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

Abstract

Provided are: a metal composite compound capable of obtaining a positive electrode active material having an excellent capacity retention rate; and a positive electrode active material having the metal composite compound as a precursor. The metal composite compound has a relative standard deviation of 0.70 or more in a volume-based crystallite diameter distribution calculated on the basis of a diffraction peak in the range of 2 [theta] = 38 + / -1 DEG in a powder X-ray diffraction measurement using a CuK [alpha] ray.

Description

TECHNICAL FIELD

[0001] The present application relates to a metal complex compound and a positive electrode active material which is a precursor of the metal complex compound, and particularly relates to a metal complex compound and a positive electrode active material which is a precursor of the metal complex compound, capable of obtaining a positive electrode active material having an excellent capacity retention rate. BACKGROUND

[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 such as mobile phones and portable personal computers, and vehicles using or utilizing electric power as a power source. As the secondary battery, for example, a lithium ion secondary battery and the like using a nonaqueous electrolyte can be cited. The lithium ion secondary battery and the like using a nonaqueous electrolyte are suitable for miniaturization and weight reduction, and have characteristics of high capacity retention rate and high utilization rate.

[0003] In order to improve the battery characteristics of the lithium ion secondary battery, high battery capacity and high output power characteristics are required. Therefore, a hydroxide in which nickel is a main component, which is a lithium complex oxide for a lithium secondary battery positive electrode active material, is proposed (Patent Document 1), and in the X-ray diffraction profile using CuKa rays, the half-value width of the peak around 19° is in the range of 0.1° to 0.60°, the half-value width of the peak around 38° is in the range of 0.1° to 0.50°, and the half-value width of the peak around 52° is in the range of 0.1° to 0.65°.

[0004] In Patent Document 1, based on the recognition that the discharge capacity of the lithium complex oxide depends on the half-value width of the peak of the specific X-ray diffraction profile of the raw material hydroxide, by using a hydroxide in which nickel is a main component having a half-value width in a lower range as a raw material, a positive electrode active material lithium complex oxide having a high capacity can be obtained.

[0005] On the other hand, for example, in portable devices such as mobile phones and portable personal computers, electric vehicles using electric power as a power source, or hybrid vehicles using electric power as a power source, the nonaqueous electrolyte secondary battery as a power source requires characteristics of further improving the capacity retention rate. However, the precursor of the positive electrode active material of Patent Document 1 has room for improvement in terms of improving the capacity retention rate of the nonaqueous electrolyte secondary battery.

[0006] (Prior Art Documents) (Patent Documents) Patent Document 1: Japanese Patent Application Laid-Open No. 10-310433 SUMMARY

[0007] Problems to be Solved by the Invention In view of the above, an object of the present application is to provide a metal composite compound capable of obtaining a positive electrode active material having an excellent capacity retention rate, and a positive electrode active material that is a precursor of the metal composite compound.

[0008] Means for solving the problem In the metal composite compound of the present application, in powder X-ray diffraction measurement using CuKα rays, the relative standard deviation of the volume-based crystallite diameter distribution calculated from the diffraction peaks in the range of 2 θ = 38 ± 1° is adjusted to 0.70 or more. Thus, the metal composite compound of the present application is in a state in which the volume-based crystallite diameter distribution calculated from the diffraction peaks in the range of 2 θ = 38 ± 1° has a large degree of dispersion. In addition, the metal composite compound of the present application is a precursor of a positive electrode active material.

[0009] The gist of the present application is as follows.

[0010] [1] A metal composite compound, in powder X-ray diffraction measurement using CuKα rays, the relative standard deviation of the volume-based crystallite diameter distribution calculated from the diffraction peaks in the range of 2 θ = 38 ± 1° is 0.70 or more.

[0011] [2] The metal composite compound according to [1], wherein the tap density is greater than 1.5 g / mL.

[0012] [3] The metal composite compound according to [1] or [2], which is represented by 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 ≤ 0.4, 0 ≤ y ≤ 0.4, 0 ≤ x + y < 0.5, 0 ≤ z ≤ 3, -0.5 ≤ α ≤ 2, and α - z < 2 are satisfied, and M is one or more kinds of additive elements selected from the group consisting of Mn, Fe, Cu, Ti, Mg, Al, Zn, Sn, Zr, Nb, Ga, W, Mo, B, and Si.

[0013] The metal composite compound according to any one of [1] to [3], in which the cumulative volume percentage of the particle diameter, i.e., D50, is 7.0 μm or more and 20.0 μm or less.

[0014] The metal complex compound according to any one of [1] to [4], wherein the mode of the volume-based crystallite size distribution calculated from the diffraction peaks in the range of 2

[0015] The metal complex compound according to any one of [1] to [5], wherein the relative standard deviation is 1.20 or less.

[0016] A positive electrode active material of a nonaqueous electrolyte secondary battery, which is obtained by firing the metal complex compound according to any one of [1] to [6] with a lithium compound.

[0017] Effects of the Invention The metal complex compound according to the present invention has a relative standard deviation of the volume-based crystallite size distribution calculated from the diffraction peaks in the range of 2 θ = 38 ± 1° of 0.70 or more, and thus a positive electrode active material having an excellent capacity retention rate can be obtained.

[0018] The metal complex compound according to the present invention has a tap density of greater than 1.5 g / mL, and thus a more excellent capacity retention rate can be obtained.

[0019] The metal complex compound according to the present invention has a particle size (D50) of 7.0 μm or more and 20.0 μm or less at a cumulative volume percentage of 50 vol%, and thus the relative standard deviation of the volume-based crystallite size distribution calculated from the diffraction peaks in the range of 2 θ = 38 ± 1° is adjusted to 0.70 or more. DETAILED DESCRIPTION

[0020] The metal complex compound according to the present invention will be described in detail below.

[0021] The metal complex compound according to the present invention is a secondary particle formed by agglomeration of a plurality of primary particles. The particle shape of the metal complex compound according to the present invention is not particularly limited, and is various, and for example, a substantially spherical shape, a substantially elliptical shape, and the like can be given.

[0022] The metal complex compound according to the present invention has a relative standard deviation of the volume-based crystallite size distribution calculated from the diffraction peaks in the range of 2 θ = 38 ± 1° of 0.70 or more.

[0023] The metal complex compound according to the present invention has a relative standard deviation of the volume-based crystallite size distribution calculated from the diffraction peaks in the range of 2 θThe relative standard deviation of the volume-based crystallite diameter distribution calculated from the diffraction peaks within the range of 2θ = 38 ± 1° is 0.70 or more, and thus the positive electrode active material using the metal complex compound of the present application as a precursor has an excellent capacity retention rate.

[0024] The relative standard deviation of the crystallite diameter distribution of the metal complex compound of the present application is obtained by the following method.

[0025] First, the powder X-ray diffraction measurement is performed on the powdered metal complex compound, in which CuKα is used as a radiation source, and the measurement range of the diffraction angle 2θ is set to 10° or more and 90° or less, and the diffraction peaks within the range of 2θ = 38 ± 1° are obtained. As the X-ray diffractometer for the powder X-ray diffraction measurement, for example, Ultima IV manufactured by Rigaku Corporation can be cited.

[0026] The obtained diffraction peak data is read using an analysis software, and after the analysis is performed using the FP method, the analysis data is output in a logarithmic normal distribution form, and the relative standard deviation of the volume-based crystallite diameter distribution is obtained. As the analysis software, for example, X-ray powder comprehensive analysis software PDXL2 manufactured by Rigaku Corporation can be used.

[0027] The metal complex compound having the relative standard deviation of 0.70 or more means that the width of the crystallite diameter distribution is large, that is, the degree of dispersion of the crystallite size is increased. For the positive electrode active material obtained by firing the mixture of the metal complex compound having the increased degree of dispersion of the crystallite size and a lithium compound, since the large-sized crystallites absorb the small-sized crystallites and grow at the time of firing, the crystal growth of the positive electrode active material is promoted. As a result, the destruction of the crystal structure of the positive electrode active material at the time of charge and discharge is suppressed, the durability is improved, and an excellent capacity retention rate is exhibited.

[0028] The relative standard deviation is not particularly limited as long as it is 0.70 or more, however, from the aspect that the capacity retention rate of the positive electrode active material using the metal complex compound of the present application as a precursor is further improved, the lower limit value of the relative standard deviation is preferably 0.71 or more, and particularly preferably 0.72 or more. On the other hand, the upper limit value of the relative standard deviation can be cited, for example, 1.20 or less.

[0029] The upper limit value and the lower limit value of the relative standard deviation can be arbitrarily combined. The relative standard deviation is preferably 0.71 or more and 1.20 or less, and particularly preferably 0.72 or more and 1.20 or less.

[0030] The mode of the crystallite size of the crystallite diameter distribution can be obtained by analyzing the crystallite diameter distribution obtained by the above method using the above analysis software.

[0031] The mode of the crystallite size distribution in the crystallite diameter distribution is not particularly limited; however, from the perspective of promoting crystal growth of the positive electrode active material during the sintering of the mixture of metal composite compound and lithium compound, its lower limit is preferably 20 Å or more, and particularly preferably 30 Å or more. On the other hand, from the perspective of improving capacity retention due to crystallite expansion and contraction caused by charge and discharge, the upper limit of the mode of the crystallite size distribution in the crystallite diameter distribution is preferably 200 Å or less, more preferably 150 Å or less, and particularly preferably 130 Å or less.

[0032] The lower and upper limits of the mode can be combined arbitrarily. The mode is preferably 20 Å or more and 200 Å or less, more preferably 30 Å or more and 150 Å or less, and particularly preferably 30 Å or more and 130 Å or less.

[0033] The tap density of the metal composite compound of the present invention is not particularly limited. However, from the viewpoint of being able to obtain better capacity retention while increasing the filling density of the positive electrode active material, the lower limit is preferably greater than 1.5 g / mL, more preferably 1.7 g / mL or more, and particularly preferably 1.9 g / mL or more. On the other hand, from the viewpoint of suppressing particle breakage caused by increased particle density, the upper limit of the tap density is preferably 2.4 g / mL or less, more preferably 2.3 g / mL or less, and particularly preferably 2.2 g / mL or less.

[0034] The lower and upper limits of the tap density can be combined arbitrarily. From the perspective of obtaining a high filling density and better capacity retention of the positive electrode active material, while suppressing particle breakage, the tap density is preferably greater than 1.5 g / mL and less than 2.4 g / mL, more preferably greater than 1.7 g / mL and less than 2.3 g / mL, and particularly preferably greater than 1.9 g / mL and less than 2.2 g / mL.

[0035] The particle size (D50) of the metal composite compound of the present invention, with a cumulative volume percentage of 50%, is not particularly limited. However, from the perspective of increasing the filling density of the positive electrode active material to the positive electrode, 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. On the other hand, from the perspective of improving contact with the electrolyte, the upper limit of the 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. It should be noted that the above-mentioned lower and upper limits can be combined arbitrarily.

[0036] From the viewpoint that it is easy to adjust the relative standard deviation of the crystallite diameter distribution based on the volume reference calculated from the diffraction peaks in the range of 2θ = 38 ± 1° to 0.70 or higher, D50 is preferably 7.0 μm or higher and 20.0 μm or lower, more preferably 8.0 μm or higher and 19.0 μm or lower, and particularly preferably 10.0 μm or higher and 18.0 μm or lower. The aforementioned D50 refers to the particle size measured using a particle size distribution measuring device via laser diffraction / scattering.

[0037] Examples of metal composite compounds that can be used as components of the present invention include those using the following formula (I). Ni 1-x-y Co x M y O z (OH) 2-α ・・・Formula (I) (In formula (I), a metal composite compound, i.e. a nickel-containing hydroxide or nickel-containing oxide, is represented by satisfying 0≤x≤0.4, 0≤y≤0.4, 0≤x+y<0.5, 0≤z≤3, -0.5≤α≤2, and α-z<2, 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)

[0038] Wherein, the value of x is preferably 0.05≤x≤0.35, more preferably 0.07≤x≤0.30, and particularly preferably 0.10≤x≤0.25. Furthermore, the value of y is preferably 0.01≤y≤0.25, more preferably 0.02≤y≤0.20, and particularly preferably 0.03≤y≤0.17. Furthermore, the value of x+y is preferably 0.06≤x+y≤0.45, more preferably 0.10≤x+y≤0.32, and particularly preferably 0.12≤x+y≤0.30.

[0039] The metal composite compound of the present invention can be used as a precursor (hydroxide or oxide) for the positive electrode active material of non-aqueous electrolyte secondary batteries.

[0040] Next, the positive electrode active material (hereinafter sometimes simply referred to as "the positive electrode active material of the present invention") of a non-aqueous electrolyte secondary battery using the metal composite compound of the present invention as a precursor will be described. The positive electrode active material of the present invention is formed by calcining the metal composite compound of the present invention, for example, with a lithium compound. By calcining the metal composite compound of the present invention with a lithium compound, a non-aqueous electrolyte secondary battery with excellent capacity retention can be obtained.

[0041] The positive electrode active material of the present invention has a layered crystal structure. From the perspective of obtaining a secondary battery with high capacity retention, a trigonal, hexagonal, or monoclinic crystal structure is preferred. 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.

[0042] Next, a method for manufacturing the metal composite compound of the present invention will be described. The method for manufacturing the metal composite compound of the present invention includes a reaction step in which a metal-containing aqueous solution containing nickel, a complexing agent, and an alkaline aqueous solution are continuously fed into a reaction tank to carry out a crystallization reaction to obtain the metal composite compound. The reaction step is preferably carried out in a batch reaction tank or a continuous reaction tank.

[0043] <Reaction process for obtaining metal composites> The reaction process for obtaining the metal composite compound refers to the crystallization process, which involves adding a metal-containing aqueous solution containing nickel, a pH adjuster as an alkaline aqueous solution, and a complexing agent to a reaction tank and mixing them to allow the reaction solution to undergo a co-precipitation reaction, thereby obtaining the metal composite compound.

[0044] Specifically, a co-precipitation method is used to prepare a metal complex compound by appropriately adding a nickel-containing aqueous solution, an alkaline aqueous solution, and a complexing agent into a reaction tank. The nickel-containing aqueous solution contains a nickel salt (e.g., sulfate), a cobalt salt (e.g., sulfate) as a selective component, and a salt containing element M (e.g., sulfate). A neutralization reaction and crystallization occur within the reaction tank, thereby preparing a metal complex compound and obtaining a slurry-like suspension containing the metal complex compound. Water can be used as a solvent for the suspension, for example.

[0045] As a complexing agent, there are no particular limitations as long as it is a substance that can form a complex with nickel, cobalt as a selective component, and added element M in aqueous solution. Examples include ammonium ion donors (ammonium sulfate, ammonium chloride, ammonium carbonate, ammonium fluoride, etc.).

[0046] As an alkaline aqueous solution, there are no particular limitations as long as the pH value of the aqueous solution in the reaction tank is adjusted during co-precipitation. Examples include aqueous solutions of alkali metal hydroxides (such as sodium hydroxide and potassium hydroxide).

[0047] When the aforementioned aqueous solution containing nickel, an alkaline aqueous solution, and a complexing agent are continuously supplied to the reaction tank, nickel, cobalt (as a selective component), and added element M undergo a crystallization reaction to obtain a metal composite compound. The pH value of the aqueous solution containing nickel is, for example, pH 2 to pH 6 at a liquid temperature of 40°C. During the crystallization reaction, the temperature in the reaction tank is controlled, for example, within the range of 10°C to 80°C, preferably 20°C to 70°C; the pH value in the reaction tank is controlled, for example, within the range of pH 9 to pH 13, preferably pH 10 to pH 12 at a liquid temperature of 40°C; the ammonium ion concentration per 1L of slurry in the reaction tank is controlled within the range of 1g / L to 20g / L; and the solid component concentration of the slurry containing the metal composite compound in the reaction tank is controlled within the range of 50g / L to 300g / L. Simultaneously, the substances in the reaction tank are appropriately stirred.

[0048] In the method for manufacturing the metal composite compound of the present invention, the ratio of ammonium ion concentration to solid component concentration of the slurry per 1L of slurry in the reaction tank (ammonium ion concentration per 1L of slurry in the reaction tank / solid component concentration of the slurry in the reaction tank) is adjusted to 0.130 or less. Furthermore, in the method for manufacturing the metal composite compound of the present invention, the ratio of the pH value of the slurry at a liquid temperature of 40°C in the reaction tank to the pH value of the aqueous solution containing nickel at a liquid temperature of 40°C (pH value of the slurry at a liquid temperature of 40°C / pH value of the aqueous solution containing nickel at a liquid temperature of 40°C) is adjusted to greater than 2.00. By adjusting the ratio of ammonium ion concentration to solid component concentration to 0.130 or less in the slurry per 1L of slurry in the reaction tank, and adjusting the ratio of the pH value of the slurry at a liquid temperature of 40°C to the pH value of the aqueous solution containing nickel at a liquid temperature of 40°C to greater than 2.00, a metal composite compound with a relative standard deviation of 0.70 or more can be obtained.

[0049] The ratio of ammonium ion concentration per 1L of slurry in the reaction tank to the solids concentration of the slurry in the reaction tank is not particularly limited as long as it is 0.130 or less. However, from the perspective of obtaining a metal composite compound with a relative standard deviation of 0.70 or more, this value is preferably 0.100 or less, more preferably 0.070 or less, and particularly preferably 0.050 or less. As a lower limit value for the ratio of ammonium ion concentration per 1L of slurry in the reaction tank to the solids concentration of the slurry in the reaction tank, an example is 0.015 or more.

[0050] The pH value of the reaction tank slurry at a temperature of 40°C as a reference / the pH value of the metal-containing aqueous solution at a temperature of 40°C as a reference is not particularly limited as long as it is greater than 2.00. However, from the viewpoint of obtaining the metal composite compound with a relative standard deviation of 0.70 or more, it is preferred to be 2.05 or more, and particularly preferred to be 2.10 or more.

[0051] In a continuous reaction process, the prepared metal composite compound is continuously discharged from the reaction vessel through an overflow pipe. In a batch reaction process, after a predetermined reaction time, the reaction is stopped, and all the metal composite compound in the reaction vessel is discharged from the system using a pump or similar means.

[0052] The resulting slurry containing the metal complex can be subjected to solid-liquid separation, i.e., separated into a solid phase and a liquid phase by filtration, thereby obtaining a solid phase containing the metal complex. Furthermore, the solid phase can be washed with an alkaline aqueous solution during solid-liquid separation. Subsequently, the solid phase containing the metal complex can be dried.

[0053] Next, the method for manufacturing the positive electrode active material of the present invention will be described. For example, in the method for manufacturing 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. As for the lithium compound, there is no particular limitation as long as it is a compound containing lithium, and examples include lithium carbonate, lithium hydroxide, etc.

[0054] As a mixing ratio of lithium compound and metal composite compound, for example, the molar ratio of lithium in lithium compound to the total metal content of metal composite compound (total amount of nickel and cobalt as selective components and added element M) can be in the range of 1.00 or more and 1.10 or less.

[0055] Next, by calcining the above mixture, a positive electrode active material can be manufactured. Examples of calcination conditions include a calcination temperature of 600°C or higher and 1000°C or lower, a heating rate of 50°C / hour or higher and 300°C / hour or lower, and a calcination time of 5 hours or higher and 20 hours or lower. There are no particular limitations on the calcination atmosphere; examples include atmosphere and oxygen. Furthermore, there are no particular limitations on the calcination furnace used; examples include stationary box furnaces and roller hearth continuous furnaces.

[0056] Next, the 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 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 a conductive additive as needed. As a conductive additive, there are no particular limitations as long as it is a material suitable for use in non-aqueous electrolyte secondary batteries; for example, carbon-based materials can be used. Examples of carbon-based materials include graphite powder, carbon black (e.g., acetylene black), and fibrous carbon materials. As a binder, there are no particular limitations; for example, thermoplastic resins can be used. Examples of thermoplastic resins include polyvinylidene fluoride (PVdF), butadiene rubber (BR), polyvinyl alcohol (PVA), carboxymethyl cellulose (CMC), polytetrafluoroethylene (PTFE), and combinations thereof. As a positive electrode current collector, there are no particular limitations; for example, conductive metal materials such as aluminum foil, nickel foil, and stainless steel can be used.

[0057] One method for manufacturing the positive electrode is to mix a positive electrode active material, a conductive additive, and a binder to prepare a positive electrode active material slurry. This positive electrode active material slurry is then filled into a positive electrode current collector using a known filling method, dried, and then rolled and fixed by extrusion or similar means.

[0058] Using the positive electrode, negative electrode, electrolyte containing a specified electrolyte, and separator obtained as described above, a non-aqueous electrolyte secondary battery is assembled by a known method.

[0059] Examples of negative electrodes include electrodes formed by supporting a layer of negative electrode active material on a negative electrode current collector, and electrodes composed solely of the negative electrode active material. As for the negative electrode active material, there are no particular limitations as long as it is a commonly used negative electrode active material; examples include natural graphite, artificial graphite, coke, carbon black, thermally decomposed carbon, carbon fibers, and sintered organic polymer compounds. As for the negative electrode current collector, there are no particular limitations; examples include metallic materials such as copper foil, nickel foil, and stainless steel.

[0060] Furthermore, conductive additives, binders, etc., can be added to the negative electrode active material layer as needed. Examples of conductive additives and binders include substances identical to those used in the aforementioned positive electrode active material layer.

[0061] As a method for manufacturing the negative electrode, for example, a negative electrode active material slurry is prepared by mixing a negative electrode active material, a conductive additive and a binder as needed, and water. The negative electrode active material slurry is then filled into a negative electrode current collector using a known filling method, dried, and then rolled and fixed by extrusion or the like.

[0062] Examples of electrolytes included in non-aqueous electrolyte systems include LiClO4, LiPF6, LiAsF6, LiSbF6, LiBF4, LiCF3SO3, LiN(SO2CF3)2, LiN(SO2C2F5)2, LiN(SO2CF3)(COCF3), Li(C4F9SO3), LiC(SO2CF3)3, and Li2B. 10 Cl 10 Lithium salts such as LiBOB (where BOB stands for bis(oxalato)borate), LiFSI (where FSI stands for bis(fluorosulfonyl)imide), lower aliphatic carboxylic acid lithium salts, and LiAlCl4 can be used alone or in combination of two or more.

[0063] In addition, carbonates such as propylene carbonate, ethylene carbonate, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, 4-trifluoromethyl-1,3-dioxolane-2-one, and 1,2-di(methoxycarbonyloxy)ethane can be used as dispersion media; 1,2-dimethoxyethane, 1,3-dimethoxypropane, pentafluoropropyl methyl ether, 2,2,3,3-tetrafluoropropyl difluoromethyl ether, tetrahydrofuran, and 2-methyltetrahydrofuran can also be used. Ethers; esters such as methyl formate, methyl acetate, and γ-butyrolactone; nitrile compounds such as acetonitrile and butyronitrile; amides such as N,N-dimethylformamide and N,N-dimethylacetamide; carbamates such as 3-methyl-2-oxazolidinone; sulfur-containing compounds such as sulfolane, dimethyl sulfoxide, and 1,3-propanesulfonic acid lactone, or compounds further fluorinated with fluorine groups on these organic solvents (compounds in which one or more hydrogen atoms in the organic solvent are replaced by fluorine atoms). These can be used alone or in combination of two or more.

[0064] Alternatively, solid electrolytes can be used instead of electrolyte-containing liquids. Examples of solid electrolytes include organic polymeric electrolytes such as polyethylene oxide-based polymers, polymers containing at least one of polyorganosiloxane chains or polyoxyalkylene chains. Additionally, so-called gel-type electrolytes, which are held in a polymeric compound by a non-aqueous electrolyte, can also be used. Furthermore, examples 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 can be used individually or in combination of two or more.

[0065] There are no particular limitations on the spacer material; for example, materials such as porous membranes, nonwoven fabrics, and woven fabrics made of polyolefin resins such as polyethylene and polypropylene, fluoropolymers, and nitrogen-containing aromatic polymers can be used. These materials can be used alone or in combination of two or more.

[0066] Example The following describes examples of the metal composite compounds of the present invention, but the present invention is not limited to these examples as long as it does not depart from its spirit.

[0067] Preparation of metal composite compounds in the examples and comparative examples Preparation of the metal composite compound in Example 1 Water was added to a reaction vessel equipped with a rotary agitator with a stirring paddle and an overflow pipe, and the temperature inside the reaction vessel was heated to 70°C. An aqueous solution of nickel sulfate, an aqueous solution of cobalt sulfate, and an aqueous solution of manganese sulfate were mixed in a predetermined molar ratio of nickel:cobalt:manganese to prepare a nickel-containing metallic aqueous solution. Next, the aforementioned nickel-containing metallic aqueous solution, an ammonium sulfate aqueous solution as a complexing agent, and an aqueous solution of sodium hydroxide were continuously added to the reaction vessel under stirring to obtain a slurry containing a metal complex compound. At this time, while maintaining the temperature inside the reaction vessel, the ratio of ammonium ion concentration per liter of slurry to the solid content concentration of the slurry in the reaction vessel was adjusted to 0.019, and the ratio of the pH value of the slurry at a temperature of 40°C to the pH value of the nickel-containing metallic aqueous solution at a temperature of 40°C was adjusted to 2.24. The resulting slurry containing the metal complex compound was overflowed from the overflow pipe of the reaction vessel and removed. The extracted slurry containing the metal composite compound was subjected to solid-liquid separation. After cleaning the solid phase with an alkaline aqueous solution, the solid phase was dried to obtain the metal composite compound.

[0068] Preparation of the metal composite compound in Example 2 Water is added to a reaction vessel equipped with a rotary agitator with a stirring paddle and an overflow pipe, and the temperature inside the reaction vessel is heated to 60°C. An aqueous solution of nickel sulfate, an aqueous solution of cobalt sulfate, and an aqueous solution of manganese sulfate are mixed in a predetermined molar ratio of nickel:cobalt:manganese to prepare a nickel-containing metal-containing aqueous solution. Next, the aforementioned nickel-containing metal-containing aqueous solution, an ammonium sulfate aqueous solution as a complexing agent, and an aqueous solution of sodium hydroxide are continuously added to the reaction vessel under stirring to obtain a slurry containing a metal complex compound. At this time, while maintaining the temperature inside the reaction vessel, the ratio of ammonium ion concentration per liter of slurry in the reaction vessel to the solid content concentration of the slurry in the reaction vessel is adjusted to 0.019, and the ratio of the pH value of the slurry at a reference temperature of 40°C to the pH value of the nickel-containing metal-containing aqueous solution at a reference temperature of 40°C is adjusted to 2.10. The generated slurry is overflowed from the overflow pipe of the reaction vessel and supplied to a sedimentation tank with a predetermined volume. The metal complex compound is precipitated in the sedimentation tank for a predetermined time to obtain a concentrated slurry. After a specified time, the concentrated slurry is returned from the settling tank to the reaction tank. After the above process is repeated for the specified time, the slurry is extracted from the reaction tank and settling tank using a pump or the like, and the slurry containing the metal composite compound is removed from the system. Subsequent processes are performed in the same manner as in Example 1 to obtain the metal composite compound of Example 2.

[0069] Preparation of the metal composite compound in Example 3 Water was added to a reaction tank equipped with a rotary agitator with a stirring paddle and an overflow pipe, and the temperature inside the reaction tank was heated to 60°C. An aqueous solution of nickel sulfate, an aqueous solution of cobalt sulfate, and an aqueous solution of manganese sulfate were mixed in a predetermined molar ratio of nickel:cobalt:manganese to prepare a nickel-containing metal aqueous solution. Next, the aforementioned nickel-containing metal aqueous solution, an ammonium sulfate aqueous solution as a complexing agent, and an aqueous solution of sodium hydroxide were continuously added to the reaction tank under stirring to obtain a slurry containing a metal composite compound. At this time, while maintaining the temperature inside the reaction tank, the ratio of ammonium ion concentration per 1L of slurry in the reaction tank to the solid content concentration of the slurry in the reaction tank was adjusted to 0.018, and the ratio of the pH value of the slurry at a temperature of 40°C to the pH value of the nickel-containing metal aqueous solution at a temperature of 40°C was adjusted to 2.24. Subsequent steps were performed in the same manner as in Example 1 to obtain the metal composite compound of Example 3.

[0070] Preparation of the metal composite compound in Example 4 Water was added to a reaction vessel equipped with a rotary agitator with a stirring paddle and an overflow pipe, and the temperature inside the reaction vessel was heated to 71°C. An aqueous solution of nickel sulfate, an aqueous solution of cobalt sulfate, and an aqueous solution of manganese sulfate were mixed in a predetermined molar ratio of nickel:cobalt:manganese to prepare a nickel-containing metal aqueous solution. Next, the aforementioned nickel-containing metal aqueous solution, an ammonium sulfate aqueous solution as a complexing agent, and an aqueous solution of sodium hydroxide were continuously added to the reaction vessel under stirring to obtain a slurry containing a metal composite compound. At this time, while maintaining the temperature inside the reaction vessel, the ratio of ammonium ion concentration per liter of slurry in the reaction vessel to the solid content concentration of the slurry in the reaction vessel was adjusted to 0.022, and the ratio of the pH value of the slurry at a temperature of 40°C to the pH value of the nickel-containing metal aqueous solution at a temperature of 40°C was adjusted to 2.24. Subsequent procedures were performed in the same manner as in Example 1 to obtain the metal composite compound of Example 4.

[0071] Preparation of the metal composite compound of Comparative Example 1 Water was added to a reaction vessel equipped with a rotary agitator with a stirring paddle and an overflow pipe, and the temperature inside the reaction vessel was heated to 70°C. An aqueous solution of nickel sulfate, an aqueous solution of cobalt sulfate, and an aqueous solution of manganese sulfate were mixed in a predetermined molar ratio of nickel:cobalt:manganese to prepare a nickel-containing aqueous solution. Next, the aforementioned nickel-containing aqueous solution, an ammonium sulfate aqueous solution as a complexing agent, and an aqueous solution of sodium hydroxide were continuously added to the reaction vessel under stirring to obtain a slurry containing a metal composite compound. At this time, while maintaining the temperature inside the reaction vessel, the ratio of ammonium ion concentration per liter of slurry in the reaction vessel to the solid content concentration of the slurry in the reaction vessel was adjusted to 0.076, and the ratio of the pH value of the slurry at a temperature of 40°C to the pH value of the nickel-containing aqueous solution at a temperature of 40°C was adjusted to 2.00. The generated slurry containing the metal composite compound was overflowed from the overflow pipe of the reaction vessel and removed. Subsequent procedures were performed in the same manner as in Example 1 to obtain the metal composite compound of Comparative Example 1.

[0072] Preparation of the metal composite compound of Comparative Example 2 Water was added to a reaction vessel equipped with a rotary agitator with a stirring paddle and an overflow pipe, and the temperature inside the reaction vessel was heated to 70°C. An aqueous solution of nickel sulfate, an aqueous solution of cobalt sulfate, and an aqueous solution of manganese sulfate were mixed in a predetermined molar ratio of nickel:cobalt:manganese to prepare a nickel-containing aqueous solution. Next, the aforementioned nickel-containing aqueous solution, an ammonium sulfate aqueous solution as a complexing agent, and an aqueous solution of sodium hydroxide were continuously added to the reaction vessel under stirring to obtain a slurry containing a metal composite compound. At this time, while maintaining the temperature inside the reaction vessel, the ratio of ammonium ion concentration per liter of slurry in the reaction vessel to the solid content concentration of the slurry in the reaction vessel was adjusted to 0.138, and the ratio of the pH value of the slurry at a temperature of 40°C to the pH value of the nickel-containing aqueous solution at a temperature of 40°C was adjusted to 1.93. The generated slurry containing the metal composite compound was overflowed from the overflow pipe of the reaction vessel and removed. Subsequent procedures were performed in the same manner as in Example 1 to obtain the metal composite compound of Comparative Example 2.

[0073] Preparation of the metal composite compound of Comparative Example 3 Water was added to a reaction vessel equipped with a rotary agitator with a stirring paddle and an overflow pipe, and the temperature inside the reaction vessel was heated to 70°C. An aqueous solution of nickel sulfate, an aqueous solution of cobalt sulfate, and an aqueous solution of manganese sulfate were mixed in a predetermined molar ratio of nickel:cobalt:manganese to prepare a nickel-containing aqueous solution. Next, the aforementioned nickel-containing aqueous solution, an ammonium sulfate aqueous solution as a complexing agent, and an aqueous solution of sodium hydroxide were continuously added to the reaction vessel under stirring to obtain a slurry containing a metal composite compound. At this time, while maintaining the temperature inside the reaction vessel, the ratio of ammonium ion concentration per liter of slurry in the reaction vessel to the solid content concentration of the slurry in the reaction vessel was adjusted to 0.154, and the ratio of the pH value of the slurry at a temperature of 40°C to the pH value of the nickel-containing aqueous solution at a temperature of 40°C was adjusted to 2.12. The generated slurry containing the metal composite compound was overflowed from the overflow pipe of the reaction vessel and removed. Subsequent procedures were performed in the same manner as in Example 1 to obtain the metal composite compound of Comparative Example 3.

[0074] The evaluation items for the physical properties of the metal composite compounds in the examples and comparative examples are as follows.

[0075] (1) Compositional analysis of metal composite compounds The obtained metal composite compound was dissolved in hydrochloric acid and its composition was analyzed using an inductively coupled plasma light emission analyzer (PerkinElmer Japan, Optima 8300).

[0076] (2) The relative standard deviation of the crystallite diameter distribution of the volume reference, calculated from the diffraction peaks in the range of 2θ = 38 ± 1°. The obtained metal composite compound was subjected to powder X-ray diffraction (PXRD) analysis. CuKα was used as the X-ray source, and the diffraction angle 2θ was set to a range of 10° to 90°. The X-ray diffraction apparatus used was Rigaku's "Ultima IV," and diffraction peaks were obtained within the range of 2θ = 38 ± 1°. The obtained diffraction peak data were read using analysis software (X-ray powder analysis software "PDXL2," manufactured by Rigaku, Co., Ltd.). After analysis using the FP method, the analytical data were output in log-normal distribution form, yielding the relative standard deviation of the volume-based crystallite diameter distribution calculated from the diffraction peaks within the range of 2θ = 38 ± 1°.

[0077] (3) Tap density (g / mL) The density was measured using a tap densor (manufactured by Seishin Co., Ltd., KYT-4000) according to the mass determination method described in JIS R1628.

[0078] The evaluation results of the physical properties of the metal composite compounds of the examples and comparative examples are listed in Table 1 below.

[0079] Manufacturing of positive electrode active materials using metal composite compounds as precursors in the examples and comparative examples Lithium hydroxide powder was added to the metal composite compounds of the examples and comparative examples respectively, so that the molar ratio of Li / (Ni+Co+Mn) was 1.05, and mixed to obtain a mixture of the metal composite compound and lithium hydroxide. The resulting mixture was calcined to obtain a lithium metal composite oxide as the positive electrode active material. The calcination conditions were set as follows: under an oxygen atmosphere, a heating rate of 175°C / hour, a calcination temperature of 790°C, and a calcination time of 5 hours. A roller kiln was used for calcination.

[0080] Manufacturing of a positive electrode using a positive electrode active material The positive electrode is prepared using the positive electrode active material obtained as described above, and an evaluation battery is assembled using the prepared positive electrode. Specifically, the obtained positive electrode active material, conductive additive (acetylene black), and binder (PVdF) are mixed in a weight ratio of 92:5:3. The resulting mixture is coated onto the positive electrode current collector (aluminum foil), dried, and pressed to fix it onto the positive electrode current collector, thus serving as the positive electrode.

[0081] A lithium secondary battery is made using the positive electrode, negative electrode (lithium metal), electrolyte containing electrolyte (LiPF6) (a mixture of ethylene carbonate, dimethyl carbonate and ethyl methyl carbonate in a volume ratio of 30:35:35), and separator (made of polypropylene) obtained as described above.

[0082] Evaluation items for lithium secondary batteries Capacity retention (%) after 50 cycles The above-mentioned lithium secondary batteries were subjected to charge-discharge tests. At 25°C, the batteries were charged at a constant current and constant voltage of 0.2C to a voltage of 4.3V, and then discharged at a constant current of 0.2C to a voltage of 2.5V. This charge-discharge cycle was repeated four times, and the discharge capacity of the fourth cycle was taken as the initial capacity. Furthermore, at 25°C, constant current charge-discharge cycle tests were conducted with a charge rate of 0.5C and a discharge rate of 1C, at a charging end voltage of 4.3V and a discharging end voltage of 2.5V. The percentage of discharge capacity relative to the initial capacity after 50 cycles was calculated as the capacity retention rate; a capacity retention rate of 95% or higher was considered acceptable.

[0083] The evaluation results of the lithium secondary batteries of the examples and comparative examples are listed in Table 1 below.

[0084] Table 1 According to Table 1, in the metal composite compounds of Examples 1 to 4, which were manufactured by adjusting the ratio of ammonium ion concentration per 1L of slurry in the reaction tank to solid component concentration in the reaction tank to 0.130 or less, and adjusting the ratio of pH value at a liquid temperature of 40°C in the reaction tank slurry to pH value at a liquid temperature of 40°C in the metal-containing aqueous solution containing nickel to greater than 2.00, the capacity retention rate after 50 cycles was 98.0% or more, achieving excellent capacity retention.

[0085] In addition, the tap density of the metal composite compounds in Examples 1 to 4 is 2.0 g / mL to 2.1 g / mL.

[0086] On the other hand, according to Table 1, in the metal composite compounds of Comparative Examples 1 to 3, when the ammonium ion concentration per 1L of slurry in the reaction tank / the solid component concentration of the slurry in the reaction tank is greater than 0.130 and / or the pH value of the slurry at a temperature of 40°C in the reaction tank / the pH value of the metal-containing aqueous solution at a temperature of 40°C containing nickel is less than 2.00, the capacity retention rate after 50 cycles is less than 95%, and excellent capacity retention rate is not obtained.

[0087] In addition, the tap density of the metal composite compounds in Comparative Examples 1 to 3 was 1.0 g / mL to 1.5 g / mL.

[0088] Industrial availability When the positive electrode active material using the metal composite compound of the present invention as a precursor is used in a secondary battery, it can achieve excellent capacity retention, 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, characterized by, In the powder X-ray diffraction measurement using CuKα rays, the relative standard deviation of the volume-based crystallite diameter distribution calculated from the diffraction peaks in the range of 2θ = 38 ± 1° is 0.70 or more.

2. The metal composite compound according to claim 1, having a tap density of more than 1.5 g / mL.

3. The metal composite compound according to claim 1 or 2, represented by the following formula (I), Formula (I) wherein 0≤x≤0.4, 0≤y≤0.4, 0≤x+y<0.5, 0≤z≤3, -0.5≤α≤2, and α-z<2 are satisfied, and M is one or more selected from the group consisting of Mn, Fe, Cu, Ti, Mg, Al, Zn, Sn, Zr, Nb, Ga, W, Mo, B, and Si. Ni 1-x-y Co x M y O z (OH) 2-α ... Formula (I) 4. The metal composite compound according to claim 1 or 2, having a cumulative volume percentage of 50 vol% of a particle size D50 of 7.0 μm or more and 20.0 μm or less. The mode of the crystallite size of the crystallite diameter distribution is 20 A or more and 200 A or less.

5. The metal complex compound according to claim 1 or 2, wherein, The relative standard deviation is 1.20 or less.

6. The metal complex compound according to claim 1 or 2, wherein, 7. A positive electrode active material of a nonaqueous electrolyte secondary battery, which is obtained by firing the metal composite compound according to claim 1 or 2 with a lithium compound. ​

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