Nickel composite hydroxide particles, a positive electrode active material using the nickel composite hydroxide particles as a precursor, and a method for producing the positive electrode active material

Abstract

The present invention provides a precursor of a positive electrode active material capable of obtaining a positive electrode active material, the positive electrode active material obtained from the precursor, and a method for manufacturing the positive electrode active material. The positive electrode active material can exhibit a high discharge capacity and a high charge-discharge efficiency when mounted in a secondary battery using a non-aqueous electrolyte. A nickel composite hydroxide particle, which is a precursor of a positive electrode active material of a non-aqueous electrolyte secondary battery, has a porosity of 45.0% or more and 55.0% or less.

Description

Technical Field

[0001] The present invention relates to nickel composite hydroxide particles, a positive electrode active material using the nickel composite hydroxide particles as a precursor, and a method for manufacturing the positive electrode active material, and more particularly to nickel composite hydroxide particles, a positive electrode active material using the nickel composite hydroxide particles as a precursor, and a method for manufacturing the positive electrode active material, which can provide a non-aqueous electrolyte secondary battery having excellent discharge capacity and charge-discharge efficiency. Background Art

[0002] In recent years, from the viewpoint of reducing the environmental load, secondary batteries are used in a wide range of fields such as portable devices and vehicles that use electric power or use electric power as a power source. As the secondary battery, for example, there is a secondary battery using a non-aqueous electrolyte such as a lithium ion secondary battery. A secondary battery using a non-aqueous electrolyte such as a lithium ion secondary battery is suitable for miniaturization and weight reduction, and has excellent characteristics such as high cycle characteristics and high rate characteristics.

[0003] In addition, in order to further improve the cycle characteristics and rate characteristics, a method has been proposed to increase the packing density of the positive electrode active material mounted on the positive electrode, or even to increase the tap density of the composite hydroxide particles as the precursor of the positive electrode active material. In order to increase the tap density of the composite hydroxide particles, it is effective to increase the roundness of the composite hydroxide particles. Therefore, a composite compound containing nickel and manganese having a tap density of 1.9 g / cm 3 or more and an average roundness of 0.960 or more has been proposed (Patent Document 1).

[0004] Regarding the composite compound of Patent Document 1, although a positive electrode active material having excellent cycle characteristics and rate characteristics can be obtained by increasing the tap density and roundness, there is room for improvement in other characteristics required for the positive electrode active material, that is, discharge capacity and charge-discharge efficiency.

[0005] Prior Art Documents

[0006] Patent Documents

[0007] Patent Document 1: WO 2014 / 175191 Summary of the Invention

[0008] Problems to be Solved by the Invention

[0009] In view of the above circumstances, an object of the present invention is to provide a precursor of a positive electrode active material capable of obtaining a positive electrode active material, the positive electrode active material obtained from the precursor, and a method for manufacturing the positive electrode active material, the positive electrode active material being capable of exhibiting a high discharge capacity and a high charge-discharge efficiency when mounted on a secondary battery using a non-aqueous electrolyte.

[0010] Means for Solving the Problems

[0011] The gist of the constitution of the present invention is as follows.

[0012] [1] A nickel composite hydroxide particle, which is a precursor of a positive electrode active material for a non-aqueous electrolyte secondary battery, wherein the porosity of the nickel composite hydroxide particle is 45.0% or more and 55.0% or less.

[0013] [2] A nickel composite hydroxide particle, which is a precursor of a positive electrode active material for a non-aqueous electrolyte secondary battery, wherein the average circularity of the nickel composite hydroxide particle is 0.85 or more and 0.94 or less.

[0014] [3] The nickel composite hydroxide particle according to [1], wherein the average circularity of the nickel composite hydroxide particle is 0.85 or more and 0.94 or less.

[0015] [4] The nickel composite hydroxide particle according to any one of [1] to [3], wherein the particle diameter (D50) at a cumulative volume percentage of 50% by volume of the nickel composite hydroxide particle is 5.0 μm or more and 25.0 μm or less.

[0016] [5] The nickel composite hydroxide particle according to any one of [1] to [4], wherein the nickel composite hydroxide particle contains Ni, Co, and one or more additive metal elements M selected from the group consisting of Mn, Al, Ca, Ti, V, Cr, Zr, Nb, Mo, and W, and the molar ratio of Ni:Co:M is 1 - x - y:x:y (0 < x ≤ 0.2, 0 < y ≤ 0.1).

[0017] [6] A positive electrode active material for a non-aqueous electrolyte secondary battery, which is obtained by firing the nickel composite hydroxide particle according to any one of [1] to [5] and a lithium compound.

[0018] [7] A method for manufacturing a positive electrode active material for a non-aqueous electrolyte secondary battery, which includes: a step of obtaining a mixture by adding a lithium compound to the nickel composite hydroxide particle according to any one of [1] to [5], or a step of preparing nickel composite oxide particles by subjecting the nickel composite hydroxide particle according to any one of [1] to [5] to an oxidation treatment, and then adding a lithium compound to obtain a mixture of the lithium compound and the nickel composite oxide particles; and a step of firing the mixture.

[0019] In the method of [1], the "void fraction" (unit: %) represents the value calculated as follows: A specified amount of nickel composite hydroxide particles are filled into a container (cell) with a certain volume, and compressed at a pressure of 21.2 MPa, thereby measuring the compressed volume (V) of the nickel composite hydroxide particles. The void fraction is calculated by [V - mass of the composite hydroxide particles × (1 / d)] / V × 100 (%) using the true density (d) of the nickel composite hydroxide particles. As an example, using the powder compressor, which is an accessory of the high-precision surface tension meter DY-700 (manufactured by Kyowa Interface Science Co., Ltd.), 6.5 g of nickel composite hydroxide particles are filled into a container with a diameter of 10 mm and a height of 100 mm (volume: 7.85 ml), and compressed at a pressure of 21.2 MPa, whereby the compressed volume (V) can be measured. In addition, the true density (d) is the value measured using a gas displacement type dry automatic densitometer.

[0020] In the method of [2], the circularity is an index of sphericity when the nickel composite hydroxide particles are two-dimensionally projected. The "circularity" in this specification represents the value calculated as follows: The nickel composite hydroxide particles, which are the measurement objects, are individually photographed using a CCD camera or the like, and calculated based on the circumference of a circle having the same area as the particle image / the circumference of the particle image. As a device for the above measurement, for example, the wet fluid type particle size / shape analysis device "FPIA-3000S" (manufactured by Sysmex Corporation) can be cited. In addition, the "average circularity" in this specification represents the average value calculated by analyzing the circularity based on the number.

[0021] Effects of the Invention

[0022] According to the method of the present invention, the void fraction is 45.0% or more and 55.0% or less, and thus by mounting a positive electrode active material using this nickel composite hydroxide as a precursor on a secondary battery, high discharge capacity and high charge-discharge efficiency can be exhibited.

[0023] According to the method of the present invention, the average circularity of the nickel composite hydroxide particles is 0.85 or more and 0.94 or less, and thus by mounting a positive electrode active material using this nickel composite hydroxide as a precursor on a secondary battery, high discharge capacity and high charge-discharge efficiency can be exhibited.

[0024] According to the method of the present invention, the void fraction is 45.0% or more and 55.0% or less and the average circularity of the nickel composite hydroxide particles is 0.85 or more and 0.94 or less, and thus by mounting a positive electrode active material using these nickel composite hydroxide particles as a precursor on a secondary battery, the discharge capacity and the charge-discharge efficiency can be further improved. Detailed Embodiments

[0025] Hereinafter, the nickel composite hydroxide particles, which are the precursor of the positive electrode active material of the non-aqueous electrolyte secondary battery of the present invention, will be described in detail. The porosity of the nickel composite hydroxide particles, which are the precursor of the positive electrode active material of the non-aqueous electrolyte secondary battery of the present invention (hereinafter, sometimes simply referred to as "the nickel composite hydroxide particles of the present invention"), is 45.0% or more and 55.0% or less. When the nickel composite hydroxide particles of the present invention are filled, the shape of the nickel composite hydroxide particles can be adjusted so that a predetermined amount of voids are formed between the nickel composite hydroxide particles.

[0026] Since the porosity of the nickel composite hydroxide particles of the present invention is 45.0% or more and 55.0% or less, a non-aqueous electrolyte secondary battery can be imparted with a high discharge capacity and a high charge-discharge efficiency. Regarding the type of equipment for compressing the powder used for calculating the above porosity, as long as it is equipment that can compress the nickel composite hydroxide particles of the present invention accommodated in a container with a certain volume at a pressure of 21.2 MPa, it is not particularly limited. For example, a powder compressor (manufactured by Kyowa Interface Science Co., Ltd.) which is an accessory of a high-precision surface tensiometer DY-700 can be cited.

[0027] In the present invention, as long as the porosity is in the range of 45.0% or more and 55.0% or less, it is not particularly limited. From the viewpoint of further improving the discharge capacity and the charge-discharge efficiency, its lower limit value is preferably 46.0% or more. On the other hand, from the viewpoint of maintaining the loading density of the positive electrode active material on the positive electrode without impairing other characteristics of the positive electrode active material such as the cycle characteristics and further improving the discharge capacity and the charge-discharge efficiency, the upper limit value of the above porosity is preferably 53.0% or less, and particularly preferably 52.0% or less. In addition, the above upper limit value and lower limit value can be arbitrarily combined.

[0028] As described above, regarding the nickel composite hydroxide particles of the present invention, the shape of the nickel composite hydroxide particles is adjusted to have the above porosity. The shape of the nickel composite hydroxide particles of the present invention has an average circularity of 0.85 or more and 0.94 or less, for example. Therefore, the nickel composite hydroxide particles of the present invention have a shape with a lower circularity compared to conventional precursors.

[0029] Since the average circularity of the nickel composite hydroxide particles of the present invention is 0.85 or more and 0.94 or less, a non-aqueous electrolyte secondary battery can be imparted with a high discharge capacity and a high charge-discharge efficiency.

[0030] The average circularity of the nickel composite hydroxide particles of the present invention is not particularly limited as long as it is in the range of 0.85 or more and 0.94 or less. From the viewpoint of maintaining the loading density of the positive electrode active material on the positive electrode so as not to impair other characteristics of the positive electrode active material such as the cycle characteristics and further improving the discharge capacity and charge-discharge efficiency, the lower limit value is preferably 0.87 or more, and particularly preferably 0.89 or more. On the other hand, from the viewpoint of further improving the discharge capacity and charge-discharge efficiency, the upper limit value of the average circularity is preferably 0.92 or less, and particularly preferably 0.91 or less. In addition, the above upper limit value and lower limit value can be arbitrarily combined.

[0031] As the components of the nickel composite hydroxide particles of the present invention, for example, a composite hydroxide containing nickel (Ni), cobalt (Co), and one or more additive metal elements M selected from the group consisting of manganese (Mn), aluminum (Al), calcium (Ca), titanium (Ti), vanadium (V), chromium (Cr), zirconium (Zr), niobium (Nb), molybdenum (Mo), and tungsten (W) can be cited. That is, in the above nickel composite hydroxide particles, Ni and Co are contained as essential metal components, and further, one or more metal elements of Mn, Al, Ca, Ti, V, Cr, Zr, Nb, Mo, and W are contained as the additive metal element (M).

[0032] The molar ratio of Ni:Co:M is not particularly limited and can be appropriately selected according to the use conditions of the positive electrode active material obtained from the nickel composite hydroxide particles. The molar ratio of Ni:Co:M can be, for example, 1 - x - y:x:y (0 < x ≤ 0.2, 0 < y ≤ 0.1). As the additive metal element, from the viewpoint of further improving the discharge capacity and charge-discharge efficiency, it is preferably to contain Al and Mn, and particularly preferably Al.

[0033] The nickel composite hydroxide particles of the present invention are secondary particles formed by aggregation of a plurality of primary particles. The particle size of the nickel composite hydroxide particles of the present invention is not particularly limited. For example, from the viewpoint of increasing the density, the lower limit value of the particle size at a cumulative volume percentage of 50% by volume (hereinafter, sometimes simply referred to as "D50") is preferably 5.0 μm or more, and particularly preferably 8.0 μm or more. On the other hand, from the viewpoint of improving the contact with the non-aqueous electrolyte, the upper limit value of D50 of the nickel composite hydroxide particles of the present invention is preferably 25.0 μm or less, and particularly preferably 20.0 μm or less. In addition, the above upper limit value and lower limit value can be arbitrarily combined.

[0034] Further, from the viewpoint of increasing the density, the lower limit of the particle diameter at which the cumulative volume percentage of the nickel composite hydroxide particles of the present invention is 90% by volume (hereinafter sometimes simply referred to as "D90") is preferably 10.0 μm or more, particularly preferably 15.0 μm or more. On the other hand, from the viewpoint of improving the contact with the non-aqueous electrolyte, the upper limit of D90 of the nickel composite hydroxide particles of the present invention is preferably 40.0 μm or less, particularly preferably 35.0 μm or less. In addition, the above upper and lower limits can be arbitrarily combined. Further, from the viewpoint of increasing the density, the lower limit of the particle diameter at which the cumulative volume percentage of the nickel composite hydroxide particles of the present invention is 10% by volume (hereinafter sometimes simply referred to as "D10") is preferably 1.0 μm or more, particularly preferably 5.0 μm or more. On the other hand, from the viewpoint of improving the contact with the non-aqueous electrolyte, the upper limit of D10 of the nickel composite hydroxide particles of the present invention is preferably 15.0 μm or less, particularly preferably 10.0 μm or less. In addition, the above upper and lower limits can be arbitrarily combined. In addition, D10, D50, and D90 represent the particle diameters measured by a particle size distribution measuring device using the laser diffraction scattering method.

[0035] In addition, the particle size distribution width of the nickel composite hydroxide particles of the present invention is not particularly limited and can be appropriately selected according to the use conditions of the positive electrode active material, etc. For example, from the viewpoint of increasing the loading density of the positive electrode active material, the lower limit of (D90 - D10) / D50 is preferably 0.40 or more, more preferably 0.50 or more, particularly preferably 0.70 or more. On the other hand, regardless of the size of the particle diameter of the nickel composite hydroxide particles, from the viewpoint of balancing the various characteristics of the positive electrode active material, the upper limit of (D90 - D10) / D50 of the nickel composite hydroxide particles of the present invention is preferably 1.10 or less, particularly preferably 1.00 or less. In addition, the above upper and lower limits can be arbitrarily combined.

[0036] The BET specific surface area of the nickel composite hydroxide particles of the present invention is not particularly limited. For example, from the viewpoint of increasing the filling degree of the positive electrode active material into the positive electrode and the contact area with the non-aqueous electrolyte, its lower limit is preferably 30 m 2 / g or more, particularly preferably 35 m 2 / g or more. On the other hand, from the viewpoint of increasing the crushing strength of the positive electrode active material, the upper limit of the BET specific surface area of the nickel composite hydroxide particles of the present invention is preferably 60 m 2 / g or less, particularly preferably 50 m 2 / g or less. In addition, the above upper and lower limits can be arbitrarily combined.

[0037] Next, the manufacturing method of the nickel composite hydroxide particles of the present invention will be described. First, by the coprecipitation method, a solution containing metal salts, such as a solution containing a nickel salt (e.g., sulfate), a cobalt salt (e.g., sulfate), and a salt of an added metal element (e.g., sulfate), a complexing agent, and a pH adjuster are appropriately added, and they are made to undergo a neutralization reaction in a reaction tank to prepare crude nickel composite hydroxide particles and obtain a slurry-like suspension containing the crude nickel composite hydroxide particles. As the solvent of the suspension, for example, water is used.

[0038] As the complexing agent, as long as it can form a complex with metal element ions, such as nickel, cobalt, and added metal element ions, in an aqueous solution, there is no particular limitation, and for example, an ammonium ion donor can be cited. As the ammonium ion donor, for example, ammonia water, ammonium sulfate, ammonium chloride, ammonium carbonate, ammonium fluoride, etc. can be cited. In addition, during the neutralization reaction, an alkali metal hydroxide (e.g., sodium hydroxide, potassium hydroxide) can be added as a pH adjuster as needed to adjust the pH value of the aqueous solution.

[0039] If the above metal salt solution, pH regulator, and ammonium ion donor are appropriately and continuously supplied to the reaction tank and the substances in the reaction tank are appropriately stirred, the metals (such as nickel, cobalt, and added metal elements) in the metal salt solution undergo a coprecipitation reaction to prepare crude nickel composite hydroxide particles. During the coprecipitation reaction, for example, the temperature of the reaction tank is controlled to be 10°C to 80°C, preferably in the range of 20 to 70°C. When the pH regulator and ammonium ion donor are supplied to the reaction tank and a coprecipitation reaction occurs, the ammonia concentration in the mixed solution in the reaction tank and the pH at a reference liquid temperature of 40°C are controlled within a specified range, and the stirring speed and residence time of the stirring device provided in the reaction tank are adjusted to a specified range, whereby the porosity between the nickel composite hydroxide particles can be adjusted to be 45.0% or more and 55.0% or less, and the average circularity of the nickel composite hydroxide particles can be adjusted to be 0.85 or more and 0.94 or less. The preferred range of the ammonia concentration and the pH at a reference liquid temperature of 40°C sometimes needs to be adjusted according to the composition of the crude nickel composite hydroxide particles. For example, the ammonia concentration is preferably less than 12.0 g / L, particularly preferably 7.0 g / L or more and 11.0 g / L or less. In addition, the pH at a reference liquid temperature of 40°C is preferably 11.0 or more and 12.5 or less, particularly preferably 11.5 or more and 12.3 or less. In addition, since the shear force applied to the particles varies depending on the volume of the reaction tank, the type of stirring blade, and the residence time, it is necessary to appropriately adjust the stirring speed of the stirring device. For example, when using three propeller-type blades for a reaction tank with a volume of 15 L and a coprecipitation reaction occurs within a residence time of 5 to 10 hours, the stirring speed is preferably 1000 rpm or more and 1500 rpm or less, particularly preferably 1100 rpm or more and 1400 rpm or less.

[0040] As a stirring device for the method for manufacturing nickel composite hydroxide particles of the present invention, for example, a stirring device having the following stirring blades can be cited, and the stirring blades have a plurality of propeller-type blades at the front end of the stirring shaft. In addition, as a reaction tank for the method for manufacturing nickel composite hydroxide particles of the present invention, for example, a continuous type in which the obtained crude nickel composite hydroxide particles are made to overflow for separation and an intermittent type in which no discharge to the outside of the system is performed until the reaction ends can be cited.

[0041] As described above, after filtering the crude nickel composite hydroxide particles obtained through the neutralization reaction step from the suspension, they are washed with an aqueous alkali solution to remove the impurities contained in the crude nickel composite hydroxide particles, and refined nickel composite hydroxide particles (the nickel composite hydroxide particles of the present invention) are obtained. Then, solid-liquid separation is carried out, and if necessary, the solid phase containing the nickel composite hydroxide particles is washed with water, and the nickel composite hydroxide particles are heat-treated to be dried, whereby powdery nickel composite hydroxide particles can be obtained.

[0042] Next, the positive electrode active material of the non-aqueous electrolyte secondary battery using the nickel composite hydroxide particles of the present invention as a precursor (hereinafter, sometimes simply referred to as "the positive electrode active material of the present invention") will be described. Regarding the positive electrode active material of the present invention, the nickel composite hydroxide particles of the present invention as a precursor are, for example, in a form after firing with a lithium compound. The crystal structure of the positive electrode active material of the present invention is a layered structure, and from the viewpoint of obtaining a secondary battery with a high discharge capacity, a hexagonal crystal structure or a monoclinic crystal structure is more preferable. The positive electrode active material of the present invention can be used, for example, as the positive electrode active material of a lithium ion secondary battery. In addition, when manufacturing the positive electrode active material of the present invention, a step of preparing nickel composite hydroxide particles into nickel composite oxide particles can be carried out in advance. As a method for preparing nickel composite oxide particles from nickel composite hydroxide particles, for example, an oxidation treatment of firing at a temperature of 300 °C or higher and 800 °C or lower for 1 hour or more and 10 hours or less in an atmosphere containing oxygen can be cited.

[0043] Next, a method for manufacturing the positive electrode active material using the nickel composite hydroxide particles of the present invention as a precursor will be described. For example, in the method for manufacturing the positive electrode active material of the present invention, first, a lithium compound is added to the nickel composite hydroxide particles or nickel composite oxide particles to prepare a mixture of the nickel composite hydroxide particles or nickel composite oxide particles and the lithium compound. As the lithium compound, as long as it is a compound containing lithium, there is no particular limitation, and for example, lithium carbonate, lithium hydroxide, etc. can be cited.

[0044] Next, the positive electrode active material of the present invention can be manufactured by firing the mixture obtained in the above manner. As the firing conditions, for example, the firing temperature is 700 °C or higher and 1000 °C or lower, the heating rate is 50 °C / h or higher and 300 °C / h or lower, and the firing time is 5 hours or more and 20 hours or less. Regarding the firing atmosphere, there is no particular limitation, and for example, air, oxygen, etc. can be cited. In addition, as the firing furnace for firing, there is no particular limitation, and for example, a stationary box furnace, a roller hearth continuous furnace, etc. can be cited.

[0045] In addition, the fired product obtained in the above-described manner can be washed. For washing, pure water or an alkaline cleaning solution can be used. As the alkaline cleaning solution, for example, an aqueous solution of one or more acid anhydrides and their hydrates selected from the group consisting of LiOH (lithium hydroxide), NaOH (sodium hydroxide), KOH (potassium hydroxide), Li2CO3 (lithium carbonate), Na2CO3 (sodium carbonate), K2CO3 (potassium carbonate), and (NH4)2CO3 (ammonium carbonate) can be cited. In addition, ammonia can also be used as the alkaline cleaning solution.

[0046] In the washing step, as a method of bringing the cleaning solution into contact with the fired product, for example, a method of putting the fired product into the aqueous solution of each cleaning solution and stirring, a method of spraying the aqueous solution of each cleaning solution as shower water onto the fired product, and a method of putting the fired product into the aqueous solution of the cleaning solution and stirring, then separating the fired product from the aqueous solution of each cleaning solution, and subsequently spraying the aqueous solution of each cleaning solution as shower water onto the separated fired product can be cited.

[0047] When performing the above washing, after washing, the washed product is separated from the cleaning solution by filtration or the like and heat treatment is performed. As the conditions for heat treatment, for example, the heat treatment temperature is 100°C or higher and 600°C or lower, and the heat treatment time is 1 hour or longer and 20 hours or shorter. The atmosphere for heat treatment is not particularly limited, and for example, air, oxygen, a vacuum atmosphere, etc. can be cited.

[0048] Next, the positive electrode using the positive electrode active material with the nickel composite hydroxide particles of the present invention as a precursor will be described. The positive electrode includes: a positive electrode current collector; and a positive electrode active material layer formed on the surface of the positive electrode current collector and using the positive electrode active material of the present invention. The positive electrode active material layer contains the positive electrode active material of the present invention, a binder, and, if necessary, a conductive additive. As the conductive additive, as long as it can be used in a non-aqueous electrolyte secondary battery, there is no particular limitation. For example, a carbon material can be used. As the carbon material, graphite powder, carbon black (e.g., acetylene black), fibrous carbon materials, etc. can be cited. As the binder, there is no particular limitation, and polymer resins such as polyvinylidene fluoride (PVdF), butadiene rubber (BR), polyvinyl alcohol (PVA), carboxymethyl cellulose (CMC), polytetrafluoroethylene (PTFE), etc. and combinations thereof can be cited. As the positive electrode current collector, there is no particular limitation, and a strip-shaped member formed of a metal material such as Al, Ni, stainless steel, etc. can be cited. Among them, from the viewpoints of easy processing and low cost, a material formed of Al and processed into a thin film shape can be cited.

[0049] As a method for manufacturing a positive electrode, for example, first, a positive electrode active material slurry is prepared by mixing the positive electrode active material of the present invention, a binder, and, if necessary, a conductive assistant. Next, the above positive electrode active material slurry is applied to a positive electrode current collector by a known filling method, dried, and pressed and fixed to obtain a positive electrode.

[0050] A non-aqueous electrolyte secondary battery can be assembled by mounting the positive electrode obtained in the above manner, a negative electrode having a negative electrode current collector and a negative electrode active material layer formed on the surface of the negative electrode current collector and containing a negative electrode active material, an electrolytic solution containing a predetermined electrolyte, and a separator by a known method.

[0051] Examples of the electrolyte contained in the electrolytic solution include lithium salts such as LiClO4, LiPF6, LiAsF6, LiSbF6, LiBF4, LiCF3SO3, LiN(SO2CF3)2, LiN(SO2C2F5)2, LiN(SO2CF3)(COCF3), Li(C4F9SO3), LiC(SO2CF3)3, Li2B 10 Cl 10 , LiBOB (lithium bis(oxalato)borate) (here, BOB is bis(oxalato)borate), LiFSI (lithium bis(fluorosulfonyl)imide) (here, FSI is bis(fluorosulfonyl)imide), lithium salts of lower aliphatic carboxylic acids, LiAlCl4, etc. Regarding the above substances, they can be used alone or two or more of them can be used simultaneously.

[0052] In addition, examples of the solvent of the electrolyte contained in the electrolytic solution include carbonates such as propylene carbonate, ethylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, 4-trifluoromethyl-1,3-dioxolan-2-one, 1,2-bis(methoxycarbonyloxy)ethane; ethers such as 1,2-dimethoxyethane, 1,3-dimethoxypropane, pentafluoropropyl methyl ether, 2,2,3,3-tetrafluoropropyl difluoromethyl ether, tetrahydrofuran, 2-methyltetrahydrofuran; esters such as methyl formate, methyl acetate, γ-butyrolactone; nitriles such as acetonitrile, butyronitrile; amides such as N,N-dimethylformamide, N,N-dimethylacetamide; urethanes such as 3-methyl-2-oxazolidinone; sulfur-containing compounds such as sulfolane, dimethyl sulfoxide, 1,3-propane sultone, or substances in which a fluorine group is further introduced into these organic solvents (substances in which one or more of the hydrogen atoms of the dispersion medium are replaced by fluorine atoms), etc. Regarding the above substances, they can be used alone or two or more of them can be used simultaneously.

[0053] Alternatively, a solid electrolyte can be used to replace the electrolyte solution containing the above electrolyte. Examples of the solid electrolyte include organic polymer electrolytes such as poly(ethylene oxide)-based polymer compounds and polymer compounds containing at least one of a polyorganosiloxane chain or a polyalkylene oxide chain. In addition, a gel-type substance in which a polymer compound holds a non-aqueous electrolyte can be used. Further, examples of the solid electrolyte include inorganic solid electrolytes containing sulfides such as Li2S-SiS2, Li2S-GeS2, Li2S-P2S5, Li2S-B2S3, Li2S-SiS2-Li3PO4, Li2S-SiS2-Li2SO4, and Li2S-GeS2-P2S5. Regarding the above substances, they can be used alone or two or more of them can be used simultaneously.

[0054] Examples of the separator include materials made of polyolefin resins such as polyethylene and polypropylene, fluororesins, nitrogen-containing aromatic polymers, etc., in the form of porous membranes, non-woven fabrics, woven fabrics, etc.

[0055] Examples

[0056] Next, examples of the nickel composite hydroxide particles of the present invention will be described. The present invention is not limited to these examples as long as it does not exceed its gist.

[0057] Manufacture of nickel composite hydroxide particles in examples and comparative examples

[0058] Manufacture of nickel composite hydroxide particles of Example 1

[0059] An aqueous solution of nickel sulfate, cobalt sulfate, and aluminum sulfate dissolved in a specified ratio, an aqueous solution of ammonium sulfate (ammonium ion donor), and an aqueous solution of sodium hydroxide were dropped into a reaction tank. Based on a liquid temperature of 40°C, the pH of the mixed solution in the reaction tank with a volume of 15 L was maintained at 12.1, and the ammonia concentration was maintained at 9.5 g / L. At the same time, the mixture was continuously stirred with a stirrer at a stirring speed of 1200 rpm. The stirrer used a structure with a stirring blade having three propeller-type blades at the front end of the stirring shaft. In addition, the temperature of the mixed solution in the reaction tank was maintained at 40.0°C. The crude nickel composite hydroxide particles formed by the neutralization reaction stayed in the reaction tank for 10 hours and then overflowed from the overflow pipe of the reaction tank and were taken out as a suspension. After filtering the suspension of the above-mentioned crude nickel composite hydroxide particles taken out, it was washed with an aqueous alkali solution and solid-liquid separation was carried out. Then, the separated solid phase was washed with water, and further subjected to dehydration and drying treatments to obtain refined nickel composite hydroxide particles.

[0060] Manufacture of nickel composite hydroxide particles of Example 2

[0061] Except that the pH of the mixed solution in the reaction tank was maintained at 11.9 based on a liquid temperature of 40 °C and the ammonia concentration was maintained at 7.5 g / L, refined nickel composite hydroxide particles were obtained in the same manner as in Example 1.

[0062] Manufacture of nickel composite hydroxide particles of Example 3

[0063] Except that the ratios of nickel sulfate, cobalt sulfate, and aluminum sulfate were changed, the pH of the mixed solution in the reaction tank was maintained at 12.0 based on a liquid temperature of 40 °C, and the ammonia concentration was maintained at 9.0 g / L, refined nickel composite hydroxide particles were obtained in the same manner as in Example 1.

[0064] Manufacture of nickel composite hydroxide particles of Example 4

[0065] Except that the ratios of nickel sulfate, cobalt sulfate, and aluminum sulfate were changed to the same ratios as in Example 3, the liquid temperature of the mixed solution in the reaction tank was set to 45.0 °C, and the residence time in the reaction tank was set to 6 hours, refined nickel composite hydroxide particles were obtained in the same manner as in Example 1.

[0066] Manufacture of nickel composite hydroxide particles of the Comparative Example

[0067] Except that the pH of the mixed solution in the reaction tank was maintained at 12.7 based on a liquid temperature of 40 °C, the ammonia concentration was maintained at 12.0 g / L, the stirring speed was set to 1500 rpm, and the residence time in the reaction tank was 14 hours, refined nickel composite hydroxide particles were obtained in the same manner as in Example 1.

[0068] The neutralization reaction conditions of the nickel composite hydroxide particles of Examples 1 to 4 and the Comparative Example are shown in Table 1 below.

[0069] The evaluation items of the physical properties of the nickel composite hydroxide particles of Examples 1 to 4 and the Comparative Example are as follows.

[0070] (1) Composition analysis of nickel composite hydroxide particles

[0071] After dissolving the obtained nickel composite hydroxide particles in hydrochloric acid, composition analysis was performed using an inductively coupled plasma optical emission spectrometer (manufactured by PerkinElmer Japan Co., Ltd., Optima 7300DV).

[0072] (2) D10, D50, D90

[0073] Measurement was performed using a particle size distribution measuring device (manufactured by Horiba, Ltd., LA-950) (the principle is laser diffraction scattering method).

[0074] (3) BET specific surface area

[0075] After drying 1 g of nickel composite hydroxide particles at a temperature of 105°C for 30 minutes in a nitrogen atmosphere, the measurement was carried out by the one-point BET method using a specific surface area measuring device (manufactured by MOUNTECH Co., Ltd., Macsorb).

[0076] The evaluation results of the physical properties of the nickel composite hydroxide particles of Examples 1 to 4 and the comparative example are shown in Table 1 below.

[0077] [Table 1]

[0078] Unit Example 1 Example 2 Example 3 Example 4 Comparative Example Neutralization temperature ℃ 40.0 40.0 40.0 45.0 40.0 Neutralization pH - 12.1 11.9 12.0 12.1 12.7 Ammonia concentration g / L 9.5 7.5 9.0 9.5 12.0 Stirring speed rpm 1200 1200 1200 1200 1500 Retention time hr 10 10 10 6 14 D10 μm 6.7 6.3 6.8 7.1 6.8 D50 μm 11.9 13.1 12.0 12.6 12.4 D90 μm 18.4 19.8 18.5 19.6 19.7 BET specific surface area <![CDATA[m 2 / g]]> 44 48 50 58 28 Ni mol% 88.0 88.0 91.0 91.0 88.0 Co mol% 9.0 9.0 4.0 4.0 9.0 Al mol% 3.0 3.0 5.0 5.0 3.0

[0079] Porosity (%)

[0080] Using the powder compressor, which is an accessory of the high-precision surface tensiometer DY-700 (manufactured by Kyowa Interface Science Co., Ltd.), 6.5 g of nickel composite hydroxide particles were placed in a container (cell) with a diameter of 10 mm and a height of 100 mm (volume of 7.85 ml), and compressed at a pressure of 21.2 MPa. Thus, the compressed volume (V) of the nickel composite hydroxide particles when the mass was 6.5 g was measured. The porosity was calculated by [V - mass of the composite hydroxide particles × (1 / d)] / V × 100 based on the true density (d) of the nickel composite hydroxide particles. It should be noted that the true density (d) was measured using a gas displacement type dry automatic densitometer, namely "AccuPyc II 1340" (manufactured by Shimadzu Corporation). Regarding the measurement conditions of the true density, the filling pressure was set to 19.500 psig, the equilibrium rate was set to 0.005 psig / min, the sample weight was set to 3.0000 g, and helium gas was used.

[0081] Average circularity of nickel composite hydroxide particles

[0082] Using the wet fluid type particle size / shape analyzer "FPIA-3000S" (manufactured by Sysmex Corporation) and using the objective standard (10 times), the nickel composite hydroxide particles were measured under the HRP measurement mode conditions, and then the circularity was analyzed based on the number and the average value was calculated as the average circularity.

[0083] The average circularity, true density, and porosity of the nickel composite hydroxide particles of Examples 1 to 4 and the comparative example are shown in Table 2 below.

[0084] [Table 2]

[0085] Unit Example 1 Example 2 Example 3 Example 4 Comparative Example Average circularity - 0.90 0.87 0.90 0.88 0.95 True density g / cc 3.59 3.61 3.57 3.62 3.61 Inter-particle porosity ％ 46.1 50.9 49.5 51.3 40.8

[0086] Manufacture of Cathode Active Material Using Nickel Composite Hydroxide Particles of Examples and Comparative Examples as Precursors

[0087] Among the nickel composite hydroxide particles of Examples 1 to 4 and the comparative example, the cathode active material was manufactured using the nickel composite hydroxide particles of Example 1 and the comparative example. When manufacturing the cathode active material, a step of subjecting the nickel composite hydroxide particles to an oxidation treatment to prepare nickel composite oxide particles was carried out in advance. Regarding the oxidation treatment, firing was carried out at a temperature of 690 °C for 5 hours in an air atmosphere, whereby the nickel composite oxide particles of Example 1 and the comparative example were prepared. Then, lithium hydroxide powder was added to the nickel composite oxide particles of Example 1 and the comparative example such that the molar ratio of Li / (Ni + Co + Al) became 1.07, and they were mixed, whereby a mixed powder of nickel composite oxide particles and lithium hydroxide was obtained. The obtained mixed powder was subjected to a firing treatment to obtain lithium metal composite oxide particles. Regarding the firing conditions, in an oxygen-containing atmosphere, the firing temperature was set to 700 °C, the heating rate was set to 200 °C / h, and the firing time was set to 6 hours. In addition, a box furnace was used for firing.

[0088] The lithium metal composite oxide particles obtained in the above manner were washed with water. The slurry-like liquid obtained by adding the lithium metal composite oxide to pure water was stirred for 10 minutes and dehydrated for washing.

[0089] Then, the wet cake obtained by the above washing was heat-treated at a temperature of 150 °C for 12 hours in a vacuum atmosphere to obtain the cathode active material.

[0090] A cathode plate was manufactured using the cathode active material obtained in the above manner, and an evaluation battery was assembled using the manufactured cathode plate. Specifically, the obtained cathode active material, a conductive agent (acetylene black), and a binder (polyvinylidene fluoride) were mixed at a weight ratio of 92:5:3, and N-methyl-2-pyrrolidone was added for kneading and dispersion to manufacture a slurry of the cathode active material. The obtained slurry was applied to an aluminum foil using a Baker applicator, dried at 60 °C for 3 hours and at 150 °C for 12 hours. The product obtained by rolling the dried electrode was punched into an area of 1.65 cm 2 and set as the cathode plate.

[0091] The positive electrode plate obtained in the above manner is placed on the lower cover of the component for button battery R2032 (produced by Hohsen Co., Ltd.) with the aluminum foil facing downward, and a laminated film separator (a heat-resistant porous layer (thickness 16 μm) laminated on a polyethylene porous film) is placed on top of it. 300 μl of electrolyte is injected here. As for the electrolyte, an electrolyte in which 1 mol / l of LiPF6 is dissolved in a 30:35:35 (volume ratio) mixture of ethylene carbonate, dimethyl carbonate and ethyl methyl carbonate is used. Lithium metal is used as the negative electrode, and the negative electrode is placed on the upper side of the laminated film separator, covered with a gasket, and crimped using a crimping machine (Japanese: かしめ机) to produce a lithium secondary battery (button battery R2032).

[0092] Evaluation items for lithium secondary batteries

[0093] (1) Discharge capacity

[0094] The charge and discharge were performed under the following conditions, and the discharge capacity of the first charge and discharge was defined as the discharge capacity. The discharge capacity was evaluated with the ratio of Example being 100.

[0095] Test temperature: 25℃

[0096] The maximum charging voltage is 4.3V, the charging current is 0.2C, and the constant current and constant voltage charging

[0097] The minimum discharge voltage is 2.5V, the discharge current is 0.2C, and the constant current discharge

[0098] (2) Charge and discharge efficiency

[0099] The charge and discharge efficiency was evaluated by setting the ratio of the initial discharge capacity to the initial charge capacity in the above charge and discharge test to 100 for the example.

[0100] Table 3 below shows the evaluation results of the lithium secondary batteries.

[0101] [Table 3]

[0102] Example 1 Comparative Example Discharge capacity (mAh / g) 100 96.9 Charge-discharge efficiency (%) 100 94.5

[0103] As can be seen from Tables 2 and 3, in Example 1 where the precursor (nickel composite hydroxide particles) with a porosity of 46.1% was used to prepare the positive electrode active material, excellent discharge capacity and charge-discharge efficiency could be obtained. In addition, as can be seen from Table 2, in Example 1, the average circularity of the precursor was 0.90. In addition, it was found that even in Example 2 where the porosity was 50.9%, that is, the porosity was 45.0% or more and 55.0% or less as in Example 1, excellent discharge capacity and charge-discharge efficiency could be obtained as in Example 1. In addition, as can be seen from Table 2, in Example 2, the average circularity was 0.87, that is, the average circularity was 0.85 or more and 0.94 or less as in Example 1. In addition, even in Example 3 where the porosity was 49.5%, that is, the porosity was 45.0% or more and 55.0% or less as in Example 1, excellent discharge capacity and charge-discharge efficiency could be obtained as in Example 1. In addition, as can be seen from Table 2, in Example 3, the average circularity was 0.90, that is, the average circularity was 0.85 or more and 0.94 or less as in Example 1. In addition, it was found that even in Example 4 where the porosity was 51.3%, that is, the porosity was 45.0% or more and 55.0% or less as in Example 1, excellent discharge capacity and charge-discharge efficiency could be obtained as in Example 1. In addition, as can be seen from Table 2, in Example 4, the average circularity was 0.88, that is, the average circularity was 0.85 or more and 0.94 or less as in Example 1. On the other hand, in the comparative example where the precursor with a porosity of 40.8% was used to prepare the positive electrode active material, both the discharge capacity and the charge-discharge efficiency decreased compared with Example 1. In addition, as can be seen from Table 2, in the comparative example, the average circularity of the precursor was 0.95.

[0104] Industrial Applicability

[0105] The nickel composite hydroxide particles of the present invention can be used as a positive electrode active material precursor for obtaining a positive electrode active material, and the positive electrode active material can exhibit high discharge capacity and high charge-discharge efficiency by being mounted on a secondary battery using a non-aqueous electrolyte. Therefore, it can be used in a wide range of fields such as portable devices and vehicles.

Claims

1. A nickel composite hydroxide particle, which is a precursor of a positive electrode active material for a non-aqueous electrolyte secondary battery, wherein the porosity of the nickel composite hydroxide particle is 45.0% or more and 55.0% or less. The porosity is a value calculated by [V - mass of the nickel composite hydroxide particle × (1 / d)] / V × 100 (%) using the compressed volume V of the nickel composite hydroxide particle and the true density d of the nickel composite hydroxide particle. The nickel composite hydroxide particles contain Ni, Co, and at least one additional metal element M selected from the group consisting of Mn, Al, Ca, Ti, V, Cr, Zr, Nb, Mo, and W, and the molar ratio of Ni:Co:M is 1 - x - y:x:y, where, 0 < x ≤ 0.2, 0 < y ≤ 0.

1.

2. The nickel composite hydroxide particle according to claim 1, wherein the average circularity of the nickel composite hydroxide particle is 0.85 or more and 0.94 or less.

3. The nickel composite hydroxide particle according to claim 1 or 2, wherein the particle size D50 at a cumulative volume percentage of 50% by volume of the nickel composite hydroxide particle is 5.0 μm or more and 25.0 μm or less.

4. A positive electrode active material for a non-aqueous electrolyte secondary battery, which is obtained by firing the nickel composite hydroxide particle according to any one of claims 1 to 3 and a lithium compound.

5. A method for manufacturing a positive electrode active material for a non-aqueous electrolyte secondary battery, comprising: a step of adding a lithium compound to the nickel composite hydroxide particle according to any one of claims 1 to 3 to obtain a mixture, or a step of subjecting the nickel composite hydroxide particle according to any one of claims 1 to 3 to an oxidation treatment to prepare a nickel composite oxide particle, and then adding a lithium compound to obtain a mixture of the lithium compound and the nickel composite oxide particle; and a step of firing the mixture.