lithium manganese oxide; iron phosphate compounds; Lithium Nickel Cobalt Aluminum Oxide; lithium nickel oxide; A nickel-manganese-based lithium composite metal oxide in which part of the nickel (Ni) in the lithium nickel oxide is replaced with manganese (Mn); and an NCM-based lithium composite transition metal oxide in which a portion of nickel (Ni) in the lithium nickel oxide is replaced with manganese (Mn) and cobalt (Co).

XI) In I) to X), the heat treatment may be performed at 300 to 650 ° C.

XII) In I) to XI), the method of regenerating the positive electrode active material may include drying the solid content.

XIII) In I) to

XIV) In I) to XIII), the lithium precursor may be one or more selected from the group consisting of LiOH, Li ₂ CO ₃ , LiNO ₃ and Li ₂ O.

XV) In I) to

XVI) In I) to XV), the annealing temperature may be a temperature exceeding the melting point of the lithium precursor.

XVII) In I) to

In addition,

Additionally, XIX) the present invention relates to lithium cobalt oxide; lithium manganese oxide; iron phosphate compounds; Lithium Nickel Cobalt Aluminum Oxide; lithium nickel oxide; A nickel-manganese-based lithium composite metal oxide in which part of the nickel (Ni) in the lithium nickel oxide is replaced with manganese (Mn); and at least one selected from the group consisting of NCM-based lithium composite transition metal oxides in which part of nickel (Ni) in the lithium nickel oxide is replaced with manganese (Mn) and cobalt (Co), and D50 is 2 in the particle size distribution chart. to 20 ㎛, D90 is 8 to 80 ㎛, D10 is 1 to 10 ㎛, and the surface residual LiOH and Li ₂ CO ₃ contents are each 0.5% by weight or less.

XX) In I) to XIX), the regenerated positive electrode active material has the following formula (1)

[Formula 1]

Li _a Ni _x Mn _y Co _z M _w O _{2 + δ}

(In Formula 1, M includes one or more selected from the group consisting of B, W, Al, Ti, and Mg, 1<a≤1.1, 0<x<0.95, 0<y<0.8, 0< It may be a compound expressed as z<1.0, 0≤w≤0.1, -0.02≤δ≤0.02, x+y+z+w=1.

XXI) In I) to XX), the regenerated positive electrode active material has a moisture content of 200 ppm or less and may include MgO or MgF ₂ .

XXII) In I) to XXI), the surface of the recycled positive electrode active material may be coated with a coating agent containing metal or carbon.

Additionally, XXIII) the present invention provides a secondary battery including the positive electrode active material of any one of I) to XXII) above.

According to the present invention, the F component remaining on the surface of the recycled positive electrode active material is washed in multiple stages with a small amount of washing liquid and its filtrate, thereby significantly reducing the generation of wastewater and greatly shortening the cleaning time, resulting in loss of Li and increase in fine particles in the functional coating layer and lattice. It is environmentally friendly because it does not use acid, and process costs are reduced because there is no need for neutralization and wastewater treatment. There are no discarded metal elements because the cathode active material is recycled without decomposition, and it is recovered because the current collector is not dissolved. It is possible to use organic solvents, so there is no risk of toxic gas generation or explosion, and a method of regenerating positive electrode active materials suitable for mass production using easy-to-manage processes such as heat treatment or sedimentation, and electrochemical performance, electrochemical performance, and It has the effect of providing a positive electrode active material with excellent resistance and capacity characteristics.

The following drawings attached to this specification illustrate embodiments of the present invention, and serve to further understand the technical idea of the present invention together with the detailed description described later. Therefore, the present invention is limited to the matters described in these drawings. It should not be interpreted.
Figure 1 is a diagram showing positive electrode scrap discarded after cutting the electrode plate from the positive electrode sheet.
Figure 2 is a flowchart of a regeneration process of a positive electrode active material in one embodiment according to the present invention.
Figure 3 is a schematic diagram of the washing step and annealing step of the recovered positive electrode active material in one embodiment according to the present invention.
Figure 4 shows the results of evaluating coin half-cells manufactured using the recycled positive electrode active material obtained in Example 1 and the recycled positive electrode active material obtained in the comparison group, respectively, showing 0.2C/0.2C and 0.5C/0.5C. This is a graph comparing the discharge capacity at 0.5/2C.
Figure 5 is a PSD (Particle Size Distribution) graph obtained by measuring the recycled positive electrode active material obtained in Example 1 using a particle size analyzer.
Figure 6 is a spectrum obtained by measuring the recycled positive electrode active material obtained in Example 1 using X-ray Photoelectron Spectroscopy (XPS).
Figure 7 is a spectrum obtained by measuring the recycled positive electrode active material obtained in Example 1 by ¹⁹ F-NMR.

The present inventors have proposed a method of directly recycling a waste cathode into a cathode active material without decomposing the cathode active material (direct recycling method), which significantly reduces the amount of washing water and cleaning time without deteriorating the electrochemical performance, resistance characteristics, and capacity characteristics of the recycled cathode active material. While researching a possible method, it was found that when a predetermined method includes the step of washing some of the recovered positive electrode active material with a predetermined filtrate, the F component remaining on the surface of the regenerated positive active material can be washed with a small amount of cleaning solution. By significantly reducing the generation of wastewater and at the same time greatly shortening the cleaning time, we have confirmed that the loss of Li in the functional coating layer and lattice and the increase in particulates have been minimized, improving the battery characteristics of the recycled positive electrode active material. Based on this, we have devoted ourselves to further research. This invention has been completed.

Hereinafter, the method for regenerating the positive electrode active material of the present invention and the positive active material recovered therefrom will be described in detail step by step.

However, terms or words used in this specification and claims cannot be construed as limited to their usual or dictionary meanings, and the inventor must appropriately define the concept of terms in order to explain his or her application in the best way. It must be interpreted with meaning and concept consistent with the technical idea of the present invention based on the principle that it can be done. Accordingly, the embodiments described in this specification and the configurations shown in the drawings are only one embodiment of the present invention and do not represent the entire technical idea of the present invention, so various equivalents and modifications that can replace them are provided. It should be understood that they can be arranged, replaced, combined, separated or designed into various different configurations.

All technical and scientific terms used in this description, unless otherwise defined, have the same meaning as commonly understood by those skilled in the art to which the present invention pertains.

Method for recycling positive electrode active material

The method for regenerating a positive electrode active material of the present invention includes the steps of a) heat treating a waste positive electrode including a current collector and a positive electrode active material layer coated thereon under an oxygen atmosphere to recover the positive electrode active material, and b) washing the recovered positive electrode active material with a cleaning solution. A method of regenerating a positive electrode active material comprising the step of filtering and separating into solid content and a primary filtrate, comprising the step of washing some of the recovered positive electrode active material with the primary filtrate and then filtering it to separate it into solid content and a secondary filtrate. In this case, some recycled positive electrode active materials are washed with a small amount of filtrate, which greatly reduces the generation of wastewater and at the same time greatly shortens the cleaning time, minimizing the loss of Li and the increase in fine particles within the functional coating layer and lattice. It is environmentally friendly and does not require neutralization and wastewater treatment, thus reducing process costs. The cathode active material is recycled without decomposition, so there are no discarded metal elements, and recovery is possible because the current collector is not dissolved. Organic solvents are not used. There is no risk of toxic gas generation or explosion, and it has the advantage of being suitable for mass production by using easy-to-manage processes such as heat treatment or sedimentation.

(a) Recovering the positive electrode active material from the waste positive electrode

The step (a) of recovering the positive electrode active material from the waste positive electrode according to the present invention preferably includes recovering the positive electrode active material by heat treating the waste positive electrode including the current collector and the positive electrode active material layer coated thereon in air at 300 to 650 ° C. It may be, and in this case, the process is simple and has the effect of cleanly removing the binder, conductive material, and current collector.

The waste positive electrode may preferably be a positive electrode separated from a discarded lithium secondary battery after use, a defective positive electrode sheet or positive electrode scrap generated during the lithium secondary battery manufacturing process, and more preferably a positive electrode remaining after punching out the positive plate from the positive electrode sheet. It could be scrap.

The positive electrode active material layer in step (a) may preferably include a positive electrode active material, a binder, and a conductive material.

The positive electrode active material is preferably lithium cobalt oxide such as LiCoO ₂ (hereinafter referred to as 'LCO'); Lithium manganese oxide such as LiMnO ₂ or LiMn ₂ O ₄ ; Lithium iron phosphate compounds such as LiFePO ₄ ; lithium nickel cobalt aluminum oxide (NCA); Lithium nickel oxide such as LiNiO ₂ ; A nickel-manganese-based lithium composite metal oxide in which part of the nickel (Ni) in the lithium nickel oxide is replaced with manganese (Mn); and an NCM-based lithium composite transition metal oxide in which a portion of nickel (Ni) in the lithium nickel oxide is replaced with manganese (Mn) and cobalt (Co), and more preferably, a nickel-manganese-based oxide. It is a lithium composite metal oxide, an NCM-based lithium composite transition metal oxide, or a mixture thereof, and in this case, it has excellent reversible capacity and thermal stability.

As another specific example, the positive electrode active material has the following formula 1:

[Formula 1]

Li _a Ni _x Mn _y Co _z M _w O _{2 + δ}

(In Formula 1, M includes one or more selected from the group consisting of B, W, Al, Ti, and Mg, 1<a≤1.1, 0<x<0.95, 0<y<0.8, 0< It may be a compound expressed as z<1.0, 0≤w≤0.1, -0.02≤δ≤0.02, x+y+z+w=1.

The conductive material may be, for example, a carbon-based conductive material, and preferably may be carbon black, CNT, or a mixture thereof.

The binder may be, for example, a polymer binder, preferably polyvinylidene fluoride (PVdF), acrylonitrile-butadiene rubber (NBR), or a mixture thereof, more preferably polyvinylidene. It may be fluoride.

The heat treatment temperature may be preferably 400 to 600°C, more preferably 500 to 600°C, and even more preferably 530 to 580°C. Within this range, the current collector does not melt and only the binder, etc. is removed from the current collector. There is an advantage that the positive electrode active material is easily separated.

The heat treatment time may be preferably 10 minutes to 5 hours, more preferably 30 minutes to 5 hours, even more preferably 30 minutes to 2 hours, even more preferably 30 minutes to 1 hour, and is within this range. There is an advantage that the positive electrode active material is easily separated from the current collector because only the binder, etc. is removed without melting.

In this description, the heat treatment time is the time treated at the relevant heat treatment temperature, and the time to reach the relevant heat treatment temperature is not calculated.

Figure 1 below shows positive electrode scrap discarded after cutting the positive electrode plate from the positive electrode sheet.

Referring to FIG. 1, a positive electrode sheet 30 is manufactured by coating a positive electrode active material layer 20 containing a positive electrode active material, a conductive material, a binder, etc. on aluminum foil 10, which is a long sheet-shaped positive electrode current collector, and then manufacturing the positive electrode sheet 30. The positive electrode plate 40 is produced by punching to size, and positive electrode scrap 50 is generated from the remaining portion. The punching is one means of cutting the positive electrode sheet.

In addition, the positive electrode active material layer 20 is formed by coating a slurry mixed with a positive active material, a conductive material, a binder, and a solvent on the aluminum foil 10. The slurry is very sensitive to the environment such as temperature, so it is difficult to set coating conditions. Since this is not difficult at all, waste anode sheets are generated until conditions for manufacturing the anode sheet 30 of the desired quality are found through a predetermined test.

For reference, in the following examples, positive electrode scrap was used as a waste positive electrode.

(b) washing the positive electrode active material

Step (b) of washing the positive electrode active material according to the present invention may preferably include washing some of the recovered positive electrode active material with the filtrate and then filtering it to separate it into solids and secondary filtrate. In this case, the recycled positive electrode is The F component remaining on the surface of the active material is completely removed with a small amount of washing liquid and its filtrate, which has the effect of greatly reducing wastewater generation and greatly improving the output performance of the battery. For reference, most of the F component remaining on the surface of the recycled positive electrode active material is combined with the Li element of the positive electrode active material and exists as LiF. LiF remaining on the surface can act as a surface protection layer and improve battery stability, but it has the problem of lowering electrical conductivity and causing overvoltage charging. Therefore, it is inevitable to go through a washing step to remove some or all of LiF. Since the solubility of LiF is very low at about 0.13 g per 100 g of distilled water, an excessive amount of distilled water was used in the past to completely elute it from the recycled positive electrode active material, so the same amount of waste liquid was used. There was a downside.

The step (b) of washing the positive electrode active material may further include washing some of the recovered positive electrode active material with the secondary filtrate and then filtering it to separate the solid content and the tertiary filtrate. In this case, By completely removing the F component remaining on the surface of the recycled positive electrode active material with a small amount of cleaning solution, the generation of wastewater is greatly reduced and the output performance of the battery is greatly improved.

The step (b) of washing the positive electrode active material may preferably include mixing the respective solids obtained after washing with the washing liquid and the filtrate. In this case, both reproducibility and battery output performance are excellent.

The filtrate can preferably be used 1 to 5 times, more preferably 1 to 3 times, and even more preferably 2 times. Within this range, it is economical, environmentally friendly, and battery-friendly. The output performance is all excellent. Here, when the filtrate is used once, the washing step can be referred to as a two-stage washing, and when the filtrate is used twice, the washing step can be referred to as a three-stage washing.

The washing liquid can preferably be used in a weight of 3 to 9 times the weight of the positive electrode active material to be cleaned, more preferably in a weight of 4 to 7 times, and even more preferably in a weight of 4 to 6 times. It can be used, and within this range, the F component remaining on the surface of the recycled positive electrode active material is completely removed with a small amount of washing liquid and its filtrate, which has the effect of greatly reducing the generation of wastewater and at the same time greatly improving the output performance of the battery. For reference, during heat treatment of a waste cathode, the F content flowing into the cathode active material is proportional to the amount of binder contained in the waste cathode. Although the residual amount may vary depending on the heat treatment conditions, approximately 50 to 90% of F is converted into the cathode active material. It appears to be flowing in. Most of the F introduced in this way exists in the form of LiF, and in order to completely remove it through the cleaning process, considering the theoretical solubility of LiF, it is calculated that about 10 times the weight of the positive electrode active material will require distilled water. However, in actual experiments, the common ion It is related to the rate of dissolution and solubility as well as the rate of mass transfer due to interference from other ions, so about 30 times more distilled water is required. However, the method for regenerating the cathode active material of the present invention cleanly removes the F component remaining on the surface with a small amount of washing liquid (e.g., distilled water), thereby greatly reducing the generation of waste water. In particular, the filtrate is used as is without purification, making it very economical and clean. Since the time is short, there is no disadvantage in output performance, etc.

The washing liquid may preferably be at room temperature or above room temperature, and as a specific example, it may be 20 to 100°C, and as another example, 20 to 60°C, 20 to 50°C, 20 to 45°C, 30 to 60°C, or 35°C. It can be from 60°C, and within this range, the F component remaining on the surface of the recycled positive electrode active material is completely removed with a small amount of washing liquid, which has the effect of greatly reducing the generation of wastewater and greatly improving the output performance of the battery.

In this description, room temperature is not particularly limited as long as it is a temperature commonly defined as room temperature in the technical field to which the present invention pertains, and may be, for example, a temperature within 20 to 25°C.

In the present disclosure, the temperature control method of the washing liquid is not particularly limited as long as it is a temperature control method commonly used in the technical field to which the present invention pertains. For example, the temperature of the washing liquid can be adjusted by using a jacket-type stirring tank or a double-jacket-type stirring tank. It can be easily adjusted.

The washing liquid may preferably be water, a basic aqueous lithium compound solution, or an aqueous salt solution, more preferably water or a basic aqueous lithium compound solution, even more preferably water, and even more preferably distilled water or deionized water. In this case, the F component remaining on the surface of the recycled positive electrode active material is completely removed with a small amount of cleaning solution, which has the effect of greatly reducing wastewater generation and greatly improving the output performance of the battery.

The basic lithium compound aqueous solution may preferably contain more than 0% by weight to 15% by weight or less of the basic lithium compound, and more preferably contains more than 0% by weight to 10% by weight or less of the basic lithium compound. Within this range, the surface modification effect is excellent in removing LiF, etc., formed on the surface of the positive electrode active material during the previous heat treatment process.

The step (b) of washing the positive electrode active material may preferably be a step of washing the recovered positive electrode active material by stirring it with the cleaning solution. In this case, foreign substances such as LiF generated on the surface of the positive electrode active material in the previous heat treatment process are removed. It has the effect of reforming the surface of the recycled positive electrode active material.

The washing preferably includes stirring for 20 minutes to 40 minutes, preferably includes stirring for 20 minutes to 35 minutes, 25 minutes to 40 minutes, and 25 minutes to 35 minutes, and within this range is applied to the surface of the positive electrode active material. All foreign substances such as LiF are removed, and the loss of Li in the functional coating layer and the lattice is small and the increase in fine particles is minimized, which has the advantage of excellent discharge capacity characteristics. For reference, since the positive electrode active material is vulnerable to moisture and CO ₂ , it is preferable that the cleaning step be as short as possible.

The solid content can preferably be dried before annealing, which has the effect of optimizing the lithium precursor addition process, that is, the annealing step.

The drying can be preferably carried out at 70 to 200 ℃, more preferably 20 to 130 ℃, until there is no further change in weight, for example, for 1 to 24 hours, and washing within this range It is effective in efficiently removing moisture contained in a positive electrode active material.

The solid content obtained after washing with the washing liquid and filtrate preferably has an average fluorine (F) removal rate of 10% or more, more preferably 12% or more, even more preferably 13% or more, and even more preferably 15%. It may be more than this, and within this range, all foreign substances such as LiF or metal fluoride generated on the surface of the positive electrode active material are removed, and yet, there is an advantage of excellent discharge capacity characteristics by reducing the loss of Li in the functional coating layer and the lattice and minimizing the increase in fine particles.

(c) After adding lithium precursor to the positive electrode active material Annealing step

The step (c) of adding a lithium precursor to the positive electrode active material and then annealing according to the present invention may preferably be a step of adding a lithium precursor to the washed positive electrode active material and annealing at 400 to 1000° C. in air. In this case, the decision It has the effect of improving the battery characteristics of the recycled positive electrode active material by improving crystallinity, such as increasing crystallinity or recovering crystal structure.

The lithium precursor in step (c) is preferably one or more selected from the group consisting of LiOH, Li ₂ CO ₃ , LiNO ₃ and Li ₂ O.

The lithium precursor in step (c) may be preferably added in a reduced amount, at least in the molar ratio of lithium in the positive electrode active material in step (a), based on the amount of lithium in the washed positive electrode active material. It can be added in an amount that provides a molar ratio of lithium of 0.0001 to 0.2 relative to the molar ratio of lithium in the positive electrode active material in step (a), and within this range, insufficient lithium in the recycled positive electrode active material is supplemented to increase crystallinity or crystal structure. There is an advantage that the battery characteristics of the recycled positive electrode active material are improved by improving crystallinity, such as recovery.

The lithium precursor in step (c) may be preferably added in an amount capable of providing 1 to 40 mol% of lithium based on the total 100 mol% of lithium in the positive electrode active material in step (a), More preferably, it can be added in an amount capable of providing lithium corresponding to 1 to 15 mol%, and more preferably in an amount capable of providing lithium corresponding to 7 to 11 mol%, within this range. It is very useful in improving battery characteristics as no residual precursors that can increase resistance are left in the recycled positive electrode active material.

The annealing temperature in step (c) can be adjusted within a limited range depending on the melting point of the lithium precursor. For example, in the case of Li ₂ CO ₃ , the melting point is 723 ° C, preferably 700 to 900 ° C, more preferably It can be annealed at 710 to 780 ℃, and in the case of LiOH, the melting point is 462 ℃, preferably 400 to 600 ℃, more preferably 450 to 480 ℃, and within this range, the crystal structure is recovered and the battery It has excellent output performance.

The annealing temperature in step (c) may preferably be a temperature that exceeds the melting point of the lithium precursor, but if it exceeds 1000°C, thermal decomposition of the positive electrode active material may occur, resulting in a decrease in battery performance.

(d) heat treatment after coating with a coating agent

The method for reusing a positive electrode active material of the present invention includes the step of (d) coating the surface of the cleaned positive electrode active material to obtain a reusable positive electrode active material, in which case the structural stability and electrochemical performance are improved while maintaining the properties of the positive electrode active material itself. It works.

The surface coating is preferably performed by coating the surface with a coating agent containing at least one of metal, organometallic, and carbon components in a solid or liquid manner and then heat treating it at 100 to 1200 ° C. In this case, the properties of the positive electrode active material itself are changed. It has the effect of improving structural stability and electrochemical performance while maintaining the same structure.

The coating agent containing the metal is preferably at least one selected from the group consisting of B, W, Al, Ti, Mg, Ni, Co, Mn, Si, Zr, Ge, Sn, Cr, Fe, V and Y. It is a coating agent containing, more preferably, a coating agent containing at least one selected from the group consisting of B, W, Al, Ti, and Mg, and even more preferably boron (B), tungsten (W), or a mixture thereof. It may be a coating agent containing, and more preferably, a coating agent containing tungsten (W) and boron (B), and a specific example is a coating agent containing tungsten boride (WB), in this case. There is an effect of improving resistance characteristics and life characteristics.

For example, the coating agent containing the metal may be an oxide or acid containing the metal as an element in the molecule.

The coating agent containing the organic metal is not particularly limited as long as it is commonly used in the technical field to which the present invention pertains and is a coating agent containing an organometallic compound containing the metal, and a specific example may be a metal alkoxide.

The coating agent containing the carbon component is not particularly limited as long as it is a coating agent containing the carbon component commonly used in the technical field to which the present invention pertains, and a specific example may be a saccharide such as sucrose.

For example, the coating agent may be included in an amount of 0.001 to 0.3 mol%, preferably 0.01 to 0.3 mol%, based on 1 mol% of metal in the positive electrode active material before coating treatment, based on the components coated on the surface of the actual positive electrode active material excluding the solvent. may be included, more preferably 0.01 to 0.15 mol%, more preferably 0.01 to 0.1 mol%, even more preferably 0.01 to 0.05 mol%, and within this range, the positive electrode active material itself It has the effect of improving structural stability and electrochemical performance while maintaining the same properties.

The heat treatment temperature may be preferably 100 to 1000 ℃, more preferably 200 to 1000 ℃, and even more preferably 200 to 500 ℃, and within this range, without performance degradation due to thermal decomposition of the positive electrode active material. It has the effect of improving structural stability and electrochemical performance.

The heat treatment time is preferably 1 to 16 hours, more preferably 3 to 7 hours, and within this range, structural stability and electrochemical performance are improved while maintaining the properties of the positive electrode active material itself. There is.

The coating method is not particularly limited as long as it is a coating method commonly used in the technical field to which the present invention pertains. For example, a liquid method of preparing a liquid coating and mixing it with a positive electrode active material, a mechanochemical method using high mechanical energy of ball milling, It may be a fluidized bed coating method, a spray drying method, a precipitation method in which the coating agent is precipitated onto the surface of the positive electrode active material in an aqueous solution, a method using the reaction between the gaseous coating agent and the positive electrode active material, or a sputtering method.

For example, the metal, organometallic, and carbon component may be spherical, plate-shaped, square-shaped, or needle-shaped, and these shapes can be adjusted by changing process conditions during the manufacturing process. The definition of each shape is defined in the technology to which the present invention pertains. There are no particular restrictions as long as it follows definitions commonly accepted in the field.

The coating agent preferably has an average diameter of 1 to 1000 nm and a specific surface area of 10 to 100 m2/g, and more preferably has an average diameter of 10 to 100 nm and a specific surface area of 20 to 100 m2/g. It can be uniformly attached to the surface of the positive electrode active material within this range, providing structural stability to the positive active material, thereby improving the problems of lifespan characteristics and electrochemical performance degradation due to lattice deformation or collapse of the crystal structure of the positive active material. there is.

In the present disclosure, the average diameter can be measured by a measurement method commonly used in the technical field to which the present invention pertains. For example, it can be measured using a laser diffraction method, and specifically, the particles of the positive electrode active material can be measured. After dispersing in a dispersion medium, it is introduced into a commercially available laser diffraction particle size measuring device such as Microtrac MT 3000, and irradiated with ultrasonic waves at about 28 kHz with an output of 60 W, and the average particle diameter (based on 50% of the particle diameter distribution in the measuring device) is measured. D50) can be calculated.

In this description, the specific surface area can be measured by a measurement method commonly used in the technical field to which the present invention pertains, for example, by the BET (Brunauer-Emmett-Teller) method, and specifically by BELSORP of BEL Japan. -mino II can be used to calculate the amount of nitrogen gas adsorption under liquid nitrogen temperature (77K).

Figure 2 below is a flowchart of a regeneration process of a positive electrode active material as an embodiment of the present invention, and Figure 3 below is a schematic diagram of a washing step and annealing step of a recovered positive electrode active material as an embodiment of the present invention. am.

Referring to Figures 2 and 3, first prepare positive electrode scrap (step S10). For example, a slurry prepared by mixing NCM-based or LCO-based lithium composite transition metal oxide, carbon black, and polyvinylidene fluoride with NMP (N-methyl pyrrolidone) was coated on aluminum foil and incubated at about 120°C. A positive electrode sheet is manufactured by drying in a vacuum oven. After punching out a positive electrode plate of a certain size, the remaining positive electrode scrap can be prepared.

The positive electrode scrap has a positive electrode active material layer on aluminum foil, and the positive electrode active material layer has a structure in which a binder binds the positive electrode active material and the conductive material after solvent volatilization. Therefore, when the binder is removed, the positive electrode active material is separated from the aluminum foil.

Next, the prepared positive electrode scrap is shredded to an appropriate size (step S20). Here, crushing includes cutting or shredding the positive electrode scrap into a size that is easy to handle. As a specific example, shredded positive electrode scrap may be 1 cm x 1 cm in size. For example, the crushing may use various dry crushing equipment such as a hand-mill, pin-mill, disk-mill, cutting-mill, and hammer-mill, or a high-speed cutter may be used to increase productivity.

The crushing can preferably be performed or the size of the pieces in consideration of the handling of the anode scrap and the characteristics required for the equipment used in the subsequent process. For example, if equipment capable of continuous processing is used, fluidity is It must be good, so the anode scrap must be shredded into smaller pieces.

Next, the anode scrap is heat treated in air (step S30). Here, heat treatment is performed to thermally decompose the binder in the active material layer.

Through the heat treatment in air as described above, the binder and conductive material in the active material layer are thermally decomposed into CO ₂ and H ₂ O and removed. Because the binder is removed, the positive electrode active material is separated from the current collector, and the separated positive active material is easily selected into powder form. Therefore, in step S30 alone, the active material layer can be separated from the current collector, and the positive electrode active material in the active material layer can be recovered in powder form.

It is important that the heat treatment is performed in air. When the heat treatment is performed in a reducing gas or inert gas atmosphere, the binder and the conductive material are carbonized rather than thermally decomposed. When carbonized, carbon components remain on the surface of the positive electrode active material, deteriorating the performance of the reused positive electrode active material. However, when heat treatment is performed in air, both the binder and the conductive material are removed because the carbon component in the binder and conductive material reacts with oxygen and disappears into gases such as CO and CO ₂ .

The heat treatment is preferably performed at 300 to 650 ℃, and as a specific example, at 550 ℃. Below 300 ℃, it is difficult to remove the binder, so the current collector cannot be separated, and above 650 ℃, the current collector melts and the current collector melts. A problem arises where the cannot be separated.

The heat treatment preferably has a temperature increase rate of 1 to 20 ℃/min, more preferably 3 to 10 ℃/min, a specific example is 5 ℃/min, but within this range, it is unreasonable for heat treatment equipment. It can be implemented without causing damage and has the advantage of not causing thermal shock to the anode scrap.

For example, the heat treatment may be performed for a period of time sufficient for the binder to be sufficiently thermally decomposed, preferably for 30 minutes or more, more preferably for 30 minutes to 5 hours, and a specific example is around 30 minutes. Within this range, the binder is sufficiently thermally decomposed and the thermal decomposition efficiency is excellent.

The heat treatment is performed using various types of furnaces, for example, a box-type furnace, and considering productivity, it is performed using a rotary kiln that allows continuous processing.

After the heat treatment, it can be slowly cooled or rapidly cooled in the air.

Next, the positive electrode active material recovered through heat treatment is washed with a cleaning solution (steps S40, S40', S40", and S40"').

The cleaning effectively removes foreign substances that may be generated on the surface of the positive electrode active material during the heat treatment step (S30) using a small amount of cleaning solution, so that no foreign substances remain on the surface of the recycled positive electrode active material.

As a specific example, the cleaning may be performed using a cleaning solution adjusted to room temperature to 40° C. In this case, there is an advantage in that the amount of cleaning solution is greatly reduced while foreign substances formed on the surface of the positive electrode active material are effectively removed.

It is also important to use neutral water, basic lithium compound aqueous solution, or salt aqueous solution as the cleaning solution. If sulfuric acid or hydrochloric acid aqueous solution is used, foreign substances such as fluorine (F) compounds on the surface of the positive electrode active material can be cleaned, but Excessive elution of existing transition metals such as Co and Mg deteriorates the performance of the recycled positive electrode active material.

However, the neutral water or basic lithium compound aqueous solution is safe and inexpensive, and not only removes trace amounts of binder that may remain after the thermal decomposition in step S30 without loss of other elements, but also removes the transition present in the positive electrode active material. It does not elute the metal, and in the case of a basic lithium compound aqueous solution, it can also play a role in replenishing the amount of lithium that can be eluted during the washing process.

For example, the basic lithium compound aqueous solution contains a basic lithium compound in an amount of more than 0% to 15% or less, and a lithium compound aqueous solution with a high concentration exceeding this has somewhat poor cleaning performance and leaves an excessive amount of lithium compound on the surface of the active material after cleaning. This can have a negative impact on the future annealing process.

As a specific example, the cleaning may use a cleaning solution with a weight of 4.5 to 5.5 times the weight of the positive electrode active material to be cleaned.

The lithium compound is preferably LiOH.

In this description, % means weight% unless otherwise defined.

For example, the washing is performed by mixing the recovered positive electrode active material and the washing liquid or filtrate by stirring. Here, stirring is not particularly limited, but may be mechanical stirring or ultrasonic stirring.

As a specific example, the washing is performed for 25 to 35 minutes, and within this range, it is effective in preventing a decrease in battery capacity due to excessive elution of lithium.

The reason for washing the positive electrode active material recovered in this substrate with neutral water or a basic lithium compound aqueous solution is to perform surface modification to remove LiF, etc., which may be present on the surface of the recovered positive active material. During the heat treatment of step S30, the binder and conductive material in the active material layer are vaporized and removed as CO ₂ and H ₂ O. During this process, CO ₂ and H ₂ O react with lithium on the surface of the positive electrode active material to form Li ₂ CO ₃ and LiOH. LiF or metal fluoride may be formed when F present in a binder such as PVdF reacts with lithium or other metal elements that make up the positive electrode active material. If such LiF or metal fluoride remains on the surface of the positive electrode active material, battery characteristics may deteriorate upon reuse.

After stirring or mixing the recovered positive electrode active material and neutral water or basic lithium compound aqueous solution, the positive electrode active material slurry formed therefrom is filtered to obtain a solid positive electrode active material and a primary filtrate.

It is preferable to dry the obtained solid positive electrode active material. As a specific example, it can be dried in the air at 100 to 120 ° C. using a vacuum oven (convection type).

Referring to FIG. 3, 250 g of distilled water was added as a washing liquid to 50 g of some positive electrode active material recovered in the heat treatment step (S30), stirred for 30 minutes, and then passed through a 2.5 ㎛ filter paper to remove solid content (#4) and primary Separate into filtrate (see step S40'). The entire amount of the primary filtrate is added to 50 g of the other positive electrode active material recovered in the heat treatment step (S30) and stirred for 30 minutes, then passed through a 2.5 ㎛ filter paper and separated into solid content (#5) and secondary filtrate (S40) (see step "). In addition, the entire amount of the secondary filtrate was added to 50 g of another positive electrode active material recovered in the heat treatment step (S30) and stirred for 30 minutes, and then passed through a 2.5 ㎛ filter paper to remove solid content (#6) and Separate into a third filtrate (see step S40"'). Here, the solids (#4, #5, and #6) are each dried using a vacuum oven, the filtrate is used a total of two times, and the third filtrate can be discharged and discarded. The solid contents (#4, #5, and #6) can be mixed before annealing (step S50'), and at this time, the average fluorine (F) removal rate thereof may preferably be 15% or more.

Next, a lithium precursor is added to the washed positive electrode active material and annealed (step S50).

Since lithium in the positive electrode active material is lost during steps S30 and S40, the lithium loss is compensated for in step S50. In addition, since a deformed structure (e.g., Co ₃ O ₄ in the case of LCO active material) may appear on the surface of the positive electrode active material during the previous step, the crystal structure of the positive electrode active material is recovered through annealing in step S50 to produce a recycled positive electrode active material. Improve the properties of or restore them to the level of new cathode active materials. Here, 'new' is the opposite of 'regeneration', meaning something that was created for the first time, and is the same as 'raw materials' used in the examples.

As a specific example, LiOH is used as the lithium precursor.

The lithium precursor is preferably added in an amount equal to the molar ratio of the lost lithium compared to the molar ratio of lithium and other metals in the new positive electrode active material used in the positive electrode active material layer. Addition of an excessive amount of lithium precursor compared to the amount of lithium lost leaves unreacted lithium precursor in the regenerated positive electrode active material, which serves to increase resistance, so it is necessary to add an appropriate amount of lithium precursor. For example, when the molar ratio of lithium and other metals in the new positive electrode active material is 1, a lithium precursor in an amount of lithium in a molar ratio of 0.001 to 0.4 can be added, preferably in an amount of lithium in an amount of 0.01 to 0.2 molar ratio. can be added.

As a specific example, based on the results of ICP analysis, adding a lithium precursor at a molar ratio of 0.09 to 0.1 (based on lithium metal), which is the ratio lost compared to the lithium content in the new cathode active material, shows a capacity improvement effect to the same level as that of the new cathode active material. Here, the ICP analysis result has an error value of approximately ±0.02.

For example, the annealing is performed in air under conditions of 400 to 1000° C., and is preferably performed under conditions of 600 to 900° C., and this temperature should vary within a limited range depending on the type of lithium precursor.

The annealing temperature is preferably higher than the melting point of the lithium precursor. However, at temperatures exceeding 1000°C, thermal decomposition of the positive electrode active material occurs and performance deteriorates, so the temperature should not exceed 1000°C. Accordingly, when Li ₂ CO ₃ is used as a lithium precursor, the annealing temperature may be appropriately 700 to 900°C, more preferably 710 to 780°C, and most preferably 750 to 780°C. In addition, when using LiOH as a lithium precursor, the annealing temperature may be suitably 400 to 600 °C, more suitably 450 to 480 °C, and most suitably 470 to 480 °C.

The annealing time is preferably 1 hour or more, preferably 15 hours or less, and more preferably 4 to 6 hours. If the annealing time is long, the crystal structure can be sufficiently recovered, but even if annealing for a long time, it does not have a significant effect on performance. At this time, the annealing equipment may be the same or similar to that used in heat treatment step S30.

The annealing step restores the battery characteristics of the recycled positive electrode active material by recovering the crystal structure, that is, improving crystallinity, while being safe and inexpensive.

The regenerated cathode active material obtained through the above cathode active material regeneration step has a particle size distribution similar to that of the new cathode active material, and no carbon component resulting from carbonization of the binder or conductive material remains on the surface, so it can be 100% intact or new without any additional processing. It can be used to manufacture positive electrodes by mixing with active materials.

Next, as an optional step, surface coating may be further performed on the annealed positive electrode active material (S60).

The surface coating is, for example, coating a surface with a coating containing metal or carbon in a solid or liquid form and then heat-treating it at 100 to 1200 ℃. If the heat treatment temperature is less than 100 ℃, the surface is protected by a different metal through surface coating. If a layer is not formed and the temperature exceeds 1200°C, battery performance deteriorates due to thermal decomposition of the positive electrode active material.

Specifically, when metal oxides such as B, W, and B-W are coated on a positive electrode active material and then heat treated, a lithium borooxide layer can be formed on the surface of the active material, which acts as a surface protection layer.

The solid-phase or liquid-phase method of the surface coating is specifically performed by methods such as mixing, milling, spray drying, or grinding.

For reference, in the preceding annealing step S50, when the molar ratio of lithium to other metals in the positive electrode active material is set to 1:1, the lithium in the positive electrode active material reacts with the coating agent, reducing the molar ratio of lithium to other metals in the positive electrode active material to less than 1:1. If this happens, the capacity of the battery cannot be achieved at 100%. Therefore, not only is the lithium that was lacking in the previous step S50 added to ensure that the lithium:other metal molar ratio in the positive electrode active material is 1:1, but an excess amount is added so that lithium is included in a molar ratio of 0.0001 to 0.1 more than the other metals in the positive electrode active material. will be. Then, during the surface coating in step S60, the molar ratio of lithium to other metals in the positive electrode active material becomes 1:1, further forming a surface protective layer.

Specifically, the lithium added in excess at a molar ratio of about 0.0001 to 0.1 in step S50 reacts with metal oxides such as B, W, and B-W in step S60, and the molar ratio of lithium to other metals in the positive electrode active material becomes 1:1, resulting in a decrease in battery capacity. I never do that.

Regenerated positive electrode active material

The regenerated positive electrode active material of the present invention is characterized in that it is manufactured by the above-described regeneration method of the positive electrode active material. In this case, the F component remaining on the surface of the regenerated positive active material is small, and the loss of Li and the increase in fine particles in the functional coating layer and lattice are minimized. This has the effect of greatly improving output performance (rate performance).

In addition, the recycled positive electrode active material of the present invention is preferably lithium cobalt oxide such as LiCoO ₂ (hereinafter referred to as 'LCO'); Lithium manganese oxide such as LiMnO ₂ or LiMn ₂ O ₄ ; Lithium iron phosphate compounds such as LiFePO ₄ ; lithium nickel cobalt aluminum oxide (NCA); Lithium nickel oxide such as LiNiO ₂ ; A nickel-manganese-based lithium composite metal oxide in which part of the nickel (Ni) in the lithium nickel oxide is replaced with manganese (Mn); and at least one selected from the group consisting of NCM-based lithium composite transition metal oxides in which part of nickel (Ni) in the lithium nickel oxide is replaced with manganese (Mn) and cobalt (Co), and D50 is 2 in the particle size distribution chart. to 20 ㎛, D90 is 8 to 80 ㎛, D10 is 1 to 10 ㎛, and the surface residual LiOH and Li 2 CO 3 contents are each 0.5% by weight or less, and in this case, the residual LiOH and Li ₂ CO ₃ contents on the surface of the recycled positive electrode active material are each 0.5% by weight or less. The F component is small, and the loss of Li and increase in fine particles within the functional coating layer and lattice are minimized, which has the effect of greatly improving the rate performance of the battery.

The recycled positive electrode active material preferably has the following formula (1)

[Formula 1]

Li _a Ni _x Mn _y Co _z M _w O _{2 + δ}

(In Formula 1, M includes one or more selected from the group consisting of B, W, Al, Ti, and Mg, 1<a≤1.1, 0<x<0.95, 0<y<0.8, 0< It may be a compound expressed as z<1.0, 0≤w≤0.1, -0.02≤δ≤0.02, x+y+z+w=1.

The recycled positive electrode active material preferably has a D50 of 5 to 20 ㎛, a D90 of 15 to 80 ㎛, and a D10 of 2 to 10 ㎛, more preferably, a D50 of 10 to 20 ㎛ in the particle size distribution, D90 is 20 to 80 ㎛, D10 is 3 to 10 ㎛, more preferably, in the particle size distribution chart, D50 is 15 to 20 ㎛, D90 is 30 to 80 ㎛, and D10 is 4 to 10 ㎛, within this range. There is less F component remaining on the surface of the recycled positive electrode active material, and the loss of Li and increase in fine particles within the functional coating layer and lattice are minimized, resulting in a significant improvement in battery output performance.

The regenerated positive electrode active material preferably has D5 in the particle size distribution diagram of 1 to 10 ㎛, more preferably 2 to 9 ㎛, even more preferably 3 to 8 ㎛, and even more preferably 4 to 7 ㎛, Within this range, the F component remaining on the surface of the recycled positive electrode active material is small, and the loss of Li and the increase in fine particles in the functional coating layer and lattice are minimized, which has the effect of greatly improving the output performance of the battery.

As a specific example, the lithium cobalt oxide preferably has D50 of 16 to 20 ㎛, D90 of 25 to 50 ㎛, D10 of 2 to 10 ㎛, and more preferably D50 of 16 to 19 in the particle size distribution. ㎛, D90 is 25 to 40 ㎛, D10 is 3 to 10 ㎛, more preferably, in the particle size distribution chart, D50 is 16 to 18 ㎛, D90 is 25 to 35 ㎛, and D10 is 4 to 10 ㎛, More preferably, in the particle size distribution, D50 is 16 to 17 ㎛, D90 is 25 to 30 ㎛, and D10 is 5 to 10 ㎛, and within this range, the F component remaining on the surface of the recycled positive electrode active material is small, The loss of Li and the increase in fine particles within the functional coating layer and the lattice are minimized, thereby significantly improving the rate performance of the battery.

In this description, the average diameter (D5, D10, D50 and D90, etc.) is not particularly limited when measured by a measurement method commonly used in the technical field to which the present invention pertains, for example, using a laser diffraction method. Specifically, the particles of the positive electrode active material are dispersed in a dispersion medium, then introduced into a commercially available laser diffraction particle size measuring device such as Microtrac MT 3000, irradiated with an ultrasonic wave of about 28 kHz with an output of 60 W, and the measurement device The average particle diameter can be calculated based on 5%, 10%, 50%, and 90% of the particle diameter distribution.

The recycled positive electrode active material preferably has a surface residual LiOH and Li ₂ CO ₃ content of 0.3 wt% or less, more preferably 0.1 wt% or less, and even more preferably 0.02 wt% or less and 0.07 wt% or less, respectively. and even more preferably 0.01% by weight or less and 0.05% by weight or less, very preferably 0.008% by weight or less and 0.03% by weight or less, respectively, and most preferably 0.006% by weight or less and 0.03% by weight or less, respectively, Within this range, the F component remaining on the surface of the recycled positive electrode active material is small, and the loss of Li and the increase in fine particles in the functional coating layer and lattice are minimized, which has the effect of greatly improving the output performance of the battery.

In this substrate, the surface residual LiOH and Li ₂ CO ₃ contents are not particularly limited by measurement methods commonly used in the technical field to which the present invention pertains, and can be measured by, for example, titration.

The recycled positive electrode active material preferably has a moisture content of 100 ppm or less, more preferably 50 ppm or less, and even more preferably 30 ppm or less, and within this range, the stability and output performance of the recycled positive electrode active material are excellent. there is.

In this description, the moisture content is not particularly limited as long as it is used by a method or device for measuring moisture content commonly used in the technical field to which the present invention pertains. For example, moisture measuring equipment may be used, and a specific example is a Karl Fischer moisture meter. Available.

The surface of the recycled positive electrode active material may preferably be coated with a coating containing metal or carbon. In this case, the structural stability of the positive electrode active material is improved without chemical or physical changes in the positive electrode active material itself, such as output performance, life characteristics, capacity, etc. The electrochemical properties of the cathode active material are improved, and the physicochemical properties are also improved due to the effect of reducing the amount of residual lithium and decreasing the pH by substitution of heterogeneous elements on the surface of the positive electrode active material.

The recycled positive electrode active material preferably has a fluorine (F) content of 600 ppm or less, more preferably 200 ppm or less, even more preferably 100 ppm or less, even more preferably 50 ppm or less, and most preferably 30 ppm or less. It can be ppm or less, and within this range, excellent resistance characteristics and capacitance characteristics are achieved.

The recycled positive electrode active material of the present invention may include all of the contents of the above-described positive electrode active material recycling method. Therefore, redundant description thereof is omitted here.

secondary battery

The secondary battery of the present invention includes the above positive electrode active material, and in this case, the F component remaining on the surface of the regenerated positive active material is small, and the loss of Li and increase in fine particles in the functional coating layer and lattice are minimized to improve initial discharge capacity, output performance, and It has excellent capacity and resistance characteristics, and is environmentally friendly as it does not use acids and organic solvents in the recovery and regeneration process of the positive electrode active material. In particular, it has excellent economic efficiency and productivity by using the filtrate as is without purification.

The secondary battery of the present invention may include all of the above-described positive electrode active material and its regeneration method. Therefore, redundant description thereof is omitted here.

Hereinafter, preferred embodiments are presented to aid understanding of the present invention. However, the following examples are merely illustrative of the present invention, and it is clear to those skilled in the art that various changes and modifications are possible within the scope and spirit of the present invention. It is natural that such variations and modifications fall within the scope of the attached patent claims.

[Example]

Example One

After punching the positive plate, the discarded positive electrode scrap (current collector: aluminum foil, positive electrode active material: LCO-based lithium composite transition metal oxide) is shredded, heat treated in air at 550°C for 30 minutes to remove the binder and conductive material, and the current collector and positive electrode are removed. After separating the active material, the positive electrode active material was recovered. Here, the temperature increase rate until reaching the heat treatment temperature was 5 °C/min, and the F content in the recovered positive electrode active material was 4240 ppm.

150 g of the recovered positive electrode active material (hereinafter referred to as 'LCO powder') was prepared by dividing into 50 g portions (#1 50g, #2 50g, #3 50g).

#1 50 g of LCO powder and 250 g of distilled water were mixed and stirred at 400 rpm for 30 minutes. After the stirring, reduced pressure filtration was performed using filter paper with a pore size of 2.5 ㎛ to separate solids (residue) and primary filtrate (filtrate). The solid content (#4) remaining on the filter paper was dried in a vacuum oven at 100°C for 6 hours. The entire amount of the primary filtrate was recovered, mixed with 50 g of #2 LCO powder, stirred and filtered under the same conditions as for #1 LCO powder, and the solid content (#5) remaining on the filter paper was placed in a vacuum oven at 100°C for 6 hours. It was dried. Then, the entire amount of the secondary filtrate was recovered, mixed again with 50 g of #3 LCO powder, stirred and filtered under the same conditions, and the solid content (#6) remaining on the filter paper was dried in a vacuum oven at 100°C for 6 hours. And the entire third filtrate was discarded.

The three types of previously dried LCO powders (#4, #5, and #6) were aliquoted at 10 g each and mixed evenly, and Li corresponding to 3 mol% of the mole number of the raw material LCO-based lithium complex transition metal oxide was converted to Li ₂ CO ₃ In addition, the solid phase was mixed using a mixer. Afterwards, the solid-phase mixed LCO powder was placed in an alumina crucible and annealed under conditions of 750°C and 5 hours to prepare LCO powder for final evaluation. Here, the molar ratio of lithium and other metals in the positive electrode active material was measured through ICP analysis.

Example 2

A recycled positive electrode active material was prepared in the same manner as in Example 1, except that the temperature of distilled water and filtrate was changed from room temperature to 40°C.

Example 3

A recycled positive electrode active material was prepared in the same manner as in Example 1, except that 300 g of distilled water was used in Example 1.

Example 4

A recycled positive electrode active material was prepared in the same manner as in Example 1, except that stirring was performed for 60 minutes.

Comparative example One

A regenerated positive electrode was produced in the same manner as in Example 1, except that 150 g of LCO powder was mixed, stirred, and filtered at once with 250 g of distilled water without aliquoting, and the filtrate was discarded without reuse. The active material was prepared.

Comparative example 2

A recycled positive electrode active material was manufactured in the same manner as Comparative Example 1, except that the stirring time was changed from 30 minutes to 60 minutes.

Comparative example 3

A regenerated positive electrode was produced in the same manner as in Example 1, except that 150 g of LCO powder was mixed, stirred, and filtered at once with 600 g of distilled water instead of aliquoting, and the filtrate was discarded without being reused. The active material was prepared.

Comparative example 4

In the same manner as in Example 2, except that 150 g of LCO powder was mixed, stirred, and filtered at once with 250 g of distilled water at 40°C without aliquoting, and the filtrate was discarded without reuse. A recycled positive electrode active material was manufactured.

Control example

A recycled positive electrode active material was prepared in the same manner as in Example 1, except that only 50 g of LCO powder was mixed with 250 g of distilled water, stirred, and filtered, and the filtrate was discarded rather than reused.

[Test example]

The properties of the recycled positive electrode active materials obtained in Examples 1 to 4, Comparative Examples 1 to 4, and Control Examples were measured by the following method, and the results are shown in Table 1 and Figures 4 to 7 below.

* ICP analysis: Using an ICP analysis device, the remaining amount of LiF, the ratio of lithium to other metals in the active material, and the content of specific elements such as F (mg/kg) were measured. At this time, it can be measured with a general ICP analysis device widely used in laboratories, but there is no deviation depending on the measurement device or method.

* Coin half-cell C-rate evaluation: 96% by weight of recycled positive electrode active material, 2% by weight of conductive material, and 2% by weight of binder were weighed and mixed with an organic solvent to create a slurry. This was coated on aluminum foil to manufacture a positive electrode, and then a cell (Coin Half Cell, CHC) was manufactured and evaluated under the conditions of a voltage of 3 to 4.55V and 25°C.

division LCO powder washing liquid Washing conditions F content in LOC powder before washing (ppm) F content in LCO powder after washing (ppm) F removal amount (ppm) F removal rate (%) F removal rate average (%) Example 1 #1 50g 250g distilled water Room temperature/30 minutes stirring 4210 3315 895 21.3% 15.13 #2 50g primary filtrate Room temperature/30 minutes stirring 4210 3565 645 15.3% #3 50g secondary filtrate Room temperature/30 minutes stirring 4210 3840 370 8.8% Example 2 #1 50g 250g distilled water Stirring at 40℃/30 minutes 4210 2870 1340 31.8% 23.26 #2 50g primary filtrate Stirring at 40℃/30 minutes 4210 3200 1010 24.0% #3 50g secondary filtrate Stirring at 40℃/30 minutes 4210 3620 590 14.0% Example 3 #1 50g 300g distilled water Room temperature/30 minutes stirring 4210 2650 1560 37.10% 32.3 #2 50g primary filtrate Room temperature/30 minutes stirring 4210 2840 1370 32.50% #3 50g secondary filtrate Room temperature/30 minutes stirring 4210 3060 1150 27.30% Example 4 #1 50g 250g distilled water Room temperature/60 minutes stirring 4210 3300 910 21.60% 15.73 #2 50g primary filtrate Room temperature/60 minutes stirring 4210 3525 685 16.30% #3 50g secondary filtrate Room temperature/60 minutes stirring 4210 3820 390 9.30% Comparative Example 1 #1 150g 250g distilled water Room temperature/30 minutes stirring 4210 3870 340 8.1% 8.1% Comparative Example 2 #1 150g 250g distilled water Room temperature/60 minutes stirring 4210 3790 420 10.00% 10.00% Comparative Example 3 #1 150g 600g distilled water Room temperature/30 minutes stirring 4210 3560 650 15.4% 15.4% Comparative Example 4 #1 150g 250g distilled water Stirring at 40℃/30 minutes 4210 3570 640 15.2% 15.2% Control example #1 50g 250g distilled water Room temperature/30 minutes stirring 4210 3315 895 21.3% 21.3%

As shown in Table 1, the regeneration method of the regenerated positive electrode active material according to the present invention (Examples 1 to 4) effectively removes the F component remaining on the surface of the regenerated positive electrode active material with a small amount of distilled water and its filtrate, thereby reducing the generation of wastewater. It was confirmed that the loss of Li and the increase in fine particles within the functional coating layer and lattice were minimized by significantly shortening the cleaning time.

However, unlike the method for regenerating the recycled positive electrode active material according to the present invention, in Comparative Examples 1 to 4 in which no filtrate is used, when the same amount of distilled water as in Examples 1 to 4 is used (Comparative Example 1), the F removal rate is significantly lower. It was low, and even when the stirring time was increased (Comparative Example 2), the amount of distilled water was increased by 2.5 times (Comparative Example 3), or the washing temperature was increased (Comparative Example 4), the value was equal to or lower than the F removal rate of Examples 1 to 4. I was able to confirm that I had it.

Figure 4 below shows the results of evaluating the coin half-cell manufactured using the recycled positive electrode active material obtained in Example 1 and the recycled positive electrode active material obtained in the comparison group, respectively, showing 0.2C/0.2C, 0.5C/0.5. This is a graph comparing the discharge capacity at C and 0.5/2C.

Referring to Figure 4, Example 1 used only 250 g of distilled water to wash 150 g of LCO powder, while the control example used 250 g of distilled water to wash 50 g of LCO powder, using three times more distilled water than Example 1. Even though it was used extensively, the difference in residual F content between Example 1 and the control example was not large, and as a result of coin half-cell C-rate evaluation, it was confirmed that the discharge capacities of Example 1 and the control example were at a similar level.

Figure 5 below is a PSD (Particle Size Distribution) graph obtained by measuring the recycled positive electrode active material obtained in Example 1 using a particle size analyzer.

Referring to FIG. 5, it can be seen that the recycled positive electrode active material obtained in Example 1 has few fine particles, D50 is 1 to 20, Dmax (D90) is 80 or less, and Dmin (D5) is 1 or more, so the particle size is uniform. It was expected that the initial discharge capacity, output performance, capacity characteristics, and resistance characteristics were excellent.

Figure 6 below ^shows a spectrum obtained by measuring the regenerated positive electrode active material obtained in Example 1 using -This is a spectrum obtained by measuring with NMR.

Referring to Figures 6 and 7, in the XPS spectrum, the Mg peak is observed around the binding energy of 50 to 51, and MgO (6.6%) and MgF ₂ (12.4%) with atomic % in the range of 3 to 20%. The peak could be confirmed, and through the comparison of the 19F-NMR spectra before and after the washing step of Example 1, it was confirmed that the MgF ₂ peak did not change significantly after washing with distilled water, but the LiF peak decreased significantly.

10: Current collector
20: Active material layer
30: anode sheet
40: positive plate
50: Anode scrap

Claims (23)

A waste positive electrode including a current collector and a positive electrode active material layer coated thereon is heat treated under an oxygen atmosphere to recover the positive electrode active material, and the recovered positive electrode active material is washed with a washing solution and then filtered to separate it into solids and primary filtrate. As a method of regenerating a positive electrode active material,
Characterized in that it includes the step of washing some of the recovered positive electrode active material with the primary filtrate and then filtering it to separate it into solids and secondary filtrate.
Method for recycling positive electrode active material. According to paragraph 1,
The method of regenerating the positive electrode active material further includes the step of washing some of the other recovered positive electrode active materials with the secondary filtrate and then filtering them to separate the solid content and the tertiary filtrate.
Method for recycling positive electrode active material. According to claim 1 or 2,
The method of regenerating the positive electrode active material includes the step of mixing the respective solids obtained after washing with a washing liquid and a filtrate.
Method for recycling positive electrode active material. According to claim 1 or 2,
The washing liquid is characterized in that the weight is 3 to 9 times the weight of the recovered positive electrode active material.
Method for recycling positive electrode active material. According to claim 1 or 2,
The cleaning solution is characterized in that it is at room temperature or at a temperature higher than room temperature.
Method for recycling positive electrode active material. According to claim 1 or 2,
The cleaning solution is water, a basic lithium compound aqueous solution, or a salt aqueous solution.
Method for recycling positive electrode active material. According to claim 1 or 2,
The cleaning includes stirring the recovered positive electrode active material and the cleaning solution for 20 to 40 minutes.
Method for recycling positive electrode active material. According to claim 1 or 2,
The solid content obtained after washing with the washing liquid and filtrate is characterized in that the average fluorine (F) removal rate is 10% or more.
Method for recycling positive electrode active material. According to claim 1 or 2,
The waste positive electrode is a positive electrode separated from a discarded lithium secondary battery after use, a defective positive electrode sheet generated in the lithium secondary battery manufacturing process, or positive electrode scrap remaining after punching out the positive plate from the positive electrode sheet.
Method for recycling positive electrode active material. According to claim 1 or 2,
The positive electrode active material is lithium cobalt oxide; lithium manganese oxide; iron phosphate compounds; Lithium Nickel Cobalt Aluminum Oxide; lithium nickel oxide; A nickel-manganese-based lithium composite metal oxide in which part of the nickel (Ni) in the lithium nickel oxide is replaced with manganese (Mn); And at least one selected from the group consisting of NCM-based lithium composite transition metal oxides in which a portion of nickel (Ni) in the lithium nickel oxide is replaced with manganese (Mn) and cobalt (Co).
Method for recycling positive electrode active material. According to claim 1 or 2,
The heat treatment is characterized in that performed at 300 to 650 ° C.
Method for recycling positive electrode active material. According to claim 1 or 2,
The method of regenerating the positive electrode active material includes the step of drying the solid content.
Method for recycling positive electrode active material. According to claim 1 or 2,
Characterized by adding a lithium precursor to the solid content and annealing at 400 to 1000 ° C in air.
Method for recycling positive electrode active material. According to clause 13,
The lithium precursor is characterized in that at least one selected from the group consisting of LiOH, Li ₂ CO ₃ , LiNO ₃ and Li ₂ O.
Method for recycling positive electrode active material. According to clause 13,
The lithium precursor is added at least in an amount reduced by the molar ratio of lithium in the positive electrode active material of the positive electrode active material layer.
Method for recycling positive electrode active material. According to clause 13,
The annealing temperature is characterized in that it exceeds the melting point of the lithium precursor.
Method for recycling positive electrode active material. According to clause 13,
The method of regenerating the positive electrode active material includes coating the annealed positive electrode active material with a coating agent containing metal or carbon and then heat treating it at 100 to 1200 ° C.
Method for recycling positive electrode active material. Characterized in that it is manufactured by the method of recycling the positive electrode active material according to claim 1 or 2.
Regenerated positive electrode active material. lithium cobalt oxide; lithium manganese oxide; iron phosphate compounds; Lithium Nickel Cobalt Aluminum Oxide; lithium nickel oxide; A nickel-manganese-based lithium composite metal oxide in which part of the nickel (Ni) in the lithium nickel oxide is replaced with manganese (Mn); and at least one selected from the group consisting of NCM-based lithium composite transition metal oxides in which part of nickel (Ni) in the lithium nickel oxide is replaced with manganese (Mn) and cobalt (Co), and D50 is 2 in the particle size distribution chart. to 20 ㎛, D90 is 8 to 80 ㎛, D10 is 1 to 10 ㎛, and the surface residual LiOH and Li ₂ CO ₃ contents are each 0.5% by weight or less.
Regenerated positive electrode active material. According to clause 19,
The recycled positive electrode active material has the following formula 1:
[Formula 1]
Li _a Ni _x Mn _y Co _z M _w O _{2 + δ}
(In Formula 1, M includes one or more selected from the group consisting of B, W, Al, Ti and Mg, 1<a≤1.1, 0<x<0.95, 0<y<0.8, 0< characterized in that it is a compound expressed as z<1.0, 0≤w≤0.1, -0.02≤δ≤0.02, x+y+z+w=1.
Regenerated positive electrode active material. According to clause 19,
The recycled positive electrode active material has a moisture content of 200 ppm or less and contains MgO or MgF ₂ .
Regenerated positive electrode active material. According to clause 19,
The recycled positive electrode active material is characterized in that the surface is coated with a coating containing metal or carbon.
Regenerated positive electrode active material. Characterized by comprising the positive electrode active material of any one of claims 19 to 22.
Secondary battery.