Method for manufacturing positive electrode active material, positive electrode active material, positive electrode plate, and non-aqueous electrolyte secondary battery

Abstract

To provide a positive electrode active material capable of reducing degradation of storage properties and a method of producing the positive electrode active material, and a positive electrode plate and a nonaqueous electrolyte secondary battery including the positive electrode active material.SOLUTION: There is provided a method of producing a positive electrode active material, which includes: a preparation step of preparing aggregate particles including a nickel-cobalt-manganese-based compound having a ratio of nickel of 75 mol% or more; a first treatment step of treating a surface of the aggregate particles with a fluorine-based compound at a temperature of 80°C or more; and a second treatment step of treating the surface of the aggregate particles after the first treatment step, with at least one selected from the group consisting of a lithium-containing metal oxide and lithium borate.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a method for producing a positive electrode active material, and further to a positive electrode active material, a positive electrode plate, and a non-aqueous electrolyte secondary battery. [Background technology]

[0002] Patent Document 1 discloses a lithium metal composite oxide composed of secondary particles formed by aggregation of primary particles and single particles existing independently of the secondary particles, and proposes that particle cracking be suppressed by making the particle size of the single particles relatively small. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2020-87879 Summary of the Invention [Problem to be solved by the invention]

[0004] When single particles are used in the positive electrode plate of a non-aqueous electrolyte secondary battery (hereinafter also referred to as a battery), the amount of gas generated when the battery is stored (hereinafter also referred to as a storage gas amount) increases, and the storage characteristics of the battery tend to deteriorate.

[0005] An object of the present disclosure is to provide a positive electrode active material that suppresses deterioration of battery storage characteristics, a method for producing the same, a positive electrode plate including the same, and a nonaqueous electrolyte secondary battery. [Means for solving the problem]

[0006] The present disclosure provides the following method for producing a positive electrode active material, a positive electrode active material, a positive electrode plate including the same, and a nonaqueous electrolyte secondary battery. [1] A method for producing a positive electrode active material, a preparation step of preparing agglomerated particles containing a nickel-cobalt-manganese compound having a nickel ratio of 75 mol % or more; a first treatment step of treating the surfaces of the aggregated particles with a fluorine-based compound at a temperature of 80°C or higher; and a second treatment step in which the surfaces of the aggregated particles after the first treatment step are treated with at least one selected from the group consisting of lithium-containing metal oxides and lithium borate; A method for producing a positive electrode active material, comprising: [2] The method for producing a positive electrode active material according to [1], wherein the fluorine-based compound is a compound containing a perfluoroalkyl group. [3] The method for producing a positive electrode active material according to [1], wherein the lithium-containing metal oxide is at least one selected from the group consisting of lithium tungstate, lithium zirconate, lithium titanate, and lithium aluminate. [4] The method for producing a positive electrode active material according to [1], further comprising a mixing step of mixing the aggregated particles obtained after the second treatment step with single particles containing a nickel-cobalt-manganese compound having a nickel ratio of 70 mol % or more. [5] The method for producing a positive electrode active material according to [4], wherein the mass ratio of the aggregated particles to the single particles is 20:80 to 50:50. [6] After a storage test at 60°C for 60 days, the gas generation volume was 6.0 cm 3 / Ah or less, and the positive electrode active material includes agglomerated particles containing a nickel-cobalt-manganese compound having a nickel ratio of 75 mol % or more. [7] A positive electrode plate comprising the positive electrode active material according to [6]. [8] A non-aqueous electrolyte secondary battery comprising the positive electrode plate according to [7]. [Effects of the Invention]

[0007] The present disclosure provides a positive electrode active material that suppresses deterioration of storage characteristics, a method for producing the same, a positive electrode plate including the same, and a nonaqueous electrolyte secondary battery. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a schematic flowchart of a method for producing a positive electrode active material in this embodiment. [Figure 2]FIG. 2 is a schematic diagram showing an example of a battery according to this embodiment. [Figure 3] FIG. 3 is a schematic diagram showing an example of an electrode body in this embodiment. [Figure 4] FIG. 4 is a conceptual diagram showing the positive electrode plate in this embodiment. [Figure 5] FIG. 5 is a schematic flowchart of a method for manufacturing a positive electrode plate in this embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, an embodiment of the present disclosure (hereinafter may be abbreviated as "the present embodiment") and an example of the present disclosure (hereinafter may be abbreviated as "the present example") will be described. However, the present embodiment and the example do not limit the technical scope of the present disclosure.

[0010] In this specification, elements expressed in the singular include the plural unless otherwise specified. For example, a "particle" can mean not only "one particle" but also "an aggregate of particles (powder, powder, particle group)."

[0011] <Method of manufacturing positive electrode active material> As shown in FIG. 1 , a method for producing a positive electrode active material according to one embodiment of the present disclosure includes a preparation step (A) of preparing aggregated particles containing a nickel-cobalt-manganese compound (hereinafter also referred to as a first NCM compound) having a nickel ratio of 75 mol % or more, a first treatment step (B) of treating the surfaces of the aggregated particles with a fluorine-based compound at a temperature of 80°C or more, and a second treatment step (C) of treating the surfaces of the aggregated particles after the first treatment step with at least one selected from the group consisting of lithium-containing metal oxides and lithium borate.

[0012] Because single particles require higher temperatures during production than agglomerated particles, the cation mixing value tends to be large. To suppress this, the Li / Me ratio is generally set to 1 or greater. This leads to an increase in the alkaline components present on the surface of the single particles, which tends to increase the amount of storage gas due to the alkaline components remaining on the surface of the single particles and deteriorate storage characteristics. This is presumably because one form of alkaline component is LiOH, LiHCO3, and then Li2CO3, resulting in the generation of CO2 gas during storage at high temperatures. In addition, not only decomposition of the alkaline components present on the surface of the positive electrode active material but also decomposition of the electrolyte due to contact between the electrolyte and the positive electrode active material tends to occur easily. In the manufacturing method of the positive electrode active material disclosed herein, by treating the surface of the agglomerated particles with a fluorine-based compound and then performing elemental coating, a barrier layer that suppresses gas generation is formed between the surface of the agglomerated particles and the coating layer. This easily suppresses gas generation due to the alkaline components, and as a result, it is possible to suppress deterioration of storage characteristics. In this specification, storage characteristics are evaluated according to the method described in the Examples section below.

[0013] The aggregated particles prepared in the preparation step (A) may be aggregates of primary particles. The aggregated particles may have any size. The average particle diameters D50, D70, and D30 of the aggregated particles may be, for example, all 1 μm to 40 μm, preferably all 1 μm to 30 μm, and more preferably all 1 μm to 20 μm. The average particle diameters D50, D70, and D30 represent particle diameters at which the cumulative particle volume from the small particle size side in the volume-based particle size distribution is 50%, 70%, and 30%, respectively, of the total particle volume. The average particle diameter can be measured by a laser diffraction / scattering method.

[0014] Primary particles are particles in which grain boundaries cannot be visually identified in SEM images of the particles and which have an average primary particle diameter of less than 0.5 μm. The average primary particle diameter is the distance between the two most distant points on the outline of a primary particle. The average primary particle diameter of primary particles may be, for example, 0.05 μm to 0.2 μm or 0.1 μm to 0.2 μm. When 10 or more primary particles randomly sampled from an SEM image of a single agglomerate particle have an average primary particle diameter of 0.05 μm to 0.2 μm, all of the primary particles contained in the agglomerate are considered to have an average primary particle diameter of 0.05 μm to 0.2 μm. The primary particles may have an average primary particle diameter of, for example, 0.1 μm to 0.2 μm.

[0015] The first NCM compound has a nickel content of 75 mol % or more, preferably 78 mol % or more, and more preferably 81 mol % or more, where the nickel content is the content ratio of nickel to metal elements excluding lithium.

[0016] The first NCM compound preferably contains a nickel-cobalt-manganese composite hydroxide, more preferably a lithium-nickel-cobalt-manganese composite oxide. The nickel-cobalt-manganese composite hydroxide may be obtained by, for example, a coprecipitation method. The nickel-cobalt-manganese composite hydroxide may be, for example, a compound represented by the general formula: Ni x Co y Mn z It may be a compound represented by (OH)2 (wherein x+y+z=1). The lithium nickel cobalt manganese composite oxide may have a molar ratio of lithium to nickel, cobalt, and manganese, Li:(Ni+Co+Mn), of, for example, 1.0 to 1.2:1.0.

[0017] The first NCM compound is, for example, a compound represented by the following formula (1): Li 1-a1 Ni x1 Me 1 1-x1 O2(1) [In formula (1), "a1" satisfies the relationship -0.3≦a1≦0.3. "x1" satisfies the relationship 0.75≦x1≦1.0. "Me 1 " represents at least one selected from the group consisting of Co, Mn, Al, Zr, Ti, V, Cr, Fe, Cu, Zn, Mo, Sn, Ge, Nb, and W. The layered metal oxide may contain one or more first layered metal oxides represented by the following formula:

[0018] For example, the aggregate particles (primary particles) are LiNi 0.75 Co 0.15 Mn 0.1 O2, and LiNi 0.75 Co 0.1 Mn 0.15 O2 and LiNi 0.8 Co 0.1 Mn 0.1 For example, the aggregated particles (primary particles) may contain at least one selected from the group consisting of LiNi 0.75 Co 0.15 Mn 0.1 O2, and LiNi 0.75 Co 0.1 Mn 0.15 O2 and LiNi 0.8 Co 0.1 Mn 0.1 O2.

[0019] When the agglomerated particles contain a lithium-nickel-cobalt-manganese composite oxide, the agglomerated particles can be obtained by, for example, mixing a lithium source such as lithium hydroxide with a nickel-cobalt-manganese composite hydroxide, firing the mixture, wet-pulverizing the mixture using a ball mill or the like, and drying it.

[0020] The fluorine-based compound used to treat the surfaces of the aggregated particles in the first treatment step (B) is not particularly limited in the length of the main chain, and it is sufficient that at least one of the atoms present in the side chain is a fluorine atom. For example, the compound may have a functional group such as an aliphatic hydrocarbon group (e.g., a methyl group, an ethyl group, etc.) or an aromatic hydrocarbon group (e.g., a benzene ring), and at least one of the hydrogen atoms of the functional group may be substituted with fluorine. Examples of fluorine-containing compounds include compounds containing perfluoroalkyl groups. Specific examples thereof include trimethoxysilane (CH 16 O3Si), perfluorohexylethyltriethoxysilane (CF3(CF2)5CH2CH2Si(OEt)3), perfluorohexylethyltrimethoxysilane (CF3(CF2)5CH2CH2Si(OMe)3), perfluorohexylethyltrichlorosilane (CF3(CF2)5CH2CH2SiCl3), CF3(CF2)9CH2CH2Si(OCH3)3, and CF3(CF2)3(C6H4)CH(OH)CH3. As the fluorine-based compound, for example, a surfactant containing fluorine can also be used.

[0021] The temperature at which the surfaces of the agglomerated particles are treated with a fluorine-based compound is 80°C or higher, and from the viewpoint of storage properties, preferably 80°C or higher and 160°C or lower. The method for treating the surfaces of the agglomerated particles with a fluorine-based compound may be any method that allows the fluorine-based compound to be present on part of the surfaces of the agglomerated particles, and examples of such methods include coating treatments such as mechanochemical treatment. Mechanochemical treatment can be, for example, a dry treatment in which a base material (aggregated particles) and coating material particles (fluorine-based compound) are rotated at high speed in a container together with media (e.g., zirconia beads), and the coating material particles are crushed and bonded to the surface of the base material to coat them.

[0022] The lithium-containing metal oxide used in the second treatment step (C) may include at least one selected from the group consisting of lithium tungstate (Li2WO4), lithium zirconate (Li2ZrO3), lithium titanate (Li2TiO3), and lithium aluminate (LiAlO2). From the viewpoint of storage properties, lithium borate is preferably used.

[0023] In the second treatment step (C), the surface of the agglomerated particles after the first treatment step is treated with at least one selected from the group consisting of lithium-containing metal oxides and lithium borate. For example, the agglomerated particles are heat-treated using at least one selected from the group consisting of metal oxides and boric acid and a lithium salt. For example, the agglomerated particles after the first treatment step are mixed with at least one selected from the group consisting of metal oxides and boric acid and a lithium salt, and the mixture is heated at a temperature of 200°C to 400°C for 1 hour. Examples of lithium salts include lithium carbonate. Examples of metal oxides include tungstic acid (H3BO3), zirconate (H4O4Zr), titanate (H4TiO4), and aluminate (HAlO2). The heat treatment time is preferably 10 to 60 minutes from the viewpoint of storage properties.

[0024] The method for producing a positive electrode active material may further include a mixing step in which the aggregated particles obtained after the second treatment step are mixed with single particles containing an NCM compound having a nickel ratio of 70 mol% or more (hereinafter also referred to as a second NCM compound). The single particles may have any size. The average particle diameter D50 of the single particles may be, for example, 1 μm to 20 μm, preferably 1 μm to 10 μm, and more preferably 1 μm to 5 μm.

[0025] The nickel content in the second NCM compound is 70 mol % or more, preferably 73 mol % or more, and more preferably 76 mol % or more.

[0026] The second NCM compound preferably contains a nickel-cobalt-manganese composite hydroxide, more preferably a lithium-nickel-cobalt-manganese composite oxide. The nickel-cobalt-manganese composite hydroxide may be obtained by, for example, a coprecipitation method. The nickel-cobalt-manganese composite hydroxide may be, for example, a compound represented by the general formula: Ni x Co y Mn z It may be a compound represented by (OH)2 (wherein x+y+z=1). The lithium nickel cobalt manganese composite oxide may have a molar ratio of lithium to nickel, cobalt, and manganese, Li:(Ni+Co+Mn), of, for example, 1.0 to 1.2:1.0.

[0027] The single particle may be, for example, a particle represented by the following formula (2): Li 1-a2 Ni x2 Me 2 1-x2 O2(2) [In formula (2), "a2" satisfies the relationship -0.3≦a2≦0.3. "x2" satisfies the relationship 0.7≦x2<1.0. "Me 2 " represents at least one selected from the group consisting of Co, Mn, Al, Zr, Ti, V, Cr, Fe, Cu, Zn, Mo, Sn, Ge, Nb, and W. The second layered metal oxide may contain one or more types of second layered metal oxides represented by the following formula:

[0028] For example, a single particle is LiNi 0.7 Co 0.2 Mn 0.1 O2, and LiNi 0.7 Co 0.1 Mn 0.2 O2 and LiNi 0.8 Co 0.1 Mn 0.1 For example, the single particle may contain substantially at least one selected from the group consisting of LiNi 0.7 Co 0.2 Mn 0.1 O2, and LiNi 0.7 Co 0.1Mn 0.2 O2 and LiNi 0.8 Co 0.1 Mn 0.1 O2.

[0029] When the single particles contain a lithium-nickel-cobalt-manganese composite oxide, the single particles can be obtained by, for example, mixing a lithium source such as lithium hydroxide with the nickel-cobalt-manganese composite hydroxide, firing the mixture, wet-pulverizing the mixture using a ball mill or the like, and drying the mixture. The single particles may be surface-treated.

[0030] In the mixing step, the single particles can be mixed so that the mass ratio of agglomerated particles to single particles is, for example, 20:80 to 50:50, and preferably 30:70 to 50:50. When the positive electrode active material contains single particles and agglomerated particles in a mass ratio within the above range, particle cracking tends to be easily suppressed. A positive electrode active material layer formed from a positive electrode active material containing single particles and agglomerated particles in a mass ratio within the above range has a density of 3.7 g / cm. 3 Even if the content is more than this, particle cracking tends to be easily suppressed.

[0031] <Cathode active material> The positive electrode active material according to another embodiment of the present disclosure has a gas generation rate of 6.0 cm after a storage test at a temperature of 60° C. for a storage period of 60 days. 3 The cathode active material of the present disclosure includes agglomerated particles containing an NCM compound having a nickel ratio of 75 mol% or more and a capacity of 1 / Ah or less. By including the agglomerated particles, the cathode active material of the present disclosure tends to suppress storage gas generation and to easily suppress deterioration of storage characteristics. The agglomerated particles can be agglomerated particles obtained by the above-described method for producing a cathode active material. The above-described descriptions of the agglomerated particles and the first NCM compound in the method for producing a cathode active material apply to the agglomerated particles and the NCM compound having a nickel ratio of 75 mol% or more, respectively. The amount of gas generated after a storage test at 60°C for 60 days is measured by the method described in the Examples section below.

[0032] The positive electrode active material may further include single particles containing an NCM compound having a nickel ratio of 70 mol% or more. The same explanations regarding the single particles and the second NCM compound in the method for producing a positive electrode active material as described above apply to the single particles and the NCM compound having a nickel ratio of 70 mol% or more (hereinafter also referred to as the second NCM compound). The mass ratio of the agglomerated particles to the single particles in the positive electrode active material may be, for example, 20:80 to 50:50, and preferably 30:70 to 50:50. By ensuring that the mass ratio of the single particles to the agglomerated particles in the positive electrode active material is within the above range, particle cracking tends to be more easily suppressed.

[0033] <Nonaqueous electrolyte secondary battery> Fig. 2 is a schematic diagram showing an example of a nonaqueous electrolyte secondary battery according to this embodiment. The battery 100 shown in Fig. 2 may be a lithium ion battery such as a main power source or a power source for power assist of an electric vehicle.

[0034] The battery 100 includes an exterior housing 90. The exterior housing 90 houses an electrode assembly 50 and an electrolyte (not shown). The electrode assembly 50 is connected to a positive terminal 91 by a positive current collecting member 81. The electrode assembly 50 is connected to a negative terminal 92 by a negative current collecting member 82. FIG. 3 is a schematic diagram showing an example of an electrode assembly in this embodiment. The electrode assembly 50 is a wound type. The electrode assembly 50 includes a positive electrode plate 20, a separator 40, and a negative electrode plate 30. That is, the battery 100 includes the positive electrode plate 20. The positive electrode plate 20 includes a positive electrode active material layer 22 and a positive electrode substrate 21. The negative electrode plate 30 includes a negative electrode active material layer 32 and a negative electrode substrate 31.

[0035] <Positive electrode> As shown in FIG. 4, a positive electrode plate 20 may have a positive electrode active material layer 22 formed directly or indirectly on one or both sides of a positive electrode substrate 21. The positive electrode substrate 21 may be a conductive sheet made of, for example, an Al alloy foil, a pure Al foil, or the like. The positive electrode active material constituting the positive electrode active material layer 22 includes agglomerated particles 12. As shown in FIG. 4, the positive electrode active material may include single particles 11. The positive electrode active material can be produced by the above-mentioned method for producing a positive electrode active material. The positive electrode active material layer 22 may further include a conductive material, a binder, and the like.

[0036] The positive electrode active material layer 22 may have a thickness of, for example, 10 μm or more and 200 μm or less. The positive electrode active material layer 22 may have a high density. The density of the positive electrode active material layer 22 is, for example, 3.65 g / cm. 3 may be 3.7 g / cm or more, 3 or more than 3.8g / cm 3 The positive electrode active material layer 22 may have a density of, for example, 4.0 g / cm 3 It may have the following densities:

[0037] <Manufacturing method of positive electrode plate> The manufacturing method of the positive electrode plate 20 in this embodiment includes (A) preparing a positive electrode slurry, (B) applying the positive electrode slurry, and (C) rolling the positive electrode slurry, as shown in FIG. 5. In (A) preparing the positive electrode slurry, a positive electrode slurry containing the positive electrode active material manufactured by the manufacturing method of the positive electrode active material described above is prepared. The positive electrode slurry is prepared by dispersing the positive electrode active material in a dispersion medium. The dispersion medium may be an organic solvent, such as N-methyl-2-pyrrolidone (NMP), tetrahydrofuran (THF), dimethylformamide (DMF), methyl ethyl ketone (MEK), or dimethyl sulfoxide (DMSO). The positive electrode slurry may contain a conductive material and a binder. Examples of the conductive material include carbon nanotubes, carbon black such as acetylene black (AB), and other carbon materials (e.g., graphite). Examples of binders include polyvinylidene fluoride (PVdF), polytetrafluoroethylene (PTFE), polyimide (PI), polyamide (PA), polyamideimide (PAI), butadiene rubber (BR), styrene butadiene rubber (SBR), nitrile-butadiene rubber (NBR), styrene-ethylene-butylene-styrene block copolymer (SEBS), carboxymethyl cellulose (CMC), or combinations thereof. The slurry may have a solids concentration of, for example, 40% to 80%. Any stirring, mixing, or dispersing device may be used for mixing.

[0038] In coating (B), the positive electrode slurry is coated on the surface of the positive electrode substrate 21 to form the positive electrode active material layer 22. In rolling (C), the positive electrode active material layer 22 and the positive electrode substrate 21 are rolled together to produce the positive electrode plate 20. A raw sheet of the positive electrode plate 20 is produced by rolling. The raw sheet can be cut to a predetermined planar size according to the specifications of the battery 100. [Example]

[0039] The present invention will be described in more detail below with reference to examples. In the examples, "%" and "parts" are by mass % and mass parts unless otherwise specified.

[0040] Example 1 [Preparation of aggregated particles] Obtained by coprecipitation, the composition is Ni 0.83 Co 0.05 Mn 0.12 A nickel-cobalt-manganese composite hydroxide (OH)2 was calcined with lithium hydroxide in an oxygen atmosphere at 800°C for 10 hours and then crushed to obtain agglomerated particles of lithium composite oxide (preparation step). 0.05 wt% of a trimethoxysilane solvent having a fluorine-containing perfluoroalkyl group (hereinafter also referred to as trimethoxysilane solvent) was added to the agglomerated particles and mixed with φ2 mm zirconia balls using a P5 planetary mill manufactured by Filitch. The temperature after 30 minutes of mixing was 80°C (first treatment step). Next, 0.6 wt% of boric acid and an equal molar amount of lithium carbonate were added to the obtained dispersed agglomerated particles of lithium composite oxide, followed by heat treatment at 300°C to obtain an active material (first composite oxide) with an agglomerated structure coated with lithium borate (second treatment step). The particle size distribution of the first composite oxide was D50 12 μm, D70 14 μm, and D30 10 μm. The cross section of the first composite oxide after the CP processing was observed by SEM, and the average primary particle size of the first composite oxide was found to be 0.13 μm.

[0041] <Example 2 and Comparative Example 2> Aggregated particles of Example 2 and Comparative Example 2 were prepared in the same manner as in Example 1, except that the treatment temperatures shown in Table 1 were used in the first treatment step instead of the treatment temperature in Example 1. Example 3 The aggregated particles of Example 3 were prepared in the same manner as in Example 1, except that the fluorine-based compounds shown in Table 1 were used instead of the fluorine-based compounds used in Example 1, and that the treatment temperature in the first treatment step in Example 1 was changed to the treatment temperature shown in Table 1. <Examples 4 to 6> The aggregated particles of Examples 4 to 6 were prepared in the same manner as Example 1, except that the fluorine-based compound used in Example 1 was replaced with the fluorine-based compound shown in Table 1, the treatment temperature of the first treatment step in Example 1 was replaced with the treatment temperature shown in Table 1, and tungstic acid, titanic acid, and zirconic acid were used in Examples 4 to 6 instead of boric acid in Example 1, in the same molar amounts as in Example 1.

[0042] <Comparative Example 1> Aggregated particles were prepared in the same manner as in Example 1, except that after the preparation step in Example 1, the second treatment step was carried out without carrying out the first treatment step.

[0043] [Single particle preparation] Obtained by coprecipitation, the composition is Ni 0.78 Co 0.11 Mn 0.11 Nickel-cobalt-manganese composite hydroxide (OH)2 was calcined at 500°C to obtain nickel-cobalt-manganese composite oxide (Z1). Next, lithium hydroxide and nickel-cobalt-manganese composite oxide (Z1) were mixed so that the molar ratio of Li to the total amount of Ni, Co, and Mn was 1.05:1. The mixture was calcined in an oxygen atmosphere at 900°C for 72 hours, wet-pulverized in a ball mill, dried, and then formed into a single particle structure. This was then heat-treated again in an oxygen atmosphere at 750°C for 10 hours to obtain a lithium composite oxide (second composite oxide) with a single particle structure. Measurement of the particle size distribution of the second composite oxide revealed a particle diameter (D50) of 3.6 μm. Observation of its structure using an SEM revealed that the second composite oxide was composed of particles with a nearly single particle structure, with particle diameters of 2.5 to 3.8 μm.

[0044] [Preparation of positive electrode plate] A 1:1 mixture of the aggregated particles obtained in the Examples and Comparative Examples and the above-mentioned single particles was further mixed with acetylene black and polyvinylidene fluoride (PVdF) to a solids mass ratio of 96.3:2.5:1.2, and an appropriate amount of N-methyl-2-pyrrolidone (NMP) was added, followed by kneading to prepare a positive electrode composite slurry. The positive electrode composite slurry was applied to both sides of a 1N30 aluminum foil core having a thickness of 13 μm, the coating film was dried, and then the coating film was rolled using a rolling mill until the composite density of the coating film reached 3.7 g / cm. 3 The resultant was compressed to a predetermined electrode size, and cut to obtain a positive electrode plate in which a positive electrode composite layer was formed on both sides of the positive electrode core.

[0045] [Fabrication and evaluation of small lithium-ion batteries] The positive electrode plate and carbon anode were combined with a separator, placed in a laminated outer bag, and sealed after adding electrolyte to create a small laminated battery. The battery size was 8 layers of electrodes stacked together to obtain a charge capacity of 600mAh.

[0046] [Evaluation of storage characteristics] The fabricated battery was charged and then stored in a thermostatic chamber at 60° C. for 60 days, after which the amount of gas generated was measured. The results are shown in Table 1.

[0047] [Table 1]

[0048] As shown in Table 1, in Examples 1 to 6, the DTG peak values ​​after the storage test at a temperature of 60°C for a storage period of 60 days were lower than those in Comparative Examples 1 and 2. It is clear that the present disclosure enables the production of a positive electrode active material with excellent storage characteristics. [Explanation of symbols]

[0049] 11 single particle, 12 agglomerated particle, 20 positive electrode plate, 21 positive electrode substrate, 22 positive electrode active material layer, 30 negative electrode plate, 31 negative electrode substrate, 32 negative electrode active material layer, 40 separator, 50 electrode body, 81 positive electrode current collecting member, 82 negative electrode current collecting member, 90 exterior body, 91 positive electrode terminal, 92 negative electrode terminal, 100 battery.

Claims

1. A method for producing a positive electrode active material, a preparation step of preparing agglomerated particles containing a nickel-cobalt-manganese compound having a nickel ratio of 75 mol % or more; a first treatment step of treating the surfaces of the aggregated particles with a fluorine-based compound at a temperature of 80° C. or higher; and a second treatment step in which the surfaces of the aggregated particles after the first treatment step are treated with at least one selected from the group consisting of lithium-containing metal oxides and lithium borate; Including, The method for producing a positive electrode active material, wherein the fluorine-based compound is a compound containing a perfluoroalkyl group.

2. 2. The method for producing a positive electrode active material according to claim 1, wherein the lithium-containing metal oxide is at least one selected from the group consisting of lithium tungstate, lithium zirconate, lithium titanate, and lithium aluminate.

3. 2. The method for producing a positive electrode active material according to claim 1, further comprising a mixing step of mixing the aggregated particles obtained after the second treatment step with single particles containing a nickel-cobalt-manganese-based compound having a nickel ratio of 70 mol % or more.

4. 4. The method for producing a positive electrode active material according to claim 3, wherein a mass ratio of the aggregated particles to the single particles is 20:80 to 50:

50.

5. After a storage test at 60°C for 60 days, the amount of gas generated was 6.0 cm ３ / Ah or less, and the nickel ratio is 75 mol% or more, and the agglomerated particles contain a nickel-cobalt-manganese compound, the agglomerated particles have a fluorine-based compound present on a portion of the surface of the agglomerated particles, and at least one selected from the group consisting of a lithium-containing metal oxide and lithium borate present on the surface of the agglomerated particles on which the fluorine-based compound is present, The fluorine-based compound is a compound containing a perfluoroalkyl group, and is a positive electrode active material.

6. A positive electrode plate comprising the positive electrode active material according to claim 5 .

7. A non-aqueous electrolyte secondary battery comprising the positive electrode plate according to claim 6.

Images