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WO2025154586A1 - Dispositif de stockage d'énergie et procédé permettant de fabriquer un dispositif de stockage d'énergie - Google Patents

Dispositif de stockage d'énergie et procédé permettant de fabriquer un dispositif de stockage d'énergie

Info

Publication number
WO2025154586A1
WO2025154586A1 PCT/JP2025/000247 JP2025000247W WO2025154586A1 WO 2025154586 A1 WO2025154586 A1 WO 2025154586A1 JP 2025000247 W JP2025000247 W JP 2025000247W WO 2025154586 A1 WO2025154586 A1 WO 2025154586A1
Authority
WO
WIPO (PCT)
Prior art keywords
negative electrode
active material
material layer
electrode active
positive electrode
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Pending
Application number
PCT/JP2025/000247
Other languages
English (en)
Japanese (ja)
Inventor
寛 岩田
裕樹 市川
祐樹 杉本
佑樹 石野
皓大 馬場
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Toyota Industries Corp
Original Assignee
Toyota Industries Corp
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Toyota Industries Corp filed Critical Toyota Industries Corp
Publication of WO2025154586A1 publication Critical patent/WO2025154586A1/fr
Pending legal-status Critical Current
Anticipated expiration legal-status Critical

Links

Classifications

    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/056—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes
    • H01M10/0564—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes the electrolyte being constituted of organic materials only
    • H01M10/0566—Liquid materials
    • H01M10/0567—Liquid materials characterised by the additives
    • 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
    • H01M10/056—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes
    • H01M10/0564—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes the electrolyte being constituted of organic materials only
    • H01M10/0566—Liquid materials
    • H01M10/0568—Liquid materials characterised by the solutes
    • 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
    • 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
    • H01M4/133—Electrodes based on carbonaceous material, e.g. graphite-intercalation compounds or CFx
    • 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
    • H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
    • H01M4/583—Carbonaceous material, e.g. graphite-intercalation compounds or CFx
    • H01M4/587—Carbonaceous material, e.g. graphite-intercalation compounds or CFx for inserting or intercalating light metals
    • 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
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • 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 disclosure relates to an energy storage device and a method for manufacturing an energy storage device.
  • Patent Document 1 discloses a flat-type storage device constructed by stacking a number of individually manufactured storage cells in series.
  • the storage cell includes a positive electrode having a positive electrode active material layer formed in the center of one side of a foil-shaped positive electrode collector, a negative electrode having a negative electrode active material layer formed in the center of one side of a foil-shaped negative electrode collector, the negative electrode being arranged so that the negative electrode active material layer faces the positive electrode active material layer of the positive electrode, and a separator arranged between the positive electrode and the negative electrode.
  • the above-mentioned storage cell includes a seal portion disposed between the positive electrode and the negative electrode and on the outer periphery side of the positive electrode active material layer and the negative electrode active material layer.
  • the seal portion maintains the distance between the positive electrode collector and the negative electrode collector to prevent short circuits between the collectors, and also provides a liquid-tight seal between the positive electrode collector and the negative electrode collector to form an enclosed space that contains a liquid electrolyte between the positive electrode collector and the negative electrode collector.
  • a power storage device in one aspect of the present disclosure, includes a positive electrode having a positive electrode active material layer, a negative electrode having a negative electrode active material layer, a separator disposed between the positive electrode and the negative electrode, and a liquid electrolyte disposed between the positive electrode and the negative electrode.
  • the negative electrode active material layer has a basis weight of 200 g/m 2 or more.
  • the negative electrode active material layer includes graphite particles, carbon fibers, and a negative electrode binder.
  • the liquid electrolyte includes lithium difluorophosphate and vinylene carbonate.
  • the carbon fiber includes a fiber bundle formed by bundling a plurality of single-walled carbon nanotubes, and that the fiber bundle is in contact with a plurality of the graphite particles across the plurality of the graphite particles.
  • the assembly process includes an electrode formation process in which the negative electrode active material layer is formed by applying and drying a negative electrode mixture to the surface of a negative electrode current collector, and the negative electrode mixture preferably includes graphite particles, carbon fibers, a negative electrode binder, and a dispersion medium, and has a solids concentration of 65 mass% or less.
  • FIG. 1 is a cross-sectional view of the electricity storage device.
  • FIG. 2 is a schematic diagram showing the state of graphite particles and carbon fibers in the negative electrode active material layer.
  • FIG. 3 is an explanatory diagram of the activation step.
  • FIGS. 4A to 4D are schematic diagrams showing the process of forming an SEI film on graphite particles.
  • FIG. 5 is a graph showing the results of a storage test for measuring the amount of gas generated.
  • the power storage device 10 shown in Fig. 1 is a power storage module used in batteries of various vehicles such as forklifts, hybrid vehicles, and electric vehicles.
  • the power storage device 10 is, for example, a lithium ion secondary battery.
  • the power storage device 10 may be an electric double layer capacitor. In this embodiment, the case where the power storage device 10 is a lithium ion secondary battery is illustrated.
  • the energy storage device 10 includes a cell stack 30 (laminate) in which a plurality of energy storage cells 20 are stacked in a stacking direction.
  • the stacking direction of the plurality of energy storage cells 20 will be simply referred to as the stacking direction.
  • Each energy storage cell 20 includes a positive electrode 21, a negative electrode 22, a separator 23, and a seal portion 24.
  • the positive electrode 21 includes a positive electrode current collector 21a and a positive electrode active material layer 21b provided on a first surface 21a1 of the positive electrode current collector 21a.
  • the positive electrode active material layer 21b is formed in the center of the first surface 21a1 of the positive electrode collector 21a.
  • the peripheral portion of the first surface 21a1 of the positive electrode collector 21a in the plan view is a positive electrode uncoated portion 21c where the positive electrode active material layer 21b is not provided.
  • the positive electrode uncoated portion 21c is disposed so as to surround the periphery of the positive electrode active material layer 21b in the plan view.
  • the negative electrode 22 includes a negative electrode collector 22a and a negative electrode active material layer 22b provided on the first surface 22a1 of the negative electrode collector 22a.
  • the negative electrode active material layer 22b is formed in the center of the first surface 22a1 of the negative electrode collector 22a.
  • the peripheral portion of the first surface 22a1 of the negative electrode collector 22a is a negative electrode uncoated portion 22c where the negative electrode active material layer 22b is not provided.
  • the negative electrode uncoated portion 22c is arranged to surround the periphery of the negative electrode active material layer 22b in a plan view.
  • the positive electrode 21 and the negative electrode 22 are arranged such that the positive electrode active material layer 21b and the negative electrode active material layer 22b face each other in the stacking direction. In other words, the direction in which the positive electrode 21 and the negative electrode 22 face each other coincides with the stacking direction.
  • the negative electrode active material layer 22b is formed to be slightly larger than the positive electrode active material layer 21b, and in a plan view seen from the stacking direction, the entire formation area of the positive electrode active material layer 21b is located within the formation area of the negative electrode active material layer 22b.
  • the positive electrode collector 21a has a second surface 21a2 located opposite the first surface 21a
  • the negative electrode collector 22a has a second surface 22a2 located opposite the first surface 22a1.
  • the cell stack 30 has a structure in which a plurality of storage cells 20 are stacked such that the second surface 21a2 of the positive electrode collector 21a and the second surface 22a2 of the negative electrode collector 22a are in contact with each other. As a result, the plurality of storage cells 20 that constitute the cell stack 30 are connected in series.
  • a pseudo bipolar electrode 25 is formed in which the mutually contacting positive electrode collector 21a and negative electrode collector 22a of two storage cells 20 adjacent to each other in the stacking direction are regarded as a single collector.
  • the pseudo bipolar electrode 25 includes a collector having a structure in which the positive electrode collector 21a and the negative electrode collector 22a are stacked, a positive electrode active material layer 21b formed on one surface of the collector, and a negative electrode active material layer 22b formed on the other surface.
  • the positive electrode collector 21a and the negative electrode collector 22a may form a bipolar collector in which the second surface 21a2 of the positive electrode collector 21a and the second surface 22a2 of the negative electrode collector 22a are joined together.
  • the positive electrode 21 and the negative electrode 22 form a bipolar electrode 25 having one bipolar collector in which the positive electrode collector 21a and the negative electrode collector 22a are joined together.
  • the bipolar electrode 25 is joined between the surface of the positive electrode collector 21a of the positive electrode 21 constituting one of the adjacent storage cells 20 opposite the first surface 21a1, and the surface of the negative electrode collector 22a of the negative electrode 22 constituting the other of the adjacent storage cells 20 opposite the first surface 22a1.
  • the separator 23 is, for example, a porous sheet or nonwoven fabric containing a polymer that absorbs and retains liquid electrolyte.
  • materials that constitute the separator 23 include polypropylene, polyethylene, polyolefin, and polyester.
  • the separator 23 may have a single-layer structure or a multi-layer structure.
  • the multi-layer structure may have, for example, an adhesive layer, a ceramic layer as a heat-resistant layer, etc.
  • the seal portion 24 is disposed between the first surface 22a1 of the positive electrode collector 21a of the positive electrode 21 and the first surface 22a1 of the negative electrode collector 22a of the negative electrode 22, and is disposed on the outer periphery side of the positive electrode active material layer 21b and the negative electrode active material layer 22b, and is adhered to both the positive electrode collector 21a and the negative electrode collector 22a.
  • the seal portion 24 prevents short circuits between the collectors by insulating between the positive electrode collector 21a and the negative electrode collector 22a.
  • the sealing portion 24 extends along the peripheral portions of the positive electrode collector 21a and the negative electrode collector 22a, and is formed in a frame shape surrounding the periphery of the positive electrode active material layer 21b and the negative electrode active material layer 22b.
  • the sealing portion 24 is disposed between the positive electrode uncoated portion 21c of the first surface 21a1 of the positive electrode collector 21a and the negative electrode uncoated portion 22c of the first surface 22a1 of the negative electrode collector 22a.
  • a sealed space S is formed, surrounded by a frame-shaped seal portion 24, a positive electrode 21, and a negative electrode 22.
  • a separator 23 and a liquid electrolyte are contained in the sealed space S.
  • the peripheral portion of the separator 23 is embedded in the seal portion 24.
  • the sealing portion 24 can prevent the liquid electrolyte contained in the sealed space S from permeating to the outside by sealing the sealed space S between the positive electrode 21 and the negative electrode 22.
  • the sealing portion 24 can also prevent moisture from entering the sealed space S from the outside of the energy storage device 10.
  • the sealing portion 24 can prevent gas generated from the positive electrode 21 or the negative electrode 22 due to, for example, a charge/discharge reaction, from leaking to the outside of the energy storage device 10.
  • the seal portion 24 of each storage cell 20 has an outer peripheral portion that extends outward beyond the edges of the positive electrode collector 21a and the negative electrode collector 22a. When viewed from the stacking direction, the outer peripheral portion protrudes beyond the edges of the positive electrode collector 21a and the negative electrode collector 22a in a direction perpendicular to the stacking direction. Adjacent storage cells 20 in the stacking direction are integrated by bonding the outer peripheral portions of their respective seal portions 24 together. Methods for bonding adjacent seal portions 24 together include, for example, known welding methods such as heat welding, ultrasonic welding, or infrared welding.
  • the energy storage device 10 includes a pair of conductive bodies consisting of a positive electrode conductive plate 40 and a negative electrode conductive plate 50, which are arranged to sandwich the cell stack 30 in the stacking direction of the cell stack 30.
  • the positive electrode conductive plate 40 and the negative electrode conductive plate 50 are each made of a material with excellent electrical conductivity.
  • the positive electrode current-carrying plate 40 is electrically connected to the second surface 21a2 of the positive electrode current collector 21a of the positive electrode 21 arranged on the outermost side at one end in the stacking direction.
  • the negative electrode current-carrying plate 50 is electrically connected to the second surface 22a2 of the negative electrode current collector 22a of the negative electrode 22 arranged on the outermost side at the other end in the stacking direction.
  • the energy storage device 10 is charged and discharged through terminals provided on the positive electrode current-carrying plate 40 and the negative electrode current-carrying plate 50.
  • the material constituting the positive electrode current-carrying plate 40 may be, for example, the same material as the material constituting the positive electrode current-carrying plate 21a.
  • the positive electrode current-carrying plate 40 may be made of a metal plate thicker than the positive electrode current-carrying plate 21a used in the cell stack 30.
  • the material constituting the negative electrode current-carrying plate 50 may be, for example, the same material as the material constituting the negative electrode current-carrying plate 22a.
  • the negative electrode current-carrying plate 50 may be made of a metal plate thicker than the negative electrode current-carrying plate 22a used in the cell stack 30.
  • the negative electrode collector 22a is a chemically inactive electric conductor for continuously passing a current through the negative electrode active material layer 22b during discharging or charging of the lithium ion secondary battery.
  • An example of the negative electrode collector 22a is a copper collector whose surface, which becomes the first surface 22a1, is made of copper.
  • the copper collector may be a simple substance entirely made of copper, or may be a composite having a portion made of copper and a portion made of a material other than copper. Examples of the simple substance include copper foil such as electrolytic copper foil. Examples of the composite include a multilayer structure in which the layer constituting the first surface 22a1 is a copper layer, and a substrate whose surface including the first surface 22a1 is coated with a copper film.
  • Examples of the material other than copper include metal materials, conductive resin materials, and conductive inorganic materials.
  • Examples of the metal materials include aluminum, nickel, titanium, and stainless steel (e.g., SUS304, SUS316, SUS301, SUS304, etc., as specified in JIS G 4305:2015).
  • Examples of the conductive resin materials include resins in which conductive polymer materials or non-conductive polymer materials are added with conductive fillers as necessary.
  • the negative electrode collector 22a may be in the form of, for example, a foil, a sheet, or a film.
  • the thickness of the negative electrode collector 22a is, for example, 1 to 100 ⁇ m.
  • the negative electrode active material layer 22b contains graphite particles, carbon fibers, and a negative electrode binder.
  • the graphite particles are contained in the negative electrode active material layer 22b as a negative electrode active material capable of absorbing and releasing charge carriers such as lithium ions.
  • Examples of the graphite constituting the graphite particles include natural graphite, artificial graphite, hard carbon (hardly graphitizable carbon), and soft carbon (easily graphitizable carbon).
  • Examples of the artificial graphite include highly oriented graphite and mesocarbon microbeads.
  • the average particle diameter (D50) of the graphite particles is, for example, 3 ⁇ m or more, preferably 5 ⁇ m or more, and more preferably 10 ⁇ m or more.
  • the average particle diameter (D50) of the graphite particles is, for example, 30 ⁇ m or less, preferably 25 ⁇ m or less, and more preferably 20 ⁇ m or less.
  • the average particle diameter (D50) of the graphite particles can be measured, for example, using a laser diffraction particle size analyzer.
  • the graphite particle content in the negative electrode active material layer 22b is, for example, 93% by mass or more, preferably 95% by mass or more, and more preferably 97% by mass or more.
  • the graphite particle content in the negative electrode active material layer 22b is, for example, 99% by mass or less, preferably 98% by mass or less, and more preferably 97.5% by mass or less.
  • the second layer M2 is formed on the surface of the first layer M1 and covers a part or the whole of the surface of the first layer M1.
  • the second layer M2 is composed of a decomposition product of vinylene carbonate contained in the liquid electrolyte.
  • the SEI film M functions as a protective film that suppresses contact between the graphite particles P and the liquid electrolyte. The formation mechanism of the SEI film M will be described later in detail.
  • the carbon fibers are included in the negative electrode active material layer 22b as a conductive assistant for enhancing electrical conductivity.
  • the carbon fibers are, for example, carbon nanotubes.
  • Carbon nanotubes can be broadly divided into two types: single-walled carbon nanotubes and multi-walled carbon nanotubes.
  • a single-walled carbon nanotube is a cylindrical body in which a single graphene sheet is seamlessly rolled up.
  • a multi-walled carbon nanotube is a composite in which a plurality of single-walled carbon nanotubes with different diameters are contained within one single-walled carbon nanotube.
  • the carbon fibers included in the negative electrode active material layer 22b are preferably single-walled carbon nanotubes.
  • the fiber length and fiber diameter of the carbon fiber are not particularly limited.
  • the fiber length of the carbon fiber is, for example, 5 ⁇ m or more and 1000 ⁇ m or less.
  • the fiber diameter of the carbon fiber is, for example, 1 nm or more and 20 nm or less.
  • the fiber length and fiber diameter of the carbon fiber can be measured using, for example, an electron microscope such as a scanning electron microscope (SEM) or a transmission electron microscope (TEM).
  • the carbon fiber content in the negative electrode active material layer 22b is, for example, 0.005% by mass or more and 0.05% by mass or less.
  • An example of a preferred state of the graphite particles and carbon fibers in the negative electrode active material layer 22b will be described with reference to Fig. 2. In Fig. 2, the negative electrode binder and other components described later are omitted.
  • the negative electrode active material layer 22b includes graphite particles P and fiber bundles F.
  • the fiber bundles F are fiber bundles formed by bundling a plurality of single-walled carbon nanotubes.
  • the number of single-walled carbon nanotubes constituting one fiber bundle F is, for example, several to several tens of single-walled carbon nanotubes.
  • the negative electrode active material layer 22b may include a single single-walled carbon nanotube that does not form a fiber bundle F.
  • single-walled carbon nanotubes which are carbon fibers, are dispersed in fiber bundles F and are arranged in a mesh-like pattern (e.g., spider web-like pattern) as a whole.
  • the fiber bundles F are in contact with multiple graphite particles P.
  • the state in which the fiber bundles F are in contact with multiple graphite particles means a state in which 50% or more of the fiber bundles F, based on the number of bundles, are in contact with multiple graphite particles.
  • the fiber length of the single-walled carbon nanotubes is preferably, for example, 5 ⁇ m or more and 50 ⁇ m or less.
  • the fiber length is more preferably 10 ⁇ m or more, and even more preferably 15 ⁇ m or more.
  • the fiber length is more preferably 40 ⁇ m or less, and even more preferably 30 ⁇ m or less.
  • the ratio of the fiber length to the average particle size of the graphite particles P is preferably, for example, greater than 1. The ratio is, for example, 20 or less.
  • the negative electrode binder examples include fluorine-containing resins such as polyvinylidene fluoride, polytetrafluoroethylene, and fluorine rubber, thermoplastic resins such as polypropylene and polyethylene, imide resins such as polyimide and polyamideimide, alkoxysilyl group-containing resins, acrylic resins such as poly(meth)acrylic acid, styrene-butadiene rubber, carboxymethyl cellulose, alginates such as sodium alginate and ammonium alginate, water-soluble cellulose ester crosslinked bodies, and starch-acrylic acid graft polymers.
  • the negative electrode binder may be used alone or in combination.
  • the solvent or dispersion medium used to dissolve or disperse the negative electrode binder include water and N-methyl-2-pyrrolidone.
  • the negative electrode active material layer 22b may further contain other components other than the graphite particles, carbon fibers, and negative electrode binder as necessary.
  • the other components include a negative electrode active material other than graphite particles, a conductive assistant other than carbon fibers, an electrolyte (polymer matrix, ion-conductive polymer, liquid electrolyte, etc.), and an electrolyte supporting salt (lithium salt) for increasing ion conductivity.
  • Anode active materials other than graphite particles include, for example, silicon, tin, and other elements that can be alloyed with lithium. There are no particular limitations on the anode active material, and any element, alloy, or compound that can absorb and release charge carriers such as lithium ions can be used.
  • Examples of the conductive assistant other than carbon fiber include acetylene black, carbon black, and graphite.
  • the types and compounding ratios of other components contained in the negative electrode active material layer 22b are not particularly limited, and conventionally known knowledge about lithium ion secondary batteries can be appropriately referred to.
  • the thickness of the negative electrode active material layer 22b is, for example, 0.2 mm or more, preferably 0.25 mm or more, and more preferably 0.3 mm or more.
  • the thickness of the negative electrode active material layer 22b is, for example, 0.4 mm or less.
  • the negative electrode active material layer 22b has a porous shape that allows the liquid electrolyte to infiltrate.
  • the negative electrode active material layer 22b has a surface area of, for example, 250 mm 2 or more and 1350 mm 2 or less.
  • the surface area of the negative electrode active material layer 22b can be calculated as the product of the specific surface area of the negative electrode active material layer 22b and the total mass of the negative electrode active material layer 22b.
  • the specific surface area of the negative electrode active material layer 22b means the BET surface area per unit mass of the negative electrode active material layer 22b measured by N2 adsorption using the BET method.
  • the total mass of the negative electrode active material layer 22b can be calculated as the product of the basis weight of the negative electrode active material layer 22b and the area of the range in which the negative electrode active material layer 22b is formed on the negative electrode current collector 22a.
  • the method for forming the negative electrode active material layer 22b on the surface of the negative electrode current collector 22a is not particularly limited, and a conventionally known method such as a roll coating method can be used.
  • a coating may be provided on the surface of the negative electrode current collector 22a.
  • An example of the coating is a heat-resistant layer that is provided to improve the thermal stability of the negative electrode 22.
  • the positive electrode collector 21a is a chemically inactive electric conductor for continuously passing a current through the positive electrode active material layer 21b during discharging or charging of the lithium ion secondary battery.
  • An example of the positive electrode collector 21a is an aluminum collector whose surface, which becomes the first surface 21a1, is made of aluminum.
  • the aluminum collector may be a single body entirely made of aluminum, or a composite having a portion made of aluminum and a portion made of a material other than aluminum. Examples of the single body include aluminum foil such as rolled aluminum foil. Examples of the composite include a multilayer structure in which the layer constituting the first surface 21a1 is an aluminum layer, and a substrate whose surface including the first surface 21a1 is coated with an aluminum film.
  • An example of the positive electrode active material layer 21b includes a positive electrode binder.
  • the positive electrode binder include those exemplified above as negative electrode binders.
  • the positive electrode binders may be used alone or in combination.
  • the solvent or dispersion medium used to dissolve or disperse the positive electrode binder include water and N-methyl-2-pyrrolidone.
  • a positive electrode binder is an aqueous binder.
  • An aqueous binder is a binder that is soluble or dispersible in an aqueous solvent, and is used by mixing it with a positive electrode active material in a dispersed or dissolved state in the aqueous solvent.
  • aqueous binder there are no particular limitations on the aqueous binder, and any conventionally known material can be used as an aqueous binder contained in the positive electrode active material layer of a lithium ion secondary battery.
  • Examples of aqueous binders include those exemplified above as negative electrode binders.
  • the positive electrode active material layer 21b may further contain, as necessary, a conductive assistant to increase electrical conductivity, an electrolyte (polymer matrix, ion-conductive polymer, liquid electrolyte, etc.), an electrolyte supporting salt (lithium salt) to increase ionic conductivity, etc.
  • the conductive assistant is added to increase the conductivity of the positive electrode 21.
  • Examples of conductive assistants include acetylene black, carbon black, graphite, and carbon nanotubes.
  • the types and compounding ratios of the components contained in the positive electrode active material layer 21b are not particularly limited, and conventionally known knowledge about lithium ion secondary batteries may be referred to as appropriate.
  • the basis weight and thickness of the positive electrode active material layer 21b are not particularly limited, and conventionally known knowledge about lithium ion secondary batteries may be appropriately referred to.
  • the basis weight of the positive electrode active material layer 21b is, for example, 500 g/m 2 or more and 800 g/m 2 or less.
  • the thickness of the positive electrode active material layer 21b is, for example, 0.3 mm or more and 0.4 mm or less.
  • the method for forming the positive electrode active material layer 21b on the surface of the positive electrode collector 21a is not particularly limited, and a conventionally known method such as a roll coating method can be used.
  • a coating may be provided on the surface of the positive electrode collector 21a.
  • An example of the coating is a heat-resistant layer that is provided to improve the thermal stability of the positive electrode 21.
  • non-aqueous electrolyte solution is a non-aqueous electrolyte solution obtained by adding a specific additive to a solution in which the lithium salt is dissolved in the non-aqueous solvent at a concentration of about 0.5 mol/L to 2.5 mol/L.
  • the liquid electrolyte contains lithium difluorophosphate (LiPO 2 F 2 ), which is one of the specific additives.
  • the content of lithium difluorophosphate in the liquid electrolyte is set according to the size of the surface area of the negative electrode active material layer 22b arranged in the same sealed space S as the liquid electrolyte.
  • the content of lithium difluorophosphate in the liquid electrolyte per surface area of the negative electrode active material layer 22b is, for example, 3 mg/m 2 or more, preferably 4 mg/m 2 or more, and more preferably 5 mg/m 2 or more.
  • the content of lithium difluorophosphate per surface area of the negative electrode active material layer 22b is, for example, 20 mg/m 2 or less, preferably 15 mg/m 2 or less, and more preferably 9 mg/m 2 or less.
  • the liquid electrolyte contains vinylene carbonate (1,3-dioxol-2-one), which is one of the specific additives.
  • the content of vinylene carbonate in the liquid electrolyte is set according to the size of the surface area of the negative electrode active material layer 22b disposed in the same sealed space S as the liquid electrolyte.
  • the content of vinylene carbonate in the liquid electrolyte per surface area of the negative electrode active material layer 22b is, for example, 3 mg/m 2 or more, preferably 4 mg/m 2 or more, and more preferably 5 mg/m 2 or more.
  • the content of vinylene carbonate per surface area of the negative electrode active material layer 22b is, for example, 20 mg/m 2 or less, preferably 15 mg/m 2 or less, and more preferably 9 mg/m 2 or less.
  • the ratio of the content of lithium difluorophosphate per surface area of the negative electrode active material layer 22b to the content of vinylene carbonate per surface area of the negative electrode active material layer 22b is, for example, 0.5 to 2.0.
  • the concentration of vinylene carbonate in the liquid electrolyte is, for example, 0.3% by mass to 2.0% by mass, and preferably 1.0% by mass to 2.0% by mass.
  • the liquid electrolyte preferably contains a cyclic sulfonate ester, which is one of the specific additives described above.
  • the cyclic sulfonate ester is an optional specific additive described above. Therefore, the liquid electrolyte may be configured not to contain a cyclic sulfonate ester.
  • Examples of the cyclic sulfonate ester include propane sultone and propene sultone.
  • the content of the cyclic sulfonate ester in the liquid electrolyte is set according to the size of the surface area of the negative electrode active material layer 22b arranged in the same sealed space S as the liquid electrolyte.
  • the content of the cyclic sulfonate ester in the liquid electrolyte per surface area of the negative electrode active material layer 22b is, for example, 0.6 mg/m 2 or more, preferably 0.8 mg/m 2 or more, and more preferably 1 mg/m 2 or more.
  • the content of the cyclic sulfonate ester per surface area of the negative electrode active material layer 22b is, for example, 20 mg/m 2 or less, preferably 15 mg/m 2 or less, and more preferably 9 mg/m 2 or less.
  • the ratio of the content of the cyclic sulfonate ester per surface area of the negative electrode active material layer 22b to the content of the vinylene carbonate per surface area of the negative electrode active material layer 22b is, for example, 0.1 to 2.0, and preferably 0.5 to 2.0.
  • the concentration of the cyclic sulfonate ester in the liquid electrolyte is, for example, 0.1 to 2.0% by mass, and preferably 1.0 to 2.0% by mass.
  • the manufacturing method of the power storage device 10 includes an assembly step of assembling a battery assembly and an activation step of activating the assembled battery assembly.
  • the battery assembly means the power storage device 10 before the activation step.
  • a positive electrode is formed by forming a positive electrode active material layer 21b on the surface of the positive electrode collector 21a, and a negative electrode is formed by forming a negative electrode active material layer 22b on the surface of the negative electrode collector 22a.
  • liquid electrolyte is injected into the sealed space S inside the assembly unit through an injection port provided in part of the seal portion 24, and the injection port is then sealed. This forms a single assembly unit that constitutes one storage cell 20.
  • the positive electrode current-carrying plate 40 is stacked and fixed in an electrically connected state to the second surface 21a2 of the positive electrode current collector 21a of the positive electrode 21 arranged on the outermost side at one end of the stacking direction.
  • the negative electrode current-carrying plate 50 is stacked and fixed in an electrically connected state to the second surface 22a2 of the negative electrode current collector 22a of the negative electrode 22 arranged on the outermost side at the other end of the stacking direction.
  • a battery assembly is formed through the above steps.
  • the initial charging process includes a first charging process in which charging is performed up to a first voltage, and a second charging process in which charging is performed from the first voltage to a target voltage.
  • the first charging process and the second charging process have different charging rates.
  • the charging rate of the first charging process is lower than the charging rate of the second charging process.
  • the charging rate of the first charging step is, for example, 0.01 C or less, and preferably 0.0075 C or less.
  • the charging rate of the first charging step is, for example, 0.001 C or more, and preferably 0.0025 C or more.
  • the charging rate of the second charging step is higher than the charging rate of the first charging step.
  • the charging rate of the second charging step is, for example, greater than 0.01 C, and preferably 0.1 C or more.
  • the charging rate of the second charging step is, for example, 0.5 C or less.
  • the time required for the initial charging step can be shortened. Also, by setting the first voltage to a low value within the range above the voltage at which lithium difluorophosphate and vinylene carbonate decompose, the time required for the initial charging step can be shortened. In other words, in this case, the period during which charging is performed at the low charge rate in the first charging step becomes relatively shorter, while the period during which charging is performed at the high charge rate in the second charging step becomes relatively longer. As a result, the time required for the initial charging step can be shortened.
  • the aging process is a process in which the battery assembly in a high-voltage state after the initial charging process is held in a high-temperature environment for a predetermined period of time.
  • the temperature in the aging process is, for example, 55°C or higher and 70°C or lower.
  • the duration of the aging process is, for example, 20 hours or higher and 50 hours or lower.
  • the weight of the negative electrode active material layer 22b is adjusted to 200 g/m 2 or more.
  • a problem occurs in that the amount of gas generated from the electrode increases significantly.
  • the weight of the negative electrode active material layer is large, the amount of electrons released from the negative electrode due to self-discharge increases.
  • the electrons released from the negative electrode react with the liquid electrolyte at the negative electrode to generate gas.
  • the electrons released from the negative electrode reach the positive electrode through the liquid electrolyte and react with water contained in the positive electrode active material layer of the positive electrode to generate gas at the positive electrode. Therefore, when the weight of the negative electrode active material layer is increased, the amount of electrons released from the negative electrode due to self-discharge increases, and as a result, the amount of gas generated from the electrode increases significantly.
  • graphite particles are used as the negative electrode active material constituting the negative electrode active material layer 22b, and lithium difluorophosphate and vinylene carbonate are contained in the liquid electrolyte.
  • an SEI film M consisting of decomposition products of lithium difluorophosphate and vinylene carbonate is formed on the surface of the graphite particles P.
  • the SEI film M derived from lithium difluorophosphate and vinylene carbonate functions as a protective film that suppresses contact between the graphite particles P and the liquid electrolyte.
  • the power storage device 10 includes a positive electrode 21 having a positive electrode active material layer 21b, a negative electrode 22 having a negative electrode active material layer 22b, a separator 23 disposed between the positive electrode 21 and the negative electrode 22, and a liquid electrolyte disposed between the positive electrode 21 and the negative electrode 22, and the negative electrode active material layer 22b has a basis weight of 200 g/m 2 or more.
  • the negative electrode active material layer 22b includes graphite particles, carbon fibers, and a negative electrode binder.
  • the liquid electrolyte includes lithium difluorophosphate and vinylene carbonate.
  • the positive electrode active material layer 21b includes a positive electrode active material and a positive electrode binder.
  • the positive electrode binder is a water-based binder.
  • the positive electrode active material layer 21b containing the aqueous binder is formed using a positive electrode mixture containing water, and therefore is likely to contain water such as crystal water. Therefore, it can be said that the positive electrode active material layer 21b containing the aqueous binder is likely to generate gas.
  • the nonaqueous solvent contained in the liquid electrolyte is an ester. Esters are more susceptible to gas generation due to self-discharge than other solvents such as carbonates, etc.
  • the first charging step charging is performed at a relatively low charging rate.
  • This makes it possible to more reliably form an SEI film having a first layer M1 made of a decomposition product of lithium difluorophosphate and a second layer M2 made of a decomposition product of vinylene carbonate on the surface of the graphite particles P constituting the negative electrode current collector 22a. Therefore, the effect of reducing the amount of gas generation based on the function of the SEI film M that suppresses contact between the graphite particles P and the liquid electrolyte can be more significantly obtained.
  • charging is performed at a relatively high charging rate. This makes it possible to shorten the time required for the initial charging step.
  • the assembly process includes an electrode formation process in which a negative electrode mixture is applied to the surface of the negative electrode current collector 22a and then dried to form a negative electrode active material layer 22b.
  • the negative electrode mixture contains graphite particles, carbon fibers, a negative electrode binder, and a dispersion medium, and has a solid content concentration of 65 mass% or less.
  • planar shapes of the positive electrode current collector 21a and the positive electrode active material layer 21b are not particularly limited. They may be polygonal, such as rectangular, or may be circular or elliptical. The same is true for the negative electrode current collector 22a and the negative electrode active material layer 22b.
  • a charge/discharge process may be performed as necessary.
  • the charge/discharge process is performed, for example, before or after the aging process.
  • the charge/discharge process is a process in which multiple cycles of charge/discharge are performed, with one cycle consisting of discharge and charge.
  • multiple cycles of charge/discharge are performed, with one cycle consisting of discharge to SOC 0% and charge to SOC 15%.
  • multiple cycles of charge/discharge are performed, with one cycle consisting of discharge to SOC 0% and charge to SOC 100%.
  • the liquid electrolyte used was prepared by dissolving LiN( FSO2 ) 2 to a concentration of 1.4 M in a mixed solvent of ethylene carbonate and methyl propionate in a volume ratio of 15:85, and adding the additives shown in Table 1.
  • a liquid electrolyte was used to which lithium difluorophosphate and vinylene carbonate were added as additives.
  • the numerical value in each additive column indicates the content of the additive per surface area of the negative electrode active material layer 22b, and the numerical value in parentheses below indicates the concentration of the additive in the liquid electrolyte.
  • Comparative Examples 1 to 2 Except for the difference in the additives added to the liquid electrolyte, electricity storage devices of Comparative Examples 1 and 2 were obtained in the same manner as in Example 1. As shown in Table 1, a liquid electrolyte to which vinylene carbonate was added was used in Comparative Example 1. A liquid electrolyte to which vinylene carbonate and lithium difluoro(oxalato)borate were added was used in Comparative Example 2. The content of each additive in the liquid electrolyte is as shown in Table 1.
  • the additives shown in Table 1 are as follows.
  • DFOB Lithium difluoro(oxalato)borate (measurement of gas generation amount)
  • Each of the storage devices of the examples and comparative examples was charged to 2.7 V (first voltage) at a constant current of 0.005 C. Then, the storage device was charged to 3.75 V (target voltage) at a constant current of 0.05 C, and the high-voltage storage device was held at 65° C. for 35 hours. Then, the storage device was discharged to 3.0 V.
  • the volume of the storage device after discharge was measured, and this measured value was regarded as the initial volume.
  • the storage device after discharge was then stored at 60°C for several days, and the volume of the storage device was measured periodically during the storage period, and the amount of volume increase from the initial volume was calculated.
  • the calculated amount of volume increase was regarded as the amount of gas generated.
  • the results are shown in the graph in Figure 5.
  • the volume of the storage device was measured by the Archimedes method using an electronic specific gravity meter (MDS-300 manufactured by Alpha Mirage).
  • Comparative Example 1 is an example in which a liquid electrolyte containing only vinylene carbonate was used
  • Comparative Example 2 is an example in which vinylene carbonate and the comparative additive DFOB were added.
  • Figure 5 in Comparative Examples 1 and 2, the amount of gas generated increased as the number of storage days increased. This result indicates that gas continues to be generated in the devices of Comparative Examples 1 and 2.
  • Example 1 which uses a liquid electrolyte to which lithium difluorophosphate and vinylene carbonate have been added, reduces the amount of gas generated with increasing storage days to less than half. This result shows that the simultaneous addition of lithium difluorophosphate and vinylene carbonate can reduce gas generation from the electrodes.
  • Examples 2 to 4 are examples using a liquid electrolyte containing lithium difluorophosphate, vinylene carbonate, and propane sultone or propene sultone. As shown in Figure 5, no gas generation was observed in Examples 2 to 4. These results show that gas generation from the electrodes can be significantly reduced or eliminated by further adding a cyclic sulfonate ester such as propane sultone or propene sultone.
  • Example 1 Although detailed data is omitted, as an additional test, a storage battery was obtained in the same manner as in Example 1, except that the single-walled carbon nanotubes (1 mass%) were replaced with particulate carbon black in an amount (3.8 mass%) that provided an equivalent capacity retention rate. When the amount of gas generated from this storage battery was measured, the amount of gas generated was greater than in Example 1. From these results, it can be seen that the effect of reducing the amount of gas generated in each example is an effect that can be obtained when carbon fiber is used as the conductive additive.
  • F fiber bundle P: graphite particles S: sealed space 10: power storage device 21: positive electrode 21b: positive electrode active material layer 22: negative electrode 22b: negative electrode active material layer 23: separator 24: seal portion

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Abstract

L'invention concerne un dispositif de stockage d'énergie (10) comprenant : une électrode positive (21) qui comprend une couche de matériau actif d'électrode positive (21b) ; une électrode négative (22) qui comprend une couche de matériau actif d'électrode négative (22b) ; un séparateur (23) qui est disposé entre l'électrode positive (21) et l'électrode négative (22) ; et un électrolyte liquide qui est disposé entre l'électrode positive (21) et l'électrode négative (22). Le poids de base de la couche de matériau actif d'électrode négative (22b) est égal ou supérieur à 200 g/m2. La couche de matériau actif d'électrode négative (22b) contient des particules de graphite, des fibres de carbone et un liant d'électrode négative. L'électrolyte liquide contient du difluorophosphate de lithium et du carbonate de vinylène.
PCT/JP2025/000247 2024-01-15 2025-01-08 Dispositif de stockage d'énergie et procédé permettant de fabriquer un dispositif de stockage d'énergie Pending WO2025154586A1 (fr)

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Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2018169029A1 (fr) * 2017-03-17 2018-09-20 旭化成株式会社 Électrolyte non aqueux, batterie secondaire non aqueuse, bloc de piles et système hybride
CN112289989A (zh) * 2020-10-12 2021-01-29 常州高态信息科技有限公司 一种超低温磷酸铁锂锂离子电池
CN112331833A (zh) * 2020-11-10 2021-02-05 江西省汇亿新能源有限公司 一种磷酸铁锂启动电池及其制作方法
CN114464766A (zh) * 2020-11-09 2022-05-10 中国科学院苏州纳米技术与纳米仿生研究所 一种新型负电极结构、其制备方法及电池

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2018169029A1 (fr) * 2017-03-17 2018-09-20 旭化成株式会社 Électrolyte non aqueux, batterie secondaire non aqueuse, bloc de piles et système hybride
CN112289989A (zh) * 2020-10-12 2021-01-29 常州高态信息科技有限公司 一种超低温磷酸铁锂锂离子电池
CN114464766A (zh) * 2020-11-09 2022-05-10 中国科学院苏州纳米技术与纳米仿生研究所 一种新型负电极结构、其制备方法及电池
CN112331833A (zh) * 2020-11-10 2021-02-05 江西省汇亿新能源有限公司 一种磷酸铁锂启动电池及其制作方法

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