WO2025243748A1 - Électrode positive d'élément de stockage d'énergie, corps d'électrode, élément de stockage d'énergie et dispositif de stockage d'énergie - Google Patents

Électrode positive d'élément de stockage d'énergie, corps d'électrode, élément de stockage d'énergie et dispositif de stockage d'énergie

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Publication number
WO2025243748A1
WO2025243748A1 PCT/JP2025/015270 JP2025015270W WO2025243748A1 WO 2025243748 A1 WO2025243748 A1 WO 2025243748A1 JP 2025015270 W JP2025015270 W JP 2025015270W WO 2025243748 A1 WO2025243748 A1 WO 2025243748A1
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WO
WIPO (PCT)
Prior art keywords
active material
positive electrode
material particles
electrode active
storage element
Prior art date
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Pending
Application number
PCT/JP2025/015270
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English (en)
Japanese (ja)
Inventor
瑞歩 中野
哲志 星野
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GS Yuasa International Ltd
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GS Yuasa International Ltd
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Filing date
Publication date
Application filed by GS Yuasa International Ltd filed Critical GS Yuasa International Ltd
Publication of WO2025243748A1 publication Critical patent/WO2025243748A1/fr
Pending legal-status Critical Current
Anticipated expiration legal-status Critical

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Classifications

    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES, LIGHT-SENSITIVE OR TEMPERATURE-SENSITIVE DEVICES OF THE ELECTROLYTIC TYPE
    • H01G11/00—Hybrid capacitors, i.e. capacitors having different positive and negative electrodes; Electric double-layer [EDL] capacitors; Processes for the manufacture thereof or of parts thereof
    • H01G11/22—Electrodes
    • H01G11/24—Electrodes characterised by structural features of the materials making up or comprised in the electrodes, e.g. form, surface area or porosity; characterised by the structural features of powders or particles used therefor
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES, LIGHT-SENSITIVE OR TEMPERATURE-SENSITIVE DEVICES OF THE ELECTROLYTIC TYPE
    • H01G11/00—Hybrid capacitors, i.e. capacitors having different positive and negative electrodes; Electric double-layer [EDL] capacitors; Processes for the manufacture thereof or of parts thereof
    • H01G11/22—Electrodes
    • H01G11/30—Electrodes characterised by their material
    • H01G11/46—Metal oxides
    • 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
    • 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
    • H01M4/136—Electrodes based on inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy
    • 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
    • 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 an energy storage element, an electrode body, an energy storage element, and an energy storage device.
  • Non-aqueous electrolyte secondary batteries typified by lithium-ion secondary batteries
  • Non-aqueous electrolyte secondary batteries are widely used in electronic devices such as personal computers and communication terminals, as well as automobiles, due to their high energy density.
  • Non-aqueous electrolyte secondary batteries generally have a pair of electrodes electrically isolated by a separator and a non-aqueous electrolyte sandwiched between the electrodes, and are configured to charge and discharge by transferring charge-carrying ions between the electrodes.
  • Capacitors other than non-aqueous electrolyte secondary batteries such as lithium-ion capacitors and electric double-layer capacitors, are also widely used as energy storage elements.
  • An example of an electrode for an energy storage element is one that has an active material layer obtained by applying a mixture containing active material particles to a metal foil, drying it, and then pressing it (Patent Document 1).
  • One way to improve adhesion is to increase both the hardness and particle size of the active material particles contained in the active material layer.
  • the present invention was made based on the above circumstances, and its purpose is to provide a positive electrode for an electric storage element that can reduce the resistance of the electric storage element and increase the electrode density, as well as an electrode body, electric storage element, and electric storage device that include such a positive electrode for an electric storage element.
  • a positive electrode for an energy storage device includes a substrate and a positive electrode active material layer laminated on the substrate and containing positive electrode active material particles, the positive electrode active material particles including first active material particles and second active material particles having different particle diameters, wherein in a particle size distribution diagram of the positive electrode active material particles with the horizontal axis representing particle diameter [ ⁇ m] and the vertical axis representing volume-based frequency [%], the first active material particles exhibit a first peak particle diameter of 4.0 ⁇ m or more and the second active material particles exhibit a second peak particle diameter smaller than the first peak particle diameter, the first active material particles have a breaking strength of 20.0 MPa or more, the ratio of the frequency [%] of the first peak particle diameter to the frequency [%] of the second peak particle diameter in the particle size distribution diagram is 1.0 or more and 4.3 or less, and the positive electrode active material layer has a mass per unit area of 1.0 g/100 cm2 or more and 2.0 g/100 cm2 or more . It is 2 or less.
  • An electrode body according to another aspect of the present invention has a positive electrode for an energy storage element according to one embodiment of the present invention.
  • Another aspect of the present invention relates to an energy storage element having a positive electrode for an energy storage element according to one embodiment of the present invention.
  • Another aspect of the present invention relates to a power storage device that includes one or more power storage elements according to one embodiment of the present invention, and also includes two or more power storage elements.
  • a positive electrode for an energy storage element that can reduce the resistance of the energy storage element and increase the electrode density, or an electrode body, energy storage element, or energy storage device that includes such a positive electrode for an energy storage element.
  • FIG. 1 is a perspective view showing an electric storage element having a positive electrode for the electric storage element according to one embodiment of the present invention.
  • FIG. 2 is a schematic diagram showing an electric storage device constructed by assembling a plurality of electric storage elements each having a positive electrode for the electric storage element according to one embodiment of the present invention.
  • FIG. 3 is a particle size distribution diagram of the positive electrode active material particles contained in the energy storage elements of Example 3 and Comparative Example 2.
  • a positive electrode for an energy storage device includes a substrate and a positive electrode active material layer laminated on the substrate and containing positive electrode active material particles, the positive electrode active material particles including first active material particles and second active material particles having different particle diameters, wherein in a particle size distribution diagram of the positive electrode active material particles with the horizontal axis representing particle diameter [ ⁇ m] and the vertical axis representing volume-based frequency [%], the first active material particles exhibit a first peak particle diameter of 4.0 ⁇ m or more and the second active material particles exhibit a second peak particle diameter smaller than the first peak particle diameter, the first active material particles have a breaking strength of 20.0 MPa or more, the ratio of the frequency [%] of the first peak particle diameter to the frequency [%] of the second peak particle diameter in the particle size distribution diagram is 1.0 or more and 4.3 or less, and the positive electrode active material layer has a mass per unit area of 1.0 g/100 cm2 or more and 2.0 g/100 cm2 or more . It is 2 or less.
  • the positive electrode for an electric storage element described in [1] above can reduce the resistance of the electric storage element and increase the electrode density. The reason for this is not clear, but the following reason is presumed.
  • the hardness of the active material particles may be increased so that the active material particles sink into the substrate and improve adhesion between the substrate and the positive electrode active material layer. Furthermore, to effectively improve adhesion between the substrate and the positive electrode active material layer, it is necessary to increase not only the hardness of the active material particles but also the particle size to a certain level.
  • the positive electrode for a storage battery device described in [1] includes a positive electrode active material layer containing first active material particles having a peak particle size and fracture strength within the above-mentioned ranges in a particle size distribution diagram.
  • the first active material particles sink into the substrate, thereby enhancing adhesion between the substrate and the positive electrode active material layer, thereby reducing the resistance of the storage battery device.
  • the positive electrode active material layer contains, in addition to the first active material particles, second active material particles having a smaller peak particle size than the first active material particles at a certain frequency. Therefore, the first active material particles reduce the resistance of the storage battery device, while the second active material particles penetrate between the first active material particles, thereby increasing the density of the positive electrode active material layer without causing cracks or other problems. Furthermore, because the mass per unit area of the positive electrode active material layer is controlled within the above-mentioned ranges, it is easy to reduce the resistance of the storage battery device and improve the electrode density. This point is explained below.
  • the positive electrode for a storage device described in [1] above is typically manufactured by applying a so-called positive electrode mixture to a substrate and then pressing it to form a positive electrode active material layer. This is then wound or stacked with a negative electrode or the like to produce an electrode assembly, which is then used in the storage device. Pressing the positive electrode mixture too hard increases the density of the positive electrode active material layer, but as described above, the strength of the positive electrode active material layer is likely to decrease. Furthermore, if the mass per unit area of the positive electrode active material layer is large, the positive electrode active material layer laminated on the substrate becomes thick, which is likely to cause cracking of the positive electrode active material layer, peeling from the substrate, or fracture of the substrate itself during the process of producing the electrode assembly.
  • the mass per unit area of the positive electrode active material layer is large, it is necessary to correspondingly reduce the density of the positive electrode active material layer (i.e., to weaken the pressure on the positive electrode mixture). Conversely, when the mass per unit area of the positive electrode active material layer is small, it is possible to increase the density of the positive electrode active material layer (to press the positive electrode mixture more strongly). In other words, by controlling the mass per unit area of the positive electrode active material layer within the above range, it is possible to easily reduce the resistance of the energy storage element and improve the electrode density.
  • the positive electrode described in [1] above has the effect of reducing the resistance of the energy storage element and increasing the electrode density due to the synergistic effect of the physical properties and frequency in the particle size distribution diagram of the first active material particles and the second active material particles, and the mass per unit area of the positive electrode active material layer.
  • particle size distribution diagram refers to a graph showing the particle size distribution (frequency distribution curve) of particle sizes measured by laser diffraction/scattering for a diluted solution of positive electrode active material particles diluted with a solvent, in accordance with JIS-Z-8825 (2013).
  • peak particle size refers to the particle size corresponding to the maximum value on the particle size distribution diagram.
  • first peak particle size of first active material particles refers to the particle size at the maximum value of the portion of the particle size distribution diagram corresponding to the first active material particles
  • second peak particle size of second active material particles refers to the particle size at the maximum value of the portion of the particle size distribution diagram corresponding to the second active material particles.
  • peak particle size refers to the peak particle size of secondary particles, but if the positive electrode active material particles do not constitute secondary particles, it refers to the peak particle size of primary particles.
  • different particle sizes refers to different peak particle sizes on the particle size distribution diagram.
  • particle size distribution of the first active material particles and the second active material particles overlap so much in the particle size distribution diagram that the peak particle diameters of each cannot be clearly identified
  • numerical analysis software can be used to separate the two particle size distributions and measure the peak particle diameters. Examples of numerical analysis software include MATLAB (registered trademark) (The MathWorks) and ORIGIN PRO (registered trademark) (Lightstone). Furthermore, particle size distributions can be separated using known techniques.
  • breaking strength is measured in accordance with JIS-Z-8844 (2019). Breaking strength is measured by collecting five first active material particles and using the average value. However, particles whose particle diameters fall within the range where the particle size distributions of the first active material particles and the second active material particles overlap are excluded from selection.
  • the "particle diameter" of each particle used to measure breaking strength is the average value of the minor axis and major axis.
  • the minor axis is the shortest diameter passing through the center of the smallest circumscribing circle of the particle, and the major axis is the diameter passing through the center and perpendicular to the minor axis. If there are two or more shortest diameters, the diameter perpendicular to the other diameters is taken as the minor axis.
  • the particle size distribution and fracture strength of the positive electrode active material particles are measured on the positive electrode active material particles before charge/discharge if they are available. If a positive electrode containing positive electrode active material particles is incorporated into an energy storage device, the measurements are performed on positive electrode active material particles collected from the positive electrode of the energy storage device in a fully discharged state, as described below. First, the energy storage device is charged at a constant current of 0.05 C until the end-of-charge voltage for normal use is reached, and then fully charged. After a 30-minute rest, the device is discharged at a constant current of 0.05 C until the end-of-discharge voltage for normal use is reached.
  • the device is then disassembled, the positive electrode is removed, and a test battery is assembled using the removed positive electrode as the working electrode and a metallic lithium electrode as the counter electrode.
  • the metallic lithium electrode used here is pure metallic lithium.
  • the test battery is then discharged at a constant current of 10 mA per gram of positive electrode active material until the positive electrode potential reaches 2.0 V (vs. Li/Li + ), adjusting the positive electrode to a fully discharged state.
  • the battery is disassembled again, and the positive electrode is removed. Dimethyl carbonate is used to thoroughly wash away any electrolyte or other substances adhering to the removed positive electrode, and the battery is vacuum dried at room temperature for 24 hours, after which the positive electrode active material particles from the positive electrode active material layer are collected.
  • the collected positive electrode active material particles are subjected to measurement.
  • the operations from disassembling the battery element to collecting the positive electrode active material particles are carried out in an argon atmosphere with a dew point of -60°C or lower. "During normal use” refers to the case where the battery element is used under the charge/discharge conditions recommended or specified for the battery element, and, if equipment for using the battery element is available, the device is used to use the battery element.
  • the "mass per unit area of the positive electrode active material layer” is the value obtained by dividing the mass (g) of the positive electrode active material layer in the positive electrode by the area (100 cm 2 ) of the region where the positive electrode active material layer is laminated. For example, when the positive electrode active material layer is laminated over the entire surface of one side of a sheet-shaped positive electrode substrate, the “mass per unit area of the positive electrode active material layer” is the value obtained by dividing the total mass of the positive electrode active material layer by the area of one side of the positive electrode substrate.
  • the "mass per unit area of the positive electrode active material layer” is the value obtained by dividing the total mass of the positive electrode active material layer by the area of both sides of the positive electrode substrate.
  • the ratio of the first peak particle diameter to the second peak particle diameter may be 6.0 or greater.
  • the ratio of the first peak particle diameter to the second peak particle diameter is in the above range, so that the difference between the first peak particle diameter and the second peak particle diameter is sufficiently large, making it easier to increase the electrode density.
  • the first active material particles and the second active material particles may contain a lithium transition metal compound having a polyanion structure. Active material particles containing a lithium transition metal compound having a polyanion structure tend to have poor adhesion to the substrate. Therefore, the positive electrode for a storage battery element described in [3] above, in which the first active material particles and the second active material particles contain a lithium transition metal compound having a polyanion structure, significantly achieves the advantages of the present invention, namely, reducing the resistance of the storage battery element and increasing the electrode density.
  • An electrode body according to another aspect of the present invention has a positive electrode for a storage element described in any one of [1] to [3] above.
  • the electrode body described in [4] above has a positive electrode for a storage element described in any one of [1] to [3] above, thereby reducing the resistance of the storage element and increasing the electrode density of the positive electrode.
  • Another aspect of the present invention relates to an energy storage element having a positive electrode for an energy storage element described in any one of [1] to [3] above or an electrode body described in [4] above.
  • FIG. 6 Another aspect of the present invention relates to a power storage device that includes one or more power storage elements described in [5] above, and also includes two or more power storage elements.
  • the energy storage device described in [6] above includes one or more energy storage elements described in [5] above, thereby reducing the resistance of the energy storage device and increasing the electrode density of the positive electrode.
  • the following describes in detail a positive electrode for an energy storage element, an electrode body, an energy storage element, a method for manufacturing an energy storage element, an energy storage device, and other embodiments according to one embodiment of the present invention.
  • the names of the components (elementary components) used in each embodiment may differ from the names of the components (elementary components) used in the background art.
  • the value of the parameter can be within a range that combines either of the lower limits and either of the upper limits (however, the lower limit is smaller than the upper limit).
  • a positive electrode for an energy storage device includes a substrate and a positive electrode active material layer laminated directly on the substrate.
  • the positive electrode active material layer contains positive electrode active material particles.
  • the positive electrode for an energy storage device will also be referred to simply as the "positive electrode,” and the substrate of the positive electrode will also be referred to as the "positive electrode substrate.”
  • the positive electrode has positive electrode active material particles and a positive electrode active material layer with the composition and physical properties described below, which can reduce the resistance of the energy storage element and increase the electrode density.
  • the positive electrode substrate is conductive. Whether or not a material is "conductive" is determined by using a volume resistivity of 10-2 ⁇ -cm measured in accordance with JIS-H-0505 (1975) as a threshold value.
  • Metals such as aluminum, titanium, tantalum, and stainless steel, or alloys thereof, are used as the material for the positive electrode substrate.
  • aluminum or aluminum alloys are preferred from the viewpoints of potential resistance, high conductivity, and cost.
  • Examples of positive electrode substrates include foils, vapor-deposited films, meshes, and porous materials, with foil being preferred from the viewpoint of cost. Therefore, aluminum foil or aluminum alloy foil is preferred as the positive electrode substrate.
  • Examples of aluminum or aluminum alloys include A1085, A3003, and A1N30 as specified in JIS-H-4000 (2014) or JIS-H-4160 (2006).
  • the average thickness of the positive electrode substrate is preferably 3 ⁇ m or more and 50 ⁇ m or less, more preferably 5 ⁇ m or more and 40 ⁇ m or less, even more preferably 8 ⁇ m or more and 30 ⁇ m or less, and particularly preferably 10 ⁇ m or more and 25 ⁇ m or less.
  • the positive electrode active material layer contains positive electrode active material particles.
  • the positive electrode active material layer can be formed from a so-called positive electrode mixture containing positive electrode active material particles.
  • the positive electrode active material layer may contain optional components such as a conductive agent, a thickener, and a filler as needed.
  • the positive electrode active material particles contain first and second active material particles having different particle diameters.
  • the particle diameter of the first active material particles is larger than the particle diameter of the second active material particles. That is, in a particle size distribution diagram of the positive electrode active material particles, with the horizontal axis representing particle diameter [ ⁇ m] and the vertical axis representing volume-based frequency [%], the first peak particle diameter of the first active material particles (hereinafter also referred to as "first particle diameter”) is larger than the second peak particle diameter of the second active material particles (hereinafter also referred to as "second particle diameter").
  • the first particle diameter typically coincides with the peak particle diameter of the first active material particles shown in a particle size distribution diagram of the first active material particles alone.
  • the second particle diameter typically coincides with the peak particle diameter of the second active material particles shown in a particle size distribution diagram of the second active material particles alone.
  • the second active material particles enter between the first active material particles, thereby increasing the density of the positive electrode active material layer.
  • the first active material particles and second active material particles may be single particles (single particles) consisting of multiple primary particles that do not aggregate, but are preferably secondary particles formed by aggregation of multiple primary particles.
  • the first active material particles and second active material particles are, for example, secondary particles of a lithium transition metal compound having a polyanion structure.
  • the particle size distribution curve of the above particle size distribution diagram for the positive electrode active material particles it is preferable that there is an inflection point between the peak indicated by the first active material particles and the peak indicated by the second active material particles, and it is more preferable that there is a valley or flat portion.
  • the differences in particle diameter, frequency in the particle size distribution diagram, etc. between the first and second active material particles are within an appropriate range, making it easy to reduce the resistance of the energy storage element.
  • the lower limit of the first particle diameter is 4.0 ⁇ m, preferably 4.2 ⁇ m, more preferably 4.4 ⁇ m, even more preferably 4.6 ⁇ m, and even more preferably 4.8 ⁇ m.
  • the upper limit of the first particle diameter is preferably 25.0 ⁇ m, more preferably 20.0 ⁇ m, even more preferably 15.0 ⁇ m, and even more preferably 10.0 ⁇ m.
  • the upper limit of the second particle diameter is preferably 2.0 ⁇ m, more preferably 1.5 ⁇ m, even more preferably 1.2 ⁇ m, and even more preferably 1.0 ⁇ m.
  • the density of the positive electrode active material layer can be easily increased.
  • the lower limit of the second particle diameter is preferably 0.4 ⁇ m, preferably 0.5 ⁇ m, more preferably 0.6 ⁇ m, and even more preferably 0.7 ⁇ m.
  • the lower limit of the ratio of the first particle diameter to the second particle diameter is preferably 6.0, more preferably 6.5, and may be 7.0 or 7.5.
  • the lower limit of the above ratio may be 8.0, 10.0, 20.0, or 30.0.
  • the upper limit of the above ratio is not particularly limited, but may be, for example, 50.0 or 45.0.
  • a grinder, classifier, etc. is used. Grinding methods include, for example, methods using a mortar, ball mill, sand mill, vibrating ball mill, planetary ball mill, jet mill, counter jet mill, swirling airflow jet mill, or sieve. Wet grinding in the presence of water or an organic solvent such as hexane can also be used during grinding. Sieves, air classifiers, etc. are used as needed for both dry and wet classification methods.
  • the lower limit of the breaking strength of the first active material particles is 20.0 MPa, preferably 30.0 MPa, more preferably 40.0 MPa, and even more preferably 50.0 MPa. If the breaking strength of the first active material particles is equal to or greater than the above lower limit, the resistance of the energy storage element can be reduced. On the other hand, from the viewpoint of manufacturability, the upper limit of the breaking strength of the first active material particles is preferably 200.0 MPa, more preferably 150.0 MPa, and even more preferably 100.0 MPa.
  • the breaking strength of the first active material particles can be controlled by manufacturing conditions such as the type of positive electrode active material and the carbon material coating its surface, as well as the manufacturing method of the positive electrode active material (hydrothermal method, solid-phase method, etc.), firing conditions, and conditions of the method of forming the positive electrode active material particles (spray drying method, etc.).
  • polyanion compounds include compounds containing an oxoacid anion (PO 4 3 ⁇ , SO 4 2 ⁇ , SiO 4 4 ⁇ , BO 3 3 ⁇ , VO 4 3 ⁇ , etc.), a lithium ion, and a transition metal ion.
  • the oxoacid anion may be a condensed anion (P 2 O 7 4 ⁇ , P 3 O 10 5 ⁇ , etc.).
  • the polyanion compound may have an olivine-type crystal structure.
  • the polyanion compound typically contains a lithium element and a transition metal element and may further contain other elements (e.g., halogen elements).
  • Preferred transition metal elements contained in the polyanion compound are iron, manganese, nickel, and cobalt, with iron being more preferred.
  • Preferred oxoacid anion contained in the polyanion compound is a phosphate anion (PO 4 3 ⁇ ).
  • the polyanionic compound is preferably a compound represented by the following formula (1): Li a M b (AO c ) d X e ...(1)
  • M is at least one transition metal element.
  • A is at least one selected from B, Al, Si, P, S, Cl, Ti, V, Cr, Mo, and W.
  • X is at least one halogen element.
  • a, b, c, d, and e are numbers satisfying 0 ⁇ a ⁇ 3, 0 ⁇ b ⁇ 2, 2 ⁇ c ⁇ 4, 1 ⁇ d ⁇ 3, and 0 ⁇ e ⁇ 1.
  • a, b, c, d, and e may all be integers or decimals.
  • polyanion compounds include LiFePO4 , LiCoPO4, LiFe0.5Co0.5PO4 , LiMnPO4 , LiNiPO4 , LiMn0.5Fe0.5PO4 , LiCrPO4 , LiFeVO4 , Li2FeSiO4, Li2Fe2 ( SO4 ) 3 , LiFeBO3 , LiFePO3.9F0.2 , Li3V2 ( PO4 ) 3 , Li2MnSiO4 , Li2CoPO4F , and the like .
  • the atoms or polyanions in these polyanionic compounds may be partially substituted with other atoms or anionic species.
  • the polyanionic compounds may be used singly or in combination of two or more.
  • the first active material particles and the second active material particles each contain a polyanionic compound as their main component.
  • “Containing a polyanionic compound as their main component” means that the polyanionic compound content is 50% by mass or more.
  • the polyanionic compound content contained in each of the first active material particles and the second active material particles is preferably 70% by mass or more, more preferably 90% by mass or more, and even more preferably 99% by mass or more.
  • the first active material particles and the second active material particles can exhibit sufficient electronic conductivity between the particles.
  • the carbon material is, for example, an inorganic material with a carbon element content of 80% by mass or more and 100% by mass or less.
  • the carbon element content in the carbon material may be 90% by mass or more, or may be 95% by mass or more.
  • Elements other than carbon that may be contained in the carbon material include oxygen, hydrogen, nitrogen, etc. Examples of carbon materials include graphite and non-graphitic carbon.
  • the carbon material content in each of the first active material particles and the second active material particles is preferably 0.1% by mass or more and 20% by mass or less, more preferably 0.2% by mass or more and 10% by mass or less, even more preferably 0.3% by mass or more and 5% by mass or less, and even more preferably 0.5% by mass or more and 2% by mass or less.
  • the carbon material content in each of the first active material particles and the second active material particles is above the above lower limit, it is possible to improve electronic conductivity, etc.
  • the carbon material content in each of the first active material particles and the second active material particles is below the above upper limit, it is possible to increase the polyanion compound content and increase the discharge capacity per volume of a positive electrode using the first active material particles and the second active material particles, etc.
  • the positive electrode active material particles may contain other active material particles in addition to the first active material particles and second active material particles described above.
  • the other active material particles may be known positive electrode active material particles.
  • the total content of the first active material particles and second active material particles in all the positive electrode active material particles is preferably 90% by mass or more, more preferably 99% by mass or more, and may be substantially 100% by mass.
  • the positive electrode active material particles may consist essentially of the first active material particles and the second active material particles.
  • the positive electrode active material particles contain first active material particles and second active material particles.
  • the positive electrode active material particles are obtained by mixing the first active material particles and the second active material particles.
  • the first active material particles and the second active material particles can be selected from, for example, publicly known positive electrode active material particles that are commercially available.
  • the first active material particles and the second active material particles can also be manufactured by the method described below.
  • the first active material particles and the second active material particles contained in the positive electrode active material particles are not limited to those manufactured by the manufacturing method described below.
  • the first active material particles are primarily composed of a polyanion compound
  • the first active material particles are produced by adjusting the pH of the reaction solution using ammonia water or the like when producing the hydroxide precursor in a method that uses a hydroxide precursor, a lithium source, and a carbon source. This makes it easy to obtain first active material particles with the desired breaking strength.
  • a hydroxide precursor is obtained by a precipitation reaction between transition metal ions and hydroxide ions in water.
  • a transition metal salt aqueous solution and a sodium hydroxide aqueous solution are dropped into water to obtain a hydroxide precursor (a transition metal hydroxide).
  • the transition metal salt may be any water-soluble salt containing the transition metal element that constitutes the desired lithium transition metal compound, such as iron sulfate, iron chloride, cobalt sulfate, manganese sulfate, or nickel sulfate.
  • a potassium hydroxide aqueous solution may be used instead of the sodium hydroxide aqueous solution.
  • reaction solution When the transition metal salt aqueous solution and the sodium hydroxide aqueous solution are dropped into water, an ammonia aqueous solution or the like is further dropped into the reaction solution to maintain the pH of the water (reaction solution) into which these aqueous solutions are dropped within a predetermined range.
  • the pH of the reaction solution is preferably in the range of 8.5 to 11.6. If the pH of the reaction solution is outside the above range, or if the pH of the reaction solution is within the above range but an aqueous ammonia solution or the like is not added dropwise to the reaction solution, the particle size change amount of the finally obtained first active material particles when pressed tends to be large, i.e., the breaking strength of the first active material particles tends to be low.
  • the concentration of the aqueous ammonia solution to be added dropwise can be, for example, about 0.3 mol/dm 3 or more and 1 mol/dm 3 or less.
  • the pH of the reaction solution can be adjusted by adjusting the concentration, amount, etc. of the aqueous ammonia solution and the aqueous sodium hydroxide solution to be added dropwise.
  • Another alkaline aqueous solution such as an aqueous hydrazine solution may also be added dropwise together with the aqueous ammonia solution or the like.
  • the pH of the reaction solution can also be adjusted by the amount, etc., of the other alkaline aqueous solution added.
  • the obtained hydroxide precursor, a lithium source, and a carbon source are mixed and baked under an inert atmosphere (e.g., a nitrogen atmosphere) to obtain first active material particles mainly composed of a polyanion compound according to one embodiment of the present invention.
  • an inert atmosphere e.g., a nitrogen atmosphere
  • the lithium source compounds having a polyanion structure and containing lithium element, such as LiH2PO4 , Li3PO4 , and LiHSO4 , can be suitably used.
  • Other lithium sources include LiOH and lithium halides.
  • salts of ammonium cations and polyanions such as NH4H2PO4 , ( NH4 ) 3PO4 , ( NH4 ) 2HPO4 , ( NH4 ) 2SO4 , and NH4VO3 , can be suitably used.
  • the carbon source may be an organic substance such as sucrose, lactose, maltose, sucrose, polyvinyl alcohol, ascorbic acid, etc.
  • the baking temperature may be, for example, 500°C or higher and 800°C or lower.
  • the second active material particles When the second active material particles have a polyanionic compound as their main component, the second active material particles can be obtained by adjusting the particle size of active material particles obtained by the same manufacturing method as the first active material particles having a polyanionic compound as their main component, using the grinding method described above as appropriate.
  • the content of the positive electrode active material particles in the positive electrode active material layer is preferably 70% by mass to 99% by mass, more preferably 80% by mass to 98% by mass, and even more preferably 90% by mass to 95% by mass.
  • the lower limit of the mass per unit area of the positive electrode active material layer is 1.0 g/100 cm 2.
  • the lower limit may be 1.2 g/100 cm 2 , 1.4 g/100 cm 2 , or 1.6 g/100 cm 2.
  • the upper limit of the mass per unit area of the positive electrode active material layer is 2.0 g/100 cm 2 or less, and preferably 1.8 g/100 cm 2.
  • the upper limit may be 1.6 g/100 cm 2 , 1.4 g/100 cm 2 , or 1.2 g/100 cm 2.
  • the conductive agent is not particularly limited as long as it is a material that is conductive.
  • Examples of such conductive agents include carbonaceous materials, metals, and conductive ceramics.
  • Carbonaceous materials include graphite, non-graphitic carbon, and graphene-based carbon.
  • Non-graphitic carbon includes carbon nanofiber, pitch-based carbon fiber, and carbon black.
  • Carbon black includes furnace black, acetylene black, and ketjen black.
  • Graphene-based carbon includes graphene, carbon nanotubes (CNT), and fullerene.
  • the conductive agent may be in the form of powder or fiber.
  • one of these materials may be used alone, or two or more may be mixed. These materials may also be used in combination.
  • a composite of carbon black and CNT may be used. Of these, carbon black is preferred from the standpoints of electronic conductivity and coatability, and acetylene black is particularly preferred.
  • the content of the conductive agent in the positive electrode active material layer is preferably 1% by mass or more and 8% by mass or less, and more preferably 3% by mass or more and 5% by mass or less.
  • the energy density of the non-aqueous electrolyte storage element can be increased. Note that if the first active material particles and the second active material particles have a coating layer made of a carbon material on their surfaces, the coating layer on the first active material particles and the second active material particles is not considered to be included in the conductive agent.
  • binders include thermoplastic resins such as fluororesins (polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), etc.), polyethylene, polypropylene, polyacrylic, and polyimide; elastomers such as ethylene-propylene-diene rubber (EPDM), sulfonated EPDM, styrene-butadiene rubber (SBR), and fluororubber; and polysaccharide polymers.
  • PTFE polytetrafluoroethylene
  • PVDF polyvinylidene fluoride
  • EPDM ethylene-propylene-diene rubber
  • SBR styrene-butadiene rubber
  • fluororubber polysaccharide polymers
  • the binder content in the positive electrode active material layer is preferably 1% by mass or more and 8% by mass or less, and more preferably 2% by mass or more and 5% by mass or less. By keeping the binder content within this range, the positive electrode active material can be stably maintained.
  • thickeners examples include polysaccharide polymers such as carboxymethyl cellulose (CMC) and methyl cellulose. If the thickener has a functional group that reacts with lithium or the like, this functional group may be deactivated in advance by methylation or the like.
  • the content of the thickener in the positive electrode active material layer is preferably 5% by mass or less, and more preferably 1% by mass or less.
  • the technology disclosed herein can be preferably implemented in an embodiment in which the positive electrode active material layer does not contain a thickener.
  • the filler is not particularly limited.
  • examples of fillers include polyolefins such as polypropylene and polyethylene; inorganic oxides such as silicon dioxide, alumina, titanium dioxide, calcium oxide, strontium oxide, barium oxide, magnesium oxide, and aluminosilicates; hydroxides such as magnesium hydroxide, calcium hydroxide, and aluminum hydroxide; carbonates such as calcium carbonate; sparingly soluble ionic crystals such as calcium fluoride, barium fluoride, and barium sulfate; nitrides such as aluminum nitride and silicon nitride; mineral-derived substances such as talc, montmorillonite, boehmite, zeolite, apatite, kaolin, mullite, spinel, olivine, sericite, bentonite, and mica; and artificial products thereof.
  • the content of the filler in the positive electrode active material layer is preferably 5% by mass or less, and even more preferably 1% by mass or less.
  • the technology disclosed herein can be preferably implemented in an embodiment in which the positive electrode active material layer does not contain a filler.
  • the positive electrode active material layer may contain typical non-metallic elements such as B, N, P, F, Cl, Br, and I; typical metallic elements such as Li, Na, Mg, Al, K, Ca, Zn, Ga, Ge, Sn, Sr, and Ba; and transition metal elements such as Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Mo, Zr, Nb, and W as components other than the positive electrode active material particles, conductive agent, binder, thickener, and filler.
  • typical non-metallic elements such as B, N, P, F, Cl, Br, and I
  • typical metallic elements such as Li, Na, Mg, Al, K, Ca, Zn, Ga, Ge, Sn, Sr, and Ba
  • transition metal elements such as Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Mo, Zr, Nb, and W as components other than the positive electrode active material particles, conductive agent, binder, thickener, and filler.
  • An electrode assembly according to one embodiment of the present invention is an electrode assembly configured by stacking a positive electrode and a negative electrode according to one embodiment of the present invention with a separator interposed therebetween.
  • the electrode assembly for example, an electrode assembly having a known structure, such as a wound electrode assembly or a stacked electrode assembly, can be used.
  • the electrode assembly is used in, for example, a storage element such as a non-aqueous electrolyte secondary battery. Because the electrode assembly according to one embodiment of the present invention has a positive electrode according to one embodiment of the present invention, the resistance of the storage element can be reduced and the electrode density of the positive electrode can be increased.
  • a wound electrode body has a structure in which a positive electrode and a negative electrode are wound while being insulated.
  • the wound electrode body may be cylindrical (columnar) or flat.
  • the electrode body 2 provided in the energy storage element 1 of Figure 1 is a flat wound electrode body.
  • a wound electrode body can be produced, for example, by the following procedure. First, a positive electrode, a separator, and a negative electrode, each formed in a strip shape, are stacked in this order to obtain a laminate. This laminate is then wound to obtain a wound electrode body.
  • wound electrode bodies are prone to cracking of the positive electrode active material layer or peeling from the substrate at curved portions of the positive electrode, etc. For this reason, the benefits of using such a positive electrode, such as reduced resistance of the energy storage element, can be significantly obtained.
  • a laminated electrode body has a structure in which one or more positive electrodes and one or more negative electrodes are stacked in an insulated state.
  • a laminated electrode body can be obtained by stacking a positive electrode, a separator, and a negative electrode, each of which is formed in a rectangular shape, in that order.
  • Electrode structures may also be used, such as those in which at least one of the positive and negative electrodes is folded accordion-like and stacked.
  • the positive electrode according to one embodiment of the present invention described above is used as the positive electrode.
  • the negative electrode has a negative electrode substrate and a negative electrode active material layer disposed on the negative electrode substrate directly or via an intermediate layer.
  • the configuration of the intermediate layer is not particularly limited and can be selected from the configurations exemplified for the positive electrode above, for example.
  • the negative electrode substrate is conductive.
  • Materials used for the negative electrode substrate include metals such as copper, nickel, stainless steel, nickel-plated steel, and aluminum, or alloys of these metals, and carbon materials. Of these, copper or copper alloys are preferred.
  • Examples of negative electrode substrates include foil, vapor-deposited film, mesh, and porous materials, with foil being preferred from a cost perspective. Therefore, copper foil or copper alloy foil is preferred as the negative electrode substrate.
  • Examples of copper foil include rolled copper foil and electrolytic copper foil.
  • the average thickness of the negative electrode substrate is preferably 2 ⁇ m or more and 35 ⁇ m or less, more preferably 3 ⁇ m or more and 30 ⁇ m or less, even more preferably 4 ⁇ m or more and 25 ⁇ m or less, and particularly preferably 5 ⁇ m or more and 20 ⁇ m or less.
  • the negative electrode active material layer contains a negative electrode active material.
  • the negative electrode active material layer may contain optional components such as a conductive agent, binder, thickener, and filler as needed.
  • the optional components such as a conductive agent, binder, thickener, and filler can be selected from the materials exemplified for the positive electrode above.
  • the negative electrode active material layer may contain typical non-metallic elements such as B, N, P, F, Cl, Br, and I; typical metallic elements such as Li, Na, Mg, Al, K, Ca, Zn, Ga, Ge, Sn, Sr, and Ba; and transition metal elements such as Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Mo, Zr, Ta, Hf, Nb, and W as components other than the negative electrode active material, conductive agent, binder, thickener, and filler.
  • typical non-metallic elements such as B, N, P, F, Cl, Br, and I
  • typical metallic elements such as Li, Na, Mg, Al, K, Ca, Zn, Ga, Ge, Sn, Sr, and Ba
  • transition metal elements such as Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Mo, Zr, Ta, Hf, Nb, and W as components other than the negative electrode active material, conductive agent, binder, thickener, and filler
  • the negative electrode active material can be appropriately selected from known negative electrode active materials.
  • a material capable of absorbing and releasing lithium ions is typically used as the negative electrode active material for lithium ion secondary batteries.
  • negative electrode active materials include metal Li; metals or semimetals such as Si and Sn; metal oxides or semimetal oxides such as Si oxide, Ti oxide, and Sn oxide; titanium-containing oxides such as Li 4 Ti 5 O 12 , LiTiO 2 , and TiNb 2 O 7 ; polyphosphate compounds; silicon carbide; carbon materials such as graphite and non-graphitic carbon (easily graphitizable carbon or non-graphitizable carbon). Among these materials, graphite and non-graphitic carbon are preferred. In the negative electrode active material layer, one of these materials may be used alone, or two or more may be mixed and used.
  • Graphite refers to a carbon material in which the average lattice spacing (d 002 ) of the (002) plane, as determined by X-ray diffraction before charge/discharge or in a discharged state, is 0.33 nm or more and less than 0.34 nm. Examples of graphite include natural graphite and artificial graphite. Artificial graphite is preferred from the viewpoint of being able to obtain a material with stable physical properties.
  • Non-graphitic carbon refers to a carbon material in which the average lattice spacing (d 002 ) of the (002) plane, as determined by X-ray diffraction before charge/discharge or in a discharged state, is 0.34 nm or more and 0.42 nm or less.
  • Examples of non-graphitic carbon include non-graphitizable carbon and graphitizable carbon.
  • Examples of non-graphitic carbon include resin-derived materials, petroleum pitch or petroleum pitch-derived materials, petroleum coke or petroleum coke-derived materials, plant-derived materials, and alcohol-derived materials.
  • discharged state refers to a state in which the negative electrode active material, the carbon material, has been discharged so that lithium ions that can be absorbed and released during charging and discharging are sufficiently released.
  • this refers to a state in which the open circuit voltage is 0.7 V or higher in a half cell using a negative electrode containing a carbon material as the negative electrode active material as the working electrode and metallic Li as the counter electrode.
  • non-graphitizable carbon refers to a carbon material having the above d 002 of 0.36 nm or more and 0.42 nm or less.
  • epi graphitizable carbon refers to a carbon material having the above d 002 of 0.34 nm or more and less than 0.36 nm.
  • the negative electrode active material is typically a particle (powder).
  • the average particle size of the negative electrode active material can be, for example, 1 nm or more and 100 ⁇ m or less.
  • the average particle size may be 1 ⁇ m or more and 100 ⁇ m or less.
  • the negative electrode active material is Si, Sn, Si oxide, Sn oxide, or the like, the average particle size may be 1 nm or more and 1 ⁇ m or less. Setting the average particle size of the negative electrode active material to be above the above lower limit facilitates the manufacture and handling of the negative electrode active material.
  • average particle size refers to the value at which the volume-based cumulative distribution calculated in accordance with JIS-Z-8819-2 (2001) is 50%, based on the particle size distribution measured by laser diffraction/scattering in a diluted solution obtained by diluting particles with a solvent in accordance with JIS-Z-8825 (2013).
  • a pulverizer or classifier is used to obtain powder with a specified particle size.
  • the negative electrode active material is a metal such as metallic Li
  • the negative electrode active material layer may be in the form of a foil.
  • the content of the negative electrode active material in the negative electrode active material layer is preferably 60% by mass or more and 99% by mass or less, and more preferably 90% by mass or more and 98% by mass or less. By keeping the content of the negative electrode active material within this range, it is possible to achieve both high energy density and manufacturability in the negative electrode active material layer.
  • the separator can be appropriately selected from known separators.
  • separators that can be used include separators consisting of only a substrate layer and separators in which a heat-resistant layer containing heat-resistant particles and a binder is formed on one or both surfaces of the substrate layer.
  • the shape of the substrate layer of the separator include woven fabric, nonwoven fabric, and porous resin film. Among these shapes, porous resin films are preferred from the viewpoint of strength, and nonwoven fabrics are preferred from the viewpoint of non-aqueous electrolyte retention.
  • Materials for the substrate layer of the separator are preferably polyolefins such as polyethylene and polypropylene from the viewpoint of shutdown function, and polyimide and aramid from the viewpoint of oxidative decomposition resistance.
  • a composite material of these resins may also be used for the substrate layer of the separator.
  • the heat-resistant particles contained in the heat-resistant layer preferably exhibit a mass loss of 5% or less when heated from room temperature to 500°C in an air atmosphere at 1 atmosphere pressure, and more preferably exhibit a mass loss of 5% or less when heated from room temperature to 800°C.
  • Examples of materials exhibiting a mass loss of a predetermined value or less include inorganic compounds.
  • inorganic compounds include oxides such as iron oxide, silicon oxide, aluminum oxide, titanium oxide, zirconium oxide, calcium oxide, strontium oxide, barium oxide, magnesium oxide, and aluminosilicates; nitrides such as aluminum nitride and silicon nitride; carbonates such as calcium carbonate; sulfates such as barium sulfate; sparingly soluble ionic crystals such as calcium fluoride, barium fluoride, and barium titanate; covalently bonded crystals such as silicon and diamond; mineral-derived substances such as talc, montmorillonite, boehmite, zeolite, apatite, kaolin, mullite, spinel, olivine, sericite, bentonite, and mica, as well as artificial products thereof.
  • oxides such as iron oxide, silicon oxide, aluminum oxide, titanium oxide, zirconium oxide, calcium oxide, strontium oxide, barium oxide, magnesium oxide, and aluminosilicates
  • these substances may be used alone or in the form of a complex, or two or more may be mixed and used.
  • silicon oxide, aluminum oxide, or aluminosilicate are preferred from the perspective of the safety of the energy storage element.
  • the porosity of the separator is preferably 80% by volume or less from the perspective of strength, and 20% by volume or more from the perspective of discharge performance.
  • porosity refers to a volume-based value measured using a mercury porosimeter.
  • a polymer gel composed of a polymer and a non-aqueous electrolyte may be used as the separator.
  • examples of polymers include polyacrylonitrile, polyethylene oxide, polypropylene oxide, polymethyl methacrylate, polyvinyl acetate, polyvinylpyrrolidone, and polyvinylidene fluoride.
  • Using a polymer gel has the effect of suppressing leakage.
  • the separator may also be a combination of a porous resin film or nonwoven fabric, such as those mentioned above, and a polymer gel.
  • An energy storage element includes an electrode assembly having a positive electrode, a negative electrode, and a separator according to one embodiment of the present invention, an electrolyte, and a container that accommodates the electrode assembly and the electrolyte.
  • the electrode assembly is typically a stacked type in which multiple positive electrodes and multiple negative electrodes are stacked with separators interposed therebetween, or a wound type in which positive electrodes and negative electrodes are stacked with separators interposed therebetween and wound.
  • the electrolyte is present in a state contained in the positive electrode, negative electrode, and separator.
  • the electrolyte may be a nonaqueous electrolyte.
  • a nonaqueous electrolyte secondary battery hereinafter simply referred to as a "secondary battery" in which the electrolyte is a nonaqueous electrolyte will be described.
  • the energy storage element according to one embodiment of the present invention has a positive electrode according to one embodiment of the present invention, which allows for low resistance and high electrode density of the positive electrode.
  • the electrode body uses the positive electrode according to one embodiment of the present invention described above, the negative electrode described above, and a separator.
  • the nonaqueous electrolyte can be appropriately selected from known nonaqueous electrolytes.
  • the nonaqueous electrolyte may be a nonaqueous electrolytic solution.
  • the nonaqueous electrolytic solution contains a nonaqueous solvent and an electrolyte salt dissolved in the nonaqueous solvent.
  • the non-aqueous solvent can be appropriately selected from known non-aqueous solvents.
  • non-aqueous solvents include cyclic carbonates, chain carbonates, carboxylic acid esters, phosphate esters, sulfonic acid esters, ethers, amides, and nitriles.
  • Non-aqueous solvents in which some of the hydrogen atoms contained in these compounds have been substituted with halogens may also be used.
  • Cyclic carbonates include ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), vinylene carbonate (VC), vinylethylene carbonate (VEC), chloroethylene carbonate, fluoroethylene carbonate (FEC), difluoroethylene carbonate (DFEC), styrene carbonate, 1-phenylvinylene carbonate, 1,2-diphenylvinylene carbonate, etc. Of these, EC is preferred.
  • chain carbonates examples include diethyl carbonate (DEC), dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), diphenyl carbonate, trifluoroethyl methyl carbonate, and bis(trifluoroethyl) carbonate. Of these, EMC is preferred.
  • a cyclic carbonate or a chain carbonate as the non-aqueous solvent, and it is even more preferable to use a combination of a cyclic carbonate and a chain carbonate.
  • the use of a cyclic carbonate promotes dissociation of the electrolyte salt, improving the ionic conductivity of the non-aqueous electrolyte.
  • the use of a chain carbonate reduces the viscosity of the non-aqueous electrolyte.
  • the volume ratio of the cyclic carbonate to the chain carbonate is preferably in the range of, for example, 5:95 to 50:50.
  • the electrolyte salt can be appropriately selected from known electrolyte salts.
  • electrolyte salts include lithium salts, sodium salts, potassium salts, magnesium salts, and onium salts. Of these, lithium salts are preferred.
  • lithium salts examples include inorganic lithium salts such as LiPF6 , LiPO2F2 , LiBF4 , LiClO4 , and LiN ( SO2F ) 2 ; lithium oxalate salts such as lithium bis(oxalate)borate (LiBOB), lithium difluorooxalateborate (LiFOB), and lithium bis( oxalate )difluorophosphate ( LiFOP ); and lithium salts having a halogenated hydrocarbon group such as LiSO3CF3 , LiN( SO2CF3 ) 2 , LiN( SO2C2F5 ) 2 , LiN ( SO2CF3 ) ( SO2C4F9 ) , LiC( SO2CF3 ) 3 , and LiC( SO2C2F5 ) 3 .
  • inorganic lithium salts are preferred, and LiPF6 is more preferred.
  • the content of the electrolyte salt in the non-aqueous electrolyte solution at 20°C and 1 atmosphere is preferably 0.1 mol/dm3 or more and 2.5 mol/dm3 or less, more preferably 0.3 mol/dm3 or more and 2.0 mol/dm3 or less, even more preferably 0.5 mol/dm3 or more and 1.7 mol/dm3 or less , and particularly preferably 0.7 mol/dm3 or more and 1.5 mol/ dm3 or less.
  • the nonaqueous electrolyte may contain additives.
  • additives include halogenated carbonates such as fluoroethylene carbonate (FEC) and difluoroethylene carbonate (DFEC); oxalates such as lithium bis(oxalate)borate (LiBOB), lithium difluorooxalateborate (LiFOB), and lithium bis(oxalate)difluorophosphate (LiFOP); imide salts such as lithium bis(fluorosulfonyl)imide (LiFSI); biphenyl, alkylbiphenyl, terphenyl, partially hydrogenated terphenyl, and silyl.
  • FEC fluoroethylene carbonate
  • DFEC difluoroethylene carbonate
  • oxalates such as lithium bis(oxalate)borate (LiBOB), lithium difluorooxalateborate (LiFOB), and lithium bis(oxalate)difluorophosphate (Li
  • Aromatic compounds such as cyclohexylbenzene, t-butylbenzene, t-amylbenzene, diphenyl ether, and dibenzofuran; partial halides of the above aromatic compounds such as 2-fluorobiphenyl, o-cyclohexylfluorobenzene, and p-cyclohexylfluorobenzene; halogenated anisole compounds such as 2,4-difluoroanisole, 2,5-difluoroanisole, 2,6-difluoroanisole, and 3,5-difluoroanisole; vinylene carbonate, methylvinylene carbonate, ethylvinylene carbonate, and the like.
  • the content of additives contained in the non-aqueous electrolyte is preferably 0.01% by mass or more and 10% by mass or less, more preferably 0.1% by mass or more and 7% by mass or less, even more preferably 0.2% by mass or more and 5% by mass or less, and particularly preferably 0.3% by mass or more and 3% by mass or less, relative to the total mass of the non-aqueous electrolyte.
  • a solid electrolyte may be used as the non-aqueous electrolyte, or a non-aqueous electrolyte solution and a solid electrolyte may be used in combination.
  • the solid electrolyte can be selected from any material that has ionic conductivity, such as lithium, sodium, or calcium, and is solid at room temperature (e.g., 15°C to 25°C).
  • Examples of solid electrolytes include sulfide solid electrolytes, oxide solid electrolytes, nitride solid electrolytes, and polymer solid electrolytes.
  • examples of sulfide solid electrolytes include Li 2 SP 2 S 5 , LiI-Li 2 SP 2 S 5 , and Li 10 Ge-P 2 S 12 .
  • the shape of the energy storage element includes cylindrical batteries, prismatic batteries, flat batteries, coin batteries, and button batteries.
  • Figure 1 shows a storage element 1 as an example of a prismatic battery. Note that this figure is a see-through view of the inside of the container.
  • An electrode body 2 having a positive electrode and a negative electrode wound with a separator sandwiched between them is housed in a prismatic container 3.
  • the positive electrode is electrically connected to a positive electrode terminal 4 via a positive electrode lead 41.
  • the negative electrode is electrically connected to a negative electrode terminal 5 via a negative electrode lead 51.
  • the manufacturing method of the energy storage element of this embodiment can be appropriately selected from known methods.
  • the manufacturing method includes, for example, preparing a positive electrode having positive electrode active material particles manufactured by the above-mentioned method, preparing an electrode assembly, preparing an electrolyte, and housing the electrode assembly and the electrolyte in a container.
  • Preparing the electrode assembly includes preparing a negative electrode, and forming the electrode assembly by stacking or winding the positive electrode and the negative electrode with a separator interposed therebetween.
  • the electrolyte can be placed in the container by any known method. For example, if a non-aqueous electrolyte is used as the electrolyte, the non-aqueous electrolyte can be poured into an inlet formed in the container, and then the inlet can be sealed.
  • the energy storage element of this embodiment can be mounted as an energy storage unit (battery module) comprising a collection of a plurality of energy storage elements in an automobile power source such as an electric vehicle (EV), a hybrid electric vehicle (HEV), or a plug-in hybrid electric vehicle (PHEV), a power source for electronic devices such as a personal computer or a communication terminal, or a power source for power storage, etc.
  • EV electric vehicle
  • HEV hybrid electric vehicle
  • PHEV plug-in hybrid electric vehicle
  • a power source for electronic devices such as a personal computer or a communication terminal
  • a power source for power storage etc.
  • the technology of the present invention is applied to at least one energy storage element included in the energy storage unit.
  • a power storage device includes two or more power storage elements, and includes one or more power storage elements according to one embodiment of the present invention described above (hereinafter referred to as the "second embodiment"). It is sufficient that the technology according to one embodiment of the present invention is applied to at least one power storage element included in the power storage device according to the second embodiment, and the power storage device may include one power storage element according to one embodiment of the present invention described above and one or more power storage elements that are not according to one embodiment of the present invention described above, or may include two or more power storage elements according to one embodiment of the present invention described above.
  • FIG. 2 shows an example of a power storage device 30 according to a second embodiment, which further aggregates power storage units 20, each of which is an aggregation of two or more electrically connected power storage elements 1.
  • the power storage device 30 may include a bus bar (not shown) that electrically connects two or more power storage elements 1, a bus bar (not shown) that electrically connects two or more power storage units 20, etc.
  • the power storage unit 20 or the power storage device 30 may include a status monitoring device (not shown) that monitors the status of one or more power storage elements.
  • the positive electrode for an energy storage device, the electrode body for an energy storage device, and the energy storage device of the present invention are not limited to the above-described embodiments, and various modifications may be made without departing from the spirit of the present invention.
  • the configuration of one embodiment can be added to the configuration of another embodiment, and part of the configuration of one embodiment can be replaced with the configuration of another embodiment or well-known technology.
  • part of the configuration of one embodiment can be deleted.
  • well-known technology can be added to the configuration of one embodiment.
  • the energy storage element is described as being used as a chargeable and dischargeable non-aqueous electrolyte secondary battery (e.g., a lithium-ion secondary battery), but the type, shape, dimensions, capacity, etc. of the energy storage element are arbitrary.
  • the present invention can also be applied to various secondary batteries, electric double layer capacitors, lithium-ion capacitors, and other capacitors.
  • the electrode assembly does not have to include a separator.
  • the positive electrode and negative electrode may be in direct contact with each other, with a non-conductive layer formed on the active material layer of the positive electrode or negative electrode.
  • Example 1 (Preparation of First Active Material Particles) First active material particles were prepared by coating particles of LiFePO4 , a lithium transition metal compound having a polyanion structure, with a carbon material. The carbon material content of the first active material particles was 1.0 mass%. The peak particle diameter (first peak particle diameter) in the particle size distribution diagram obtained by the above method for the first active material particles was 4.5 ⁇ m. The breaking strength of the first active material particles measured by the above method was 55.4 MPa.
  • second active material particles were prepared, which were composed of particles of LiFePO4 , a lithium transition metal compound having a polyanion structure, coated with a carbon material.
  • the carbon material content of the second active material particles was 1.0% by mass.
  • the peak particle diameter (second peak particle diameter) in the particle size distribution diagram obtained by the above method for the second active material particles was 0.67 ⁇ m. That is, the ratio of the first peak particle diameter to the second peak particle diameter was 6.7.
  • the first active material particles and the second active material particles were then mixed to obtain positive electrode active material particles.
  • the ratio of the frequency of the first peak particle diameter to the frequency of the second peak particle diameter was 2.1. Note that the first active material particles and second active material particles used in the examples and comparative examples were all selected from commercially available positive electrode active material particles.
  • a positive electrode mixture paste was prepared using the obtained positive electrode active material particles, acetylene black (AB) as a conductive agent, polyvinylidene fluoride (PVDF) as a binder, and N-methylpyrrolidone (NMP) as a dispersion medium.
  • the mass ratio of the positive electrode active material particles, AB, and PVDF was 90:5:5 in terms of solid content.
  • This positive electrode mixture paste was applied to an aluminum foil positive electrode substrate, dried, and roll-pressed to form a positive electrode active material layer (positive electrode active material mixture), thereby obtaining a positive electrode.
  • the mass per unit area of the positive electrode active material layer was 1.0 g/100 cm 2.
  • the limiting active material density of the positive electrode active material layer was 2.09 g/cm 3.
  • the "limiting active material density” was calculated by multiplying the maximum density of the positive electrode active material layer obtained by roll-pressing by the mass ratio of the positive electrode active material particles in terms of solid content in the positive electrode active material layer.
  • a negative electrode mixture paste was prepared by mixing graphite as a negative electrode active material, acetylene black (AB) as a conductive agent, styrene-butadiene rubber (SBR) as a binder, carboxymethyl cellulose (CMC) as a thickener, and water as a dispersion medium.
  • the mass ratio of graphite to AB to SBR to CMC was 97.1:1.0:0.8:1.0 in terms of solid content.
  • This negative electrode mixture paste was applied to copper foil as a negative electrode substrate, dried, and roll-pressed to form a negative electrode active material layer, thereby obtaining a negative electrode.
  • Non-aqueous electrolyte LiPF6 was dissolved at a concentration of 0.9 mol/ dm3 in a solvent prepared by mixing ethylene carbonate (EC), diethyl carbonate (DEC), and ethyl methyl carbonate (EMC) in a volume ratio of 20:35:45, and 0.3 mass% of vinylene carbonate (VC) was added as an additive to prepare a solution to serve as a nonaqueous electrolyte.
  • EC ethylene carbonate
  • DEC diethyl carbonate
  • EMC ethyl methyl carbonate
  • VC vinylene carbonate
  • Electrode assembly Assembly of energy storage elements
  • the positive electrode, negative electrode, and separator were stacked to prepare an electrode assembly.
  • the obtained electrode assembly was placed in a container, and the nonaqueous electrolyte was then poured into the container, followed by sealing, to obtain the energy storage element of Example 1.
  • Comparative Examples 1 and 5 An energy storage element of Comparative Example 1 was obtained using the same procedure as in Example 1, except that positive electrode active material particles containing only the second active material particles of Example 1 were used. Also, an energy storage element of Comparative Example 5 was obtained using the same procedure as in Example 1, except that positive electrode active material particles containing only the first active material particles having the first peak particle size shown in Table 1 were used. Table 1 shows the limit active material densities of Comparative Examples 1 and 5.
  • Example 9 the positive electrode was also prepared using the same procedures as in Example 1, except that the values shown in Table 1 were obtained. However, cracks occurred in the positive electrode active material layer when the positive electrode mixture paste was applied and dried and then roll-pressed, so the production of the energy storage element was discontinued.
  • Table 1 shows the limit active material density for each Example and Comparative Example. Note that "-" in Table 1 indicates that the limit active material density was not measured.
  • 3 shows particle size distribution diagrams for Comparative Example 2 and Example 3. For Example 3, an inflection point was confirmed in the particle size distribution curve of the particle size distribution diagram between the second peak particle size of 0.61 ⁇ m and the first peak particle size of 4.9 ⁇ m.
  • the 1 kHz alternating current resistance was measured at 25°C using a 1 kHz alternating current impedance meter 10 minutes or more after the end of discharge, and this was taken as the initial ACR.
  • the initial ACR is shown in Table 1.
  • the alternating current resistance (ACR) of each storage element was measured at 1 kHz using a 1 kHz AC impedance meter at 25°C for at least 3 hours after discharge, and this was recorded as the post-cycling ACR.
  • the post-cycling ACR is shown in Table 1.
  • Comparative Example 1 in which no first active material particles were present, or Comparative Example 2, in which the ratio of the frequency at the first peak particle size to the frequency at the second peak particle size was less than 1.0, had a large initial ACR or post-cycling ACR.
  • Comparative Examples 3 and 4 in which the ratio of the frequency at the first peak particle size to the frequency at the second peak particle size was greater than 4.3, or Comparative Example 5, in which no second active material particles were present, had a small critical active material density.
  • Comparative Example 6 in which the first peak particle size was less than 4.0 ⁇ m, had a large initial ACR and post-cycling ACR.
  • Comparative Example 7 in which the fracture strength of the first active material particles was less than 20.0 MPa, had a large post-cycling ACR.
  • Comparative Examples 8 and 9 in which the mass per unit area of the positive electrode active material layer was greater than 2.0 g/100 cm2 , had a small critical active material density or it was impossible to prepare an electrode body without cracking or peeling of the positive electrode active material layer.
  • Examples 1 to 6 in which the first peak particle size was 4.0 ⁇ m or more and the second peak particle size was smaller than the first peak particle size, the first active material particles had a breaking strength of 20.0 MPa or more, the ratio of the frequency at the first peak particle size to the frequency at the second peak particle size was 1.0 or more and 4.3 or less, and the positive electrode active material layer had a mass per unit area of 1.0 g/100 cm2 or more and 2.0 g/100 cm2 or less, had a large critical active material density and small initial ACR and post-cycling ACR.
  • the present invention can be applied to storage elements used as power sources for electronic devices such as personal computers and communication terminals, as well as automobiles.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Power Engineering (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Electrochemistry (AREA)
  • General Chemical & Material Sciences (AREA)
  • Microelectronics & Electronic Packaging (AREA)
  • Inorganic Chemistry (AREA)
  • Battery Electrode And Active Subsutance (AREA)

Abstract

Un aspect de la présente invention concerne une électrode positive d'élément de stockage d'énergie comprenant un matériau de base et une couche de matériau actif d'électrode positive qui est stratifiée sur le matériau de base et comprend des particules de matériau actif d'électrode positive. Les particules de matériau actif d'électrode positive contiennent des premières particules de matériau actif et des secondes particules de matériau actif qui ont des diamètres de particule différents. Sur un diagramme de distribution de taille de particule pour les particules de matériau actif d'électrode positive, sur lequel l'axe horizontal représente le diamètre de particule (μm) et l'axe vertical la fréquence (%) en volume, un premier diamètre de particule de pic représentant les premières particules de matériau actif est supérieur ou égal à 4,0 μm, un second diamètre de particule de pic représentant les secondes particules de matériau actif est inférieur au premier diamètre de particule de pic, et le rapport de la fréquence (%) pour le premier diamètre de particule de pic à la fréquence (%) pour le second diamètre de particule de pic est compris entre 1,0 et 4,3. La résistance à la rupture des premières particules de matériau actif est supérieure ou égale à 20,0 MPa, et la masse par unité de surface de la couche de matériau actif d'électrode positive est supérieure ou égale à 1,0 g/100 cm2 mais inférieure ou égale à 2,0 g/100 cm2.
PCT/JP2025/015270 2024-05-20 2025-04-18 Électrode positive d'élément de stockage d'énergie, corps d'électrode, élément de stockage d'énergie et dispositif de stockage d'énergie Pending WO2025243748A1 (fr)

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Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2009032410A (ja) * 2007-07-24 2009-02-12 Hitachi Vehicle Energy Ltd リチウム二次電池
JP2017216243A (ja) * 2015-11-13 2017-12-07 日立金属株式会社 リチウムイオン二次電池用正極材料及びリチウムイオン二次電池
JP2018095529A (ja) * 2016-12-15 2018-06-21 新日本電工株式会社 リチウムマンガン複合酸化物粉末およびその製造方法ならびに非水電解質二次電池用正極
WO2020194510A1 (fr) * 2019-03-26 2020-10-01 株式会社 東芝 Électrode, batterie à électrolyte non aqueux, et bloc-batterie

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2009032410A (ja) * 2007-07-24 2009-02-12 Hitachi Vehicle Energy Ltd リチウム二次電池
JP2017216243A (ja) * 2015-11-13 2017-12-07 日立金属株式会社 リチウムイオン二次電池用正極材料及びリチウムイオン二次電池
JP2018095529A (ja) * 2016-12-15 2018-06-21 新日本電工株式会社 リチウムマンガン複合酸化物粉末およびその製造方法ならびに非水電解質二次電池用正極
WO2020194510A1 (fr) * 2019-03-26 2020-10-01 株式会社 東芝 Électrode, batterie à électrolyte non aqueux, et bloc-batterie

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