Positive electrode active material for lithium secondary batteries using waste positive electrode active material and method for manufacturing the same

Abstract

The present invention relates to a method for producing a positive electrode active material for a lithium secondary battery using a waste positive electrode active material, and more specifically, to a method for producing a positive electrode active material for a lithium secondary battery using a waste positive electrode active material, which can improve the electrochemical properties and stability by controlling the specific surface area of ​​the positive electrode active material.

Description

[Technical Field]

[0001] This invention relates to a positive electrode active material for lithium secondary batteries using waste positive electrode active material and a method for producing the same, and more specifically, to a positive electrode active material for lithium secondary batteries using waste positive electrode active material that can improve electrochemical properties and stability by controlling the specific surface area of ​​the waste positive electrode active material and a method for producing the same. [Background technology]

[0002] A battery stores electricity by using electrochemically reactive materials at its positive and negative electrodes. A typical example of such a battery is the lithium-ion secondary battery, which stores electrical energy through the difference in chemical potential that occurs when lithium ions are intercalated / deintercalated at the positive and negative electrodes.

[0003] The lithium secondary battery described above is manufactured by using materials capable of reversible intercalation / deintercalation of lithium ions as the positive electrode active material and the negative electrode active material, and by filling the space between the positive electrode and the negative electrode with an organic electrolyte or a polymer electrolyte.

[0004] Lithium composite oxides are used as positive electrode active materials in lithium secondary batteries. Examples of such composite oxides that have been studied include LiCoO2, LiMn2O4, LiNiO2, and LiMnO2. Recently, oxides in which some of the nickel in the lithium composite oxide is replaced with metals such as Co, Mn, and / or Al have been proposed. In particular, ternary lithium composite oxides containing Ni, Co, and Mn or Ni, Co, and Al are mainly used in large-capacity lithium secondary batteries for electric vehicles. Furthermore, there are attempts to improve the electrochemical properties and stability of the positive electrode active material by doping the aforementioned ternary lithium composite oxide with additional elements.

[0005] As technology advances, the demand for lithium-ion batteries, particularly for electric vehicles, is rapidly increasing. Consequently, related industries are also facing a growing demand for cost reductions in lithium-ion batteries and the various materials used in them.

[0006] For example, conventional methods for synthesizing lithium complex oxide precursors containing three or more elements generally use the coprecipitation method. However, the coprecipitation method generates large amounts of wastewater and, due to its complex process steps, is cited as a cause of environmental pollution as well as an increase in the manufacturing cost of cathode active materials.

[0007] As a result, research is currently being conducted to reduce the manufacturing cost of cathode active materials by recycling waste cathode active materials recovered from lithium secondary batteries that have reached the end of their service life. [Overview of the project] [Problems that the invention aims to solve]

[0008] In the lithium-ion battery market, while the growth of lithium-ion batteries for electric vehicles is driving the market, the demand for positive electrode active materials used in lithium-ion batteries is also continuously changing, and in particular, the demand for cost reduction of positive electrode active materials is steadily increasing.

[0009] To meet such market demands, the present invention aims to provide a method for producing a positive electrode active material for lithium secondary batteries using a precursor derived from waste positive electrode active material during the production of the positive electrode active material.

[0010] In particular, the present invention aims to provide a method for producing a positive electrode active material for lithium secondary batteries that, despite using a precursor derived from waste positive electrode active material, exhibits electrochemical properties and stability at a similar level to positive electrode active materials produced using precursors synthesized by conventional coprecipitation methods.

[0011] Thus, the present invention aims to provide a method for manufacturing positive electrode active material for lithium secondary batteries, which can contribute to reducing the cost of positive electrode active material and, consequently, lithium secondary batteries, by separating positive electrode active material from waste lithium secondary batteries that have reached the end of their lifespan or from defective lithium secondary batteries generated during the manufacturing process, and utilizing this as a raw material for manufacturing new positive electrode active material.

[0012] Furthermore, the present invention aims to provide a positive electrode containing a positive electrode active material manufactured by the manufacturing method defined in this application.

[0013] Furthermore, the present invention aims to provide a lithium secondary battery that uses the positive electrode defined in this application. [Means for solving the problem]

[0014] According to one aspect of the present invention, a method for producing a positive electrode active material for a lithium secondary battery using a waste positive electrode active material is provided, comprising the steps of (a) mixing a waste positive electrode active material with a solvent to produce a slurry, (b) pulverizing the waste positive electrode active material in the slurry, (c) spray-drying the slurry containing the pulverized waste positive electrode active material to produce a precursor, and (d) heat-treating the precursor to obtain a lithium composite oxide.

[0015] The waste positive electrode active material used in step (a) may include a lithium composite oxide represented by the following chemical formula 1 or chemical formula 2.

[0016] [Chemical formula 1] Li w Ni 1-x M x O 2-y X y (Here, M is at least one selected from Mn, Co, Al, B, Ba, Ce, Hf, Ta, Cr, Mg, V, Ti, Fe, Zr, Zn, Si, Y, Nb, Ga, Sn, Mo, W, Sr, Ge, Nd, Gd, and Cu. X is selected from F, S, and P, 0.5 ≤ w ≤ 1.5, 0 ≤ x ≤ 0.80, 0 ≤ y ≤ 2.)

[0017] [Chemical formula 2] Li w Ni 1-(x+y+z) Co x M1 y M2 z O2 (where M1 is at least one selected from Mn and Al, M2 is at least one selected from Mn, B, Ba, Ce, Hf, Ta, Cr, F, Mg, Al, V, Ti, Fe, Zr, Zn, Si, Y, Nb, Ga, Sn, Mo, W, P, Sr, Ge, Nd, Gd, and Cu, M1 and M2 are different elements from each other, 0.5 ≤ w ≤ 1.5, 0 ≤ x ≤ 0.40, 0 < y ≤ 0.40, 0 ≤ z ≤ 0.40.)

[0018] Further, the manufacturing method according to the present invention may further include a step (e) of heat-treating a mixture after manufacturing the mixture by mixing at least one selected from at least one sub-feedstock material containing an element selected from Mn, Co, Al, B, Ba, Ce, Hf, Ta, Cr, F, Mg, V, Ti, Fe, Zr, Zn, Si, Y, Nb, Ga, Sn, Mo, W, P, Sr, Ge, Nd, Gd, and Cu and a lithium-containing feedstock material with the lithium composite oxide obtained in the step (d).

[0019] Through the heat treatment in the step (e), an oxide represented by the following chemical formula 3 may be formed on at least a part of the surface of the lithium composite oxide.

[0020] [Chemical formula 3] Li a A b O c (where A is at least one selected from Ni, Mn, Co, Fe, Cu, Nb, Mo, Ti, Al, Cr, Zr, Zn, Na, K, Ca, Mg, Pt, Au, B, P, Eu, Sm, Ce, V, Ba, Ta, Sn, Hf, Gd, and Nd. 0 ≤ a ≤ 10, 0 <b≦8、2≦c≦13である。)

[0021] According to another aspect of the present invention, there is a positive electrode active material for a lithium secondary battery having a lithium composite oxide comprising at least (1) one selected from manganese and aluminum; (2) nickel; and (3) cobalt, wherein 3 wt% or more of the lithium composite oxide (1) one selected from manganese and aluminum; (2) nickel; and (3) cobalt is derived from waste positive electrode active material.

[0022] The positive electrode active material may be a positive electrode active material produced by a manufacturing method according to one aspect of the present invention.

[0023] The lithium composite oxide can be represented by the following chemical formula 1 or chemical formula 2.

[0024] [Chemical formula 1] Li w Ni 1-x M x O 2-y X y (Here, M is at least one selected from Mn, Co, Al, B, Ba, Ce, Hf, Ta, Cr, Mg, V, Ti, Fe, Zr, Zn, Si, Y, Nb, Ga, Sn, Mo, W, Sr, Ge, Nd, Gd, and Cu. X is selected from F, S, and P. (0.5 ≤ w ≤ 1.5, 0 ≤ x ≤ 0.80, 0 ≤ y ≤ 2.)

[0025] [Chemical formula 2] Li w Ni 1-(x+y+z) Co x M1 y M2z O2 (Here, M1 is at least one selected from Mn and Al. M2 is at least one selected from Mn, B, Ba, Ce, Hf, Ta, Cr, F, Mg, Al, V, Ti, Fe, Zr, Zn, Si, Y, Nb, Ga, Sn, Mo, W, P, Sr, Ge, Nd, Gd, and Cu. M1 and M2 are different elements. 0.5 ≤ w ≤ 1.5, 0 ≤ x ≤ 0.40, 0 <y≦0.40、0≦z≦0.40である。)

[0026] Furthermore, a coating layer containing an oxide represented by the following chemical formula 3 may be present on at least a portion of the surface of the lithium composite oxide.

[0027] [Chemical formula 3] Li a A b O c (Here, A is at least one selected from Ni, Mn, Co, Fe, Cu, Nb, Mo, Ti, Al, Cr, Zr, Zn, Na, K, Ca, Mg, Pt, Au, B, P, Eu, Sm, Ce, V, Ba, Ta, Sn, Hf, Gd, and Nd. 0 ≤ a ≤ 10, 0 <b≦8、2≦c≦13である。) [Effects of the Invention]

[0028] According to the present invention, it is possible to produce a cathode active material that exhibits electrochemical properties and stability at a similar level to that of a cathode active material produced using a precursor synthesized by a conventional coprecipitation method, using a precursor derived from waste cathode active material.

[0029] This makes it possible to separate positive electrode active material from end-of-life waste lithium secondary batteries or defective lithium secondary batteries generated during the manufacturing process, and utilize it as a raw material for producing new positive electrode active material. This contributes to reducing the overall cost of positive electrode active material and, consequently, lithium secondary batteries.

[0030] Furthermore, by reusing lithium-ion batteries that have reached the end of their lifespan or defective lithium-ion batteries generated during the manufacturing process, instead of discarding them, problems such as resource waste and environmental pollution can be reduced. [Brief explanation of the drawing]

[0031] [Figure 1] This is a cross-sectional SEM image of the precursor obtained when producing the positive electrode active material according to Example 1 of the present invention. [Figure 2] This is a cross-sectional SEM image of the precursor obtained when producing the positive electrode active material according to Example 3 of the present invention. [Figure 3] This is a cross-sectional SEM image of the precursor obtained when producing the positive electrode active material according to Comparative Example 3. [Figure 4] This is a cross-sectional SEM image of the precursor obtained when producing the positive electrode active material according to Comparative Example 4. [Modes for carrying out the invention]

[0032] For the convenience of making the present invention easier to understand, certain terms are defined in this application. Unless otherwise specifically defined in this application, the scientific and technical terms used in this invention have meanings that are generally understood by those of ordinary skill in the art. Furthermore, unless otherwise specified in the context, singular terms should be understood to include their plural forms, and plural terms should be understood to include their singular forms.

[0033] The following describes in more detail a method for producing a positive electrode active material for lithium secondary batteries using waste positive electrode active material according to the present invention, a positive electrode containing the positive electrode active material produced by the said method, and a lithium secondary battery using the said positive electrode.

[0034] Method for producing positive electrode active material for lithium secondary batteries using waste positive electrode active material According to one aspect of the present invention, a method for producing a positive electrode active material for a lithium secondary battery using a waste positive electrode active material is provided, comprising the steps of (a) mixing a waste positive electrode active material with a solvent to produce a slurry, (b) pulverizing the waste positive electrode active material in the slurry, (c) spray-drying the slurry containing the pulverized waste positive electrode active material to produce a precursor, and (d) heat-treating the precursor to obtain a lithium composite oxide.

[0035] The waste positive electrode active material used in step (a) above is used as a raw material for a positive electrode active material for a lithium secondary battery according to one aspect of the present invention.

[0036] The aforementioned waste positive electrode active material can be recovered from lithium secondary batteries (hereinafter referred to as waste lithium secondary batteries) or positive electrodes that have reached the end of their lifespan or are otherwise unusable due to defects, but is not necessarily limited to these sources.

[0037] For example, surplus positive electrode active material of NCM622 composition can be used to manufacture positive electrode active material of NCM811 composition by the manufacturing method defined in this application. In this case, even if the surplus positive electrode active material of NCM622 composition is not expired or defective, it may be referred to as waste positive electrode active material for convenience in this application.

[0038] Accordingly, in the following, all diverse lithium composite oxides used as raw materials in step (a) of the manufacturing method defined in this application, and positive electrode active materials containing them, are referred to as waste positive electrode active materials.

[0039] The waste positive electrode active material used in step (a) may include a lithium composite oxide represented by the following chemical formula 1 or chemical formula 2.

[0040] [Chemical formula 1] Li w Ni 1-x M x O 2-y X y (Here, M is at least one selected from Mn, Co, Al, B, Ba, Ce, Hf, Ta, Cr, Mg, V, Ti, Fe, Zr, Zn, Si, Y, Nb, Ga, Sn, Mo, W, Sr, Ge, Nd, Gd, and Cu. X is selected from F, S, and P. (0.5 ≤ w ≤ 1.5, 0 ≤ x ≤ 0.80, 0 ≤ y ≤ 2.)

[0041] [Chemical formula 2] Li w Ni 1-(x+y+z) Co x M1 y M2 z O2 (Here, M1 is at least one selected from Mn and Al. M2 is at least one selected from Mn, B, Ba, Ce, Hf, Ta, Cr, F, Mg, Al, V, Ti, Fe, Zr, Zn, Si, Y, Nb, Ga, Sn, Mo, W, P, Sr, Ge, Nd, Gd, and Cu. M1 and M2 are different elements. 0.5 ≤ w ≤ 1.5, 0 ≤ x ≤ 0.40, 0 <y≦0.40、0≦z≦0.40である。)

[0042] The waste positive electrode active material used in step (a) above can be appropriately selected according to the composition of the target positive electrode active material in the manufacturing method defined in this application. However, if the elements constituting the lithium composite oxide contained in the waste positive electrode active material are different from the elements constituting the lithium composite oxide contained in the target positive electrode active material in the manufacturing method defined in this application, the elements constituting the lithium composite oxide contained in the waste positive electrode active material may act as impurities. Therefore, it is preferable that the elements constituting the lithium composite oxide contained in the target positive electrode active material in the manufacturing method defined in this application include at least the elements constituting the lithium composite oxide contained in the waste positive electrode active material.

[0043] For example, in the manufacturing method defined in this application, if the target positive electrode active material is of NCM811 composition, the lithium composite oxide contained in the waste positive electrode active material may be a lithium composite oxide with a composition such as lithium nickel oxide (LNO), lithium cobalt oxide (LCO), and / or lithium manganese oxide (LMO), or a two-component lithium composite oxide or a three-component lithium composite oxide such as NCM424 and / or NCM622 may be used instead of the NCM811 composition.

[0044] Furthermore, the waste positive electrode active material used in step (a) may consist of a lithium composite oxide of the same composition, but is not necessarily limited to this, and may be provided as a mixture containing lithium composite oxides of different compositions.

[0045] The waste positive electrode active material used in step (a) can be recovered from the positive electrode of a waste lithium secondary battery that has reached the end of its lifespan or is otherwise unusable due to defects. For example, the waste positive electrode active material present as a positive electrode active material layer in the positive electrode can be obtained by separating the positive electrode active material layer from the positive electrode (or the positive electrode current collector used in the positive electrode) and then crushing the separated positive electrode active material layer.

[0046] In other cases, surplus positive electrode active material that is not processed into a positive electrode or lithium secondary battery may be used as the waste positive electrode active material.

[0047] The selected waste positive electrode active material is mixed with a solvent to prepare a slurry.

[0048] The solvent is not particularly limited as long as it is capable of creating an environment in which subsequent processes can be carried out without causing excessive chemical reactions with the waste positive electrode active material. For example, the solvent can be deionized water, distilled water, alcohol (ethyl alcohol, isopropyl alcohol), acetone, acidic aqueous solution, alkaline aqueous solution, or any mixture thereof.

[0049] The amount of solvent used to produce the slurry is not particularly limited, but it is preferable that the amount of solvent be adjusted so that the viscosity of the slurry is in the range of 3,000 to 20,000 cp without reducing the grinding efficiency of the waste positive electrode active material in the slurry during step (b) described later.

[0050] Furthermore, when producing the slurry, at least one sub-raw material containing an element selected from Mn, Co, Al, B, Ba, Ce, Hf, Ta, Cr, Mg, V, Ti, Fe, Zr, Zn, Si, Y, Nb, Ga, Sn, Mo, W, Sr, Ge, Nd, Gd, and Cu may be added.

[0051] By adding the sub-raw material to the slurry before grinding the waste positive electrode active material, the elements contained in the sub-raw material can be doped into the particles formed by grinding the waste positive electrode active material in step (b) described later, or the sub-raw material and / or the metal elements contained in the sub-raw material can be attached to the surface of the particles.

[0052] Furthermore, by adding the sub-raw material to the slurry before grinding the waste cathode active material, it is possible to obtain a cathode active material precursor without using the coprecipitation method conventionally used to synthesize precursors. Also, if the sub-raw material is added to the slurry after grinding the waste cathode active material, a further grinding step is required so that the elements contained in the sub-raw material are doped into the particles formed by grinding the waste cathode active material, or so that the sub-raw material and / or the metal elements contained in the sub-raw material adhere to the surface of the particles. Therefore, by adding the sub-raw material to the slurry before grinding the waste cathode active material, process efficiency can be improved.

[0053] Here, the sub-raw material can be provided in at least one form selected from sulfates, carbonates, nitrates, acetates, chlorides, hydroxides, and oxides.

[0054] For example, if the waste cathode active material has the composition of NCM424 and the target cathode active material in the manufacturing method defined in this application has the composition of NCM811, when manufacturing the slurry, (1) a nickel-containing sub-raw material (e.g., nickel-containing hydroxide), (2) a cobalt-containing sub-raw material (e.g., cobalt-containing hydroxide), and / or (3) a manganese-containing sub-raw material (e.g., manganese-containing hydroxide) may be added further.

[0055] The amount of at least one sub-raw material further added to the slurry can vary depending on the composition of the waste cathode active material used in step (a) and the composition of the cathode active material targeted in the manufacturing method defined herein.

[0056] Furthermore, when manufacturing the slurry, a binder may be added. The amount of binder added can vary depending on the content of the raw materials (the waste cathode active material and the sub-raw material) in the slurry and the molecular weight of the binder, but it is preferable that the amount added is 1% or less of the total weight of the raw materials (the waste cathode active material and the sub-raw material) in the slurry.

[0057] The binder acts as a binder for the waste cathode active material and the sub-raw material, improving the bonding strength between particles. This improves the bonding strength between the sub-raw material and / or the metal elements contained in the sub-raw material to the particles formed by crushing the waste cathode active material in step (b) described later. Furthermore, by suppressing particle breakage or disintegration in the process described later, it is possible to form a dense, nearly spherical precursor and lithium composite oxide.

[0058] The binder may be lithium hydroxide, sodium hydroxide, carboxylic acids or their salts (e.g., acetic acid, acrylic acid, citric acid, ascorbic acid, formic acid, lactic acid, malic acid, malonic acid, oxalic acid, tartaric acid, polycarboxylic acid, sodium polycarboxylic acid salt, ammonium polycarboxylic acid salt, amine polycarboxylic acid salt, sodium carboxymethylcellulose salt, etc.), saccharides (starch, monosaccharide, disaccharide, polysaccharide, dextrin, cyclodextrin or maltodextrin, etc.), polymers (polyvinyl alcohol, polyvinyl butyral, polyacrylic acid, polyvinyl chloride, carboxyl Compounds selected from polyvinyl chloride, polyvinyl fluoride, polymers containing ethylene oxide, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polyethylene glycol, polypropylene, polyamide-imide, polyimide, styrene-butadiene rubber, acrylic styrene-butadiene rubber, polyvinyl alcohol, sodium polyacrylate, copolymers of propylene and olefins having 2 to 8 carbon atoms, copolymers of (meth)acrylic acid and alkyl (meth)acrylate esters, and / or sodium dodecylbenzenesulfonate can be used.

[0059] Next, in step (b), the waste positive electrode active material from the slurry produced in step (a) is pulverized.

[0060] To pulverize the waste positive electrode active material, a dry or wet dispersion mill such as a ball mill, a beads mill (using beads typically used to pulverize metallic raw materials such as Al beads, Fe beads, or Zr beads), a vibration mill, an attritor mill, an air jet mill, a disk mill, or an air classifier mill can be used.

[0061] The average particle size of the waste positive electrode active material crushed in step (b) may be 0.1 μm to 5 μm.

[0062] After completing the grinding in step (b), the viscosity of the slurry is preferably in the range of 3,000 to 20,000 cp.

[0063] Because the slurry has the viscosity range described above, the condensation time during the spray drying in step (c) described later can be shortened, and since the amount of water lost during drying is small, it is possible to obtain a precursor with high density.

[0064] If the viscosity of the slurry is less than 3,000 cp, not only will the condensation time during spray drying be longer, but the density of the precursor will decrease as the amount of water lost during drying increases, and there is a risk that a large number of pores will be formed within the precursor. A precursor with low density and a large number of pores may exhibit weak particle strength. In this case, the positive electrode active material produced using the precursor may disintegrate during charging, discharging, or storage of a lithium secondary battery, which may result in reduced electrochemical properties or decreased stability of the lithium secondary battery.

[0065] On the other hand, if the viscosity of the slurry exceeds 20,000 cp, the fluidity of the slurry is low in the spray dryer where the spray drying in step (c) is performed. This not only prevents the achievement of sufficient process efficiency, but also makes it difficult to obtain a precursor with a near-spherical shape produced through spray drying.

[0066] Furthermore, before spray-drying the slurry in step (c), a binder may be added to the slurry. Here, the binder may be the same as the binder used in step (a) described above.

[0067] The amount of binder added can vary depending on the content of raw materials (the waste positive electrode active material and the sub-raw material) in the slurry and the molecular weight of the binder, but it is preferable that the amount added is 1% or less of the total weight of the raw materials (the waste positive electrode active material and the sub-raw material) in the slurry. If the binder has already been added in step (a), it is preferable that the sum of the amount of binder added in step (a) and the amount of binder added before step (c) be 1% or less of the total weight of the raw materials (the waste positive electrode active material and the sub-raw material) in the slurry.

[0068] Furthermore, before spray-drying the slurry in step (c), it is preferable that the temperature of the slurry be adjusted to within the range of 15 to 70°C. In this case, the temperature of the slurry before spray-drying refers to the temperature of the slurry before it is introduced into the spray dryer where the spray drying in step (c) is performed.

[0069] If the temperature of the slurry is below 15°C, the temperature difference with the environment in which the spray drying in step (c) is performed is large, which can result in excessively large thermal shock being applied to the particles (pulverized waste cathode active material) in the slurry. In this case, the particles (pulverized waste cathode active material) in the slurry may disintegrate.

[0070] On the other hand, when the temperature of the slurry exceeds 70°C, there is a problem in that it is difficult to accurately control the viscosity of the slurry due to the evaporation of the solvent in the slurry.

[0071] As described above, the slurry obtained by pulverizing the waste positive electrode active material can be spray-dried in step (c) to obtain a precursor.

[0072] Step (c) may be carried out in a spray dryer, and the spray dryer is not particularly limited as long as it is a spray drying device capable of spray drying the slurry containing the pulverized waste cathode active material to produce a dried precursor in a near-spherical shape, but ultrasonic sprayers, one-fluid injection nozzle sprayers, two-fluid injection nozzle sprayers, ultrasonic nozzle sprayers, filter expansion droplet generators (FEAGs), or disc-type droplet generators can be used.

[0073] The spray dryer in which the spray drying of step (c) is performed may include a spray nozzle and a drying chamber, and the slurry is atomized into droplets of a predetermined size through the spray nozzle and sprayed into the drying chamber where a relatively high-temperature gas flow is present.

[0074] The raw materials (the waste positive electrode active material and the sub-raw materials) in the droplets sprayed into the drying chamber are synthesized as dried precursors in a near-spherical shape under the temperature conditions of the drying chamber.

[0075] To facilitate the precursorization of the raw material substance within the droplet, it is preferable that the temperature inside the drying chamber be adjusted to a range of 50 to 500°C.

[0076] The viscosity of the slurry spray-dried in step (c) is preferably 3,000 to 20,000 cp, and the flow rate of the compressed air used to spray-dry the relatively high-viscosity slurry through the spray nozzle is preferably 40 L / min or more. If the flow rate of the compressed air is less than 40 L / min, the spray nozzle may become clogged with the relatively high-viscosity slurry, which may reduce the efficiency of the spray-drying process.

[0077] Furthermore, because the slurry has the viscosity range described above, the condensation time during spray drying can be shortened, and since the amount of water lost during drying is small, it is possible to obtain a precursor with high density.

[0078] If the viscosity of the slurry in step (c) is less than 3,000 cp, not only will the condensation time during spray drying be longer, but the density of the precursor will decrease as the amount of water lost during drying increases, and there is a risk that a large number of pores will be formed within the precursor. A precursor with low density and a large number of pores may exhibit weak particle strength. In this case, the positive electrode active material produced using the positive electrode active material may disintegrate during charging, discharging, or storage of a lithium secondary battery, which may result in a decrease in the electrochemical properties or stability of the lithium secondary battery.

[0079] On the other hand, if the viscosity of the slurry exceeds 20,000 cp, the fluidity of the slurry in the spray dryer is low, which not only prevents the achievement of sufficient process efficiency but also makes it difficult to obtain a precursor with a near-spherical shape produced through spray drying.

[0080] Furthermore, specific conditions for the spray drying performed in step (c) can be referenced from the manufacturing examples described later.

[0081] The average particle size of the precursor produced in step (c) is 0.1 μm to 20 μm, and the 50% cumulative volume particle size D of the precursor is 50 and 10% cumulative volume particle size D 10 Percentage D 50 / D 10 It is preferable that the value is between 1.92 and 6.24.

[0082] The aforementioned D 50 / D 10 It is preferable that the electrode density be at least 1.92 in order to improve the electrode density. 50 / D 10 If the value exceeds 6.24, the particle size distribution of the precursor is excessively broad, making it difficult to obtain a lithium composite oxide with uniform particle diameter through subsequent processes.

[0083] Furthermore, if a positive electrode active material is manufactured using a precursor derived from waste positive electrode active material by the manufacturing method defined in this application, instead of using a precursor synthesized by the coprecipitation method, the density of the lithium composite oxide contained in the positive electrode active material may decrease, or a large amount of pores may be formed in the lithium composite oxide, potentially resulting in weak particle strength. In this case, the positive electrode active material may disintegrate during charging, discharging, or storage of the lithium secondary battery using the positive electrode active material, potentially leading to reduced electrochemical properties or decreased stability of the lithium secondary battery.

[0084] However, in the case of a positive electrode active material produced by the method according to the present invention, the particle strength of the lithium composite oxide can be improved by increasing the density of the precursor derived from the waste positive electrode active material and simultaneously reducing the formation of pores. The particle strength of the precursor derived from the waste positive electrode active material or the positive electrode active material produced using the precursor derived from the waste positive electrode active material can be confirmed by measuring the particle size distribution that changes through artificial physical treatment of the precursor or the positive electrode active material.

[0085] For example, the D of the precursor measured after ultrasonically treating the precursor produced in step (c) at a frequency of 40 kHz for 60 seconds. 50 / D 10 The rate of change may be 43% or less.

[0086] After ultrasonic treatment of the precursor under the above conditions, the D of the precursor 50 / D 10 If the rate of change exceeds 43%, the particle strength of the precursor may be insufficient, and the stability of the positive electrode active material produced using the precursor may decrease.

[0087] Next, step (d) is performed, in which the precursor produced in step (c) is heat-treated to obtain a lithium composite oxide.

[0088] In one embodiment, before heat-treating the precursor produced in step (c) in step (d), at least one sub-raw material containing an element selected from Mn, Co, Al, B, Ba, Ce, Hf, Ta, Cr, F, Mg, V, Ti, Fe, Zr, Zn, Si, Y, Nb, Ga, Sn, Mo, W, P, Sr, Ge, Nd, Gd, and Cu, and at least one selected from lithium-containing raw materials may be added. The sub-raw material may be provided in at least one form selected from sulfates, carbonates, nitrates, acetates, chlorides, hydroxides, and oxides.

[0089] The amount of the sub-raw material introduced in step (d) can vary depending on the composition of the waste cathode active material and the composition of the cathode active material targeted in the manufacturing method defined in this application.

[0090] As a result, during the heat treatment of the mixture of the precursor and the sub-raw material in step (d), the elements contained in the sub-raw material may be doped into the lithium composite oxide, or at least a portion of the surface of the lithium composite oxide may be coated with an oxide represented by chemical formula 3, which will be described later.

[0091] By doping the lithium composite oxide with the elements contained in the aforementioned sub-raw material, the electrochemical properties and stability of the lithium composite oxide can be improved.

[0092] Examples of lithium-containing raw materials that can be used include lithium hydroxide, lithium carbonate, lithium nitrate, or lithium acetate.

[0093] The lithium-containing raw material introduced in step (d) is preferably mixed such that the ratio of the number of lithium atoms (Li) to the total number of atoms of metal elements other than lithium (Metal) in step (d) is within the range of 1.5 or less.

[0094] If the lithium-containing raw material is further added when the mixture is produced in step (e) described later, it is preferable that the lithium compound added in step (d) is mixed such that the ratio of the number of lithium atoms Li to the total number of atoms Metal of metal elements other than lithium in the raw material is in the range of 1.0 or less, and the lithium compound added in step (e) is mixed such that the ratio of the number of lithium atoms Li to the total number of atoms Metal of metal elements other than lithium in the raw material is in the range of 1.5 or less.

[0095] The lithium-containing raw material reacts with the precursor to induce lithiation of the precursor, and at the same time acts as a binder for the precursor and the sub-raw material, thereby improving the bonding strength between particles.

[0096] The heat treatment temperature in step (d) may be 300 to 1,000°C, and the heat treatment temperature in step (d) can be varied depending on the composition of the waste positive electrode active material and the composition of the positive electrode active material targeted in the manufacturing method defined in this application.

[0097] More specifically, the heat treatment in step (d) may be carried out in a firing furnace under an O2 atmosphere, with the temperature raised to 300-1,000°C at a rate of 2-5°C per minute for 5-12 hours. If the heat treatment temperature in step (d) is less than 300°C, the firing of the precursor will proceed insufficiently, resulting in insufficient crystal growth of the lithium composite oxide. On the other hand, if the heat treatment temperature in step (c) exceeds 1,000°C, thermal decomposition of the lithium composite oxide may occur, leading to a decrease in particle strength or particle collapse.

[0098] The lithium composite oxide obtained in step (d) may include primary particles and secondary particles formed by the aggregation of the primary particles. Similarly, the lithium composite oxide is represented by chemical formula 1 or chemical formula 2, but does not necessarily have to have the same composition as the waste cathode active material used as a raw material.

[0099] Furthermore, a step (e) may be performed in which a mixture is produced by mixing at least one sub-raw material containing an element selected from Mn, Co, Al, B, Ba, Ce, Hf, Ta, Cr, F, Mg, V, Ti, Fe, Zr, Zn, Si, Y, Nb, Ga, Sn, Mo, W, P, Sr, Ge, Nd, Gd, and Cu with the lithium composite oxide obtained in step (d) to produce a mixture, and then heat-treating the mixture.

[0100] The content of the sub-raw material introduced in step (e) can vary depending on the composition of the waste cathode active material and the composition of the cathode active material targeted in the manufacturing method defined herein.

[0101] The aforementioned sub-raw material can be provided in at least one form selected from sulfates, carbonates, nitrates, acetates, chlorides, hydroxides, and oxides.

[0102] In step (e) above, during the heat treatment of the mixture of the lithium composite oxide and the sub-raw material, at least a portion of the surface of the lithium composite oxide can be coated with an oxide represented by the following chemical formula 3.

[0103] [Chemical formula 3] Li a A b O c (Here, A is at least one selected from Ni, Mn, Co, Fe, Cu, Nb, Mo, Ti, Al, Cr, Zr, Zn, Na, K, Ca, Mg, Pt, Au, B, P, Eu, Sm, Ce, V, Ba, Ta, Sn, Hf, Gd, and Nd. 0 ≤ a ≤ 10, 0 <b≦8、2≦c≦13である。)

[0104] The oxide represented by chemical formula 3 may be present on at least a portion of the surface of the lithium composite oxide, and the region on the surface of the lithium composite oxide in which the oxide represented by chemical formula 3 is present can be defined as a coating layer.

[0105] Furthermore, if the lithium composite oxide includes primary particles and secondary particles formed by the aggregation of the primary particles, the oxide represented by chemical formula 2 may be present on at least a portion of the surface of the primary particles (e.g., the interface between the primary particles) and / or the secondary particles formed by the aggregation of the primary particles. The coating layer may exist as a layer that continuously or discontinuously coats the surface of the primary particles and / or the secondary particles formed by the aggregation of the primary particles. If the coating layer exists discontinuously, it may exist in an island form.

[0106] Furthermore, depending on the circumstances, the oxide may be present not only at least a portion of the interfaces between the primary particles and the surfaces of the secondary particles, but also in the internal voids formed within the secondary particles.

[0107] In this case, the coating layer may exist in the form of a solid solution that does not form a boundary with the primary particles and / or the secondary particles formed by the aggregation of the primary particles, but is not limited to this.

[0108] The coating layer can remove residual lithium by-products present on the surface of the lithium composite oxide, thereby improving the stability of the lithium composite oxide and contributing to improving the electrochemical properties of the lithium composite oxide.

[0109] Furthermore, as described in step (d), when producing the mixture in step (e), the lithium-containing raw material can be added in addition.

[0110] The lithium-containing raw material further added in step (e) is a lithium compound that can induce further lithification of the lithium composite oxide during the heat treatment in step (e), and the lithium compound can be lithium hydroxide, lithium carbonate, lithium nitrate, or lithium acetate.

[0111] The lithium compound further added in step (e) is preferably mixed such that the ratio of lithium atoms (Li) to the total number of metal elements other than lithium (Metal) in the final product, the lithium composite oxide, is in the range of 1.5 or less.

[0112] The heat treatment temperature in step (e) for forming the coating layer on the surface of the lithium composite oxide may be 300 to 1,000°C. More specifically, the heat treatment in step (e) may be carried out in a firing furnace under an O2 atmosphere, with the temperature raised to 300 to 1,000°C at a rate of 2 to 5°C per minute for 5 to 12 hours. If the heat treatment temperature in step (e) is less than 300°C, the crystal growth of the oxide constituting the coating layer on the surface of the lithium composite oxide will be insufficient. On the other hand, if the heat treatment temperature in step (e) exceeds 1,000°C, thermal decomposition of the lithium composite oxide and / or the oxide may occur.

[0113] Furthermore, prior to performing step (e), the lithium composite oxide obtained in step (d) may be subjected to disintegration, distribution, iron removal, and / or washing.

[0114] In particular, a water washing step may be selectively performed on the lithium composite oxide obtained in step (d) before performing step (e).

[0115] By reacting the lithium composite oxide obtained in step (d) with the water washing solution to remove impurities remaining in the lithium composite oxide (e.g., residual lithium by-products and / or unreacted sub-raw material substances), a deliberate reaction between the lithium composite oxide and the sub-raw material substances for forming a coating layer on the surface of the lithium composite oxide can be induced in step (e).

[0116] positive electrode active material According to another aspect of the present invention, a positive electrode active material is provided that is produced by the manufacturing method described above, i.e., using waste positive electrode active material.

[0117] The positive electrode active material is provided as an aggregate comprising primary particles made of lithium composite oxide capable of lithium intercalation / deintercalation, and secondary particles formed by the aggregation of multiple primary particles.

[0118] Here, the primary particle refers to a single grain (grain or crystallite), and the secondary particle refers to an aggregate formed by the aggregation of multiple primary particles. The primary particle may have a rod-like shape, an elliptical shape, and / or an amorphous shape. Voids and / or grain boundaries may exist between the primary particles constituting the secondary particle. In other embodiments, the positive electrode active material may also include a lithium composite oxide existing in single-crystal form with an average particle size of 0.1 μm or more.

[0119] The primary particles can form internal voids within the secondary particles by separating them from adjacent primary particles. Furthermore, the primary particles do not form grain boundaries by contacting adjacent primary particles, but rather form surfaces within the secondary particles by contacting the internal voids. The surface of the primary particles on the outermost surface of the secondary particles that is exposed to the outside air forms the surface of the secondary particle.

[0120] Here, the average particle size of the primary particles (where the average particle size of the primary particles may be the average major axis length of the primary particles) is within the range of 0.1 μm to 5 μm, thereby achieving the optimal density of the positive electrode manufactured using the positive electrode active material according to various embodiments of the present invention. Furthermore, the positive electrode active material manufactured using waste positive electrode active material by the manufacturing method defined in this application has improved particle strength, so even if the average particle size of the primary particles is within the range of 0.1 μm to 5 μm, the possibility of particle breakage is reduced.

[0121] The average particle size of secondary particles formed by the aggregation of multiple primary particles can vary depending on the number of aggregated primary particles, but is generally between 3 μm and 20 μm.

[0122] The lithium composite oxide can be represented by the following chemical formula 1 or chemical formula 2.

[0123] [Chemical formula 1] Li w Ni 1-x M x O 2-y X y (Here, M is at least one selected from Mn, Co, Al, B, Ba, Ce, Hf, Ta, Cr, Mg, V, Ti, Fe, Zr, Zn, Si, Y, Nb, Ga, Sn, Mo, W, Sr, Ge, Nd, Gd, and Cu. X is selected from F, S, and P. (0.5 ≤ w ≤ 1.5, 0 ≤ x ≤ 0.80, 0 ≤ y ≤ 2.)

[0124] [Chemical formula 2] Li w Ni 1-(x+y+z) Co x M1 y M2 z O2 (Here, M1 is at least one selected from Mn and Al. M2 is at least one selected from Mn, B, Ba, Ce, Hf, Ta, Cr, F, Mg, Al, V, Ti, Fe, Zr, Zn, Si, Y, Nb, Ga, Sn, Mo, W, P, Sr, Ge, Nd, Gd, and Cu. M1 and M2 are different elements. 0.5 ≤ w ≤ 1.5, 0 ≤ x ≤ 0.40, 0 <y≦0.40、0≦z≦0.40である。)

[0125] The composition of the lithium composite oxide can vary depending on the composition of the waste cathode active material used as a raw material in the manufacturing method defined herein, and the type and composition of the sub-raw materials further used therein.

[0126] In particular, if the positive electrode active material according to the present invention has a lithium composite oxide containing at least (1) one selected from manganese and aluminum; (2) nickel; and (3) cobalt, then 3 wt% or more, preferably 5 wt% or more, of the total weight of (1) one selected from manganese and aluminum; (2) nickel; and (3) cobalt in the lithium composite oxide may be derived from waste positive electrode active material.

[0127] The positive electrode active material according to the present invention is a positive electrode active material manufactured using waste positive electrode active material. The content of components derived from the waste positive electrode active material in the positive electrode active material can vary depending on the composition of the waste positive electrode active material or the composition of the target positive electrode active material. However, the higher the content of components derived from the waste positive electrode active material in the final product positive electrode active material, the greater the cost reduction of the positive electrode active material and, consequently, the lithium secondary battery. However, if the content of components derived from the waste positive electrode active material in the positive electrode active material becomes excessively high, there is a risk that the electrochemical properties or stability of the positive electrode active material will decrease. Therefore, it is preferable that the total content of components derived from the waste positive electrode active material in the positive electrode active material be 70 wt% or less.

[0128] Furthermore, the 50% cumulative volume particle size D of the positive electrode active material produced using waste positive electrode active material by the manufacturing method defined in this application 50 and 10% cumulative volume particle size D 10 Percentage D 50 / D 10 It is preferably 2.0 to 7.0 in order to improve the electrode density produced using the positive electrode active material.

[0129] Furthermore, if a positive electrode active material is manufactured using a precursor derived from waste positive electrode active material by the manufacturing method defined in this application, instead of using a precursor synthesized by the coprecipitation method, the density of the lithium composite oxide contained in the positive electrode active material may decrease, or a large amount of pores may be formed in the lithium composite oxide, potentially resulting in weak particle strength. In this case, the positive electrode active material may disintegrate during charging, discharging, or storage of the lithium secondary battery using the positive electrode active material, potentially leading to a decrease in the electrochemical properties or stability of the lithium secondary battery.

[0130] However, in the case of a positive electrode active material manufactured by the manufacturing method defined in this application, the particle strength of the lithium composite oxide can be improved by increasing the density of the precursor derived from the waste positive electrode active material while simultaneously reducing pore formation. The particle strength of the positive electrode active material manufactured using the precursor derived from the waste positive electrode active material can be confirmed by measuring the particle size distribution that changes through artificial physical treatment of the precursor or the positive electrode active material.

[0131] For example, the D content of the lithium composite oxide measured after ultrasonic treatment of the positive electrode active material at a frequency of 40 kHz for 60 seconds. 50 / D 10 The rate of change may be 10% or less.

[0132] Under the conditions described above, the lithium composite oxide D after ultrasonic treatment of the positive electrode active material 50 / D 10If the rate of change exceeds 10%, the particle strength of the positive electrode active material may be insufficient, which could lead to a decrease in the stability of the lithium secondary battery using the positive electrode active material.

[0133] Furthermore, the positive electrode active material may include a coating layer that covers at least a portion of the surface of the primary particles (for example, the interfaces between the primary particles) and / or the surface of the secondary particles formed by the aggregation of the primary particles.

[0134] For example, the coating layer may be present so as to cover at least a portion of the exposed surface of the primary particles. In particular, the coating layer may be present so as to cover at least a portion of the exposed surface of the primary particles that are located on the outermost edge of the secondary particles.

[0135] As a result, the coating layer may exist as a layer that continuously or discontinuously coats the surface of the primary particles and / or the secondary particles formed by the aggregation of the primary particles. If the coating layer exists discontinuously, it may exist in an island form.

[0136] Furthermore, depending on the circumstances, the oxide may be present not only at least a portion of the interfaces between the primary particles and the surfaces of the secondary particles, but also in the internal voids formed within the secondary particles.

[0137] The coating layer present in this manner can contribute to improving the electrochemical properties and stability of the positive electrode active material.

[0138] In this case, the coating layer may exist in the form of a solid solution that does not form a boundary with the primary particles and / or the secondary particles formed by the aggregation of the primary particles, but is not limited to this.

[0139] In addition, at least one oxide represented by the following Chemical Formula 2 may be present in the coating layer. That is, the coating layer can be defined as a region where an oxide represented by the following Chemical Formula 3 is present.

[0140] [Chemical Formula 3] Li a A b O c (Here, A is at least one selected from Ni, Mn, Co, Fe, Cu, Nb, Mo, Ti, Al, Cr, Zr, Zn, Na, K, Ca, Mg, Pt, Au, B, P, Eu, Sm, Ce, V, Ba, Ta, Sn, Hf, Gd, and Nd, 0 ≦ a ≦ 10, 0 < b ≦ 8, 2 ≦ c ≦ 13.)

[0141] The oxide represented by Chemical Formula 3 is an oxide in which lithium and the element represented by A are combined, or an oxide of A. The oxide is, for example, Li a W b ​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​ In other embodiments, the oxide represented by chemical formula 3 may be an oxide composed of lithium and at least two elements represented by A, or may further contain an oxide composed of lithium and at least two elements represented by A. An oxide composed of lithium and at least two elements represented by A is, for example, Li a (W / Ti) b O c Li a (W / Zr) b O c Li a (W / Ti / Zr) b O c Li a (W / Ti / B) b O c Other examples are also acceptable, but are not limited to those.

[0143] As described above, the positive electrode active material according to this embodiment has enhanced structural stability by including a coating layer that covers at least a portion of the surface of the primary particles (e.g., the interface between the primary particles) and / or the secondary particles formed by the aggregation of the primary particles. Furthermore, by using such a positive electrode active material as a positive electrode active material for lithium secondary batteries, the lifespan and capacity characteristics can be improved.

[0144] Furthermore, the coating layer can reduce residual lithium within the lithium composite oxide and simultaneously act as a diffusion path for lithium ions, thereby influencing the improvement of the efficiency characteristics of the lithium secondary battery.

[0145] Furthermore, the oxide can exhibit a concentration gradient that decreases from the surface of the secondary particle toward the center of the secondary particle. This allows the concentration of the oxide to decrease from the outermost surface of the secondary particle toward the center of the secondary particle.

[0146] As described above, the oxide exhibits a concentration gradient that decreases from the surface of the secondary particles toward the center of the secondary particles, thereby effectively reducing the residual lithium present on the surface of the positive electrode active material and preventing side reactions caused by unreacted residual lithium. Furthermore, the oxide can prevent a decrease in crystallinity in the inner region of the surface of the positive electrode active material. In addition, the oxide can prevent the overall structure of the positive electrode active material from collapsing during the electrochemical reaction.

[0147] Lithium-ion rechargeable battery According to yet another aspect of the present invention, a positive electrode can be provided comprising a positive electrode current collector and a layer of the positive electrode active material described above formed on the positive electrode current collector. Here, the positive electrode active material layer may include a positive electrode active material produced by the manufacturing method according to the various embodiments of the present invention described above.

[0148] The positive electrode current collector is not particularly limited as long as it does not induce chemical changes in the battery and is conductive. For example, stainless steel, aluminum, nickel, titanium, calcined carbon, or aluminum or stainless steel with a surface treatment of carbon, nickel, titanium, silver, etc. may be used. The positive electrode current collector may also have a thickness of 3 to 500 μm, and fine irregularities can be formed on the surface of the current collector to increase the adhesion strength of the positive electrode active material. For example, it may be used in various forms such as film, sheet, foil, net, porous material, foam, or nonwoven fabric.

[0149] The positive electrode active material layer may be manufactured by applying a positive electrode slurry composition, which includes a conductive material and, if necessary, a binder, together with the positive electrode active material, to the positive electrode current collector.

[0150] In this case, the positive electrode active material may be included in an amount of 80 to 99 wt%, more specifically 85 to 98.5 wt%, relative to the total weight of the positive electrode active material layer. When included in this content range, excellent capacity characteristics can be observed, but the material is not necessarily limited to this range.

[0151] The conductive material is used to impart conductivity to the electrodes and can be used without particular limitations as long as it has electronic conductivity in the battery without causing a chemical change. Specific examples include graphite such as natural graphite or artificial graphite, carbon-based materials such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, thermal black, and carbon fiber, metal powders or metal fibers such as copper, nickel, aluminum, and silver, conductive whiskers such as zinc oxide and potassium titanate, conductive metal oxides such as titanium oxide, or conductive polymers such as polyphenylene derivatives. One of these may be used alone or in mixtures of two or more. The conductive material may be included in an amount of 0.1 to 15% by weight relative to the total weight of the positive electrode active material layer.

[0152] The binder plays a role in improving adhesion between positive electrode active material particles and adhesion between the positive electrode active material and the current collector. Specific examples include polyvinylidene fluoride (PVDF), vinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinyl alcohol, polyacrylonitrile, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated-EPDM, styrene-butadiene rubber (SBR), fluororubber, or various copolymers thereof, of which one or more may be used. The binder may be included in an amount of 0.1 to 15% by weight relative to the total weight of the positive electrode active material layer.

[0153] The positive electrode may be manufactured by a conventional positive electrode manufacturing method, except that the positive electrode active material is used. Specifically, the positive electrode may be manufactured by applying a positive electrode slurry composition, prepared by dissolving or dispersing the positive electrode active material and selectively a binder and conductive material in a solvent, onto a positive electrode current collector, followed by drying and rolling.

[0154] The solvent may be any solvent commonly used in the art, such as dimethyl sulfoxide (DMSO), isopropyl alcohol, N-methylpyrrolidone (NMP), acetone, or water, and one or more of these may be used individually or in mixtures of two or more. The amount of solvent used should be such that it dissolves or disperses the cathode active material, conductive material, and binder, and then provides a viscosity that allows for excellent thickness uniformity during coating for cathode manufacturing, taking into consideration the coating thickness and production yield of the slurry.

[0155] In other embodiments, the positive electrode may be manufactured by casting the positive electrode slurry composition onto a separate support, peeling it off the support, and then laminating the resulting film onto the positive electrode current collector.

[0156] Furthermore, according to yet another aspect of the present invention, an electrochemical element including the aforementioned positive electrode may be provided. Specifically, the electrochemical element may be a battery, a capacitor, or the like, and more specifically, a lithium secondary battery.

[0157] The lithium secondary battery may specifically include a positive electrode, a negative electrode positioned opposite the positive electrode, and a separator and electrolyte interposed between the positive and negative electrodes. The lithium secondary battery may also be provided as an anode-free lithium secondary battery. Here, since the positive electrode is as described above, for convenience, a detailed explanation will be omitted, and only the remaining components not mentioned above will be described in detail below. Furthermore, the explanation related to the negative electrode described later should be understood as assuming the presence of a negative electrode in the lithium secondary battery.

[0158] The lithium secondary battery may further selectively include a battery container for housing the electrode assembly comprising the positive electrode, the negative electrode, and the separator, and a sealing member for sealing the battery container.

[0159] The negative electrode may include a negative electrode current collector and a negative electrode active material layer located on the negative electrode current collector.

[0160] The negative electrode current collector is not particularly limited as long as it has high conductivity without inducing chemical changes in the battery. For example, copper, stainless steel, aluminum, nickel, titanium, calcined carbon, copper or stainless steel surface-treated with carbon, nickel, titanium, silver, etc., and aluminum-cadmium alloy may be used. The negative electrode current collector may also typically have a thickness of 3 μm to 500 μm, and, similar to the positive electrode current collector, fine irregularities can be formed on the surface of the current collector to strengthen the bonding force of the negative electrode active material. For example, it may be used in various forms such as film, sheet, foil, net, porous material, foam, and nonwoven fabric.

[0161] The negative electrode active material layer may be manufactured by applying a negative electrode slurry composition, which includes the negative electrode active material together with a conductive material and, if necessary, a selective binder, to the negative electrode current collector.

[0162] As the negative electrode active material, a compound capable of reversible intercalation and deintercalation of lithium may be used. Specific examples include carbonaceous materials such as artificial graphite, natural graphite, graphitized carbon fiber, and amorphous carbon; metallic compounds capable of alloying with lithium, such as Si, Al, Sn, Pb, Zn, Bi, In, Mg, Ga, Cd, Si alloys, Sn alloys, or Al alloys; and SiO2. β Examples include lithium-doped and dedoped metal oxides such as (0<β<2), SnO2, vanadium oxide, and lithium vanadium oxide, or composites containing the metallic compound and carbonaceous material, such as Si-C composites or Sn-C composites. One or more of these mixtures may be used. A metallic lithium thin film may also be used as the negative electrode active material. Furthermore, low-crystalline carbon and high-crystalline carbon may all be used as the carbon material. Typical examples of low-crystalline carbon include soft carbon and hard carbon, while typical examples of high-crystalline carbon include amorphous, plate-like, flaky, spherical, or fibrous natural or artificial graphite, Kish graphite, pyrolytic carbon, mesophase pitch-based carbon fiber, meso-carbon microbeads, mesophase pitches, and high-temperature calcined carbon such as petroleum or coal tar pitch-derived cokes.

[0163] The aforementioned negative electrode active material may be present in an amount of 80 to 99 wt% based on the total weight of the negative electrode active material layer.

[0164] The binder may be added in an amount of 0.1 to 10 wt% based on the total weight of the negative electrode active material layer, as a component that assists in bonding between the conductive material, active material, and current collector. Examples of such binders include polyvinylidene fluoride (PVDF), polyvinyl alcohol, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated EPDM, styrene-butadiene rubber, nitrile-butadiene rubber, fluororubber, and various copolymers thereof.

[0165] The conductive material may be added as a component to further improve the conductivity of the negative electrode active material, in an amount of 10% by weight or less, preferably 5% by weight or less, based on the total weight of the negative electrode active material layer. Such a conductive material is not particularly limited as long as it has conductivity without inducing a chemical change in the battery, and for example, graphite such as natural graphite or artificial graphite, carbon black such as acetylene black, Ketjen black, channel black, furnace black, lamp black, and thermal black, conductive fibers such as carbon fibers and metal fibers, metal powders such as carbon fluoride, aluminum, and nickel powder, conductive whiskers such as zinc oxide and potassium titanate, conductive metal oxides such as titanium oxide, and conductive materials such as polyphenylene derivatives may be used.

[0166] In one embodiment, the negative electrode active material layer may be manufactured by coating a negative electrode slurry composition, which is prepared by dissolving or dispersing a negative electrode active material and a binder and conductive material selectively in a solvent, onto a negative electrode current collector and then drying it, or by casting the negative electrode slurry composition onto a separate support, peeling it off the support, and then laminating the resulting film onto the negative electrode current collector.

[0167] In other embodiments, the negative electrode active material layer may be manufactured by coating a negative electrode slurry composition, prepared by dissolving or dispersing a negative electrode active material and a binder and conductive material selectively in a solvent, onto a negative electrode current collector and drying it, or by casting the negative electrode slurry composition onto a separate support, peeling it off the support, and laminating the resulting film onto the negative electrode current collector.

[0168] On the other hand, in the lithium secondary battery, the separator separates the negative electrode and the positive electrode and provides a passage for lithium ions to move. Generally, any separator commonly used in lithium secondary batteries can be used without particular limitations, and it is especially preferable that the separator has low resistance to ion movement of the electrolyte and excellent electrolyte moisture absorption capacity. Specifically, porous polymer films, such as ethylene homopolymers, propylene homopolymers, ethylene / butene copolymers, ethylene / hexene copolymers, and ethylene / methacrylate copolymers, or laminated structures of two or more layers thereof may be used. Alternatively, ordinary porous nonwoven fabrics, such as nonwoven fabrics made of high-melting-point glass fibers or polyethylene terephthalate fibers, may be used. Furthermore, to ensure heat resistance or mechanical strength, coated separators containing ceramic components or polymeric substances may be used, and may be selectively used as single-layer or multi-layer structures.

[0169] Furthermore, the electrolytes used in the present invention include, but are not limited to, organic liquid electrolytes, inorganic liquid electrolytes, solid polymer electrolytes, gel-type polymer electrolytes, solid inorganic electrolytes, and molten inorganic electrolytes that can be used in the manufacture of lithium secondary batteries.

[0170] Specifically, the electrolyte may include an organic solvent and a lithium salt.

[0171] The organic solvent can be any solvent that serves as a medium through which ions involved in the electrochemical reaction of the battery can move, without any particular limitations. Specifically, the organic solvent may be an ester solvent such as methyl acetate, ethyl acetate, γ-butyrolactone, or ε-caprolactone; an ether solvent such as dibutyl ether or tetrahydrofuran; a ketone solvent such as cyclohexanone; an aromatic hydrocarbon solvent such as benzene or fluorobenzene; dimethyl carbonate (DMC), diethyl carbonate (DEC), methyl ethyl carbonate (MEC), ethyl methyl carbonate (EMC), ethylene carbonate (EC), or propylene carbonate (propylene Carbonate solvents such as carbonate (PC), alcohol solvents such as ethyl alcohol and isopropyl alcohol, nitriles such as R-CN (where R is a linear, branched, or cyclic hydrocarbon group having 2 to 20 carbon atoms, and may include a double-bonded aromatic ring or ether bond), amides such as dimethylformamide, dioxolanes such as 1,3-dioxolane, or sulfolanes may be used. Among these, carbonate solvents are preferred, and a mixture of a cyclic carbonate (e.g., ethylene carbonate or propylene carbonate) having high ionic conductivity and high dielectric constant that can improve the charge and discharge performance of the battery, and a low-viscosity linear carbonate compound (e.g., ethyl methyl carbonate, dimethyl carbonate, or diethyl carbonate) is more preferred. In this case, the electrolyte performance can be improved by mixing the cyclic carbonate and the linear carbonate in a volume ratio of about 1:1 to about 1:9.

[0172] The lithium salt may be any compound capable of providing lithium ions for use in a lithium secondary battery, without any particular limitations. Specifically, the lithium salt may be LiPF6, LiClO4, LiAsF6, LiBF4, LiSbF6, LiAlO4, LiAlCl4, LiCF3SO3, LiC4F9SO3, LiN(C2F5SO3), LiN(C2F5SO2)2, LiN(CF3SO2)2, LiCl, LiI, or LiB(C2O4)2, etc. The concentration of the lithium salt is preferably within the range of 0.1 to 2.0 M. When the concentration of the lithium salt falls within this range, the electrolyte has appropriate conductivity and viscosity, exhibiting excellent electrolyte performance and allowing lithium ions to move effectively.

[0173] In addition to the electrolyte components, the electrolyte may further contain one or more additives for the purpose of improving battery life characteristics, suppressing the decrease in battery capacity, and improving battery discharge capacity, such as haloalkylene carbonate compounds such as difluoroethylene carbonate, pyridine, triethyl phosphite, triethanolamine, cyclic ethers, ethylenediamine, n-glyme, hexaphosphate triamide, nitrobenzene derivatives, sulfur, quinone imine dyes, N-substituted oxazolidinone, N,N-substituted imidazolidine, ethylene glycol dialkyl ether, ammonium salts, pyrrole, 2-methoxyethanol, or aluminum trichloride. In this case, the additive may be present in an amount of 0.1 to 5% by weight relative to the total weight of the electrolyte.

[0174] As described above, the lithium secondary battery containing the positive electrode active material according to the present invention exhibits excellent discharge capacity, output characteristics, and life characteristics in a stable manner, making it useful in portable devices such as mobile phones, laptop computers, and digital cameras, as well as in the electric vehicle field, such as hybrid electric vehicles (HEVs).

[0175] The external shape of the lithium secondary battery according to the present invention is not particularly limited, but it may be cylindrical, rectangular, pouch-shaped, or coin-shaped using a can. Furthermore, the lithium secondary battery can be used not only as a battery cell used as a power source for small devices, but may also be preferably used as a unit battery in medium-to-large battery modules containing multiple battery cells.

[0176] According to yet another aspect of the present invention, a battery module and / or a battery pack including the lithium secondary battery as a unit cell can be provided.

[0177] The battery module or battery pack can be used as a power source for one or more medium-to-large devices, including power tools, electric vehicles (EVs), hybrid electric vehicles, and plug-in hybrid electric vehicles (PHEVs), or power storage systems.

[0178] The present invention will be described in more detail below with reference to examples. However, these examples are for illustrative purposes only and should not be construed as limiting the scope of the present invention.

[0179] Manufacturing Example 1. Production of positive electrode active material using waste positive electrode active material (1) Example 1 Li[Ni 1 / 3 Co 1 / 3 Mn 1 / 3 Waste positive electrode active material with an average particle size of 15 μm was recovered from lithium secondary batteries manufactured and used with 2O2, and the composition of the recovered waste positive electrode active material was confirmed using ICP-OES.

[0180] After filling a bead mill (Netch LabStar Mini) with 0.6mm and 0.3mm beads to 70% of its internal space, distilled water (DIW) was added in a 1:1 weight ratio to the beads, and the mixture was circulated.

[0181] The waste cathode active material, nickel hydroxide, and cobalt hydroxide were weighed and placed in a bead mill so that the molar ratio of Ni, Co, and Mn in the target cathode active material was 80:10:10 relative to 0.2 kg of the waste cathode active material. The mixture was then stirred to produce a slurry. Next, the slurry was pulverized in the bead mill so that the average particle size of the waste cathode active material was 0.5 μm or less. After pulverization was completed, the viscosity of the slurry was measured to be 5,000 cp and the temperature of the slurry was measured to be 25°C.

[0182] The prepared slurry was placed in a raw material storage container attached to a spray dryer (Toshin Giken, DJE003R) and stirred at 200 rpm to prevent sedimentation and separation of the slurry. The stirring speed of the slurry was adjusted to decrease as the amount of slurry in the raw material storage container decreased.

[0183] The slurry was transferred to the spray drying chamber at a transfer speed of 1 kg / hour by a tubular feeding pump. The atomizer used for spray drying was a two-fluid injection nozzle, and the input temperature was maintained at 235°C and the discharge temperature at 100°C or higher.

[0184] In the drying chamber, the temperature was kept constant at 235°C to rapidly remove moisture, and the slurry sprayed by the injection nozzle was atomized into droplets to produce a spherical ultrafine powder (precursor).

[0185] In the spray drying process, high-temperature air, heated by drawing in ambient air, was brought into contact with droplets sprayed in a co-current flow during the drying process. Through this process, evaporated water vapor was either released into the atmosphere or removed using a vapor trap to produce the precursor. A cross-sectional SEM image of the produced precursor is shown in Figure 1.

[0186] Next, the manufactured precursor was placed in a zero-gravity mixer, lithium hydroxide was added, and the mixture was stirred for 1 hour to produce a mixture. The amount of lithium hydroxide added was such that the ratio of the total number of Li atoms in the precursor and the total number of Li atoms added as lithium hydroxide to the total number of metal elements other than Li in the precursor (Metal) was 1.05 (Li / Metal).

[0187] Next, the mixture was heat-treated in a calcination furnace under an O2 atmosphere, increasing the temperature to 680°C at a rate of 2°C per minute for 12 hours to obtain a lithium composite oxide (positive electrode active material).

[0188] ICP-OES analysis of the obtained positive electrode active material revealed that the composition of the positive electrode active material is Li 1.05 Ni 0.8 Co 0.1 Mn 0.1 It was confirmed to be O2 (NCM811). Furthermore, as shown in Table 1 below, the weight of the waste cathode active material used as a raw material was calculated to be 30.9 wt% of the total weight of the cathode active material finally obtained.

[0189] [Table 1]

[0190] (2) Example 2 The positive electrode active material was manufactured in the same manner as in Example 1, except that the content of pure water in the slurry was adjusted so that the viscosity of the slurry was 8,000 cp before spray drying.

[0191] ICP-OES analysis of the obtained positive electrode active material revealed that the composition of the positive electrode active material is Li 1.05 Ni 0.8 Co 0.1 Mn 0.1 It was confirmed to be O2 (NCM811). Furthermore, the weight of the waste positive electrode active material relative to the total weight of the obtained positive electrode active material was the same as in Example 1.

[0192] (3) Example 3 The positive electrode active material was produced in the same manner as in Example 1, except that the content of pure water in the slurry was adjusted so that the viscosity of the slurry became 15,000 cp before spray drying.

[0193] As a result of ICP-OES analysis of the obtained positive electrode active material, the composition of the positive electrode active material was Li 1.05 Ni 0.8 Co 0.1 Mn 0.1 O2 (NCM811), which was confirmed. Also, the weight of the waste positive electrode active material with respect to the total weight of the obtained positive electrode active material was the same as in Example 1.

[0194] The cross-sectional SEM image of the precursor obtained when producing the positive electrode active material according to Example 3 is shown in FIG. 2.

[0195] (4) Example 4 The positive electrode active material was produced in the same manner as in Example 1, except that ZrO2 was weighed and mixed so as to be 0.1 mol% with respect to the precursor before heat-treating the precursor.

[0196] As a result of ICP-OES analysis of the obtained positive electrode active material, the composition of the positive electrode active material was Li 1.05 Ni 0.79 Co 0.09 Mn 0.09 Zr 0.01 O2, which was confirmed. Also, the weight of the waste positive electrode active material with respect to the total weight of the obtained positive electrode active material was the same as in Example 1.

[0197] (5) Example 5 The positive electrode active material was produced in the same manner as in Example 1, except that TiO2 was weighed and mixed so as to be 0.3 mol% with respect to the lithium composite oxide after heat-treating the precursor to obtain the lithium composite oxide.

[0198] As a result of ICP-OES analysis of the obtained positive electrode active material, the composition of the positive electrode active material was Li 1.05 Ni 0.79 Co 0.09 Mn0.09 Ti 0.02 It was confirmed to be O2. Furthermore, the weight of the waste positive electrode active material relative to the total weight of the obtained positive electrode active material was the same as in Example 1.

[0199] (6) Examples 6 to 8 The raw material is Li[Ni] with an average particle size of 15 μm. 0.4 Co 0.2 Mn 0.4 ]O2(NCM424), Li[Ni 0.5 Co 0.2 Mn 0.3 ]O2(NCM523) and Li[Ni 0.6 Co 0.2 Mn 0.2 A positive electrode active material was manufactured in the same manner as in Example 1, using waste positive electrode active material with the composition of ]O2(NCM622). In Example 6, the amount of pure water in the slurry was adjusted so that the viscosity of the slurry was 3,000 cp before spray drying, and in Example 8, the amount of pure water in the slurry was adjusted so that the viscosity of the slurry was 20,000 cp before spray drying.

[0200] ICP-OES analysis of the obtained positive electrode active material revealed that the composition of the positive electrode active material was Li 1.05 Ni 0.8 Co 0.1 Mn 0.1 It was confirmed to be O2 (NCM811). Furthermore, the weight of the waste positive electrode active material used as a raw material was calculated relative to the total weight of the positive electrode active material finally obtained, as shown in Table 2 below.

[0201] TIFF0007888562000002.tif39170

[0202] (7) Examples 9 to 12 The raw material is Li[Ni] with an average particle size of 15 μm. 1 / 3 Co 1 / 3 Mn 1 / 3 ]O2(NCM333), Li[Ni 0.4 Co 0.2 Mn 0.4 ]O2(NCM424), Li[Ni0.5 Co 0.2 Mn 0.3 ]O2(NCM523) and Li[Ni 0.6 Co 0.2 Mn 0.2 Using waste cathode active materials with the O2 (NCM622) composition, cathode active materials were prepared in the same manner as in Example 1, except that the molar ratio of Ni, Co, and Mn in the target cathode active material was 88:10:2.

[0203] ICP-OES analysis of the obtained positive electrode active material revealed that the composition of the positive electrode active material was Li 1.05 Ni 0.88 Co 0.1 Mn 0.02 It was confirmed to be O2. Furthermore, the weight of the waste positive electrode active material used as a raw material was calculated relative to the total weight of the positive electrode active material finally obtained, as shown in Table 3 below.

[0204] [Table 2]

[0205] (8) Comparative Example 1 [Ni] synthesized using a known coprecipitation method. 0.8 Co 0.1 Mn 0.1 A cathode active material was prepared using an OH2 precursor.

[0206] ICP-OES analysis of the manufactured positive electrode active material revealed that the composition of the positive electrode active material is Li 1.05 Ni 0.8 Co 0.1 Mn 0.1 It was confirmed to be O2.

[0207] (9) Comparative Example 2 The positive electrode active material was manufactured in the same manner as in Example 1, except that the content of pure water in the slurry was adjusted so that the viscosity of the slurry was 500 cp before spray drying.

[0208] ICP-OES analysis of the obtained positive electrode active material revealed that the composition of the positive electrode active material is Li 1.05 Ni 0.8 Co 0.1 Mn 0.1 It was confirmed to be O2. Furthermore, the weight of the waste positive electrode active material relative to the total weight of the obtained positive electrode active material was the same as in Example 1.

[0209] (10) Comparative Example 3 The positive electrode active material was manufactured in the same manner as in Example 1, except that the content of pure water in the slurry was adjusted so that the viscosity of the slurry was 2,000 cp before spray drying.

[0210] ICP-OES analysis of the obtained positive electrode active material revealed that the composition of the positive electrode active material is Li 1.05 Ni 0.8 Co 0.1 Mn 0.1 It was confirmed to be O2. Furthermore, the weight of the waste positive electrode active material relative to the total weight of the obtained positive electrode active material was the same as in Example 1. A cross-sectional SEM image of the precursor obtained when producing the positive electrode active material according to Comparative Example 3 is shown in Figure 3.

[0211] (10) Comparative Example 4 The positive electrode active material was manufactured in the same manner as in Example 1, except that the waste positive electrode active material was pulverized in a bead mill so that the average particle size was 0.5 μm or less, and then nickel hydroxide and cobalt hydroxide were weighed and added to the slurry.

[0212] ICP-OES analysis of the obtained positive electrode active material revealed that the composition of the positive electrode active material is Li 1.05 Ni 0.8 Co 0.1 Mn 0.1 It was confirmed to be O2. Furthermore, the weight of the waste positive electrode active material relative to the total weight of the obtained positive electrode active material was the same as in Example 1.

[0213] Figure 4 shows a cross-sectional SEM image of the precursor obtained when producing the positive electrode active material according to Comparative Example 4.

[0214] Manufacturing Example 2: Manufacturing of Lithium-ion Rechargeable Batteries 92 wt% of each of the cathode active materials produced according to Production Example 1, 4 wt% of artificial graphite, and 4 wt% of a PVDF binder were dispersed in 30 g of N-methyl-2-pyrrolidone (NMP) to produce a cathode slurry. The cathode slurry was uniformly coated on an aluminum thin film with a thickness of 15 μm and vacuum dried at 135°C to produce a cathode for a lithium secondary battery.

[0215] A lithium foil was used as a counter electrode with respect to the cathode, a porous polyethylene film (Celgard 2300, thickness: 25 μm) was used as a separator, and a coin cell was produced using an electrolytic solution in which LiPF6 was present at a concentration of 1.15 M in a solvent in which ethylene carbonate and ethyl methyl carbonate were mixed at a volume ratio of 3:7.

[0216] Experimental Example 1. Evaluation of particle properties of positive electrode active material 0.1 g each of the precursor and the lithium composite oxide obtained when producing the cathode active material in Production Example 1 were put into 50 ml of an aqueous sodium hexametaphosphate solution and then dispersed to obtain a dispersion. Next, the average particle diameter and particle size distribution of the precursor and the lithium composite oxide in the dispersion were measured using a laser diffraction scattering particle size distribution measuring device (Cilas PSA 1060) to obtain a cumulative particle size distribution curve based on volume.

[0217] Next, the dispersion was ultrasonically treated at a frequency of 40 kHz for 60 seconds using the ultrasonic treatment unit included in the particle size distribution measuring device, and then D 50 / D 10 The change rate of was measured.

[0218] In the obtained cumulative particle size distribution curve, the volume particle size at 10% cumulative was defined as the 10% cumulative volume particle size D 10 The volume particle size at 50% cumulative was defined as the 50% cumulative volume particle size D 50 The volume particle size at 90% cumulative was defined as the 90% cumulative volume particle size D 90 And. [[ID=​​​50 / D 10 The rate of change was calculated as follows:

[0220] D 50 / D 10 Rate of change (%) = (|D after ultrasonic treatment) 50 / D 10 -D before ultrasonic treatment 50 / D 10 | / D before ultrasonic treatment 50 / D 10 ) × 100

[0221] The measurement results for the particle size distribution of the aforementioned precursor are shown in Tables 4 and 5 below, and the measurement results for the particle size distribution of the aforementioned lithium composite oxide are shown in Tables 6 and 7 below.

[0222] [Table 3]

[0223] [Table 4]

[0224] Referring to the results in Tables 4 and 5 above, [Ni] synthesized using a known coprecipitation method 0.8 Co 0.1 Mn 0.1 When comparing positive electrode active materials produced using waste positive electrode active materials, excluding the precursors of positive electrode active materials produced using OH2 precursors, it can be confirmed that the change in particle size distribution after ultrasonic treatment of the positive electrode active material precursors in Examples 1 to 12 is less than that of the positive electrode active material precursors in Comparative Examples 2 to 4.

[0225] [Table 5]

[0226] [Table 6]

[0227] Referring to the results in Tables 6 and 7 above, [Ni] synthesized using a known coprecipitation method 0.8 Co 0.1 Mn 0.1 With the exception of Comparative Example 1, which is a positive electrode active material produced using an OH2 precursor, when comparing positive electrode active materials produced using waste positive electrode active materials, it can be confirmed that the change in particle size distribution after ultrasonic treatment for the positive electrode active materials (lithium composite oxides) from Examples 1 to 12 is less than that for the positive electrode active materials (lithium composite oxides) from Comparative Examples 2 to 4.

[0228] In particular, the positive electrode active materials (lithium composite oxides) according to Examples 1 to 12 show a similar level of change in particle size distribution as Comparative Example 1, suggesting that sufficient strength and stability can be ensured as positive electrode active materials for lithium secondary batteries.

[0229] Experimental Example 2. Evaluation of the electrochemical properties of lithium secondary batteries. Charge and discharge experiments were conducted on the lithium secondary battery (coin cell) manufactured in Manufacturing Example 2 using an electrochemical analyzer (Toyo, Toscat-3100) at 25°C, with a voltage range of 3.0V to 4.3V and a discharge rate of 0.1C, and the charge and discharge capacities were measured. Furthermore, the same lithium secondary battery underwent 100 charge-discharge cycles at 25°C, within a driving voltage range of 3.0V to 4.3V, under conditions of 0.1C / 0.1C. The ratio of the discharged capacity after 100 cycles to the initial capacity (cycle capacity retention) was then measured.

[0230] The measurement results are shown in Table 8 below.

[0231] [Table 7]

[0232] Referring to the results in Table 8 above, [Ni] synthesized using a known coprecipitation method 0.8 Co 0.1 Mn0.1 When compared with Comparative Example 1, which is a positive electrode active material produced using an OH2 precursor, it can be confirmed that lithium secondary batteries using positive electrode active materials (lithium composite oxides) from Examples 1 to 12, which are produced using waste positive electrode active materials, can also exhibit similar levels of electrochemical properties.

[0233] Experimental Example 3. Evaluation of the stability of the positive electrode active material and lithium secondary battery. (1) Evaluation of the thermal stability of the positive electrode active material To evaluate the thermal stability of the cathode active materials produced by Production Example 1, a thermogravimetric analyzer (TA Instruments, Q20) was used to measure weight loss from 25°C to 350°C at a heating rate of 10°C / min under atmospheric pressure and an Ar atmosphere. The onset temperature at which the weight loss (thermal decomposition) peak appeared for each cathode active material is shown in Table 9 below.

[0234] [Table 8]

[0235] Referring to the results in Table 9 above, it can be confirmed that the onset temperature at which the weight loss (thermal decomposition) peak appears in the positive electrode active materials of Examples 1 to 12, which were manufactured using waste positive electrode active materials, is similar to or even higher than that of the positive electrode active materials of Comparative Examples 1 to 4. Through this, it can be confirmed that the thermal stability of the positive electrode active materials of Examples 1 to 12 is sufficiently ensured.

[0236] (2) Measurement of gas generation amount of lithium secondary battery The lithium secondary battery manufactured according to Manufacturing Example 2 was charged to 4.25V with a constant current of 0.2C, and then stored at 60°C for 14 days. The volume change of the lithium secondary battery due to gas generation within the battery was measured. The volume change measurement results are shown in Table 10 below.

[0237] [Table 9]

[0238] Referring to the results in Table 10 above, [Ni] synthesized using a known coprecipitation method 0.8 Co 0.1 Mn 0.1 Excluding Comparative Example 1, which is a positive electrode active material produced using an OH2 precursor, when comparing positive electrode active materials produced using waste positive electrode active materials, it can be confirmed that the volume change of lithium secondary batteries produced using the positive electrode active materials (lithium composite oxides) according to Examples 1 to 12 is less than that of lithium secondary batteries produced using the positive electrode active materials (lithium composite oxides) according to Comparative Examples 2 to 4.

[0239] In particular, the positive electrode active materials (lithium composite oxides) according to Examples 1 to 12 show a volume change at a similar level to that of Comparative Example 1, suggesting that sufficient stability as a positive electrode active material for lithium secondary batteries can be ensured.

[0240] Although embodiments of the present invention have been described above, a person with ordinary skill in the art can modify and change the present invention in various ways, such as by adding, changing, deleting, or adding components, without departing from the spirit of the invention as described in the claims, and this can also be said to be within the scope of the rights of the present invention.

Claims

1. A positive electrode active material for a lithium secondary battery having a lithium composite oxide containing at least (1) manganese, optionally aluminum; (2) nickel; and (3) cobalt, Of the lithium composite oxides, (1) manganese, optionally aluminum; (2) nickel; and (3) cobalt, 3 wt% or more of the total weight is derived from waste positive electrode active material. The positive electrode active material is subjected to ultrasonic treatment at a frequency of 40 kHz for 60 seconds, and then the lithium composite oxide in the positive electrode active material is D ５０ / D １０ The rate of change is less than 10%. The ratio D50 / D10 of the 50% cumulative volume particle size D50 of the positive electrode active material to the 10% cumulative volume particle size D10 of the positive electrode active material is between 2.0 and 7.

0. The aforementioned lithium composite oxide is a positive electrode active material for lithium secondary batteries, represented by the following chemical formula 2. [Chemical formula 2] Li w Ni 1-(x+y+z) Co x M1 y M2 z O 2 (Here, M1 is Mn, M2 is at least one selected from Mn, B, Ba, Ce, Hf, Ta, Cr, F, Mg, Al, V, Ti, Fe, Zr, Zn, Si, Y, Nb, Ga, Sn, Mo, W, P, Sr, Ge, Nd, Gd, and Cu. M1 and M2 are different elements. 0.5 ≤ w ≤ 1.5, 0 < x ≤ 0.40, 0 < y ≤ 0.40, 0 ≤ z ≤ 0.40, and 1 - (x + y + z) ≥ 0.

79.

2. The positive electrode active material includes primary particles made of the lithium composite oxide and secondary particles formed by aggregation of multiple primary particles. The positive electrode active material for a lithium secondary battery according to claim 1, wherein the average particle size of the secondary particles is 3 μm to 20 μm.

3. The positive electrode active material for a lithium secondary battery according to claim 1, wherein at least a portion of the surface of the lithium composite oxide has a coating layer containing an oxide represented by the following chemical formula 3. [Chemical formula 3] Li ａ A ｂ O ｃ (Here, A is at least one selected from Ni, Mn, Co, Fe, Cu, Nb, Mo, Ti, Al, Cr, Zr, Zn, Na, K, Ca, Mg, Pt, Au, B, P, Eu, Sm, Ce, V, Ba, Ta, Sn, Hf, Gd, and Nd. (0 ≤ a ≤ 10, 0 < b ≤ 8, 2 ≤ c ≤ 13.)

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