WO2015045719A1 - Électrode positive pour batteries secondaires ion-lithium en pile - Google Patents

Électrode positive pour batteries secondaires ion-lithium en pile Download PDF

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Publication number
WO2015045719A1
WO2015045719A1 PCT/JP2014/072542 JP2014072542W WO2015045719A1 WO 2015045719 A1 WO2015045719 A1 WO 2015045719A1 JP 2014072542 W JP2014072542 W JP 2014072542W WO 2015045719 A1 WO2015045719 A1 WO 2015045719A1
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Prior art keywords
positive electrode
active material
electrode active
material particles
ion secondary
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PCT/JP2014/072542
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English (en)
Japanese (ja)
Inventor
由美 斎藤
林　朋彦
公良 深津
智行 太田
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Ｎｅｃエナジーデバイス株式会社
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Publication of WO2015045719A1 publication Critical patent/WO2015045719A1/fr

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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
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/058—Construction or manufacture
    • H01M10/0585—Construction or manufacture of accumulators having only flat construction elements, i.e. flat positive electrodes, flat negative electrodes and flat separators
    • 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
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • 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
    • H01M4/04—Processes of manufacture in general
    • H01M4/043—Processes of manufacture in general involving compressing or compaction
    • 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
    • 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
    • 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
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
    • Y02P70/50—Manufacturing or production processes characterised by the final manufactured product

Definitions

  • This embodiment relates to a positive electrode for a stacked lithium ion secondary battery.
  • a positive electrode for a stacked lithium ion secondary battery is produced, for example, by the following method. After applying the slurry containing the positive electrode active material particles on the metal foil, the slurry is dried by hot air or infrared rays to volatilize the solvent. Then, this is pressed with a roller, the positive electrode active material layer is compressed and densified. By narrowing the interval between the positive electrode active material particles by pressing, the positive electrode resistance value can be lowered, and a positive electrode that can be applied to a stacked lithium ion secondary battery can be produced.
  • the positive electrode active material layer is pressed at a high pressure in order to increase the density, but the positive electrode active material particles are ruptured by contact between the positive electrode active material particles and the roller, or contact between the positive electrode active material particles.
  • the above force is applied, and cracks may occur in some of the positive electrode active material particles.
  • Patent Document 1 discloses that positive electrode active material particles composed of secondary particles formed by agglomeration of primary particles have cracks, thereby ensuring safety at the time of short-circuiting of the secondary battery. It is described that the elution of is facilitated to develop an internal short circuit safety mechanism.
  • the surface layer portion of the positive electrode active material particles has a larger distribution of metals (Mn, Al, Mg, Ca, Zr, B, W, Nb, Ta, In, Mo, and Sn) than the inside.
  • the metal oxide film is formed on the surface to ensure safety at the time of short circuit. Although metal elution is suppressed by this metal oxide film at the time of a short circuit, elution of metal is facilitated by providing a crack.
  • Patent Document 2 discloses a method for producing positive electrode active material particles made of a nickel-alkali metal-containing composite oxide having cracks on the surface of the primary particles and a secondary battery to which the positive electrode active material particles are applied. By providing cracks in the positive electrode active material particles, volume change of the positive electrode active material particles due to Li in and out of the positive electrode active material particles in the charge / discharge cycle is suppressed, and a decrease in capacity in the charge / discharge cycle is prevented.
  • Patent Documents 1 and 2 both state that cracks in the positive electrode active material particles are effective for promoting metal elution with respect to overcharge and suppressing volume expansion of the positive electrode active material particles accompanying the charge / discharge cycle.
  • the present inventors recognize that cracks in the positive electrode active material particles reduce the long-term reliability of the lithium ion secondary battery.
  • the surface of the positive electrode active material particles is coated with an oxide layer in order to prevent elution of metal elements.
  • the positive electrode active material particles have cracks, the inner surface of the positive electrode active material particles without coating is exposed, and the amount of elution of the metal elements constituting the positive electrode active material particles is reduced when the secondary battery is used for a long time.
  • OH ions are desorbed from the alkali metal component contained in the positive electrode active material particles, and dissolved in the non-aqueous electrolyte solution to become moisture.
  • the present inventors in order to increase the density of the positive electrode active material layer for the purpose of reducing the impedance of the positive electrode for use in a stacked lithium ion secondary battery, the present inventors, for example, It has been experimentally confirmed that it is necessary to press the material particles at such a pressure as to cause cracks.
  • the frequency of occurrence of cracks in the positive electrode active material particles due to the pressing process tends to vary depending on the position in the thickness direction of the positive electrode active material layer.
  • the frequency of occurrence of cracks in the positive electrode active material particles is higher than that in the positive electrode active material layer. This can be confirmed by observing the surface and cross section of the positive electrode active material layer by SEM (Scanning Electron Microscope).
  • the positive electrode active material layer there is a gap between the positive electrode active material particles before the pressing step, and the positive electrode active material particles move due to the press pressure.
  • the positive electrode active material particles present on the surface of the positive electrode active material layer come into contact with the roller in the pressing step, the movement of the positive electrode active material particles is restricted, and the positive electrode active material particles are directly pressed.
  • the surface of the roller is made of metal, and the breaking strength of the positive electrode active material particles is lower than the breaking strength of the metal.
  • the positive electrode active material layer surface before the pressing process has irregularities due to individual positive electrode active material particles, and the positive electrode active material particles protruding in a convex shape are locally subjected to a high pressing pressure and cracks are generated. easy.
  • An object of the present embodiment is to provide a positive electrode for a laminated lithium ion secondary battery having high long-term reliability when a laminated lithium ion secondary battery is manufactured.
  • the positive electrode for a stacked lithium ion secondary battery is a positive electrode for a stacked lithium ion secondary battery that includes a stacked body in which a plurality of positive electrodes and negative electrodes facing each other with a nonaqueous electrolyte and a separator interposed therebetween.
  • the positive electrode comprises a positive electrode active material layer containing positive electrode active material particles, Of the positive electrode active material particles present on the outermost surface of the positive electrode active material layer, the proportion of the positive electrode active material particles having cracks is 20% or less.
  • the multilayer lithium ion secondary battery according to this embodiment includes the positive electrode for the multilayer lithium ion secondary battery.
  • the method for producing a laminated lithium ion secondary battery according to this embodiment includes a positive electrode for a laminated lithium ion secondary battery that includes a laminate in which a plurality of positive electrodes and negative electrodes facing each other with a nonaqueous electrolyte and a separator interposed therebetween.
  • the present embodiment it is possible to provide a positive electrode for a stacked lithium ion secondary battery that has high long-term reliability when a stacked lithium ion secondary battery is manufactured.
  • LiOH LiOH that is used to form lithium metal oxide in the production process of the positive electrode active material particles, and if there are cracks in the positive electrode active material particles, OH ions are likely to be dissociated from the LiOH. , OH ion desorption increases.
  • the positive electrode active material particles are secondary particles formed by agglomeration of primary particles, the primary particles are dispersed by the pressing process, and the amount of desorption of OH ions existing inside the secondary particles is reduced.
  • the OH ions become moisture and dissolve in the non-aqueous electrolyte.
  • OH ions become moisture (H 2 O) by the following reaction, for example. Thereby, the moisture content inside the secondary battery increases.
  • the present inventors detect the moisture content measurement (300 ° C.) by the Karl Fischer method of the positive electrode after the pressing process compared to before the pressing process. It has been confirmed that the amount of water to be increased. It has also been confirmed that when the press pressure is changed to increase the frequency of occurrence of cracks in the positive electrode active material particles, the amount of water detected by the water content measurement by the Karl Fischer method of the positive electrode increases.
  • the surface area of the positive electrode active material particles increases and the moisture adsorption sites increase.
  • the positive electrode active material particles are secondary particles formed by agglomeration of primary particles
  • the surface area of the positive electrode active material particles greatly increases when the primary particles are dispersed by the pressing process.
  • the moisture adsorption amount increases when the positive electrode is exposed to the atmosphere when storing the positive electrode.
  • the present inventors have measured the moisture content by the Karl Fischer method of the positive electrode when the positive electrode is left in the atmosphere as compared to the case where no crack is generated ( It has been confirmed that the amount of water detected at 300 ° C. increases.
  • Cracks in the positive electrode active material particles may occur on the surface and inside the positive electrode active material layer.
  • the positive electrode active material particles present on the outermost surface of the positive electrode active material layer have cracks, two cracks are caused by the positive electrode. The contribution to the increase in water content in the secondary battery is large.
  • the positive electrode for a stacked lithium ion secondary battery is a positive electrode for a stacked lithium ion secondary battery that includes a stacked body in which a plurality of positive electrodes and negative electrodes facing each other with a nonaqueous electrolyte and a separator interposed therebetween.
  • the positive electrode includes a positive electrode active material layer containing positive electrode active material particles, and among the positive electrode active material particles present on the outermost surface of the positive electrode active material layer, a ratio of the positive electrode active material particles having cracks is 20 % Or less.
  • the following effects are acquired when the ratio of the positive electrode active material particle which has a crack among the positive electrode active material particles which exist in the outermost surface of a positive electrode active material layer is 20% or less.
  • the 1st effect can suppress generation
  • the second effect is that even when the positive electrode is left in the air, the amount of water adsorbed on the positive electrode active material particles can be reduced. Since the ratio of the positive electrode active material particles having cracks is low, the entire surface area of the positive electrode active material particles is small, and there are few external moisture adsorption sites. Thereby, the amount of moisture adsorbed by the positive electrode active material particles is reduced.
  • the positive electrode active material particles present on the outermost surface of the positive electrode active material layer have cracks
  • the positive electrode active material particles are exposed to the atmosphere and have a large amount of moisture adsorption.
  • the contribution to the increase in water content in the secondary battery is large.
  • the proportion of the positive electrode active material particles present on the outermost surface of the positive electrode active material layer having cracks is 20% or less, so that the amount of water inside the secondary battery can be significantly reduced.
  • the positive electrode active material particles present inside the positive electrode active material layer are also exposed to the atmosphere, but due to adhesion of the binder around the positive electrode active material particles, contact with other positive electrode active material particles, Compared with the positive electrode active material particles present on the outermost surface, the contact area with the atmosphere is small. In addition, since the gap between the positive electrode active material particles in the positive electrode active material layer is narrow, the air entering the positive electrode active material layer is stagnant compared to the surface of the positive electrode active material layer.
  • the amount of moisture supplied from the atmosphere to the positive electrode active material particles is small, and the increase in the amount of water due to the cracks in the positive electrode active material particles present inside the positive electrode active material layer is This is less than the increase in the amount of water due to the positive electrode active material particles present on the outermost surface having cracks.
  • the proportion of the positive electrode active material particles present on the outermost surface of the positive electrode active material layer having cracks is 20% or less, so that the amount of water in the positive electrode is effectively reduced, and the long-term performance of the secondary battery is increased. Reliability can be improved.
  • FIG. 1 An example of a positive electrode for a stacked lithium ion secondary battery according to the present embodiment is shown in FIG.
  • the positive electrode shown in FIG. 1 includes a positive electrode current collector 1 and a positive electrode active material layer 2 formed on the positive electrode current collector 1.
  • the positive electrode active material particles present on the outermost surface of the positive electrode active material layer 2 are positive electrode active material particles 3 having no cracks.
  • the positive electrode active material particles present inside the positive electrode active material layer 2 include positive electrode active material particles 3 having no cracks and positive electrode active material particles 4 having cracks.
  • “positive electrode active material particles present on the outermost surface of the positive electrode active material layer” means positive electrode active material particles that can be observed when the positive electrode surface is observed at 2500 times with an electron microscope. Show.
  • the “positive electrode active material particles present inside the positive electrode active material layer” refers to positive electrode active material particles other than the “positive electrode active material particles present on the outermost surface of the positive electrode active material layer”. Further, in this embodiment, “having cracks” indicates a state in which one or more cracks have entered at least a part of the positive electrode active material particles. When the positive electrode active material particles are secondary particles formed by aggregation of primary particles, “having cracks” indicates that the primary particles are separated from each other and that the primary particles themselves have cracks. On the other hand, when the positive electrode active material particles are formed of primary particles, “having cracks” means that the primary particles themselves have cracks.
  • the positive electrode active material particle which exists in the positive electrode active material layer 2 of the positive electrode shown by FIG. 1 contains the positive electrode active material particle 4 which has a crack
  • the positive electrode active material particles present inside the layer 2 may not include the positive electrode active material particles 4 having cracks.
  • the proportion of the positive electrode active material particles having cracks is 20% or less.
  • the ratio is more preferably 15% or less, further preferably 10% or less, and particularly preferably 5% or less.
  • the ratio is preferably small, and may be 0%.
  • the positive electrode active material particles are pressed with a pressure at which cracks are generated in some positive electrode active material particles present on the outermost surface due to contact between the positive electrode active material particles. It is technically difficult to devise a pressing process so that cracks due to collision between the positive electrode active material particles do not occur at all while narrowing the interval between the positive electrode active material particles.
  • the ratio of the positive electrode active material particles having cracks among the positive electrode active material particles present on the outermost surface of the positive electrode active material layer is a value measured by the following method.
  • the surface of the positive electrode is observed with an electron microscope at 2500 times, and the total number of positive electrode active material particles and the number of positive electrode active material particles with cracks are determined with respect to the positive electrode active material particles present in a region of 48 ⁇ m ⁇ 36 ⁇ m. Count and calculate the ratio.
  • the positive electrode active material layer is formed, for example, by applying a slurry containing positive electrode active material particles on a metal foil, which is a positive electrode current collector, and drying, followed by pressing. A specific forming method will be described later.
  • the positive active material particles are Li x Mn 2 + y M1 z O 4 + ⁇ (M1 is selected from the group consisting of B, Sn, Al, Ti, V, Cr, Fe, Co, Ni, Cu, Zn, Mg and Ga) 1 ⁇ x ⁇ 1.5, ⁇ 1 ⁇ y ⁇ 0, 0 ⁇ z ⁇ 0.5, ⁇ 0.1 ⁇ ⁇ ⁇ 0.1), and Li p Ni 2 ⁇ Including at least one of q O 2 + ⁇ (0 ⁇ p ⁇ 1, 0 ⁇ q ⁇ 1, ⁇ 0.1 ⁇ ⁇ 0.1) is preferable from the viewpoint of improving the capacity retention rate.
  • x is preferably 1 ⁇ x ⁇ 1.3, and more preferably 1 ⁇ x ⁇ 1.2.
  • y is preferably ⁇ 0.5 ⁇ y ⁇ 0, and more preferably ⁇ 0.3 ⁇ y ⁇ 0.
  • z is preferably 0 ⁇ z ⁇ 0.3, and more preferably 0 ⁇ z ⁇ 0.2.
  • ⁇ is preferably ⁇ 0.07 ⁇ ⁇ ⁇ 0.07, and more preferably ⁇ 0.05 ⁇ ⁇ ⁇ 0.05.
  • p is preferably 0.03 ⁇ p ⁇ 1, and more preferably 0.05 ⁇ p ⁇ 1.
  • q is preferably 0.03 ⁇ q ⁇ 1, and more preferably 0.05 ⁇ q ⁇ 1.
  • ⁇ is preferably ⁇ 0.07 ⁇ ⁇ ⁇ 0.07, and more preferably ⁇ 0.05 ⁇ ⁇ ⁇ 0.05.
  • the positive electrode active material particles preferably include the Li x Mn 2 + y M1 z O 4 + ⁇ and the Li p Ni 2 -q O 2 + ⁇ from the viewpoint of improving the capacity retention rate.
  • contained in the positive electrode active material particles Li x Mn 2 + y M1 z O 4 + ⁇ and the Li p Ni 2-q ratio of the O 2 + ⁇ (Li x Mn 2 + y M1 z O 4 + ⁇ : Li p Ni 2-q O 2 + ⁇ ) is Although not particularly limited, the mass ratio is preferably 9: 1 to 6: 4.
  • Some of the positive electrode active material particles present in the positive electrode active material layer may have cracks.
  • the crack of the positive electrode active material particles existing on the outermost surface of the positive electrode active material layer contributes greatly to the increase in the amount of moisture, the crack of the positive electrode active material particles existing on the outermost surface of the positive electrode active material layer is reduced.
  • the existing ratio is 20% or less.
  • the positive electrode active material particles are brought into contact with each other inside the positive electrode active material layer by the press pressure, and the pressure is applied to each other. Such positive electrode active material particles may crack.
  • the positive electrode active material particles present inside the positive electrode active material layer may have cracks.
  • the present embodiment includes a case where the positive electrode active material particles present in the positive electrode active material layer have no cracks.
  • the positive electrode active material particles In order to suppress an increase in the amount of water inside the secondary battery, it is most effective that the positive electrode active material particles have no cracks in the entire positive electrode active material layer.
  • it is required to increase the density of the positive electrode active material layer and reduce the electrode resistance without generating cracks in the positive electrode active material particles. For example, there are a method in which the press pressure is increased stepwise, a method in which heat is applied and the positive electrode active material layer before pressing is softened, and the like is technically difficult.
  • the method for producing a positive electrode for a laminated lithium ion secondary battery according to this embodiment is for a laminated lithium ion secondary battery comprising a laminate in which a plurality of positive electrodes and negative electrodes facing each other with a nonaqueous electrolyte and a separator interposed therebetween are laminated.
  • a method for producing a positive electrode comprising: forming a positive electrode active material layer by pressing a slurry containing positive electrode active material particles on a metal foil as a positive electrode current collector; Of the positive electrode active material particles present on the outermost surface of the positive electrode active material layer, the proportion of the positive electrode active material particles having cracks is 20% or less.
  • the positive electrode for the laminated lithium ion secondary battery according to the present embodiment can be suitably manufactured.
  • the method according to the present embodiment includes a step of forming a positive electrode active material layer by applying a slurry containing positive electrode active material particles on a metal foil, which is a positive electrode current collector, and drying, followed by pressing.
  • An aluminum foil or the like can be used as the metal foil that is the positive electrode current collector.
  • the slurry containing the positive electrode active material particles can be prepared, for example, by adding the positive electrode active material particles, the conductive auxiliary agent, and the binder to a solvent and mixing them. Carbon black or the like can be used as the conductive auxiliary agent.
  • As the binder polyvinylidene fluoride (PVDF) or the like can be used.
  • As the solvent N-methyl-2-pyrrolidone (NMP) or the like can be used.
  • the thickness of the slurry applied on the metal foil can be set to 100 to 120 ⁇ m, for example.
  • the drying method is not particularly limited, and for example, it can be dried with hot air.
  • the press can be pressed using, for example, a roller press.
  • the pressure at the time of pressing depends on the density of the target positive electrode active material layer, but can be, for example, 100 to 300 MPa.
  • the thickness of the positive electrode active material layer after pressing can be, for example, 70 to 80 ⁇ m.
  • the density of the positive electrode active material layer after pressing is preferably 2.5 to 3.5 g / ml. The density can be adjusted by changing the gap length of the roller for pressing.
  • the application, drying, and pressing of the slurry may be performed on one side of the metal foil that is the positive electrode current collector, or may be performed on both sides.
  • two or more positive electrode active material layers may be formed by performing application, drying, and pressing of the slurry twice or more on one side or both sides of the metal foil.
  • another slurry may be further applied without drying, and then drying and pressing may be performed.
  • the step of forming the positive electrode active material layer is a step shown below from the viewpoint of setting the ratio of positive electrode active material particles having cracks to 20% or less of the positive electrode active material particles present on the outermost surface of the positive electrode active material layer. It is preferable that
  • the positive electrode active material layer in the step of forming the positive electrode active material layer, it is preferable to perform pressing using a roller made of a material having a lower elastic modulus than the positive electrode active material particles.
  • a material having a lower elastic modulus than the positive electrode active material particles as the material of at least the roller surface, that is, the roller surface that is in contact with the surface of the positive electrode active material layer, the positive electrode active material layer has a lower modulus than the positive electrode active material layer surface. The pressure to the inside increases and the collapse of the positive electrode active material particles is suppressed on the outermost surface of the positive electrode active material layer.
  • the pressure inside the positive electrode active material layer becomes high, and cracks may occur in the positive electrode active material particles existing inside the positive electrode active material layer.
  • the positive electrode active material particles include the Li x Mn 2 + y M1 z O 4 + ⁇ and the Li p Ni 2 -q O 2 + ⁇
  • an acrylic resin, rubber, or the like can be used as the material of the roller.
  • the elastic modulus is a value measured by a tensile test.
  • the step of forming the positive electrode active material layer after applying a slurry containing the first positive electrode active material particles on the metal foil that is the positive electrode current collector, it is preferable that a slurry containing second positive electrode active material particles having an average particle diameter smaller than that of the positive electrode active material particles is further applied, dried, and then pressed.
  • a slurry containing second positive electrode active material particles having an average particle diameter smaller than that of the positive electrode active material particles is further applied, dried, and then pressed.
  • the average particle diameter of the positive electrode active material particles existing on the outermost surface of the positive electrode active material layer is small, the unevenness generated by the positive electrode active material particles on the surface of the positive electrode active material layer is small before the pressing step, and the positive electrode The surface of the active material layer is smooth.
  • the pressure applied from the roller to the positive electrode active material particles existing on the outermost surface of the positive electrode active material layer becomes uniform, and locally high pressure can be avoided from being applied to the individual positive electrode active material particles.
  • the generation of cracks is suppressed.
  • the average particle diameter of the first positive electrode active material particles can be 5 ⁇ m or more, and the average particle diameter of the second positive electrode active material particles can be 2 ⁇ m or less.
  • the thickness of the positive electrode active material layer after applying the slurry containing the first positive electrode active material particles was applied to the slurry containing the first positive electrode active material particles and the slurry containing the second positive electrode active material particles. It is preferably 80 to 90% of the thickness of the subsequent positive electrode active material layer.
  • the average particle diameter (D50) of the positive electrode active material particles is a median value obtained from a particle size distribution measured by a laser diffraction or scattering method. Also, a slurry containing the first positive electrode active material particles is applied onto the metal foil, dried, and a slurry containing the second positive electrode active material particles having an average particle diameter smaller than that of the first positive electrode active material particles is applied. It is also possible to press after drying. However, in this case, since the adhesion between the two layers is low, peeling may occur at the interface between the two layers.
  • the step of forming the positive electrode active material layer after applying a slurry containing the first positive electrode active material particles on the metal foil that is the positive electrode current collector, it is preferable that a slurry containing second positive electrode active material particles having a compressive strength larger than that of the positive electrode active material particles is further applied, dried, and then pressed. In this case, since the compressive strength of the positive electrode active material particles present on the outermost surface of the positive electrode active material layer is high, cracks are unlikely to occur in the positive electrode active material particles present on the outermost surface of the positive electrode active material in contact with the roller in the pressing step. .
  • the positive electrode active material particles having high compressive strength have a high density, the permeability of the electrolytic solution into the positive electrode active material particles is low, and the efficiency of Li ion entry / exit into the positive electrode active material particles may be reduced. is there.
  • the compressive strength of the positive electrode active material particles existing on the outermost surface of the positive electrode active material layer is increased, the influence is small.
  • the compressive strength of the first positive electrode active material particles can be 30 MPa or less, and the average particle diameter of the second positive electrode active material particles can be 40 MPa or more.
  • the compressive strength of the positive electrode active material particles is a value calculated from a value measured by a compression tester.
  • the stacked lithium ion secondary battery according to the present embodiment includes the positive electrode for the stacked lithium ion secondary battery according to the present embodiment.
  • the laminated lithium ion secondary battery according to the present embodiment is a laminate in which a plurality of laminated lithium ion secondary battery positive electrodes and negative electrodes according to the present embodiment are opposed to each other with a nonaqueous electrolyte and a separator interposed therebetween. Prepare the body.
  • non-aqueous electrolyte for example, EC (ethylene carbonate), DEC (diethylene carbonate), DMC (dimethylene carbonate) and the like can be used. These may use 1 type and may use 2 or more types together.
  • the non-aqueous electrolyte can contain a lithium salt such as LiPF 6 as a supporting salt.
  • a material for the separator for example, polypropylene or the like can be used.
  • a negative electrode having a negative electrode active material layer formed on a negative electrode current collector can be used.
  • the negative electrode current collector for example, a copper foil or the like can be used. Carbon or the like can be used as the negative electrode active material contained in the negative electrode active material layer.
  • the negative electrode can be obtained, for example, by forming a negative electrode active material layer containing a negative electrode active material and a binder on a negative electrode current collector.
  • the binder for example, polyvinylidene fluoride (PVDF) can be used.
  • a separator is disposed between the positive electrode for a laminated lithium ion secondary battery according to the present embodiment and the negative electrode, and a plurality of the separators are laminated to form a laminated body. Then, the laminate is inserted into the exterior body, a nonaqueous electrolytic solution containing a supporting salt is injected into the exterior body, and the exterior body is sealed under reduced pressure.
  • a laminate film can be used as the exterior body.
  • the moisture content of the positive electrode was measured at 300 ° C. by the Karl Fischer method.
  • the elastic modulus was measured by a tensile test.
  • the average particle diameter (D50) of the positive electrode active material particles was measured by laser diffraction and scattering methods.
  • the compressive strength of the positive electrode active material particles was measured with a compression tester.
  • the ratio of the positive electrode active material particles having cracks among the positive electrode active material particles present on the outermost surface of the positive electrode active material layer was measured by the following method.
  • the surface of the positive electrode produced by an electron microscope is observed at a magnification of 2500, and the total number of positive electrode active material particles and the number of positive electrode active material particles with cracks are present with respect to the positive electrode active material particles present in a 48 ⁇ m ⁇ 36 ⁇ m region. And the ratio was calculated.
  • PVDF polyvinylidene fluoride
  • NMP N-methyl-2-pyrrolidone
  • the slurry application and drying steps were performed twice on both sides of the positive electrode current collector.
  • the positive electrode active material layer formed on both surfaces of the positive electrode current collector was pressed by a roller press (pressing pressure: 200 MPa), the thickness of the positive electrode active material layer was 80 ⁇ m, and the positive electrode active material layer was densified. This obtained the positive electrode in a present Example.
  • An acrylic resin having a lower elastic modulus than that of the positive electrode active material particles was used as a material constituting the surface of the roller used in the press by the roller press in contact with the positive electrode active material layer.
  • the generation of cracks in the positive electrode active material particles present on the outermost surface of the positive electrode active material layer due to pressing is suppressed, and among the positive electrode active material particles present on the outermost surface of the positive electrode active material layer, positive electrode active material particles having cracks The percentage of was 19%.
  • the positive electrode active material layer has a pressure necessary for realizing high density inside, so that the positive electrode active material particles having the same mechanical strength are brought into contact with each other and compressed, and the positive electrode active material layer Cracks occurred in some of the positive electrode active material particles present in the interior of the glass.
  • a negative electrode active material layer containing a negative electrode active material mainly composed of carbon and PVDF as a binder was formed on a copper foil as a negative electrode current collector to obtain a negative electrode.
  • a separator made of polypropylene was disposed between the positive electrode and the negative electrode, and the negative electrode, the separator, and the unit layer of the positive electrode were laminated several times.
  • the obtained laminate was inserted into an exterior body made of a laminate film, and a solution of LiPF 6 as a supporting salt dissolved in a nonaqueous electrolytic solution made of EC (ethylene carbonate) and DEC (diethylene carbonate) was injected.
  • the inside of the body was sealed in a vacuum state.
  • a stacked lithium ion secondary battery in this example was obtained.
  • a slurry 1 was prepared in the same manner as in 1.
  • a slurry 2 was prepared in the same manner as in 1.
  • the positive electrode active material layer includes a first positive electrode active material layer 5 and a second positive electrode active material layer 6.
  • the steps of applying and drying the slurries 1 and 2 were also performed on the other surface of the positive electrode current collector.
  • the positive electrode active material layer formed on both surfaces of the positive electrode current collector was pressed by a roller press, so that the thickness of the positive electrode active material layer was 80 ⁇ m and the positive electrode active material layer was densified.
  • the average particle size of the second positive electrode active material particles present on the outermost surface of the positive electrode active material layer is larger than the average particle size of the first positive electrode active material particles present inside the positive electrode active material layer. Since it was small, the unevenness
  • a slurry 1 was prepared in the same manner as in 1.
  • a slurry 2 was prepared in the same manner as in Example 1.
  • a laminated lithium ion secondary battery including a positive electrode and the positive electrode was produced in the same manner as in Example 2 except that these slurries 1 and 2 were used.
  • the proportion of positive electrode active material particles having cracks was 19%.
  • the positive electrode active material particles present inside the positive electrode active material layer were cracked in part due to contact between the positive electrode active material particles during pressing.
  • Example 1 The same as in Example 1 except that a material having a higher elastic modulus than the positive electrode active material particles (SUS) is used as the material constituting the surface of the roller used in the press by the roller press in contact with the positive electrode active material layer.
  • a positive electrode was prepared.
  • the proportion of positive electrode active material particles having cracks was 40%.
  • the positive electrode active material particles present inside the positive electrode active material layer were cracked in part due to contact between the positive electrode active material particles during pressing.
  • a stacked lithium ion secondary battery was obtained in the same manner as in Example 1, and a charge / discharge cycle test was performed. The results are shown in Table 1.
  • the multilayer lithium ion secondary battery according to the present embodiment can be used for multilayer lithium ion secondary batteries that require long-term reliability because performance degradation in charge / discharge cycles is suppressed.

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  • Engineering & Computer Science (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Electrochemistry (AREA)
  • General Chemical & Material Sciences (AREA)
  • Manufacturing & Machinery (AREA)
  • Materials Engineering (AREA)
  • Inorganic Chemistry (AREA)
  • Battery Electrode And Active Subsutance (AREA)

Abstract

L'invention concerne une électrode positive pour batteries secondaires lithium-ion en pile qui permet la production d'une batterie secondaire lithium-ion en pile ayant une grande fiabilité à long terme. Une électrode positive pour batteries secondaires lithium-ion en pile selon l'invention, qui est utilisée pour une batterie secondaire lithium-ion en pile qui est dotée d'un stratifié obtenu par stratification de plusieurs électrodes positives et de plusieurs électrodes négatives se faisant respectivement face les unes aux autres, des séparateurs et une solution d'électrolyte non aqueux étant intercalés entre les électrodes. L'électrode positive est dotée d'une couche de matériau actif d'électrode positive contenant des particules de matériau actif d'électrode positive, et le rapport de particules de matériau actif d'électrode positive ayant une fissure parmi les particules de matériau actif d'électrode positive présent sur la surface la plus à l'extérieur de la couche de matériau actif d'électrode positive est inférieur ou égal à 20%.
PCT/JP2014/072542 2013-09-26 2014-08-28 Électrode positive pour batteries secondaires ion-lithium en pile WO2015045719A1 (fr)

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JP2019140054A (ja) * 2018-02-15 2019-08-22 Tdk株式会社 正極及び非水電解液二次電池
WO2020013324A1 (fr) * 2018-07-13 2020-01-16 株式会社村田製作所 Batterie secondaire à électrolyte non aqueux
CN110943255A (zh) * 2018-09-21 2020-03-31 丰田自动车株式会社 全固体电池的制造方法及全固体电池
CN115053368A (zh) * 2020-03-18 2022-09-13 株式会社Lg化学 锂二次电池用正极材料以及包含其的正极和锂二次电池
CN115053360A (zh) * 2020-01-31 2022-09-13 松下知识产权经营株式会社 二次电池用正极和二次电池
WO2023185743A1 (fr) * 2022-03-30 2023-10-05 华为技术有限公司 Plaque d'électrode, batterie rechargeable et dispositif terminal
CN117410584A (zh) * 2023-12-12 2024-01-16 中安芯界控股集团有限公司 一种高稳定性条板电池芯片的制备工艺

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WO2018016528A1 (fr) * 2016-07-20 2018-01-25 Ｎｅｃエナジーデバイス株式会社 Électrode pour batteries au lithium-ion, et batterie au lithium-ion
JP2019140054A (ja) * 2018-02-15 2019-08-22 Tdk株式会社 正極及び非水電解液二次電池
WO2020013324A1 (fr) * 2018-07-13 2020-01-16 株式会社村田製作所 Batterie secondaire à électrolyte non aqueux
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CN110943255A (zh) * 2018-09-21 2020-03-31 丰田自动车株式会社 全固体电池的制造方法及全固体电池
CN110943255B (zh) * 2018-09-21 2023-10-13 丰田自动车株式会社 全固体电池的制造方法及全固体电池
CN115053360B (zh) * 2020-01-31 2024-03-22 松下知识产权经营株式会社 二次电池用正极和二次电池
CN115053360A (zh) * 2020-01-31 2022-09-13 松下知识产权经营株式会社 二次电池用正极和二次电池
CN115053368A (zh) * 2020-03-18 2022-09-13 株式会社Lg化学 锂二次电池用正极材料以及包含其的正极和锂二次电池
CN115053368B (zh) * 2020-03-18 2023-12-19 株式会社Lg化学 锂二次电池用正极材料以及包含其的正极和锂二次电池
WO2023185743A1 (fr) * 2022-03-30 2023-10-05 华为技术有限公司 Plaque d'électrode, batterie rechargeable et dispositif terminal
CN117410584B (zh) * 2023-12-12 2024-02-23 中安芯界控股集团有限公司 一种高稳定性条板电池芯片的制备工艺
CN117410584A (zh) * 2023-12-12 2024-01-16 中安芯界控股集团有限公司 一种高稳定性条板电池芯片的制备工艺

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