Metal composite compound and positive electrode active material using the metal composite compound as a precursor

Abstract

The present invention provides a metal composite compound that can provide a positive electrode active material having an excellent discharge capacity, and a positive electrode active material that uses the metal composite compound as a precursor. [Solution] A metal complex compound in which the relative standard deviation of the volume-based crystallite size distribution calculated from the diffraction peaks within the range of 2θ=38±1° in powder X-ray diffraction measurement using CuKα radiation is less than 0.70.

Description

[Technical Field]

[0001] The present invention relates to a metal composite compound and a positive electrode active material having a metal composite compound as a precursor, and in particular to a metal composite compound and a positive electrode active material having a metal composite compound as a precursor that can provide a positive electrode active material having excellent rate characteristics during discharge. [Background technology]

[0002] In recent years, in order to reduce environmental impact, secondary batteries have been used in a wide range of fields, such as portable devices such as mobile phones and portable personal computers, and vehicles that use or combine electricity as a power source. Examples of secondary batteries include secondary batteries using non-aqueous electrolytes, such as lithium-ion secondary batteries. Secondary batteries using non-aqueous electrolytes, such as lithium-ion secondary batteries, are suitable for miniaturization and weight reduction, and have properties such as high utilization rate and high cycle characteristics.

[0003] To improve the battery characteristics of lithium-ion secondary batteries, high battery capacity and high output characteristics are required. Therefore, a nickel-based hydroxide has been proposed for use as a positive electrode active material for lithium composite oxides, which have a peak half width at around 19° in the range of 0.1° to 0.60°, a peak half width at around 38° in the range of 0.1° to 0.50°, and a peak half width at around 52° in the range of 0.1° to 0.65° in an X-ray diffraction profile using CuKα radiation (Patent Document 1).

[0004] Patent Document 1 describes that, based on the finding that the discharge capacity of a lithium composite oxide depends on the half-value width of a peak in a specific X-ray diffraction profile of a raw material hydroxide, a high-capacity lithium composite oxide for a positive electrode active material can be obtained by using, as a raw material, a hydroxide containing nickel as its main component and having a relatively low half-value width.

[0005] On the other hand, for example, in portable devices such as mobile phones and portable personal computers, electric vehicles that use electricity as a power source, or hybrid vehicles that also use electricity as a power source, non-aqueous electrolyte secondary batteries that serve as power sources are required to have large discharge capacities. However, the precursor of the positive electrode active material in Patent Document 1 leaves room for improvement in terms of improving the discharge capacity of non-aqueous electrolyte secondary batteries. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Publication No. 10-310433 Summary of the Invention [Problem to be solved by the invention]

[0007] In view of the above circumstances, an object of the present invention is to provide a metal composite compound from which a positive electrode active material having an excellent discharge capacity can be obtained, and a positive electrode active material using the metal composite compound as a precursor. [Means for solving the problem]

[0008] In the metal composite compound of the present invention, the relative standard deviation of the volume-based crystallite size distribution calculated from the diffraction peaks in the range of 2θ=38±1° in powder X-ray diffraction measurement using CuKα radiation is adjusted to less than 0.70. Therefore, in the metal composite compound of the present invention, the variation in the volume-based crystallite size distribution calculated from the diffraction peaks in the range of 2θ=38±1° is suppressed. In addition, the metal composite compound of the present invention is a precursor of a positive electrode active material.

[0009] The gist of the configuration of the present invention is as follows. [1] A metal complex compound having a relative standard deviation of less than 0.70 in the volume-based crystallite size distribution calculated from the diffraction peaks within the range of 2θ=38±1° in powder X-ray diffraction measurement using CuKα radiation. [2] The metal complex compound according to [1], which has a tap density of 1.9 g / mL or less. [3] The following composition formula (I) Ni 1-x-y Co x M y O z (OH) 2-α Formula (I) The metal complex compound according to [1] or [2], represented by formula (I), wherein 0≦x≦0.3, 0≦y≦0.3, 0≦x+y≦0.3, 0≦z≦3, −0.5≦α≦2, and α−z<2 are satisfied, and M is one or more additive elements selected from the group consisting of Mn, Fe, Cu, Ti, Mg, Al, Zn, Sn, Zr, Nb, Ga, W, Mo, B, and Si. [4] The metal complex compound according to any one of [1] to [3], wherein the particle diameter at a cumulative volume percentage of 50% by volume (D50) is 7.0 μm or more and 20.0 μm or less. [5] The metal complex compound according to any one of [1] to [4], wherein the mode of the crystallite size in the crystallite size distribution is 30 Å or more and 200 Å or less. [6] The metal complex compound according to any one of [1] to [5], wherein the relative standard deviation is 0.30 or more. [7] A positive electrode active material for a non-aqueous electrolyte secondary battery, obtained by baking the metal composite compound according to any one of [1] to [6] with a lithium compound. [Effects of the Invention]

[0010] According to the metal composite compound of the present invention, the relative standard deviation of the volume-based crystallite size distribution calculated from the diffraction peaks in the range of 2θ=38±1° in powder X-ray diffraction measurement using CuKα rays is less than 0.70, and therefore a positive electrode active material having excellent discharge capacity can be obtained.

[0011] According to the metal composite compound of the present invention, since the tap density is 1.9 g / mL or less, a positive electrode active material having an excellent discharge capacity can be more reliably obtained.

[0012] According to the metal composite compound of the present invention, the particle size (D50) at a cumulative volume percentage of 50% by volume is 7.0 μm or more and 20.0 μm or less, which makes it easy to control the relative standard deviation of the volume-based crystallite size distribution calculated from the diffraction peaks within the range of 2θ=38±1° to less than 0.70. DETAILED DESCRIPTION OF THE INVENTION

[0013] The metal complex compound of the present invention will be described in detail below.

[0014] The metal composite compound of the present invention is a secondary particle formed by aggregation of a plurality of primary particles. The particle shape of the metal composite compound of the present invention is not particularly limited and may be a wide variety of shapes, such as a substantially spherical shape or a substantially elliptical shape.

[0015] The metal composite compound of the present invention has a relative standard deviation of the volume-based crystallite size distribution calculated from diffraction peaks within the range of 2θ=38±1° in powder X-ray diffraction measurement using CuKα radiation, which is controlled to less than 0.70.

[0016] The metal composite compound of the present invention has a relative standard deviation of the volume-based crystallite size distribution calculated from the diffraction peaks in the range of 2θ=38±1° in powder X-ray diffraction measurement using CuKα radiation of less than 0.70, and therefore a positive electrode active material using the metal composite compound of the present invention as a precursor has excellent discharge capacity.

[0017] The relative standard deviation of the crystallite size distribution of the metal composite compound of the present invention can be obtained by the following method. First, a powdered metal composite compound is subjected to powder X-ray diffraction measurement using CuKα as a radiation source and within a measurement range of a diffraction angle 2θ of 10° to 90°, to obtain a diffraction peak within the range of 2θ = 38 ± 1°. An example of an X-ray diffractometer used for the powder X-ray diffraction measurement is Ultima IV manufactured by Rigaku Corporation.

[0018] The obtained diffraction peak data is read into analytical software, analyzed using the FP method, and the analytical data is output as a log-normal distribution to obtain the relative standard deviation of the volume-based crystallite size distribution. For example, the integrated powder X-ray analysis software PDXL2 manufactured by Rigaku Corporation can be used as the analytical software.

[0019] A metal composite compound having a relative standard deviation of less than 0.70 has a narrow crystallite size distribution, i.e., the crystallite size variation is reduced. A positive electrode active material obtained by firing a mixture of a metal composite compound having a reduced crystallite size variation and a lithium compound exhibits excellent discharge capacity during discharge due to the uniform reaction of lithium ions throughout the positive electrode active material.

[0020] The relative standard deviation is not particularly limited as long as it is less than 0.70, but the upper limit of the relative standard deviation is preferably 0.69 or less, more preferably 0.67 or less, and particularly preferably 0.65 or less, from the viewpoint of further improving the discharge capacity of the positive electrode active material using the metal composite compound of the present invention as a precursor. On the other hand, the lower limit of the relative standard deviation is, for example, 0.30 or more.

[0021] The upper and lower limits of the relative standard deviation can be arbitrarily combined. The relative standard deviation is preferably 0.30 or more and 0.69 or less, more preferably 0.30 or more and 0.67 or less, and particularly preferably 0.30 or more and 0.65 or less.

[0022] The mode of the crystallite size in the crystallite size distribution can be determined by analyzing the crystallite size distribution determined by the above method using the above analysis software.

[0023] The mode of the crystallite size in the crystallite size distribution is not particularly limited, but its lower limit is preferably 30 Å or more, particularly preferably 40 Å or more, from the viewpoint of facilitating the reaction of lithium ions in the positive electrode active material and contributing to improving the discharge capacity. On the other hand, the upper limit of the mode of the crystallite size in the crystallite size distribution is preferably 200 Å or less, more preferably 150 Å or less, particularly preferably 130 Å or less, from the viewpoint of suppressing deterioration of the positive electrode active material due to expansion and contraction of the crystallites caused by charge and discharge.

[0024] The lower limit and upper limit of the mode can be arbitrarily combined. The mode is preferably 30 Å or more and 200 Å or less, more preferably 40 Å or more and 150 Å or less, and particularly preferably 40 Å or more and 130 Å or less.

[0025] The tap density of the metal composite compound of the present invention is not particularly limited, but from the viewpoint of obtaining a positive electrode active material having excellent discharge capacity, the upper limit is preferably 1.9 g / mL or less, more preferably 1.8 g / mL or less, and particularly preferably 1.7 g / mL or less. On the other hand, from the viewpoint of improving the packing density of the positive electrode active material, the lower limit of the tap density is preferably 1.0 g / mL or more, and particularly preferably 1.2 g / mL or more.

[0026] The upper and lower limits of the tap density can be arbitrarily combined. From the viewpoint of improving the packing density of the positive electrode active material and obtaining an excellent discharge capacity, the tap density is preferably 1.0 g / mL or more and 1.9 g / mL or less, more preferably 1.2 g / mL or more and 1.8 g / mL or less, and particularly preferably 1.2 g / mL or more and 1.7 g / mL or less.

[0027] The particle diameter (D50) at a cumulative volume percentage of 50% by volume of the metal composite compound of the present invention (hereinafter sometimes simply referred to as "D50") is not particularly limited, but the lower limit is preferably 7.0 μm or more, more preferably 8.0 μm or more, and particularly preferably 10.0 μm or more, from the viewpoint of improving the packing density of the positive electrode active material in the positive electrode. On the other hand, the upper limit of D50 of the metal composite compound of the present invention is preferably 20.0 μm or less, more preferably 19.0 μm or less, and particularly preferably 18.0 μm or less, from the viewpoint of improving contact with the electrolyte. The above-mentioned lower limit and upper limit can be combined arbitrarily.

[0028] Among these, from the viewpoint of facilitating the control of the relative standard deviation of the volume-based crystallite size distribution calculated from the diffraction peaks within the range of 2θ=38±1° to less than 0.70, it is preferably 7.0 μm or more and 20.0 μm or less, more preferably 8.0 μm or more and 19.0 μm or less, and particularly preferably 10.0 μm or more and 18.0 μm or less. The above-mentioned D50 means the particle size measured with a particle size distribution analyzer using a laser diffraction / scattering method.

[0029] The composition of the metal composite compound of the present invention may be, for example, the following composition formula (I): Ni 1-x-y Co x M y O z (OH) 2-α Formula (I) (wherein formula (I) satisfies 0≦x≦0.3, 0≦y≦0.3, 0≦x+y≦0.3, 0≦z≦3, −0.5≦α≦2, and α−z<2, and M is one or more additional elements selected from the group consisting of Mn, Fe, Cu, Ti, Mg, Al, Zn, Sn, Zr, Nb, Ga, W, Mo, B, and Si), i.e., nickel-containing hydroxides or nickel-containing oxides.

[0030] Among these, the value of x is preferably 0.05≦x≦0.25, more preferably 0.07≦x≦0.20, and particularly preferably 0.10≦x≦0.15. The value of y is preferably 0.01≦y≦0.15, more preferably 0.02≦y≦0.10, and particularly preferably 0.03≦y≦0.07. The value of x+y is preferably 0.06≦x+y≦0.25, more preferably 0.10≦x+y≦0.22, and particularly preferably 0.12≦x+y≦0.20.

[0031] The metal composite compound of the present invention can be used as a precursor (hydroxide or oxide) of a positive electrode active material for a non-aqueous electrolyte secondary battery.

[0032] Next, a positive electrode active material for a non-aqueous electrolyte secondary battery using the metal composite compound 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. The positive electrode active material of the present invention is in a form in which the metal composite compound of the present invention, which is a precursor, is calcined with, for example, a lithium compound. By calcining the metal composite compound of the present invention with a lithium compound, a non-aqueous electrolyte secondary battery having excellent discharge capacity can be obtained.

[0033] The crystalline 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 preferably a trigonal crystalline structure, a hexagonal crystalline structure, or a monoclinic crystalline structure. The positive electrode active material of the present invention can be used, for example, as a positive electrode active material for non-aqueous electrolyte secondary batteries such as lithium ion secondary batteries.

[0034] Next, a method for producing a metal composite compound of the present invention will be described. The method for producing a metal composite compound of the present invention includes a reaction step of continuously supplying a metal-containing aqueous solution containing nickel, a complexing agent, and an alkaline aqueous solution to a reaction tank and causing a crystallization reaction to obtain a metal composite compound, a slurry concentration step of continuously withdrawing a slurry containing the metal composite compound from the reaction tank and supplying the slurry containing the metal composite compound to a settling tank to concentrate the slurry, and a concentrated slurry reflux step of returning the concentrated slurry to the reaction tank.

[0035] <Reaction process for obtaining metal complex compound> The reaction process for obtaining a metal composite compound is a crystallization process in which a metal-containing aqueous solution containing nickel, a pH adjuster which is an alkaline aqueous solution, and a complexing agent are added and mixed in a reaction tank, and a coprecipitation reaction occurs in the reaction solution to obtain a metal composite compound.

[0036] Specifically, by coprecipitation, a metal-containing aqueous solution containing nickel, which contains a nickel salt (e.g., sulfate) and an optional cobalt salt (e.g., sulfate) and a salt of the additional element M (e.g., sulfate), an alkaline aqueous solution, and a complexing agent are added to a reaction vessel, whereby a neutralization reaction occurs in the reaction vessel to cause crystallization, thereby preparing a metal composite compound and obtaining a slurry-like suspension containing the metal composite compound. Water, for example, is used as the solvent for the suspension.

[0037] The complexing agent is not particularly limited as long as it can form a complex with nickel, the optional cobalt, and the additional element M in an aqueous solution, and examples thereof include ammonium ion donors (ammonium sulfate, ammonium chloride, ammonium carbonate, ammonium fluoride, etc.), hydrazine, ethylenediaminetetraacetic acid, nitrilotriacetic acid, uracildiacetic acid, and glycine.

[0038] The alkaline aqueous solution is not particularly limited as long as it adjusts the pH value of the aqueous solution in the reaction tank during coprecipitation, and examples thereof include aqueous solutions of alkali metal hydroxides (for example, sodium hydroxide, potassium hydroxide).

[0039] When the nickel-containing metal-containing aqueous solution, the alkaline aqueous solution, and the complexing agent are continuously supplied to a reaction vessel, a crystallization reaction occurs between nickel, the optional cobalt, and the additional element M, producing a metal composite compound. During the crystallization reaction, the temperature in the reaction vessel is controlled, for example, within a range of 10°C to 80°C, preferably 20°C to 70°C, and the pH value in the reaction vessel is controlled, for example, within a range of pH 9 to pH 13, preferably pH 10 to pH 12, based on a liquid temperature of 40°C, while the materials in the reaction vessel are appropriately stirred. One example of a reaction method is one in which the formed metal composite compound is not discharged outside the system, but is circulated within the system to promote particle growth of the metal composite compound.

[0040] In the method for producing a metal composite compound of the present invention, the concentration of the slurry containing the metal composite compound in the reaction tank is adjusted to 300 g / L or more. By providing a slurry concentrating step and a concentrated slurry reflux step described below, the concentration of the slurry containing the metal composite compound in the reaction tank can be adjusted to 300 g / L or more.

[0041] Since the secondary particles constituting the metal composite compound are an aggregate of multiple crystallites, it is believed that as the concentration of secondary particles present in the reaction tank increases, the reaction site in the reaction tank favors crystallite growth over crystallite nucleation, suppressing the generation of fine crystallites and reducing the variation in crystallite size, resulting in a metal composite compound having a relative standard deviation of less than 0.70. The concentration of the slurry containing the metal composite compound in the reaction tank can be measured by the following procedure. (1) A certain amount of slurry is pumped out from the reaction tank. (2) Measure the weight of the watch glass and filter paper. (3) The pumped slurry is filtered by suction and placed on a watch glass to dry. (4) Measure the weight of the solid content of the slurry in the reaction tank using the formula (solid content after drying + weight of watch glass + filter paper [g] - weight of watch glass + filter paper [g]). (5) Calculate the slurry concentration using the formula (weight of solids in the reaction tank [g] ÷ volume of pumped slurry [L]).

[0042] <Slurry concentration process> The slurry concentration step is a step in which a slurry containing a metal complex compound continuously extracted from a reaction tank is supplied to a settling tank, and the metal complex compound is allowed to settle in the settling tank, thereby concentrating the slurry containing the metal complex compound.

[0043] When the slurry containing the metal complex compound extracted from the reaction tank is fed to a settling tank, the slurry containing the concentrated metal complex compound is separated into the lower layer of the settling tank and the supernatant liquid is separated into the upper layer. The upper supernatant liquid is discharged to the outside of the system through an overflow pipe.

[0044] In the method for producing a metal composite compound of the present invention, the concentration of the slurry containing the concentrated metal composite compound (hereinafter sometimes referred to as "concentrated slurry") in the lower layer of the settling tank is adjusted to 400 g / L or more. The concentration of the concentrated slurry can be adjusted to 400 g / L or more by adjusting the residence time of the slurry containing the metal composite compound in the settling tank. By adjusting the concentration of the concentrated slurry to 400 g / L or more, the concentration of the slurry containing the metal composite compound in the reaction tank can be easily adjusted to 300 g / L or more. The concentration of the concentrated slurry in the settling tank can be calculated by dividing the amount of solids [g / min] returned from the settling tank to the reaction tank by the amount of liquid [L / min] returned from the settling tank to the reaction tank.

[0045] <Concentrated slurry reflux process> The concentrated slurry reflux process is a process in which the concentrated slurry, which has been adjusted to a concentration of 400 g / L or more, is returned from the settling tank to the reaction tank.

[0046] By returning the concentrated slurry adjusted to a concentration of 400 g / L or more from the settling tank to the reaction tank, the concentration of the slurry containing the metal complex compound in the reaction tank can be adjusted to 300 g / L or more. One method for returning the concentrated slurry from the settling tank to the reaction tank is to provide a liquid transfer pump in a reflux pipe connecting the settling tank and the reaction tank.

[0047] <Metal composite compound extraction process> In the metal composite compound extraction process, the flow of the slurry containing the metal composite compound circulating from the reaction tank to the reaction tank via the settling tank is stopped, and the slurry containing the metal composite compound is extracted from the reaction tank and the settling tank using a pump or the like, thereby extracting the metal composite compound as a product.

[0048] Furthermore, if necessary, the method may further include a solid-liquid separation step in which the slurry containing the metal composite compound obtained in the metal composite compound extraction step is filtered, the metal composite compound is washed with an alkaline aqueous solution, and then separated into a solid phase and a liquid phase to obtain a solid phase containing the metal composite compound. Furthermore, if necessary, the method may further include a step in which the solid phase containing the metal composite compound is dried to obtain a dry powder of the metal composite compound. Furthermore, if necessary, the solid phase may be washed with water or the like before drying.

[0049] Next, a method for producing the positive electrode active material of the present invention will be described. For example, in the method for producing the positive electrode active material of the present invention, a lithium compound is first added to the metal composite compound of the present invention to prepare a mixture of the metal composite compound 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.

[0050] The mixing ratio of the lithium compound and the metal composite compound may be, for example, such that the molar ratio of lithium in the lithium compound to the total amount of metals contained in the metal composite compound (total amount of nickel, cobalt as an optional component, and additional element M) is in the range of 1.00 or more and 1.10 or less.

[0051] Next, the mixture is fired to produce a positive electrode active material. Examples of firing conditions include a firing temperature of 600°C to 1000°C, a temperature rise rate of 50°C / h to 300°C / h, and a firing time of 5 hours to 20 hours. The firing atmosphere is not particularly limited, but examples include air and oxygen. The firing furnace used for firing is not particularly limited, but examples include a stationary box furnace and a roller hearth continuous furnace.

[0052] Next, a positive electrode using the positive electrode active material of the present invention 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 includes the positive electrode active material of the present invention, a binder, and, if necessary, a conductive additive. The conductive additive is not particularly limited as long as it can be used for non-aqueous electrolyte secondary batteries, and for example, a carbon-based material can be used. Examples of carbon-based materials include graphite powder, carbon black (e.g., acetylene black), and fibrous carbon materials. The binder is not particularly limited, but for example, a thermoplastic resin can be used. Examples of thermoplastic resins include polyvinylidene fluoride (PVdF), butadiene rubber (BR), polyvinyl alcohol (PVA), carboxymethyl cellulose (CMC), polytetrafluoroethylene (PTFE), etc., as well as combinations thereof. The positive electrode current collector is not particularly limited, but examples include conductive metal materials such as aluminum foil, nickel foil, and stainless steel.

[0053] In a method for producing a positive electrode, for example, a positive electrode active material, a conductive additive, and a binder are mixed to prepare a positive electrode active material slurry, which is then filled into a positive electrode current collector by a known filling method, dried, and then rolled and fixed by a press or the like.

[0054] A nonaqueous electrolyte secondary battery can be assembled by preparing a positive electrode using the positive electrode active material obtained as described above, a negative electrode, an electrolytic solution containing a predetermined electrolyte, and a separator by a known method.

[0055] The negative electrode may be an electrode in which a negative electrode active material layer using a negative electrode active material is supported on a negative electrode current collector, or an electrode made of the negative electrode active material alone. The negative electrode active material is not particularly limited as long as it is a commonly used material, and examples thereof include graphite such as natural graphite and artificial graphite, cokes, carbon black, pyrolytic carbons, carbon fiber, and organic polymer compound sintered bodies. The negative electrode current collector is not particularly limited, and examples thereof include metal materials such as copper foil, nickel foil, and stainless steel.

[0056] Furthermore, the negative electrode active material layer may further contain, as necessary, a conductive additive, a binder, etc. Examples of the conductive additive and binder include the same ones as those used in the positive electrode active material layer.

[0057] In a method for producing a negative electrode, for example, a negative electrode active material is mixed with, if necessary, a conductive additive and a binder, and water to prepare a negative electrode active material slurry. The negative electrode active material slurry is filled into a negative electrode current collector by a known filling method, dried, and then rolled and fixed by a press or the like.

[0058] The electrolytes contained in non-aqueous electrolytes include LiClO4, LiPF6, LiAsF6, LiSbF6, LiBF4, LiCF3SO3, LiN(SO2CF3)2, LiN(SO2C2F5)2, LiN(SO2CF3)(COCF3), Li(C4F9SO3), LiC(SO2CF3)3, Li2B 10 Cl 10 Examples of the lithium salt include LiBOB (here, BOB is bis(oxalato)borate), LiFSI (here, FSI is bis(fluorosulfonyl)imide), lithium salts of lower aliphatic carboxylic acids, and lithium salts such as LiAlCl4. These may be used alone or in combination of two or more.

[0059] Examples of the dispersion medium for the electrolyte 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; 1,2-dimethoxyethane, 1,3-dimethoxypropane, pentafluoropropyl methyl ether, 2,2,3,3-tetrafluoropropyl difluoromethyl ether, tetrahydrofuran, and 2-methyltetrahydrofuran. Examples of suitable organic solvents include ethers 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; and organic solvents containing fluoro groups (organic solvents in which one or more hydrogen atoms have been replaced with fluorine atoms). These may be used alone or in combination of two or more.

[0060] Alternatively, a solid electrolyte may be used instead of an electrolyte-containing electrolytic solution. Examples of solid electrolytes that can be used include organic polymer electrolytes such as polyethylene oxide polymer compounds, polymer compounds containing at least one of a polyorganosiloxane chain and a polyoxyalkylene chain. Also usable are so-called gel-type solid electrolytes in which a nonaqueous electrolytic solution is held in a polymer compound. Examples of inorganic solid electrolytes that contain sulfides include 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.

[0061] The separator is not particularly limited, but may be, for example, a material in the form of a porous film, nonwoven fabric, woven fabric, etc., made of a polyolefin resin such as polyethylene or polypropylene, a fluororesin, a nitrogen-containing aromatic polymer, etc. These may be used alone or in combination of two or more types. [Example]

[0062] Next, examples of the metal complex compound of the present invention will be described, but the present invention is not limited to these examples as long as they do not depart from the spirit of the invention.

[0063] Production of metal complex compounds of Examples and Comparative Examples Preparation of metal complex compound of Example 1 A metal-containing aqueous solution containing nickel, in which nickel sulfate, cobalt sulfate, and manganese sulfate were dissolved in a predetermined molar ratio of nickel:cobalt:manganese, and a sodium hydroxide aqueous solution were added dropwise to a reaction vessel having a predetermined volume. The temperature in the reaction vessel was maintained at 60°C, and the pH in the reaction vessel was maintained at 10.2 based on a liquid temperature of 40°C, while the mixture was continuously stirred with a stirrer. The produced metal complex compound was overflowed from the overflow pipe of the reaction vessel and supplied to a settling vessel having a predetermined volume. The metal complex compound was allowed to settle in the settling vessel for a predetermined time, and the slurry containing the metal complex compound was concentrated to obtain a concentrated slurry. The slurry concentration of the concentrated slurry that settled to the bottom of the settling vessel was 428 g / L. The concentrated slurry was then returned from the settling vessel to the reaction vessel. The above steps were continuously carried out for a predetermined time, and when the concentration of the slurry containing the metal composite compound in the reaction tank reached 315 g / L, the steps were terminated, and the slurry containing the metal composite compound was extracted from the reaction tank and the settling tank using a pump or the like, and the metal composite compound was removed from the system. The extracted metal composite compound was subjected to treatments of washing with water, dehydration, and drying, to obtain the metal composite compound as a product.

[0064] Preparation of metal complex compound of Example 2 A metal-containing aqueous solution containing nickel, in which nickel sulfate, cobalt sulfate, and manganese sulfate were dissolved at a predetermined molar ratio of nickel:cobalt:manganese, an ammonium sulfate aqueous solution (complexing agent), and a sodium hydroxide aqueous solution were added dropwise to a reaction tank having a predetermined volume, and the mixture was continuously stirred with a stirrer while maintaining the temperature in the reaction tank at 60° C. and the pH in the reaction tank at 10.3 based on a liquid temperature of 40° C. Further, a metal composite compound of Example 2 was obtained in the same manner as in Example 1, except that the concentration of the slurry containing the metal composite compound in the reaction tank was 346 g / L and the slurry concentration of the concentrated slurry that settled to the bottom layer of the settling tank was 473 g / L.

[0065] Preparation of metal complex compound of Example 3 A metal-containing aqueous solution containing nickel, in which nickel sulfate, cobalt sulfate, and manganese sulfate were dissolved at a predetermined molar ratio of nickel:cobalt:manganese, an ammonium sulfate aqueous solution (complexing agent), and a sodium hydroxide aqueous solution were added dropwise to a reaction tank having a predetermined volume, and the mixture was continuously stirred with a stirrer while maintaining the temperature in the reaction tank at 60° C. and the pH in the reaction tank at 10.7 based on a liquid temperature of 40° C. Further, a metal composite compound of Example 3 was obtained in the same manner as in Example 1, except that the concentration of the slurry containing the metal composite compound in the reaction tank was 308 g / L and the slurry concentration of the concentrated slurry that settled to the bottom layer of the settling tank was 400 g / L.

[0066] Preparation of metal complex compound of Example 4 A metal-containing aqueous solution containing nickel, in which nickel sulfate, cobalt sulfate, and manganese sulfate were dissolved at a predetermined molar ratio of nickel:cobalt:manganese, an ammonium sulfate aqueous solution (complexing agent), and a sodium hydroxide aqueous solution were added dropwise to a reaction tank having a predetermined volume, and the mixture was continuously stirred with a stirrer while maintaining the temperature in the reaction tank at 60° C. and the pH in the reaction tank at 10.8 based on a liquid temperature of 40° C. Further, a metal composite compound of Example 4 was obtained in the same manner as in Example 1, except that the concentration of the slurry containing the metal composite compound in the reaction tank was 322 g / L and the slurry concentration of the concentrated slurry that settled to the bottom layer of the settling tank was 420 g / L.

[0067] Preparation of metal composite compound of Comparative Example 1 A metal-containing aqueous solution containing nickel, in which nickel sulfate, cobalt sulfate, and manganese sulfate were dissolved at a predetermined molar ratio of nickel:cobalt:manganese, an ammonium sulfate aqueous solution (complexing agent), and a sodium hydroxide aqueous solution were added dropwise to a reaction tank having a predetermined volume, and the mixture was continuously stirred with a stirrer while maintaining the temperature in the reaction tank at 60° C. and the pH in the reaction tank at 11.2 based on a liquid temperature of 40° C. Further, a metal composite compound of Comparative Example 1 was obtained in the same manner as in Example 1, except that the concentration of the slurry containing the metal composite compound in the reaction tank was 263 g / L and the slurry concentration of the concentrated slurry that settled to the bottom layer of the settling tank was 307 g / L.

[0068] Preparation of metal composite compound of Comparative Example 2 A metal-containing aqueous solution containing nickel, in which nickel sulfate, cobalt sulfate, and manganese sulfate were dissolved at a predetermined molar ratio of nickel:cobalt:manganese, an ammonium sulfate aqueous solution (complexing agent), and a sodium hydroxide aqueous solution were added dropwise to a reaction tank having a predetermined volume, and the mixture was continuously stirred with a stirrer while maintaining the temperature in the reaction tank at 60° C. and the pH in the reaction tank at 10.5 based on a liquid temperature of 40° C. Further, a metal composite compound of Comparative Example 2 was obtained in the same manner as in Example 1, except that the concentration of the slurry containing the metal composite compound in the reaction tank was 254 g / L and the slurry concentration of the concentrated slurry that settled to the bottom layer of the settling tank was 484 g / L.

[0069] Preparation of metal composite compound of Comparative Example 3 A metal-containing aqueous solution containing nickel, in which nickel sulfate, cobalt sulfate, and manganese sulfate were dissolved at a predetermined molar ratio of nickel:cobalt:manganese, an ammonium sulfate aqueous solution (complexing agent), and a sodium hydroxide aqueous solution were added dropwise to a reaction vessel having a predetermined volume. The temperature in the reaction vessel was maintained at 71°C, and the pH in the reaction vessel was maintained at 11.2 based on a liquid temperature of 40°C, while the contents were continuously stirred with a stirrer. The produced metal composite compound was allowed to overflow and removed from the overflow pipe of the reaction vessel. The removed metal composite compound was subjected to treatments of washing with water, dehydration, and drying to obtain the metal composite compound of Comparative Example 3 as a product. The concentration of the slurry containing the metal composite compound in the reaction vessel was 116 g / L. From the above, in Comparative Example 3, the metal composite compound was not supplied from the reaction vessel to a settling vessel, and therefore a concentrated slurry was not prepared.

[0070] The evaluation items for the physical properties of the metal composite compounds of the examples and comparative examples are as follows.

[0071] (1) Composition analysis of metal complex compounds The composition analysis was carried out by dissolving the obtained metal composite compound in hydrochloric acid and then using an inductively coupled plasma emission spectrometer (Optima 8300, manufactured by PerkinElmer Japan Co., Ltd.).

[0072] (2) Relative standard deviation of volume-based crystallite size distribution calculated from diffraction peaks within the range of 2θ=38±1° The obtained metal complex compound was subjected to powder X-ray diffraction measurement (X-ray diffractometer: "Ultima IV", manufactured by Rigaku Corporation) using CuKα as the radiation source and a diffraction angle 2θ measurement range of 10° to 90°, and a diffraction peak was obtained within the range of 2θ = 38 ± 1°. The obtained diffraction peak data was read into analysis software (integrated powder X-ray analysis software "PDXL2", manufactured by Rigaku Corporation), analyzed using the FP method, and the analysis data was output as a normal logarithmic distribution. The relative standard deviation of the volume-based crystallite size distribution calculated from the diffraction peaks within the range of 2θ = 38 ± 1° was obtained.

[0073] (3) Tap density (g / mL) Measurement was carried out using a tap denser (KYT-4000, manufactured by Seishin Co., Ltd.) by the constant mass measurement method described in JIS R1628.

[0074] The evaluation results of the physical properties of the metal composite compounds of the examples and comparative examples are shown in Table 1 below.

[0075] Production of positive electrode active materials using metal composite compounds of Examples and Comparative Examples as precursors Lithium hydroxide powder was added to and mixed with the metal composite compounds of the examples and comparative examples so that the Li / (Ni+Co+Mn) molar ratio was 1.05, to obtain a mixture of the metal composite compound and lithium hydroxide. The resulting mixture was subjected to a calcination treatment to obtain a lithium metal composite oxide, which was used as the positive electrode active material. The calcination conditions were an oxygen atmosphere, a temperature increase rate of 175°C / h, a calcination temperature of 790°C, and a calcination time of 5 hours. A roller hearth kiln was used for the calcination.

[0076] Manufacturing of positive electrodes using positive electrode active materials A positive electrode was fabricated using the positive electrode active material obtained as described above, and a battery for evaluation was assembled using the fabricated positive electrode. Specifically, the positive electrode active material obtained, a conductive additive (acetylene black), and a binder (PVdF) were mixed in a weight ratio of 92:5:3, respectively, and the resulting mixture was applied to a positive electrode current collector (aluminum foil), dried, and pressed to adhere to the positive electrode current collector, thereby forming a positive electrode.

[0077] A lithium secondary battery was fabricated using the positive electrode obtained as described above, a negative electrode (metallic lithium), an electrolyte solution containing an electrolyte (LiPF6) (a mixed solution of ethylene carbonate: dimethyl carbonate: ethyl methyl carbonate in a volume ratio of 30:35:35), and a separator (made of polypropylene).

[0078] Evaluation items for lithium secondary batteries 1C discharge rate capacity The rate characteristics were determined by setting the 1.0 C capacity to 200 mAh / g, charging and discharging under the following conditions, and measuring the discharge capacity at 1.0 C. A rate capacity of 185 mAh / g or more during 1.0 C discharge was considered acceptable. Test temperature: 25℃ Maximum charging voltage 4.3V, charging current 1.0CA, constant current constant voltage charging Minimum discharge voltage 2.5V, discharge current 1.0CA, constant current discharge

[0079] The evaluation results of the lithium secondary batteries of the Examples and Comparative Examples are shown in Table 1 below.

[0080] [Table 1]

[0081] As can be seen from Table 1, the metal composite compounds of Examples 1 to 4, which were produced by adjusting the concentration of the slurry containing the metal composite compound in the reaction tank to 300 g / L or more and the concentration of the concentrated slurry in the lower layer of the settling tank to 400 g / L or more and had a relative standard deviation of less than 0.70, had a 1.0 C discharge rate capacity of 185 mAh / g or more, and exhibited excellent discharge characteristics. In particular, Examples 1, 3, and 4, which had a relative standard deviation of 0.65 or less, exhibited further improved 1.0 C discharge rate capacity.

[0082] Furthermore, the metal composite compounds of Examples 1 to 4 had tap densities of 1.2 g / mL to 1.7 g / mL.

[0083] On the other hand, as can be seen from Table 1, the metal composite compound of Comparative Example 1, in which the concentration of the slurry containing the metal composite compound in the reaction tank was less than 300 g / L, the concentration of the concentrated slurry in the lower layer of the settling tank was less than 400 g / L, and the relative standard deviation was 0.77, had a rate capacity of less than 185 mAh / g at 1.0 C discharge, and excellent discharge characteristics were not obtained. Also, the metal composite compound of Comparative Example 2, in which the concentration of the concentrated slurry in the lower layer of the settling tank was 400 g / L or more, but the concentration of the slurry containing the metal composite compound in the reaction tank was less than 300 g / L, and the relative standard deviation was 0.72, had a rate capacity of less than 185 mAh / g at 1.0 C discharge, and excellent discharge characteristics were not obtained. In addition, in the case of the metal composite compound of Comparative Example 3, in which the metal composite compound was not supplied from the reaction tank to the settling tank and a concentrated slurry was not prepared, and the relative standard deviation was 0.73, the rate capacity at 1.0C discharge was less than 185 mAh / g, and excellent discharge characteristics were not obtained.

[0084] Furthermore, the metal composite compounds of Comparative Examples 1 to 3 had tap densities of 2.0 g / mL to 2.1 g / mL. [Industrial Applicability]

[0085] When a positive electrode active material using the metal composite compound of the present invention as a precursor is used in a secondary battery, it can exhibit excellent discharge capacity, and therefore can be used in a wide range of secondary battery fields, such as portable devices and vehicles.

Claims

1. A metal complex compound having a relative standard deviation of less than 0.70 in volume-based crystallite size distribution calculated from diffraction peaks within the range of 2θ=38±1° in powder X-ray diffraction measurement using CuKα radiation.

2. The metal complex compound according to claim 1, having a tap density of 1.9 g / mL or less.

3. The following composition formula (I) Ni １－ｘ－ｙ Co ｘ M ｙ O ｚ (OH) ２－α ... Formula (I) (In formula (I), 0≦x≦0.3, 0≦y≦0.3, 0≦x+y≦0.3, 0≦z≦3, −0.5≦α≦2, and α−z<2 are satisfied, and M is one or more additive elements selected from the group consisting of Mn, Fe, Cu, Ti, Mg, Al, Zn, Sn, Zr, Nb, Ga, W, Mo, B, and Si.) The metal complex compound according to claim 1 or 2, represented by the formula (I).

4. 3. The metal complex compound according to claim 1, wherein the particle diameter at a cumulative volume percentage of 50% by volume (D50) is 7.0 μm or more and 20.0 μm or less.

5. 3. The metal complex compound according to claim 1, wherein the mode of the crystallite size in the crystallite size distribution is 30 Å or more and 200 Å or less.

6. 3. The metal complex compound according to claim 1, wherein the relative standard deviation is 0.30 or more.

7. A positive electrode active material for a non-aqueous electrolyte secondary battery, comprising the metal complex compound according to claim 1 or 2, fired with a lithium compound.

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