Power storage device

Abstract

To improve peel strength of a seal part to a current collector.SOLUTION: A power storage device 10 includes a positive electrode 21 where a positive electrode active substance layer 21b is formed on a first surface 21a1 of a positive electrode current collector 21a, and a seal part 24 bonded to the first surface 21a1 of the positive electrode 21. The seal part 24 is composed of an acid-modified polyolefin-based resin. The positive electrode 21 includes a carbon coat layer M provided in an adhesive part to the seal part 24 on the first surface 21a1 of the positive electrode current collector 21a. The carbon coat layer M contains carbon particles and a coat layer binding agent. The coat layer binding agent has an intensity ratio (PCOO / PCH) of a peak (PCOO) indicating a COO structure to a peak (PCH) indicating a CH structure of 0.5 or more and 3.3 or less in an IR absorption spectrum measured by an infrared spectrophotometer.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an electricity storage device. [Background technology]

[0002] Patent Document 1 discloses a flat-type energy storage device constructed by stacking a plurality of individually manufactured energy storage cells in series. The energy 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 current collector, a negative electrode having a negative electrode active material layer formed in the center of one side of a foil-shaped negative electrode current collector, the negative electrode active material layer being disposed so as to face the positive electrode active material layer of the positive electrode, and a separator disposed between the positive electrode and the negative electrode.

[0003] The energy storage cell further includes a seal portion disposed between the positive electrode and the negative electrode and on the outer circumferential side of the positive electrode active material layer and the negative electrode active material layer. The seal portion maintains a gap between the positive electrode current collector and the negative electrode current collector to prevent short circuits between the current collectors, and also liquid-tightly seals the gap between the positive electrode current collector and the negative electrode current collector, thereby forming an enclosed space for accommodating a liquid electrolyte between the positive electrode current collector and the negative electrode current collector. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2017-16825 A Summary of the Invention [Problem to be solved by the invention]

[0005] In conventional energy storage devices, when a load is applied to the adhesive portion between the current collector and the seal, such as when the internal pressure of the sealed space increases, the seal may peel off from the current collector. Peeling of the seal can cause a short circuit between the current collectors and leakage of the liquid electrolyte.

[0006] The present inventors have found that the peel strength of the seal part can be improved by using a seal part made of an acid-modified polyolefin resin and by providing a carbon coating layer containing a specific coating layer binder at the adhesive portion between the seal part and the surface of the current collector. [Means for solving the problem]

[0007] The electricity storage device that solves the above-mentioned problems includes a plurality of electrodes, each having an active material layer formed on a first surface of a current collector, and a sealing portion that is disposed between the plurality of electrodes and is adhered to the first surface of the current collector, the sealing portion being made of an acid-modified polyolefin resin, and at least one of the plurality of electrodes includes a carbon coating layer that is provided on the first surface of the current collector at an adhesion portion with the sealing portion, the carbon coating layer including carbon particles and a coating layer binder, and the coating layer binder has a wavelength band that is 1400 cm or more in an IR absorption spectrum measured by an infrared spectrophotometer. -1 More than 1600cm -1 Peaks within the following range (P CH ) to 1680cm -1 More than 1720cm -1 Peaks within the following range (P COO ) intensity ratio (P COO / P CH ) is between 0.5 and 3.3.

[0008] In the electricity storage device, the coating layer binder preferably contains an acrylic resin. In the electricity storage device, the carbon coating layer is preferably provided on the entire first surface of the current collector.

[0009] In the electricity storage device, the first surface of the current collector is preferably made of aluminum. In the above-described energy storage device, it is preferable that the electrode is a bipolar electrode, and the current collector is a bipolar current collector in which a first current collector having a first surface and a second surface located opposite the first surface and a second current collector having a first surface and a second surface located opposite the first surface are joined together at their second surfaces, and that a first active material layer is formed on the first surface of the first current collector as the active material layer, and a second active material layer is formed on the first surface of the second current collector as the active material layer.

[0010] In the above electricity storage device, it is preferable that the first surface of the first current collector is made of aluminum, and the first surface of the second current collector is made of copper. In the above electricity storage device, it is preferable that the bipolar electrode has the carbon coating layer provided on the adhesive portions with the sealing portion on both the first surface of the first current collector and the second surface of the second current collector.

[0011] The above-described electricity storage device preferably includes a liquid electrolyte disposed between the plurality of electrodes, the liquid electrolyte preferably containing a fluorine-containing metal salt. [Effects of the Invention]

[0012] According to the present invention, the peel strength of the seal portion relative to the current collector can be improved. [Brief explanation of the drawings]

[0013] [Figure 1] FIG. 1 is a cross-sectional view of the electricity storage device. DETAILED DESCRIPTION OF THE INVENTION

[0014] An embodiment of the present invention will now be described with reference to the drawings. The power storage device 10 shown in Fig. 1 is a power storage module used in batteries for various vehicles such as forklifts, hybrid vehicles, and electric vehicles. The power storage device 10 is, for example, a secondary battery such as a nickel-metal hydride secondary battery or a lithium-ion secondary battery. The power storage device 10 may also be an electric double layer capacitor. In this embodiment, the power storage device 10 is illustrated as a lithium-ion secondary battery.

[0015] <Electricity storage device> 1, 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. Hereinafter, 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.

[0016] 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. In this embodiment, the positive electrode 21, the positive electrode current collector 21a, and the positive electrode active material layer 21b correspond to an electrode, a current collector, and an active material layer, respectively.

[0017] In a plan view seen from the stacking direction (hereinafter simply referred to as a plan view), the positive electrode active material layer 21b is formed in the center of the first surface 21a1 of the positive electrode current collector 21a. In the plan view, the peripheral portion of the first surface 21a1 of the positive electrode current collector 21a 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 arranged so as to surround the periphery of the positive electrode active material layer 21b in the plan view.

[0018] The negative electrode 22 includes a negative electrode current collector 22a and a negative electrode active material layer 22b provided on a first surface 22a1 of the negative electrode current collector 22a. In a plan view, the negative electrode active material layer 22b is formed in the center of the first surface 22a1 of the negative electrode current collector 22a. In a plan view, the peripheral portion of the first surface 22a1 of the negative electrode current collector 22a is a negative electrode uncoated portion 22c where the negative electrode active material layer 22b is not provided. In a plan view, the negative electrode uncoated portion 22c is arranged to surround the periphery of the negative electrode active material layer 22b.

[0019] 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. That is, the facing direction of the positive electrode 21 and the negative electrode 22 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 region of the positive electrode active material layer 21b is located within the formation region of the negative electrode active material layer 22b.

[0020] Here, the positive electrode current collector 21a has a second surface 21a2 located opposite the first surface 21a1, and the negative electrode current 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 power storage cells 20 are stacked such that the second surface 21a2 of the positive electrode current collector 21a and the second surface 22a2 of the negative electrode current collector 22a are in contact with each other. In this way, the plurality of power storage cells 20 constituting the cell stack 30 are connected in series.

[0021] In the cell stack 30, two adjacent energy storage cells 20 in the stacking direction form a pseudo bipolar electrode 25 in which the mutually contacting positive electrode current collector 21a and negative electrode current collector 22a are regarded as a single current collector. The pseudo bipolar electrode 25 includes a current collector having a structure in which the positive electrode current collector 21a and the negative electrode current collector 22a are stacked, a positive electrode active material layer 21b formed on one surface of the current collector, and a negative electrode active material layer 22b formed on the other surface.

[0022] The positive electrode current collector 21a and the negative electrode current collector 22a may form a bipolar current collector in which the second surface 21a2 of the positive electrode current collector 21a and the second surface 22a2 of the negative electrode current collector 22a are joined together. In this case, the positive electrode 21 and the negative electrode 22 form a bipolar electrode 25 including one bipolar current collector in which the positive electrode current collector 21a and the negative electrode current collector 22a are joined together.

[0023] The separator 23 is disposed between the positive electrode 21 and the negative electrode 22, and is a component that separates the positive electrode 21 and the negative electrode 22 to prevent short circuits due to contact between the two electrodes, while allowing charge carriers such as lithium ions to pass through.

[0024] The separator 23 is, for example, a porous sheet or nonwoven fabric containing a polymer that absorbs and retains the liquid electrolyte. Examples of materials that make up 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 include, for example, an adhesive layer, a ceramic layer as a heat-resistant layer, and the like.

[0025] The seal portion 24 is disposed between the first surface 22a1 of the positive electrode current collector 21a of the positive electrode 21 and the first surface 22a1 of the negative electrode current collector 22a of the negative electrode 22, and is disposed on the outer peripheral side of the positive electrode active material layer 21b and the negative electrode active material layer 22b, and is bonded to both the positive electrode current collector 21a and the negative electrode current collector 22a. The seal portion 24 insulates the positive electrode current collector 21a from the negative electrode current collector 22a, thereby preventing a short circuit between the current collectors.

[0026] The sealing portion 24 extends along the peripheral edges of the positive electrode current collector 21 a and the negative electrode current collector 22 a in a plan view, and is formed in a frame shape surrounding the peripheries of the positive electrode active material layer 21 b and the negative electrode active material layer 22 b. The sealing portion 24 is disposed between the positive electrode uncoated portion 21 c on the first surface 21 a 1 of the positive electrode current collector 21 a and the negative electrode uncoated portion 22 c on the first surface 22 a 1 of the negative electrode current collector 22 a.

[0027] An enclosed space S is formed inside the energy storage cell 20 and is surrounded by a frame-shaped seal portion 24, the positive electrode 21, and the negative electrode 22. A separator 23 and a liquid electrolyte are housed in the enclosed space S. The peripheral portion of the separator 23 is embedded in the seal portion 24.

[0028] The seal 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 seal portion 24 can also prevent moisture from entering the sealed space S from the outside of the electricity storage device 10. Furthermore, the seal 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 electricity storage device 10.

[0029] The seal portion 24 of each storage cell 20 has an outer peripheral portion 24a that extends outward beyond the edges of the positive electrode current collector 21a and the negative electrode current collector 22a. When viewed from the stacking direction, the outer peripheral portion 24a protrudes beyond the edges of the positive electrode current collector 21a and the negative electrode current 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 24a of the seal portions 24 together. Examples of methods for bonding adjacent seal portions 24 together include known welding methods such as heat welding, ultrasonic welding, and infrared welding.

[0030] The energy storage device 10 includes a pair of current-carrying bodies, consisting of a positive electrode current-carrying plate 40 and a negative electrode current-carrying plate 50, which are arranged to sandwich the cell stack 30 in the stacking direction of the cell stack 30. The positive electrode current-carrying plate 40 and the negative electrode current-carrying plate 50 are each made of a material with excellent conductivity.

[0031] 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 outermost 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 outermost at the other end in the stacking direction.

[0032] 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 collector 21a. The positive electrode current-carrying plate 40 may be formed of a metal plate that is thicker than the positive electrode current collector 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 collector 22a. The negative electrode current-carrying plate 50 may be formed of a metal plate that is thicker than the negative electrode current collector 22a used in the cell stack 30.

[0033] Next, the positive electrode current collector 21a, the negative electrode current collector 22a, the positive electrode active material layer 21b, the negative electrode active material layer 22b, the liquid electrolyte, and the seal portion 24 will be described in detail. <Positive electrode current collector and negative electrode current collector> The positive electrode current collector 21a is a chemically inactive electrical conductor that allows current to continue to flow through the positive electrode active material layer 21b during charging or discharging of the lithium-ion secondary battery. One example of the positive electrode current collector 21a is an aluminum current collector whose surface, which becomes the first surface 21a1, is made of aluminum. The aluminum current collector may be a single body made entirely of aluminum, or a composite having a portion made of aluminum and a portion made of a material other than aluminum. An example of the single body is aluminum foil. An example of the composite is a multilayer structure in which the layer making up the first surface 21a1 is an aluminum layer, or a substrate whose surface, including the first surface 21a1, is coated with an aluminum film.

[0034] Examples of the material other than aluminum include metal materials, conductive resin materials, and conductive inorganic materials. Examples of the metal materials include copper, 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 obtained by adding a conductive filler to a conductive polymer material or a non-conductive polymer material as needed. The aluminum current collector may be in the form of, for example, a foil, a sheet, or a film. The thickness of the aluminum current collector is, for example, 1 to 100 μm.

[0035] The negative electrode current collector 22a is a chemically inactive electrical conductor for continuing to pass current to the negative electrode active material layer 22b during discharging or charging of the lithium ion secondary battery. An example of the negative electrode current collector 22a is a copper current collector whose surface, which becomes the first surface 22a1, is made of copper. The copper current collector may be a single object made entirely of copper, or a composite having a portion made of copper and a portion made of a material other than copper. An example of the single object is copper foil. An example of the composite is a multilayer structure in which the layer making up the first surface 22a1 is a copper layer, or a substrate whose surface, including the first surface 22a1, is coated with a copper film.

[0036] 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 obtained by adding a conductive filler to a conductive polymer material or a non-conductive polymer material as needed. The copper current collector may be in the form of, for example, a foil, sheet, or film. The aluminum current collector has a thickness of, for example, 1 to 100 μm.

[0037] A preferred example of a combination of the positive electrode current collector 21a and the negative electrode current collector 22a is a combination in which the positive electrode current collector 21a is made of aluminum foil, which is an aluminum current collector, and the negative electrode current collector 22a is made of copper foil, which is a copper current collector. Examples of the bipolar current collector include a current collector in which two aluminum foils are bonded together, a current collector in which an aluminum foil and a copper foil are bonded together, and a current collector in which copper is plated on the surface of an aluminum foil.

[0038] In addition, a carbon coating layer M is provided on the first surface 21a1 of the positive electrode current collector 21a. Details of the carbon coating layer M will be described later. <Positive Electrode Active Material Layer and Negative Electrode Active Material Layer> The positive electrode active material layer 21b contains a positive electrode active material capable of absorbing and releasing charge carriers such as lithium ions. The positive electrode active material may be any material that can be used as a positive electrode active material for lithium ion secondary batteries, such as a lithium composite metal oxide having a layered rock salt structure, a metal oxide having a spinel structure, or a polyanion-based compound. Two or more positive electrode active materials may also be used in combination. In this embodiment, the positive electrode active material layer 21b contains olivine-type lithium iron phosphate (LiFePO4) as a polyanion-based compound.

[0039] The negative electrode active material layer 22b can be made of any element, alloy, or compound capable of absorbing and releasing charge carriers such as lithium ions. Examples of the negative electrode active material include Li, carbon, metal compounds, and elements or compounds thereof that can be alloyed with lithium. Examples of carbon include natural graphite, artificial graphite, hard carbon (non-graphitizable carbon), and soft carbon (easily graphitizable carbon). Examples of artificial graphite include highly oriented graphite and mesocarbon microbeads. Examples of elements that can be alloyed with lithium include silicon and tin. In this embodiment, the negative electrode active material layer 22b contains graphite as a carbon-based material.

[0040] The positive electrode active material layer 21b and the negative electrode active material layer 22b (hereinafter also simply referred to as the active material layer) may each further contain, as necessary, a conductive aid for improving electrical conductivity, a binder, an electrolyte (a polymer matrix, an ion-conductive polymer, a liquid electrolyte, etc.), an electrolyte supporting salt (lithium salt) for improving ion conductivity, etc. The components contained in the active material layer, the blending ratio of these components, and the thickness of the active material layer are not particularly limited, and conventionally known knowledge about lithium ion secondary batteries may be referred to as appropriate.

[0041] The conductive additive is added to increase the conductivity of the positive electrode 21 or the negative electrode 22. Examples of the conductive additive include acetylene black, carbon black, and graphite. Examples of binders include fluorine-containing resins such as polyvinylidene fluoride, polytetrafluoroethylene, and fluororubber; 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 crosslinks; and starch-acrylic acid graft polymers. These binders may be used alone or in combination. Examples of solvents or dispersion media include water and N-methyl-2-pyrrolidone.

[0042] The method for forming the active material layer on the surface of the positive electrode current collector 21a and the negative electrode current collector 22a is not particularly limited, and a conventionally known method such as roll coating can be used. In order to improve the thermal stability of the positive electrode 21 or the negative electrode 22, the above-mentioned heat-resistant layer may be provided on the surface of the active material layer.

[0043] The basis weight of the active material layer is not particularly limited, and conventionally known knowledge about lithium ion secondary batteries can be referred to as appropriate. However, from the viewpoint of increasing the energy density of the storage cell 20, it is preferable to increase the basis weight of the active material layer. The basis weight of the positive electrode active material layer 21b is, for example, 55 to 90 mg / cm. 2 and 60 mg / cm 2 Preferably, it is 70 mg / cm or more. 2 The weight of the negative electrode active material layer 22b is, for example, 25 to 45 mg / cm 2 2 and 30 mg / cm 2 It is preferable that this is equal to or greater than this.

[0044] <Sealing part> The seal portion 24 is made of an acid-modified polyolefin resin. Examples of acid-modified polyolefin resins include acid-modified polyethylene, acid-modified polypropylene, acid-modified isoprene, and acid-modified polybutene. Examples of acid-modified groups include carboxylic acid groups, maleic acid groups, and maleic anhydride groups. The acid-modified polyolefin resin constituting the seal portion 24 may be one type or a combination of two or more types. The acid-modified polyolefin resin constituting the seal portion 24 may be a thermoplastic resin or a thermosetting resin.

[0045] The melting point Tm1 of the acid-modified polyolefin resin constituting the seal portion 24 is, for example, 90°C or higher and 170°C or lower. The thickness of the sealing portion 24 is, for example, preferably 50 μm or more and 1000 μm or less, and more preferably 100 μm or more and 800 μm or less. The thickness of the sealing portion 24 refers to the thickness of a portion located between the first surface 21a1 of the positive electrode current collector 21a and the first surface 22a1 of the negative electrode current collector 22a.

[0046] The sealing portion 24 is adhered to the first surface 21a1 of the positive electrode current collector 21a, more specifically, to the carbon coating layer M provided on the first surface 21a1. The sealing portion 24 is also adhered to the first surface 22a1 of the negative electrode current collector 22a.

[0047] <Liquid electrolyte> The liquid electrolyte contains a non-aqueous solvent and an electrolyte salt dissolved in the non-aqueous solvent. Known lithium salts such as LiClO4, LiAsF6, LiPF6, LiBF4, LiCF3SO3, LiN(FSO2)2, and LiN(CF3SO2)2 can be used as the electrolyte salt. Known solvents such as cyclic carbonates, cyclic esters, chain carbonates, chain esters, and ethers can be used as the non-aqueous solvent. Two or more of these known solvent materials may be used in combination.

[0048] An example of the liquid electrolyte contains a fluorine-containing metal salt as an electrolyte salt. Examples of the fluorine-containing metal salt include fluorine-containing lithium salts such as LiPF6, LiBF4, and LiAsF6. When the liquid electrolyte contains a fluorine-containing metal salt, the proportion of the fluorine-containing metal salt in the electrolyte salt is, for example, 50 mass% or more.

[0049] <Carbon coating layer> Next, the carbon coating layer M provided on the first surface 21a1 of the positive electrode current collector 21a will be described.

[0050] In this embodiment, the carbon coating layer M is provided on the entire first surface 21a1 of the positive electrode current collector 21a. Therefore, the first surface 21a1 of the positive electrode current collector 21a is bonded to the sealing portion 24 via the carbon coating layer M. In other words, the sealing portion 24 is bonded to the carbon coating layer M provided on the first surface 21a1 of the positive electrode current collector 21a.

[0051] The carbon coating layer M contains carbon particles and a coating layer binder. The carbon particles may be any known carbon material that is used for a carbon coating layer, such as graphite, acetylene black, etc. The carbon particle content in the carbon coating layer M is, for example, 13% by mass or more and 90% by mass or less.

[0052] The coating layer binder has a structure represented by "-COO-" (hereinafter referred to as COO structure) and a structure represented by "-CH" (hereinafter referred to as CH structure) in the chemical formula, and is composed of a material in which the abundance ratio of each of these structures falls within a specific range.

[0053] In detail, the coating layer binder has a peak representing a COO structure and a peak representing a CH structure in an IR absorption spectrum measured by an infrared spectrophotometer, and the intensity ratio of these two peaks is a specific ratio. -1 More than 1720cm -1 The peak representing the CH structure appears in the range of 1400 cm in the above IR absorption spectrum. -1 More than 1600cm -1 The peaks appear in the following range:

[0054] The peak representing the CH structure (P CH ) for the peak representing the COO structure (P COO ) intensity ratio (P COO / P CH ) is 0.5 or more and 3.3 or less. By using a coating layer binder having the strength ratio within the above range, it is possible to suppress a decrease in the peel strength of the seal portion 24 over time.

[0055] The intensity used to calculate the intensity ratio is the transmittance absorbance A calculated based on the measured transmittance reflectance R. * (=log(1 / R)), and the transmitted absorbance A * The value is obtained by subtracting the background from the peak (P CH ) and peak (P COO ) means the intensity at the apex of the peak.

[0056] Examples of materials constituting the coating layer binder include acrylic resins and carboxy-modified styrene-butadiene rubbers, and the material constituting the coating layer binder is preferably an acrylic resin.

[0057] Examples of the acrylic resin include homopolymers of acrylic monomers such as acrylic acid, methacrylic acid, and (meth)acrylic acid esters, and (meth)acrylic copolymers containing the above acrylic monomers. In this embodiment, (meth)acrylic acid refers to acrylic acid or methacrylic acid.

[0058] Examples of the (meth)acrylic acid ester include methyl (meth)acrylate, ethyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, and isobutyl (meth)acrylate.

[0059] In the (meth)acrylic copolymer, other comonomers copolymerized with the acrylic monomer include α-olefin, styrene, α-methylstyrene, vinyltoluene, acrylonitrile, methacrylonitrile, and vinyl acetate. These comonomers can be present in the acrylic resin in the form of random copolymer, graft copolymer, or block copolymer. Examples of the (meth)acrylic copolymer include silicon-modified acrylic-styrene resin, carboxy-modified acrylic-styrene resin, and hydroxyl-modified acrylic resin.

[0060] The material constituting the coating layer binder may be one kind or a combination of two or more kinds. When the coating layer binder is a mixture of two or more of the above materials, the mixing ratio and the like are adjusted so that the above strength ratio is within the above range as a whole coating layer binder.

[0061] The glass transition temperature Tg2 of the coating layer binder is, for example, 0°C or higher and 150°C or lower. When the seal portion 24 is adhered by heat welding, it is preferable to heat the sealing material, which is the material forming the seal portion 24, at a temperature higher than the glass transition temperature Tg2 of the coating layer binder and at a temperature equal to or higher than the melting point Tm1 of the acid-modified polyolefin resin constituting the seal portion 24. In this case, due to the heating for adhering the seal portion 24, the coating layer binder contained in the carbon coating layer M softens, so that the coating layer binder and the seal portion 24 are more likely to be compatible. Therefore, it is preferable that the glass transition temperature Tg2 of the coating layer binder is lower than the melting point Tm1 of the acid-modified polyolefin resin constituting the seal portion 24 (Tg2 < Tm1). The difference between the melting point Tm1 of the acid-modified polyolefin resin and the glass transition temperature Tg2 of the coating layer binder (melting point Tm1 - Tg2) is, for example, 5°C or higher and 100°C or lower.

[0062] The thickness of the carbon coating layer M is, for example, 0.1 μm or more and 5 μm or less, and preferably 0.5 μm or more and 2 μm or less. The carbon coating layer may contain other components such as a dispersant. Examples of the dispersant include carboxyethyl cellulose.

[0063] Next, a method for manufacturing the power storage device 10 of the present embodiment will be described. The power storage device 10 is manufactured by sequentially going through an electrode forming step, a power storage cell forming step, and a cell stack forming step. Here, as an example, the case where the positive electrode current collector 21a is made of an aluminum foil and the negative electrode current collector 22a is made of a copper foil will be described.

[0064] <Electrode forming step> The electrode forming step includes a positive electrode forming step of forming the positive electrode 21 and a negative electrode forming step of forming the negative electrode 22.

[0065] In the positive electrode formation process, first, a carbon coating layer M is formed on the entire first surface 21a1 of an aluminum foil serving as the positive electrode current collector 21a. Prior to the formation of the carbon coating layer M, a corona discharge treatment is performed on the first surface 21a1 of the aluminum foil. The corona discharge treatment forms hydrophilic groups (OH groups) on the first surface 21a1 of the aluminum foil. The carbon coating layer M can be formed by any known method applicable to the formation of coatings, such as a solution-based process or a vapor deposition-based process.

[0066] An example of a solution-based process is described below. First, a carbon paste is prepared by kneading carbon particles, a coating layer binder, and an aqueous solvent. The carbon paste is applied to the entire first surface 21a1 of the positive electrode current collector 21a to a predetermined thickness to form a coating film. The formed coating film is dried and solidified to form the carbon coating layer M. Examples of processes for solidifying the carbon paste coating include drying to volatilize the solvent, heating to a temperature equal to or higher than the glass transition temperature Tg2 of the coating layer binder, and then cooling to solidify. Examples of aqueous solvents used in the carbon paste include water and mixed solvents of water and an organic solvent. Examples of organic solvents used in the mixed solvent include N-methyl-2-pyrrolidone (NMP).

[0067] When forming a bipolar electrode 25 having a bipolar current collector, instead of aluminum foil as the positive electrode current collector 21a, a current collector in which aluminum foils are bonded together, a current collector in which aluminum foil and copper foil are bonded together, a current collector in which copper is plated on the surface of aluminum foil, etc. are used.

[0068] Next, a cathode composite material that will become the cathode active material layer 21b when solidified is adhered to a predetermined thickness to the center of the first surface 21a1 of the aluminum foil on which the carbon coating layer M is formed. Thereafter, a solidification process appropriate for the cathode composite material is performed to form the cathode active material layer 21b.

[0069] The negative electrode formation step is not particularly limited, and may be any known method applicable to forming the negative electrode 22 including the negative electrode current collector 22 a and the negative electrode active material layer 22 b. For example, the negative electrode 22 can be formed by adhering a negative electrode composite material, which will become the negative electrode active material layer 22 b when solidified, to a first surface 22 a 1 of copper foil serving as the negative electrode current collector 22 a to a predetermined thickness, and then performing a solidification treatment appropriate for the negative electrode composite material.

[0070] <Storage cell formation process> In the energy storage cell formation process, first, the positive electrode 21 and the negative electrode 22 are arranged so that the positive electrode active material layer 21b and the negative electrode active material layer 22b face each other in the stacking direction with the separator 23 sandwiched therebetween. In addition, a sealing material that will become the sealing portion 24 is arranged between the positive electrode 21 and the negative electrode 22 and on the outer periphery of the positive electrode current collector 21a and the negative electrode current collector 22a. The sealing material is a resin sheet made of an acid-modified polyolefin resin cut into the same shape as the sealing portion 24 in a planar view. At this time, the sealing material is arranged so as to contact the carbon coating layer M on the first surface 21a1 of the positive electrode current collector 21a.

[0071] Thereafter, the positive electrode 21, the negative electrode 22, the separator 23, and the sealing material are welded together to form an assembly in which the positive electrode 21, the negative electrode 22, the separator 23, and the sealing portion 24 are integrated together. Examples of methods for bonding the sealing material include known welding methods such as heat welding, ultrasonic welding, and infrared welding.

[0072] When the seal portion 24 is formed by thermal welding, the seal material may be heated to a temperature equal to or higher than the melting point Tm1 of the acid-modified polyolefin resin that constitutes the seal material, and then cooled to solidify. At this time, if the glass transition temperature Tg2 of the coating layer binder is lower than the melting point Tm1 of the acid-modified polyolefin resin, the coating layer binder also softens, making the coating layer binder and the acid-modified polyolefin resin more compatible with each other.

[0073] Next, a liquid electrolyte is injected into the sealed space S inside the assembly through an injection port provided in a part of the seal portion 24, and then the injection port is sealed. In this way, the energy storage cell 20 is formed. <Cell stack formation process> In the cell stack forming process, first, the plurality of energy storage cells 20 are stacked on top of each other so that the second surfaces 21a2 of the positive electrode current collectors 21a and the second surfaces 22a2 of the negative electrode current collectors 22a face each other. Then, the plurality of energy storage cells 20 are integrated by bonding the outer circumferential portions 24a of the seal portions 24 of the energy storage cells 20 adjacent to each other in the stacking direction.

[0074] Next, the positive electrode current-carrying plate 40 is overlapped 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 outermost at one end in the stacking direction. Similarly, the negative electrode current-carrying plate 50 is overlapped 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 outermost at the other end in the stacking direction.

[0075] <effect> Next, the operation of this embodiment will be described. In the electricity storage device 10 of this embodiment, a carbon coating layer M is provided on the entire first surface 21a1 of the positive electrode current collector 21a. A sealing portion 24 made of an acid-modified polyolefin resin is adhered to the carbon coating layer M provided on the first surface 21a1 of the positive electrode current collector 21a. The coating layer binder contained in the carbon coating layer M has a COO structure and a CH structure, and is made of a material in which the abundance ratio of each structure falls within the above-mentioned specific range.

[0076] In this configuration, the first surface 21a1 of the positive electrode current collector 21a is bonded to the coating layer binder contained in the carbon coating layer M. This bond is considered to be either an ester bond or a hydrogen bond, or both. The ester bond is a bonding structure (-COOMe) formed by an ester bond between a hydroxyl group (Me-OH) on the first surface 21a1 of the positive electrode current collector 21a and a carboxyl group (-COOH) of the coating layer binder. "Me" refers to the metal constituting the current collector. The hydrogen bond is a bonding structure formed by a hydrogen bond between a hydroxyl group (Me-OH) on the first surface 21a1 of the positive electrode current collector 21a and either or both of a hydroxyl group and a carboxyl group of a material constituting the carbon coating layer M. The hydroxyl group is either or both of a hydroxyl group (C-OH) on the surface of the carbon particle and a hydroxyl group (C-OH) of the coating layer binder. The carboxyl group is a carboxyl group (-COOH) of the coating layer binder.

[0077] Furthermore, at the interface between the sealing portion 24 and the carbon coating layer M, the acid-modified polyolefin resin of the sealing portion 24 is bonded to the carbon particles contained in the carbon coating layer M. This bond is considered to be either an ester bond or a hydrogen bond, or both. The ester bond is a bond structure (-COOC) in which a hydroxyl group (C-OH) on the surface of the carbon particle is ester-bonded to a carboxyl group (-COOH) of the acid-modified polyolefin resin. The hydrogen bond is a bond structure in which either a hydroxyl group or a carboxyl group, or both, of the material constituting the carbon coating layer M is hydrogen-bonded to a carboxyl group (-COOH) of the acid-modified polyolefin resin. The hydroxyl group is either or both of the hydroxyl group (C-OH) on the surface of the carbon particle and the hydroxyl group (C-OH) of the coating layer binder. The carboxyl group is the carboxyl group (-COOH) of the coating layer binder. The above-mentioned bonding structure is formed at the interface between the positive electrode current collector 21a and the carbon coating layer M, and at the interface between the sealing portion 24 and the carbon coating layer M, so that the sealing portion 24 is adhered to the first surface 21a1 of the positive electrode current collector 21a via the carbon coating layer M.

[0078] Furthermore, since the abundance ratio of the COO structure and the CH structure in the coating layer binder is within the above-mentioned specific range, the affinity between the coating layer binder and the acid-modified polyolefin resin constituting the seal portion 24 is improved. As a result, at the interface between the seal portion 24 and the carbon coating layer M, the coating layer binder and the acid-modified polyolefin resin are compatible with each other and come into close contact with each other.

[0079] As described above, according to the configuration of this embodiment, a bonded structure is formed at the interface between the first surface 21a1 of the positive electrode current collector 21a and the carbon coating layer M, and at the interface between the sealing portion 24 and the carbon coating layer M. In addition, the coating layer binder contained in the carbon coating layer M and the sealing portion 24 are compatible with each other and tightly bonded together, thereby improving the peel strength of the sealing portion 24 from the positive electrode current collector 21a.

[0080] Furthermore, in the above configuration in which the carbon coating layer M is formed on the first surface 21a1 of the positive electrode current collector 21a and the carbon coating layer M and the seal portion 24 are closely adhered to each other, it is possible to prevent the liquid electrolyte from coming into contact with the first surface 21a1 of the positive electrode current collector 21a. In addition, the carbon coating layer M acts as a barrier that prevents the liquid electrolyte from penetrating the first surface 21a1 of the positive electrode current collector 21a, thereby also preventing the liquid electrolyte from coming into contact with the first surface 21a1 of the positive electrode current collector 21a. This prevents a decrease in the peel strength of the seal portion 24 from the positive electrode current collector 21a.

[0081] More specifically, in a conventional power storage device, for example, when a liquid electrolyte containing LiPF6 as an electrolyte salt and a seal formed of an acid-modified polyolefin resin are used, the peel strength of the seal may decrease over time. This decrease in the peel strength of the seal is thought to be due to hydrofluoric acid (HF) derived from LiPF6. LiPF6 generates hydrofluoric acid by reacting with water (HO) contained in the liquid electrolyte, for example.

[0082] In the case of a conventional structure in which the sealing portion is bonded to the surface of the current collector, a bonding structure (-COOMe) is formed on the surface of the current collector through an ester bond between the hydroxyl groups (M-OH) on the surface of the current collector and the carboxyl groups (-COOH) of the acid-modified polyolefin resin sealing portion. This bonding structure (-COOMe) allows the sealing portion to adhere to the surface of the current collector. Hydrofluoric acid derived from LiPF6 destroys the bonding structure (-COOM) formed between the sealing portion and the current collector, thereby reducing the peel strength of the sealing portion to the current collector. Furthermore, hydrofluoric acid fluorinates the surface of the current collector (MeF). The fluorinated portion of the current collector surface cannot re-form the bonding structure (-COOMe) with the sealing portion, so the reduced peel strength of the sealing portion remains. As a result, the peel strength of the sealing portion decreases over time. These phenomena are thought to occur similarly when using a liquid electrolyte containing a fluorine-containing metal salt other than LiPF6 as the electrolyte salt.

[0083] According to the present embodiment, as described above, contact of the liquid electrolyte with the first surface 21a1 of the positive electrode current collector 21a is suppressed. Therefore, the bond structure formed at the interface between the first surface 21a1 of the positive electrode current collector 21a and the carbon coating layer M is maintained, and fluorination of the first surface 21a1 of the positive electrode current collector 21a is suppressed. As a result, a decrease in the peel strength of the seal portion 24 over time is suppressed.

[0084] <Effects> According to this embodiment, the following effects can be obtained. (1) The electricity storage device 10 includes a positive electrode 21 having a positive electrode active material layer 21b formed on a first surface 21a1 of a positive electrode current collector 21a, and a seal portion 24 bonded to the first surface 21a1 of the positive electrode 21. The seal portion 24 is made of an acid-modified polyolefin resin. The positive electrode 21 includes a carbon coating layer M provided on the first surface 21a1 of the positive electrode current collector 21a at an adhesive portion with the seal portion 24. The carbon coating layer M includes carbon particles and a coating layer binder. The coating layer binder has a peak (P CH) for the peak representing the COO structure (P COO ) intensity ratio (P COO / P CH ) is between 0.5 and 3.3.

[0085] According to the above configuration, a bonded structure is formed at the interface between the first surface 21a1 of the positive electrode current collector 21a and the carbon coating layer M, and at the interface between the sealing portion 24 and the carbon coating layer M. In addition, the coating layer binder contained in the carbon coating layer M and the sealing portion 24 are compatible with each other and tightly bonded together, thereby improving the peel strength of the sealing portion 24 from the positive electrode current collector 21a.

[0086] (2) The coating layer binder contains an acrylic resin. According to the above configuration, the effect (1) above can be more significantly obtained. (3) The carbon coating layer M is provided on the entire first surface 21a1 of the positive electrode current collector 21a.

[0087] According to the above configuration, the process of forming the carbon coating layer M can be simplified compared to a configuration in which the carbon coating layer M is provided on part of the first surface 21a1 of the positive electrode current collector 21a. (4) The electricity storage device 10 includes a bipolar electrode 25 having a bipolar current collector. The bipolar current collector includes a positive electrode current collector 21a (first current collector) having a first surface 21a1 and a second surface 21a2 located opposite the first surface 21a1, and a negative electrode current collector 22a (second current collector) having a first surface 22a1 and a second surface 22a2 located opposite the first surface 22a1, joined together at their second surfaces. A positive electrode active material layer 21b (first active material layer) is formed on the first surface 21a1 of the positive electrode current collector 21a. A negative electrode active material layer 22b (second active material layer) is formed on the first surface 22a1 of the negative electrode current collector 22a.

[0088] According to the above configuration, in the electricity storage device 10 including the bipolar electrode 25, the peel strength of the seal portion 24 can be improved. (6) The electricity storage device 10 includes a liquid electrolyte containing a fluorine-containing metal salt.

[0089] The fluorine-containing metal salt contained in the liquid electrolyte may cause a decrease in the peel strength of the seal portion 24. Therefore, it is particularly effective to improve the peel strength of the seal portion 24 by using the effect (1) above. In addition, the decrease in the peel strength of the seal portion 24 over time can be suppressed.

[0090] This embodiment can be modified as follows: This embodiment and the following modifications can be combined and implemented within the scope of technical compatibility. The carbon coating layer M may be provided on at least a portion of the first surface 21a1 of the positive electrode current collector 21a that is bonded to the seal portion 24. For example, the carbon coating layer M may be absent from a portion of the first surface 21a1 of the positive electrode current collector 21a that is bonded to the seal portion 24. However, the carbon coating layer M is preferably formed in a ring shape surrounding the sealed space S in a plan view on the portion of the first surface 21a1 of the positive electrode current collector 21a that is bonded to the seal portion 24. Furthermore, the carbon coating layer M may be absent from a portion or the entirety of the portion of the first surface 21a1 of the positive electrode current collector 21a that is not bonded to the seal portion 24.

[0091] The carbon coating layer M may be provided on the first surface 22a1 of the negative electrode current collector 22a instead of on the first surface 21a1 of the positive electrode current collector 21a. Alternatively, the carbon coating layer M may be provided on both the first surface 21a1 of the positive electrode current collector 21a and the first surface 22a1 of the negative electrode current collector 22a.

[0092] The 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 applies to the negative electrode current collector 22a and the negative electrode active material layer 22b.

[0093] The shape of the seal portion 24 in plan view is not particularly limited, and may be a polygonal shape such as a rectangle, or may be a circle or an ellipse. A conductive layer that adheres closely to the positive electrode current collector 21a may be disposed between the positive electrode current-carrying plate 40 and the positive electrode current collector 21a to improve the conductive contact between the two components. Examples of the conductive layer include a layer containing carbon such as acetylene black or graphite, or a layer having a lower hardness than the positive electrode current collector 21a, such as a plating layer containing Au. A similar conductive layer may also be disposed between the negative electrode current-carrying plate 50 and the negative electrode current collector 22a.

[0094] There is no particular limitation on the number of storage cells 20 that make up the energy storage device 10. The number of storage cells 20 that make up the energy storage device 10 may be one. The positive electrode active material layer 21b or the negative electrode active material layer 22b may be provided on the second surface 21a2 of the positive electrode current collector 21a. Also, the positive electrode active material layer 21b or the negative electrode active material layer 22b may be provided on the second surface 22a2 of the negative electrode current collector 22a.

[0095] The energy storage device 10 may include a restraining member that restrains the cell stack 30. The restraining member applies a restraining load to a region where the energy storage cells 20 face each other in the stacking direction of the cell stack 30, particularly to a region where the area where the positive electrode active material layer 21b is provided overlaps with the area where the negative electrode active material layer 22b is provided in a plan view.

[0096] The specific configuration of the restraining member is not particularly limited as long as it is capable of applying a restraining load to the cell stack 30. For example, the restraining member may be configured to include plate-shaped restraining plates disposed at both ends of the cell stack 30 in the stacking direction so as to sandwich the cell stack 30, and fastening members made of bolts and nuts that fasten the restraining plates together. In the case of a restraining member configured as described above, the fastening members urge the restraining plates in directions that bring them closer to each other, thereby applying a restraining load to the cell stack 30 in the stacking direction. [Example]

[0097] Hereinafter, a more specific example of the above embodiment will be described. <IR absorption spectrum measurement of coating layer binder> Test pieces coated with each different resin were obtained by coating aluminum foil with any of the commercially available resins 1 to 6 shown in Table 1. In Table 1, SBR means styrene-butadiene rubber.

[0098] For each of the obtained test pieces, the IR absorption spectrum (microscopic reflection method) was measured using an infrared spectrophotometer at 25°C. The measured transmittance reflectance R was used to calculate the transmittance absorbance A * (=log(1 / R)) and calculate the wave number (cm -1 ) is the horizontal axis, and the transmittance absorbance A * From the graph, 1680cm -1 More than 1720cm -1 Peaks within the following range (P COO ) is the intensity of the transmitted absorbance A * , and 1400 cm -1 More than 1600cm -1 Peaks within the following range (P CH ) is the intensity of the transmitted absorbance A * Then, the peak (P CH ) intensity versus peak (P COO ) intensity ratio (P COO / P CH The results are shown in Table 1. COO ) and peak (P CH ) is expressed as the transmittance absorbance A * The value obtained by subtracting the background from the above was used.

[0099] [Table 1] <Preparation of carbon paste> Carbon particles, a coating layer binder, carboxyethyl cellulose (CMC), and water were kneaded to prepare a carbon paste. Acetylene black was used as the carbon particles. One of resins 1 to 6 was used as the coating layer binder. The mass ratio of the solid contents in the carbon paste was 50:37.5:12.5 (carbon particles: coating layer binder: CMC). The solvent content in the carbon paste was adjusted to a solid content of 85% by mass.

[0100] <Preparation of Examples 1 to 4 and Comparative Examples 1 to 3> An aluminum foil having a thickness of 30 μm was prepared, and one side of the foil was subjected to a corona discharge treatment to hydrophilize the surface of the aluminum foil. A carbon paste using Resin 1 was applied to the entire hydrophilized surface of the aluminum foil to form a coating film. The formed coating film was dried. The sheet was then heated at 150°C for 10 seconds and cooled to form a carbon coating layer having a thickness of 1 μm. The obtained sheet material was used as the sheet material of Example 1.

[0101] Sheet materials of Examples 2 to 4 were obtained by the same method as in Example 1, except that the carbon paste using resin 1 was changed to carbon paste using resins 2, 4, and 5. Furthermore, sheet materials of Comparative Examples 1 and 2 were obtained by the same method as in Example 1, except that the carbon paste using resin 1 was changed to carbon paste using resins 3 and 6.

[0102] <Peel test> A rectangular current collector measuring 10 mm in length and 50 cm in width was obtained by cutting out the sheet material of Example 1. A rectangular sealing material measuring 10 mm in length and 50 mm in width was also prepared. An acid-modified polyethylene sheet having a thickness of 150 μm and a melting point Tm1 of 120°C was used as the sealing material. The sealing material was laminated on the surface of the current collector on which the carbon coating layer was formed, with the edges aligned, to obtain a laminate.

[0103] Next, the laminate was heated at 150°C for 10 seconds using an impulse sealer, and then cooled to produce a measurement sample in which the current collector and sealing material were bonded. The resulting measurement sample was subjected to a 90-degree peel test at a pulling rate of 10 mm / min and a temperature of 60°C. The peel strength of the measurement sample was calculated by dividing the strength measured in the 90-degree peel test by the line width of 10 mm. The results are shown in Table 2.

[0104] Furthermore, the sheet material of Example 1 was replaced with the sheet materials of Examples 2 to 4 and Comparative Examples 1 and 2, and the same peel test was carried out. The results are shown in Table 2.

[0105] [Table 2] As shown in Table 2, the intensity ratio (P COO / P CH In each example using a coating layer binder in which the strength ratio (P COO / P CH The peel strength was higher than that of Comparative Example 1, which used a coating layer binder with a strength ratio (P) of less than 0.5. The peeling in each example was not an interfacial failure at the interface between the aluminum foil and the carbon coating layer, or at the interface between the carbon coating layer and the sealing material, but a cohesive failure within the carbon coating layer. This result indicates that the aluminum foil and the sealing material are firmly bonded via the carbon coating layer. In addition, the strength ratio (P COO / P CH In Comparative Example 2, in which a coating layer binder having a coefficient of adhesion of more than 3.3 was used, the sheet material did not adhere to the carbon coating layer.

[0106] The measurement sample of Example 1 before the immersion treatment was subjected to TEM-EELS analysis of the structure of the interface between the sealing material and the carbon coating layer. As a result, many gradation-like regions were confirmed at the interface, where the coating layer binder contained in the carbon coating layer gradually decreased and the acid-modified polyolefin resin constituting the sealing material gradually increased from the carbon coating layer side toward the sealing material side. This result indicates that the coating layer binder contained in the carbon coating layer and the acid-modified polyolefin resin constituting the sealing material are compatible with each other at the interface.

[0107] Next, the technical ideas that can be understood from the above-described embodiment and modified examples will be described below. [Aspect 1] a power storage device comprising: a plurality of electrodes each having an active material layer formed on a first surface of the current collector; and a sealing portion disposed between the plurality of electrodes and adhered to the first surface of the current collector, wherein the sealing portion is made of an acid-modified polyolefin resin; and at least one of the plurality of electrodes has a carbon coating layer provided on an adhesive portion between the first surface of the current collector and the sealing portion, the carbon coating layer containing carbon particles and a coating layer binder, and the coating layer binder has a carbon-containing carbon particle and a coating layer binder having ... -1 More than 1600cm -1 Peaks within the following range (P CH ) to 1680cm -1 More than 1720cm -1 Peaks within the following range (P COO ) intensity ratio (P COO / P CH ) is 0.5 or more and 3.3 or less.

[0108] [Aspect 2] 2. The electricity storage device according to embodiment 1, wherein the coating layer binder contains an acrylic resin. [Aspect 3] 3. The electricity storage device according to claim 1, wherein the carbon coating layer is provided on the entire first surface of the current collector.

[0109] [Aspect 4] 4. The electricity storage device according to any one of aspects 1 to 3, wherein the first surface of the current collector is made of aluminum.

[0110] [Aspect 5] The power storage device according to any one of Aspects 1 to 4, wherein the electrode is a bipolar electrode, the current collector is a bipolar current collector in which a first current collector has a first surface and a second surface opposite the first surface, and a second current collector has a first surface and a second surface opposite the first surface, and the second surfaces of the first current collector and the second surface are joined together, and a first active material layer is formed on the first surface of the first current collector as the active material layer, and a second active material layer is formed on the first surface of the second current collector as the active material layer.

[0111] [Aspect 6] 6. The power storage device according to aspect 5, wherein the first surface of the first current collector is made of aluminum, and the first surface of the second current collector is made of copper.

[0112] [Aspect 7] The energy storage device according to aspect 5 or 6, wherein the bipolar electrode has the carbon coating layer provided at the adhesive portion with the sealing portion on both the first surface of the first current collector and the second surface of the second current collector.

[0113] [Aspect 8] Aspect 8. The electricity storage device according to any one of aspects 1 to 7, further comprising a liquid electrolyte disposed between a plurality of the electrodes, the liquid electrolyte including a fluorine-containing metal salt.

[0114] [Aspect 9] a first electrode having a first active material layer provided in a center portion of a first surface of a first current collector; a second electrode having a second active material layer provided in a center portion of a first surface of a second current collector, the second active material layer being disposed so as to face the first active material layer of the first electrode; a separator disposed between the first active material layer and the second active material layer; and a seal portion disposed between the first electrode and the second electrode so as to surround the periphery of the first active material layer and the second active material layer, and bonded to each first surface of the first current collector and the second current collector to form an enclosed space for accommodating a liquid electrolyte between the first electrode and the second electrode, the seal portion being made of an acid-modified polyolefin resin; and the first electrode having a carbon coating layer provided on the first surface of the first current collector at an adhesive portion with the seal portion, the carbon coating layer including carbon particles and a coating layer binder, the coating layer binder having an IR absorption spectrum measured by an infrared spectrophotometer of 1400 cm -1 More than 1600cm -1 Peaks within the following range (P CH ) to 1680cm -1 More than 1720cm -1 Peaks within the following range (P COO ) intensity ratio (P COO / P CH ) is 0.5 or more and 3.3 or less.

[0115] In the above-mentioned Aspect 9, the first electrode corresponds to one of the positive electrode 21 and the negative electrode 22 in the above-mentioned embodiment, and the second electrode corresponds to the other of the positive electrode 21 and the negative electrode 22. [Aspect 10] 11. The electricity storage device according to aspect 10, wherein the carbon coating layer is provided on the first surface of the first current collector and the first surface of the second current collector at a portion where the first surface is bonded to the seal portion. [Explanation of symbols]

[0116] M...Carbon coating layer S…Closed space 10...Electricity storage device 20...Storage cell 21...Positive electrode 21a...Positive electrode current collector 21b...Cathode active material layer 22...Negative electrode 22a...Negative electrode current collector 22b...Negative electrode active material layer 23...Separator 24...Seal part 30...Cell stack

Claims

1. a plurality of electrodes each having an active material layer formed on a first surface of a current collector; a seal portion disposed between the plurality of electrodes and adhered to a first surface of the current collector, the sealing portion is made of an acid-modified polyolefin resin, At least one of the plurality of electrodes includes a carbon coating layer provided on an adhesive portion between the first surface of the current collector and the sealing portion, the carbon coating layer includes carbon particles and a coating layer binder, The coating layer binder has an IR absorption spectrum measured by an infrared spectrophotometer, which has a wavelength of 1400 cm －１ More than 1600cm －１ Peaks in the following range (P ＣＨ ) to 1680 cm －１ 1720cm or more －１ Peaks in the following range (P ＣＯＯ ) intensity ratio (P ＣＯＯ / P ＣＨ ) is 0.5 or more and 3.3 or less.

2. The electricity storage device according to claim 1 , wherein the coating layer binder contains an acrylic resin.

3. The electricity storage device according to claim 1 , wherein the carbon coating layer is provided on the entire first surface of the current collector.

4. The electricity storage device according to claim 1 , wherein the first surface of the current collector is made of aluminum.

5. the electrode is a bipolar electrode; the current collector is a bipolar current collector in which a first current collector has a first surface and a second surface located opposite to the first surface, and a second current collector has a first surface and a second surface located opposite to the first surface, and the second surfaces of the first current collector and the second surface of the second current collector are joined together, a first active material layer as the active material layer is formed on a first surface of the first current collector; 5. The electricity storage device according to claim 1, wherein a second active material layer serving as the active material layer is formed on a first surface of the second current collector.

6. a first surface of the first current collector made of aluminum; The electricity storage device according to claim 5 , wherein the first surface of the second current collector is made of copper.

7. The power storage device according to claim 5 , wherein the bipolar electrode is provided with the carbon coating layer on the first surface of the first current collector and the second surface of the second current collector at portions bonded to the seal portion.

8. a liquid electrolyte disposed between a plurality of the electrodes; The electricity storage device according to claim 1 , wherein the liquid electrolyte contains a fluorine-containing metal salt.

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