WO2015104824A1 - Lithium ion secondary battery positive electrode and lithium ion secondary battery - Google Patents

Lithium ion secondary battery positive electrode and lithium ion secondary battery Download PDF

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WO2015104824A1
WO2015104824A1 PCT/JP2014/050268 JP2014050268W WO2015104824A1 WO 2015104824 A1 WO2015104824 A1 WO 2015104824A1 JP 2014050268 W JP2014050268 W JP 2014050268W WO 2015104824 A1 WO2015104824 A1 WO 2015104824A1
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positive electrode
metal plate
secondary battery
active material
electrode active
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PCT/JP2014/050268
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French (fr)
Japanese (ja)
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岩崎　富生
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株式会社日立製作所
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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
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/131—Electrodes based on mixed oxides or hydroxides, or on mixtures of oxides or hydroxides, e.g. LiCoOx
    • 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
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/139—Processes of manufacture
    • H01M4/1391—Processes of manufacture of electrodes based on mixed oxides or hydroxides, or on mixtures of oxides or hydroxides, e.g. LiCoOx
    • 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
    • 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
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/64—Carriers or collectors
    • H01M4/66—Selection of materials
    • 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

Definitions

  • the present invention relates to a positive electrode for a lithium ion secondary battery and a lithium ion secondary battery.
  • a lithium transition metal oxide capable of inserting and extracting lithium ions As a positive electrode active material for a lithium ion secondary battery, a lithium transition metal oxide capable of inserting and extracting lithium ions is known. Typical examples include lithium oxide (LiMO 2 ) having a layered rock salt structure, olivine-type lithium phosphate compound (LiMPO 4 ), and spinel-type oxide (LiM 2 O 4 ), which achieve high output and high energy density. Has been studied for.
  • Patent Document 1 As a technique for improving the performance of a lithium ion secondary battery, it is oriented in a crystal orientation such that lithium ions easily enter and exit a positive electrode active material made of LiCoO 2.
  • a method of using (110) -oriented gold or platinum as a base metal plate for the purpose is disclosed.
  • a layered solid solution compound represented by Li 1.2 M 0.8 O 2 has attracted attention as a material that can insert and desorb more lithium than a positive electrode active material made of LiMO 2.
  • a positive electrode active material made of LiMO 2. has been. It can contain 20% more lithium, and is a material suitable for increasing the capacity (Japanese Patent Laid-Open No. 2012-129102 (Patent Document 2), etc.).
  • This invention is providing the positive electrode for lithium ion secondary batteries which can achieve a high capacity
  • the positive electrode active material is epitaxially grown on the metal plate, and the theoretical value of the closest interatomic distance of the metal plate is 87 to 89% of the theoretical value of the closest interatomic distance of the positive electrode active material. It is characterized by being.
  • Another positive electrode of the present invention includes a positive electrode active material and a metal plate for fixing the positive electrode active material.
  • the at least surface portion is made of a metal material made of nickel or a cobalt nickel alloy, and the positive electrode active material is epitaxially grown on the metal plate.
  • a lithium ion secondary battery of the present invention that solves the above-described problems comprises the above positive electrode and a negative electrode that occludes and releases lithium.
  • a positive electrode for a lithium ion secondary battery and a lithium ion secondary battery that can achieve high capacity and high output can be provided.
  • FIG. 3 is a view showing a ( ⁇ 100) crystal plane of a (110) oriented nickel metal plate.
  • 1 is a view showing a (1-100) crystal plane of a layered solid solution compound (Li 1.2 MnxNiyCozO 2 ).
  • FIG. It is the figure which showed the (1 1 -20) crystal plane of the layered solid solution compound (Li 1.2 MnxNiyCozO 2 ).
  • High-power and high-energy density lithium-ion secondary batteries have recently attracted attention as power sources for consumer devices such as mobile phones.
  • a lithium ion secondary battery is also desired to be applied to a driving power source for ships, railways, automobiles and the like that can efficiently use energy.
  • technologies for storing electric power generated using natural energy such as wind power and sunlight in lithium ion secondary batteries and storing electric power from the grid are attracting attention for both home and industrial use. Yes.
  • a technology using a lithium ion secondary battery is also attracting attention in a smart grid (next-generation power transmission network) using IT (Information Technology) technology.
  • a lithium ion secondary battery has a configuration in which a positive electrode and a negative electrode capable of occluding and releasing lithium ions are arranged via a separator and sealed in a battery container filled with a non-aqueous electrolyte containing a lithium salt. And charge and discharge reversibly.
  • the positive electrode uses a metal foil such as an aluminum foil as a current collector (electrode plate), and a positive electrode active material made of powder is fixed to the current collector by a binder (binder).
  • a positive electrode active material conventionally, lithium cobaltate (LiCoO 2 ) having a layered rock salt structure, or an oxide of lithium and transition metal in which a part or all of cobalt atoms of lithium cobaltate is substituted by nickel, manganese, or the like
  • the powder etc. which consist of are used.
  • the layered solid solution compound is represented by the general formula ⁇ Li 2 MnO 3 — (1- ⁇ ) LiMO 2 (M includes transition metals such as Ni and Co), and is expected to have a high capacity exceeding 250 mAh / g. It is a material.
  • the basic composition may be expressed in the form of Li 1.2 MO 2 , Li 1.2 M 0.8 O 2 or the like. Although it has a crystal structure that is very similar to LiCoO 2 that is a conventional positive electrode active material, it has a larger theoretical capacity and is expected to contribute to an increase in battery capacity.
  • LixNiaMnbMcO2 + y (a + b + c 0.8, 0.95 or more and x or more and 1.2).
  • M is a metal other than Ni and Mn, a transition metal, and other additive elements, and includes Fe, Co, W, Nb, Mg, Al, and the like. Oxygen is affected by the ratio of lithium and metal and the elements contained, and increases or decreases as appropriate.
  • the inventors of the present application have determined that the crystal phase of the positive electrode active material is formed by epitaxial growth so that lithium can easily move from the lithium layer in the positive electrode active material (layered solid solution compound) to the transition metal layer.
  • the material for the metal plate was selected, and the layered solid solution compound was epitaxially grown on the crystal plane of the metal plate. At that time, it was effective to set the theoretical value of the nearest interatomic distance of the underlying metal plate within a specific range with respect to the theoretical value of the nearest interatomic distance of the active material.
  • the layered solid solution compound has a crystal structure that is very similar to LiCoO 2 that is a conventional positive electrode active material. Therefore, as in Japanese Patent Application Laid-Open No. 2009-295514, a method of using (110) -oriented gold or platinum as a metal plate as a base was also examined. However, when the layered solid solution compound is used as the positive electrode active material, the lithium ion storage / release performance was not improved. Therefore, it is not effective to use gold or platinum as the metal plate. The analysis will be described later.
  • a feature of the present invention that solves the above problems is a lithium ion secondary battery including a positive electrode and a negative electrode capable of occluding and releasing lithium ions
  • the positive electrode includes a positive electrode active material, and a metal plate that fixes the positive electrode active material
  • the surface portion to which the positive electrode active material is fixed has a (110) oriented portion having a face-centered cubic structure, and the positive electrode active material is epitaxially grown on the metal plate,
  • the theoretical value of the distance is 87 to 89% of the theoretical value of the closest interatomic distance of the positive electrode active material.
  • the atomic density close-packed crystal plane of the positive electrode active material is perpendicular to the metal plate, and the interatomic distance of the positive electrode active material is extended in the direction perpendicular to the metal plate, so that the lithium layer and the transition metal layer Therefore, it is possible to provide a lithium ion secondary battery with high performance and reliability.
  • the positive electrode active material is preferably formed by epitaxial growth on the surface of a metal plate.
  • Each element of the positive electrode active material grows on the metal element on the surface of the metal plate.
  • the nearest oxygen atom distance of the positive electrode active material is 0.281 nm or more and 0.288 nm or less, and the theoretical value of the nearest atom distance of the metal plate is 0.244 nm or more and 0.253 nm or less.
  • at least the surface of the metal plate is made of nickel or cobalt nickel alloy.
  • the metal plate may be provided with a (110) -oriented portion having a face-centered cubic structure only on the surface.
  • a nickel layer or a cobalt nickel alloy, or a base material having conductivity other than that, and a nickel layer or a cobalt nickel alloy layer provided on the base material may be provided.
  • the (110) -oriented portion having a face-centered cubic structure may be present on the outermost surface, and the internal orientation can be selected as appropriate, or the orientation may not exist.
  • the theoretical value of the nearest interatomic distance of the metal plate is preferably 87 to 88% of the theoretical value of the nearest interatomic distance of the positive electrode active material.
  • the above configuration can provide a positive electrode that is suitable for a large-capacity lithium ion secondary battery and has a high output.
  • FIG. 1 is a schematic cross-sectional view of a positive electrode according to the first embodiment.
  • a positive electrode 1 capable of occluding and releasing lithium ions applied to a lithium ion secondary battery includes a metal plate 2 and a positive electrode active material layer 3 capable of occluding and releasing lithium ions.
  • lithium is present in the transition metal layer where the transition metals Mn, Ni, and Co are present at 80%. It can be regarded as a structure with 20% penetration. Therefore, when lithium is inserted starting from a charged state in which lithium is removed, if lithium can be inserted until it reaches a state of Li (Li 0.2 M 0.8 ) O 2 , it will be more than the conventional material LiCoO 2. Lithium can be inserted in an amount of 20 at.%, And the capacity can be increased.
  • FIG. 2 shows the crystal structure (FIG. 2A) of the conventional positive electrode active material (LiCoO 2 ) and the crystal structure of the layered solid solution compound (Li 1.2 MnxNiyCozO 2 ) as seen from the [1 1 -2 0] direction. 2 (B)).
  • the size of each atom lithium ( ⁇ layer, ⁇ ′ layer) is the largest, next is oxygen ( ⁇ layer, ⁇ ′ layer), and the smallest is transition metal ( ⁇ layer, ⁇ ′ layer). It has a layered structure.
  • the layered solid solution compound is in a state where an excessive amount of lithium element 4 expressed in black has entered the transition metal layer ( ⁇ layer).
  • FIG. 3 is a diagram showing a state of a layered solid solution compound that is charged and lithium is empty.
  • the lithium layer 5 is emptied when lithium is removed by charging. Further, the lithium element 4 contained in the transition metal layer is also released.
  • lithium ions are occluded in the positive electrode active material layer.
  • Lithium enters the lithium layer in the first stage (first stage). After the lithium layer is filled, it moves laterally and enters the transition metal layer (second stage). That is, the lithium is filled into the transition metal layer so as to move from the lithium layer into which lithium has entered, but the diffusion rate for moving lithium from the lithium layer to the transition metal layer is very slow. It is difficult to achieve a state in which 20% of lithium enters a transition metal layer in which 80 at.% Of transition metals (Mn, Ni, Co) are present under the conditions of actual use as a battery.
  • Mn, Ni, Co transition metals
  • FIG. 4 is a diagram for explaining the movement of lithium during discharge of a layered solid solution compound (Li 1.2 MnxNiyCozO 2 ).
  • a layered solid solution compound Li 1.2 MnxNiyCozO 2
  • the interatomic distance around the vacancies is narrow, and the oxygen atoms 6 and 7 become obstacles when the lithium atoms move. Therefore, lithium does not easily move from the lithium layer to the transition metal layer, and it is difficult to fill the transition metal layer with lithium.
  • the inventors In order to widen the gap between the oxygen atoms 6 and 7, which are obstructive, the inventors have increased the interatomic distance in the direction perpendicular to the base metal plate to facilitate the movement from the lithium layer to the transition metal layer. Tried.
  • FIG. 5 shows a cross-sectional view of the crystal structure of an example of the positive electrode in which the layer 3 of the layered solid solution compound Li 1.2 MnxNiyCozO 2 is formed on the nickel metal plate 2 having the (110) orientation according to the present embodiment.
  • the layered solid solution compound is viewed from the [1 1 -2 0] direction, the layered solid solution compound layer is stretched by tensile strain in the direction perpendicular to the metal plate (arrow direction) under the influence of the nickel metal plate. Since the interatomic distance in the vertical direction in the figure is increased, the movement from the lithium layer to the transition metal layer is likely to occur.
  • a nickel metal plate of (110) orientation serving as a base and a positive electrode active material layer made of a layered solid solution compound are provided. Due to the influence of the metal plate, tensile strain of the positive electrode active material layer is generated in the direction perpendicular to the metal plate (up and down direction in the figure), and the interatomic distance is extended in the direction perpendicular to the metal plate. That is, by increasing the interatomic distance in the direction perpendicular to the metal plate, the path for lithium movement can be expanded.
  • FIG. 6A shows a (110) crystal plane (viewed from a direction perpendicular to the nickel metal plate) of a (110) -oriented nickel metal plate viewed from the [110] direction
  • FIG. 7 shows the (1 ⁇ 1 0 0) crystal plane (FIG. 7A) when the layered solid solution compound Li 1.2 MnxNiyCozO 2 is expressed by the space group R-3m (hexagonal crystal), and (1 1 ⁇ 2 0 FIG.
  • the layered solid solution compound Li 1.2 MnxNiyCozO 2 can be expressed by the space group C2 / m, but the overall structure excluding exceptional lattice points corresponding to a peak around 22 ° obtained by X-ray diffraction is It can be expressed by the space group R-3m (hexagonal crystal).
  • the (1 ⁇ 100) crystal plane of the layered solid solution compound Li 1.2 MnxNiyCozO 2 in FIG. 7A has a short side (distance between nearest oxygen atoms) of 0.281 nm or more. It is a crystal plane having a unit cell of a rectangle having a length of 288 nm or less and a long side of 0.368 nm or more and 0.398 nm or less.
  • the (110) plane of the nickel metal plate in FIG. 6 (A) is a crystal plane with a rectangular unit having a short side of 0.249 nm and a long side of 0.352 nm as a unit cell.
  • the (1 -1 0 0) crystal plane of the layered solid solution compound Li 1.2 MnxNiyCozO 2 and the (110) plane of nickel have a similar structure, and the (1 -1 0 0) crystal of the layered solid solution compound Li 1.2 MnxNiyCozO 2
  • the (110) face of nickel than the face is made up of unit cells about 12% smaller.
  • the layered solid solution compound Li 1.2 MnxNiyCozO 2 when a layered solid solution compound Li 1.2 MnxNiyCozO 2 is formed on a nickel metal plate having a (110) orientation, the layered solid solution compound Li 1.2 MnxNiyCozO 2 has a (1 ⁇ 1 0 0) orientation.
  • the layered solid solution compound Li 1.2 MnxNiyCozO 2 is contracted in a direction parallel to the nickel metal plate (compressed strain state) by epitaxial growth (single crystal growth with the same structure as the base) and nickel with a small unit cell. . Under the influence, a layered solid solution compound Li 1.2 MnxNiyCozO 2 is formed in a state (tensile strain state) stretched by a Poisson's ratio in a direction perpendicular to the nickel metal plate.
  • Epitaxial growth is observed by a conventionally known thin film growth method by selecting a base material.
  • Epitaxial growth is a crystal growth method in which a Li 1.2 MnxNiyCozO 2 + y target is used and atoms are released from the target by, for example, sputtering or electron beam evaporation, and deposited on a substrate.
  • the direction parallel to the metal plate should be smaller than the value of the distance between nearest oxygen atoms of the metal constituting the metal plate than the value of the layered solid solution compound Li 1.2 MnxNiyCozO 2 (from 0.281 nm to 0.288 nm). It was analyzed using molecular dynamics simulations whether the effect of shrinking to a width (that is, the effect of stretching in a direction perpendicular to the metal plate) was obtained. The relative difference between the distance between the nearest atoms in the metal plate and the distance between the nearest oxygen atoms in the positive electrode active material is calculated from the theoretical distance between the nearest atoms in the layered solid solution compound.
  • the value is subtracted and divided by the theoretical value of the closest interatomic distance of the layered solid solution compound and then multiplied by 100 and expressed as a percentage.
  • the relative difference is negative, that is, when the theoretical value of the distance between nearest atoms of the metal plate is large, there is no effect of shrinking in the direction parallel to the metal plate (ie, the effect of stretching in the direction perpendicular to the metal plate). Only positive cases were considered.
  • x 0.40
  • y 0.24
  • z 0.16.
  • the diffusion rate (m 2 / s) of lithium with 50% Li deficiency (during discharge) was calculated.
  • the diffusion rate indicates the rate at which Li atoms contained in the Li layer move to the transition metal layer.
  • molecular dynamics simulation for example, as described in page 150 of Bio Physical Journal, Vol. 75. It was obtained using Einstein's relationship indicating the relationship between the mean square displacement of atoms and the diffusion coefficient.
  • the distance between the nearest atoms of the metal plate is smaller than the distance between the nearest oxygen atoms of the positive electrode active material, and the distance between the nearest atoms of the metal plate is
  • the relative difference in the distance between the nearest oxygen atoms of the positive electrode active material is 11% or more and 13% or less (the theoretical value of the nearest atomic distance of the metal plate is the theoretical value of the nearest interatomic distance of the positive electrode active material) In the case of 87 to 89%), the diffusion rate of lithium is remarkably increased, and the effect of expanding the movement path by the effect of contracting in the direction parallel to the metal plate (that is, the effect of extending in the direction perpendicular to the metal plate) is obtained.
  • nickel As a metal plate material capable of obtaining such an effect, there are nickel corresponding to a relative difference of 11% to 13% and a cobalt nickel alloy.
  • a cobalt simple substance since it is not a face-centered cubic structure but a close-packed hexagonal structure, the effect of giving strain cannot be obtained.
  • the cobalt nickel alloy has a face-centered cubic structure, so that the effect of this embodiment can be obtained.
  • a (110) -oriented cobalt nickel alloy is effective.
  • Gold also has a face-centered cubic structure similar to that of nickel, but its (110) plane has a rectangular unit with a short side (distance between nearest oxygen atoms) of 0.288 nm and a long side of 0.408 nm as a unit cell. It is a crystal plane, and the closest distance between oxygen atoms (0.288 nm) is equal to or larger than the value of the layered solid solution compound Li 1.2 MnxNiyCozO 2 (from 0.281 nm to 0.288 nm). Therefore, there is no effect of causing compressive strain in a direction parallel to the metal plate.
  • Platinum also has a face-centered cubic structure similar to that of nickel, but its (110) plane has a rectangular unit with a short side (distance between nearest oxygen atoms) of 0.277 nm and a long side of 0.392 nm.
  • the distance between the nearest oxygen atoms (0.277 nm) is smaller than the value of the layered solid solution compound Li 1.2 MnxNiyCozO 2 (0.281 nm or more and 0.288 nm or less).
  • platinum, palladium, iridium, etc. are not effective because the closest relative distance difference is about 3%.
  • lithium of the positive electrode active material can be easily transferred and lithium can be easily transferred from the lithium layer to the transition metal layer.
  • lithium can enter a high concentration (in Li 1.2 MnxNiyCozO 2 , it can enter up to 0.6 times the amount of oxygen), resulting in a high-capacity lithium ion secondary battery.
  • the positive electrode structure of the first embodiment when lithium comes out to the electrolyte side or enters from the electrolyte side, it is possible to bring out a crystal face that is easy to go in and out, and the structure of the positive electrode with many effective crystal faces Can lead to improved output. Further, in the positive electrode structure of the first embodiment, it is not necessary to use a binder resin, and there is a possibility of extending the life by improving the electrode density and avoiding deterioration.
  • FIG. 9 is a diagram showing a second embodiment, and shows a positive electrode structure having a crystal defect repair layer between a layered solid solution compound layer and a substrate.
  • the metal plate 2 includes a substrate 8 and a crystal defect repair layer 9 formed on the surface of the substrate 8, and the layer of the positive electrode active material 3 is provided on the crystal defect repair layer 2.
  • the crystal defect repair layer is a metal film, and as in the first embodiment, the surface has a (110) orientation having a face-centered cubic structure, and the distance between nearest atoms of the metal material constituting the crystal defect repair layer is The theoretical value is 87 to 89% of the theoretical value of the closest interatomic distance of the positive electrode active material.
  • the substrate may be any material as long as it can form a crystal defect repair layer on the surface, and is preferably a conductive material.
  • a nickel film as a crystal defect repair layer by sputtering or the like on an aluminum plate conventionally used as a current collector, and to epitaxially grow a positive electrode active material thereon.
  • the base material 8 made of an aluminum plate or the like has a thickness of, for example, 0.1 mm to 5 mm
  • the positive electrode active material layer 3 has a thickness of, for example, 1 nm to 5 ⁇ m
  • the crystal defect repair layer 9 has, for example, It is preferable to use one having a thickness of 1 nm to 0.1 ⁇ m.
  • FIG. 10 is a partial cross-sectional view showing a configuration example of a lithium ion secondary battery to which the positive electrode 1 of the first and second embodiments is applied.
  • a lithium ion secondary battery 100 (hereinafter, simply referred to as “battery 100”) includes a sheet-like positive electrode 1 interposed between a negative electrode 10, a positive electrode 1, and a negative electrode 10 and a separator 11 that prevents a short circuit.
  • a wound body wound around a core material (not shown) is provided, and the battery can 12 is sealed together with a non-aqueous electrolyte solution (not shown) containing a lithium salt.
  • the battery 100 has a cylindrical shape, but may be a square shape, a laminate type, or the like, or a stacked electrode group in which positive and negative electrodes and a separator are stacked may be used.
  • the positive electrode 1 has the configuration of the first and second embodiments.
  • the negative electrode 10 a material capable of occluding and releasing lithium ions can be used as appropriate.
  • the separator 11 the nonaqueous electrolytic solution and the lithium salt, any conventionally proposed materials can be used. Description is omitted.
  • the battery 100 includes a battery can 12, a positive electrode plate lead piece 13, a negative electrode lead piece 14, a sealing lid 15, an insulating plate 16, and a packing 17.
  • the battery can 12 and the sealing lid 15 are made of, for example, stainless steel (SUS).
  • the positive electrode plate lead piece 13 electrically connects the positive electrode 1 and the sealing lid portion 15.
  • the battery cover 15 functions as a positive electrode of the battery 100.
  • the negative electrode lead piece 14 electrically connects the negative electrode 10 and the bottom of the battery can 12.
  • the battery can 12 main body specifically, the bottom of the battery can 12
  • the battery can 12 and the sealing lid portion 15 are electrically insulated by a packing 17.
  • the battery 100 can be reversibly charged and discharged, and by using the positive electrode of the present invention, it is possible to occlude lithium at a high concentration, so that a high-capacity lithium ion secondary battery is obtained. .
  • lithium migration in a layered solid solution compound can be facilitated, and a lithium ion battery having high performance and reliability can be provided.
  • a lithium ion battery having high performance and reliability can be provided.
  • small rechargeable batteries such as consumer devices but also electric vehicles, hybrid vehicles, tools It can be widely used for lithium ion secondary batteries that require a large size and a long life.

Abstract

This lithium ion secondary battery positive electrode comprises a positive electrode active material and a metal plate that fixes the positive electrode active material. The positive electrode active material is a lithium transition metal oxide represented by LixNiaMnbMcO2+y (a+b+c = 0.8, 0.95 ≦ x ≦ 1.2). On the surface area where the positive electrode active material is fixed, the metal plate has a (110) orientation portion having a face-centered cubic structure, and the positive electrode active material is produced by epitaxial growth on the metal plate. This positive electrode is characterized in that the theoretical value of the nearest interatomic distance in the metal plate is 87-89% of the theoretical value of the nearest interatomic distance of the positive electrode active substance.

Description

リチウムイオン二次電池用正極、およびリチウムイオン二次電池Positive electrode for lithium ion secondary battery and lithium ion secondary battery
　本発明は、リチウムイオン二次電池用正極、およびリチウムイオン二次電池に関する。 The present invention relates to a positive electrode for a lithium ion secondary battery and a lithium ion secondary battery.
　リチウムイオン二次電池用の正極活物質として、リチウムイオンを吸蔵・放出可能なリチウム遷移金属酸化物が知られている。層状岩塩構造を有するリチウム酸化物（ＬｉＭＯ2）や、オリビン型リン酸リチウム化合物（ＬｉＭＰＯ4）、スピネル型酸化物（ＬｉＭ2Ｏ4）が代表的であり、高出力、高エネルギ密度を達成するための検討がされている。 As a positive electrode active material for a lithium ion secondary battery, a lithium transition metal oxide capable of inserting and extracting lithium ions is known. Typical examples include lithium oxide (LiMO 2 ) having a layered rock salt structure, olivine-type lithium phosphate compound (LiMPO 4 ), and spinel-type oxide (LiM 2 O 4 ), which achieve high output and high energy density. Has been studied for.
　特開２００９－２９５５１４号公報（特許文献１）には、リチウムイオン二次電池を高性能化させる技術として、ＬｉＣｏＯ2からなる正極活物質中にリチウムイオンが出入りしやすくなるような結晶方位に配向させるための下地金属板として（１１０）配向の金や白金を用いる方法が開示されている。 In JP 2009-295514 A (Patent Document 1), as a technique for improving the performance of a lithium ion secondary battery, it is oriented in a crystal orientation such that lithium ions easily enter and exit a positive electrode active material made of LiCoO 2. A method of using (110) -oriented gold or platinum as a base metal plate for the purpose is disclosed.
　また、さらなる高容量化を達成するため、ＬｉＭＯ2からなる正極活物質よりもリチウムをより多く挿入・脱離させることができる物質として、Ｌｉ1.2Ｍ0.8Ｏ2で表される層状固溶体化合物が注目されている。リチウムを２０％多く含ませることが可能となり、大容量化に適した材料である（特開２０１２－１２９１０２号公報（特許文献２）等）。 Further, in order to achieve higher capacity, a layered solid solution compound represented by Li 1.2 M 0.8 O 2 has attracted attention as a material that can insert and desorb more lithium than a positive electrode active material made of LiMO 2. Has been. It can contain 20% more lithium, and is a material suitable for increasing the capacity (Japanese Patent Laid-Open No. 2012-129102 (Patent Document 2), etc.).
特開２００９－２９５５１４号公報JP 2009-295514 A 特開２０１２－１２９１０２号公報JP 2012-129102 A
　層状固溶体化合物を用いたリチウムイオン二次電池、特に正極の出力を向上させるために、上述の特許文献１を適用してもリチウムイオンの吸蔵・放出は容易とならず、リチウムイオン二次電池の高出力化は達成されない。 In order to improve the output of a lithium ion secondary battery using a layered solid solution compound, particularly the positive electrode, even if the above-mentioned Patent Document 1 is applied, the insertion and extraction of lithium ions is not easy. High output is not achieved.
　本発明は、高容量、高出力を達成しうるリチウムイオン二次電池用正極、及びリチウムイオン二次電池を提供することにある。 This invention is providing the positive electrode for lithium ion secondary batteries which can achieve a high capacity | capacitance and a high output, and a lithium ion secondary battery.
　上記課題を解決する本発明の正極は、正極活物質と、前記正極活物質を固定する金属板とを備え、正極活物質は、ＬｉxＮｉaＭｎbＭcＯ2+y（ａ＋ｂ＋ｃ＝０．８、０．９５≦ｘ≦１．２）で表わされるリチウム遷移金属酸化物であり、金属板は、正極活物質が固定された表面部に面心立方構造の（１１０）配向部分を有し、正極活物質は前記金属板上にエピタキシャル成長させたものであって、金属板の最近接原子間距離の理論値は、正極活物質の最近接原子間距離の理論値の８７～８９％であることを特徴とする。 The positive electrode of the present invention that solves the above problems includes a positive electrode active material and a metal plate that fixes the positive electrode active material, and the positive electrode active material is Li x Ni a Mn b M c O 2 + y (a + b + c = 0). .8, 0.95 ≦ x ≦ 1.2), and the metal plate has a (110) -oriented portion having a face-centered cubic structure on the surface portion to which the positive electrode active material is fixed. The positive electrode active material is epitaxially grown on the metal plate, and the theoretical value of the closest interatomic distance of the metal plate is 87 to 89% of the theoretical value of the closest interatomic distance of the positive electrode active material. It is characterized by being.
　また、他の本発明の正極は、正極活物質と、前記正極活物質を固定する金属板とを備え、正極活物質は、ＬｉxＮｉaＭｎbＭcＯ2+y（ａ＋ｂ＋ｃ＝０．８、０．９５≦ｘ≦１．２）で表わされるリチウム遷移金属酸化物であり、金属板は、正極活物質が固定された表面部に面心立方構造の（１１０）配向部分を有し、少なくとも表面部は、ニッケルまたはコバルトニッケル合金よりなる金属材料で構成され、正極活物質は前記金属板上にエピタキシャル成長させたものであることを特徴とする。 Another positive electrode of the present invention includes a positive electrode active material and a metal plate for fixing the positive electrode active material. The positive electrode active material is Li x Ni a Mn b McO 2 + y (a + b + c = 0. 8, 0.95 ≦ x ≦ 1.2), and the metal plate has a (110) -oriented portion having a face-centered cubic structure on the surface portion to which the positive electrode active material is fixed. The at least surface portion is made of a metal material made of nickel or a cobalt nickel alloy, and the positive electrode active material is epitaxially grown on the metal plate.
　また、上記課題を解決する本発明のリチウムイオン二次電池は、上記の正極と、リチウムを吸蔵放出する負極とを備えるものである。 Further, a lithium ion secondary battery of the present invention that solves the above-described problems comprises the above positive electrode and a negative electrode that occludes and releases lithium.
　上記本発明によれば、高容量、高出力を達成しうるリチウムイオン二次電池用正極、及びリチウムイオン二次電池を提供することができる。 According to the present invention, a positive electrode for a lithium ion secondary battery and a lithium ion secondary battery that can achieve high capacity and high output can be provided.
第１実施形態に係る正極の模式断面図である。It is a schematic cross section of the positive electrode which concerns on 1st Embodiment. 従来の正極活物質（ＬｉＣｏＯ2）の結晶構造を［１ １ － ２ ０］方向から見た図である。It is the figure which looked at the crystal structure of the conventional positive electrode active material (LiCoO 2 ) from the [1 1 -2 0] direction. 層状固溶体化合物（Ｌｉ1.2ＭｎｘＮｉｙＣｏｚＯ2）の結晶構造を［１ １ － ２ ０］方向から見た図である。It is the figure which looked at the crystal structure of the layered solid solution compound (Li 1.2 MnxNiyCozO 2 ) from the [1 1 -2 0] direction. 充電状態の層状固溶体化合物（Ｌｉ1.2ＭｎｘＮｉｙＣｏｚＯ2）の状態を示す図である。It is a diagram showing a state of laminar solid solution compound of the state of charge (Li 1.2 MnxNiyCozO 2). 層状固溶体化合物（Ｌｉ1.2ＭｎｘＮｉｙＣｏｚＯ2）の放電時のリチウムの移動について説明する図である。It is a diagram illustrating the movement of lithium during discharge of the layered solid solution compound (Li 1.2 MnxNiyCozO 2). 第１実施形態に係る正極の層状固溶体化合物（Ｌｉ1.2ＭｎｘＮｉｙＣｏｚＯ2）の放電時のリチウムの移動について説明する図である。Is a diagram illustrating the movement of lithium during discharge of the layered solid solution compound of the positive electrode according to the first embodiment (Li 1.2 MnxNiyCozO 2). （１１０）配向のニッケル金属板の（１１０）結晶面を示した図である。It is the figure which showed the (110) crystal plane of the nickel metal plate of (110) orientation. （１１０）配向のニッケル金属板の（－１００）結晶面を示した図である。FIG. 3 is a view showing a (−100) crystal plane of a (110) oriented nickel metal plate. 層状固溶体化合物（Ｌｉ1.2ＭｎｘＮｉｙＣｏｚＯ2）の（１－１００）結晶面を示した図である。1 is a view showing a (1-100) crystal plane of a layered solid solution compound (Li 1.2 MnxNiyCozO 2 ). FIG. 層状固溶体化合物（Ｌｉ1.2ＭｎｘＮｉｙＣｏｚＯ2）の（１ １ －２ ０）結晶面を示した図である。It is the figure which showed the (1 1 -20) crystal plane of the layered solid solution compound (Li 1.2 MnxNiyCozO 2 ). 層状固溶体化合物のリチウム層から遷移金属層へ移動するリチウムイオンの拡散速度に対する金属板の効果を示した図である。It is the figure which showed the effect of the metal plate with respect to the diffusion rate of the lithium ion which moves from the lithium layer of a layered solid solution compound to a transition metal layer. 第２実施形態に係る正極の模式断面図である。It is a schematic cross section of the positive electrode which concerns on 2nd Embodiment. リチウムイオン二次電池の構成例を示す部分断面図である。It is a fragmentary sectional view which shows the structural example of a lithium ion secondary battery.
　高出力及び高エネルギ密度のリチウムイオン二次電池は、近年、携帯電話等の民生用機器用電源として注目されている。また、このようなリチウムイオン二次電池は、エネルギを効率的に利用できる船舶、鉄道、自動車等の駆動用電源への適用も望まれている。さらには、例えば風力、太陽光等の自然エネルギを利用して発電した電力をリチウムイオン二次電池に蓄えたり、系統からの電力を蓄えたりする技術が家庭用にも産業用にも注目されている。また、ＩＴ（Information Technology）技術を利用したスマートグリッド（次世代送電網）においても、リチウムイオン二次電池を利用した技術が注目されている。 High-power and high-energy density lithium-ion secondary batteries have recently attracted attention as power sources for consumer devices such as mobile phones. In addition, such a lithium ion secondary battery is also desired to be applied to a driving power source for ships, railways, automobiles and the like that can efficiently use energy. Furthermore, for example, technologies for storing electric power generated using natural energy such as wind power and sunlight in lithium ion secondary batteries and storing electric power from the grid are attracting attention for both home and industrial use. Yes. In addition, a technology using a lithium ion secondary battery is also attracting attention in a smart grid (next-generation power transmission network) using IT (Information Technology) technology.
　リチウムイオン二次電池は、リチウムイオンを吸蔵・放出可能な正極及び負極が、セパレータを介して配置されており、リチウム塩を含む非水電解液によって満たされた電池容器内に密閉された構成を有し、可逆的に充放電を行う。 A lithium ion secondary battery has a configuration in which a positive electrode and a negative electrode capable of occluding and releasing lithium ions are arranged via a separator and sealed in a battery container filled with a non-aqueous electrolyte containing a lithium salt. And charge and discharge reversibly.
　通常、正極は、アルミニウム箔等の金属箔を集電体（電極板）とし、粉体よりなる正極活物質がバインダ（結着剤）によって、集電体に固定される。正極活物質としては、従来、層状岩塩構造を有するコバルト酸リチウム（ＬｉＣｏＯ2）や、コバルト酸リチウムのコバルト原子の一部又は全部がニッケル、マンガン等により置換されたリチウムと遷移金属との酸化物からなる粉体等が使用されている。 Usually, the positive electrode uses a metal foil such as an aluminum foil as a current collector (electrode plate), and a positive electrode active material made of powder is fixed to the current collector by a binder (binder). As the positive electrode active material, conventionally, lithium cobaltate (LiCoO 2 ) having a layered rock salt structure, or an oxide of lithium and transition metal in which a part or all of cobalt atoms of lithium cobaltate is substituted by nickel, manganese, or the like The powder etc. which consist of are used.
　層状固溶体化合物は、一般式αＬｉ2ＭｎＯ3－（１－α）ＬｉＭＯ2（ＭはＮｉ、Ｃｏ等の遷移金属を含む）で表わされ、２５０ｍＡｈ/ｇを超える高容量が期待される正極活物質材料である。ほかにも、基本組成Ｌｉ1.2ＭＯ2、Ｌｉ1.2Ｍ0.8Ｏ2などの形で表わす場合がある。従来の正極活物質材料であるＬｉＣｏＯ2などとよく似た結晶構造を持っているが、より理論容量が大きく、電池の大容量化に寄与することが期待されている。本願明細書では、ＬｉｘＮｉａＭｎｂＭｃＯ２＋ｙ（ａ＋ｂ＋ｃ＝０．８、０．９５以上ｘ以上１．２）で表わす。Ｍは、Ｎｉ、Ｍｎ以外の金属、遷移金属やその他の添加元素であり、Ｆｅ、Ｃｏ、Ｗ、Ｎｂ、Ｍｇ、Ａｌ等が含まれる。酸素はリチウムや金属の比率、含まれる元素に影響を受け、適宜増減する。 The layered solid solution compound is represented by the general formula αLi 2 MnO 3 — (1-α) LiMO 2 (M includes transition metals such as Ni and Co), and is expected to have a high capacity exceeding 250 mAh / g. It is a material. In addition, the basic composition may be expressed in the form of Li 1.2 MO 2 , Li 1.2 M 0.8 O 2 or the like. Although it has a crystal structure that is very similar to LiCoO 2 that is a conventional positive electrode active material, it has a larger theoretical capacity and is expected to contribute to an increase in battery capacity. In this specification, LixNiaMnbMcO2 + y (a + b + c = 0.8, 0.95 or more and x or more and 1.2). M is a metal other than Ni and Mn, a transition metal, and other additive elements, and includes Fe, Co, W, Nb, Mg, Al, and the like. Oxygen is affected by the ratio of lithium and metal and the elements contained, and increases or decreases as appropriate.
　しかしながら、大容量化を達成可能な層状固溶体化合物に、理論容量に近い範囲でリチウムイオンの吸蔵放出を達成させるため、正極活物質材料の内部までリチウムイオンが出入りしやすくなるような検討が必要である。本願発明者らは、鋭意研究を行った結果、正極活物質（層状固溶体化合物）中のリチウム層から遷移金属層にリチウムが移動しやすくなるように、エピタキシャル成長により正極活物質の結晶相を金属板に垂直な方向に配向させ、下地となる金属板との配向をそろえ、結晶相の原子間距離、特に下地金属板に垂直な方向の原子間距離を拡げることを試みた。具体的には、金属板の材料を選定するとともに、層状固溶体化合物を金属板の結晶面上にエピタキシャル成長させた。その際、活物質の最近接原子間距離の理論値に対し、下地となる金属板の最近接原子間距離の理論値を特定の範囲とすることが有効であった。 However, in order to achieve lithium ion storage and release within a range close to the theoretical capacity of a layered solid solution compound capable of achieving a large capacity, it is necessary to study so that lithium ions can easily enter and exit the cathode active material. is there. As a result of intensive research, the inventors of the present application have determined that the crystal phase of the positive electrode active material is formed by epitaxial growth so that lithium can easily move from the lithium layer in the positive electrode active material (layered solid solution compound) to the transition metal layer. We tried to expand the interatomic distance of the crystal phase, particularly the interatomic distance in the direction perpendicular to the underlying metal plate, by aligning in the direction perpendicular to the substrate and aligning the orientation with the underlying metal plate. Specifically, the material for the metal plate was selected, and the layered solid solution compound was epitaxially grown on the crystal plane of the metal plate. At that time, it was effective to set the theoretical value of the nearest interatomic distance of the underlying metal plate within a specific range with respect to the theoretical value of the nearest interatomic distance of the active material.
　なお、層状固溶体化合物は、従来の正極活物質材料であるＬｉＣｏＯ2などとよく似た結晶構造を持っている。そこで、特開２００９－２９５５１４号公報と同様に、下地となる金属板として（１１０）配向の金や白金を用いる方法も検討した。しかしながら、層状固溶体化合物を正極活物質として使用した場合では、リチウムイオンの吸蔵放出性能の向上は見られなかった。したがって、金または白金を金属板として用いることは有効でない。その分析については後述する。 The layered solid solution compound has a crystal structure that is very similar to LiCoO 2 that is a conventional positive electrode active material. Therefore, as in Japanese Patent Application Laid-Open No. 2009-295514, a method of using (110) -oriented gold or platinum as a metal plate as a base was also examined. However, when the layered solid solution compound is used as the positive electrode active material, the lithium ion storage / release performance was not improved. Therefore, it is not effective to use gold or platinum as the metal plate. The analysis will be described later.
　上記課題を解決する本発明の特徴は、リチウムイオンを吸蔵放出可能な正極及び負極を備えるリチウムイオン二次電池において、正極に、正極活物質と、正極活物質を固定する金属板とを備え、正極活物質は、ＬｉｘＮｉａＭｎｂＭｃＯ２+ｙ（ａ＋ｂ＋ｃ＝０．８、０．９５≦ｘ≦１．２）で表わされるリチウム遷移金属酸化物、いわゆる層状固溶体化合物であり、下地層となる金属板は、少なくとも正極活物質が固定される表面部に、面心立方構造の（１１０）配向部分を有し、前記正極活物質は前記金属板上にエピタキシャル成長させたものであって、金属板の最近接原子間距離の理論値は、正極活物質の最近接原子間距離の理論値の８７～８９％である。 A feature of the present invention that solves the above problems is a lithium ion secondary battery including a positive electrode and a negative electrode capable of occluding and releasing lithium ions, the positive electrode includes a positive electrode active material, and a metal plate that fixes the positive electrode active material, The positive electrode active material is a lithium transition metal oxide represented by LixNiaMnbMcO2 + y (a + b + c = 0.8, 0.95 ≦ x ≦ 1.2), a so-called layered solid solution compound, and the metal plate serving as the underlayer is at least The surface portion to which the positive electrode active material is fixed has a (110) oriented portion having a face-centered cubic structure, and the positive electrode active material is epitaxially grown on the metal plate, The theoretical value of the distance is 87 to 89% of the theoretical value of the closest interatomic distance of the positive electrode active material.
　上記の構成により、正極活物質の原子密度最密結晶面が金属板に対して垂直方向となり、正極活物質の原子間距離が金属板に垂直な方向に引き伸ばされて、リチウム層と遷移金属層の相互のリチウムの移動を円滑化し、性能、信頼性の高いリチウムイオン二次電池を提供することが可能となる。 With the above configuration, the atomic density close-packed crystal plane of the positive electrode active material is perpendicular to the metal plate, and the interatomic distance of the positive electrode active material is extended in the direction perpendicular to the metal plate, so that the lithium layer and the transition metal layer Therefore, it is possible to provide a lithium ion secondary battery with high performance and reliability.
　特に、上記の正極活物質は、金属板の表面にエピタキシャル成長させて形成されたものであることが好ましい。金属板表面の金属元素に正極活物質の各元素が結晶成長する。また、正極活物質の最近接酸素原子間距離が０．２８１ｎｍ以上０．２８８ｎｍ以下、金属板の最近接原子間距離の理論値が０．２４４ｎｍ以上０．２５３ｎｍ以下であることが好ましい。具体的には、金属板の少なくとも表面をニッケルまたはコバルトニッケル合金とする。金属板は、表面のみに面心立方構造の（１１０）配向部分を備えればよい。したがって、ニッケル層またはコバルトニッケル合金、もしくはそれ以外の導電性を備える基材と、前記基材上に設けられたニッケル層またはコバルトニッケル合金層とを備えればよい。さらに、最表面に面心立方構造の（１１０）配向部分が存在すればよく、内部の配向は適宜選択できるし、配向が存在しないものでもよい。特に、金属板の最近接原子間距離の理論値は、正極活物質の最近接原子間距離の理論値の８７～８８％であることが好ましい。 In particular, the positive electrode active material is preferably formed by epitaxial growth on the surface of a metal plate. Each element of the positive electrode active material grows on the metal element on the surface of the metal plate. Moreover, it is preferable that the nearest oxygen atom distance of the positive electrode active material is 0.281 nm or more and 0.288 nm or less, and the theoretical value of the nearest atom distance of the metal plate is 0.244 nm or more and 0.253 nm or less. Specifically, at least the surface of the metal plate is made of nickel or cobalt nickel alloy. The metal plate may be provided with a (110) -oriented portion having a face-centered cubic structure only on the surface. Therefore, a nickel layer or a cobalt nickel alloy, or a base material having conductivity other than that, and a nickel layer or a cobalt nickel alloy layer provided on the base material may be provided. Furthermore, the (110) -oriented portion having a face-centered cubic structure may be present on the outermost surface, and the internal orientation can be selected as appropriate, or the orientation may not exist. In particular, the theoretical value of the nearest interatomic distance of the metal plate is preferably 87 to 88% of the theoretical value of the nearest interatomic distance of the positive electrode active material.
　上記構成により、大容量のリチウムイオン二次電池に好適であって、出力が高い正極を提供できる。 The above configuration can provide a positive electrode that is suitable for a large-capacity lithium ion secondary battery and has a high output.
　以下、図面を参照しながら本発明を実施するための形態（本実施形態）を説明する。 Hereinafter, embodiments for carrying out the present invention (this embodiment) will be described with reference to the drawings.
　図１は、第１の実施形態に係る正極の模式断面図である。リチウムイオン二次電池に適用されるリチウムイオンを吸蔵放出可能な正極１は、金属板２と、リチウムイオンを吸蔵放出可能な正極活物質層３により構成される。本実施例の正極活物質層３には、正極活物質として層状固溶体化合物、Ｌｉ1.2ＭｎｘＮｉｙＣｏｚＯ2   （ただし、ｘ＋ｙ＋ｚ＝０．８）を用いる。 FIG. 1 is a schematic cross-sectional view of a positive electrode according to the first embodiment. A positive electrode 1 capable of occluding and releasing lithium ions applied to a lithium ion secondary battery includes a metal plate 2 and a positive electrode active material layer 3 capable of occluding and releasing lithium ions. For the positive electrode active material layer 3 of the present example, a layered solid solution compound, Li 1.2 MnxNiyCozO 2 (x + y + z = 0.8) is used as the positive electrode active material.
　層状固溶体化合物Ｌｉ1.2ＭｎｘＮｉｙＣｏｚＯ2   （ただし、ｘ＋ｙ＋ｚ＝０．８）は、Ｌｉ（Ｌｉ0.2Ｍ0.8）Ｏ2と書けるため、遷移金属Ｍｎ、Ｎｉ、Ｃｏが８０ａｔ.％存在する遷移金属層にリチウムが２０％入り込んだ構造とみなすことができる。したがって、リチウムが抜けた充電状態からスタートしてリチウムを挿入していった場合、Ｌｉ（Ｌｉ0.2Ｍ0.8）Ｏ2の状態になるまでリチウムを挿入することができれば、従来材料のＬｉＣｏＯ2よりもリチウムを２０ａｔ.％多く挿入することができ、大容量化することが可能となる。 Since the layered solid solution compound Li 1.2 MnxNiyCozO 2 (where x + y + z = 0.8) can be written as Li (Li 0.2 M 0.8 ) O 2 , lithium is present in the transition metal layer where the transition metals Mn, Ni, and Co are present at 80%. It can be regarded as a structure with 20% penetration. Therefore, when lithium is inserted starting from a charged state in which lithium is removed, if lithium can be inserted until it reaches a state of Li (Li 0.2 M 0.8 ) O 2 , it will be more than the conventional material LiCoO 2. Lithium can be inserted in an amount of 20 at.%, And the capacity can be increased.
　発明者らは、従来材料のＬｉＣｏＯ2よりも大容量化できる層状固溶体化合物Ｌｉ1.2ＭｎｘＮｉｙＣｏｚＯ2   （ただし、ｘ＋ｙ＋ｚ＝０．８）にリチウムイオンが出入りしやすくなるようにさせるために鋭意研究をおこなった結果、Ｌｉ1.2ＭｎｘＮｉｙＣｏｚＯ2   （ただし、ｘ＋ｙ＋ｚ＝０．８）の配向をそろえるとともに、Ｌｉ1.2ＭｎｘＮｉｙＣｏｚＯ2   中においてリチウム層から遷移金属層にリチウムが移動しやすくなるように、下地金属板に垂直な方向の原子間距離を拡げることができるような金属板材料を選定することが有効であることを見出した。 The inventors have conducted intensive research to make it easier for lithium ions to enter and exit the layered solid solution compound Li 1.2 MnxNiyCozO 2 (where x + y + z = 0.8), which can have a larger capacity than the conventional LiCoO 2 material. As a result, the orientation of Li 1.2 MnxNiyCozO 2 (where x + y + z = 0.8) is aligned, and the direction perpendicular to the underlying metal plate is such that lithium can easily move from the lithium layer to the transition metal layer in Li 1.2 MnxNiyCozO 2. It has been found that it is effective to select a metal plate material that can increase the interatomic distance.
　図２に、［１ １ - ２ ０］方向から見た従来の正極活物質（ＬｉＣｏＯ2）の結晶構造（図２（Ａ））と、層状固溶体化合物（Ｌｉ1.2ＭｎｘＮｉｙＣｏｚＯ2）の結晶構造（図２（Ｂ））とを示す。各原子の大きさは、リチウム（α層、α’層）が最大、その次が酸素（β層、β’層）、最小が遷移金属（γ層、γ’層）であり、それぞれが並んだ層状構造となっている。図２（Ｂ）に示す通り、層状固溶体化合物は、黒で表した過剰量のリチウム元素４が遷移金属層（γ層）に入りこんだ状態となっている。 FIG. 2 shows the crystal structure (FIG. 2A) of the conventional positive electrode active material (LiCoO 2 ) and the crystal structure of the layered solid solution compound (Li 1.2 MnxNiyCozO 2 ) as seen from the [1 1 -2 0] direction. 2 (B)). As for the size of each atom, lithium (α layer, α ′ layer) is the largest, next is oxygen (β layer, β ′ layer), and the smallest is transition metal (γ layer, γ ′ layer). It has a layered structure. As shown in FIG. 2B, the layered solid solution compound is in a state where an excessive amount of lithium element 4 expressed in black has entered the transition metal layer (γ layer).
　図３は、充電し、リチウムが空になっている層状固溶体化合物の状態を示す図である。リチウム層５は、充電によりリチウムが抜け、空になっている。また、遷移金属層に含まれていたリチウム元素４も放出された状態である。放電に伴い、リチウムイオンが正極活物質層に吸蔵される。リチウムは第一段階ではリチウム層に入る（第一段階）。リチウム層が充填された後に、横方向へ移動して遷移金属層に入る（第二段階）。つまり、リチウムが入りこんだリチウム層から、遷移金属層に移動する形で遷移金属層にリチウムを充填するのであるが、リチウム層から遷移金属層にリチウムを移動させる拡散速度が非常に遅い。遷移金属（Ｍｎ、Ｎｉ、Ｃｏ）が８０ａｔ.％存在する遷移金属層にリチウムが２０％入り込んだ状態にすることは、実際に電池として使用する条件では達成困難である。 FIG. 3 is a diagram showing a state of a layered solid solution compound that is charged and lithium is empty. The lithium layer 5 is emptied when lithium is removed by charging. Further, the lithium element 4 contained in the transition metal layer is also released. Accompanying the discharge, lithium ions are occluded in the positive electrode active material layer. Lithium enters the lithium layer in the first stage (first stage). After the lithium layer is filled, it moves laterally and enters the transition metal layer (second stage). That is, the lithium is filled into the transition metal layer so as to move from the lithium layer into which lithium has entered, but the diffusion rate for moving lithium from the lithium layer to the transition metal layer is very slow. It is difficult to achieve a state in which 20% of lithium enters a transition metal layer in which 80 at.% Of transition metals (Mn, Ni, Co) are present under the conditions of actual use as a battery.
　図４は、層状固溶体化合物（Ｌｉ1.2ＭｎｘＮｉｙＣｏｚＯ2）の放電時のリチウムの移動について説明する図である。リチウム原子がリチウム層から遷移金属層の空格子点に移動しようとする場合、空格子点のまわりの原子間距離が狭く、リチウム原子が移動する際に酸素原子６、７が障害となる。したがって、リチウム層から遷移金属層へのリチウムの移動は起こり難く、遷移金属層にリチウムを充填するのは難しい。そこで、発明者らは、障害となる酸素原子６、７の間隙を広げるため、下地金属板に垂直な方向の原子間距離を拡げ、リチウム層から遷移金属層への移動を容易とすることを試みた。 FIG. 4 is a diagram for explaining the movement of lithium during discharge of a layered solid solution compound (Li 1.2 MnxNiyCozO 2 ). When lithium atoms try to move from the lithium layer to the vacancies of the transition metal layer, the interatomic distance around the vacancies is narrow, and the oxygen atoms 6 and 7 become obstacles when the lithium atoms move. Therefore, lithium does not easily move from the lithium layer to the transition metal layer, and it is difficult to fill the transition metal layer with lithium. In order to widen the gap between the oxygen atoms 6 and 7, which are obstructive, the inventors have increased the interatomic distance in the direction perpendicular to the base metal plate to facilitate the movement from the lithium layer to the transition metal layer. Tried.
　図５は、本実施形態に係る（１１０）配向を持つニッケル金属板２の上に、層状固溶体化合物Ｌｉ1.2ＭｎｘＮｉｙＣｏｚＯ2の層３を形成した正極の例の結晶構造の断面図を示す。層状固溶体化合物を[１ １ － ２ ０]方向から見ると、ニッケル金属板の影響を受けて、層状固溶体化合物層が金属板に垂直な方向（矢印方向）の引張ひずみにより引き伸ばされている状態となっており、図の縦方向の原子間距離が大きくなるため、リチウム層から遷移金属層への移動が生じやすい。 FIG. 5 shows a cross-sectional view of the crystal structure of an example of the positive electrode in which the layer 3 of the layered solid solution compound Li 1.2 MnxNiyCozO 2 is formed on the nickel metal plate 2 having the (110) orientation according to the present embodiment. When the layered solid solution compound is viewed from the [1 1 -2 0] direction, the layered solid solution compound layer is stretched by tensile strain in the direction perpendicular to the metal plate (arrow direction) under the influence of the nickel metal plate. Since the interatomic distance in the vertical direction in the figure is increased, the movement from the lithium layer to the transition metal layer is likely to occur.
　図５を用い、第１実施形態に係る正極での層状固溶体化合物（Ｌｉ1.2ＭｎｘＮｉｙＣｏｚＯ2）の放電時のリチウムの移動について説明する。本実施の形態では、下地となる（１１０）配向のニッケルの金属板と、層状固溶体化合物よりなる正極活物質層を備える。金属板の影響により、金属板に垂直な方向（図の上下方向）に正極活物質層の引張ひずみを発生させ、原子間距離を金属板に垂直な方向に引き伸ばしている。つまり、金属板に垂直な方向の原子間距離を広げることによって、リチウムが移動する際の経路を広げることができる。その結果、無ひずみ（図４）では障害となっていた酸素原子１、２がリチウム原子の移動経路上から無くなるため、リチウム層から遷移金属層へ（矢印方向）のリチウムの移動が起こりやすくなる。 The movement of lithium during discharge of the layered solid solution compound (Li 1.2 MnxNiyCozO 2 ) at the positive electrode according to the first embodiment will be described with reference to FIG. In this embodiment, a nickel metal plate of (110) orientation serving as a base and a positive electrode active material layer made of a layered solid solution compound are provided. Due to the influence of the metal plate, tensile strain of the positive electrode active material layer is generated in the direction perpendicular to the metal plate (up and down direction in the figure), and the interatomic distance is extended in the direction perpendicular to the metal plate. That is, by increasing the interatomic distance in the direction perpendicular to the metal plate, the path for lithium movement can be expanded. As a result, the oxygen atoms 1 and 2 that have become obstacles in the unstrained state (FIG. 4) disappear from the movement path of the lithium atoms, and thus lithium movement from the lithium layer to the transition metal layer (arrow direction) is likely to occur. .
　下地となる金属層の、正極活物質層の原子間距離への影響について、（１１０）配向のニッケルを例とし、図６及び図７を用いて説明する。図６（Ａ）に、（１１０）配向のニッケル金属板を[１１０]方向から見た（１１０）結晶面（ニッケル金属板に垂直な方向から見た図）、図６（Ｂ）に[－１１０]方向から見た（－１００）結晶面（ニッケル金属板に平行な方向から見た図）を示す。図７は、層状固溶体化合物Ｌｉ1.2ＭｎｘＮｉｙＣｏｚＯ2を空間群Ｒ-３ｍ（六方晶）で表現した場合の（１ -１ ０ ０）結晶面（図７（Ａ））と、（１ １ － ２ ０）結晶面（図７（Ｂ））を示す図である。なお、層状固溶体化合物Ｌｉ1.2ＭｎｘＮｉｙＣｏｚＯ2は、空間群Ｃ２/ｍで表現することができるが、Ｘ線回折によって得られる２２°付近のピークに相当する例外的な格子点を除いた全体構造は、空間群Ｒ-３ｍ（六方晶）で表現することができる。そして、空間群Ｒ-３ｍにおける層状固溶体化合物Ｌｉ1.2ＭｎｘＮｉｙＣｏｚＯ2の格子定数a（最近接酸素原子間距離）は、x＋y＋z＝０．８を満たすx、y、zの比率に応じて、０．２８１ｎｍ以上０．２８８ｎｍ以下の値をとる。 The influence of the metal layer serving as the base on the interatomic distance of the positive electrode active material layer will be described using (110) oriented nickel as an example with reference to FIGS. FIG. 6A shows a (110) crystal plane (viewed from a direction perpendicular to the nickel metal plate) of a (110) -oriented nickel metal plate viewed from the [110] direction, and FIG. The (-100) crystal plane (viewed from a direction parallel to the nickel metal plate) viewed from the 110] direction is shown. FIG. 7 shows the (1 −1 0 0) crystal plane (FIG. 7A) when the layered solid solution compound Li 1.2 MnxNiyCozO 2 is expressed by the space group R-3m (hexagonal crystal), and (1 1 −2 0 FIG. 8 is a diagram showing a crystal plane (FIG. 7B). The layered solid solution compound Li 1.2 MnxNiyCozO 2 can be expressed by the space group C2 / m, but the overall structure excluding exceptional lattice points corresponding to a peak around 22 ° obtained by X-ray diffraction is It can be expressed by the space group R-3m (hexagonal crystal). The lattice constant a (distance between nearest oxygen atoms) of the layered solid solution compound Li 1.2 MnxNiyCozO 2 in the space group R-3m is 0.281 nm depending on the ratio of x, y, and z satisfying x + y + z = 0.8. The value is not less than 0.288 nm.
　図６、図７を比較すると、図７（Ａ）の層状固溶体化合物Ｌｉ1.2ＭｎｘＮｉｙＣｏｚＯ2の（１ －１ ００）結晶面は、短辺（最近接酸素原子間距離）が０．２８１ｎｍ以上０．２８８ｎｍ以下で、長辺が、０．３６８ｎｍ以上０．３９８ｎｍ以下の長方形を単位格子とする結晶面である。一方、図６（Ａ）のニッケル金属板の（１１０）面は、短辺が０．２４９ｎｍで、長辺が０．３５２ｎｍの長方形を単位格子とする結晶面である。層状固溶体化合物Ｌｉ1.2ＭｎｘＮｉｙＣｏｚＯ2の（１ －１ ０ ０）結晶面とニッケルの（１１０）面は、よく似た構造を持ち、なおかつ層状固溶体化合物Ｌｉ1.2ＭｎｘＮｉｙＣｏｚＯ2の（１ －１ ０ ０）結晶面よりもニッケルの（１１０）面は、約１２％小さい単位格子から構成されている。 6 and FIG. 7, the (1 −100) crystal plane of the layered solid solution compound Li 1.2 MnxNiyCozO 2 in FIG. 7A has a short side (distance between nearest oxygen atoms) of 0.281 nm or more. It is a crystal plane having a unit cell of a rectangle having a length of 288 nm or less and a long side of 0.368 nm or more and 0.398 nm or less. On the other hand, the (110) plane of the nickel metal plate in FIG. 6 (A) is a crystal plane with a rectangular unit having a short side of 0.249 nm and a long side of 0.352 nm as a unit cell. The (1 -1 0 0) crystal plane of the layered solid solution compound Li 1.2 MnxNiyCozO 2 and the (110) plane of nickel have a similar structure, and the (1 -1 0 0) crystal of the layered solid solution compound Li 1.2 MnxNiyCozO 2 The (110) face of nickel than the face is made up of unit cells about 12% smaller.
　このため、（１１０）配向を持つニッケル金属板の上に、層状固溶体化合物Ｌｉ1.2ＭｎｘＮｉｙＣｏｚＯ2の層を形成すると、層状固溶体化合物Ｌｉ1.2ＭｎｘＮｉｙＣｏｚＯ2は（１ －１ ０ ０）配向を持った状態でエピタキシャル成長（単結晶的に下地と同様の構造で成長）し、なおかつ単位格子の小さなニッケルによって層状固溶体化合物Ｌｉ1.2ＭｎｘＮｉｙＣｏｚＯ2はニッケル金属板に平行な方向に縮められた状態（圧縮ひずみ状態）となる。この影響を受けて、ニッケル金属板に垂直な方向にはポアッソン比の分だけ引き伸ばされた状態（引張ひずみ状態）で層状固溶体化合物Ｌｉ1.2ＭｎｘＮｉｙＣｏｚＯ2が形成される。 Therefore, when a layered solid solution compound Li 1.2 MnxNiyCozO 2 is formed on a nickel metal plate having a (110) orientation, the layered solid solution compound Li 1.2 MnxNiyCozO 2 has a (1 −1 0 0) orientation. The layered solid solution compound Li 1.2 MnxNiyCozO 2 is contracted in a direction parallel to the nickel metal plate (compressed strain state) by epitaxial growth (single crystal growth with the same structure as the base) and nickel with a small unit cell. . Under the influence, a layered solid solution compound Li 1.2 MnxNiyCozO 2 is formed in a state (tensile strain state) stretched by a Poisson's ratio in a direction perpendicular to the nickel metal plate.
　上記の通り、下地材料を選択することで、従来より知られた薄膜成長法方法によりエピタキシャル成長がみられる。エピタキシャル成長は、Ｌｉ1.2ＭｎｘＮｉｙＣｏｚＯ2+yのターゲットを用い、例えばスパッタリング法や電子ビーム蒸着法などにより、ターゲットから原子を放出させ、基材上等に堆積させる結晶成長方法である。 As described above, epitaxial growth is observed by a conventionally known thin film growth method by selecting a base material. Epitaxial growth is a crystal growth method in which a Li 1.2 MnxNiyCozO 2 + y target is used and atoms are released from the target by, for example, sputtering or electron beam evaporation, and deposited on a substrate.
　次に、金属板を構成する金属の最近接酸素原子間距離の値が層状固溶体化合物Ｌｉ1.2ＭｎｘＮｉｙＣｏｚＯ2の値（０．２８１ｎｍ以上０．２８８ｎｍ以下）よりもどの程度小さければ金属板に平行な方向に縮める効果（すなわち金属板に垂直な方向に引き伸ばす効果）が得られるのかを分子動力学シミュレーションを用いて解析した。金属板の最近接原子間距離の理論値と正極活物質の最近接酸素原子間距離の相対差は、層状固溶体化合物の最近接原子間距離の理論値から金属板の最近接原子間距離の理論値を差し引き、それを層状固溶体化合物の最近接原子間距離の理論値で割ってから１００を掛けてパーセントで表示したものである。相対差が負になる場合、すなわち金属板の最近接原子間距離の理論値が大きい場合は、金属板に平行な方向に縮める効果（すなわち金属板に垂直な方向に引き伸ばす効果）は無いので、正の場合についてのみ検討した。シミュレーションを適用した層状固溶体化合物は、Ｌｉ1.2ＭｎｘＮｉｙＣｏｚＯ2で、ｘ＝０．４８,ｙ＝０．３２,ｚ＝０の場合、ｘ＝０．４８,ｙ＝０．２４,ｚ＝０．０８の場合、ｘ＝０．４０,ｙ＝０．２４,ｚ＝０．１６の場合である。Ｌｉ欠損５０％（放電時）のリチウムの拡散速度（ｍ2/ｓ）を計算した。拡散速度は、Ｌｉ層に含まれるＬｉ原子が、遷移金属層に移動する速度を示すものであり、分子動力学シミュレーションでは、例えばBio Physical Journal, Vol. 75の150ページに記載されているように、原子の平均二乗変位と拡散係数の関係を示すアインシュタインの関係を用いて求めた。 Next, the direction parallel to the metal plate should be smaller than the value of the distance between nearest oxygen atoms of the metal constituting the metal plate than the value of the layered solid solution compound Li 1.2 MnxNiyCozO 2 (from 0.281 nm to 0.288 nm). It was analyzed using molecular dynamics simulations whether the effect of shrinking to a width (that is, the effect of stretching in a direction perpendicular to the metal plate) was obtained. The relative difference between the distance between the nearest atoms in the metal plate and the distance between the nearest oxygen atoms in the positive electrode active material is calculated from the theoretical distance between the nearest atoms in the layered solid solution compound. The value is subtracted and divided by the theoretical value of the closest interatomic distance of the layered solid solution compound and then multiplied by 100 and expressed as a percentage. When the relative difference is negative, that is, when the theoretical value of the distance between nearest atoms of the metal plate is large, there is no effect of shrinking in the direction parallel to the metal plate (ie, the effect of stretching in the direction perpendicular to the metal plate). Only positive cases were considered. The layered solid solution compound to which the simulation is applied is Li 1.2 MnxNiyCozO 2 , and when x = 0.48, y = 0.32, z = 0, x = 0.48, y = 0.24, z = 0.08. In this case, x = 0.40, y = 0.24, z = 0.16. The diffusion rate (m 2 / s) of lithium with 50% Li deficiency (during discharge) was calculated. The diffusion rate indicates the rate at which Li atoms contained in the Li layer move to the transition metal layer. In the molecular dynamics simulation, for example, as described in page 150 of Bio Physical Journal, Vol. 75. It was obtained using Einstein's relationship indicating the relationship between the mean square displacement of atoms and the diffusion coefficient.
　この結果を図８に示す。縦軸には、金属板が層状固溶体化合物にひずみを与えてリチウムの移動経路を広げる効果が、層状固溶体化合物のリチウム層から遷移金属層へ移動するリチウムイオンの拡散速度で示されており、横軸には、層状固溶体化合物との最近接原子間距離の理論値の相対差をとっている。 This result is shown in FIG. On the vertical axis, the effect of the metal plate distorting the layered solid solution compound to widen the migration path of lithium is shown by the diffusion rate of lithium ions moving from the lithium layer to the transition metal layer of the layered solid solution compound. The axis shows the relative difference in the theoretical value of the distance between the nearest atoms with the layered solid solution compound.
　ｘ、ｙ、ｚを変化させたいずれの化合物の場合も、金属板の最近接原子間距離が前記正極活物質の最近接酸素原子間距離よりも小さく、かつ金属板の最近接原子間距離と前記正極活物質の最近接酸素原子間距離の相対差が１１％以上１３％以下の場合（金属板の最近接原子間距離の理論値が、正極活物質の最近接原子間距離の理論値の８７～８９％の場合）にリチウムの拡散速度が顕著に大きくなり、金属板に平行な方向に縮められる効果（すなわち金属板に垂直な方向に引き伸ばされる効果）により移動経路が広げられる効果が得られることがわかる。 In any compound in which x, y, and z are changed, the distance between the nearest atoms of the metal plate is smaller than the distance between the nearest oxygen atoms of the positive electrode active material, and the distance between the nearest atoms of the metal plate is When the relative difference in the distance between the nearest oxygen atoms of the positive electrode active material is 11% or more and 13% or less (the theoretical value of the nearest atomic distance of the metal plate is the theoretical value of the nearest interatomic distance of the positive electrode active material) In the case of 87 to 89%), the diffusion rate of lithium is remarkably increased, and the effect of expanding the movement path by the effect of contracting in the direction parallel to the metal plate (that is, the effect of extending in the direction perpendicular to the metal plate) is obtained. I understand that
　このような効果が得られる金属板材料として、相対差が１１％以上１３％以下に相当するニッケルと、コバルトニッケル合金がある。なお、コバルト単体の場合には、面心立方構造ではなく、最密六方構造となるため、ひずみを与える効果が得られない。ニッケルを４％以上含有する場合に、コバルトニッケル合金が面心立方構造となるため、本実施例の効果が得られる。この場合にも、前述したニッケルの場合と同様に、（１１０）配向のコバルトニッケル合金が有効である。 As a metal plate material capable of obtaining such an effect, there are nickel corresponding to a relative difference of 11% to 13% and a cobalt nickel alloy. In addition, in the case of a cobalt simple substance, since it is not a face-centered cubic structure but a close-packed hexagonal structure, the effect of giving strain cannot be obtained. When nickel is contained in an amount of 4% or more, the cobalt nickel alloy has a face-centered cubic structure, so that the effect of this embodiment can be obtained. Also in this case, as in the case of nickel described above, a (110) -oriented cobalt nickel alloy is effective.
　なお、上記検討結果を踏まえ、金属板１として（１１０）配向の金、または白金を用いる方法についての考察を行った。金もニッケルと同様の面心立方構造を持つが、その（１１０）面は、短辺（最近接酸素原子間距離）が０．２８８ｎｍで、長辺が０．４０８ｎｍの長方形を単位格子とする結晶面であり、最近接酸素原子間距離の値（０．２８８ｎｍ）が層状固溶体化合物Ｌｉ1.2ＭｎｘＮｉｙＣｏｚＯ2の値（０．２８１ｎｍ以上０．２８８ｎｍ以下）と同等または大きい。したがって、金属板に平行な方向に圧縮ひずみを生じさせる効果を奏しない。また、白金もニッケルと同様の面心立方構造を持つが、その（１１０）面は、短辺（最近接酸素原子間距離）が０．２７７ｎｍで、長辺が０．３９２ｎｍの長方形を単位格子とする結晶面であり、最近接酸素原子間距離の値（０．２７７ｎｍ）が層状固溶体化合物Ｌｉ1.2ＭｎｘＮｉｙＣｏｚＯ2の値（０．２８１ｎｍ以上０．２８８ｎｍ以下）よりも小さい。しかし、白金、パラジウム、イリジウム等は、最近接原子間距離相対差が３％程度であり、有効ではないことが図８から明らかとなった。 Based on the above examination results, a method of using (110) oriented gold or platinum as the metal plate 1 was considered. Gold also has a face-centered cubic structure similar to that of nickel, but its (110) plane has a rectangular unit with a short side (distance between nearest oxygen atoms) of 0.288 nm and a long side of 0.408 nm as a unit cell. It is a crystal plane, and the closest distance between oxygen atoms (0.288 nm) is equal to or larger than the value of the layered solid solution compound Li 1.2 MnxNiyCozO 2 (from 0.281 nm to 0.288 nm). Therefore, there is no effect of causing compressive strain in a direction parallel to the metal plate. Platinum also has a face-centered cubic structure similar to that of nickel, but its (110) plane has a rectangular unit with a short side (distance between nearest oxygen atoms) of 0.277 nm and a long side of 0.392 nm. The distance between the nearest oxygen atoms (0.277 nm) is smaller than the value of the layered solid solution compound Li 1.2 MnxNiyCozO 2 (0.281 nm or more and 0.288 nm or less). However, it is clear from FIG. 8 that platinum, palladium, iridium, etc. are not effective because the closest relative distance difference is about 3%.
　ほかの金属についても、最近接原子間距離の理論値の相対差より検討を行った。図８の横軸の下に示したように、ルテニウム、オスミウム、亜鉛、銅は、最近接原子間距離の相対差が小さく、効果が小さい。一方、相対差が１３％よりも大きなマンガン、ガリウム、ゲルマニウムは、相対差が大きくなりすぎ、層状固溶体化合物がアモルファスのように規則性の低い原子配列となってしまうため、リチウムの移動経路がつぶれてしまうため、効果が小さくなった。 Other metals were also examined based on the relative difference in the theoretical value of the closest interatomic distance. As shown below the horizontal axis in FIG. 8, ruthenium, osmium, zinc, and copper have a small relative difference in the distance between the nearest atoms and a small effect. On the other hand, manganese, gallium, and germanium having a relative difference of more than 13% have too large a relative difference, and the layered solid solution compound has an atomic arrangement with low regularity like amorphous, so that the lithium migration path is broken. Therefore, the effect was reduced.
　上記の通り、本実施の形態によれば、正極活物質のリチウムの移動が容易であって、リチウム層から遷移金属層にリチウムを容易に移動できる正極が提供できる。その結果、リチウムが高濃度に入り込むことができ（Ｌｉ1.2ＭｎｘＮｉｙＣｏｚＯ2においては、酸素量の０．６倍の量になるまで入り込むことができ）、高容量のリチウムイオン二次電池となる。 As described above, according to the present embodiment, it is possible to provide a positive electrode in which lithium of the positive electrode active material can be easily transferred and lithium can be easily transferred from the lithium layer to the transition metal layer. As a result, lithium can enter a high concentration (in Li 1.2 MnxNiyCozO 2 , it can enter up to 0.6 times the amount of oxygen), resulting in a high-capacity lithium ion secondary battery.
　また、第一実施形態の正極構造では、電解質側へリチウムが出たり、電解質側から入ったりする場合に、出入りしやすい結晶面を表面に出すことができ、有効な結晶面が多い正極の構造とすることができるため、出力向上につながる。また、第一実施形態の正極構造では、バインダ樹脂を使用する必要がなく、電極密度の向上とともに劣化回避による長寿命化の可能性がある。 In addition, in the positive electrode structure of the first embodiment, when lithium comes out to the electrolyte side or enters from the electrolyte side, it is possible to bring out a crystal face that is easy to go in and out, and the structure of the positive electrode with many effective crystal faces Can lead to improved output. Further, in the positive electrode structure of the first embodiment, it is not necessary to use a binder resin, and there is a possibility of extending the life by improving the electrode density and avoiding deterioration.
　図９は、第２実施形態を示す図であり、層状固溶体化合物層と基材との間に結晶欠陥修復層のある正極構造を示す。金属板２が基材８と、基材８の表面に形成された結晶欠陥修復層９とよりなり、正極活物質３の層は、結晶欠陥修復層２上に設けられている。結晶欠陥修復層は金属膜であって、第一実施形態と同様に、表面が面心立方構造の（１１０）配向であり、当該結晶欠陥修復層を構成する金属材料の最近接原子間距離の理論値が、正極活物質の最近接原子間距離の理論値の８７～８９％である。また、正極活物質はＬｉｘＮｉａＭｎｂＭｃＯ２+ｙ（ａ＋ｂ＋ｃ＝０．８、０．９５≦ｘ≦１．２）で表わされるリチウム遷移金属酸化物（層状固溶体化合物）である。このような構成とすることで、基材に結晶欠陥が多い場合等にも、引張ひずみを有する状態の正極活物質層を形成でき、リチウム拡散速度を高めた正極となる。基材は、表面に結晶欠陥修復層を形成できるものであればよく、導電性の材料とすることが好ましい。 FIG. 9 is a diagram showing a second embodiment, and shows a positive electrode structure having a crystal defect repair layer between a layered solid solution compound layer and a substrate. The metal plate 2 includes a substrate 8 and a crystal defect repair layer 9 formed on the surface of the substrate 8, and the layer of the positive electrode active material 3 is provided on the crystal defect repair layer 2. The crystal defect repair layer is a metal film, and as in the first embodiment, the surface has a (110) orientation having a face-centered cubic structure, and the distance between nearest atoms of the metal material constituting the crystal defect repair layer is The theoretical value is 87 to 89% of the theoretical value of the closest interatomic distance of the positive electrode active material. The positive electrode active material is a lithium transition metal oxide (layered solid solution compound) represented by LixNiaMnbMcO2 + y (a + b + c = 0.8, 0.95 ≦ x ≦ 1.2). By setting it as such a structure, even when there are many crystal defects in a base material etc., the positive electrode active material layer of the state which has a tensile strain can be formed, and it becomes a positive electrode which improved the lithium diffusion rate. The substrate may be any material as long as it can form a crystal defect repair layer on the surface, and is preferably a conductive material.
　例えば、従来より集電体として使用されているアルミ板の上に、スパッタリングなどでニッケル膜を結晶欠陥修復層として成膜し、その上に正極活物質をエピタキシャル成長させることが可能である。なお、アルミ板等からなる基材８の厚さは、例えば０．１ｍｍ～５ｍｍのものを使用し、正極活物質層３は例えば１ｎｍ～５μｍのものを使用し、結晶欠陥修復層９は例えば１ｎｍ～０．１μｍのものを使用するのが好ましい。 For example, it is possible to form a nickel film as a crystal defect repair layer by sputtering or the like on an aluminum plate conventionally used as a current collector, and to epitaxially grow a positive electrode active material thereon. The base material 8 made of an aluminum plate or the like has a thickness of, for example, 0.1 mm to 5 mm, the positive electrode active material layer 3 has a thickness of, for example, 1 nm to 5 μm, and the crystal defect repair layer 9 has, for example, It is preferable to use one having a thickness of 1 nm to 0.1 μm.
　図１０は、実施の形態１、２の正極１が適用されるリチウムイオン二次電池の構成例を示す部分断面図である。リチウムイオン二次電池１００（以下、単に「電池１００」と記載する。）は、シート状の正極１を、負極１０、正極１及び負極１０の間に介在し、短絡を防止するセパレータ１１と積層し、芯材（図示せず）に捲回した捲回体を備え、電池缶１２にリチウム塩を含む非水電解液（図示せず）とともに封入したものである。電池１００は円筒形状であるが、角型、ラミネート型等とすることができ、また正負極及びセパレータを積層した積層型電極群を用いてもよい。 FIG. 10 is a partial cross-sectional view showing a configuration example of a lithium ion secondary battery to which the positive electrode 1 of the first and second embodiments is applied. A lithium ion secondary battery 100 (hereinafter, simply referred to as “battery 100”) includes a sheet-like positive electrode 1 interposed between a negative electrode 10, a positive electrode 1, and a negative electrode 10 and a separator 11 that prevents a short circuit. In addition, a wound body wound around a core material (not shown) is provided, and the battery can 12 is sealed together with a non-aqueous electrolyte solution (not shown) containing a lithium salt. The battery 100 has a cylindrical shape, but may be a square shape, a laminate type, or the like, or a stacked electrode group in which positive and negative electrodes and a separator are stacked may be used.
　正極１は、実施の形態１、２の構成を備える。負極１０は、リチウムイオンを吸蔵放出可能なものを適宜使用でき、セパレータ１１並びに非水電解液及びリチウム塩としては、従来より提案されている任意のものを用いることができるため、それらの詳細な説明は省略する。 The positive electrode 1 has the configuration of the first and second embodiments. As the negative electrode 10, a material capable of occluding and releasing lithium ions can be used as appropriate. As the separator 11, the nonaqueous electrolytic solution and the lithium salt, any conventionally proposed materials can be used. Description is omitted.
　電池１００は電池缶１２と、正極板リード片１３と、負極リード片１４と、密閉蓋部１５と、絶縁板１６と、パッキン１７とを備える。電池缶１２及び密閉蓋部１５は、例えばステンレス鋼（ＳＵＳ）等で構成される。正極板リード片１３は、正極１と密閉蓋部１５とを電気的に接続する。これにより、電池蓋部１５が電池１００の正極として機能する。また、負極リード片１４は、負極１０と電池缶１２の底部とを電気的に接続する。これにより、電池缶１２本体（具体的には電池缶１２の底部）が電池１００の負極として機能する。なお、電池缶１２と密閉蓋部１５とは、パッキン１７により電気的に絶縁されている。 The battery 100 includes a battery can 12, a positive electrode plate lead piece 13, a negative electrode lead piece 14, a sealing lid 15, an insulating plate 16, and a packing 17. The battery can 12 and the sealing lid 15 are made of, for example, stainless steel (SUS). The positive electrode plate lead piece 13 electrically connects the positive electrode 1 and the sealing lid portion 15. Thereby, the battery cover 15 functions as a positive electrode of the battery 100. The negative electrode lead piece 14 electrically connects the negative electrode 10 and the bottom of the battery can 12. Thereby, the battery can 12 main body (specifically, the bottom of the battery can 12) functions as the negative electrode of the battery 100. The battery can 12 and the sealing lid portion 15 are electrically insulated by a packing 17.
　上記構成により、電池１００は、可逆的に充放電可能であって、本発明の正極を用いることによりリチウムを高濃度に吸蔵することが可能となるため、高容量なリチウムイオン二次電池となる。 With the above structure, the battery 100 can be reversibly charged and discharged, and by using the positive electrode of the present invention, it is possible to occlude lithium at a high concentration, so that a high-capacity lithium ion secondary battery is obtained. .
　本発明によれば、層状固溶体化合物におけるリチウムの移動を円滑化し、性能、信頼性の高いリチウムイオン電池を提供でき、民生用機器等の小型の充電池だけではなく、電気自動車、ハイブリッド車、工具用の電池など、大型・長寿命が必要とされるリチウムイオン二次電池に幅広く利用することができる。 According to the present invention, lithium migration in a layered solid solution compound can be facilitated, and a lithium ion battery having high performance and reliability can be provided. Not only small rechargeable batteries such as consumer devices but also electric vehicles, hybrid vehicles, tools It can be widely used for lithium ion secondary batteries that require a large size and a long life.
１・・・正極
２・・・金属板
３・・・正極活物質層
４・・・リチウム元素
５・・・リチウム層
６、７・・・酸素原子
８・・・基材
９・・・結晶欠陥修復層
１０・・・負極
１１・・・セパレータ
１２・・・電池缶
１３・・・正極板リード片
１４・・・負極リード片
１５・・・密閉蓋部
１６・・・絶縁板 
１７・・・パッキン  DESCRIPTION OF SYMBOLS 1 ... Positive electrode 2 ... Metal plate 3 ... Positive electrode active material layer 4 ... Lithium element 5 ... Lithium layer 6, 7 ... Oxygen atom 8 ... Base material 9 ... Crystal Defect repair layer 10 ... Negative electrode 11 ... Separator 12 ... Battery can 13 ... Positive electrode plate lead piece 14 ... Negative electrode lead piece 15 ... Sealing lid 16 ... Insulating plate
17 ... packing

Claims (11)

  1. 　リチウムイオンを吸蔵放出可能な正極及び負極を備えるリチウムイオン二次電池において、
    　前記正極は、金属板と、前記金属板上にエピタキシャル成長させた正極活物質とを備え、
    　前記正極活物質は、ＬｉｘＮｉａＭｎｂＭｃＯ２+ｙ（ａ＋ｂ＋ｃ＝０．８、０．９５≦ｘ≦１．２）で表わされるリチウム遷移金属酸化物であり、
    　前記金属板は、前記正極活物質が固定された表面部に面心立方構造の（１１０）配向部分を有し、
    　前記金属板の少なくとも表面部を構成する金属材料の最近接原子間距離の理論値は、前記正極活物質の最近接原子間距離の理論値の８７～８９％であることを特徴とするリチウムイオン二次電池。     In a lithium ion secondary battery comprising a positive electrode and a negative electrode capable of occluding and releasing lithium ions,
    The positive electrode includes a metal plate and a positive electrode active material epitaxially grown on the metal plate,
    The positive electrode active material is a lithium transition metal oxide represented by LixNiaMnbMcO2 + y (a + b + c = 0.8, 0.95 ≦ x ≦ 1.2),
    The metal plate has a (110) orientation portion having a face-centered cubic structure on a surface portion to which the positive electrode active material is fixed,
    Lithium ions characterized in that the theoretical value of the closest interatomic distance of the metal material constituting at least the surface portion of the metal plate is 87 to 89% of the theoretical value of the closest interatomic distance of the positive electrode active material Secondary battery.
  2. 　リチウムイオンを吸蔵放出可能な正極及び負極を備えるリチウムイオン二次電池において、
    　前記正極は、金属板と、前記金属板上にエピタキシャル成長させた正極活物質とを備え、
    　前記正極活物質は、ＬｉｘＮｉａＭｎｂＭｃＯ２+ｙ（ａ＋ｂ＋ｃ＝０．８、０．９５≦ｘ≦１．２）で表わされるリチウム遷移金属酸化物であり、
    　前記金属板は、前記正極活物質が固定された表面部に面心立方構造の（１１０）配向部分を有し、
    　前記金属板の少なくとも表面部は、ニッケルまたはコバルトニッケル合金よりなる金属材料で構成されていることを特徴とするリチウムイオン二次電池。     In a lithium ion secondary battery comprising a positive electrode and a negative electrode capable of occluding and releasing lithium ions,
    The positive electrode includes a metal plate and a positive electrode active material epitaxially grown on the metal plate,
    The positive electrode active material is a lithium transition metal oxide represented by LixNiaMnbMcO2 + y (a + b + c = 0.8, 0.95 ≦ x ≦ 1.2),
    The metal plate has a (110) orientation portion having a face-centered cubic structure on a surface portion to which the positive electrode active material is fixed,
    At least a surface portion of the metal plate is made of a metal material made of nickel or a cobalt nickel alloy.
  3. 　請求項１または２に記載されたリチウムイオン二次電池において、
    　前記正極活物質の原子密度最密結晶面が前記金属板に対して垂直方向であることを特徴とするリチウムイオン二次電池。     The lithium ion secondary battery according to claim 1 or 2,
    The lithium ion secondary battery, wherein an atomic density close-packed crystal plane of the positive electrode active material is perpendicular to the metal plate.
  4. 　請求項１ないし３のいずれかに記載されたリチウムイオン二次電池において、
    　前記正極活物質の最近接酸素原子間距離の理論値が０．２８１ｎｍ以上０．２８８ｎｍ以下であり、前記金属材料は、最近接原子間距離の理論値が０．２４４ｎｍ以上０．２５３ｎｍ以下であることを特徴とするリチウムイオン二次電池。     The lithium ion secondary battery according to any one of claims 1 to 3,
    The theoretical value of the distance between nearest oxygen atoms of the positive electrode active material is 0.281 nm or more and 0.288 nm or less, and the metal material has a theoretical value of distance between nearest atoms of 0.244 nm or more and 0.253 nm or less. The lithium ion secondary battery characterized by the above-mentioned.
  5. 　請求項１ないし４のいずれかに記載されたリチウムイオン二次電池において、
    　前記金属板は、ニッケルまたはコバルトニッケル合金よりなることを特徴とするリチウムイオン二次電池。     The lithium ion secondary battery according to any one of claims 1 to 4,
    The lithium metal secondary battery, wherein the metal plate is made of nickel or a cobalt nickel alloy.
  6. 　請求項１ないし４のいずれかに記載されたリチウムイオン二次電池において、
    　前記金属板は、基材と、前記基材の表面に設けられたニッケル層またはコバルトニッケル合金層とを備えることを特徴とするリチウムイオン二次電池。     The lithium ion secondary battery according to any one of claims 1 to 4,
    The said metal plate is equipped with a base material and the nickel layer or cobalt nickel alloy layer provided in the surface of the said base material, The lithium ion secondary battery characterized by the above-mentioned.
  7. 　請求項６に記載されたリチウムイオン二次電池において、
    　前記基材は、導電性を備えることを特徴とするリチウムイオン二次電池。     In the lithium ion secondary battery according to claim 6,
    The said base material is provided with electroconductivity, The lithium ion secondary battery characterized by the above-mentioned.
  8. 　請求項１ないし７のいずれかに記載されたリチウムイオン二次電池において、
    　前記金属材料の最近接原子間距離の理論値は、前記正極活物質の最近接原子間距離の理論値の８７～８８％であることを特徴とするリチウムイオン二次電池。     The lithium ion secondary battery according to any one of claims 1 to 7,
    The lithium ion secondary battery, wherein the theoretical value of the distance between nearest atoms of the metal material is 87 to 88% of the theoretical value of the distance between nearest atoms of the positive electrode active material.
  9. 　リチウムイオンを吸蔵放出するリチウムイオン二次電池用の正極であって、
    　前記正極は、金属板と、前記金属板上にエピタキシャル成長させた正極活物質とを備え、
    　前記正極活物質は、ＬｉｘＮｉａＭｎｂＭｃＯ２+ｙ（ａ＋ｂ＋ｃ＝０．８、０．９５≦ｘ≦１．２）で表わされるリチウム遷移金属酸化物であり、
    　前記金属板は、前記正極活物質が固定された表面部に面心立方構造の（１１０）配向部分を有し、
    　前記金属板の少なくとも表面部を構成する金属材料の最近接原子間距離の理論値は、前記正極活物質の最近接原子間距離の理論値の８７～８９％であること、を特徴とするリチウムイオン二次電池用正極。     A positive electrode for a lithium ion secondary battery that occludes and releases lithium ions,
    The positive electrode includes a metal plate and a positive electrode active material epitaxially grown on the metal plate,
    The positive electrode active material is a lithium transition metal oxide represented by LixNiaMnbMcO2 + y (a + b + c = 0.8, 0.95 ≦ x ≦ 1.2),
    The metal plate has a (110) orientation portion having a face-centered cubic structure on a surface portion to which the positive electrode active material is fixed,
    The theoretical value of the distance between the nearest atoms of the metal material constituting at least the surface portion of the metal plate is 87 to 89% of the theoretical value of the distance between the nearest atoms of the positive electrode active material. Positive electrode for ion secondary battery.
  10. 　請求項９に記載されたリチウムイオン二次電池において、
    　前記金属材料は、ニッケルまたはコバルトニッケル合金よりなること、を特徴とするリチウムイオン二次電池用正極。     In the lithium ion secondary battery according to claim 9,
    The positive electrode for a lithium ion secondary battery, wherein the metal material is made of nickel or a cobalt nickel alloy.
  11. 　リチウムイオンを吸蔵放出するリチウムイオン二次電池用の正極であって、
    　前記正極は、金属板と、前記金属板上にエピタキシャル成長させた正極活物質とを備え、
    　前記正極活物質は、ＬｉｘＮｉａＭｎｂＭｃＯ２+ｙ（ａ＋ｂ＋ｃ＝０．８、０．９５≦ｘ≦１．２）で表わされるリチウム遷移金属酸化物であり、
    　前記金属板は、前記正極活物質が固定された表面部に面心立方構造の（１１０）配向部分を有し、
    　前記金属板の少なくとも表面部は、ニッケルまたはコバルトニッケル合金よりなる金属材料で構成されていることを特徴とするリチウムイオン二次電池用正極。     A positive electrode for a lithium ion secondary battery that occludes and releases lithium ions,
    The positive electrode includes a metal plate and a positive electrode active material epitaxially grown on the metal plate,
    The positive electrode active material is a lithium transition metal oxide represented by LixNiaMnbMcO2 + y (a + b + c = 0.8, 0.95 ≦ x ≦ 1.2),
    The metal plate has a (110) orientation portion having a face-centered cubic structure on a surface portion to which the positive electrode active material is fixed,
    A positive electrode for a lithium ion secondary battery, wherein at least a surface portion of the metal plate is made of a metal material made of nickel or a cobalt nickel alloy.
PCT/JP2014/050268 2014-01-10 2014-01-10 Lithium ion secondary battery positive electrode and lithium ion secondary battery WO2015104824A1 (en)

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Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2009295514A (en) * 2008-06-06 2009-12-17 Toyota Motor Corp Lithium ion secondary battery and method of manufacturing the same
JP2012129102A (en) * 2010-12-16 2012-07-05 Toyota Motor Corp Lithium secondary battery
WO2013065096A1 (en) * 2011-10-31 2013-05-10 株式会社日立製作所 Lithium ion secondary battery

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2009295514A (en) * 2008-06-06 2009-12-17 Toyota Motor Corp Lithium ion secondary battery and method of manufacturing the same
JP2012129102A (en) * 2010-12-16 2012-07-05 Toyota Motor Corp Lithium secondary battery
WO2013065096A1 (en) * 2011-10-31 2013-05-10 株式会社日立製作所 Lithium ion secondary battery

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