Lithium cobalt composite oxide particles, method for producing same, lithium cobalt composite oxide particle composition, and method for producing same

Abstract

Provided are: lithium-cobalt composite oxide particles which are obtained by a solid-phase method and which, when used as a positive electrode active material for a non-aqueous lithium secondary battery or an all-solid-state battery, can achieve a reduction in weight and thickness of a positive electrode material; the average particle diameter of the primary particles of the lithium-cobalt composite oxide is 0.50 [mu] m or less, and the weight loss rate after heating at 850 DEG C is 1.5 mass% or less.

Description

Technical Field

[0001] The present invention relates to lithium-cobalt composite oxide particles useful as positive electrode materials for nonaqueous lithium secondary batteries, all-solid batteries, and the like, a lithium-cobalt composite oxide particle composition, and methods for producing the same. Background Art

[0002] Non-aqueous lithium secondary batteries are used as power sources for portable devices, laptop computers, electric vehicles, industrial robots, etc. Moreover, in recent years, the development of all-solid batteries using highly safe solid electrolytes has been actively carried out instead of non-aqueous lithium secondary batteries using electrolytes containing flammable organic solvents.

[0003] Recently, these non-aqueous lithium secondary batteries and all-solid batteries also need to be further lightweight and thinned according to their uses. In order to make the battery lightweight and thin, it is necessary to miniaturize the components that constitute the battery. For example, if the positive electrode material can be miniaturized, it will become one of the important factors related to the lightweight and thinning of the battery.

[0004] Regarding the miniaturization of positive electrode materials, for example, Patent Document 1 discloses an electrode component having a thin film positive electrode active material layer, wherein the thin film positive electrode active material layer is formed of the following particles, wherein the particles have a 10% particle size (D 10 ) is 0.01μm to 0.5μm, 50% particle size (D 50 ) is 0.01 μm to 1.0 μm, and the content of particles with a particle size of 0.12 μm or less is 0.5 volume % or more. Although Patent Document 1 does not specifically describe how the above-mentioned positive electrode active material is obtained, it is known that the electrode component can be made thinner by using a nano-scale positive electrode active material.

[0005] As for the nanomaterialization of lithium-based composite oxides as positive electrode active materials, Patent Document 2 discloses that nanoscale lithium-based composite oxides are synthesized by using molten salt as reactants and reaction medium and accompanying a drying process. This can improve functions or discover new functions compared to existing larger materials, and it is also expected to achieve miniaturization of electronic devices.

[0006] Prior art literature

[0007] Patent Literature

[0008] Patent Document 1: Japanese Patent Application Publication No. 2019-220468

[0009] Patent Document 2: Japanese Patent Application Publication No. 2008-105912 Summary of the invention

[0010] Technical problem to be solved by the invention

[0011] The method of Patent Document 2 utilizes the following principle: since the metal ions of the raw materials exist in a completely dissociated state in the molten salt, they exist mixed at the ionic level, and even with a relatively low temperature heat treatment, a chemical thermodynamic equilibrium can be achieved, and a stable substance can be easily formed.

[0012] However, although lithium-cobalt composite oxides are generally obtained by a so-called solid phase method in which a plurality of raw material powders are mixed and fired, the firing temperature still needs to be increased in order to allow the raw material powders to react fully. Therefore, although crystallization occurs, grain growth also occurs at the same time, resulting in an increase in the particle size of lithium-cobalt composite oxide particles, which makes it difficult to achieve lightweight and thin cathode materials.

[0013] Therefore, the object of the present invention is to provide a lithium-cobalt composite oxide particle and a method for producing the same. The lithium-cobalt composite oxide particle is obtained by a solid phase method and when used as a positive electrode active material for a non-aqueous lithium secondary battery or an all-solid-state battery, the positive electrode material can be made lighter and thinner.

[0014] Technical solutions for solving technical problems

[0015] In view of the above situation, the inventors of the present invention have repeatedly conducted in-depth research and found that by using a raw material in which the cobalt source is made into nano-particles, the reaction with the lithium source is easy to proceed, so that crystallization can be carried out well even if sintering is performed at a low temperature, thereby completing the present invention.

[0016] That is, the present invention (1) provides lithium-cobalt composite oxide particles, characterized in that the average particle size of primary particles of the lithium-cobalt composite oxide is 0.50 μm or less, and the weight loss rate after heating at 850° C. is 1.5 mass % or less.

[0017] In addition, the present invention (2) provides the lithium-cobalt composite oxide particles described in (1) above, characterized in that the BET specific surface area is 2.0 m 2 / g or above.

[0018] In addition, the present invention (3) provides the lithium-cobalt composite oxide particles according to (1) or (2) above, wherein the average particle size of the secondary particles of the lithium-cobalt composite oxide is 0.10 to 2.00 μm.

[0019] In addition, the present invention (4) provides lithium-cobalt composite oxide particles according to any one of (1) to (3) above, characterized in that no impurity phase other than the hexagonal crystal phase (R-3m) derived from the lithium-cobalt composite oxide appears in X-ray diffraction analysis.

[0020] In addition, the present invention (5) provides the lithium-cobalt composite oxide particles according to any one of (1) to (4) above, wherein the lithium-cobalt composite oxide particles are obtained by a solid phase method.

[0021] In addition, the present invention (6) provides a method for producing lithium-cobalt composite oxide particles, characterized in that it includes: a raw material mixture preparation step of preparing a raw material mixture containing at least a cobalt compound and a first lithium compound, and the average particle size of the secondary particles of the cobalt compound is 0.10 to 0.50 μm; and a formal firing step of firing the raw material mixture at 500 to 850°C.

[0022] In addition, the present invention (7) provides a method for producing lithium-cobalt composite oxide particles as described in the above (6), characterized in that the above cobalt compound is at least one selected from the hydroxide, oxide, carbonate, oxyhydroxyl, nitrate, sulfate and organic acid salt of the first cobalt.

[0023] In addition, the present invention (8) provides a method for producing lithium-cobalt composite oxide particles as described in (6) or (7) above, characterized in that the lithium compound is at least one selected from lithium carbonate, hydroxide, acetate and nitrate.

[0024] In addition, the present invention (9) provides a method for producing lithium-cobalt composite oxide particles as described in any one of (6) to (8) above, characterized in that a pre-firing process is performed between the raw material mixture preparation process and the formal firing process, and in the pre-firing process, the raw material mixture is pre-fired at a temperature of greater than 200°C and less than 500°C.

[0025] In addition, the present invention (10) provides the method for producing lithium-cobalt composite oxide particles according to the above (9), characterized in that the main firing step is performed after the pre-firing step, after the pre-firing product is cooled.

[0026] The present invention (11) provides the method for producing lithium-cobalt composite oxide particles according to (9) above, characterized in that the main firing step is performed without cooling the pre-fired product after the pre-fired step.

[0027] In addition, the present invention (12) provides a method for producing lithium-cobalt composite oxide particles as described in any one of (6) to (11) above, characterized in that a fired product crushing treatment step is carried out after the above-mentioned formal firing step, and in the fired product crushing treatment step, the lithium-cobalt composite oxide particles obtained by the above-mentioned formal firing step are crushed.

[0028] In addition, the present invention (13) provides the method for producing the lithium-cobalt composite oxide particles described in the above (12), wherein in the fired product pulverizing step, the lithium-cobalt composite oxide particles are pulverized by air flow pulverization.

[0029] In addition, the present invention (14) provides a lithium-cobalt-based composite oxide particle composition, characterized by containing the lithium-cobalt-based composite oxide particle according to any one of the above (1) to (5) and a second lithium compound.

[0030] In addition, the present invention (15) provides a method for producing a lithium-cobalt composite oxide particle composition, characterized in that it includes a mixing step, in which the lithium-cobalt composite oxide particles obtained by the method for producing lithium-cobalt composite oxide particles described in any one of (6) to (13) above and a second lithium compound are mixed or mixed and crushed.

[0031] In addition, the present invention (16) provides a method for producing a lithium-cobalt composite oxide particle composition as described in (15) above, characterized in that the second lithium compound is at least one selected from lithium carbonate, lithium hydroxide and lithium nitrate.

[0032] In addition, the present invention (17) provides a method for producing a lithium-cobalt composite oxide particle composition as described in (15) or (16) above, characterized in that the average particle size of the primary particles of the second lithium compound is 0.10 μm to 100.0 μm.

[0033] In addition, the present invention (18) provides a method for producing a lithium-cobalt composite oxide particle composition as described in (15) above, characterized in that the second lithium compound is lithium carbonate having an average primary particle size of 0.10 to 10.0 μm.

[0034] In addition, the present invention (19) provides a method for producing a lithium-cobalt composite oxide particle composition as described in any one of (15) to (18) above, characterized in that, in the mixing step, the second lithium compound and the lithium-cobalt composite oxide particles are mixed in such a manner that the lithium atom-converted content of the second lithium compound is 0.01 to 10.0 mass % relative to the mass of the lithium-cobalt composite oxide particles.

[0035] In addition, the present invention (20) provides a method for producing a lithium-cobalt composite oxide particle composition as described in any one of (15) to (19) above, characterized in that in the mixing step, the mixing treatment or the mixed pulverization treatment is carried out in a dry or wet manner.

[0036] Effects of the Invention

[0037] According to the present invention, a lithium-cobalt composite oxide particle, a lithium-cobalt composite oxide particle composition and a method for manufacturing the same are provided. The lithium-cobalt composite oxide particle is obtained by a solid phase method and when used as a positive electrode active material for a non-aqueous lithium secondary battery or an all-solid-state battery, the positive electrode material can be made lighter and thinner. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 This is the X-ray diffraction spectrum of the lithium-cobalt composite oxide particles obtained in Examples 1 to 6 and Comparative Example 1.

[0039] Figure 2 This is the X-ray diffraction spectrum of the lithium-cobalt composite oxide particles obtained in Examples 7 to 10 and Comparative Example 2.

[0040] Figure 3 This is the X-ray diffraction pattern of the lithium-cobalt composite oxide particles obtained in Comparative Examples 3 to 8.

[0041] Figure 4 This is the X-ray diffraction spectrum of the lithium-cobalt composite oxide particles obtained in Examples 11 to 13 and Comparative Example 9.

[0042] Figure 5 This is the X-ray diffraction spectrum of the lithium-cobalt composite oxide particles obtained in Examples 14 to 17. DETAILED DESCRIPTION

[0043] The lithium-cobalt composite oxide particles of the present invention are characterized in that the average particle size of primary particles of the lithium-cobalt composite oxide is 0.50 μm or less and the weight loss rate after heating at 850° C. is 1.5 mass % or less.

[0044] The lithium-cobalt composite oxide particles of the present invention are composed of primary particles of lithium-cobalt composite oxides, or secondary particles formed by aggregation of primary particles of lithium-cobalt composite oxides, or a mixture of primary particles and secondary particles of lithium-cobalt composite oxides. Furthermore, the lithium-cobalt composite oxide particles of the present invention are lithium-cobalt composite oxide particles obtained by a solid phase method.

[0045] The lithium-cobalt-based composite oxide involved in the lithium-cobalt-based composite oxide particles of the present invention is a composite oxide containing at least lithium and cobalt.

[0046] In the lithium-cobalt composite oxide particles of the present invention, the atomic molar ratio of Li to Co (Li / Co) is preferably 0.90 to 1.20, particularly preferably 0.95 to 1.15. When the atomic molar ratio of Li to Co (Li / Co) in the lithium-cobalt composite oxide particles is within the above range, the energy density of the positive electrode active material is improved.

[0047] In addition, the lithium-cobalt composite oxide particles of the present invention may contain an M element as needed to improve performance or physical properties. The M element is one or more metal elements selected from Mg, Al, Ti, Zr, Cu, Fe, Sr, Ca, V, Mo, Bi, Nb, Si, Zn, Ga, Ge, Sn, Ba, W, Na, K, Ni and Mn.

[0048] In the lithium-cobalt composite oxide particles of the present invention, the atomic conversion mol% of M element and Co ((M / Co)×100) is preferably 0.01 to 5.00 mol%, particularly preferably 0.05 to 2.00 mol%. When the lithium-cobalt composite oxide particles contain the M element, the atomic conversion mol% of M element and Co in the lithium-cobalt composite oxide particles ((M / Co)×100) is within the above range, which can improve the battery characteristics without impairing the charge and discharge capacity. In particular, when the lithium-cobalt composite oxide contains two or more M elements, the atomic conversion mole number of the M element as the calculation basis of the above mole % refers to the total mole number of each M element.

[0049] When the lithium-cobalt composite oxide particles of the present invention contain the M element, the M element may be present inside the lithium-cobalt composite oxide particles, or may be present on the surface of the lithium-cobalt composite oxide particles, or may be present both inside and on the surface of the lithium-cobalt composite oxide particles.

[0050] When the M element is present on the particle surface of the lithium-cobalt-based composite oxide particles of the present invention, the M element may be present in the form of an oxide, a composite oxide, a sulfate, a phosphate, or the like.

[0051] In the lithium-cobalt composite oxide particles of the present invention, the average particle size of the primary particles of the lithium-cobalt composite oxide is less than 0.50 μm, preferably 0.10 to 0.40 μm. Since the lithium-cobalt composite oxide particles of the present invention are obtained by sintering at a temperature of 500 to 850°C, which is lower than the prior art, the average particle size of the primary particles is small. When the average particle size of the primary particles of the lithium-cobalt composite oxide is within the above range, when used as a positive electrode active material for a non-aqueous lithium secondary battery or an all-solid battery, the positive electrode material can be made lighter and thinner. When the average particle size of the primary particles of the lithium-cobalt composite oxide exceeds the above range, the number of coarsened particles of the positive electrode active material increases, making it difficult to achieve a thin film of the positive electrode.

[0052] Among them, in the present invention, the average particle size of the primary particles of the lithium-cobalt composite oxide particles is the average particle size of the primary particles obtained from a scanning electron microscope (SEM) photograph. Based on the scanning electron microscope (SEM) observation, 100 primary particles are randomly selected, and the length of the horizontal Feret's diameter (Feret's diameter) of each particle is measured, and the average value of the 100 quantities is calculated as the average particle size of the primary particles.

[0053] The weight loss rate of the lithium cobalt composite oxide particles of the present invention after heating at 850°C is 1.5% by mass or less, preferably 1.0% by mass or less, and particularly preferably 0.5% by mass or less. Although the grain growth during firing can be suppressed by lowering the firing temperature when producing the lithium cobalt composite oxide particles, if the firing temperature is excessively lowered in order to suppress the grain growth excessively, the reaction of the raw materials will become insufficient. Then, when using lithium cobalt composite oxide particles whose raw materials are insufficiently reacted, not only will the positive electrode material production process be malfunctioned due to the unreacted raw materials, but the expected charge and discharge capacity of the lithium cobalt composite oxide will also be reduced. In contrast, the lithium cobalt composite oxide particles of the present invention are obtained by reducing the particle size of the cobalt source of the raw material mixture to increase the reactivity of the raw materials during firing, so that the reaction can be fully carried out, and the weight loss rate is 1.5% by mass or less, preferably 1.0% by mass or less, and particularly preferably 0.5% by mass or less, so that the positive electrode material production process will not be malfunctioned, or the expected charge and discharge capacity of the lithium cobalt composite oxide will not be reduced.

[0054] In the present invention, the weight reduction rate after heating at 850° C. is a value calculated according to the following formula.

[0055] Weight reduction rate (%) = ((X-Y) / X) × 100

[0056] X is the mass (g) of the lithium-cobalt composite oxide particles before heating at 850°C.

[0057] Y refers to the mass (g) of the lithium-cobalt composite oxide particles after the temperature is increased to 850° C. at a heating rate of 100° C. / hour, maintained at 850° C. for 5 hours, and then cooled to room temperature by natural cooling.

[0058] The BET specific surface area of ​​the lithium-cobalt composite oxide particles of the present invention is preferably 2.0 m 2 / g or more, particularly preferably 3.0 to 15.0 m 2 When the BET specific surface area of ​​the lithium-cobalt composite oxide particles is within the above range, the positive electrode material can be easily made lighter and thinner, thereby achieving miniaturization of the battery.

[0059] In the lithium-cobalt composite oxide particles of the present invention, the average particle size of the secondary particles of the lithium-cobalt composite oxide is preferably 0.10 to 2.00 μm, particularly preferably 0.20 to 1.00 μm. When the average particle size of the secondary particles of the lithium-cobalt composite oxide particles is within the above range, it is easy to make the positive electrode material lightweight and thin, and thus it is easy to achieve miniaturization of the battery. On the other hand, if the average particle size of the secondary particles of the lithium-cobalt composite oxide particles is lower than the above range, not only will it be difficult to handle the positive electrode active material particles in powder form, but the possibility of adverse conditions in the positive electrode material production process will also increase; and if it is larger than the above range, it will be difficult to thin the positive electrode due to the coarsening of the positive electrode active material particles. Among them, in the present invention, the average particle size of the secondary particles of the lithium-cobalt composite oxide particles refers to the volume conversion 50% particle size (D50) measured by laser scattering / scattering method using water as the measurement solvent.

[0060] The lithium-cobalt composite oxide particles of the present invention preferably do not show an impurity phase other than the hexagonal crystal phase (R-3m) derived from the lithium-cobalt composite oxide when subjected to X-ray diffraction analysis using CuKα rays as a radiation source. The hexagonal crystalline phase (R-3m) from the lithium-cobalt composite oxide indicates diffraction peaks that can be observed near 2θ=18.9° (18.9±0.2°), near 37.4° (37.4±0.2°), near 38.4° (38.4±0.2°), near 39.1° (39.1±0.2°), near 45.3° (45.3±0.2°), near 49.5° (49.5±0.2°), near 59.6° (59.6±0.2°), near 65.5° (65.5±0.2°), near 66.4° (66.4±0.2°), near 69.8° (69.8±0.2°), etc. from LiCoO2. In addition, the impurity phase indicates diffraction peaks other than the diffraction peaks from LiCoO2. Specific examples of such impurity phases include cobalt oxide (Co3O4) having a main peak near 36.8° (36.8±0.2°), lithium carbonate (Li2CO3) having a main peak near 31.8° (31.8±0.2°), and cubic lithium cobalt composite oxide (LiCoO2 cubic crystal) having a main peak near 19.2° (19.2±0.2°).

[0061] The lithium-cobalt composite oxide particles of the present invention are suitable for use as a positive electrode active material for lithium secondary batteries, all-solid batteries, and the like.

[0062] The method for producing the lithium-cobalt-based composite oxide particles of the present invention is not particularly limited, but the particles are preferably produced by the method for producing the lithium-cobalt-based composite oxide particles of the present invention described below.

[0063] The method for producing lithium-cobalt composite oxide particles of the present invention is characterized by comprising:

[0064] a raw material mixture preparation step of preparing a raw material mixture containing at least a cobalt compound and a first lithium compound, wherein the average particle size of secondary particles of the cobalt compound is 0.10 to 0.50 μm; and

[0065] The main firing step is to fire the raw material mixture at 500 to 850°C.

[0066] The raw material mixture preparation step in the method for producing lithium-cobalt composite oxide particles of the present invention is a step of preparing a raw material mixture containing at least a cobalt compound and a first lithium compound.

[0067] The cobalt compound is not particularly limited as long as it can be used as a raw material for producing the lithium-cobalt composite oxide, and examples thereof include cobalt oxides, oxyhydroxides, hydroxides, carbonates, nitrates, sulfates, and organic acid salts.

[0068] The average particle size of the secondary particles of the cobalt compound in the raw material mixture prepared in the raw material mixture preparation step is preferably 0.10 to 0.50 μm, particularly preferably 0.10 to 0.30 μm. When the average particle size of the secondary particles of the cobalt compound is within the above range, lithium-cobalt composite oxide particles having an average particle size of 0.50 μm or less, preferably 0.10 to 0.40 μm, can be obtained.

[0069] The first lithium compound in the raw material mixture preparation step is not particularly limited as long as it can be used as a raw material for producing a lithium-cobalt composite oxide, and examples thereof include lithium oxides, hydroxides, carbonates, nitrates, sulfates, and organic acid salts.

[0070] The average particle size of the first lithium compound in the raw material mixture preparation step is not particularly limited. A generally available compound can be used as the first lithium compound, and the particle size is generally in the range of 10 to 100 μm, for example.

[0071] In the raw material mixture preparation step, the content ratio of the first lithium compound to the cobalt compound in the raw material mixture is preferably 0.90 to 1.20, and particularly preferably 0.95 to 1.15, in terms of the ratio of the number of moles of Li to the number of moles of Co in terms of atomic conversion (Li / Co molar ratio). When the content ratio of the first lithium compound to the cobalt compound in the raw material mixture is within the above range, a single-phase lithium-cobalt composite oxide is easily obtained.

[0072] In the raw material mixture preparation step, the raw material mixture may contain a compound containing an M element as required. Examples of the compound containing an M element include oxides, hydroxides, carbonates, nitrates, sulfates, fluorides, and organic acid salts containing an M element. Examples of the compound containing an M element include compounds containing two or more M elements. Examples of the M element include Mg, Al, Ti, Zr, Cu, Fe, Sr, Ca, V, Mo, Bi, Nb, Si, Zn, Ga, Ge, Sn, Ba, W, Na, K, Ni, and Mn.

[0073] The first lithium compound, the cobalt compound, and the compound containing the M element as raw materials do not need to be considered in the production process, but in order to produce high-purity lithium-cobalt composite oxide particles, the impurity content is preferably as small as possible.

[0074] In the raw material mixture preparation step, the first lithium compound, the cobalt compound, and the compound containing the M element used as required are mixed to prepare the raw material mixture. At this time, the average particle size of the secondary particles of the cobalt compound in the raw material mixture is preferably 0.10 to 0.50 μm, particularly preferably 0.10 to 0.30 μm, and the first lithium compound is mixed with the compound containing the M element used as required by stirring, crushing, etc. Through this mixing, the first lithium compound is easily contacted with the cobalt compound and the compound containing the M element used as required. By having the average particle size of the secondary particles of the cobalt compound in the raw material mixture within the above range, the reactivity of the raw material in the formal firing process can be improved, and even at a low temperature of 500 to 850°C, the reaction can be fully carried out, and the lithium cobalt composite oxide obtained after the formal firing process can be obtained. The weight reduction rate of the lithium cobalt composite oxide after heating at 850°C is 1.5% by mass or less, preferably 1.0% by mass or less, and particularly preferably 0.5% by mass or less. The method of mixing the first lithium compound, the cobalt compound, and the compound containing the M element used as required can be a dry method or a wet method.

[0075] There are no particular restrictions on the method for preparing the raw material mixture, and examples thereof include: (i) before mixing the cobalt compound, the first lithium compound, and the compound containing the M element used as required, the cobalt compound is pulverized to adjust the particle size, and then the pulverized cobalt compound, the first lithium compound, and the compound containing the M element used as required are mixed; (ii) before mixing the cobalt compound, the first lithium compound, and the compound containing the M element used as required, the cobalt compound is pulverized, and the first lithium compound and / or the compound containing the M element are pulverized, and then the pulverized cobalt compound, the first lithium compound, and the compound containing the M element used as required are mixed; (iii) the cobalt compound, the first lithium compound, and the compound containing the M element used as required are mixed, and then they are mixed and pulverized, etc. The pulverization of the cobalt compound, the first lithium compound, or the compound containing the M element, and the mixed pulverization of the cobalt compound, the first lithium compound, and the compound containing the M element used as required can be dry treatment or wet treatment.

[0076] When cobalt hydroxide is used as the cobalt compound in the raw material mixture preparation step, as a method for preparing the raw material mixture, for example, there can be cited: cobalt hydroxide, a first lithium compound, and a compound containing an M element as required are mixed and pulverized to prepare a raw material mixture having an average particle size of 0.10 to 0.50 μm, particularly preferably 0.10 to 0.30 μm for secondary particles of cobalt hydroxide. Cobalt hydroxide usually has a smaller particle size in the form of a single particle, so even if the particle size is not adjusted to be smaller in advance by pulverizing it, a raw material mixture having an average particle size in the above range can be obtained by mixing and pulverizing it with the first lithium compound and a compound containing an M element as required.

[0077] As the apparatus for performing dry pulverization or mixed pulverization, for example, there can be mentioned a jet mill, a pin mill, a roller mill, a ball mill, a bead mill, etc. As the apparatus for performing wet pulverization or mixed pulverization, for example, there can be mentioned a ball mill, a bead mill, etc.

[0078] When the raw material mixture is prepared in a wet process, it is preferred to dry the raw material mixture. The drying method may be a conventional method, but when the pulverization treatment is performed in a wet process, for example, a method using a spray dryer may be used.

[0079] The main firing step is a step of firing the raw material mixture obtained in the raw material mixture preparation step to obtain lithium-cobalt composite oxide particles.

[0080] The firing temperature in the main firing step is 500 to 850°C, preferably 550 to 830°C. When the firing temperature in the main firing step is within the above range, lithium cobalt composite oxide particles having an average primary particle size of 0.50 μm or less, preferably 0.10 to 0.40 μm, and a weight loss rate after heating at 850°C of 1.5 mass% or less, preferably 1.0 mass% or less, and particularly preferably 0.5 mass% or less can be obtained. On the other hand, when the firing temperature in the main firing step is lower than the above range, lithium cobalt composite oxide particles having a weight loss rate after heating at 850°C of 1.5 mass% or less cannot be obtained; and when the firing temperature is higher than the above range, the average primary particle size of the lithium cobalt composite oxide particles exceeds 0.50 μm.

[0081] Furthermore, considering that lithium-cobalt composite oxide particles can be obtained having an average primary particle size of less than 0.50 μm, preferably 0.10 to 0.40 μm, a weight loss rate of less than 1.5 mass % after heating at 850°C, and no impurity phases other than the hexagonal crystalline phase (R-3m) from the lithium-cobalt composite oxide, it is particularly preferred that the firing temperature in the formal firing step is 500 to 850°C, preferably 550 to 830°C.

[0082] The firing time in the formal firing step is 1 to 30 hours, preferably 5 to 20 hours. In addition, the firing atmosphere in the formal firing step is an oxidizing atmosphere such as air or oxygen. In addition, in the formal firing step, the fired product obtained by the first firing can be fired multiple times as needed.

[0083] In the method for producing lithium-cobalt composite oxide particles of the present invention, if necessary, in order to efficiently discharge the decomposition gas generated by the raw material mixture, a pre-firing process can be performed between the raw material mixture preparation process and the main firing process. In this pre-firing process, the raw material mixture obtained by the raw material mixture preparation process is pre-fired at a temperature of 200°C or more and less than 500°C. By performing the pre-firing process, it is easy to obtain the effect of making the reaction in the main firing process more uniform. The pre-firing temperature in the pre-firing process is 200°C or more and less than 500°C, preferably 200-400°C, and more preferably 250-350°C. In addition, the pre-firing time in the pre-firing process is 1-10 hours, preferably 2-5 hours.

[0084] In the method for producing lithium-cobalt composite oxide particles of the present invention, method (A1) can be adopted: after the pre-firing step, the pre-fired product obtained by the pre-firing step is cooled to near room temperature (25°C), and then pulverized, re-mixed, etc. as needed before the formal firing step.

[0085] In the method for producing lithium-cobalt composite oxide particles of the present invention, the method (A2) may be adopted: after the pre-firing step, the pre-firing product obtained by the pre-firing step is not cooled, and the main firing step is performed. For example, in (A2), the raw material mixture obtained by the raw material mixture preparation step is heated to a predetermined pre-firing temperature, and after a predetermined pre-firing time, the heating temperature of the pre-firing product is then increased to a predetermined main firing temperature, and the main firing step is performed.

[0086] In the method for producing lithium-cobalt composite oxide particles of the present invention, by adopting the above-mentioned method (A1), the main firing process can be carried out at a lower temperature compared to the above-mentioned method (A2), and by cooling to near room temperature after the pre-firing process, it becomes possible to carry out crushing, remixing and other treatments, thereby obtaining more uniform lithium-cobalt composite oxide particles.

[0087] In the method for producing lithium-cobalt composite oxide particles of the present invention, by adopting the method (A2), the steps can be simplified compared to the method (A1).

[0088] As to which method to adopt, the method (A1) or the method (A2), it can be appropriately selected in consideration of production equipment and / or industrial advantages.

[0089] In the method for producing lithium-cobalt composite oxide particles of the present invention, a fired product pulverizing step may be performed after the main calcining step as necessary. In the fired product pulverizing step, the lithium-cobalt composite oxide particles obtained by the main calcining step are pulverized.

[0090] The pulverization process in the calcined product pulverization process step may be a dry pulverization process or a wet pulverization process. Examples of wet pulverization devices include ball mills and bead mills. Examples of dry pulverization devices include jet mills, pin mills, roller mills, ball mills, bead mills, and other known pulverization devices.

[0091] The average particle size of the primary particles of the lithium-cobalt composite oxide particles obtained by the method for producing the lithium-cobalt composite oxide particles of the present invention as described above is 0.50 μm or less, preferably 0.10 to 0.40 μm, and the weight loss rate after heating at 850° C. is 1.5 mass % or less, preferably 1.0 mass % or less, and particularly preferably 0.5 mass % or less, so that the positive electrode material can be easily made lighter and thinner, and the battery can be easily miniaturized. In addition, the BET specific surface area of ​​the lithium-cobalt composite oxide particles obtained by the method for producing the lithium-cobalt composite oxide particles of the present invention is preferably 2.0 m 2 / g or more, particularly preferably 3.0 to 15.0 m 2 / g, and the average particle size of the secondary particles is preferably 0.1 to 2.0 μm, particularly preferably 0.2 to 1.0 μm. The BET specific surface area and / or the average particle size of the secondary particles of the lithium-cobalt composite oxide particles obtained by the method for producing lithium-cobalt composite oxide particles of the present invention are within the above ranges, which can easily improve the effect of reducing the weight and thickness of the positive electrode material.

[0092] The lithium-cobalt-based composite oxide particle composition of the present invention is characterized by comprising the lithium-cobalt-based composite oxide particles of the present invention and a second lithium compound.

[0093] The lithium-cobalt-based composite oxide particles of the present invention further contain a second lithium compound in order to further improve sinterability, and a lithium-cobalt-based composite oxide particle composition containing the lithium-cobalt-based composite oxide particles of the present invention and the second lithium compound is obtained.

[0094] The temperature required for sintering the lithium-cobalt composite oxide particles of the present invention is 900°C or higher, but the lithium-cobalt composite oxide particle composition of the present invention mixed with the second lithium compound can be sintered at a temperature lower than 900°C, 700 to 900°C.

[0095] As a method for manufacturing an all-solid-state battery, it is known that in most cases, for example, powders of the materials for the positive electrode layer, the solid electrolyte layer, and the negative electrode layer are made into a paste, applied and dried to make raw sheets, and then such raw sheets are stacked, and the prepared stacked bodies are sintered at a temperature of preferably 700 to 1100°C, preferably 700 to 1100°C, and more preferably below 900°C, and the manufacturing method is manufactured through such a sintering step (refer to paragraphs 0017 to 0022 of Japanese Patent Gazette No. 2015-220099, paragraphs 0017 to 0022 of Japanese Patent Gazette No. 2015-220116, paragraphs 0088 to 0106 of WO2019 / 181909 pamphlet, etc.).

[0096] At this time, in order to improve the lithium ion conductivity in the positive electrode layer, it is necessary to make the positive electrode active material dense. As the positive electrode active material, it is preferred that the primary particles are fine particles and are easily sintered at 900° C. or less.

[0097] The lithium-cobalt composite oxide particle composition of the present invention can be sintered at a low temperature of 900° C. or lower, preferably 700 to 900° C., and is therefore particularly useful as a positive electrode active material powder for all-solid-state batteries.

[0098] The second lithium compound involved in the lithium-cobalt composite oxide particle composition of the present invention can be, for example, lithium carbonate, lithium hydroxide, lithium nitrate, etc. The compound type of the second lithium compound may be the same as or different from the compound type of the first lithium compound. For example, when lithium carbonate is used as the first lithium compound, lithium carbonate may be used as the second lithium compound, or a lithium compound other than lithium carbonate may be used. As the second lithium compound, lithium carbonate, lithium hydroxide, and lithium nitrate are preferred.

[0099] The average particle size of the primary particles of the second lithium compound is the average particle size obtained by observation with a scanning electron microscope (SEM), and is 0.10 to 100.0 μm, preferably 0.10 to 10.0 μm, and more preferably 0.10 to 1.0 μm. In the case where the second lithium compound is lithium carbonate, the average particle size of the primary particles of lithium carbonate as the second lithium compound is preferably 0.10 to 10.0 μm, and more preferably 0.10 to 1.0 μm. From the viewpoint of making it easy to evenly disperse the second lithium compound in the lithium-cobalt composite oxide particle composition and achieving sintering at a lower temperature, the average particle size of the primary particles of the second lithium compound is preferably within the above range.

[0100] In the lithium-cobalt composite oxide particle composition of the present invention, the content of the second lithium compound in terms of lithium atoms is 0.01 to 10.0% by mass, preferably 0.05 to 5.0% by mass, relative to the mass of the lithium-cobalt composite oxide particles. The content of the second lithium compound is preferably within the above range from the viewpoint of achieving sintering at a lower temperature.

[0101] The lithium-cobalt-based composite oxide particle composition of the present invention can be produced, for example, by mixing or co-pulverizing the lithium-cobalt-based composite oxide particles obtained by the above-mentioned method for producing lithium-cobalt-based composite oxide particles of the present invention and a second lithium compound.

[0102] The method for producing the lithium-cobalt-based composite oxide particle composition of the present invention is characterized by comprising a mixing step in which the lithium-cobalt-based composite oxide particles obtained by the method for producing the lithium-cobalt-based composite oxide particles of the present invention and a second lithium compound are mixed or co-pulverized.

[0103] That is, the method for producing the lithium-cobalt composite oxide particle composition of the present invention includes a mixing step, in which the lithium-cobalt composite oxide particles of the present invention obtained by performing a step including the above-mentioned raw material mixture preparation step and the above-mentioned main firing step and the second lithium compound are mixed or mixed and crushed.

[0104] In the mixing step of the method for producing the lithium-cobalt composite oxide particle composition of the present invention, the lithium-cobalt composite oxide particles to be mixed or co-pulverized with the second lithium compound may be:

[0105] 1) obtained by carrying out the above-mentioned raw material mixture preparation step and the above-mentioned main firing step;

[0106] 2) obtained by carrying out the above-mentioned raw material mixture preparation step, the above-mentioned pre-firing step and the above-mentioned main firing step;

[0107] 3) obtained by carrying out the above-mentioned raw material mixing preparation step, the above-mentioned main firing step and the above-mentioned fired product pulverization treatment step;

[0108] 4) obtained by carrying out the above-mentioned raw material mixture preparation step, the above-mentioned preliminary firing step, the above-mentioned main firing step and the above-mentioned fired product pulverization treatment step.

[0109] The mixing step is a step of mixing or pulverizing the second lithium compound and the lithium-cobalt composite oxide particles of the present invention. The mixing or pulverizing mixing in the mixing step includes two cases: a case where the second lithium compound and the lithium-cobalt composite oxide particles of the present invention are simply mixed by mixing means without pulverizing the particles, and a case where a part or all of the particles are pulverized while mixing by mixing or pulverizing mixing means.

[0110] In the mixing step, the second lithium compound and the lithium-cobalt composite oxide particles of the present invention are mixed in such a manner that the content of the second lithium compound in terms of lithium atoms is 0.01 to 10.0% by mass, preferably 0.05 to 5.0% by mass, relative to the mass of the lithium-cobalt composite oxide particles. From the viewpoint of further promoting the sintering reaction and achieving low-temperature sintering, the mixing amount of the second lithium compound is preferably within the above range.

[0111] The average particle size of the primary particles of the second lithium compound in the mixing process is an average particle size obtained by scanning electron microscopy (SEM) observation, preferably 0.10 to 100.0 μm, more preferably 0.10 to 10.0 μm, and further preferably 0.10 to 1.0 μm. From the viewpoint of making it easy to evenly disperse the second lithium compound, further promoting the sintering reaction, and achieving low-temperature sintering, the average particle size of the primary particles of the second lithium compound in the mixing process is preferably within the above range.

[0112] When the second lithium compound is at least one selected from lithium carbonate, lithium hydroxide and lithium nitrate, the average particle size of the second lithium compound is preferably 0.10 to 100.0 μm. When the second lithium compound is lithium carbonate, the average particle size of the second lithium compound is preferably 0.10 to 10.0 μm.

[0113] In the mixing step, the lithium-cobalt composite oxide particles of the present invention and the second lithium compound may be mixed or mixed and pulverized by a dry method or a wet method.

[0114] As a method for mixing or pulverizing and mixing by dry method, there is no particular restriction as long as a uniform mixture can be obtained, for example, methods using a high-speed mixer, a super mixer, a turbine mixer, an EIRICH mixer, a Henschel mixer, a Nauta mixer, a ribbon mixer, a V-type mixer, a conical mixer, a jet mill, a COSMOMIZER, an oil mixer, a bead mill, a ball mill, etc. can be cited. In addition, under laboratory scale, mixing or pulverizing and mixing can be fully carried out by using a desktop mixer. But the mixing or pulverizing and mixing of dry method is not limited to the mixing or pulverizing and mixing using the mechanical means exemplified above.

[0115] As a method for wet mixing or pulverizing and mixing, for example, a method using a ball mill or a stirrer using a stirring wing, a bead mill, a stirrer, a three-roll mill, a dispersion grinder, a homogenizer, a vibration mill, a sand mill, an attritor, and a strong mixer can be cited. Wet mixing or pulverizing and mixing is not limited to mixing or pulverizing and mixing by the mechanical means exemplified above. In addition, from the perspective of being able to obtain a lithium-cobalt composite oxide particle composition with excellent reactivity and uniform dispersion of each component, the slurry after the mixing or pulverizing and mixing is preferably spray-dried.

[0116] Example

[0117] The present invention will be described in more detail below using examples, but the present invention is not limited to these examples.

[0118] <Lithium-cobalt composite oxide particles>

[0119] (1) Weight loss after heating at 850°C

[0120] Calculate it through the following formula.

[0121] Weight reduction rate (%) = ((X-Y) / X) × 100

[0122] X: Mass of lithium-cobalt composite oxide particles before heating at 850° C. (g)

[0123] Y: mass (g) of lithium-cobalt composite oxide particles after heating to 850°C at a heating rate of 100°C / hour, maintaining the temperature at 850°C for 5 hours, and then cooling to room temperature by natural cooling

[0124] (2) Specific surface area of ​​lithium cobalt composite oxide particles

[0125] Calculated by the BET method.

[0126] (3) Average particle size of primary particles of lithium cobalt composite oxide particles

[0127] 100 primary particles were randomly selected by scanning electron microscope (SEM) observation, and the length of the horizontal Feret diameter of each particle was measured. The average value of the 100 particles was determined as the average particle size of the primary particles of the lithium cobalt composite oxide particles.

[0128] (4) Average particle size of secondary particles of lithium cobalt composite oxide particles

[0129] The particle size distribution of the lithium cobalt composite oxide particles was measured by laser scattering / scattering method using water as a measurement solvent. The volume conversion 50% particle size (D50) of the obtained particle size distribution was taken as the average particle size of the secondary particles of the lithium cobalt composite oxide.

[0130] (5) Average particle size of the cobalt compound in the raw material mixture

[0131] The particle size distribution of the raw material mixture was measured by a laser scattering / scattering method using water as a measurement solvent, and the volume-converted 50% particle size (D50) of the obtained particle size distribution was taken as the average particle size of the secondary particles of the cobalt compound in the raw material mixture.

[0132] (6) Crystalline phase

[0133] The measurement was performed using Cu—Kα rays as a radiation source with an X-ray diffractometer (Ultima IV, manufactured by Rigaku Corporation).

[0134] (Examples 1 to 6, Comparative Example 1)

[0135] (Raw material mixture preparation process)

[0136] Cobalt hydroxide (average particle size of primary particles: 0.18 μm, average particle size of secondary particles: 0.20 μm) and lithium carbonate (average particle size of secondary particles: 7.0 μm) were weighed so that the Li / Co ratio reached 1.00, and mixed and crushed in a dry manner using a commercially available desktop mixer to obtain 10.5 g of a raw material mixture with an average particle size of secondary particles of cobalt hydroxide of 0.22 μm.

[0137] (Pre-firing process, main firing process)

[0138] The obtained raw material mixture was pre-calcined at 300°C for 3 hours, then cooled to near room temperature (25°C), re-mixed using a table mixer, and then formally calcined at the calcination temperature shown in Table 1 for 5 hours to obtain lithium cobalt composite oxide particles. The obtained lithium cobalt composite oxide particles were crushed using a table mixer for 30 seconds to obtain lithium cobalt composite oxide particles.

[0139] (Fired product crushing process)

[0140] The obtained lithium cobalt composite oxide particles were subjected to air flow pulverization treatment at a feed rate of 2 g / min using a jet mill (Seishin Enterprise Co., Ltd., A-O jet mill) with P pressure set to 0.65 MPa and J pressure set to 0.60 MPa to obtain lithium cobalt composite oxide particles. The physical properties of the obtained lithium cobalt composite oxide particles are shown in Table 1.

[0141] [Table 1]

[0142]

[0143] According to the results in Table 1, the average particle size of the primary particles of the lithium cobalt composite oxide particles obtained in each example is small, and the weight loss rate after heating at 850° C. is also 1.5 mass % or less. Figure 1 The crystalline phase was confirmed to be a hexagonal single phase.

[0144] The lithium cobalt composite oxide particles obtained in Comparative Example 1 have a small average primary particle size, but a high weight loss rate after heating at 850°C. Figure 1 It was confirmed to be a mixed phase of hexagonal crystals with low crystallinity, cobalt oxide and lithium carbonate.

[0145] (Examples 7 to 10, Comparative Example 2)

[0146] (Raw material mixture preparation process)

[0147] The same method as in Example 1 was used to obtain a raw material mixture.

[0148] (Pre-firing process, main firing process)

[0149] The obtained raw material mixture was pre-calcined for 3 hours at the pre-calcination temperature shown in Table 2. After the pre-calcination time of 3 hours, the mixture was further heated to the main firing temperature shown in Table 2 without cooling, and the mixture was mainly fired for 5 hours at the main firing temperature shown in Table 2 to obtain lithium cobalt composite oxide particles. The obtained lithium cobalt composite oxide particles were crushed for 30 seconds using a table mixer to obtain lithium cobalt composite oxide particles.

[0150] (Fired product crushing process)

[0151] The obtained lithium cobalt composite oxide particles were subjected to air flow milling treatment in the same manner as in Example 1 to obtain lithium cobalt composite oxide particles. Table 2 shows the physical properties of the obtained lithium cobalt composite oxide particles.

[0152] [Table 2]

[0153]

[0154] According to the results in Table 2, the average particle size of the primary particles of the lithium cobalt composite oxide particles obtained in each example is small, and the weight loss rate after heating at 850° C. is also 1.5 mass % or less. Figure 2 It was confirmed that the crystalline phase was also a hexagonal single phase.

[0155] The lithium cobalt composite oxide particles obtained in Comparative Example 2 have a small average primary particle size, but a high weight loss rate after heating at 850°C. Figure 2 It was confirmed to be a mixed phase of hexagonal crystals with low crystallinity, cobalt oxide and lithium carbonate.

[0156] (Comparative Examples 3 to 8)

[0157] (Raw material mixture preparation process)

[0158] Weigh cobalt tetraoxide (average particle size of primary particles 0.58 μm, CV value of primary particle size 0.75, average particle size of secondary particles 2.5 μm) and lithium carbonate (average particle size of secondary particles 7.0 μm) so that the Li / Co ratio reaches 1.00, and use a commercially available desktop mixer to perform dry mixing and pulverization to obtain 10.5 g of a raw material mixture with an average particle size of 1.7 μm for secondary particles of cobalt tetraoxide. Among them, the CV value is an index indicating the deviation of the particle size, which is calculated based on the formula "CV value = standard deviation of particle size / average particle size".

[0159] (Pre-firing process, main firing process)

[0160] The obtained raw material mixture was pre-calcined for 3 hours at the pre-calcination temperature shown in Table 3. After the pre-calcination time of 3 hours, the mixture was further heated to the main firing temperature shown in Table 3 without cooling, and the mixture was formally fired for 5 hours at the main firing temperature shown in Table 3 to obtain lithium cobalt composite oxide particles. The obtained lithium cobalt composite oxide particles were crushed for 30 seconds using a table mixer to obtain lithium cobalt composite oxide particles.

[0161] (Fired product crushing process)

[0162] The obtained lithium cobalt composite oxide particles were subjected to air flow pulverization treatment at a feed rate of 2 g / min using a jet mill (Seishin Enterprise Co., Ltd., A-O jet mill) with a P pressure of 0.65 MPa and a J pressure of 0.60 MPa to obtain lithium cobalt composite oxide fine particles. The physical properties of the obtained lithium cobalt composite oxide particles are shown in Table 3.

[0163] [Table 3]

[0164]

[0165] According to the results in Table 3, when a raw material having a large average particle size of secondary particles of tricobalt tetraoxide in the raw material mixture is used, the average particle size of primary particles of the obtained lithium cobalt composite oxide particles is large. Figure 3 It is judged that if the firing temperature is not increased, the hexagonal single phase crystal phase cannot be obtained.

[0166] (Examples 11 to 13, Comparative Example 9)

[0167] (Raw material mixture preparation process)

[0168] Cobalt hydroxide (average particle size of primary particles 0.22 μm, average particle size of secondary particles 70 μm) and lithium carbonate (average particle size of secondary particles 7.0 μm) were weighed so that the Li / Co ratio was 1.00, and pure water was added to mix them at a slurry concentration of 20 mass %. The mixture was mixed and pulverized in a wet process using a bead mill (LMZ22 manufactured by Ashizawa Finetech Ltd.) using Zr balls to obtain a raw material mixture slurry having an average particle size of 0.21 μm for secondary particles of cobalt hydroxide.

[0169] The obtained raw material mixture slurry was spray dried at a rate of 60 g / min using a spray dryer (L-8 manufactured by Ohgawara Kakoki Co., Ltd.) with an inlet temperature of 250°C and an outlet temperature of 120°C, thereby obtaining 10.5 g of dry powder of the raw material mixture. (Preliminary firing step, main firing step)

[0170] The obtained dry powder of the raw material mixture was pre-calcined for 3 hours at the pre-calcination temperature shown in Table 4. After the pre-calcination time of 3 hours, the temperature was further raised to the main firing temperature shown in Table 4 without cooling, and the main firing was performed for 5 hours at the main firing temperature shown in Table 4 to obtain lithium cobalt composite oxide particles. The obtained lithium cobalt composite oxide particles were crushed for 30 seconds using a table mixer to obtain lithium cobalt composite oxide particles.

[0171] (Fired product crushing process)

[0172] The obtained lithium cobalt composite oxide particles were subjected to air flow pulverization treatment using a jet mill (Seishin Enterprise Co., Ltd., A-O jet mill) at a feed rate of 2 g / min with a P pressure of 0.65 MPa and a J pressure of 0.60 MPa to obtain lithium cobalt composite oxide particles. The physical properties of the obtained lithium cobalt composite oxide particles are shown in Table 4.

[0173] [Table 4]

[0174]

[0175] According to the results in Table 4, the average particle size of the primary particles of the lithium cobalt composite oxide particles obtained in each example is small, and the weight loss rate after heating at 850° C. is also 1.5 mass % or less. Figure 4 It was confirmed that the crystalline phase was also a hexagonal single phase.

[0176] The lithium cobalt composite oxide particles obtained in Comparative Example 9 have a small average primary particle size, but a high weight loss rate after heating at 850°C. Figure 4 , the crystallinity is very low and it is difficult to judge whether it is a hexagonal crystal.

[0177] (Examples 14 to 17)

[0178] (Raw material mixture preparation process)

[0179] Cobalt oxide (average particle size of primary particles: 0.58 μm, CV value of primary particle size: 0.75, average particle size of secondary particles: 2.5 μm) and lithium carbonate (average particle size of secondary particles: 7.0 μm) were weighed so that the Li / Co ratio was 1.00, and pure water was added and mixed at a slurry concentration of 20 mass %. The mixture was mixed and pulverized in a wet process using a bead mill (LMZ22 manufactured by Ashizawa Finetech Ltd.) using Zr balls to obtain a raw material mixture slurry having an average particle size of 0.21 μm for secondary particles of tricobalt tetraoxide.

[0180] The obtained raw material mixture slurry was spray dried at a rate of 60 g / min using a spray dryer (L-8 manufactured by Ohgawara Kakoki Co., Ltd.) with an inlet temperature of 250°C and an outlet temperature of 120°C, thereby obtaining 10.5 g of dry powder of the raw material mixture. (Preliminary firing step, main firing step)

[0181] The obtained dry powder of the raw material mixture was pre-calcined for 3 hours at the pre-calcination temperature shown in Table 5. After the pre-calcination time of 3 hours, the temperature was further raised to the main firing temperature shown in Table 5 without cooling, and the main firing was performed for 5 hours at the main firing temperature shown in Table 5 to obtain lithium cobalt composite oxide particles. The obtained lithium cobalt composite oxide particles were crushed for 30 seconds using a table mixer to obtain lithium cobalt composite oxide particles.

[0182] (Fired product crushing process)

[0183] The obtained lithium cobalt composite oxide particles were subjected to air flow pulverization treatment using a jet mill (Seishin Enterprise Co., Ltd., A-O jet mill) at a feed rate of 2 g / min with a P pressure of 0.65 MPa and a J pressure of 0.60 MPa to obtain lithium cobalt composite oxide particles. The physical properties of the obtained lithium cobalt composite oxide particles are shown in Table 5.

[0184] [Table 5]

[0185]

[0186] According to the results in Table 5, the average particle size of the primary particles of the lithium cobalt composite oxide particles obtained in each example is small, and the weight loss rate after heating at 850° C. is also 1.5 mass % or less. Figure 5 It was confirmed that the crystalline phase was also a hexagonal single phase.

[0187] <Lithium-cobalt composite oxide particle composition>

[0188] (1) Average particle size of primary particles of raw material lithium carbonate

[0189] According to the scanning electron microscope (SEM) observation, 100 primary particles were randomly selected, the length of the horizontal Feret diameter of each particle was measured, and the average value of the 100 particles was calculated as the average particle size of the primary particles of lithium carbonate.

[0190] (2) Sintering test

[0191] 0.5 g of lithium cobalt composite oxide particles or 0.5 g of a lithium cobalt composite oxide particle composition obtained by mixing lithium cobalt composite oxide particles with a second lithium compound was subjected to a test at 5 kN / cm 2 The pressure forming The obtained compact was fired at 700°C or 800°C for 5 hours to obtain a sintered body. The following formula was used to calculate the bulk density (g / cm2) of the sintered body according to the weight, thickness and diameter of the sintered body: 3 ) = weight of sintered body / ((diameter of sintered body×0.5) 2The bulk density of the sintered body was calculated by

[0192] Furthermore, a sintered body was obtained by firing at 900°C for 5 hours, and the volume density and increase / decrease of the sintered body at 800°C were checked to confirm the sintering temperature.

[0193] (Example 18)

[0194] (Raw material mixture preparation step, preliminary firing step, main firing step, fired product pulverization step)

[0195] The same method as in Example 4 was followed to obtain lithium-cobalt composite oxide particles.

[0196] (Mixing process)

[0197] The obtained lithium cobalt composite oxide particles and lithium carbonate (average particle size of primary particles: 7.0 μm) were weighed so that the lithium atom content of the lithium carbonate reached 2.0% by mass relative to the mass of the lithium cobalt composite oxide particles, and mixed and pulverized in a dry manner using a desktop mixer to obtain a lithium cobalt composite oxide particle composition.

[0198] (Sintering test)

[0199] The lithium cobalt composite oxide particle composition obtained in Example 18 was used to perform a sintering test, and the bulk density of the sintered body was calculated. The results are shown in Table 6. Since the bulk density of the sintered body hardly changed between 800°C and 900°C, it was confirmed that the sintering temperature was 800°C.

[0200] (Example 19)

[0201] (Raw material mixture preparation step, preliminary firing step, main firing step, fired product pulverization step)

[0202] The same method as in Example 4 was followed to obtain lithium-cobalt composite oxide particles.

[0203] (Crushing of lithium carbonate)

[0204] Pure water was added to lithium carbonate (average primary particle size 7.0 μm) to a slurry concentration of 20% by mass, and the slurry was prepared by using The Zr ball bead mill (LMZ22 manufactured by Ashizawa Finetech Ltd.) was wet mixed and crushed to obtain lithium carbonate slurry. The lithium carbonate slurry was spray dried at an input rate of 60 g / min using a spray dryer (L-8 manufactured by Ohgawara Chemical Industry Co., Ltd.) with the inlet temperature set to 250°C and the outlet temperature set to 120°C. The jet mill (A-O jet mill manufactured by Seishin Enterprise Co., Ltd.) was used to set the P pressure to 0.65 MPa and the J pressure to 0.60 MPa, and the jet mill was crushed at an input rate of 2 g / min to obtain lithium carbonate particles with an average particle size of 0.48 μm for the primary particles.

[0205] (Mixing process)

[0206] The obtained lithium carbonate (average particle size of primary particles: 0.48 μm) and the obtained lithium cobalt composite oxide particles were weighed so that the lithium atom content of the lithium carbonate reached 2.0% by mass relative to the mass of the lithium cobalt composite oxide particles, and mixed and pulverized them in a dry manner using a desktop mixer to obtain a lithium cobalt composite oxide particle composition.

[0207] (Sintering test)

[0208] The lithium cobalt composite oxide particle composition obtained in Example 19 was used to perform a sintering test, and the bulk density of the sintered body was calculated. The results are shown in Table 6. Since the bulk density of the sintered body hardly changed between 800°C and 900°C, it was confirmed that the sintering temperature was 800°C.

[0209] (Example 20)

[0210] (Raw material mixture preparation step, preliminary firing step, main firing step, fired product pulverization step)

[0211] The same method as in Example 4 was followed to obtain lithium-cobalt composite oxide particles.

[0212] (Crushing of lithium carbonate)

[0213] Pure water was added to lithium carbonate (average primary particle size 7.0 μm) to a slurry concentration of 20% by mass, and the slurry was prepared by using The mixture was mixed and pulverized in a wet process using a bead mill (LMZ22 manufactured by Ashizawa Finetech Ltd.) using Zr balls to obtain lithium carbonate slurry having an average primary particle size of 0.36 μm.

[0214] (Mixing process)

[0215] The obtained lithium carbonate slurry, the obtained lithium cobalt composite oxide particles and pure water are mixed in such a manner that the content of lithium carbonate in the solid component in terms of lithium atoms is 2.0% by mass relative to the mass of the lithium cobalt composite oxide particles and the slurry concentration is 20% by mass. Next, a spray dryer (L-8 manufactured by Ohgawara Chemical Industry Co., Ltd.) is used, the inlet temperature is set to 250°C, the outlet temperature is set to 120°C, and spray drying is performed at an input rate of 60 g / min to obtain a dry powder of the mixture. A jet mill (A-O jet mill manufactured by Seishin Enterprise Co., Ltd.) is used, the P pressure is set to 0.65 MPa, the J pressure is set to 0.60 MPa, and the obtained dry powder is subjected to air flow pulverization treatment at an input rate of 2 g / min to obtain a lithium cobalt composite oxide particle composition.

[0216] (Sintering test)

[0217] The lithium cobalt composite oxide particle composition obtained in Example 20 was used to perform a sintering test, and the bulk density of the sintered body was calculated. The results are shown in Table 6. Since the bulk density of the sintered body hardly changed between 800°C and 900°C, it was confirmed that the sintering temperature was 800°C.

[0218] (Example 21)

[0219] (Raw material mixture preparation step, preliminary firing step, main firing step, fired product pulverization step)

[0220] The same method as in Example 4 was followed to obtain lithium-cobalt composite oxide particles.

[0221] (Mixing process)

[0222] The obtained lithium cobalt composite oxide particles and lithium carbonate (average particle size of primary particles: 7.0 μm) were weighed so that the lithium atom content of lithium carbonate relative to the mass of the lithium cobalt composite oxide particles was 0.50% by mass, and mixed and pulverized in a dry manner using a desktop mixer to obtain lithium cobalt composite oxide particles.

[0223] (Sintering test)

[0224] The lithium-cobalt composite oxide particle composition obtained in Example 21 was used to carry out a sintering test, and the bulk density of the sintered body was calculated. The results are shown in Table 6.

[0225] (Example 22)

[0226] (Raw material mixture preparation step, preliminary firing step, main firing step, fired product pulverization step)

[0227] The same method as in Example 4 was followed to obtain lithium-cobalt composite oxide particles.

[0228] (Add Mixing Method)

[0229] The obtained lithium cobalt composite oxide particles and lithium hydroxide (average particle size of primary particles: 25.0 μm) were weighed so that the lithium atom content of the lithium hydroxide was 0.50% by mass relative to the mass of the lithium cobalt composite oxide particles, and mixed and pulverized in a dry manner using a desktop mixer to obtain a lithium cobalt composite oxide particle composition.

[0230] (Sintering test)

[0231] The lithium-cobalt composite oxide particle composition obtained in Example 22 was used to carry out a sintering test, and the bulk density of the sintered body was calculated. The results are shown in Table 6.

[0232] (Example 23)

[0233] (Raw material mixture preparation step, preliminary firing step, main firing step, fired product pulverization step)

[0234] The same method as in Example 4 was followed to obtain lithium-cobalt composite oxide particles.

[0235] (Add Mixing Method)

[0236] The obtained lithium cobalt composite oxide particles and lithium nitrate (average particle size of primary particles: 65 μm) were weighed so that the lithium atom content of the lithium nitrate reached 0.50% by mass relative to the mass of the lithium cobalt composite oxide particles, and mixed and pulverized in a dry manner using a desktop mixer to obtain a lithium cobalt composite oxide particle composition.

[0237] (Sintering test)

[0238] The lithium-cobalt composite oxide particle composition obtained in Example 23 was used to carry out a sintering test, and the bulk density of the sintered body was calculated. The results are shown in Table 6.

[0239] The relative density in Table 6 is the theoretical density of the lithium cobalt composite oxide particle composition of 5.1 g / cm 3 Relative value when set to 100%.

[0240] [Table 6]

[0241]

[0242] According to the results in Table 6, the sintered bodies obtained when the lithium cobalt composite oxide particle compositions mixed with lithium carbonate obtained in Examples 18 to 20 were fired at 700°C had a higher bulk density than the sintered bodies obtained when the lithium cobalt composite oxide particles obtained in Example 4 were fired at 700°C. In addition, the sintered bodies obtained when the lithium cobalt composite oxide particle compositions mixed with lithium carbonate obtained in Examples 18 to 20 were fired at 800°C had a higher bulk density than the sintered bodies obtained when the lithium cobalt composite oxide particles obtained in Example 4 were fired at 800°C. By comparing the lithium cobalt composite oxide particle compositions and the lithium cobalt composite oxide particles, it was confirmed that the sintering reaction further progressed and the sinterability was improved when the lithium cobalt composite oxide particle compositions were fired at 700°C and 800°C. In addition, there was almost no difference between the bulk density of the lithium cobalt composite oxide particle compositions at 900°C and the bulk density at 800°C, thus confirming that sintering was possible even at a low temperature of about 800°C.

[0243] Moreover, according to the results in Table 6, the sintered body obtained when the lithium cobalt composite oxide particle composition mixed with lithium carbonate obtained in Example 21 was fired at 700°C, the sintered body obtained when the lithium cobalt composite oxide particle composition mixed with lithium hydroxide obtained in Example 22 was fired at 700°C, and the sintered body obtained when the lithium cobalt composite oxide particle composition mixed with lithium nitrate obtained in Example 23 was fired at 700°C all have higher volume density than the sintered body obtained when the lithium cobalt composite oxide particles obtained in Example 4 were fired at 700°C.

Claims

1. A lithium-cobalt composite oxide particle, characterized in that: The average particle size of the primary particles of the lithium-cobalt composite oxide is 0.50 μm or less. The weight reduction rate after heating at 850° C. was 1.5 mass % or less.

2. The lithium-cobalt composite oxide particles according to claim 1, characterized in that: BET specific surface area is 2.0m 2 / g or above.

3. The lithium-cobalt composite oxide particles according to claim 1 or 2, characterized in that: The average particle size of the secondary particles of the lithium-cobalt composite oxide is 0.10 to 2.00 μm.

4. The lithium-cobalt composite oxide particles according to claim 1 or 2, characterized in that: In the X-ray diffraction analysis, no impurity phase other than the hexagonal crystal phase (R-3m) derived from the lithium-cobalt composite oxide was found.

5. The lithium-cobalt composite oxide particles according to claim 1 or 2, characterized in that: The lithium-cobalt composite oxide particles are obtained by a solid phase method.

6. A method for producing lithium-cobalt composite oxide particles, characterized in that: include: a raw material mixture preparation step of preparing a raw material mixture containing at least a cobalt compound and a first lithium compound, wherein the average particle size of secondary particles of the cobalt compound is 0.10 to 0.50 μm; and The main firing step is to fire the raw material mixture at 500 to 850°C.

7. The method for producing lithium-cobalt composite oxide particles according to claim 6, wherein: The cobalt compound is at least one selected from the group consisting of hydroxide, oxide, carbonate, oxyhydroxide, nitrate, sulfate and organic acid salt of cobalt.

8. The method for producing lithium-cobalt composite oxide particles according to claim 6 or 7, wherein: The first lithium compound is at least one selected from the group consisting of lithium carbonate, lithium hydroxide, lithium acetate and lithium nitrate.

9. The method for producing lithium-cobalt composite oxide particles according to claim 6 or 7, wherein: A pre-firing step is performed between the raw material mixture preparation step and the main firing step. In the pre-firing step, the raw material mixture is pre-firing at a temperature of 200° C. or higher and lower than 500° C.

10. The method for producing lithium-cobalt composite oxide particles according to claim 9, wherein: After the pre-firing step, the pre-firing product is cooled, and then the main-firing step is performed.

11. The method for producing lithium-cobalt composite oxide particles according to claim 9, wherein: After the pre-firing step, the main firing step is performed without cooling the pre-firing product.

12. The method for producing lithium-cobalt composite oxide particles according to claim 6 or 7, wherein: After the main firing step, a fired product pulverizing step is performed. In the fired product pulverizing step, the lithium-cobalt composite oxide particles obtained by the main firing step are pulverized.

13. The method for producing lithium-cobalt composite oxide particles according to claim 12, wherein: In the fired product pulverization treatment step, the lithium-cobalt composite oxide particles are pulverized by air flow pulverization.

14. A lithium-cobalt composite oxide particle composition, characterized in that: The invention comprises the lithium-cobalt composite oxide particles according to claim 1 or 2 and a second lithium compound.

15. A method for producing a lithium-cobalt composite oxide particle composition, characterized in that: The method comprises a mixing step of mixing or co-pulverizing the lithium-cobalt-based composite oxide particles obtained by the method for producing lithium-cobalt-based composite oxide particles according to any one of claims 6 to 13 and a second lithium compound.

16. The method for producing a lithium-cobalt composite oxide particle composition according to claim 15, wherein: The second lithium compound is at least one selected from the group consisting of lithium carbonate, lithium hydroxide and lithium nitrate.

17. The method for producing a lithium-cobalt composite oxide particle composition according to claim 15 or 16, wherein: The average particle size of primary particles of the second lithium compound is 0.10 to 100.0 μm.

18. The method for producing a lithium-cobalt composite oxide particle composition according to claim 15, wherein: The second lithium compound is lithium carbonate having an average primary particle size of 0.10 to 10.0 μm.

19. The method for producing a lithium-cobalt composite oxide particle composition according to claim 15, wherein: In the mixing step, the second lithium compound and the lithium-cobalt-based composite oxide particles are mixed such that the lithium atom-equivalent content of the second lithium compound is 0.01 to 10.0 mass % based on the mass of the lithium-cobalt-based composite oxide particles.

20. The method for producing a lithium-cobalt composite oxide particle composition according to claim 15, wherein: In the mixing step, a mixing treatment or a mixing and pulverizing treatment is performed in a dry or wet manner.

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