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

Abstract

The present invention provides: a positive electrode active material precursor from which a positive electrode active material, which is provided in a secondary battery using a non-aqueous electrolyte to exhibit a high discharge capacity and a high charge / discharge efficiency, can be obtained; a positive electrode active material obtained from the precursor; and a method for producing the positive electrode active material.　Nickel composite hydroxide particles, which are positive electrode active material precursors for a non-aqueous electrolyte secondary battery, have a porosity of 45.0-55.0%.

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 producing the positive electrode active material. In particular, 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 producing the positive electrode active material, which can obtain a non-aqueous electrolyte secondary battery excellent in discharge capacity and charge-discharge efficiency.

Background Art

[0002] In recent years, from the viewpoint of reducing environmental load, secondary batteries are used in a wide range of fields such as portable devices and vehicles that use or use electricity in combination as a power source. Examples of secondary batteries include secondary batteries 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, an improvement in the packing density of the positive electrode active material mounted on the positive electrode, and thus an improvement in the tap density of the composite hydroxide particles that are the precursor of the positive electrode active material have been proposed. To improve the tap density of the composite hydroxide particles, it is effective to improve 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] In the composite compound of Patent Document 1, although a positive electrode active material excellent in cycle characteristics and rate characteristics can be obtained by improving the tap density and roundness, there is room for improvement in terms of discharge capacity and charge-discharge efficiency, which are other characteristics required for the positive electrode active material.

Prior Art Documents

Patent Documents

[0005] [Patent Document 1] International Publication No. 2014 / 175191 [Summary of the Invention] [Problems to be Solved by the Invention]

[0006] In view of the above circumstances, an object of the present invention is to provide a precursor of a positive electrode active material that can exhibit a high discharge capacity and high charge-discharge efficiency when mounted on a secondary battery using a non-aqueous electrolyte, a positive electrode active material obtained from the precursor, and a method for producing the positive electrode active material. [Means for Solving the Problems]

[0007] The gist of the configuration of the present invention is as follows. [1] Nickel composite hydroxide particles that are a precursor of a positive electrode active material for a non-aqueous electrolyte secondary battery, Nickel composite hydroxide particles having a porosity of 45.0% or more and 55.0% or less. [2] Nickel composite hydroxide particles that are a precursor of a positive electrode active material for a non-aqueous electrolyte secondary battery, Nickel composite hydroxide particles having an average circularity of 0.85 or more and 0.94 or less. [3] The nickel composite hydroxide particles according to [1], having an average circularity of 0.85 or more and 0.94 or less. [4] The nickel composite hydroxide particles according to any one of [1] to [3], wherein the particle diameter (D50) at which the cumulative volume percentage of the nickel composite hydroxide particles is 50% by volume is 5.0 μm or more and 25.0 μm or less. [5] The nickel composite hydroxide particles contain 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 (where 0 < x ≤ 0.2 and 0 < y ≤ 0.1). The nickel composite hydroxide particles according to any one of [1] to [4]. The positive electrode active material of a non-aqueous electrolyte secondary battery, obtained by firing the nickel composite hydroxide particles according to any one of [6][1] to [5] with a lithium compound. A method for producing a positive electrode active material of a non-aqueous electrolyte secondary battery, comprising: a step of adding a lithium compound to the nickel composite hydroxide particles according to any one of [7][1] to [5] to obtain a mixture, or a step of subjecting the nickel composite hydroxide particles according to any one of [1] to [5] to an oxidation treatment to prepare nickel composite oxide particles, 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.

[0008] In the aspect of [1], the "porosity" (unit: %) means a value calculated by measuring the compressed volume (V) of nickel composite hydroxide particles by accommodating a predetermined amount of nickel composite hydroxide particles in a cell of a certain volume and compressing them at a pressure of 21.2 MPa, and using the true density (d) of the nickel composite hydroxide particles, [V - mass of composite hydroxide particles × (1 / d)] / V × 100 (%). As an example, a powder compressor, which is an accessory of a high-precision surface tension meter DY-700 (manufactured by Kyowa Interface Science Co., Ltd.), can be used to measure the compressed volume (V) by accommodating 6.5 g of nickel composite hydroxide particles in a cell with a diameter of 10 mm and a height of 100 mm (volume 7.85 ml) and compressing them at a pressure of 21.2 MPa. Also, the true density (d) is a value measured by a gas displacement type dry automatic density meter.

[0009] In the aspect of [2], the circularity is an index of sphericity when the nickel composite hydroxide particles are projected two-dimensionally. The "circularity" in this specification means a value calculated from the perimeter of a circle having the same area as the particle image / the perimeter of the particle image by photographing each nickel composite hydroxide particle to be measured one by one with a CCD camera or the like. As an example of the apparatus used for the above measurement, a wet flow type particle size and shape analyzer "FPIA-3000S" (manufactured by Sysmex Corporation) can be mentioned. Also, the "average circularity" in this specification means a value obtained by performing an analysis of circularity based on the number and calculating the average value.

Advantages of the Invention

[0010] According to an aspect of the present invention, by having a porosity of 45.0% or more and 55.0% or less, when a positive electrode active material using this nickel composite hydroxide as a precursor is mounted in a secondary battery, high discharge capacity and high charge-discharge efficiency can be exhibited.

[0011] According to an aspect of the present invention, by having an average circularity of the nickel composite hydroxide particles of 0.85 or more and 0.94 or less, when a positive electrode active material using this nickel composite hydroxide particle as a precursor is mounted in a secondary battery, high discharge capacity and high charge-discharge efficiency can be exhibited.

[0012] According to an aspect of the present invention, by having a porosity of 45.0% or more and 55.0% or less and an average circularity of the nickel composite hydroxide particles of 0.85 or more and 0.94 or less, when a positive electrode active material using this nickel composite hydroxide particle as a precursor is mounted in a secondary battery, the discharge capacity and the charge-discharge efficiency can be further improved.

Embodiments for Carrying Out the Invention

[0013] 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 nickel composite hydroxide particles (hereinafter, may be simply referred to as "the nickel composite hydroxide particles of the present invention"), which are the precursor of the positive electrode active material of the non-aqueous electrolyte secondary battery of the present invention, have a porosity of 45.0% or more and 55.0% or less. The shape of the nickel composite hydroxide particles is adjusted so that a predetermined amount of voids are formed between the nickel composite hydroxide particles when the nickel composite hydroxide particles of the present invention are filled.

[0014] The nickel composite hydroxide particles of the present invention can impart a high discharge capacity and high charge-discharge efficiency to a non-aqueous electrolyte secondary battery by having the porosity of 45.0% or more and 55.0% or less. The type of equipment for compressing the powder used for calculating the above porosity is not particularly limited as long as it can compress the nickel composite hydroxide particles of the present invention accommodated in a cell with a constant volume at a pressure of 21.2 MPa. For example, a powder compressor (manufactured by Kyowa Interface Science Co., Ltd.) which is an accessory of a high-precision surface tension meter DY-700 can be mentioned.

[0015] In the present invention, the porosity is not particularly limited as long as it is in the range of 45.0% or more and 55.0% or less. However, the lower limit value is preferably 46.0% or more from the viewpoint of further improving the discharge capacity and charge-discharge efficiency. On the other hand, the upper limit value of the porosity is preferably 53.0% or less, particularly preferably 52.0% or less, from the viewpoint of further improving the discharge capacity and charge-discharge efficiency without impairing other various properties of the positive electrode active material such as cycle characteristics by maintaining the loading density of the positive electrode active material on the positive electrode. Note that the above upper limit value and lower limit value can be arbitrarily combined.

[0016] As described above, the shape of the nickel composite hydroxide particles of the present invention is adjusted so as to have the above porosity. The shape of the nickel composite hydroxide particles of the present invention has, for example, an average circularity of 0.85 or more and 0.94 or less. Therefore, the nickel composite hydroxide particles of the present invention have a shape with a lower circularity compared to conventional precursors.

[0017] The nickel composite hydroxide particles of the present invention can impart a high discharge capacity and high charge-discharge efficiency to a non-aqueous electrolyte secondary battery by having an average circularity of 0.85 or more and 0.94 or less.

[0018] 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. However, the lower limit value, by maintaining the loading density of the positive electrode active material on the positive electrode, further improves the discharge capacity and charge-discharge efficiency without impairing other various properties of the positive electrode active material such as cycle characteristics. From this point of view, 0.87 or more is preferable, and 0.89 or more is particularly preferable. On the other hand, the upper limit value of the average circularity is preferably 0.92 or less, and particularly preferably 0.91 or less, from the point of further improving the discharge capacity and charge-discharge efficiency. It should be noted that the above-mentioned upper limit value and lower limit value can be arbitrarily combined.

[0019] Examples of the components of the nickel composite hydroxide particles of the present invention include 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). That is, the nickel composite hydroxide particles contain Ni and Co as essential metal components, and further contain one or more metal elements among Mn, Al, Ca, Ti, V, Cr, Zr, Nb, Mo, and W as the additive metal element (M).

[0020] The molar ratio of Ni:Co:M is not particularly limited and can be appropriately selected according to the usage conditions of the positive electrode active material obtained from the nickel composite hydroxide particles. The molar ratio of Ni:Co:M is, for example, 1-x-y:x:y (where 0 < x ≤ 0.2 and 0 < y ≤ 0.1). As the additive metal element, it is preferably to contain Al and Mn, and particularly preferably Al, from the point of further improving the discharge capacity and charge-discharge efficiency.

[0021] 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, the lower limit 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, particularly preferably 8.0 μm or more, from the viewpoint of improving density. On the other hand, the upper limit of D50 of the nickel composite hydroxide particles of the present invention is preferably 25.0 μm or less, particularly preferably 20.0 μm or less, from the viewpoint of improving the contact property with the non-aqueous electrolyte. The above-mentioned upper limit and lower limit can be arbitrarily combined.

[0022] Further, the lower limit of the particle size at a cumulative volume percentage of 90% by volume (hereinafter sometimes simply referred to as "D90") of the nickel composite hydroxide particles of the present invention is preferably 10.0 μm or more, particularly preferably 15.0 μm or more, from the viewpoint of improving density. On the other hand, 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, from the viewpoint of improving the contact property with the non-aqueous electrolyte. The above-mentioned upper limit and lower limit can be arbitrarily combined. Also, the lower limit of the particle size at a cumulative volume percentage of 10% by volume (hereinafter sometimes simply referred to as "D10") of the nickel composite hydroxide particles of the present invention is preferably 1.0 μm or more, particularly preferably 5.0 μm or more, from the viewpoint of improving density. On the other hand, 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, from the viewpoint of improving the contact property with the non-aqueous electrolyte. The above-mentioned upper limit and lower limit can be arbitrarily combined. Note that D10, D50, and D90 mean the particle sizes measured by a particle size distribution measuring device using the laser diffraction / scattering method.

[0023] Further, 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 usage conditions of the positive electrode active material and the like. For example, from the viewpoint of improving the loading density of the positive electrode active material, the lower limit value of (D90 - D10) / D50 is preferably 0.40 or more, more preferably 0.50 or more, and particularly preferably 0.70 or more. On the other hand, the upper limit value 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, from the viewpoint of uniformizing various properties of the positive electrode active material regardless of the particle size of the nickel composite hydroxide particles. Note that the above upper limit value and lower limit value can be arbitrarily combined.

[0024] The BET specific surface area of the nickel composite hydroxide particles of the present invention is not particularly limited. For example, its lower limit value is 30 m 2 / g or more, preferably 35 m 2 / g or more, particularly preferably, from the viewpoint of improving the filling degree of the positive electrode active material in the positive electrode and the contact area with the non-aqueous electrolyte. On the other hand, the upper limit value of the BET specific surface area of the nickel composite hydroxide particles of the present invention is preferably 60 m 2 / g or less, preferably 50 m 2 / g or less, particularly preferably, from the viewpoint of improving the crushing strength of the positive electrode active material. Note that the above upper limit value and lower limit value can be arbitrarily combined.

[0025] 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 a metal salt, for example, a solution containing a nickel salt (for example, sulfate), a cobalt salt (for example, sulfate), and a salt of an added metal element (for example, sulfate), a complexing agent, and a pH adjuster are appropriately added to cause 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.

[0026] As the complexing agent, in an aqueous solution, any substance that can form a complex with ions of metal elements, such as nickel and cobalt, and ions of added metal elements is not particularly limited. For example, an ammonium ion donor can be mentioned. Examples of the ammonium ion donor include aqueous ammonia, ammonium sulfate, ammonium chloride, ammonium carbonate, ammonium fluoride, etc. In addition, during the neutralization reaction, in order to adjust the pH value of the aqueous solution, an alkali metal hydroxide (for example, sodium hydroxide, potassium hydroxide) may be added as a pH adjuster as necessary.

[0027] When the above metal salt solution, pH adjuster, and ammonium ion donor are appropriately and continuously supplied to a reaction tank and the substances in the reaction tank are appropriately stirred, the metal in the metal salt solution (for example, nickel, cobalt, added metal element) undergoes a coprecipitation reaction, and crude nickel composite hydroxide particles are prepared. During the coprecipitation reaction, the temperature of the reaction tank is controlled, for example, within the range of 10°C to 80°C, preferably 20°C to 70°C. When supplying the pH adjuster and ammonium ion donor to the reaction tank to cause a coprecipitation reaction, the ammonia concentration and the pH based on a liquid temperature of 40°C of the mixed liquid in the reaction tank are controlled within a predetermined range, and the stirring rotation speed and residence time of the stirring device installed in the reaction tank are adjusted within a predetermined range, whereby the porosity between the nickel composite hydroxide particles can be adjusted to 45.0% or more and 55.0% or less, and the average circularity of the nickel composite hydroxide particles can be adjusted to 0.85 or more and 0.94 or less. The preferable range of the ammonia concentration and the pH based on a liquid temperature of 40°C may need to be adjusted according to the component composition of the crude nickel composite hydroxide particles. For example, the ammonia concentration is preferably less than 12.0 g / L, and particularly preferably 7.0 g / L or more and 11.0 g / L or less. Also, the pH based on a liquid temperature of 40°C is preferably 11.0 or more and 12.5 or less, and particularly preferably 11.5 or more and 12.3 or less. In addition, the stirring rotation speed of the stirring device needs to be appropriately adjusted because the shearing force applied to the particles changes depending on the volume of the reaction tank, the type of stirring blade, and the residence time. For example, when using three propeller blades in a reaction tank with a volume of 15 L and causing a coprecipitation reaction with a residence time of 5 to 10 hours, the stirring rotation speed is preferably 1000 rpm or more and 1500 rpm or less, and particularly preferably 1100 rpm or more and 1400 rpm or less.

[0028] As a stirring device used in the method for producing nickel composite hydroxide particles of the present invention, for example, a stirring device having a stirring blade equipped with a plurality of propeller blades at the tip of a stirring shaft can be mentioned. Further, as a reaction vessel used in the method for producing nickel composite hydroxide particles of the present invention, for example, a continuous type in which the obtained crude nickel composite hydroxide particles are overflowed for separation or a batch type in which the particles are not discharged to the outside of the system until the reaction is completed can be mentioned.

[0029] As described above, after filtering the crude nickel composite hydroxide particles obtained in the neutralization reaction step from the suspension, they are washed with an alkaline aqueous solution to remove impurities contained in the crude nickel composite hydroxide particles, and purified nickel composite hydroxide particles (nickel composite hydroxide particles of the present invention) are obtained. Then, by performing solid-liquid separation and, if necessary, washing the solid phase containing the nickel composite hydroxide particles with water and heat-treating and drying the nickel composite hydroxide particles, powdery nickel composite hydroxide particles can be obtained.

[0030] 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, may be simply referred to as "the positive electrode active material of the present invention") will be described. In the positive electrode active material of the present invention, the nickel composite hydroxide particles of the present invention, which are the precursor, are, for example, in a state of being fired 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, it is more preferably a hexagonal crystal structure or a monoclinic crystal structure. The positive electrode active material of the present invention can be used, for example, as a positive electrode active material of a lithium ion secondary battery. In addition, when producing the positive electrode active material of the present invention, a step of preparing nickel composite hydroxide particles into nickel composite oxide particles in advance may be carried out. Examples of the method for preparing nickel composite oxide particles from nickel composite hydroxide particles include an oxidation treatment in which firing is performed 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 in which oxygen gas is present.

[0031] Next, a method for manufacturing a 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 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. The lithium compound is not particularly limited as long as it is a compound containing lithium, and examples thereof include lithium carbonate and lithium hydroxide.

[0032] Next, the positive electrode active material of the present invention can be manufactured by firing the mixture obtained as described above. Examples of the firing conditions include a firing temperature of 700°C or higher and 1000°C or lower, a heating rate of 50°C / h or higher and 300°C / h or lower, and a firing time of 5 hours or longer and 20 hours or shorter. The firing atmosphere is not particularly limited, and examples thereof include air and oxygen. Also, the firing furnace used for firing is not particularly limited, and examples thereof include a stationary box furnace and a roller hearth continuous furnace.

[0033] Note that the fired product obtained as described above may be washed. Pure water or an alkaline cleaning solution can be used for washing. Examples of the alkaline cleaning solution include aqueous solutions of one or more anhydrides and hydrates thereof 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). Ammonia can also be used as the alkaline cleaning solution.

[0034] In the washing step, examples of the method of bringing the washing solution into contact with the fired product include a method of charging the fired product into an aqueous solution of each washing solution and stirring, a method of spraying the aqueous solution of each washing solution as shower water onto the fired product, a method of charging the fired product into an aqueous solution of each washing solution, stirring, separating the fired product from the aqueous solution of each washing solution, and then spraying the aqueous solution of each washing solution as shower water onto the separated fired product.

[0035] When performing the above washing, after washing, the washed product is separated from the washing liquid by filtration or the like, and heat treatment is performed. Examples of the conditions for the heat treatment include a heat treatment temperature of 100°C or higher and 600°C or lower, and a heat treatment time of 1 hour or longer and 20 hours or shorter. The atmosphere for the heat treatment is not particularly limited, and examples include air, oxygen, and a vacuum atmosphere.

[0036] Next, a positive electrode using a positive electrode active material having 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 has the positive electrode active material of the present invention, a binder, and, if necessary, a conductive assistant. The conductive assistant is not particularly limited as long as it can be used for a non-aqueous electrolyte secondary battery, and for example, a carbon material can be used. Examples of the carbon material include graphite powder, carbon black (e.g., acetylene black), and fibrous carbon materials. The binder is not particularly limited, and examples include polymer resins such as polyvinylidene fluoride (PVdF), butadiene rubber (BR), polyvinyl alcohol (PVA), carboxymethyl cellulose (CMC), polytetrafluoroethylene (PTFE), and combinations thereof. The positive electrode current collector is not particularly limited, and for example, a strip-shaped member made of a metal material such as Al, Ni, or stainless steel can be used as the forming material. Among them, from the viewpoints of being easy to process and inexpensive, those formed of Al and processed into a thin film shape can be mentioned.

[0037] As a method for manufacturing the positive electrode, for example, first, the positive electrode active material of the present invention, a binder, and, if necessary, a conductive assistant are mixed to prepare a positive electrode active material slurry. Next, the positive electrode active material slurry is applied to the positive electrode current collector by a known filling method, dried, and pressed and fixed to obtain a positive electrode.

[0038] By mounting the positive electrode obtained as described above, a negative electrode including a negative electrode current collector and a negative electrode active material layer formed on the surface of the negative electrode current collector, an electrolytic solution containing a predetermined electrolyte, and a separator by a known method, a non-aqueous electrolyte secondary battery can be assembled.

[0039] 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 (where BOB is bis(oxalato)borate), LiFSI (where FSI is bis(fluorosulfonyl)imide), lithium salts of lower aliphatic carboxylic acids, LiAlCl4, and the like. These may be used alone or in combination of two or more.

[0040] 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, and 1,2-di(methoxycarbonyloxy)ethane; ethers such as 1,2-dimethoxyethane, 1,3-dimethoxypropane, pentafluoropropyl methyl ether, 2,2,3,3-tetrafluoropropyl difluoromethyl ether, tetrahydrofuran, and 2-methyltetrahydrofuran; esters such as methyl formate, methyl acetate, and γ-butyrolactone; nitriles such as acetonitrile and butyronitrile; amides such as N,N-dimethylformamide and N,N-dimethylacetamide; carbamates such as 3-methyl-2-oxazolidone; sulfur-containing compounds such as sulfolane, dimethyl sulfoxide, and 1,3-propane sultone, or those obtained by further introducing a fluoro group into these organic solvents (substituting one or more of the hydrogen atoms of the dispersion medium with fluorine atoms), and the like. These may be used alone or in combination of two or more.

[0041] Alternatively, instead of the electrolytic solution containing the above electrolyte, a solid electrolyte may be used. Examples of the solid electrolyte include organic polymer electrolytes such as polyethylene oxide-based polymer compounds and polymer compounds containing at least one of polyorganosiloxane chains or polyoxyalkylene chains. In addition, a gel-type one in which a non-aqueous electrolyte is held in a polymer compound can also be used. Examples of the solid electrolyte also 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. These may be used alone or in combination of two or more.

[0042] Examples of the separator include materials having forms such as porous membranes, non-woven fabrics, and woven fabrics made of materials such as polyolefin resins such as polyethylene and polypropylene, fluororesins, and nitrogen-containing aromatic polymers.

Examples

[0043] Next, examples of the nickel composite hydroxide particles of the present invention will be described. However, the present invention is not limited to these examples as long as the gist thereof is not exceeded.

[0044] Production of Nickel Composite Hydroxide Particles in Examples and Comparative Examples Production of Nickel Composite Hydroxide Particles in Example 1 An aqueous solution in which nickel sulfate, cobalt sulfate, and aluminum sulfate were dissolved at a predetermined ratio, an aqueous ammonium sulfate solution (ammonium ion donor), and an aqueous sodium hydroxide solution were dropped into a reaction tank, and the pH of the mixed solution in the reaction tank with a volume of 15 L was adjusted to 12.1 based on a liquid temperature of 40 °C, and the ammonia concentration was maintained at 9.5 g / L. While continuously stirring at a stirring rotation speed of 1200 rpm by a stirrer. As the stirrer, one having a stirring blade equipped with three propeller blades at the tip of the stirring shaft was used. Also, the liquid temperature of the mixed solution in the reaction tank was maintained at 40.0 °C. The crude nickel composite hydroxide particles generated by the neutralization reaction were retained in the reaction tank for 10 hours, and then overflowed from the overflow pipe of the reaction tank and taken out as a suspension. The suspension of the taken-out crude nickel composite hydroxide particles was filtered, washed with an alkaline aqueous solution, and subjected to solid-liquid separation. Thereafter, the separated solid phase was washed with water, and further subjected to dehydration and drying treatments to obtain purified nickel composite hydroxide particles.

[0045] Production of Nickel Composite Hydroxide Particles in Example 2 Purified nickel composite hydroxide particles were obtained in the same manner as in Example 1, 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.

[0046] Production of Nickel Composite Hydroxide Particles in Example 3 The ratio of nickel sulfate, cobalt sulfate, and aluminum sulfate was changed, and purified nickel composite hydroxide particles were obtained in the same manner as in Example 1, except that 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.

[0047] Production of nickel composite hydroxide particles of Example 4 Purified nickel composite hydroxide particles were obtained in the same manner as in Example 1, except that the ratio of nickel sulfate, cobalt sulfate, and aluminum sulfate was changed to the same ratio as in Example 3, the liquid temperature of the mixed solution in the reaction tank was 45.0 °C, and the residence time in the reaction tank was 6 hours.

[0048] Production of nickel composite hydroxide particles of the comparative example Purified nickel composite hydroxide particles were obtained in the same manner as in Example 1, 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 rotation speed was 1500 rpm, and the mixture was retained in the reaction tank for 14 hours.

[0049] 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.

[0050] 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. (1) Composition analysis of nickel composite hydroxide particles For the composition analysis, the obtained nickel composite hydroxide particles were dissolved in hydrochloric acid, and then analyzed using an inductively coupled plasma optical emission spectrometer (manufactured by PerkinElmer Japan Co., Ltd., Optima 7300DV).

[0051] (2) D10, D50, D90 The particle size distribution was measured using a particle size distribution measuring device (manufactured by Horiba, Ltd., LA-950) (the principle is the laser diffraction / scattering method).

[0052] (3) BET specific surface area After drying 1 g of nickel composite hydroxide particles at 105 °C for 30 minutes in a nitrogen atmosphere, the specific surface area was measured by the one-point BET method using a specific surface area measuring device (manufactured by Mountech Co., Ltd., Macsorb).

[0053] 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.

[0054]

Table 1

[0055] Porosity (%) Using a 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 were placed in a cell 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 to measure the compressed volume (V) per 6.5 g of nickel composite hydroxide particles. The porosity was calculated as [V - mass of composite hydroxide particles × (1 / d)] / V × 100 from the true density (d) of the nickel composite hydroxide particles. The true density (d) was measured using a gas displacement type dry automatic densitometer "Accupic II 1340" (manufactured by Shimadzu Corporation). The measurement conditions for the true density were a filling pressure of 19.500 psig, an equilibrium rate of 0.005 psig / min, a sample weight of 3.0000 g, and helium gas as the gas.

[0056] Average circularity of nickel composite hydroxide particles Using a wet flow type particle size and shape analyzer "FPIA-3000S" (manufactured by Sysmex Corporation), with the objective lens standard (10x) used, after measuring the nickel composite hydroxide particles under the HRP measurement mode conditions, the circularity was analyzed based on the number standard, and the average value was calculated as the average circularity.

[0057] 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.

[0058]

Table 2

[0059] Manufacture of Cathode Active Material Using Nickel Composite Hydroxide Particles of Examples and Comparative Examples as Precursors Among the nickel composite hydroxide particles of Examples 1 to 4 and the comparative example, cathode active materials were 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 in advance to prepare nickel composite oxide particles was carried out. The oxidation treatment was carried out by firing at a temperature of 690°C for 5 hours in an air atmosphere to prepare the nickel composite oxide particles of Example 1 and the comparative example. Then, lithium hydroxide powder was added to and mixed with the nickel composite oxide particles of Example 1 and the comparative example so that the molar ratio of Li / (Ni + Co + Al) became 1.07 to obtain a mixed powder of nickel composite oxide particles and lithium hydroxide. The obtained mixed powder was subjected to a firing treatment to obtain lithium metal composite oxide particles. The firing conditions were a firing temperature of 700°C, a heating rate of 200°C / h, and a firing time of 6 hours in an oxygen atmosphere. Also, a box furnace was used for firing.

[0060] The lithium metal composite oxide particles obtained as described above were washed with water. The washing was carried out by adding the lithium metal composite oxide to pure water, stirring the resulting slurry-like liquid for 10 minutes, and dehydrating.

[0061] Thereafter, the wet cake obtained by the above washing was heat-treated at 150°C for 12 hours in a vacuum atmosphere to obtain a cathode active material.

[0062] A positive electrode plate was fabricated using the positive electrode active material obtained as described above, and an evaluation battery was assembled using the fabricated positive electrode plate. Specifically, the obtained positive electrode active material, a conductive agent (acetylene black), and a binder (polyvinylidene fluoride) were mixed at a weight ratio of 92:5:3, respectively, and N-methyl-2-pyrrolidone was added and kneaded and dispersed to prepare a slurry of the positive electrode active material. The obtained slurry was applied to an aluminum foil using a Baker applicator and dried at 60 °C for 3 hours and at 150 °C for 12 hours. The dried electrode was roll-pressed and punched out to an area of 1.65 cm 2 to obtain a positive electrode plate.

[0063] The positive electrode plate obtained as described above was placed with the aluminum foil side facing down on the lower lid of the parts for a coin-type battery R2032 (manufactured by Takizawa Co., Ltd.), and a laminated film separator (a heat-resistant porous layer laminated on a porous polyethylene film (thickness 16 μm)) was placed thereon. 300 μl of an electrolytic solution was injected here. As the electrolytic solution, a solution in which LiPF6 was dissolved to 1 mol / l in a 30:35:35 (volume ratio) mixture of ethylene carbonate, dimethyl carbonate, and ethyl methyl carbonate was used. Lithium metal was used as the negative electrode, and the negative electrode was placed on the upper side of the laminated film separator, covered with an upper lid through a gasket, and caulked with a caulking machine to fabricate a lithium secondary battery (coin-type battery R2032).

[0064] Evaluation items of lithium secondary battery (1) Discharge capacity Charge and discharge were performed under the following conditions, and the discharge capacity of the first charge and discharge was taken as the discharge capacity. The discharge capacity was evaluated at a ratio with the example taken as 100. Test temperature: 25 °C Maximum charge voltage 4.3 V, charge current 0.2C, constant current constant voltage charging Minimum discharge voltage 2.5 V, discharge current 0.2C, constant current discharge (2) Charge and discharge efficiency The charge and discharge efficiency was defined as the ratio of the first discharge capacity to the first charge capacity in the above charge and discharge test. The charge and discharge efficiency was evaluated at a ratio with the example taken as 100.

[0065] The evaluation results of the lithium secondary battery are shown in Table 3 below.

[0066]

Table 3

[0067] From Tables 2 and 3, in Example 1 where the cathode active material was produced using a precursor (nickel composite hydroxide particles) with a porosity of 46.1%, excellent discharge capacity and charge-discharge efficiency could be obtained. Also, from Table 2, in Example 1, the average circularity of the precursor was 0.90. Further, in Example 2 where the porosity was 50.9% and the porosity was also 45.0% or more and 55.0% or less as in Example 1, it was found that excellent discharge capacity and charge-discharge efficiency could be obtained in the same manner as in Example 1. Also, from Table 2, in Example 2, the average circularity was 0.87 and the average circularity was also 0.85 or more and 0.94 or less as in Example 1. Also, in Example 3 where the porosity was 49.5% and the porosity was also 45.0% or more and 55.0% or less as in Example 1, it was found that excellent discharge capacity and charge-discharge efficiency could be obtained in the same manner as in Example 1. Also, from Table 2, in Example 3, the average circularity was 0.90 and the average circularity was also 0.85 or more and 0.94 or less as in Example 1. Also, in Example 4 where the porosity was 51.3% and the porosity was also 45.0% or more and 55.0% or less as in Example 1, it was found that excellent discharge capacity and charge-discharge efficiency could be obtained in the same manner as in Example 1. Also, from Table 2, in Example 4, the average circularity was 0.88 and the average circularity was also 0.85 or more and 0.94 or less as in Example 1. On the other hand, in the comparative example where the cathode active material was produced using a precursor with a porosity of 40.8%, both the discharge capacity and the charge-discharge efficiency decreased compared to Example 1. Also, from Table 2, in the comparative example, the average circularity of the precursor was 0.95.

Industrial Applicability

[0068] The nickel composite hydroxide particles of the present invention can be used as a precursor of a positive electrode active material capable of obtaining a positive electrode active material that can exhibit a high discharge capacity and high charge-discharge efficiency when mounted in 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. Nickel composite hydroxide particles which are precursors of the positive electrode active material of a non-aqueous electrolyte secondary battery, having a porosity of 45.0% or more and 55.0% or less, The nickel composite hydroxide particles contain 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 (where 0 < x ≤ 0.2 and 0 < y ≤ 0.1). Nickel composite hydroxide particles.

2. Nickel composite hydroxide particles which are precursors of the positive electrode active material of a non-aqueous electrolyte secondary battery, having an average circularity of 0.85 or more and 0.94 or less, The particle diameter (D50) of the nickel composite hydroxide particles at a cumulative volume percentage of 50% by volume is 5.0 μm or more and 25.0 μm or less, The nickel composite hydroxide particles contain 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 (where 0 < x ≤ 0.2 and 0 < y ≤ 0.1). Nickel composite hydroxide particles.

3. The nickel composite hydroxide particles according to Claim 1, having an average circularity of 0.85 or more and 0.94 or less.

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

5. A method for producing a positive electrode active material of a non-aqueous electrolyte secondary battery, comprising firing the nickel composite hydroxide particles according to any one of Claims 1 to 4 with a lithium compound.

6. A step of adding a lithium compound to the nickel composite hydroxide particles according to any one of claims 1 to 4 to obtain a mixture, or a step of oxidizing the nickel composite hydroxide particles according to any one of claims 1 to 4 to prepare nickel composite oxide particles, 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, a method for producing a positive electrode active material of a non-aqueous electrolyte secondary battery.

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