Positive electrode active material for lithium secondary battery, method for producing same, and lithium secondary battery

Abstract

The present invention relates to a positive electrode active material for a lithium secondary battery, which has excellent cycle performance at a high voltage and is capable of reducing impedance, and which is characterized by comprising a mixture of aluminum-containing lithium-cobalt composite oxide particles and inorganic fluoride particles, aluminum is present at least in a solid solution inside the aluminum-containing lithium-cobalt composite oxide particles, and the inorganic fluoride particles are MgF2 and a compound containing Al and F.

Description

Technical Field

[0001] The present invention relates to a positive electrode active material for a lithium secondary battery, a method for manufacturing the same, and a lithium secondary battery using the positive electrode active material for a lithium secondary battery. Background Art

[0002] In recent years, with the rapid development of the miniaturization and cordless of household appliances, lithium ion secondary batteries have been practically used as power sources for small electronic devices such as laptop computers, mobile phones, and video cameras. Since Mizushima et al. reported in 1980 that lithium cobalt oxide is effective as a positive electrode active material for lithium ion secondary batteries, research and development related to lithium-based composite oxides have been actively promoted, and many proposals have been made so far.

[0003] However, as electronic devices become larger and more powerful, it is necessary to further improve various battery performances.

[0004] The present applicant has previously proposed various positive electrode active materials for lithium secondary batteries that can form lithium secondary batteries with excellent cycle performance even at high voltages. For example, in Patent Document 1, a mixture of lithium cobalt composite oxide particles and inorganic fluoride particles is proposed as a positive electrode active material for a lithium secondary battery, and a positive electrode active material for a lithium secondary battery that can form a lithium secondary battery with excellent cycle performance, a high energy capacity retention rate, and a small decrease in the average working voltage is proposed. In addition, for example, in Patent Document 2, a mixture of titanium-containing lithium cobalt composite oxide particles and inorganic fluoride particles is proposed as a positive electrode active material for a lithium secondary battery, and a positive electrode active material for a lithium secondary battery that can form a lithium secondary battery with excellent cycle performance, a small decrease in the average working voltage, a high average working voltage maintained at a high level, and a high energy density retention rate is proposed.

[0005] Prior Art Documents Patent Documents Patent Document 1: Japanese Patent Laid-Open No. 2020-064712 Patent Document 2: Japanese Patent Laid-Open No. 2020-064711 Summary of the Invention

[0006] Problems to be Solved by the Invention However, for the improvement requirements for battery characteristics proposed in recent years, none of the above prior arts can achieve a high level of balance among various battery performances.

[0007] In particular, batteries for electric bicycles, electric vehicles, robots, drones, backup power supplies, etc. are designed to be used at high voltages and high powers.

[0008] Therefore, it is necessary to improve the cycle performance at a temperature of around 25°C and under high voltage, and to reduce the impedance, etc. In addition, in addition to the above battery performance, it is also necessary to improve the cycle performance at a high temperature of around 45 to 60°C and under high voltage.

[0009] Therefore, an object of the present invention is to provide a positive electrode active material for a lithium secondary battery, which has excellent cycle performance under high voltage and can reduce impedance, and an industrially advantageous manufacturing method thereof, and to provide a lithium secondary battery having excellent cycle performance under high voltage and capable of reducing impedance.

[0010] In addition, an object of the present invention is also to provide a positive electrode active material for a lithium secondary battery, which has excellent cycle performance not only under the above battery performance but also at high temperature and under high voltage, an industrially advantageous manufacturing method thereof, and a lithium secondary battery which has excellent cycle performance not only under the above battery performance but also at high temperature and under high voltage.

[0011] Technical solution for solving the problem In view of the above facts, the present inventors have conducted repeated and in-depth studies, and as a result, found that: when a mixture of aluminum-containing lithium cobalt composite oxide particles in which aluminum is solid-solved inside the lithium cobalt composite oxide particles as aluminum-containing lithium cobalt composite oxide particles, MgF2, and inorganic fluoride particles as a compound containing Al and F is used as a positive electrode active material for a lithium secondary battery, a lithium secondary battery having excellent cycle performance under high voltage and having low impedance can be formed, thereby completing the present invention.

[0012] That is, the present invention (1) provides a positive electrode active material for a lithium secondary battery, which is characterized by being composed of a mixture of aluminum-containing lithium cobalt composite oxide particles and inorganic fluoride particles. In the above aluminum-containing lithium cobalt composite oxide particles, aluminum is at least solid-solved inside the aluminum-containing lithium cobalt composite oxide particles, and the inorganic fluoride particles are MgF2 and a compound containing Al and F.

[0013] In addition, the present invention (2) provides a positive electrode active material for a lithium secondary battery according to (1), which is characterized in that the compound containing Al and F is AlF3 and / or LiAlF4.

[0014] In addition, the present invention (3) provides a positive electrode active material for a lithium secondary battery according to (1) or (2), which is characterized in that the Al content of the above aluminum-containing lithium cobalt composite oxide particles is 0.05 to 5.0 mol% in terms of the molar percentage ((Al / Co)×100) of Al relative to the atomic equivalent of Co in the aluminum-containing lithium cobalt composite oxide particles.

[0015] In addition, the present invention (4) provides a positive electrode active material for a lithium secondary battery according to any one of (1) to (3), characterized in that the content of the above inorganic fluoride particles is 0.05 to 5.0 mol% in terms of the molar percentage ((F / Co)×100) of F relative to the atomic equivalent of Co in the aluminum-containing lithium cobalt composite oxide particles.

[0016] In addition, the present invention (5) provides a positive electrode active material for a lithium secondary battery according to any one of (1) to (4), characterized in that the mixing ratio of the above MgF2 and the compound containing Al and F is 0.033 to 33 in terms of the molar ratio of the number of moles of F in the atomic equivalent of MgF2 to the number of moles of F in the atomic equivalent of the compound containing Al and F (molar number of F in atomic equivalent of MgF2 / molar number of F in atomic equivalent of compound containing Al and F).

[0017] In addition, the present invention (6) provides a positive electrode active material for a lithium secondary battery according to any one of (1) to (5), characterized in that the lattice constant of the c-axis is 14.055 to 14.070 Å.

[0018] In addition, the present invention (7) provides a positive electrode active material for a lithium secondary battery according to any one of (1) to (6), characterized in that in the above aluminum-containing lithium cobalt composite oxide particles, as the M element, it contains one or more selected from Ca, Mg, Sr, Zr, Nb, B, and W.

[0019] In addition, the present invention (8) provides a positive electrode active material for a lithium secondary battery, characterized in that the positive electrode active material for a lithium secondary battery is a sintered product of a mixture of aluminum-containing lithium cobalt composite oxide particles and inorganic fluoride particles, wherein in the above aluminum-containing lithium cobalt composite oxide particles, aluminum is at least solid-soluted inside the aluminum-containing lithium cobalt composite oxide particles, and the above inorganic fluoride particles are MgF2 and AlF3.

[0020] In addition, the present invention (9) provides a positive electrode active material for a lithium secondary battery according to (8) above, characterized in that the above aluminum-containing lithium cobalt composite oxide particles are a sintered product of a mixture of a lithium compound, a cobalt compound, and an aluminum compound.

[0021] In addition, the present invention (10) provides a positive electrode active material for a lithium secondary battery according to (8) or (9) above, characterized in that the Al content of the above aluminum-containing lithium cobalt composite oxide particles is 0.05 to 5.0 mol% in terms of the molar percentage ((Al / Co)×100) of Al relative to the atomic equivalent of Co in the aluminum-containing lithium cobalt composite oxide particles.

[0022] In addition, the present invention (11) provides a positive electrode active material for a lithium secondary battery according to any one of (8) to (10), characterized in that the mixing amount of the inorganic fluoride particles in the mixture of the aluminum-containing lithium cobalt composite oxide particles and the inorganic fluoride particles is 0.05 to 5.0 mol% in terms of the molar percentage ((F / Co)×100) of F relative to the atomic equivalent of Co in the aluminum-containing lithium cobalt composite oxide particles.

[0023] In addition, the present invention (12) provides a positive electrode active material for a lithium secondary battery according to any one of (8) to (11), characterized in that the mixing ratio of MgF2 to AlF3 in the mixture of the aluminum-containing lithium cobalt composite oxide particles and the inorganic fluoride particles is 0.05 to 50 in terms of the molar ratio (MgF2 / AlF3).

[0024] In addition, the present invention (13) provides a positive electrode active material for a lithium secondary battery according to any one of (8) to (12), characterized in that the lattice constant of the c-axis is 14.055 to 14.070 Å.

[0025] In addition, the present invention (14) provides a positive electrode active material for a lithium secondary battery according to any one of (8) to (13), characterized in that in the aluminum-containing lithium cobalt composite oxide particles, as the M element, one or more selected from Ca, Mg, Sr, Zr, Nb, B, and W are contained.

[0026] In addition, the present invention (15) provides a method for manufacturing a positive electrode active material for a lithium secondary battery, characterized by having a first mixing step of mixing a lithium compound, a cobalt compound, and an aluminum compound as raw materials to obtain a first mixture; a first sintering step of sintering the first mixture to obtain, as a first sintered product, aluminum-containing lithium cobalt composite oxide particles in which aluminum is at least solid-solved inside the particles; a second mixing step of mixing the first sintered product obtained in the first sintering step with inorganic fluoride particles to obtain a second mixture; and a second sintering step of sintering the second mixture to obtain, as a second sintered product, a positive electrode active material for a lithium secondary battery, wherein the inorganic fluoride particles are MgF2 and AlF3.

[0027] In addition, the present invention (16) provides a method for manufacturing a positive electrode active material for a lithium secondary battery as described in (15), characterized in that, in the above first mixing step, the aluminum compound is mixed until the molar percentage of Al relative to the atomic equivalent of Co in the above first mixture ((Al / Co) × 100) is 0.05 to 5.0 mol%.

[0028] In addition, the present invention (17) provides a method for manufacturing a positive electrode active material for a lithium secondary battery as described in (15) or (16), characterized in that The above first sintered product contains, as the M element, one or more selected from Ca, Mg, Sr, Zr, Nb, B, and W.

[0029] In addition, the present invention (18) provides a method for manufacturing a positive electrode active material for a lithium secondary battery as described in any one of (15) to (17), characterized in that, in the above first sintering step, the sintering temperature is 800 to 1150 °C.

[0030] In addition, the present invention (19) provides a method for manufacturing a positive electrode active material for a lithium secondary battery as described in any one of (15) to (18), characterized in that, in the above second mixing step, the inorganic fluoride particles are mixed until the molar percentage of F relative to the atomic equivalent of Co in the above second mixture ((F / C) × 100) is 0.05 to 2.0 mol%.

[0031] In addition, the present invention (20) provides a method for manufacturing a positive electrode active material for a lithium secondary battery as described in any one of (15) to (19), characterized in that the lattice constant of the c-axis of the positive electrode active material for a lithium secondary battery as the above second sintered product is 14.055 to 14.070 Å.

[0032] In addition, the present invention (21) provides a lithium secondary battery, characterized in that, as the positive electrode active material, the positive electrode active material for a lithium secondary battery as described in any one of (1) to (14) is used.

[0033] Advantages of the Invention According to the present invention, it is possible to provide a positive electrode active material for a lithium secondary battery that has excellent cycle performance at high voltages and can reduce impedance when used as a positive electrode active material for a lithium secondary battery, an industrially advantageous manufacturing method thereof, and a lithium secondary battery that has excellent cycle performance at high voltages and can reduce impedance.

[0034] In addition, according to the present invention, it is also possible to provide a positive electrode active material for a lithium secondary battery that has excellent cycle performance not only at high temperatures but also at high voltages in addition to the above-described battery performance, an industrially advantageous manufacturing method thereof, and a lithium secondary battery that has excellent cycle performance not only at high temperatures but also at high voltages in addition to the above-described battery performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 X-ray diffraction pattern of the aluminum-containing lithium cobalt composite oxide obtained in the first sintering process of Example 1. DETAILED DESCRIPTION OF THE INVENTION

[0036] Hereinafter, the present invention will be described based on preferred embodiments.

[0037] The positive electrode active material for a lithium secondary battery according to the first embodiment of the present invention (hereinafter also simply referred to as the positive electrode active material (1) for a lithium secondary battery of the present invention) is characterized by being composed of a mixture of aluminum-containing lithium cobalt composite oxide particles (1) and inorganic fluoride particles (1). In the above aluminum-containing lithium cobalt composite oxide particles (1), aluminum is at least dissolved in the interior of the aluminum-containing lithium cobalt composite oxide particles, and the inorganic fluoride particles are MgF2 and a compound containing Al and F.

[0038] It should be noted that the aluminum-containing lithium cobalt composite oxide particles of the positive electrode active material (1) for a lithium secondary battery of the present invention are also denoted as aluminum-containing lithium cobalt composite oxide particles (1).

[0039] The positive electrode active material (1) for a lithium secondary battery of the present invention is basically composed of a mixture of aluminum-containing lithium cobalt composite oxide particles (1) and inorganic fluoride particles.

[0040] The aluminum-containing lithium cobalt composite oxide that forms the aluminum-containing lithium cobalt composite oxide particles (1) in the positive electrode active material (1) for a lithium secondary battery of the present invention is a composite oxide containing at least lithium, cobalt, and aluminum, and is a composite oxide in which aluminum is contained as an additive element in the lithium cobalt composite oxide. In the aluminum-containing lithium cobalt composite oxide particles (1) of the positive electrode active material (1) for a lithium secondary battery of the present invention, Al is at least dissolved in the interior of the aluminum-containing lithium cobalt composite oxide particles. Moreover, in the aluminum-containing lithium cobalt composite oxide particles (1) of the positive electrode active material (1) for a lithium secondary battery of the present invention, Al is at least dissolved in the interior of the aluminum-containing lithium cobalt composite oxide particles (1), which enables the crystal structure of the lithium cobalt composite oxide particles themselves to be stable even at high voltages. Therefore, not only can the decrease in charge-discharge capacity be suppressed, but also the cycle performance at high voltages can be improved. More preferably, the cycle performance at high voltages and high temperatures is improved.

[0041] In the aluminum-containing lithium cobalt composite oxide particles (1) of the positive electrode active material (1) for a lithium secondary battery according to the present invention, Al is solid-soluted inside the aluminum-containing lithium cobalt composite oxide particles (1), which means that the particles are single-phase aluminum-containing lithium cobalt composite oxide particles in which diffraction peaks derived from the raw material aluminum compound and / or Al2O3 are substantially undetectable when X-ray diffraction analysis is performed on the aluminum-containing lithium cobalt composite oxide particles (1) using CuKα rays as the radiation source.

[0042] It should be noted that the fact that diffraction peaks derived from the raw material aluminum compound and Al2O3 are substantially undetectable means that the diffraction peaks derived from the aluminum compound and Al2O3 are below the detection limit of the analysis apparatus.

[0043] In addition, as described later, whether Al is solid-soluted inside the aluminum-containing lithium cobalt composite oxide particles (1) can be inferred from the fact that the lattice constant of the c-axis of the lithium cobalt composite oxide (1) containing Al solid-soluted inside the particles is increased compared to pure lithium cobalt composite oxide particles in which Al is not solid-soluted inside the particles.

[0044] In the aluminum-containing lithium cobalt composite oxide (1) of the positive electrode active material (1) for a lithium secondary battery according to the present invention, Al may exist only inside the composite oxide particles, or may exist both inside and on the surface of the composite oxide particles. In the present invention, Al may exist inside the composite oxide particles or on the surface of the composite oxide particles. Moreover, in the positive electrode active material (1) for a lithium secondary battery according to the present invention, from the viewpoint of stabilizing the composite oxide structure, it is preferable that Al is at least solid-soluted inside the aluminum-containing lithium cobalt composite oxide particles (1). It should be noted that Al being at least solid-soluted inside the composite oxide particles means the case where Al exists only inside the particles and the case where it exists both inside and on the surface of the particles.

[0045] In the aluminum-containing lithium cobalt composite oxide particles (1) of the positive electrode active material (1) for a lithium secondary battery according to the present invention, the molar ratio (Li / Co) of the atomic equivalent of Li to Co is preferably 0.90 to 1.20, particularly preferably 0.95 to 1.15. Since the molar ratio (Li / Co) of Li to Co in the aluminum-containing lithium cobalt composite oxide particles (1) is within the above range, the unit volume capacity of the positive electrode active material for a lithium secondary battery can be increased.

[0046] In the aluminum-containing lithium cobalt composite oxide particles (1) of the positive electrode active material (1) for a lithium secondary battery of the present invention, the molar % ((Al / Co)×100) of Al relative to the atomic equivalent of Co is preferably 0.05 to 5.0 mol%, particularly preferably 0.5 to 2.0 mol%. By making the molar % ((Al / Co)×100) of Al relative to the atomic equivalent of Co in the aluminum-containing lithium cobalt composite oxide particles (1) within the above range, it is possible not only to suppress the decrease in the charge-discharge capacity of the positive electrode active material for a lithium secondary battery, but also to improve the cycle performance at high voltage, the cycle performance at high voltage and high temperature, and the high-temperature storage performance.

[0047] The aluminum-containing lithium cobalt-based composite oxide particles (1) of the positive electrode active material (1) for a lithium secondary battery of the present invention contain Al as an essential additive element of the lithium cobalt composite oxide, but for the purpose of improving performance or physical properties, an M element may be contained as needed. The M element is one or more metal elements selected from Ca, Mg, Sr, Zr, Nb, B, and W.

[0048] To further improve battery performance, the aluminum-containing lithium cobalt composite oxide particles (1) of the positive electrode active material (1) for a lithium secondary battery of the present invention preferably contain at least one of Ca and Sr as the M element, and particularly preferably contain at least one of Ca and Sr and one or more selected from Mg, Zr, Nb, B, and W. In addition, the aluminum-containing lithium cobalt composite oxide particles (1) of the positive electrode active material (1) for a lithium secondary battery of the present invention preferably contain at least one or more selected from Ca, Mg, Sr, and Zr as the M element. Moreover, the aluminum-containing lithium cobalt composite oxide particles (1) of the positive electrode active material (1) for a lithium secondary battery of the present invention preferably contain Mg, Sr, and Zr as the M element.

[0049] When the aluminum-containing lithium cobalt-based composite oxide particles (1) of the positive electrode active material (1) for a lithium secondary battery of the present invention contain an M element, the molar % ((M / Co)×100) of the M element relative to the atomic equivalent of Co atoms in the aluminum-containing lithium cobalt composite oxide particles (1) is preferably 0.01 to 2.0 mol%, particularly preferably 0.05 to 1.0 mol%. When the aluminum-containing lithium cobalt-based composite oxide particles (1) contain an M element, by making the molar % ((M / Co)×100) of the M element relative to Co in the aluminum-containing lithium cobalt-based composite oxide particles (1) within the above range, it is possible to improve battery performance without sacrificing the charge-discharge capacity of the positive electrode active material for a lithium secondary battery. It should be noted that when the aluminum-containing lithium cobalt-based composite oxide contains two or more M elements, the molar number of the M element of the atomic equivalent used as the basis for calculating the above molar % is the total value of the molar numbers of the respective M elements.

[0050] Element M can be present inside the particles of the aluminum-containing lithium cobalt composite oxide particles (1), or can also be present on the surface of the aluminum-containing lithium cobalt composite oxide particles (1), or both inside and on the surface of the aluminum-containing lithium cobalt composite oxide particles (1).

[0051] When element M is present on the surface of the aluminum-containing lithium cobalt composite oxide particles (1), element M can exist in the form of oxides, composite oxides, sulfates, phosphates, etc.

[0052] The average particle size of the aluminum-containing lithium cobalt composite oxide particles (1) of the positive electrode active material (1) for a lithium secondary battery of the present invention is the particle size (D50) at which the volume accumulation is 50% in the particle size distribution measured by the laser diffraction / scattering method, and is preferably 0.5 to 30 μm, particularly preferably 3 to 25 μm. In addition, the BET specific surface area of the aluminum-containing lithium cobalt composite oxide particles (1) is preferably 0.05 to 5.0 m 2 / g, particularly preferably 0.15 to 1.0 m 2 / g. By making the average particle size or BET specific surface area of the aluminum-containing lithium cobalt composite oxide particles (1) within the above ranges, it is possible to facilitate the preparation and coating of the positive electrode mixture, and further obtain an electrode with high packing density.

[0053] The combined use of MgF2 and a compound containing Al and F in the inorganic fluoride particles of the positive electrode active material (1) for a lithium secondary battery of the present invention is also one of the features of the present invention.

[0054] It should be noted that hereinafter, MgF2 and a compound containing Al and F are collectively referred to as "inorganic fluoride" or "inorganic fluoride particles". As a compound containing Al and F, AlF3 and / or LiAlF4 can be cited.

[0055] In the positive electrode active material (1) for a lithium secondary battery of the present invention, the content of the inorganic fluoride particles is preferably 0.05 to 5.0 mol%, particularly preferably 0.1 to 2.0 mol%, in terms of the molar percentage ((F / Co)×100) of F relative to the atomic equivalent of Co in the aluminum-containing lithium cobalt composite oxide particles (1). By making the molar percentage ((F / Co)×100) of F relative to the atomic equivalent of Co in the aluminum-containing lithium cobalt composite oxide particles (1) within the above ranges, not only can the decrease in the charge-discharge capacity of the positive electrode active material for a lithium secondary battery be suppressed, but also the effect of improving the cycle performance at high voltages can be enhanced, and the impedance of the positive electrode active material for a lithium secondary battery can be reduced.

[0056] The mixing ratio of MgF2 and the compound containing Al and F is 0.033 to 33, preferably 0.1 to 20, and particularly preferably 1 to 10, in terms of the ratio of the number of moles of F in terms of the atomic equivalent of MgF2 to the number of moles of F in terms of the atomic equivalent of the compound containing Al and F (number of moles of F in terms of the atomic equivalent of MgF2 / number of moles of F in terms of the atomic equivalent of the compound containing Al and F). By making the ratio of the number of moles of F in terms of the atomic equivalent of MgF2 to the number of moles of F in terms of the atomic equivalent of the compound containing Al and F (number of moles of F in terms of the atomic equivalent of MgF2 / number of moles of F in terms of the atomic equivalent of the compound containing Al and F) within the above range, it is preferred because of the excellent combination of the initial discharge capacity and impedance.

[0057] The inorganic fluoride particles may be present on the particle surface of the aluminum-containing lithium cobalt composite oxide particles (1), or may be present in a state of being simply mixed with the aluminum-containing lithium cobalt composite oxide particles (1), or may be both. That is, the positive electrode active material for a lithium secondary battery of the present invention may be in a state composed of the aluminum-containing lithium cobalt composite oxide particles (1) and the inorganic fluoride particles present on the aluminum-containing lithium cobalt composite oxide particles (1), or may be a simple mixture of the aluminum-containing lithium cobalt composite oxide particles (1) and the inorganic fluoride particles, or may be a mixture of the two forms. It should be noted that when the inorganic fluoride particles are present on the particle surface of the aluminum-containing lithium cobalt composite oxide particles (1), the form in which the inorganic fluoride particles are partially present on the surface of the aluminum-containing lithium cobalt composite oxide particles (1) is preferred because it does not prevent the desorption of lithium on the surface of the aluminum-containing lithium cobalt composite oxide.

[0058] The average particle diameter of the inorganic fluoride particles, based on the volume-based 50% particle diameter (D50) in the particle size distribution measured by the laser diffraction / scattering method, is preferably 0.01 to 30 μm, and particularly preferably 0.1 to 20 μm. By making the average particle diameter of the inorganic fluoride particles within the above range, no adverse conditions are likely to occur in the kneading process during the preparation of the positive electrode mixture, the coating process of applying the obtained positive electrode mixture to the positive electrode current collector, etc.

[0059] The average particle diameter of the positive electrode active material (1) for a lithium secondary battery of the present invention, based on the volume-based 50% particle diameter (D50) in the particle size distribution measured by the laser diffraction / scattering method, is preferably 0.5 to 30 μm, and particularly preferably 3 to 25 μm. In addition, the BET specific surface area of the positive electrode active material (1) for a lithium secondary battery of the present invention is preferably 0.05 to 5.0 m 2 / g, and particularly preferably 0.15 to 1.0 m 2 / g. By making the average particle size or BET specific surface area of the positive electrode active material (1) for the lithium secondary battery of the present invention within the above ranges, no adverse conditions are likely to occur in the kneading process during the preparation of the positive electrode mixture, the coating process of applying the obtained positive electrode mixture to the positive electrode current collector, etc.

[0060] The inventors of the present invention et al. speculated that Al solid-dissolved in LiCoO2 would affect the crystal structure of pure LiCoO2. That is, the c-axis lattice constant of pure LiCoO2 without Al solid-dissolved inside the particles is 14.050 - 14.055 Å, and the c-axis lattice constant of the positive electrode active material (1) for the lithium secondary battery of the present invention is larger than that of pure LiCoO2. The inventors of the present invention et al. speculated that this is the influence of Al solid-dissolved in the lithium cobalt composite oxide.

[0061] The c-axis lattice constant of the positive electrode active material (1) for the lithium secondary battery of the present invention is preferably 14.055 - 14.070 Å, particularly preferably 14.055 - 14.065 Å. By making the lattice constant of the c-axis within the above ranges, the lattice structure collapse caused by charge and discharge can be reduced, and the cycle performance can be improved.

[0062] The manufacturing method of the positive electrode active material for the lithium secondary battery of the present invention is characterized by having a first mixing step of mixing a lithium compound, a cobalt compound, and an aluminum compound as raw materials to obtain a first mixture; sintering the above first mixture to obtain, as a first sintered product, an aluminum-containing lithium cobalt composite oxide particle (2) in which aluminum is at least solid-dissolved inside the particles in a first sintering step; a second mixing step of mixing the above first sintered product obtained in the first sintering step with inorganic fluoride particles to obtain a second mixture; and a second sintering step of sintering the above second mixture to obtain, as a second sintered product, a positive electrode active material for a lithium secondary battery, where the above inorganic fluoride particles are MgF2 and AlF3.

[0063] It should be noted that in the manufacturing method of the positive electrode active material for the lithium secondary battery of the present invention, the aluminum-containing lithium cobalt composite oxide particles before sintering after being mixed with the inorganic fluoride particles, that is, the raw material aluminum-containing lithium cobalt composite oxide particles when mixed with the inorganic fluoride particles for sintering, are also denoted as aluminum-containing lithium cobalt composite oxide particles (2).

[0064] The first mixing step is, for example, a step of mixing a lithium compound, a cobalt compound, and an aluminum compound to obtain a first mixture containing a lithium compound, a cobalt compound, and an aluminum compound.

[0065] The lithium compound in the first mixing step is not particularly limited as long as it is a lithium compound commonly used as a raw material for manufacturing lithium cobalt composite oxides, and examples thereof include lithium oxides, hydroxides, carbonates, nitrates, sulfates, and organic acid salts.

[0066] The cobalt compound in the first mixing step is not particularly limited as long as it is a cobalt compound commonly used as a raw material for manufacturing lithium cobalt-based composite oxides, and examples thereof include cobalt oxides, hydroxides, carbonates, nitrates, sulfates, and organic acid salts.

[0067] The aluminum compound in the first mixing step is not particularly limited as long as it is an aluminum compound containing aluminum element and used as a raw material for manufacturing lithium cobalt composite oxides, and examples thereof include aluminum oxides, hydroxides, carbonates, nitrates, sulfates, and organic acid salts. Among them, as the aluminum compound, aluminum hydroxide is preferred.

[0068] In the first mixing step, the lithium compound and the cobalt compound are mixed at a mixing ratio such that the molar ratio of Li to Co in the first mixture (Li / Co) of the cobalt compound relative to the lithium compound is preferably 0.90 to 1.20, particularly preferably 0.95 to 1.15, and further preferably 1.03 to 1.06. Since the mixing ratio of the lithium compound and the cobalt compound is within the above range, it is easy to obtain a single phase of aluminum-containing lithium cobalt composite lithium oxide in X-ray diffraction analysis.

[0069] In the first mixing step, the aluminum compound is mixed at a ratio such that the molar percentage of Al relative to Co in the first mixture ((Al / Co)×100) of the aluminum compound is preferably 0.05 to 5.0 mol%, particularly preferably 0.5 to 2.0 mol%. Since the mixing ratio of the aluminum compound is within the above range, it is possible to improve the cycle performance at high voltage, the cycle performance at high voltage and high temperature, and the high-temperature storage performance without impairing the original charge-discharge capacity of the lithium cobalt composite oxide.

[0070] In the first mixing step, for the purpose of improving performance or physical properties, a compound containing M element may be mixed in the first mixture.

[0071] The M element is one or more metal elements selected from Ca, Mg, Sr, Zr, Nb, B, and W. As the compound containing M element, examples thereof include oxides, hydroxides, carbonates, nitrates, and organic acid salts containing M element. As the compound containing M element, a compound containing two or more M elements may be used.

[0072] When mixing a compound containing element M in the first mixing step, the compound containing element M is mixed at a mixing ratio such that the atomic equivalent molar percentage of element M in the first mixture relative to Co atoms ((M / Co)×100) is preferably 0.01 to 2.0 mol%, particularly preferably 0.05 to 1.0 mol%. By making the mixing ratio of the compound containing element M within the above range, battery performance can be improved without sacrificing the charge-discharge capacity of the positive electrode active material for the lithium secondary battery.

[0073] As a method for mixing the lithium compound, cobalt compound, aluminum compound, and the compound containing element M used as needed in the first mixing step, for example, a mixing method using a coffee grinder, ribbon mixer, Henschel mixer, super mixer, Nauta mixer, etc. can be cited.

[0074] The first sintering step is a step of obtaining aluminum-containing lithium cobalt composite oxide particles (2) in which aluminum is solid-dissolved inside the particles as the first sintered product by sintering the first mixture obtained by performing the first mixing step.

[0075] In the first sintering step, the first mixture is sintered so that the sintering temperature during the raw material reaction is 800 to 1150 °C, preferably 850 to 1100 °C. By making the sintering temperature within the above range, the generation of unreacted cobalt oxide or overheated decomposition products of lithium cobalt composite oxide, which are factors reducing the capacity of the aluminum-containing lithium cobalt composite oxide, can be reduced.

[0076] In the first sintering step, the first mixture is sintered so that the sintering time during the raw material reaction is 1 to 30 hours, preferably 5 to 20 hours. In addition, the sintering environment in the first sintering step is preferably an oxidation environment such as air or oxygen.

[0077] The second mixing step is to mix the aluminum-containing lithium cobalt composite oxide particles (2) as the first sintered product with inorganic fluoride particles to obtain a second mixture of the aluminum-containing lithium cobalt composite oxide particles (2) and the inorganic fluoride particles.

[0078] In the second mixing step, inorganic fluoride particles are mixed in an amount such that the molar percentage ((F / Co)×100) of F relative to the atomic equivalent of Co in the aluminum-containing lithium cobalt composite oxide particles (2) of the first sintered product is preferably 0.05 to 5.0 mol%, particularly preferably 0.1 to 2.0 mol%. By setting the mixing amount of the inorganic fluoride particles within the above range, it is possible to improve the effect of improving the cycle performance at high voltages while suppressing a decrease in the charge-discharge capacity of the positive electrode active material for a lithium secondary battery, and it is possible to reduce the impedance of the positive electrode active material for a lithium secondary battery. For example, when unreacted lithium carbonate remains on the surface of the aluminum-containing lithium cobalt composite oxide particles (2) as the first sintered product, carbon dioxide gas will be generated due to decomposition products during the charge-discharge process, making it easy to cause defective conditions or increase the impedance. In the method for manufacturing the positive electrode active material for a lithium secondary battery of the present invention, the inventors believe that by mixing inorganic fluoride particles and sintering, the carbonate radicals react, so that unreacted lithium carbonate can be removed. The inventors infer that this is why the impedance can be reduced.

[0079] The inorganic fluoride particles in the second mixing step are MgF2 and AlF3.

[0080] The mixing ratio of MgF2 is 0.05 to 50, preferably 0.1 to 10, particularly preferably 0.7 to 5, based on the molar ratio (MgF2 / AlF3) relative to AlF3. By setting the mixing ratio (MgF2 / AlF3) of MgF2 relative to AlF3 within the above range, it is preferred because the initial discharge capacity and impedance can be optimized.

[0081] In the second mixing step, as a method for mixing the aluminum-containing lithium cobalt composite oxide particles and the inorganic fluoride particles, for example, a mixing method using a coffee grinder, a ribbon mixer, a Henschel mixer, a super mixer, a Nauta mixer, a ball mill, a bead mill, etc. can be cited.

[0082] The second sintering step is a step of obtaining a positive electrode active material for a lithium secondary battery as a second sintered product by sintering the second mixture obtained in the second mixing step.

[0083] In the second sintering step, the second mixture is sintered so that the sintering temperature during the reaction of the raw materials is 200 to 1100 °C, preferably 500 to 1000 °C, particularly preferably 500 to 700 °C. By setting the sintering temperature within the above range, it is possible to sufficiently remove moisture and it is possible to less likely cause performance degradation such as a decrease in the charge-discharge capacity and a decrease in the cycle performance.

[0084] In the second sintering process, the second mixture is sintered, and the sintering time during the raw material reaction process is 1 to 10 hours, preferably 2 to 7 hours. In addition, the sintering environment in the second sintering process is preferably an oxidation environment such as air or oxygen.

[0085] In the first process and the second process, sintering can be performed multiple times as needed. Moreover, after sintering, the sintered product can be crushed or classified as needed.

[0086] The positive electrode active material for a lithium secondary battery according to the second embodiment of the present invention (hereinafter also simply referred to as the positive electrode active material for a lithium secondary battery (2) of the present invention) is characterized in that it is a sintered product of a mixture of aluminum-containing lithium cobalt composite oxide particles (3) and inorganic fluoride particles. The above-mentioned aluminum-containing lithium cobalt composite oxide particles (3) are characterized in that aluminum is at least solid-solved inside the aluminum-containing lithium cobalt composite oxide particles (3), and the above-mentioned inorganic fluoride particles are MgF2 and AlF3.

[0087] It should be noted that in the positive electrode active material for a lithium secondary battery (2) of the present invention, the aluminum-containing lithium cobalt composite oxide particles as the mixture mixed with the inorganic fluoride particles, that is, the raw material aluminum-containing lithium cobalt composite oxide particles sintered in the presence of the inorganic fluoride particles are also denoted as aluminum-containing lithium cobalt composite oxide particles (3).

[0088] In the aluminum-containing lithium cobalt composite oxide particles (3) of the positive electrode active material for a lithium secondary battery (2) of the present invention, aluminum is at least solid-solved inside the aluminum-containing lithium cobalt composite oxide particles (3). There is no particular limitation on the aluminum-containing lithium cobalt composite oxide particles (3) as long as aluminum is at least solid-solved inside the aluminum-containing lithium cobalt composite oxide particles, but preferably the aluminum-containing lithium cobalt composite oxide particles (2) obtained by performing the first mixing process and the first sintering process of the method for manufacturing the positive electrode active material for a lithium secondary battery of the present invention.

[0089] The inorganic fluoride particles of the positive electrode active material for a lithium secondary battery (2) of the present invention are MgF2 and AlF3.

[0090] Moreover, the positive electrode active material for a lithium secondary battery (2) of the present invention is a sintered product of a mixture of aluminum-containing lithium cobalt composite oxide particles (3) and inorganic fluoride particles. That is, the positive electrode active material for a lithium secondary battery (2) of the present invention is obtained by mixing aluminum-containing lithium cobalt composite oxide particles (3) and inorganic fluoride particles and sintering the resulting mixture.

[0091] In the positive electrode active material (2) for a lithium secondary battery of the present invention, the sintered product of the mixture of aluminum-containing lithium cobalt composite oxide particles (3) and inorganic fluoride particles is the mixture of aluminum-containing lithium cobalt composite oxide particles (3) and inorganic fluoride particles sintered at a sintering temperature of 200 to 1100 °C, preferably 500 to 1000 °C, particularly preferably 500 to 700 °C, for a sintering time of 1 to 10 hours, preferably 2 to 7 hours, in an oxidative environment such as air or oxygen.

[0092] In addition, in the positive electrode active material (2) for a lithium secondary battery of the present invention, by sintering the mixture of aluminum-containing lithium cobalt composite oxide particles (3) and inorganic fluoride particles MgF2 and AlF3, the F of the inorganic fluoride particles in the mixture exists in the form of MgF2 and a compound containing Al and F. That is, the positive electrode active material (2) for a lithium secondary battery of the present invention can also be said to be a mixture of aluminum-containing lithium cobalt composite oxide particles (3) and inorganic fluoride particles, and the inorganic fluoride particles are MgF2 and a compound containing Al and F for a positive electrode active material for a lithium secondary battery. It should be noted that the inventors of the present invention et al. infer that the compound containing Al and F is AlF3 and / or LiAlF4.

[0093] In the aluminum-containing lithium cobalt composite oxide particles (3) of the positive electrode active material (2) for a lithium secondary battery of the present invention, it is obvious that the molar ratio of Li to Co in atomic equivalents (Li / Co) is preferably 0.90 to 1.20, particularly preferably 0.95 to 1.15. By making the molar ratio of Li to Co in atomic equivalents (Li / Co) in the aluminum-containing lithium cobalt composite oxide particles (3) within the above range, the unit volume capacity of the positive electrode active material for a lithium secondary battery can be improved.

[0094] In the aluminum-containing lithium cobalt composite oxide particles (3) of the positive electrode active material (2) for a lithium secondary battery of the present invention, the molar percentage of Al to Co in atomic equivalents ((Al / Co)×100) is preferably 0.05 to 5.0 mol%, particularly preferably 0.5 to 2.0 mol%. By making the molar percentage of Al to Co in atomic equivalents ((Al / Co)×100) in the aluminum-containing lithium cobalt composite oxide particles (3) within the above range, not only can the reduction of the charge-discharge capacity of the positive electrode active material for a lithium secondary battery be suppressed, but also the cycle performance at high voltage, the cycle performance at high voltage and high temperature, and the high temperature storage performance can be improved.

[0095] The aluminum-containing lithium cobalt-based composite oxide particles (3) of the positive electrode active material (2) for a lithium secondary battery according to the present invention contain Al as an essential additive element for the lithium cobalt composite oxide, but may contain an M element as needed for improving performance or physical properties. The M element is one or more metal elements selected from Ca, Mg, Sr, Zr, Nb, B, and W.

[0096] To further improve battery performance, the aluminum-containing lithium cobalt composite oxide particles (3) of the positive electrode active material (2) for a lithium secondary battery according to the present invention preferably contain at least one of Ca and Sr as the M element, and particularly preferably contain at least one of Ca and Sr and one or more selected from Mg, Zr, Nb, B, and W. In addition, the aluminum-containing lithium cobalt composite oxide particles (3) of the positive electrode active material (2) for a lithium secondary battery according to the present invention preferably contain at least one or more selected from Ca, Mg, Sr, and Zr as the M element. Moreover, the aluminum-containing lithium cobalt composite oxide particles (3) of the positive electrode active material (2) for a lithium secondary battery according to the present invention preferably contain Mg, Sr, and Zr as the M element.

[0097] When the aluminum-containing lithium cobalt-based composite oxide particles (3) of the positive electrode active material (2) for a lithium secondary battery according to the present invention contain the M element, the molar percentage ((M / Co)×100) of the M element in the aluminum-containing lithium cobalt composite oxide particles (3) relative to the atomic equivalent of Co atoms is preferably 0.01 to 2.0 mol%, and particularly preferably 0.05 to 1.0 mol%. When the aluminum-containing lithium cobalt-based composite oxide particles (3) contain the M element, by making the molar percentage ((M / Co)×100) of the M element in the aluminum-containing lithium cobalt-based composite oxide particles (3) relative to Co within the above range, the battery performance can be improved without sacrificing the charge-discharge capacity of the positive electrode active material for a lithium secondary battery. It should be noted that when the aluminum-containing lithium cobalt-based composite oxide particles (3) contain two or more M elements, the number of moles of the M element in atomic equivalent as the basis for calculating the above molar percentage refers to the total value of the number of moles of each M element.

[0098] The M element may exist inside the particles of the aluminum-containing lithium cobalt-based composite oxide particles (3), or may exist on the surface of the aluminum-containing lithium cobalt-based composite oxide particles (3), or both inside and on the surface of the aluminum-containing lithium cobalt-based composite oxide particles (3).

[0099] When the M element exists on the surface of the particles of the aluminum-containing lithium cobalt-based composite oxide particles (3), the M element can exist in the form of an oxide, a composite oxide, a sulfate, a phosphate, or the like.

[0100] The aluminum-containing lithium cobalt composite oxide particles (3) of the positive electrode active material (2) for the lithium secondary battery of the present invention are particulate matters of the above aluminum-containing lithium cobalt composite oxide. The average particle size of the aluminum-containing lithium cobalt composite oxide particles (3) is the particle size (D50) at which the volume accumulation is 50% in the particle size distribution measured by the laser diffraction / scattering method, and is preferably 0.5 to 30 μm, particularly preferably 3 to 25 μm. In addition, the BET specific surface area of the aluminum-containing lithium cobalt composite oxide particles (3) is preferably 0.05 to 5.0 m 2 / g, particularly preferably 0.15 to 1.0 m 2 / g. By making the average particle size or BET specific surface area of the aluminum-containing lithium cobalt composite oxide particles (3) within the above range, it is possible to facilitate the preparation and coating of the positive electrode mixture, and thus obtain an electrode with high filling properties.

[0101] In the positive electrode active material (2) for the lithium secondary battery of the present invention, the mixing amount of the inorganic fluoride particles in the mixture of the aluminum-containing lithium cobalt composite oxide particles (3) and the inorganic fluoride particles is preferably 0.05 to 5.0 mol%, particularly preferably 0.1 to 2.0 mol%, in terms of the molar percentage ((F / Co)×100) of F relative to the atomic equivalent of Co in the aluminum-containing lithium cobalt composite oxide particles (3). By making the molar percentage ((F / Co)×100) of F relative to the atomic equivalent of Co in the aluminum-containing lithium cobalt composite oxide particles (3) within the above range, it is possible not only to suppress the decrease in the charge-discharge capacity of the positive electrode active material for the lithium secondary battery, but also to improve the effect of improving the cycle performance at high voltages, and to reduce the impedance of the positive electrode active material for the lithium secondary battery.

[0102] The mixing ratio of MgF2 is 0.05 to 50, preferably 0.1 to 10, particularly preferably 0.7 to 5, in terms of the molar ratio (MgF2 / AlF3) relative to AlF3. By making the mixing ratio of MgF2 relative to AlF3 (molar ratio of MgF2 / AlF3) within the above range, it is possible to achieve both excellent initial discharge capacity and impedance.

[0103] The average particle size of the inorganic fluoride particles of the positive electrode active material (2) for the lithium secondary battery of the present invention is preferably 0.01 to 30 μm, particularly preferably 0.1 to 20 μm, in terms of the particle size (D50) at which the volume accumulation is 50% in the particle size distribution measured by the laser diffraction / scattering method. By making the average particle size of the inorganic fluoride particles within the above range, no adverse conditions are likely to occur in the kneading process during the preparation of the positive electrode mixture, the coating process of applying the obtained positive electrode mixture to the positive electrode current collector, etc.

[0104] The average particle size of the positive electrode active material (2) for the lithium secondary battery of the present invention is preferably 0.5 to 30 μm, particularly preferably 3 to 25 μm, as measured by the volume cumulative 50% particle size (D50) in the particle size distribution measured by the laser diffraction / scattering method. In addition, the BET specific surface area of the positive electrode active material (2) for the lithium secondary battery of the present invention is preferably 0.05 to 5.0 m 2 / g, particularly preferably 0.15 to 1.0 m 2 / g. By making the average particle size or BET specific surface area of the positive electrode active material (2) for the lithium secondary battery of the present invention within the above range, no adverse conditions are likely to occur in the kneading process during the preparation of the positive electrode mixture, the coating process of applying the obtained positive electrode mixture to the positive electrode current collector, etc.

[0105] The c-axis lattice constant of the positive electrode active material (2) for the lithium secondary battery of the present invention is preferably 14.055 to 14.070 Å, particularly preferably 14.055 to 14.065 Å. By making the lattice constant of the c-axis within the above range, the lattice structure collapse caused by charge and discharge can be reduced, and the cycle performance can be improved.

[0106] In the second sintering process of the manufacturing method of the positive electrode active material for the lithium secondary battery of the present invention, a mixture of aluminum-containing lithium cobalt composite oxide particles and inorganic fluoride particles as the first sintered product is sintered, and the sintering in this second sintering process does not affect the size of the c-axis lattice constant of the aluminum-containing lithium cobalt composite oxide particles. Therefore, in the positive electrode active material (2) for the lithium secondary battery of the present invention, the size of the c-axis lattice constant depends on the aluminum-containing lithium cobalt composite oxide particles in the mixture of the aluminum-containing lithium cobalt composite oxide particles and the inorganic fluoride particles.

[0107] The lithium secondary battery of the present invention uses the positive electrode active material for the lithium secondary battery of the present invention as the positive electrode active material.

[0108] The lithium secondary battery of the present invention is composed of a positive electrode, a negative electrode, a separator, and a non-aqueous electrolyte containing a lithium salt.

[0109] The positive electrode of the lithium secondary battery of the present invention is formed by, for example, coating a positive electrode mixture on a positive electrode current collector and drying. The positive electrode mixture is composed of a positive electrode active material, a conductive agent, a binder, and a filler added as needed, etc.

[0110] In the lithium secondary battery of the present invention, the positive electrode active material for the lithium secondary battery of the present invention is uniformly coated on the positive electrode. Therefore, the lithium secondary battery of the present invention has high battery performance, particularly excellent cycle performance at high voltage, cycle performance at high voltage and high temperature, and high temperature storage performance, and low impedance.

[0111] The content of the positive electrode active material contained in the positive electrode mixture of the lithium secondary battery of the present invention is preferably 70 to 100% by mass, more preferably 90 to 98% by mass.

[0112] There is no particular limitation on the positive electrode current collector of the lithium secondary battery of the present invention, as long as it is an electronic conductor that does not cause chemical changes in the formed battery. For example, stainless steel, nickel, aluminum, titanium, sintered carbon, products with surfaces such as carbon, nickel, titanium, and silver-treated aluminum or stainless steel, etc. can be cited. The surfaces of these materials can be used after oxidation, or the surface of the current collector can be made to have unevenness through surface treatment. In addition, as the form of the current collector, foil, film, sheet, net, perforated plate, strip body, porous body, foam body, fiber bundle, non-woven fabric molded body, etc. can be cited. The thickness of the current collector is preferably, but not particularly limited to, 1 to 500 μm.

[0113] There is no particular limitation on the conductive agent of the lithium secondary battery of the present invention, as long as it is a conductive material that does not cause chemical changes in the formed battery. For example, graphite such as natural graphite and artificial graphite, carbon black such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lampblack, pyrolytic carbon black, etc., conductive fiber types such as carbon fiber and metal fiber, metal powder types such as carbon fluoride, aluminum powder, nickel powder, conductive whiskers such as zinc oxide and potassium titanate, conductive metal oxides such as titanium oxide, or conductive materials such as polyphenylene derivatives can be cited. Among them, as natural graphite, for example, flake graphite, scaly graphite, and earthy graphite can be cited. These conductive materials can be used alone or in combination of two or more. The blending ratio of the conductive agent in the positive electrode mixture is 1 to 50% by mass, preferably 2 to 30% by mass.

[0114] As the binder of the lithium secondary battery of the present invention, for example, starch, polyvinylidene fluoride, polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, regenerated cellulose, diacetyl cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene - propylene - diene terpolymer (EPDM), sulfonated EPDM, styrene-butadiene rubber, fluororubber, tetrafluoroethylene - hexafluoroethylene copolymer, tetrafluoroethylene - hexafluoropropylene copolymer, tetrafluoroethylene - perfluoroalkyl vinyl ether copolymer, vinylidene fluoride - hexafluoropropylene copolymer, vinylidene fluoride - chlorotrifluoroethylene copolymer, ethylene - tetrafluoroethylene copolymer, polychlorotrifluoroethylene, vinylidene fluoride - pentafluoropropylene copolymer, propylene - tetrafluoroethylene copolymer, ethylene - chlorotrifluoroethylene copolymer, vinylidene fluoride - hexafluoropropylene - tetrafluoroethylene copolymer, vinylidene fluoride - perfluoromethyl vinyl ether - tetrafluoroethylene copolymer, ethylene - acrylic acid copolymer or its (Na ﹢ )ion crosslinked body, ethylene - methacrylic acid copolymer or its (Na ﹢ )ion crosslinked body, ethylene - methyl acrylate copolymer or its (Na ﹢), an ionomer, ethylene-methyl methacrylate copolymer or its (Na ﹢ ), an ionomer, a polysaccharide such as polyethylene oxide, a thermoplastic resin, a polymer having rubber elasticity, etc. These binders can be used alone or in combination of two or more. It should be noted that when using a compound such as a polysaccharide containing a functional group capable of reacting with lithium, it is preferable to add a compound such as an isocyanate group to inactivate these functional groups. The blending ratio of the binder in the positive electrode mixture is 1 to 50% by mass, preferably 2 to 15% by mass.

[0115] The filler of the lithium secondary battery of the present invention is an additive that suppresses volume expansion of the positive electrode in the positive electrode mixture and can be added as needed. As the filler, any material can be used as long as it is a fibrous material that does not cause chemical changes in the formed battery. For example, olefin polymers such as polypropylene and polyethylene, and fibers such as glass fiber and carbon fiber can be used. The addition amount of the additive is preferably, but not particularly limited to, 0 to 30% by mass in the positive electrode mixture.

[0116] The negative electrode of the lithium secondary battery of the present invention is formed by coating a negative electrode material on a negative electrode current collector and drying. There is no particular limitation on the negative electrode current collector of the lithium secondary battery of the present invention as long as it is an electronic conductor that does not cause chemical changes in the formed battery. For example, stainless steel, nickel, copper, titanium, aluminum, sintered carbon, products with carbon, nickel, titanium, silver surface treatment on the surface of copper or stainless steel, and aluminum cadmium alloy, etc. can be cited. In addition, the surface of these materials can be used after oxidation, or the surface of the current collector can be made to have unevenness through surface treatment and then used. In addition, as the form of the current collector, for example, foil, film, sheet, net, punched plate, slat body, porous body, foam body, fiber bundle, non-woven fabric molded body, etc. can be cited. The thickness of the current collector is preferably, but not particularly limited to, 1 to 500 μm.

[0117] As the negative electrode material of the lithium secondary battery of the present invention, but not particularly limited to, for example, carbonaceous materials, metal composite oxides, lithium metal, lithium alloy, silicon alloy, tin alloy, metal oxides, conductive polymers, chalcogenides, Li-Co-Ni-based materials, Li4Ti5O 12 , lithium niobate, silicon oxide (SiO x : 0.5 ≤ x ≤ 1.6), etc. As the carbonaceous material, for example, non-graphitized carbon materials, graphite-based carbon materials, etc. can be cited. As the metal composite oxide, for example, Sn p (M1) 1－p (M2) q O r(In the formula, M1 represents one or more elements selected from Mn, Fe, Pb, and Ge, M2 represents one or more elements selected from Al, B, P, Si, Group IA, IIA, IIIB of the periodic table, and halogen elements, 0 < p ≤ 1, 1 ≤ q ≤ 3, 1 ≤ r ≤ 8), Li t Fe2O3 (0 ≤ t ≤ 1), Li t Compounds such as WO2 (0 ≤ t ≤ 1). Examples of the metal oxide include GeO, GeO2, SnO, SnO2, PbO, PbO2, Pb2O3, Pb3O4, Sb2O3, Sb2O4, Sb2O5, Bi2O3, Bi2O4, Bi2O5, etc. Examples of the conductive polymer include polyacetylene, poly(phenylene), etc.

[0118] As the separator of the lithium secondary battery of the present invention, an insulating film having high ion permeability and a set mechanical strength can be used. From the viewpoints of resistance to organic solvent corrosion and hydrophobicity, olefin-based polymers such as polypropylene, or sheets and non-woven fabrics made of glass fiber, polyethylene, etc. can be used. The pore diameter of the separator is within the range usually available for battery use, for example, 0.01 to 10 μm. The thickness of the separator is within the range usually available for batteries, for example, 5 to 300 μm. It should be noted that when a solid electrolyte such as a polymer is used as the electrolyte described later, the solid electrolyte can also serve as the separator.

[0119] The non-aqueous electrolyte of the lithium secondary battery of the present invention is composed of an electrolyte containing a non-aqueous electrolyte and a lithium salt. As the non-aqueous electrolyte of the lithium secondary battery of the present invention, a non-aqueous electrolyte solution, an organic solid electrolyte, and an inorganic solid electrolyte are used. Examples of the non-aqueous electrolyte solution include a solvent composed of one or more of aprotic organic solvents such as N-methyl-2-pyrrolidone, propylene carbonate, ethylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, γ-butyrolactone, 1,2-dimethoxyethane, tetrahydrofuran, 2-methyltetrahydrofuran, dimethyl sulfoxide, 1,3-dioxolane, formamide, dimethylformamide, dioxolane, acetonitrile, nitromethane, methyl formate, methyl acetate, triphosphate, trimethoxymethane, dioxolane derivatives, sulfolane, methylsulfolane, 3-methyl-2-oxazolidinone, 1,3-dimethyl-2-imidazolidinone, propylene carbonate derivatives, tetrahydrofuran derivatives, diethyl ether, 1,3-propane sultone, methyl propionate, ethyl propionate, etc.

[0120] As the organic solid electrolyte of the lithium secondary battery of the present invention, for example, polyethylene derivatives, poly(ethylene oxide) derivatives or polymers containing them, poly(propylene oxide) derivatives or polymers containing them, phosphate polymers, polyphosphazenes, polyethyleneimine, poly(ethyl thioether), poly(vinyl alcohol), poly(vinylidene fluoride), poly(hexafluoropropylene) and other polymers containing ionic dissociation groups, mixtures of polymers containing ionic dissociation groups and the above non-aqueous electrolytes, etc. can be cited.

[0121] As the inorganic solid electrolyte of the lithium secondary battery of the present invention, nitrides, halides, oxoacids salts, sulfides, etc. of Li can be used, and for example, Li3N, LiI, Li5NI2, Li3N−LiI−LiOH, LiSiO4, LiSiO4−LiI−LiOH, Li2SiS3, Li4SiO4, Li4SiO4−LiI−LiOH, P2S5, Li2S or Li2S−P2S5, Li2S−SiS2, Li2S−GeS2, Li2S−Ga2S3, Li2S−B2S3, Li2S−P2S5−X, Li2S−SiS2−X, Li2S−GeS2−X, Li2S−Ga2S3−X, Li2S−B2S3−X, etc. can be cited. In the formula, X is at least one or more selected from LiI, B2S3 or Al2S3.

[0122] In addition, when the inorganic solid electrolyte is amorphous (glass), the inorganic solid electrolyte may contain oxygen-containing compounds such as lithium phosphate (Li3PO4), lithium oxide (Li2O), lithium sulfate (Li2SO4), phosphorus pentoxide (P2O5), lithium borate (Li3BO3), etc., Li3PO 4－u N 2u / 3 (u is 0 < u < 4), Li4SiO 4－u N 2u / 3 (u is 0 < u < 4), Li4GeO 4－u N 2u / 3 (u is 0 < u < 4), Li3BO 3－u N 2u / 3 (u is 0 < u < 3) and other nitrogen-containing compounds. By adding the oxygen-containing compound or nitrogen-containing compound, the gaps of the formed amorphous skeleton can be expanded, the obstacles to lithium ion movement can be reduced, and the ion transport performance can be further improved.

[0123] As the lithium salt of the lithium secondary battery of the present invention, a lithium salt soluble in the above non-aqueous electrolyte is used, and for example, LiCl, LiBr, LiI, LiClO4, LiBF4, LiB 10 Cl 10 、LiPF6、LiCF3SO3、LiCF3CO2、LiAsF6、LiSbF6、LiB 10Cl 10 A salt formed by mixing one or more of LiAlCl4, CH3SO3Li, CF3SO3Li, (CF3SO2)2NLi, lithium chloroborate, lithium lower fatty acid, lithium tetraphenylborate, imide, etc.

[0124] In addition, for the purpose of improving discharge / charge performance and flame retardancy, the following compounds can be added to the non-aqueous electrolyte. For example, pyridine, triethyl phosphite, triethanolamine, cyclic ether, ethylenediamine, dimethyl ether, hexaphosphoric triamide, nitrobenzene derivative, sulfur, quinone imide dye, N-substituted oxazolidinone and N,N-substituted imidazoline, ethylene glycol dialkyl ether, ammonium salt, polyethylene glycol, pyrrole, 2-methoxyethanol, aluminum trichloride, conductive polymer electrode active substance monomer, triethylenephosphoramide, trialkylphosphine, morpholine, aryl compound with carbonyl, hexamethylphosphoric triamide and 4-alkylmorpholine, bicyclic tertiary amine, oil, phosphonium salt and sulfonium salt, phosphazene, carbonate, etc. In addition, in order to make the electrolyte non-flammable, the electrolyte can contain halogen-containing solvents such as carbon tetrachloride and trifluoroethylene. In addition, in order to be suitable for high-temperature storage, carbon dioxide gas can be contained in the electrolyte.

[0125] The lithium secondary battery of the present invention is a lithium secondary battery with high volumetric capacity, excellent safety and cycle performance, high energy density retention rate, and little reduction in average working voltage. The shape of the battery can be any shape such as button-shaped, sheet-shaped, cylindrical, square, coin-shaped, etc.

[0126] The uses of the lithium secondary battery of the present invention can include, but are not particularly limited to, for example, electronic devices such as laptop computers, notebook computers, pocket word processors, mobile phones, cordless phones, portable CD players, radios, liquid crystal TVs, backup power supplies, electric shavers, memory cards, video movie cameras, automobiles, electric vehicles, game devices, robots, drones, power tools, etc.

[0127] Examples Examples are given below to illustrate the present invention in more detail, but the present invention is not limited thereto.

[0128] (X-ray diffraction analysis) In the examples, measurements were carried out using an X-ray diffraction apparatus (Ultima IV manufactured by Rigaku Corporation) under the following measurement conditions.

[0129] X-ray source: CuKα Tube voltage: 40 kV Tube current: 40 mA Scanning speed: 4.0° / sec (Example 1) (First mixing process) Weigh cobalt tetroxide (average particle size 2.1 μm), lithium carbonate (average particle size 5.7 μm) and aluminum hydroxide (average particle size 1.6 μm), and mix them with a coffee grinder to obtain a first mixture with a molar ratio of Li to Co (Li / Co) of 1.040 and a molar percentage of Al to Co ((Al / Co)×100) of 1.0 mol%.

[0130] (First sintering process) Subsequently, sinter the obtained first mixture in an alumina crucible at a temperature of 900 °C for 5 hours. The sintered product was analyzed by X-ray diffraction and confirmed to be single-phase LiCoO2. Therefore, it was confirmed that Al was solid-solved inside the lithium cobalt composite oxide particles (see Figure 1 ).

[0131] After sintering was completed, the sintered product was crushed and classified to obtain aluminum-containing lithium cobalt composite oxide particles with an Al content of 1.0 mol% relative to Co.

[0132] (Second mixing process) Subsequently, weigh the obtained aluminum-containing lithium cobalt composite oxide particles, MgF2 (average particle size D50 = 0.9 μm) and AlF3 (average particle size D50 = 2.2 μm), and mix them with a coffee grinder to obtain a second mixture with a mol% of F relative to Co ((F / Co)×100) of 0.9 mol% and a molar ratio of the content ratio of MgF2 to AlF3 (MgF2 / AlF3) of 3.

[0133] (Second sintering process) Subsequently, sinter the obtained second mixture in an alumina crucible at a temperature of 600 °C for 5 hours.

[0134] After sintering was completed, the sintered product was crushed and classified to obtain a positive electrode active material sample.

[0135] (Examples 2 - 7) According to the same operation as in Example 1, a sintered product was obtained through the first mixing process and the first sintering process shown in Table 1. The sintered product was analyzed by X-ray diffraction and confirmed to be single-phase LiCoO2. Therefore, it was confirmed that Al was solid-solved inside the lithium cobalt composite oxide particles.

[0136] Subsequently, the sintered product was crushed and classified to obtain an aluminum-containing lithium cobalt composite oxide. Subsequently, the same operations as in Example 1 were carried out, and a positive electrode active material sample was obtained through the second mixing process and the second sintering process.

[0137] (Comparative Example 1) (First mixing process) Weigh cobalt(II,III) oxide (average particle size 2.1 μm) and lithium carbonate (average particle size 5.7 μm), and mix them with a coffee grinder to obtain a first mixture with a molar ratio of Li to Co (Li / Co) of 1.040.

[0138] (First sintering process) Subsequently, sinter the obtained first mixture in an alumina crucible at a temperature of 900 °C for 5 hours. The sintered product was analyzed by X-ray diffraction and confirmed to be single-phase LiCoO2.

[0139] After sintering is completed, crush and classify the sintered product to obtain lithium cobalt composite oxide particles.

[0140] (Second mixing process) Subsequently, weigh the obtained lithium cobalt composite oxide particles, MgF2 (average particle size 0.9 μm), and AlF3 (average particle size 2.2 μm), and mix them with a coffee grinder to obtain a second mixture with an F mol% relative to Co ((F / Co)×100) of 0.9 mol% and a molar ratio of the content ratio of MgF2 to AlF3 (MgF2 / AlF3) of 3.

[0141] (Second sintering process) Subsequently, sinter the obtained second mixture in an alumina crucible at a temperature of 600 °C for 5 hours.

[0142] After sintering is completed, crush and classify the sintered product to obtain a positive electrode active material sample.

[0143] (Comparative Example 2) (First mixing process) Weigh cobalt(II,III) oxide (average particle size 2.1 μm), lithium carbonate (average particle size 5.7 μm), and aluminum hydroxide (average particle size 1.6 μm), and mix them with a coffee grinder to obtain a first mixture with a molar ratio of Li to Co (Li / Co) of 1.040 and an Al mol% relative to Co ((Al / Co)×100) of 1.0 mol%.

[0144] (First sintering process) Subsequently, sinter the obtained first mixture in an alumina crucible at a temperature of 900 °C for 5 hours. The sintered product was analyzed by X-ray diffraction and confirmed to be single-phase LiCoO2.

[0145] After sintering is completed, crush and classify the sintered product to obtain a positive electrode active material sample.

[0146] (Reference Example 1) (First mixing process) Weigh cobalt(II,III) oxide (average particle size 2.1 μm), lithium carbonate (average particle size 5.7 μm), titanium dioxide (average particle size 0.4 μm) and calcium sulfate (average particle size 7.3 μm), and mix them with a household blender to obtain a first mixture with a molar ratio of Li to Co (Li / Co) of 1.043, a molar percentage of Ti relative to Co ((Ti / Co)×100) of 1.0 mol%, and a molar percentage of Ca relative to Co ((Ca / Co)×100) of 0.06 mol%.

[0147] (First sintering process) Subsequently, sinter the obtained first mixture in an alumina crucible at a temperature of 1070 °C for 5 hours.

[0148] After the sintering is completed, crush and classify the sintered product to obtain lithium cobalt composite oxide particles with a Ti content relative to Co of 1.0 mol% and a Ca content relative to Co of 0.06 mol%.

[0149] (Second mixing process) Subsequently, weigh the obtained lithium cobalt composite oxide particles, MgF2 (average particle size 0.9 μm) and AlF3 (average particle size 2.2 μm), and mix them with a coffee grinder to obtain a second mixture with an F mol% relative to Co ((F / Co)×100) of 0.85 mol% and a molar ratio of the content ratio of MgF2 to AlF3 (MgF2 / AlF3) of 0.625.

[0150] (Second sintering process) Subsequently, sinter the obtained second mixture in an alumina crucible at a temperature of 600 °C for 5 hours.

[0151] After the sintering is completed, crush and classify the sintered product to obtain a positive electrode active material sample.

[0152] The following physical properties (average particle size, BET specific surface area, and c-axis lattice constant) of the positive electrode active material samples obtained in Examples 1 to 7, Comparative Examples 1 and 2, and Reference Example 1 were measured. The results are shown in Tables 1 and 2.

[0153] (1) Average particle size The average particle size was determined from the particle size (D50) at which the volume accumulation is 50% in the particle size distribution measured by the laser diffraction / scattering method.

[0154] (2) BET specific surface area The BET specific surface area was measured by the BET method.

[0155] (3) Lattice constant of the c-axis The lattice constant of the c-axis was measured by Rietveld analysis of the diffraction pattern obtained by using the X-ray diffraction (XRD) method.

[0156] [Table 1] [Table 2] In Table 2, "*" indicates that the mol% of Ti relative to Co is 1.0 mol%, and the mol% of Ca relative to Co is 0.06%.

[0157] Based on Table 1 and Table 2, it can be seen that: regarding the lattice constant of the c-axis, the positive electrode active material sample without Al solid solution (Comparative Example 1) has a smaller lattice constant of the c-axis compared to the positive electrode active material sample with Al solid solution (Examples 1 to 4).

[0158] Moreover, it can be seen that: regarding the content of Al relative to Co, it is 0.5 mol% in Example 2 (lattice constant of the c-axis: 14.055 Å), 0.75 mol% in Example 4 (lattice constant of the c-axis: 14.056 Å), 1.0 mol% in Example 1 (lattice constant of the c-axis: 14.059 Å), and 2.0 mol% in Example 3 (lattice constant of the c-axis: 14.060 Å). As the content of Al relative to Co increases, the lattice constant of the c-axis also increases.

[0159] Subsequently, the battery performance test was carried out as follows.

[0160] <Preparation of Lithium Secondary Battery>[ 95% by mass of the positive electrode active materials obtained in Examples 1 to 7, Comparative Examples 1 and 2, and Reference Example 1, 2.5% by mass of graphite powder, and 2.5% by mass of polyvinylidene fluoride were mixed to form a positive electrode mixture, which was dispersed in N-methyl-2-pyrrolidone to make a kneaded paste. After coating this kneaded paste on an aluminum foil, it was dried, pressed, and punched into a disk with a diameter of 15 mm to obtain a positive electrode plate.

[0161] Using this positive electrode plate, a button-type lithium secondary battery was made using various components such as a separator, a negative electrode, a positive electrode, a current collector plate, an assembly metal part, an external terminal, and an electrolyte. Among them, a metal lithium foil was used as the negative electrode, and an electrolyte prepared by dissolving 1 mole of LiPF6 and 1 wt% of vinylene carbonate in 1 L of a mixed solution of ethylene carbonate, dimethyl carbonate, and diethyl carbonate in a ratio of 2.5:6:1.5 was used.

[0162] <Performance Evaluation of Battery>[ The following battery performances (cycle performance at high voltage, cycle performance at high voltage and high temperature, and impedance) of the fabricated button-type lithium secondary battery were evaluated. The results are shown in Tables 3, 4, and 5.

[0163] (1) Evaluation of cycle performance at high voltage (1-1) Test conditions First, charging was carried out at 0.5C for 2 hours until 4.6V, then constant current constant voltage charging (CCCV charging) was carried out at 4.6V for 3 hours, and then constant current discharging (CC discharging) was carried out at 0.2C until 2.7V. The charge and discharge operation was taken as one cycle, and the discharge capacity of each cycle was measured. This cycle was repeated 20 times at a temperature of 25°C.

[0164] (1-2) Initial discharge capacity at high voltage The discharge capacity of the first cycle in the cycle performance evaluation was set as the initial discharge capacity (initial discharge capacity at 25°C (4.6V)).

[0165] (1-3) Capacity retention rate at high voltage Based on the discharge capacities (per unit active material weight) at the first cycle and the 20th cycle in the cycle performance evaluation, the capacity retention rate at high voltage (capacity retention rate at 25°C (4.6V)) was calculated by the following formula.

[0166] Capacity retention rate (%) = (discharge capacity at the 20th cycle / discharge capacity at the first cycle) × 100 (2) Evaluation of cycle performance at high voltage and high temperature (2-1) Test conditions First, charging was carried out at 0.5C for 2 hours until 4.55V, then constant current constant voltage charging (CCCV charging) was carried out at 4.55V for 3 hours, and then constant current discharging (CC discharging) was carried out at 0.2C until 2.7V. The charge and discharge operation was taken as one cycle, and the discharge capacity of each cycle was measured. This cycle was repeated 50 times at a temperature of 45°C.

[0167] (2-2) Initial discharge capacity at high voltage and high temperature The discharge capacity of the first cycle in the high temperature cycle performance evaluation was set as the initial discharge capacity at high voltage and high temperature (initial discharge capacity at 45°C (4.55V)).

[0168] (2-3) Capacity retention rate at high voltage and high temperature Based on the discharge capacities (per unit active material weight) at the 1st cycle and the 50th cycle in the cycle performance evaluation, the capacity retention rate at high voltage and high temperature (capacity retention rate at 45 °C (4.55 V)) was calculated by the following formula.

[0169] Capacity retention rate at high voltage and high temperature (%) = (Discharge capacity at the 50th cycle / Discharge capacity at the 1st cycle) × 100 (3) Impedance After the button-type lithium secondary battery was brought to a state where the SOC reached 100%, i.e., fully charged, the AC impedance was measured using an impedance measurement device under the conditions that the applied voltage was 0 V relative to the open circuit, i.e., no voltage was applied, and the frequency measurement range was 0.02 Hz to 20 kHz. Then, the impedance value was obtained from the Cole-Cole plot obtained from the AC impedance measurement.

[0170] [Table 3] [Table 4] [Table 5]

Claims

1. A positive electrode active material for a lithium secondary battery, characterized in that it is composed of a mixture of aluminum-containing lithium cobalt composite oxide particles and inorganic fluoride particles, in the aluminum-containing lithium cobalt composite oxide particles, aluminum is at least dissolved and present inside the aluminum-containing lithium cobalt composite oxide particles, and the inorganic fluoride particles are MgF2 and a compound containing Al and F.

2. The positive electrode active material for a lithium secondary battery according to claim 1, characterized in that the compound containing Al and F is AlF3 and / or LiAlF4.

3. The positive electrode active material for a lithium secondary battery according to claim 1 or 2, characterized in that the Al content of the aluminum-containing lithium cobalt composite oxide particles, calculated as the molar% of Al relative to the atomic equivalent of Co in the aluminum-containing lithium cobalt composite oxide particles ((Al / Co)×100), is 0.05 to 5.0 mol%.

4. The positive electrode active material for a lithium secondary battery according to claim 1 or 2, characterized in that the content of the inorganic fluoride particles, calculated as the molar% of F relative to the atomic equivalent of Co in the aluminum-containing lithium cobalt composite oxide particles ((F / Co)×100), is 0.05 to 5.0 mol%.

5. The positive electrode active material for a lithium secondary battery according to claim 1 or 2, characterized in that the mixing ratio of the MgF2 and the compound containing Al and F, calculated as the ratio of the number of moles of F of the atomic equivalent of MgF2 to the number of moles of F of the atomic equivalent of the compound containing Al and F (number of moles of F of the atomic equivalent of MgF2 / number of moles of F of the atomic equivalent of the compound containing Al and F), is 0.033 to 33.

6. The positive electrode active material for a lithium secondary battery according to claim 1 or 2, characterized in that the lattice constant of the c-axis is 14.055 to 14.070 Å.

7. The positive electrode active material for a lithium secondary battery according to claim 1 or 2, characterized in that in the aluminum-containing lithium cobalt composite oxide particles, as the M element, it contains one or more selected from Ca, Mg, Sr, Zr, Nb, B, and W.

8. A positive electrode active material for a lithium secondary battery, characterized in that, The positive electrode active material for a lithium secondary battery is a sintered product of a mixture of aluminum-containing lithium cobalt composite oxide particles and inorganic fluoride particles, wherein in the aluminum-containing lithium cobalt composite oxide particles, aluminum is at least dissolved and present inside the aluminum-containing lithium cobalt composite oxide particles, and the inorganic fluoride particles are MgF2 and AlF3.

9. The positive electrode active material for a lithium secondary battery according to claim 8, characterized in that the aluminum-containing lithium cobalt composite oxide particles are a sintered product of a mixture of a lithium compound, a cobalt compound, and an aluminum compound.

10. The positive electrode active material for a lithium secondary battery according to claim 8 or 9, characterized in that the Al content of the aluminum-containing lithium cobalt composite oxide particles, calculated as the molar% of Al relative to the atomic equivalent of Co in the aluminum-containing lithium cobalt composite oxide particles ((Al / Co)×100), is 0.05 to 5.0 mol%.

11. The positive electrode active material for a lithium secondary battery according to claim 8 or 9, characterized in that in the mixture of the aluminum-containing lithium cobalt composite oxide particles and the inorganic fluoride particles, the mixing amount of the inorganic fluoride particles is 0.05 to 5.0 mol% in terms of the molar percentage ((F / Co)×100) of F relative to the atomic equivalent of Co in the aluminum-containing lithium cobalt composite oxide particles.

12. The positive electrode active material for a lithium secondary battery according to claim 8 or 9, characterized in that in the mixture of the aluminum-containing lithium cobalt composite oxide particles and the inorganic fluoride particles, the mixing ratio of MgF2 to AlF3 is 0.05 to 50 in terms of the molar ratio (MgF2 / AlF3).

13. The positive electrode active material for a lithium secondary battery according to claim 8 or 9, characterized in that the lattice constant of the c-axis is 14.055 to 14.070 Å.

14. The positive electrode active material for a lithium secondary battery according to claim 8 or 9, characterized in that in the aluminum-containing lithium cobalt composite oxide particles, as the M element, one or more selected from Ca, Mg, Sr, Zr, Nb, B, and W are contained.

15. A method for manufacturing a positive electrode active material for a lithium secondary battery, characterized in that, It has: a first mixing step of mixing a lithium compound, a cobalt compound, and an aluminum compound as raw materials to obtain a first mixture; a first sintering step of sintering the first mixture to obtain, as a first sintered product, aluminum-containing lithium cobalt composite oxide particles in which aluminum is at least solid-soluted inside the particles; a second mixing step of mixing the first sintered product obtained in the first sintering step with inorganic fluoride particles to obtain a second mixture; and a second sintering step of sintering the second mixture to obtain, as a second sintered product, a positive electrode active material for a lithium secondary battery, wherein the inorganic fluoride particles are MgF2 and AlF3.

16. The method for manufacturing a positive electrode active material for a lithium secondary battery according to claim 15, characterized in that in the first mixing step, the aluminum compound is mixed so that the molar percentage ((Al / Co)×100) of Al relative to the atomic equivalent of Co in the first mixture is 0.05 to 5.0 mol%.

17. The method for manufacturing a positive electrode active material for a lithium secondary battery according to claim 15 or 16, characterized in that the first sintered product contains one or more selected from Ca, Mg, Sr, Zr, Nb, B, and W as the M element.

18. The method for manufacturing a positive electrode active material for a lithium secondary battery according to claim 15 or 16, characterized in that in the first sintering step, the sintering temperature is 800 to 1150 °C.

19. The method for manufacturing a positive electrode active material for a lithium secondary battery according to claim 15 or 16, characterized in that in the second mixing step, the inorganic fluoride particles are mixed so that the molar percentage ((F / C)×100) of F relative to the atomic equivalent of Co in the second mixture is 0.05 to 2.0 mol%.

20. The method for manufacturing a positive electrode active material for a lithium secondary battery according to claim 15 or 16, characterized in that the lattice constant of the c-axis of the positive electrode active material for a lithium secondary battery as the second sintered product is 14.055 to 14.070 Å.

21. A lithium secondary battery, characterized in that as the positive electrode active material, the positive electrode active material for a lithium secondary battery described in claim 1 or 8 is used.

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