CN111868976B - Positive electrode compound - Google Patents

Positive electrode compound Download PDF

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Publication number
CN111868976B
CN111868976B CN201980020575.0A CN201980020575A CN111868976B CN 111868976 B CN111868976 B CN 111868976B CN 201980020575 A CN201980020575 A CN 201980020575A CN 111868976 B CN111868976 B CN 111868976B
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nickel
positive electrode
coating layer
less
core
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CN111868976A (en
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田中聪
花村直也
畑未来夫
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Tanaka Chemical Corp
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Tanaka Chemical Corp
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/362—Composites
    • H01M4/366—Composites as layered products
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01G—COMPOUNDS CONTAINING METALS NOT COVERED BY SUBCLASSES C01D OR C01F
    • C01G53/00—Compounds of nickel
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01G—COMPOUNDS CONTAINING METALS NOT COVERED BY SUBCLASSES C01D OR C01F
    • C01G53/00—Compounds of nickel
    • C01G53/006—Compounds containing, besides nickel, two or more other elements, with the exception of oxygen or hydrogen
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01G—COMPOUNDS CONTAINING METALS NOT COVERED BY SUBCLASSES C01D OR C01F
    • C01G53/00—Compounds of nickel
    • C01G53/40—Nickelates
    • C01G53/42—Nickelates containing alkali metals, e.g. LiNiO2
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/34—Gastight accumulators
    • H01M10/345—Gastight metal hydride accumulators
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/50—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/50—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese
    • H01M4/505—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese of mixed oxides or hydroxides containing manganese for inserting or intercalating light metals, e.g. LiMn2O4 or LiMn2OxFy
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/52—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/52—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron
    • H01M4/525—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron of mixed oxides or hydroxides containing iron, cobalt or nickel for inserting or intercalating light metals, e.g. LiNiO2, LiCoO2 or LiCoOxFy
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M2300/00—Electrolytes
    • H01M2300/0002—Aqueous electrolytes
    • H01M2300/0014—Alkaline electrolytes
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M2300/00—Electrolytes
    • H01M2300/0017—Non-aqueous electrolytes
    • H01M2300/0025—Organic electrolyte
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Abstract

The purpose of the present invention is to provide a positive electrode compound which has excellent utilization rate after being placed at a high temperature and in initial characteristics, and which has high conductivity. A compound for a positive electrode, which is a secondary particle obtained by agglomerating primary particles, and which has a core and a coating layer on the surface of the core, wherein the core contains a nickel composite hydroxide, and wherein the coating layer contains 500ppm or less of cobalt and 10ppm or less of phosphorus and contains nickel, and wherein the content of nickel in the coating layer is 6 to 20 parts by mass per 100 parts by mass of the core, and wherein the volume resistivity of the compound for a positive electrode is 1.5X10 Ω & cm or less.

Description

Positive electrode compound
Technical Field
The present invention relates to a positive electrode compound for a battery, and more particularly, to a positive electrode compound having high conductivity and excellent utilization after being left at high temperature.
Background
In order to improve the performance of the positive electrode compound of the battery, a coating layer containing a metal element may be formed on the surface of the metal hydroxide serving as a core. For example, as a positive electrode active material for an alkaline storage battery having a high positive electrode utilization ratio and improved cycle characteristics, a surface-modified nickel hydroxide having a surface of nickel hydroxide as a core coated with a cobalt oxide has been proposed (patent document 1).
However, in patent document 1, the positive electrode active material in which the surface of nickel hydroxide is coated with cobalt oxide can obtain good utilization and cycle characteristics at a temperature of 25 ℃, but there is room for improvement in utilization and conductivity after being left at a high temperature. In addition, the utilization rate in the initial characteristics also has room for improvement. Therefore, in patent document 1, when the positive electrode plate is manufactured, the conductivity is improved by adding a conductive auxiliary agent, thereby improving the utilization ratio.
As a method for forming a metal coating layer on the surface of nickel hydroxide, the following method has been proposed: while stirring nickel hydroxide particles in an electroless plating bath, a solution containing palladium chloride and hydrochloric acid as main components is injected to carry out electroless plating while supporting a palladium catalyst on the surfaces of nickel hydroxide particles, thereby forming an electroless plating coating layer (patent document 2). In patent document 2, the electroless plating layer is composed of a nickel-phosphorus composite coating film.
As described above, in patent document 2, the electroless plating layer contains a large amount of phosphorus element. However, phosphorus has room for improvement in terms of improving battery performance, particularly, utilization rate and conductivity after leaving the battery at high temperature and in initial characteristics.
Therefore, in patent document 2, when the positive electrode plate is manufactured, the conductivity is improved by adding the conductive auxiliary agent, thereby improving the utilization ratio.
Prior art literature
Patent literature
Patent document 1: japanese patent laid-open No. 2001-52695
Patent document 2: japanese patent application laid-open No. 2004-315946
Disclosure of Invention
Problems to be solved by the invention
In view of the above, an object of the present invention is to provide a positive electrode compound which is excellent in utilization ratio after being left at a high temperature and in initial characteristics, and which has high conductivity.
Means for solving the problems
An embodiment of the present invention relates to a positive electrode compound which is a secondary particle obtained by agglomerating primary particles, and which has a core containing a nickel composite hydroxide and a coating layer containing 500ppm or less of cobalt element and 10ppm or less of phosphorus element and containing nickel element on the surface of the core, wherein the content of nickel element in the coating layer is as follows: the volume resistivity of the positive electrode compound is 1.5X10 Ω cm or less, and the positive electrode compound is used as a positive electrode active material of an alkaline storage battery, with respect to 100 parts by mass of the core, from 6 parts by mass to 20 parts by mass.
An embodiment of the present invention relates to a positive electrode compound which is a secondary particle obtained by agglomerating primary particles, and which has a core containing a nickel composite hydroxide and a coating layer containing 500ppm or less of cobalt element and 10ppm or less of phosphorus element and containing nickel element on the surface of the core, wherein the content of nickel element in the coating layer is as follows: the volume resistivity of the positive electrode compound is 5.0X10 to 100 parts by mass of the core is 6 parts by mass or more and 20 parts by mass or less 2 Omega cm or less, and the positive electrode compound is used as a precursor of a positive electrode active material of a nonaqueous electrolyte secondary battery.
An embodiment of the present invention relates to a positive electrode compound which is a secondary particle obtained by agglomerating primary particles, and which has a core containing a nickel composite hydroxide and a coating layer containing 500ppm or less of cobalt element and 10ppm or less of phosphorus element and containing nickel element on the surface of the core, wherein the content of nickel element in the coating layer is as follows: the volume resistivity of the positive electrode compound is 1.5X10 to 100 parts by mass of the core is 6 parts by mass or more and 20 parts by mass or less 8 And omega cm or less, wherein the positive electrode compound is used as a positive electrode active material for a nonaqueous electrolyte secondary battery.
An embodiment of the present invention relates to a compound for a positive electrode, wherein the core contains at least 1 metal element selected from the group consisting of cobalt, zinc, manganese, lithium, magnesium, aluminum, zirconium, yttrium, ytterbium, and tungsten.
An embodiment of the present invention relates to a positive electrode compound, wherein the nickel element-containing coating layer has an average primary particle diameter of 10nm to 100 nm. In the present specification, the average primary particle diameter of the nickel element in the coating layer means: 10 primary particles are selected from an image obtained by observing the coating layer by a field emission scanning electron microscope (FE-SEM), and the average value of the values obtained by measuring the maximum diameter of the selected primary particles is measured.
The embodiment of the present invention relates to a positive electrode compound, which further contains a palladium compound.
An embodiment of the present invention relates to a compound for a positive electrode, wherein the core is represented by the following general formula (1),
Ni (1-x) M x (OH) 2+a (1)
(wherein x is more than 0 and less than or equal to 0.2, a is more than or equal to 0 and less than or equal to 0.2, and M represents at least 1 metal element selected from cobalt, zinc, manganese, magnesium, aluminum, yttrium and ytterbium).
An embodiment of the present invention relates to a compound for a positive electrode, wherein the core is represented by the following general formula (3),
Ni (1-z) P z (OH) 2+c (3)
(wherein z is more than 0 and less than or equal to 0.7,0 and less than or equal to c is more than or equal to 0.28, and P represents at least 1 metal element selected from cobalt, zinc, manganese, magnesium, aluminum, zirconium, yttrium, ytterbium and tungsten).
The embodiment of the present invention relates to a positive electrode active material for a nonaqueous electrolyte secondary battery, wherein the positive electrode compound is used as a precursor.
An embodiment of the present invention relates to a compound for a positive electrode, wherein the core is represented by the following general formula (2),
Li[Li y (Ni (1-b) N b ) 1-y ]O 2 (2)
(wherein b is more than 0 and less than or equal to 0.7,0 and y is more than or equal to 0.50, and N represents at least 1 metal element selected from cobalt, manganese, magnesium, aluminum, zirconium, yttrium, ytterbium and tungsten).
Effects of the invention
According to an embodiment of the present invention, a compound for a positive electrode having excellent utilization efficiency after being left to stand at a high temperature and in initial characteristics can be obtained by having a core containing a nickel composite hydroxide and a coating layer on the surface of the core, wherein the coating layer contains 500ppm or less of cobalt element, 10ppm or less of phosphorus element, and nickel element, and the content of nickel element in the coating layer is 6 parts by mass or more and 20 parts by mass or less relative to 100 parts by mass of the core. In addition, since the volume resistivity is 1.5X10. OMEGA.cm or less, a positive electrode compound having high conductivity can be obtained. Therefore, when the positive electrode plate is produced using the positive electrode compound, the positive electrode plate can obtain excellent conductivity even if the amount of the conductive additive added is reduced or the conductive additive is not added.
According to the embodiment of the present invention, the average primary particle diameter of the nickel element in the coating layer is 10nm to 100nm, and thus the nickel element particles in the coating layer can be made finer, and the conductivity of the positive electrode compound can be further improved.
Detailed Description
The positive electrode compound of the present invention will be described in detail below. The positive electrode compound of the present invention is a secondary particle obtained by agglomerating primary particles, and comprises a core and a coating layer on the surface of the core, wherein the core contains a nickel composite hydroxide, the cobalt element in the coating layer is 500ppm or less, the phosphorus element is 10ppm or less, and the nickel element is contained in the coating layer, the nickel element content in the coating layer is 6 parts by mass or more and 20 parts by mass or less relative to 100 parts by mass of the core, and the volume resistivity of the positive electrode compound is 1.5x10Ω·cm or less. Accordingly, the positive electrode compound of the present invention is a particle having a core-shell structure, and is formed as a nickel-containing coated nickel composite hydroxide having a nickel-containing composite hydroxide particle core and a nickel-containing coating layer.
The particle shape of the positive electrode compound of the present invention is not particularly limited, and examples thereof include approximately spherical shapes.
The positive electrode compound of the present invention is a secondary particle formed by agglomerating a plurality of primary particles. The volume resistivity of the positive electrode compound of the present invention is 1.5X10. Omega. Cm or less. It is considered that the miniaturization of nickel element in the coating layer contributes to the improvement of conductivity. The volume resistivity of the positive electrode compound is not particularly limited as long as it is 1.5X10. OMEGA.cm or less, and is preferably low, for example, more preferably 1.5Ω.cm or less, and further preferablyPreferably 1.0X10 -1 Omega cm or less, particularly preferably 2.0X10 -2 Omega cm or less. The lower limit of the volume resistivity of the positive electrode compound is not particularly limited, and is, for example, 1.0X10 from the viewpoint of enabling efficient production -4 Ω·cm。
The particle size distribution of the positive electrode compound is not particularly limited, and for example, the lower limit of the secondary particle diameter D50 (hereinafter, may be simply referred to as "D50") having a cumulative volume percentage of 50% is preferably 2.0 μm, more preferably 2.5 μm, and particularly preferably 3.0 μm from the viewpoint of obtaining high temperature resistance. On the other hand, the upper limit of D50 of the positive electrode compound is preferably 30.0 μm, particularly preferably 25.0 μm, from the viewpoints of improving the density and securing the balance of the contact surface with the electrolyte. The lower limit value and the upper limit value may be arbitrarily combined.
The composition of the core of the positive electrode compound is not particularly limited as long as it is a composition containing a hydroxide of nickel, and may be a hydroxide further containing at least 1 metal element selected from the group consisting of cobalt, zinc, manganese, lithium, magnesium, aluminum, zirconium, yttrium, ytterbium, and tungsten, if necessary, in addition to nickel.
The positive electrode compound of the present invention can be used, for example, as a positive electrode active material for an alkaline storage battery, a positive electrode active material for a nonaqueous electrolyte secondary battery, or a precursor of a positive electrode active material for a nonaqueous electrolyte secondary battery.
In the case where the positive electrode compound of the present invention is used as a positive electrode active material for an alkaline storage battery, the composition of the core may be represented by the following general formula (1),
Ni (1-x) M x (OH) 2+a ……(1)
(wherein x is 0 < 0.2, a is 0.2, and M represents at least 1 metal element selected from the group consisting of cobalt, zinc, manganese, magnesium, aluminum, yttrium, and ytterbium).
In the case where the positive electrode compound of the present invention is used as a positive electrode active material of a nonaqueous electrolyte secondary battery, the composition of the core may be represented by the following general formula (2),
Li[Li y (Ni (1-b) N b ) 1-y ]O 2 (2)
(wherein b is more than 0 and less than or equal to 0.7,0 and y is more than or equal to 0.50, and N represents at least 1 metal element selected from the group consisting of cobalt, manganese, magnesium, aluminum, zirconium, yttrium, ytterbium and tungsten).
A lithium ion is added to a nickel composite hydroxide and firing is performed to prepare a core (for example, a core represented by the general formula (2)), and a coating layer containing a cobalt element of 500ppm or less, a phosphorus element of 10ppm or less, and a nickel element is formed on the obtained core, whereby a positive electrode compound for a positive electrode active material for a nonaqueous electrolyte secondary battery is obtained, wherein the content of the nickel element in the coating layer is 6 parts by mass or more and 20 parts by mass or less relative to 100 parts by mass of the core.
In the case where the positive electrode compound of the present invention is used as a precursor of a positive electrode active material for a nonaqueous electrolyte secondary battery, the composition of the core may be represented by the following general formula (3),
Ni (1-z) P z (OH) 2+c (3)
(wherein z is more than 0 and less than or equal to 0.7,0 and less than or equal to c is more than or equal to 0.28, and P represents at least 1 metal element selected from the group consisting of cobalt, zinc, manganese, magnesium, aluminum, zirconium, yttrium, ytterbium and tungsten).
The positive electrode active material of the nonaqueous electrolyte secondary battery can be obtained by further adding lithium ions to the nickel-containing nickel-coated composite hydroxide, that is, the positive electrode compound of the present invention (for example, the nickel-containing nickel-coated composite hydroxide having a core represented by the general formula (3)) and firing the mixture. As described above, examples of the nonaqueous electrolyte secondary battery include lithium ion secondary batteries.
In the positive electrode compound of the present invention, the surface of the core is coated with a coating layer containing 500ppm or less of cobalt element, 10ppm or less of phosphorus element, and nickel element. The content of the cobalt element and the phosphorus element is the content in the coating layer. The positive electrode compound of the present invention is coated with the coating layer, thereby improving the utilization ratio and reducing the volume resistivity after being left at a high temperature (for example, about 90 ℃) and in the initial characteristics. The content of cobalt element is not particularly limited as long as it is 500ppm or less, and is preferably 200ppm or less, more preferably 100ppm or less, still more preferably 50ppm or less, and particularly preferably 10ppm or less, from the viewpoint of more reliably improving the utilization ratio after being left at high temperature and in the initial characteristics and more reliably reducing the volume resistivity. The content of the phosphorus element is not particularly limited as long as it is 10ppm or less, and is more preferably 5ppm or less, particularly preferably 2ppm or less, from the viewpoint of more reliably improving the utilization ratio after being left at high temperature and in the initial characteristics and more reliably reducing the volume resistivity. As described above, the main component of the coating layer containing nickel element is nickel element.
As described above, the composition of the coating layer containing nickel element is as follows: the cobalt element is 500ppm or less and the phosphorus element is 10ppm or less, and is mainly composed of nickel element. For example, the content of nickel in the coating layer is preferably 99 mass% or more, more preferably 99.9 mass% or more, and particularly preferably 100 mass% from the viewpoint of more reliably improving the utilization ratio after being left at high temperature and in the initial characteristics.
The content of nickel element in the coating layer is in a range of 6 to 20 parts by mass based on 100 parts by mass of the core. When the content of nickel element in the coating layer is 6 parts by mass or more and 20 parts by mass or less relative to 100 parts by mass of the core, not only the initial characteristics but also excellent utilization ratio after being left at high temperature can be obtained and the volume resistivity can be reduced. The content of nickel element in the coating layer is not particularly limited as long as it is 6 parts by mass or more and 20 parts by mass or less relative to 100 parts by mass of the core, and from the viewpoint of further reducing the volume resistivity and further improving the utilization ratio after leaving at high temperature and in the initial characteristics, it is particularly preferably 7 parts by mass or more and 15 parts by mass or less relative to 100 parts by mass of the core.
The nickel element in the coating layer is in a particle shape. The surface of the core containing the nickel composite hydroxide is coated with nickel particles in a state of being overlapped. The shape of each nickel element in the coating layer is not particularly limited, and is, for example, approximately spherical.
The average primary particle diameter of the nickel element in the coating layer is not particularly limited, and is preferably in the range of 10nm to 100nm. Since the nickel element in the coating layer has an average primary particle diameter of 10nm to 100nm, and thus the nickel element is miniaturized, the surface of the coating layer can be smoothed and densified, and the conductivity of the positive electrode compound can be further improved, that is, the volume resistivity can be further reduced. The average primary particle diameter of the nickel element in the coating layer is more preferably 20nm to 80nm, particularly preferably 30nm to 70nm. The coating layer containing the nickel element may cover the entire surface of the core containing the nickel composite hydroxide, or may cover a partial region of the surface of the core containing the nickel composite hydroxide.
The average thickness of the coating layer is not particularly limited, but for example, the lower limit is preferably 20nm, particularly preferably 70nm, from the viewpoint of more reliably reducing the volume resistivity. On the other hand, the core contributes mainly to the battery characteristics of the positive electrode compound, and the upper limit thereof is preferably 200nm, particularly preferably 100nm, from the viewpoint of reliably maintaining the excellent battery characteristics of the positive electrode compound.
As described later, a palladium catalyst is used in the production of the positive electrode compound of the present invention. Therefore, the positive electrode compound of the present invention contains a small amount of the palladium compound. The content of palladium element in the positive electrode compound is, for example, 1ppm to 100 ppm.
The BET specific surface area of the positive electrode compound of the present invention is not particularly limited, and the lower limit is preferably 0.1m from the viewpoints of increasing the density and securing balance of the contact surface with the electrolyte, for example 2 Per g, particularly preferably 0.3m 2 And/g. On the other hand, the upper limit is preferably 50.0m 2 Preferably 40.0m 2 And/g. The lower limit value and the upper limit value may be arbitrarily combined.
The tap density of the positive electrode compound of the present invention is not particularly limited, but is preferably 1.5g/cm from the viewpoint of improving the filling degree when used as a positive electrode active material 3 The above is particularly preferably 1.7g/cm 3 The above.
The bulk density of the positive electrode compound of the present invention is not particularly limited, and is preferably 0.8g/cm from the viewpoint of improving the filling degree when used as a positive electrode active material 3 The above is particularly preferably 1.0g/cm 3 The above.
Next, a method for producing the positive electrode compound of the present invention will be described.
As the above production method, for example, nickel composite hydroxide particles as nuclei are first prepared. As for the production method of nickel composite hydroxide particles, first, a salt solution of nickel (for example, a sulfate solution) or a salt solution of nickel and other metal elements (for example, cobalt, zinc, manganese, lithium, magnesium, aluminum, zirconium, yttrium, ytterbium, and/or tungsten) (for example, a sulfate solution) is reacted with a complexing agent by a coprecipitation method, thereby producing nickel composite hydroxide particles (for example, hydroxide particles containing nickel hydroxide particles, nickel and other metal elements (for example, cobalt, zinc, manganese, lithium, magnesium, aluminum, zirconium, yttrium, ytterbium, and/or tungsten) and obtaining a slurry-like suspension containing nickel composite hydroxide particles. As the solvent for the suspension, for example, water is used.
The complexing agent is not particularly limited as long as it can form a complex with ions of nickel and the other metal elements in an aqueous solution, and examples thereof include ammonium ion donors (ammonium sulfate, ammonium chloride, ammonium carbonate, ammonium fluoride, and the like), hydrazine, ethylenediamine tetraacetic acid, nitrilotriacetic acid, uracil diacetic acid, and glycine. In the precipitation, an alkali metal hydroxide (e.g., sodium hydroxide, potassium hydroxide) may be added as needed to adjust the pH of the aqueous solution.
When a complexing agent is continuously supplied to the reaction tank in addition to the salt solution, nickel and the other metal elements are reacted to prepare nickel composite hydroxide particles. In the reaction, the temperature of the reaction vessel is controlled to be, for example, 10 to 80 ℃, preferably 20 to 70 ℃, the pH value in the reaction vessel is controlled to be, for example, 9 to 13, preferably 11 to 13, based on the liquid temperature of 25 ℃, and the materials in the reaction vessel are appropriately stirred. Examples of the reaction tank include a continuous reaction tank overflowed to separate nickel composite hydroxide particles formed.
Next, the palladium catalyst and the surfactant are supplied to the nickel composite hydroxide particles as nuclei obtained in the above manner, and the palladium catalyst is supported on the surfaces of the nickel composite hydroxide particles. Then, nickel composite hydroxide particles carrying a palladium catalyst are immersed in a plating solution containing no phosphorus element and mainly nickel, and a hydrazine additive is added thereto to perform electroless plating, whereby nickel is plated on the surfaces of the nickel composite hydroxide particles. In electroless plating, the film thickness and/or the composition of the plating solution are adjusted so that the content of nickel element in the coating layer is 6 parts by mass or more and 20 parts by mass or less with respect to 100 parts by mass of the core, thereby forming a plated film on the surfaces of the nickel composite hydroxide particles. Thus, a nickel-containing coating layer containing 500ppm or less of cobalt element and 10ppm or less of phosphorus element can be formed.
In the above method for forming a coating layer by electroless plating, the average primary particle diameter of nickel element in the coating layer is in the range of 10nm to 100 nm. If the palladium-based catalyst is not supported on the surface of the nickel composite hydroxide particles, the average primary particle diameter of the nickel element in the coating layer becomes coarse and exceeds 100nm, and the surface of the coating layer becomes coarse and coarsens, so that a volume resistivity of 1.5X10. OMEGA.cm or less cannot be obtained.
Next, a positive electrode using the positive electrode compound of the present invention will be described. The following describes the case of using the positive electrode compound of the present invention as a positive electrode of an alkaline storage battery such as a nickel-hydrogen secondary battery or a nonaqueous electrolyte secondary battery. 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 containing the positive electrode compound of the present invention. The positive electrode active material layer contains a positive electrode active material, which is the positive electrode compound of the present invention, a binder (binder), and a small amount of a conductive auxiliary agent according to the conditions of use and the like. As described above, the positive electrode compound of the present invention has a low volume resistivity, and therefore can impart a predetermined conductivity to the positive electrode in some cases without adding a conductive auxiliary agent. The conductive auxiliary agent is not particularly limited as long as it is a conductive auxiliary agent that can be used in, for example, a livestock battery (secondary battery), and Acetylene Black (AB), metallic cobalt, cobalt oxide, or the like can be used. The binder is not particularly limited, and examples thereof include polymer resins such as polyvinylidene fluoride (PVdF), butadiene Rubber (BR), polyvinyl alcohol (PVA), carboxymethyl cellulose (CMC), polytetrafluoroethylene (PTFE), and the like, and combinations thereof. The positive electrode current collector is not particularly limited, and examples thereof include punched metal, expanded metal, metal mesh, foamed metal (for example, foamed nickel), mesh-shaped metal fiber sintered body, metal-plated resin plate, and the like.
As a method for producing an alkaline storage battery such as a nickel-hydrogen secondary battery or a positive electrode of a nonaqueous electrolyte secondary battery, for example, a positive electrode compound of the present invention, a conductive auxiliary agent, a binder and water are first mixed to prepare a positive electrode active material slurry. Next, the positive electrode active material slurry is filled into a positive electrode current collector by a known filling method, dried, and then rolled and fixed by pressing or the like, whereby a positive electrode can be obtained.
In the case of using the positive electrode compound of the present invention as a precursor of a positive electrode active material for a nonaqueous electrolyte secondary battery such as a lithium ion secondary battery, a lithium compound such as lithium carbonate or lithium hydroxide is added to the positive electrode compound of the present invention to obtain a mixture of the lithium compound and the positive electrode compound, and the obtained mixture is subjected to primary firing (firing temperature of 600 ℃ to 900 ℃ for 5 hours to 20 hours, for example) and further to secondary firing (firing temperature of 700 ℃ to 1000 ℃ for 1 hour to 20 hours, for example), whereby a positive electrode active material for a nonaqueous electrolyte secondary battery such as a lithium ion secondary battery can be obtained. A positive electrode for a nonaqueous electrolyte secondary battery such as a lithium ion secondary battery is provided with a positive electrode collector and a positive electrode active material layer formed on the surface of the positive electrode collector and using the positive electrode compound of the present invention as a precursor. The positive electrode active material layer contains a positive electrode active material using the positive electrode compound of the present invention as a precursor, a binder (binder), and a conductive auxiliary agent added as necessary. As the positive electrode current collector, the binder, and the conductive additive, the same positive electrode current collector, binder, and conductive additive as described above can be used.
As a method for producing a positive electrode of a nonaqueous electrolyte secondary battery such as a lithium ion secondary battery, for example, a positive electrode active material using the positive electrode compound of the present invention as a precursor, a conductive auxiliary agent, a binder, and N-methyl-2-pyrrolidone (NMP) are first mixed to prepare a positive electrode active material slurry. Next, the positive electrode active material slurry is filled into a positive electrode current collector by a known filling method, dried, and then rolled and fixed by pressing or the like, whereby a positive electrode can be obtained.
A positive electrode using the positive electrode active material obtained in the above manner, a negative electrode including a negative electrode current collector and a negative electrode active material layer containing a negative electrode active material formed on the surface of the negative electrode current collector, a predetermined electrolyte, and a separator are mounted by a known method, whereby a battery (for example, an alkaline battery, a nonaqueous electrolyte secondary battery, or the like) can be assembled.
Examples
Next, embodiments of the present invention will be described, but the present invention is not limited to the above examples unless departing from the spirit of the present invention.
Method for producing Compound for Positive electrode of examples 1 and 2
Preparation of Nickel composite hydroxide particles
An aqueous solution of ammonium sulfate and an aqueous solution of sodium hydroxide were added dropwise to an aqueous solution in which nickel sulfate, cobalt sulfate and zinc sulfate were dissolved in a predetermined ratio (nickel: cobalt: zinc=92.1:1.12:6.77 by mass ratio) in a reaction tank with a stirrer, and the reaction was continuously stirred at a stirring speed of 520rpm by a propeller stirrer with stirring blades while maintaining a reaction temperature of 45.0 ℃ and a reaction pH of 12.1 at 40 ℃ with a liquid temperature reference in the reaction tank having a reaction volume of 500L. The produced hydroxide was overflowed from the overflow pipe of the reaction tank and taken out. The extracted hydroxide is subjected to each treatment of washing with water, dehydration, and drying, whereby nickel composite hydroxide particles as nuclei are obtained. The composition of the obtained nickel composite hydroxide particles was confirmed by an inductively coupled plasma spectrometry apparatus as follows: the content of nickel element was 92.1 parts by mass, the content of cobalt element was 1.12 parts by mass, and the content of zinc element was 6.77 parts by mass.
The nickel composite hydroxide particles prepared as described above are directly subjected to electroless pure nickel plating treatment, whereby a nickel composite hydroxide having a nickel plating film as a coating layer, that is, a nickel-coated nickel composite hydroxide is produced. More specifically, a nickel composite hydroxide having a nickel plating film was produced in the following manner.
First, nickel composite hydroxide particles having a particle diameter of 10 μm were used as base particles, and the base particles were stirred with a cationic surfactant for 10 minutes in order to modify the surfaces of the base particles. Then, after the filtration and water washing, stirring treatment was performed for 10 minutes with a palladium ion catalyst solution, thereby adsorbing palladium ions on the surfaces of the substrate particles. After the filtration and water washing, the palladium catalyst was carried on the surface of the base particles by stirring the solution for 10 minutes. Then, after the filtration and water washing, the substrate particles having the palladium catalyst supported on the surface were pre-stirred in a nickel sulfate solution heated to 80 ℃ for 1 minute. The composition of the nickel sulfate solution was as follows: the nickel salt is 0.30mol/L, the citrate is 1mol/L, and the carbonate is 1.7mol/L. Then, hydrazine monohydrate was added to the nickel sulfate solution in an amount of 0.4 mol/L. After the reaction starts, the substrate particles having the palladium catalyst supported on the surface thereof are stirred for 5 minutes or more in a nickel sulfate solution containing hydrazine monohydrate, whereby a nickel plating film is gradually formed on the surfaces of the nickel composite hydroxide particles and a coating layer containing nickel element is formed. After stirring, the nickel composite hydroxide particles having the coating layer containing nickel element formed thereon were washed with water by filtration and dried at a temperature of 80 ℃. Thus, nickel-containing coated nickel composite hydroxide particles as a positive electrode compound according to the present invention were obtained. The content of nickel element (7.5 parts by mass, 10 parts by mass) in the coating layer of the nickel composite hydroxide particles was adjusted to 100 parts by mass by adjusting the amount of the nickel sulfate solution to be charged.
Method for producing Compound for Positive electrode of comparative example 1
Nickel composite hydroxide particles as cores were obtained in the same manner as in the above examples. Then, the nickel composite hydroxide particles as nuclei were put into an aqueous alkali solution in a reaction bath in which the pH at 50 ℃ was maintained at 9.0 with sodium hydroxide as a liquid temperature reference. After the addition, the solution was stirred and an aqueous cobalt sulfate solution having a concentration of 90g/L was added dropwise. During this period, an aqueous sodium hydroxide solution was appropriately added dropwise, and the pH of the reaction bath at a liquid temperature of 50 ℃ was maintained at 9.0 for 1 hour, whereby cobalt hydroxide-coated nickel composite hydroxide particles were obtained in which a coating layer composed of cobalt hydroxide was formed on the surfaces of the nickel composite hydroxide particles (cores). The cobalt content of the coating was 2.6 parts by mass per 100 parts by mass of the nickel composite hydroxide particles.
Then, 7Kg of the obtained cobalt hydroxide-coated nickel composite hydroxide particles were charged into a high-speed mixer (model FMD-25J, manufactured by POWTEC Co., ltd.) having a capacity of 25L. Then, while introducing air into the stirring and mixing device from the inlet port of the stirring and mixing device and exhausting air from the exhaust port, the main stirring blade at the bottom of the stirring and mixing device was rotated at 200rpm, and the sub stirring blade at the side wall of the stirring and mixing device was rotated at 1200rpm, whereby the cobalt hydroxide-coated nickel composite hydroxide particles were mixed. The temperature of the sample in the stirring and mixing apparatus was brought to almost 90℃by heating with the heating jacket while continuing to mix, and then 0.4L of a 48 mass% aqueous sodium hydroxide solution was sprayed in mist form from the spraying apparatus into the stirring and mixing apparatus during about 2 minutes. After the end of the spraying, the temperature in the stirring and mixing device was heated to about 120 ℃ during about 30 minutes, and the color of the particle surface changed from light pink to black. Then, the temperature in the stirring and mixing device was returned to room temperature, the product particles were taken out, the taken-out product particles were washed with water, and then heated and dried in air. Thus, coOOH-coated nickel composite hydroxide particles, which were the positive electrode compound of comparative example 1, were obtained.
Method for producing positive electrode Compound of comparative examples 2 to 4
Nickel composite hydroxide particles as cores were obtained in the same manner as in the above examples. Then, electroless nickel plating was performed on nickel composite hydroxide particles having an average particle diameter of 10. Mu.m. As the electroless plating bath, a plating bath having the composition shown below was used.
Nickel sulfate 22.0g/L
Glycine is 33.3g/L
Sodium hypophosphite 23.3g/L
Sodium hydroxide of 12.3g/L
Surfactant 10mL/L
pH 9.5
A3L plating bath satisfying the above conditions was formed at a temperature of 60℃and 50g of nickel composite hydroxide particles were directly charged. That is, pretreatment steps such as the dip degreasing step, the surface conditioning step, and the etching step are not performed. After the nickel composite hydroxide particles were charged, stirring was performed by propeller at 500 rpm for 10 minutes, and 20mL of a solution containing palladium chloride and hydrochloric acid as main components (the concentration of the activator, palladium chloride was 2 g/L) was charged. At the same time as this charge, foaming is started instantaneously to start the reduction of palladium ions and nickel plating. During about 30 minutes until the end of foaming, propeller stirring was continued at 500 rpm, and stirring was stopped after the end of foaming. After filtration with a suction filter, water washing was repeated 3 times, and then drying was performed with hot air at a temperature of 80 ℃ for 1 hour. Thus, nickel composite hydroxide particles coated with the nickel-phosphorus composite plating film, which are positive electrode compounds of comparative examples 2 to 4, were obtained. The content of nickel element in the coating layer of the nickel composite hydroxide particles was adjusted to 100 parts by mass by adjusting the amount of the nickel sulfate solution to be charged.
Method for producing Compound for Positive electrode of comparative example 5
The positive electrode compound of comparative example 5 was produced in the same manner as in examples 1 and 2 above, except that the amount of the nickel sulfate solution added was adjusted so that the content of the nickel element in the coating layer was adjusted to 5.0 parts by mass relative to 100 parts by mass of the nickel composite hydroxide particles.
The nickel element content in the coating layer of the nickel composite hydroxide particles of examples 1 to 2 and comparative example 5 with respect to 100 parts by mass, the cobalt element content in the coating layer of the nickel composite hydroxide particles of comparative example 1 with respect to 100 parts by mass, and the nickel element content in the coating layer of the nickel composite hydroxide particles of comparative examples 2 to 4 with respect to 100 parts by mass are shown in table 1 below.
The evaluation items are as follows.
(1) Composition analysis
The composition analysis of the nickel composite hydroxide powders obtained in examples 1 to 2 and comparative examples 2 to 5 was performed by dissolving the obtained powders in hydrochloric acid or aqua regia and then analyzing the resultant powders by an inductively coupled plasma spectrometry device (manufactured by the company PerkinElmer Japan, 7300 DV).
(2) Volume resistivity
The volume resistivity was measured by a Loresta resistivity meter (MCP-T610, mitsubishi chemical corporation) and a Hiresta resistivity meter (MCP-HT 450, mitsubishi chemical corporation), and the volume resistivity at a load of 20kN was obtained. The measurement conditions are shown below.
Loresta resistivity meter
The measurement method comprises the following steps: automatic measuring range mode, 10V applied voltage, 20kN load and 1.5g Hiresta resistivity meter
The measurement method comprises the following steps: automatic measuring range mode, 10V applied voltage, 20kN load and 1.5g sample weight
(3) Utilization (initial)
For the nickel-metal hydride battery, after being charged at an ambient temperature of 25 ℃ for 6 hours at a charging rate of 0.2C, it was left at an ambient temperature of 25 ℃ for 0.5 hours, and then discharged at an ambient temperature of 25 ℃ to 1.0V at a discharging rate of 0.2C. This charge and discharge cycle was repeated 12 times to determine the discharge capacitance at the 12 th cycle. The utilization ratio was obtained by the following equation based on the obtained discharge capacitance at the 12 th cycle.
Utilization (%) =discharge capacitance at 12 th cycle (mAh)/theoretical capacitance (mAh) ×100
(4) Utilization (after 6 days at 90 ℃ C.)
For the nickel-metal hydride battery, after being charged at an ambient temperature of 25 ℃ for 6 hours at a charging rate of 0.2C, it was left at an ambient temperature of 25 ℃ for 0.5 hours, and then discharged at an ambient temperature of 25 ℃ to 1.0V at a discharging rate of 0.2C. Then, after the deep discharge test of 0.2C was performed, the nickel-hydrogen battery was naturally left at 90 ℃ for 6 days in a no-load connection state, thereby discharging the nickel-hydrogen battery. Then, after being charged at an ambient temperature of 25 ℃ for 6 hours at a charging rate of 0.2C, the battery was left at an ambient temperature of 25 ℃ for 0.5 hours and discharged at an ambient temperature of 25 ℃ to 1.0V at a discharging rate of 0.2C. This charge and discharge cycle was repeated 2 times to determine the discharge capacitance at the 2 nd cycle. The utilization ratio was obtained by the following equation based on the obtained discharge capacitance at the 2 nd cycle.
Utilization (%) = discharge capacitance at cycle 2 (mAh)/theoretical capacitance (mAh) x 100
(5) Average primary particle diameter of coating layer containing nickel element
The average primary particle diameter of the coating layer containing nickel element was determined by randomly selecting 10 independent primary particles from an image obtained by observing the coating layer with a field emission scanning electron microscope (FE-SEM), and measuring the maximum diameter of each of the selected primary particles, and the average value was set as the average primary particle diameter.
In examples 1 to 2 and comparative examples 2 to 5, it was confirmed that a coating layer containing nickel element was formed on the nickel composite hydroxide particles serving as nuclei as follows: the nickel composite hydroxide particles as nuclei and the nickel-containing coated nickel composite hydroxide particles as final products were subjected to composition analysis at substantially equal intervals from the center to the surface portion thereof by energy dispersive X-ray analysis (EDX), respectively. That is, as shown in table 2 below, the nickel content in the core did not change significantly in the core center portion and the core surface portion, whereas in the nickel-containing coated nickel composite hydroxide particles, the nickel content changed significantly in the particle center portion and the particle surface portion, and the nickel content in the particle surface portion was significantly greater than the nickel content in the particle center portion (nickel content indicated by underlines in table 2). From this, it can be confirmed that: the nickel composite hydroxide particles serving as cores are formed with a coating layer containing nickel element.
The evaluation results are shown in table 1 below.
TABLE 1
TABLE 2
In examples 1 and 2 and comparative examples 2 and 5, since the cobalt element was not added at the time of forming the coating layer, it was determined that the cobalt content of the coating layer in examples 1 and 2 and comparative examples 2 and 5 was not (0 ppm).
As shown in table 1 above, in examples 1 to 2, the nickel composite hydroxide particles had a coating layer containing nickel element in which cobalt element was 0ppm and phosphorus element was 2ppm or less on the surface, and the content of nickel element in the coating layer was 7.0 parts by mass or more and 10 parts by mass or less, and the volume resistivity was 0.0154 Ω·cm or less, and the initial characteristic utilization was 87.9% or more and the utilization at day 6 at 90 ℃ was 81.4% or more, relative to 100 parts by mass of the nickel composite hydroxide particles. Therefore, in examples 1 and 2, a positive electrode compound having not only excellent utilization efficiency in initial characteristics but also excellent utilization efficiency after leaving at high temperature and high conductivity was obtained. In particular, in example 1 in which the content of nickel element in the coating layer was 10 parts by mass relative to 100 parts by mass of the nickel composite hydroxide particles, the use efficiency and the conductivity after being left at high temperature were further improved.
In addition, according to examples 1 to 2, it can be confirmed that: as the volume resistivity of the positive electrode compound decreases, the utilization rate in the initial characteristics and the utilization rate after being left at high temperature tend to increase. In examples 1 and 2, the average primary particle diameter of the nickel element-containing coating layer was reduced to 81nm to 83nm as compared with comparative examples 2 and 4.
On the other hand, in comparative example 1, which is a nickel composite hydroxide particle coated with CoOOH, the volume resistivity was 15.3 Ω·cm, and the utilization rate at the 6 th day of the standing at 90 ℃ was stopped at 77.1%. Therefore, in comparative example 1, conductivity and good utilization after leaving at high temperature could not be obtained.
In comparative examples 2 to 4, in which the coating layer containing nickel contained 1570ppm to 2327ppm of phosphorus, the volume resistivity was 6.2Ω·cm to 21.1Ω·cm, but the initial characteristic utilization was 71.7% to 76.4%, and the utilization after leaving at high temperature was 66.6% to 71.0%, respectively, and the utilization was greatly reduced. In comparative example 5 in which the nickel element content in the coating layer of the nickel composite hydroxide particles was 5.0 parts by mass relative to 100 parts by mass, the volume resistivity was increased, and conductivity could not be obtained.
Next, the method for producing the positive electrode compound of examples 3 and 4 and comparative examples 6 and 7 will be described.
Method for producing Compound for Positive electrode of comparative example 7
After water was injected into a reaction tank equipped with a stirrer and an overflow pipe, an aqueous sodium hydroxide solution was added. So that the atomic ratio of nickel atoms, cobalt atoms and manganese atoms reaches 0.50:0.20: the nickel sulfate aqueous solution, the cobalt sulfate aqueous solution, and the manganese sulfate aqueous solution were mixed in a manner of 0.30, thereby preparing a mixed raw material liquid. Next, the mixed raw material solution and an aqueous ammonium sulfate solution as a complexing agent were continuously added to the reaction tank while stirring, and an aqueous sodium hydroxide solution was timely added dropwise so that the pH of the solution in the reaction tank became 11.3 at a liquid temperature of 40 ℃. The obtained nickel composite hydroxide particles were filtered, then washed with water, and dried at a temperature of 105 ℃, thereby obtaining a dried powder of the nickel composite hydroxide of comparative example 7.
Method for producing Compound for Positive electrode of example 3
The nickel composite hydroxide particles of comparative example 7 prepared as described above were further directly subjected to electroless pure nickel plating treatment, thereby producing a nickel composite hydroxide having a nickel plating film as a coating layer (nickel cobalt manganese composite hydroxide having a nickel plating film as a coating layer), i.e., a nickel-coated nickel composite hydroxide of example 3. In more detail, a nickel composite hydroxide having a nickel plating film was produced as follows.
First, nickel composite hydroxide particles having a particle diameter of 10 μm were used as base particles, and the base particles were stirred with a cationic surfactant for 10 minutes in order to modify the surfaces of the base particles. Then, after the filtration and water washing, the palladium ion catalyst solution was stirred for 10 minutes, whereby palladium ions were adsorbed on the surfaces of the substrate particles. Then, after the filtration and water washing, the palladium catalyst was carried on the surface of the base material particles by stirring the mixture in a reducing solution for 10 minutes. Then, after the filtration and water washing, the substrate particles having the palladium catalyst supported on the surface were pre-stirred in a nickel sulfate solution heated to 80 ℃ for 1 minute. The composition of the nickel sulfate solution was as follows: the nickel salt is 0.30mol/L, the citrate is 1mol/L, and the carbonate is 1.7mol/L. Then, hydrazine monohydrate was put into the nickel sulfate solution in an amount of 0.4 mol/L. After the reaction starts, the substrate particles having the palladium catalyst supported on the surface thereof are stirred for 5 minutes or more in a nickel sulfate solution containing hydrazine monohydrate, whereby a nickel plating film is gradually formed on the surfaces of the nickel composite hydroxide particles and a coating layer containing nickel element is formed. After stirring, the nickel composite hydroxide particles having the coating layer containing nickel element formed thereon were washed with water by filtration and dried at a temperature of 80 ℃. Thus, nickel-containing coated nickel composite hydroxide particles as a positive electrode compound according to the present invention were obtained. The content of nickel element (10 parts by mass) in the coating layer of the nickel composite hydroxide particles was adjusted to 100 parts by mass by adjusting the amount of the nickel sulfate solution to be charged.
Method for producing Compound for Positive electrode of example 4
The dried powder of nickel-containing coated nickel composite hydroxide of example 3 and lithium carbonate powder obtained in the above manner were weighed and mixed so that Li/(ni+co+mn) =1.03, and then, primary firing was performed under atmospheric conditions at a temperature of 740 ℃ for 8.4 hours, thereby obtaining a lithium-nickel-containing coated nickel composite oxide as primary fired powder. Then, the primary calcined powder was pulverized and subjected to secondary calcination at 940℃for 8.4 hours under atmospheric conditions. As a secondary firing powder, a lithium-nickel-containing coated nickel composite oxide of example 4 was obtained.
Method for producing Compound for Positive electrode of comparative example 6
The dry powder of the nickel composite hydroxide of comparative example 7 and lithium carbonate powder were weighed and mixed so that Li/(ni+co+mn) =1.03, and then, primary firing was performed at a temperature of 740 ℃ for 8.4 hours under atmospheric conditions, to obtain a lithium-nickel composite oxide as primary fired powder. Then, the primary calcined powder was pulverized, and secondary calcination was performed at a temperature of 940 ℃ for 8.4 hours under an atmospheric environment, to obtain a secondary calcined powder, which was the lithium-nickel composite oxide of comparative example 6.
The evaluation items are as follows.
(1) Composition analysis
The composition analysis of the positive electrode compound powders obtained in example 4 and comparative example 6 was performed by dissolving the obtained powders in hydrochloric acid or aqua regia and then analyzing the powders by an inductively coupled plasma spectrometry device (manufactured by the company PerkinElmer Japan, 7300 DV).
(2) Volume resistivity
The volume resistivity was measured by a Loresta resistivity meter (Mitsubishi chemical system, MCP-T610) and a Hiresta resistivity meter (Mitsubishi chemical system, MCP-HT 450), and the volume resistivity at a load of 20kN was obtained. The measurement conditions are shown below.
Loresta resistivity meter
The measurement method comprises the following steps: automatic measuring range mode, 10V applied voltage, 20kN load and 1.5g Hiresta resistivity meter
The measurement method comprises the following steps: automatic measuring range mode, 10V applied voltage, 20kN load and 1.5g sample weight
(3) Initial capacitance
A stacked cell type battery was fabricated using the compound powders for positive electrode of example 4 and comparative example 6, and both of them were charged and discharged at an ambient temperature of 25 ℃. Charged to 4.2V at CV conditions at 0.05C and then discharged to 2.7V at 0.1C. Charging to 4.2V at 0.1C at CV conditions, then discharging to 2.7V at 0.2C, and performing 3 cycles at this condition. Charging to 4.2V at CV conditions at 0.2C, then discharging to 2.7V at 0.2C, and performing 5 cycles at this condition. Charging to 4.2V at CV conditions at 0.2C, then discharging to 3.0V at 0.2C, and performing 3 cycles at this condition. The final discharge capacitance at this time is set to the initial capacitance.
(4) DCIR measurement at 25 ℃
DCIR measurement of a battery having an SOC of 50% was performed at an ambient temperature of 25 ℃ using a laminated unit cell prepared from the compound powders for positive electrode of example 4 and comparative example 6.
(5) Load characteristics
The stacked cell type batteries prepared from the positive electrode compound powders of example 4 and comparative example 6 were charged to 4.2V at an ambient temperature of 25 ℃ under a condition of 0.2C and a CV condition, and then discharged to 3.0V under a condition of 0.2C. In addition, the charge was carried out to 4.2V at a temperature of 25℃under a condition of 0.2C under CV conditions, and then discharged to 3.0V under a condition of 10C. The ratio of the capacity discharged at 10C to the capacity discharged at 0.2C was set as the capacity retention rate in the load characteristic. As shown in the following formula.
Capacitance retention (%) =10c discharge capacitance (mAh/g)/0.2C discharge capacitance (mAh/g) ×100
(6) Average primary particle diameter of coating layer containing nickel element
Regarding the average primary particle diameter of the nickel element-containing coating layer of the positive electrode compound powder of example 3, 10 independent primary particles were randomly selected from an image obtained by observing the coating layer by a field emission scanning electron microscope (FE-SEM), and the maximum diameter of each of the selected primary particles was measured, and the average value was set as the average primary particle diameter.
The evaluation results are shown in table 3 below.
TABLE 3
As a result of carrying out composition analysis of the lithium-nickel-containing coated nickel cobalt manganese composite oxide powder of example 4, li: ni: co: the molar ratio of Mn is 1.011:0.575:0.170:0.255. as a result of carrying out composition analysis of the lithium-nickel cobalt manganese composite oxide powder of comparative example 6, li: ni: co: mn in a molar ratio of 1.022:0.499:0.200:0.301.
as shown in Table 3, the volume resistivity was 1.559X 10 as compared with comparative example 7 8 The volume resistivity of the nickel-containing coated nickel composite hydroxide of example 3 was 4.713 ×10 as compared with the Ω·cm nickel composite hydroxide 7 Omega cm, thereby improving the conductivity. In addition, the volume resistivity was 5.605×10 as compared with comparative example 6 2 The volume resistivity of the lithium-nickel-containing coated nickel composite oxide of example 4 was 1.679 ×10 as compared with the omega cm lithium-nickel composite oxide 2 Omega cm, thereby improving the conductivity.
As shown in Table 3, the initial capacitance of the lithium-nickel-containing coated nickel composite oxide of example 4, which has a lower volume resistivity, was 157.4mAh/g, and thus had a higher capacitance, than that of the lithium-nickel composite oxide of comparative example 6, which had an initial capacitance of 153.9 mAh/g.
As shown in table 3, DCIR1.73 Ω at 25 ℃ of the 50% SOC of example 4, which has a lower volume resistivity, has a lower resistance than the lithium-nickel composite oxide of comparative example 6, which has DCIR 1.98 Ω at 25 ℃ of the 50% SOC.
As shown in table 3, the lithium-nickel-containing composite oxide of example 4 having a low volume resistivity has a capacitance retention of 65.6% calculated as a ratio of the capacitance discharged at 10C to the capacitance discharged at 0.2C, and has a higher load characteristic than the lithium-nickel composite oxide of comparative example 6 having a capacitance retention of 65.1% calculated as a ratio of the capacitance discharged at 10C to the capacitance discharged at 0.2C.
The average primary particle diameter of the nickel element-containing coating layer of example 3 was reduced to 50nm to 90nm.
Industrial applicability
The positive electrode compound of the present invention has the above-described coating layer structure, and therefore, is excellent in initial characteristics and in use efficiency after being left at a high temperature, and has high conductivity, and therefore, can be used in a wide range of battery fields, for example, as a positive electrode active material of an alkaline storage battery, a positive electrode active material of a nonaqueous electrolyte secondary battery, and a precursor of a positive electrode active material of a nonaqueous electrolyte secondary battery, and has high use value.

Claims (9)

1. A positive electrode compound which is a secondary particle obtained by agglomerating primary particles, and which has a core and a coating layer on the surface of the core, wherein the core contains a nickel composite hydroxide, and the coating layer contains 500ppm or less of cobalt element, 10ppm or less of phosphorus element, and nickel element,
The content of nickel element in the coating layer is as follows: 6 parts by mass or more and 20 parts by mass or less with respect to 100 parts by mass of the core,
the nickel-containing coating layer has an average primary particle diameter of 10nm to 90nm,
the nickel content in the nickel-containing coating layer is 99 mass% or more,
the volume resistivity of the positive electrode compound is 1.5X10 Ω & cm or less, and the positive electrode compound is used as a positive electrode active material of an alkaline storage battery.
2. A positive electrode compound which is a secondary particle obtained by agglomerating primary particles, and which has a core and a coating layer on the surface of the core, wherein the core contains a nickel composite hydroxide, and the coating layer contains 500ppm or less of cobalt element, 10ppm or less of phosphorus element, and nickel element,
the content of nickel element in the coating layer is as follows: 6 parts by mass or more and 20 parts by mass or less with respect to 100 parts by mass of the core,
the nickel-containing coating layer has an average primary particle diameter of 10nm to 90nm,
the nickel content in the nickel-containing coating layer is 99 mass% or more,
the positive electrode compound has a volume resistivity of 5.0X10 2 And omega cm or less, wherein the positive electrode compound is used as a positive electrode active material for a nonaqueous electrolyte secondary battery.
3. A positive electrode compound which is a secondary particle obtained by agglomerating primary particles, and which has a core and a coating layer on the surface of the core, wherein the core contains a nickel composite hydroxide, and the coating layer contains 500ppm or less of cobalt element, 10ppm or less of phosphorus element, and nickel element,
the content of nickel element in the coating layer is as follows: 6 parts by mass or more and 20 parts by mass or less with respect to 100 parts by mass of the core,
the nickel-containing coating layer has an average primary particle diameter of 10nm to 90nm,
the nickel content in the nickel-containing coating layer is 99 mass% or more,
the positive electrode compound has a volume resistivity of 1.5X10 8 Omega cm or less, and is used as a precursor of a positive electrode active material for a nonaqueous electrolyte secondary battery.
4. The positive electrode compound according to any one of claim 1 to 3, wherein,
the core contains at least 1 metal element selected from cobalt, zinc, manganese, lithium, magnesium, aluminum, zirconium, yttrium, ytterbium and tungsten.
5. The positive electrode compound according to any one of claim 1 to 3, wherein,
and further comprises a palladium compound.
6. The positive electrode compound according to claim 1, wherein,
The core is represented by the following general formula (1),
Ni (1-x) M x (OH) 2+a (1)
in the above formula, x is more than 0 and less than or equal to 0.2, a is more than or equal to 0 and less than or equal to 0.2, and M represents at least 1 metal element selected from cobalt, zinc, manganese, magnesium, aluminum, yttrium and ytterbium.
7. The positive electrode compound according to claim 3, wherein,
the core is represented by the following general formula (3),
Ni (1-z) P z (OH) 2+c (3)
in the above formula, z is more than 0 and less than or equal to 0.7,0 and less than or equal to c is more than or equal to 0.28, and P represents at least 1 metal element selected from cobalt, zinc, manganese, magnesium, aluminum, zirconium, yttrium, ytterbium and tungsten.
8. A positive electrode active material for a nonaqueous electrolyte secondary battery, wherein,
the positive electrode compound according to claim 7 is used as a precursor.
9. The positive electrode compound according to claim 2, wherein,
the core is represented by the following general formula (2),
Li[Li y (Ni (1-b) N b ) 1-y ]O 2 (2)
in the formula, b is more than or equal to 0 and less than or equal to 0.7,0, y is more than or equal to 0.50, and N represents at least 1 metal element selected from cobalt, manganese, magnesium, aluminum, zirconium, yttrium, ytterbium and tungsten.
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