Structure, electricity storage device, and method for manufacturing electricity storage device

Abstract

To simplify the manufacturing process as much as possible.SOLUTION: The structure of the present disclosure is a structure used in a power storage device, comprises a separator, a positive electrode collector formed on the first surface of the separator and having an opening that is connected to the separator, and a negative electrode collector formed on the second surface of the separator and having an opening that is connected to the separator.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] This specification discloses a structure, an electricity storage device, and a method for manufacturing an electricity storage device. [Background technology]

[0002] Conventionally, a proposed electricity storage device includes an electrode for an electricity storage device having a comb-shaped current collecting portion including an electrode active material, a plurality of current collecting wires that are not electrically connected to each other in the portions adjacent to and in contact with the electrode active material, and a current collector that is a continuum that connects the plurality of current collecting wires in parallel outside the portion where the current collecting wires are not in contact with the electrode active material (see, for example, Patent Document 1). In this electricity storage device, a gradual discharge mechanism can be realized in the sheet-like electrode when an internal short circuit occurs. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2021-144800 Summary of the Invention [Problem to be solved by the invention]

[0004] Incidentally, the manufacturing of an electricity storage device involves many steps, such as applying an electrode mixture onto a current collector and laminating it with a separator, and there has been a demand for simplifying the manufacturing process as much as possible. Although Patent Document 1 mentioned above can realize a gradual discharge mechanism in the event of an internal short circuit in a sheet-like electrode, it has not considered simplifying the manufacturing method as much as possible.

[0005] The present disclosure has been made in consideration of such problems, and has as its main object to provide a structure, an electricity storage device, and a method for manufacturing an electricity storage device that can simplify the manufacturing process as much as possible. [Means for solving the problem]

[0006] As a result of intensive research to achieve the above-mentioned object, the inventors discovered that the manufacturing process for an electricity storage device having sheet-like electrodes can be simplified by forming a current collector having openings on the front and back of a separator, and have completed the invention disclosed in this specification.

[0007] That is, the structure disclosed in this specification is A structure used in an electricity storage device, A separator; a positive electrode current collector having an opening formed on a first surface of the separator and communicating with the separator; a negative electrode current collector having an opening formed on a second surface of the separator and communicating with the separator; It is equipped with the following.

[0008] The electricity storage device disclosed in this specification comprises: The structure described above; a positive electrode mixture layer formed on the positive electrode current collector side; a negative electrode mixture layer formed on the negative electrode current collector side; It is equipped with the following.

[0009] The method for manufacturing an electricity storage device disclosed in the present specification includes the steps of: A method for manufacturing an electricity storage device, comprising: a positive electrode structure fabrication step of forming a positive electrode composite layer on the positive electrode current collector side of a structure including a separator, a positive electrode current collector having an opening formed on a first surface of the separator and communicating with the separator, and a negative electrode current collector having an opening formed on a second surface of the separator and communicating with the separator, to obtain a positive electrode structure; a negative electrode structure fabrication step of forming a negative electrode composite layer on the negative electrode current collector side of the structure to obtain a negative electrode structure; a lamination step of laminating the positive electrode structure and the negative electrode structure; It includes: [Effects of the Invention]

[0010] The present disclosure can simplify the manufacturing process as much as possible. The reason for this effect is believed to be as follows. For example, conventional energy storage devices such as lithium batteries constructed with sheet-like electrodes require three components: a separator, a positive electrode current collector foil, and a negative electrode current collector foil. In contrast, the present disclosure requires only one component: a separator structure on which positive and negative electrode current collectors are formed, making it easier to handle. Furthermore, in conventional structures, a positive electrode composite is applied to the surface of a positive electrode current collector, and then a positive electrode composite is applied again to the back surface of the positive electrode current collector. Similarly, in the case of negative electrodes, a negative electrode composite is applied to the surface of a negative electrode current collector, and then a negative electrode composite is applied again to the back surface of the negative electrode current collector, thereby obtaining positive / negative electrodes. Therefore, while conventional sheet-like electrodes require four composite applications, the present disclosure applies the positive electrode composite to the positive electrode current collector side of one structure, and then the negative electrode composite to the negative electrode current collector side of another structure, and then stacks these together. This reduces the composite application time to just two applications. Furthermore, while conventional sheet-type electrodes require three steps—laminating a separator on a positive electrode current collector with a positive electrode composite formed thereon, and then laminating a negative electrode current collector with a negative electrode composite formed thereon—the present disclosure requires only two steps: laminating a structure with a negative electrode composite formed thereon onto a structure with a positive electrode composite formed thereon. Furthermore, in conventional structures, because the metal current collectors are foil-shaped, the electrolyte solution only penetrates the electrodes in the plane direction after stacking, making the injection of the electrolyte time-consuming. In contrast, in the present disclosure, the positive and negative electrode current collectors have openings that communicate with the separator, allowing the electrolyte solution to penetrate not only in the plane direction but also in the thickness direction of the current collectors, thereby enabling smoother electrolyte penetration. Furthermore, in the present disclosure, the positive and negative electrode current collectors have openings, which reduces the proportion of current collectors in the stacked electrode, thereby increasing the proportion of positive and negative electrode active materials relative to each other, thereby improving energy density. In this way, the structure of the present disclosure can simplify the manufacturing process as much as possible. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a schematic diagram showing an example of a structure 10. FIG. [Figure 2] FIG. 2 is a schematic diagram showing an example of an electricity storage device 20. [Figure 3] FIG. 10 is a schematic diagram showing an example of another structure 10B. [Figure 4]FIG. 10 is a schematic diagram showing an example of another electricity storage device 20B. [Figure 5] FIG. 10 is an explanatory diagram of the number of constituent members in an example and a comparative example. [Figure 6] FIG. 2 is an explanatory diagram of the number of coating times in Examples and Comparative Examples. [Figure 7] FIG. 10 is an explanatory diagram of the number of laminations in an example and a comparative example. [Figure 8] FIG. 2 is an explanatory diagram illustrating impregnation of an electrolyte solution in an example and a comparative example. [Figure 9] FIG. 10 is an explanatory diagram of the embodiment when a partial short circuit occurs. DETAILED DESCRIPTION OF THE INVENTION

[0012] (structure) The structure of the present disclosure described in the embodiments is used in an electricity storage device. This structure includes a separator, a positive electrode current collector, and a negative electrode current collector. The separator is an insulating member that can impart ion conductivity. The positive electrode current collector is a conductive member formed on a first surface of the separator and has an opening communicating with the separator. The negative electrode current collector is a conductive member formed on a second surface of the separator and has an opening communicating with the separator.

[0013] The structure and the electricity storage device disclosed in this embodiment will be described with reference to the drawings. FIG. 1 is a schematic diagram showing an example of a structure 10. FIG. 2 is a schematic diagram showing an example of an electricity storage device 20. FIG. 3 is a schematic diagram showing an example of another structure 10B. FIG. 4 is a schematic diagram showing an example of another electricity storage device 20B. The structure 10 has a structure in which a positive electrode current collector 14 and a negative electrode current collector 17 are arranged in positions facing each other with a separator 13 interposed therebetween. The structure 10B has a structure in which the positive electrode current collector 14 and the negative electrode current collector 17 are arranged in positions shifted from each other with the separator 13 interposed therebetween. As shown in FIG. 1, the structure 10 has the positive electrode current collector 14 formed on a first surface 11 of the separator 13, and the negative electrode current collector 17 formed on a second surface 12 opposite to the first surface 11.

[0014] The separator 13 insulates the positive electrode 25 from the negative electrode 26 without inhibiting the ion conduction of carrier ions (e.g., lithium ions). The separator 13 is not particularly limited as long as it has a composition that can withstand the range of use of the structure 10. For example, the separator 13 may be made of a polyolefin resin such as polyethylene or polypropylene, a polyester resin such as polyethylene terephthalate or polybutylene terephthalate, polyvinylidene fluoride, a vinylidene fluoride-tetrafluoroethylene copolymer, a vinylidene fluoride-perfluoroethylene copolymer, a vinylidene fluoride-hexafluoropropylene copolymer, a vinylidene fluoride-trifluoroethylene copolymer, a vinylidene fluoride-fluoroethylene copolymer, a vinylidene fluoride-hexafluoroacetone copolymer, a vinylidene fluoride-ethylene copolymer, a vinylidene fluoride-propylene copolymer, a fluoride Examples of suitable separators include fluorine-based resins such as vinylidene-trifluoropropylene copolymer, vinylidene fluoride-tetrafluoroethylene-hexafluoropropylene copolymer, and vinylidene fluoride-ethylene-tetrafluoroethylene copolymer; polyvinylidene chloride, polyacrylonitrile, polyacrylamide, polysulfone, polyethersulfone, polycarbonate, polyamide, polyimide, polyethers such as polyethylene oxide and polypropylene oxide; celluloses such as carboxymethyl cellulose and hydroxypropyl cellulose; polymers and derivatives mainly composed of poly(meth)acrylic acid and other esters; and films made of copolymers or mixtures thereof. These may be used alone or in combination. These films may also contain additives to enhance ionic conductivity or various additives to improve strength and corrosion resistance. Among these microporous films, polyethylene, polypropylene, polyvinylidene fluoride, and polysulfone are preferred. The separator is preferably made microporous to allow the nonaqueous electrolyte to penetrate and ions to pass through. The thickness of the separator 13 is, for example, preferably 5 μm or more, more preferably 8 μm or more, and may be 10 μm or more. A thickness of 5 μm or more is preferable in terms of ensuring insulation.The thickness of the separator 13 is preferably 20 μm or less, more preferably 15 μm or less, and may be 10 μm or less. A thickness of 20 μm or less is preferable in that a decrease in ion conductivity can be suppressed and the volume occupied by the separator 13 in the cell can be further reduced.

[0015] The separator 13 may be a solid electrolyte as an ion-conducting medium. Examples of solid electrolytes include inorganic solid electrolytes and polymer solid electrolytes. The solid electrolyte is not limited to the following composition or structure, and may be any electrolyte that allows Li ions to move. As long as the basic skeleton is the compound exemplified below, it can be used even if it has a partial substitution product or a different composition ratio. Examples of inorganic solid electrolytes include LiN and LISICON, which are Li-based solid electrolytes. 14 Zn(GeO4)4, Li sulfide 3.25 Ge 0.25 P 0.75 S4, perovskite-type La 0.5 Li 0.5 TiO3, (La 2 / 3 Li 3x □ 1 / 3-2x )TiO3 (□: atomic vacancy), garnet-type Li7La3Zr2O 12 , LiTi2(PO4)3, called NASICON type, Li 1.3 M 0.3 Ti 1.7 (PO3)4 (M=Sc, Al), Li7P3S obtained from glass-ceramic 80Li2S·20P2S5 (mol%) glass. 11 Furthermore, Li, a sulfide-based material with high conductivity, 10Examples include Ge2PS2, glass-based inorganic solid electrolytes such as Li2S-SiS2, Li2S-SiS2-LiI, Li2S-SiS2-Li3PO4, Li2S-SiS2-Li4SiO4, Li2S-P2S5, Li3PO4-Li4SiO4, Li3BO4-Li4SiO4, and those using SiO2, GeO2, B2O3, and P2O5 as glass-based substances and Li2O as a network modifier. Examples of electrolytes include Li2S-GeS2-based, Li2S-GeS2-ZnS-based, Li2S-Ga2S2-based, Li2S-GeS2-Ga2S3-based, Li2S-GeS2-P2S5-based, Li2S-GeS2-SbS5-based, Li2S-GeS2-Al2S3-based, Li2S-SiS2-based, Li2S-P2S5-based, Li2S-Al2S3-based, LiS-SiS2-Al2S3-based, and Li2S-SiS2-P2S5-based.

[0016] Examples of polymer solid electrolytes include complexes of polyethylene oxide (PEO) and alkali metals. The polymer is not limited to PEO, and examples of unit structures of polymer materials that dissolve lithium salts include Polyether-based PEO, PPO: poly(propylene oxide), Polyamine-based PEI: poly(ethylene imine), PAN: poly(acrylonitrile), and Polysulfide-based PAS: poly(alkylene sulfide). Examples of lithium salts include LiTFSI: (LiN(SO2CF3)2), LiPEI: (COCF2SO2NLi)n, and LiPPI: (COCF(CF3OCF2CF2SO2NLi)). nExamples include gel polymer electrolytes using PVdF (Polyvinylidene DiFluoride), PAN, and HFP (Hexafluoropropylene). Organic ionic plastic electrolytes include those with a plastic crystalline phase. Representative molecules of the plastic crystalline phase include tetrachloromethane, cyclohexane, and succinonitrile. These plastic crystalline phases may be combined with TfN (trifluoromethylsulfonyl)amide or LiBF4, or with a salt containing a plastic crystalline phase consisting of an aliphatic quaternary ammonium salt and a perfluoroanion. Organic-inorganic hybrid ion gels, which combine ionic liquids and glass components at the molecular level, include organoboron-based ion gel electrolytes using cellulose, organoboron-based ion gel electrolytes using amylose, and poly-boron-substituted macrocycles derived from cyclodextrin.

[0017] The positive electrode current collector 14 is a comb-shaped member having current collector wires 14a, connecting portions 15, and openings 16. The current collector wires 14a are multiple linear members that are not electrically connected to each other at the portions adjacent to and in contact with the positive electrode active material. The current collector wires 14a may have a square or rectangular cross-sectional shape, or may be a polygonal columnar shape such as a circular columnar, elliptical columnar, hexagonal columnar, or octagonal columnar. The connecting portions 15 are continuous members that connect multiple current collector wires 14a in parallel outside the area where the current collector wires 14a and the positive electrode active material are not in contact. The connecting portions 15 are foil- or plate-shaped members whose longitudinal direction is the arrangement direction of the current collector wires 14a. The openings 16 are spaces that communicate with the separator 13 and are formed between the current collector wires 14a. The positive electrode current collector 14 has multiple openings 16. Opening 16 is filled with positive electrode mixture layer 21 .

[0018] The current collector 14a can be made of copper, nickel, stainless steel, titanium, aluminum, calcined carbon, conductive polymer, conductive glass, Al-Cd alloy, etc., or, for example, copper whose surface has been treated with carbon, nickel, titanium, silver, etc. to improve adhesion, conductivity, and reduction resistance. These surfaces can also be oxidized. The current collector 14a preferably has a width t of 100 μm or more and a width s of the opening 16 of 100 μm or more and a width s of 100 μm or more and a width s of 500 μm or less. The widths t and s may be the same or different, but considering support during stacking, it is preferable that they be the same. The width t of the current collector 14a is more preferably 200 μm or more and may be 250 μm or more. The width t of the current collector 14a is more preferably 400 μm or less and may be 300 μm or less. The width s of the opening 16 is more preferably 200 μm or more and may be 250 μm or more. Furthermore, the width s of the opening 16 is more preferably 400 μm or less, and may be 300 μm or less. The length L of the current collector 14a may be selected appropriately according to the characteristics required of the electricity storage device 20, and may be, for example, 5 cm or more, or 10 cm or more to 20 cm or more. The length of the opening 16 may also be the same as the length L of the current collector 14a.

[0019] The connection portion 15 may be configured such that the number M of collector wires 14a connected in parallel is 100 or more, or may be configured such that the number M of collector wires 14a connected in parallel is 200 or more, or 500 or more. Since the resistance applied to the unit cell 23 via the connection portion 15 is determined depending on the number M of parallel connections, the number M of parallel-connected collector wires 14a and the volume resistivities of the connection portion 15 and collector wires 14a may be appropriately set depending on the desired charge / discharge characteristics. Furthermore, since the amount of negative electrode active material per unit volume decreases as the number M of collector wires 14a increases, the number M of collector wires 14a may be appropriately set taking into account the energy density. This positive electrode current collector 14 has a volume resistivity of 1.0 × 10 -7 The positive electrode current collector 14 may have a volume resistivity of 5.0×10 -8 The volume resistivity may be 2.0×10 -8The volume resistivity of the current collector 14a and the connection portion 15 may be the same or different.

[0020] The negative electrode current collector 17 is a comb-shaped member having current collector wires 17a, connecting portions 18, and openings 19. The current collector wires 17a are multiple linear members that are not electrically connected to each other in the portions adjacent to the negative electrode composite layer 22 and in contact with the negative electrode active material. The current collector wires 17a may have a square or rectangular cross-sectional shape, or may be a polygonal columnar shape such as a circular columnar, elliptical columnar, hexagonal columnar, or octagonal columnar. The connecting portions 18 are continuous members that connect multiple current collector wires 17a in parallel outside the area where the current collector wires 17a and the negative electrode active material are not in contact. The connecting portions 18 are foil- or plate-shaped members whose longitudinal direction is the arrangement direction of the current collector wires 17a. The openings 19 are spaces that communicate with the separator 13 and are formed between the current collector wires 17a. The negative electrode current collector 17 has multiple openings 19. Opening 19 is filled with negative electrode composite material layer 22. Negative electrode current collector 17 may have the same shape as positive electrode current collector 14, or may have a different shape.

[0021] The current collector 17a can be made of copper, nickel, stainless steel, titanium, aluminum, calcined carbon, conductive polymer, conductive glass, Al-Cd alloy, etc., or, for example, copper whose surface has been treated with carbon, nickel, titanium, silver, etc. to improve adhesion, conductivity, and reduction resistance. These surfaces can also be oxidized. The current collector 17a preferably has a width t of 100 μm or more and a width s of the opening 19 of 100 μm or more and a width s of 100 μm or more and a width s of 500 μm or less. The widths t and s may be the same or different, but are preferably the same considering support during stacking. The width t of the current collector 17a is more preferably 200 μm or more and may be 250 μm or more. The width t of the current collector 17a is more preferably 400 μm or less and may be 300 μm or less. The width s of the opening 19 is more preferably 200 μm or more and may be 250 μm or more. Furthermore, the width s of the opening 19 is more preferably 400 μm or less, and may be 300 μm or less. The length L of the current collector 17a may be selected appropriately according to the characteristics required of the electricity storage device 20, and may be, for example, 5 cm or more, or 10 cm or more to 20 cm or more. The length of the opening 19 may also be the same as the length L of the current collector 17a.

[0022] The connection portion 18 may be configured such that the number N of collector wires 17a connected in parallel is 100 or more, or may be configured such that the number N of collector wires 17a connected in parallel is 200 or more, or 500 or more. The resistance applied to the unit cell 23 via the connection portion 18 is determined depending on the number N of parallel connections. Therefore, the number N of parallel connections of collector wires 17a and the volume resistivities of the connection portion 18 and collector wires 17a may be appropriately set depending on the desired charge / discharge characteristics. Furthermore, since the amount of negative electrode active material per unit volume decreases as the number N of collector wires 17a increases, the number N of collector wires 17a may be appropriately set taking into account the energy density. This negative electrode current collector 17 has a volume resistivity of 1.0 × 10 -7 The negative electrode current collector 17 may have a volume resistivity of 5.0×10 -8 The volume resistivity may be 2.0×10 -8The volume resistivity of the current collector 17a and the connection portion 18 may be the same or different.

[0023] The aperture 16 preferably has an aperture ratio of 20% or more in terms of area ratio. This aperture ratio refers to the ratio of the area of ​​the aperture 16 to the area of ​​the entire region including the current collector wire 14a of the positive electrode current collector 14, excluding the area of ​​the connection portion 15. From the viewpoint of carrier ion conduction, a larger aperture ratio is preferable, and from the viewpoint of electrical conductivity, a smaller aperture ratio is preferable. The aperture ratio is preferably 30% or more, more preferably 40% or more, and may be 50% or more. The aperture ratio is preferably 80% or less, more preferably 70% or less, and may be 60% or less. The aperture 19 may have the same aperture ratio as the aperture 16, or may have a different aperture ratio. Note that the aperture 19 is assumed to be the same as the aperture 16, and a detailed description thereof will be omitted.

[0024] (Electricity storage device) As shown in FIG. 2 , the electricity storage device 20 includes a structure 10, a positive electrode composite layer 21 formed on the positive electrode current collector 14 side, and a negative electrode composite layer 22 formed on the negative electrode current collector 17 side. The positive electrode 25 is composed of the positive electrode current collector 14 and the positive electrode composite layer 21, and the negative electrode 26 is composed of the negative electrode current collector 17 and the negative electrode composite layer 22. The electricity storage device 20 may be, for example, an electric double layer capacitor, a hybrid capacitor, a pseudo-electric double layer capacitor, an alkali metal secondary battery, or an alkali metal ion battery. Examples of carrier ions in the electricity storage device 20 include alkali metal ions such as lithium ions, sodium ions, and potassium ions, and Group 2 ions such as magnesium ions, strontium ions, and calcium ions. The electricity storage device 20 may also include an ion-conductive medium in one or more of the positive electrode 25, the negative electrode 26, and the separator 13. For the sake of convenience, the following description will be given taking a lithium ion secondary battery, which uses lithium ions as a carrier, as a main example.

[0025] The positive electrode 25 may include a positive electrode composite material layer 21 and a positive electrode current collector 14. The positive electrode composite material layer 21 may include a positive electrode active material, a conductive material as needed, and a binder. The positive electrode 25 may be formed by, for example, mixing a positive electrode active material, a conductive material, and a binder, adding an appropriate solvent to form a paste-like positive electrode composite material, applying and drying it on the side of the positive electrode current collector 14 of the structure 10, and compressing it as needed to increase the electrode density. Examples of the positive electrode active material include materials capable of occluding and releasing lithium as a carrier. Examples of the positive electrode active material include compounds having lithium and a transition metal, such as oxides containing lithium and a transition metal element, and phosphate compounds containing lithium and a transition metal element. Specifically, the basic composition formula is Li (1-x) MnO2 (0 ≦ x ≦ 1, etc., the same hereinafter), Li (1-x) Mn2O4, etc., lithium manganese composite oxides, the basic composition formula is Li (1-x) CoO2, etc., lithium cobalt composite oxides, the basic composition formula is Li (1-x) NiO2, etc., lithium nickel composite oxides, the basic composition formula is Li (1-x) Co a Ni b Mn c O2 (a > 0, b > 0, c > 0, a + b + c = 1), Li (1-x) Co a Ni b Mn c O4 (0 < a < 1, 0 < b < 1, 1 ≦ c < 2, a + b + c = 2), etc., lithium cobalt nickel manganese composite oxides, the basic composition formula is LiV2O3, etc., lithium vanadium composite oxides, the basic composition formula is V2O5, etc., transition metal oxides, etc. can be used. Also, a lithium iron phosphate compound having a basic composition formula of LiFePO4, etc., can be used as the positive electrode active material. Among these, lithium cobalt nickel manganese composite oxides, such as LiCo 1 / 3 Ni 1 / 3 Mn 1 / 3 O2 and LiNi 0.4 Co 0.3 Mn 0.3 O2, etc., are preferable. Note that the "basic composition formula" means that it may contain components of other elements, such as Al and Mg.

[0026] The conductive material is not particularly limited as long as it is an electronically conductive material that does not adversely affect the battery performance of the positive electrode. For example, graphite such as natural graphite (scale graphite, flake graphite) and artificial graphite, acetylene black, carbon black, ketjen black, carbon whiskers, needle coke, carbon fiber, and metals (copper, nickel, aluminum, silver, gold, etc.) can be used alone or in combination of two or more. Among these, carbon black and acetylene black are preferred as the conductive material from the viewpoints of electronic conductivity and coatability. The binder serves to bind the active material particles and the conductive material particles together, and examples thereof include fluorine-containing resins such as polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVdF), and fluororubber, thermoplastic resins such as polypropylene and polyethylene, ethylene propylene diene rubber (EPDM), sulfonated EPDM rubber, and natural butyl rubber (NBR), which can be used alone or in combination of two or more. Aqueous binders such as cellulose-based binders or aqueous dispersions of styrene-butadiene rubber (SBR) can also be used. Examples of solvents that can be used to disperse the positive electrode active material, conductive material, and binder include organic solvents such as N-methylpyrrolidone, dimethylformamide, dimethylacetamide, methyl ethyl ketone, cyclohexanone, methyl acetate, methyl acrylate, diethylenetriamine, N,N-dimethylaminopropylamine, ethylene oxide, and tetrahydrofuran. Alternatively, a dispersant, thickener, or the like can be added to water, and the active material can be slurried with a latex such as SBR. Examples of thickeners that can be used include polysaccharides such as carboxymethylcellulose and methylcellulose, either alone or in combination. Examples of application methods include roller coating (e.g., applicator roll), screen coating, doctor blade coating, spin coating, and bar coating. Any of these methods can be used to create a desired thickness and shape.

[0027] In the positive electrode 25, the content of the positive electrode active material is preferably higher, preferably 70% by mass or more, and more preferably 80% by mass or more, relative to the total mass of the positive electrode 25. The content of the conductive material is preferably in the range of 0% by mass to 20% by mass or less, and more preferably 0% by mass to 10% by mass or less, relative to the total mass of the positive electrode 25. Within such a range, a decrease in battery capacity can be suppressed and sufficient conductivity can be imparted. Furthermore, the content of the binder is preferably in the range of 0.1% by mass to 5% by mass or less, and more preferably 0.2% by mass to 3% by mass, relative to the total mass of the positive electrode 25.

[0028] The negative electrode 26 includes a negative electrode composite layer 22 and a negative electrode current collector 17. The negative electrode 26 may be formed by closely adhering the negative electrode composite layer 22 and the negative electrode current collector 17. Alternatively, the negative electrode 26 may be formed by, for example, mixing a negative electrode active material, a conductive material, and a binder, adding an appropriate solvent to form a paste-like negative electrode composite, applying the paste to the negative electrode current collector 17 side of the structure 10, drying the mixture, and compressing it as needed to increase electrode density. The negative electrode composite layer 22 may include a negative electrode active material, a conductive material, and a binder. Examples of negative electrode active materials include inorganic compounds such as lithium, lithium alloys, and tin compounds; carbonaceous materials capable of absorbing and releasing lithium ions; composite oxides containing multiple elements; and conductive polymers. Examples of carbonaceous materials include cokes, glassy carbons, graphites, non-graphitizable carbons, pyrolytic carbons, and carbon fibers. Among these, graphites such as artificial graphite and natural graphite are preferred because they have an operating potential close to that of metallic lithium, allowing for charging and discharging at high operating voltages, and when a lithium salt is used as a supporting electrolyte, they suppress self-discharge and reduce irreversible capacity during charging. Examples of composite oxides include lithium-titanium composite oxide and lithium-vanadium composite oxide. Of these, carbonaceous materials are preferred as negative electrode active materials from the standpoint of safety. The conductive material, binder, solvent, and the like used in the negative electrode 26 can be the same as those exemplified for the positive electrode 25.

[0029] In the negative electrode 26, the content of the negative electrode active material is preferably higher, and is preferably 70 mass% or more, and more preferably 80 mass% or more, relative to the total mass of the negative electrode 26. The content of the conductive material is preferably in the range of 0 mass% to 20 mass% and more preferably 0 mass% to 10 mass% relative to the total mass of the negative electrode 26. Within such a range, a decrease in battery capacity can be suppressed and sufficient conductivity can be imparted. Furthermore, the content of the binder is preferably in the range of 0.1 mass% to 5 mass% and more preferably 0.2 mass% to 3 mass% relative to the total mass of the negative electrode 26.

[0030] As the ion-conducting medium, a non-aqueous electrolyte solution containing a supporting salt or a non-aqueous gel electrolyte solution can be used. Examples of solvents for the non-aqueous electrolyte solution include carbonates, esters, ethers, nitriles, furans, sulfolanes, and dioxolanes, which can be used alone or in combination. Specific examples of carbonates include cyclic carbonates such as ethylene carbonate (EC), propylene carbonate, vinylene carbonate, butylene carbonate, and chloroethylene carbonate; chain carbonates such as dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), diethyl carbonate, ethyl-n-butyl carbonate, methyl-t-butyl carbonate, di-i-propyl carbonate, and t-butyl-i-propyl carbonate; and γ-butyl carbonate. Examples of suitable electrolytes include cyclic esters such as hydroxyl lactone and γ-valerolactone; chain esters such as methyl formate, methyl acetate, ethyl acetate, and methyl butyrate; ethers such as dimethoxyethane, ethoxymethoxyethane, and diethoxyethane; nitriles such as acetonitrile and benzonitrile; furans such as tetrahydrofuran and methyltetrahydrofuran; sulfolanes such as sulfolane and tetramethylsulfolane; and dioxolanes such as 1,3-dioxolane and methyldioxolane. The electrolyte may also contain a supporting salt containing ions that serve as carriers for the structure 10. Examples of supporting salts include LiPF, LiBF, LiAsF, LiCFSO, LiN(CFSO), LiC(CFSO), LiSbF, LiSiF, LiAlF, LiSCN, LiClO, LiCl, LiF, LiBr, LiI, and LiAlCl. Among these, it is preferable to use a combination of one or more salts selected from the group consisting of inorganic salts such as LiPF6, LiBF4, and LiClO4, and organic salts such as LiCF3SO3, LiN(CF3SO2)2, and LiC(CF3SO2)3, from the viewpoint of electrical properties. The concentration of this supporting salt in the electrolyte is preferably 0.1 mol / L or more and 5 mol / L or less, and more preferably 0.5 mol / L or more and 2 mol / L or less.

[0031] From the viewpoint of safety, the gradual discharge function of the electricity storage device 20 when an internal short circuit occurs from a fully charged state is preferably longer, for example, preferably 30 minutes or more, more preferably 1 hour or more, and even more preferably 2 hours or more. If this gradual discharge function is longer, sudden discharge when a partial short circuit occurs inside the cell can be further suppressed, and safety can be further ensured. From the viewpoint of energy density, such as an increase in the resistance of the structure 10, this gradual discharge function may be set to 5 hours or less.

[0032] In the electricity storage device 20, as shown in FIGS. 1 and 2, the current collector 14a and the current collector 17a are arranged to face each other with the separator 13 interposed therebetween, but as shown in FIGS. 3 and 4, an electricity storage device 20B may be configured in which the current collector 14a and the current collector 17a are arranged to be offset from each other with the separator 13 interposed therebetween. Note that the structure 10B and the single cell 23B are similar to the structure 10 and the single cell 23 except for the position of the current collector. In consideration of the conduction of carrier ions, the electricity storage device 20 is preferable.

[0033] The shape of the electricity storage device 20 is not particularly limited, and examples thereof include a coin type, a button type, a sheet type, a laminated type, a cylindrical type, a flat type, a rectangular type, etc. Furthermore, a plurality of such batteries may be connected in series to be applied to a large device used in an electric vehicle or the like.

[0034] (Method of manufacturing an electricity storage device) The method for manufacturing an electricity storage device includes a positive electrode structure fabrication step, a negative electrode structure fabrication step, and a lamination step, and may further include an ion conductive medium impregnation step. Alternatively, the method may include a structure preparation step as an initial step. Note that in this manufacturing method, the methods described above for the structures 10 and 10B and the electricity storage devices 20 and 20B may be used as appropriate, and detailed description thereof will be omitted.

[0035] (Structure preparation process) In this step, a structure 10 is prepared. As described above, the structure 10 includes a separator 13, a positive electrode current collector 14 having an opening 16 formed on a first surface 11 of the separator 13 and communicating with the separator 13, and a negative electrode current collector 17 having an opening 19 formed on a second surface 12 of the separator 13 and communicating with the separator 13. In this step, the structure 10 may be produced by forming the positive electrode current collector 14 on the first surface 11 of the separator 13 and forming the negative electrode current collector 17 on the second surface 12.

[0036] (Positive electrode structure manufacturing process) In this step, a positive electrode mixture layer 21 is formed on the positive electrode current collector 14 side of the structure 10 to obtain a positive electrode structure. The positive electrode mixture layer 21 can be formed by appropriately adopting the same as that described for the electricity storage device 20. The thickness of the positive electrode mixture layer 21 may be, for example, 50 μm or more, 80 μm or more, or 100 μm or more. The thickness of the positive electrode mixture layer 21 may be 200 μm or less, 150 μm or less, or 120 μm or less. The thickness of the positive electrode mixture layer 21 may be selected appropriately in accordance with the characteristics of the electricity storage device 20.

[0037] (Negative electrode structure manufacturing process) In this step, a negative electrode mixture layer 22 is formed on the negative electrode current collector 17 side of the structure 10 to obtain a negative electrode structure. The negative electrode mixture layer 22 can be formed by appropriately adopting those described in connection with the electricity storage device 20. The thickness of the negative electrode mixture layer 22 may be, for example, 50 μm or more, 80 μm or more, or 100 μm or more. The thickness of the negative electrode mixture layer 22 may be 200 μm or less, 150 μm or less, or 120 μm or less. The thickness of the negative electrode mixture layer 22 may be appropriately selected in accordance with the characteristics of the electricity storage device 20.

[0038] (Lamination process) In this step, the obtained positive electrode structure and the negative electrode structure are laminated. In the lamination step, the negative electrode structure is laminated so that the negative electrode composite layer 22 of the negative electrode structure faces the negative electrode current collector 17 side of the positive electrode structure. Alternatively, the positive electrode composite layer 21 of the positive electrode structure faces the positive electrode current collector 14 side of the negative electrode structure. In this step, the laminate obtained by lamination may be pressed under pressure. By applying pressure, the composite layer fills the openings 16 of the positive electrode current collector 14 and the openings 19 of the negative electrode current collector 17.

[0039] (Ion conductive medium impregnation process) In this step, the laminate obtained above is placed in a cell case, and an ion-conductive medium, particularly an electrolyte, is impregnated into the laminate. This laminate allows the electrolyte to pass through openings 16 in positive electrode current collector 14 and openings 19 in negative electrode current collector 17, so the impregnation process can be carried out quickly.

[0040] The structure 10 and the electricity storage device 20 described in detail above can simplify the manufacturing process as much as possible. The reason for this effect is presumed to be as follows. For example, electricity storage devices such as lithium batteries configured with conventional sheet-like electrodes require three components: a separator, a positive electrode current collector foil, and a negative electrode current collector foil. In contrast, the present disclosure requires only one component: a separator structure on which positive and negative electrode current collectors are formed, making it easy to handle. Furthermore, in the conventional structure, a positive electrode composite is applied to the surface of a positive electrode current collector, and then a positive electrode composite is applied again to the back surface of the positive electrode current collector. Similarly, in the case of a negative electrode, a negative electrode composite is applied to the surface of a negative electrode current collector, and then a negative electrode composite is applied again to the back surface of the negative electrode current collector, thereby obtaining positive and negative electrodes. Therefore, while conventional sheet-type electrodes require four applications of the composite, the present disclosure applies the composite only two times by applying the positive electrode composite to the positive electrode current collector side of one structure and the negative electrode composite to the negative electrode current collector side of another structure and then stacking them. Furthermore, conventional sheet-type electrodes require three steps: laminating a separator on top of a positive electrode current collector on which a positive electrode composite has been formed, and then laminating a negative electrode current collector on which a negative electrode composite has been formed. However, the present disclosure requires only two steps: laminating a structure on which a negative electrode composite has been formed on top of a structure on which a positive electrode composite has been formed. Furthermore, in conventional structures, because the metal current collectors are foil-shaped, the electrolyte solution can only penetrate the electrodes in the plane direction after stacking, which requires time for electrolyte injection. In contrast, the present disclosure provides openings in the positive and negative electrode current collectors that communicate with the separator, allowing the electrolyte solution to penetrate not only in the plane direction but also in the thickness direction of the current collectors, thereby enabling smoother electrolyte penetration. Furthermore, in the present disclosure, the positive and negative electrode current collectors have openings, which reduces the proportion of the current collectors in the stacked electrode, thereby relatively increasing the proportion of positive and negative electrode active materials, thereby improving energy density. In this way, the structure of the present disclosure can simplify the manufacturing process as much as possible. Furthermore, in the structure 10, by arranging the comb-shaped positive and negative electrode current collectors on the front and back of the separator, the current path in the event of an internal short circuit becomes highly resistant, suppressing current concentration in the event of an internal short circuit, thereby significantly improving safety.

[0041] It goes without saying that the present disclosure is not limited to the above-described embodiments, and can be embodied in various forms as long as they fall within the technical scope of the present disclosure.

[0042] For example, in the above-described embodiment, the carrier of the power storage device is lithium ion, but is not limited thereto, and may be alkali metal ion such as sodium ion or potassium ion, or Group 2 element ion such as calcium ion or magnesium ion. The positive electrode active material may contain carrier ions. The electrolyte solution is a non-aqueous electrolyte solution, but may be an aqueous electrolyte solution.

[0043] In the above-described embodiment, the positive electrode active material is a transition metal composite oxide, but it is not particularly limited thereto, and may be, for example, a carbon material used in a capacitor. The carbon material is not particularly limited, but examples thereof include activated carbons, cokes, glassy carbons, graphites, non-graphitizable carbons, pyrolytic carbons, carbon fibers, carbon nanotubes, and polyacenes. Among these, activated carbons exhibiting a high specific surface area are preferred. Activated carbons as carbon materials have a specific surface area of ​​1000 m 2 / g or more, and 1500m 2 / g or more is more preferable. 2 / g or more, the discharge capacity can be further increased. The specific surface area of ​​this activated carbon is 3000m due to the ease of production. 2 / g or less is preferred, and 2000m 2 / g or less is more preferable. It is thought that electricity is stored by adsorbing and desorbing at least one of the anions and cations contained in the conductive medium, but it may also be stored by inserting and desorbing at least one of the anions and cations contained in the ion conductive medium.

[0044] In the above-described embodiment, the positive electrode current collector 14 and the negative electrode current collector 17 have a comb-like shape, but are not limited thereto as long as they have openings, and the positive electrode current collector 14 and the negative electrode current collector 17 may be sheet-shaped current collectors with one or more circular, elliptical, rectangular, polygonal, or other openings formed therein. Even in this structure, there is a space communicating from the opening to the separator 13, and the separator, the positive electrode current collector, and the negative electrode current collector 17 are integrally formed, so that the manufacturing process can be simplified as much as possible. [Example]

[0045] Hereinafter, examples in which the above-described structure, electricity storage device, and method for manufacturing the electricity storage device have been specifically considered will be described as examples.

[0046] The structure and the electricity storage device using the same of the present disclosure are used as examples, and the electricity storage device having a general coated electrode using a sheet-shaped current collector foil is used as a comparative example. The structure of the example used a polyethylene separator with a thickness of 15 μm. The positive electrode current collector 14 was comb-shaped and made of Al, with a current collector length of 70 mm, a width t of 335 μm, and a thickness of 7 μm. The negative electrode current collector 17 was comb-shaped and made of Cu, with a current collector length of 70 mm, a width t of 200 μm, and a thickness of 7 μm. In the electricity storage device 20, the positive electrode composite layer 21 had a thickness of 120 μm, and the negative electrode active material layer had a thickness of 100 μm. In the comparative example, a polyethylene separator with a thickness of 15 μm was used. The positive electrode current collector was sheet-shaped and made of Al, with a thickness of 10 μm. The negative electrode current collector was in the form of a sheet made of Cu and had a thickness of 20 μm. In the comparative electricity storage device, the positive electrode mixture layer had a thickness of 60 μm, and the negative electrode active material layer had a thickness of 50 μm.

[0047] Fig. 5 is an explanatory diagram of the number of constituent parts in the Example and the Comparative Example. As shown in Fig. 5, the Comparative Example, which is composed of conventional sheet-like electrodes, requires three types of components: a separator, a positive electrode current collector foil, and a negative electrode current collector foil. However, the Example requires only one type of structure, a separator on which positive and negative electrode current collectors are formed, making it easy to handle. Furthermore, the reduction in the number of parts simplifies the management of components during manufacturing, which is also beneficial in terms of stock space and inventory management, and also contributes to cost reduction.

[0048] FIG. 6 is an explanatory diagram of the number of coating times in the example and the comparative example. As shown in FIG. 6, in the comparative example of the conventional structure, a positive electrode composite is applied to the surface of a positive electrode current collector, and then a positive electrode composite is applied again to the back surface of the positive electrode current collector. Similarly, in the negative electrode, a negative electrode composite is applied to the surface of a negative electrode current collector, and then a negative electrode composite is applied again to the back surface of the negative electrode current collector to obtain positive / negative electrodes. Therefore, in the comparative example, the composite must be applied four times. On the other hand, in the example, the positive electrode composite is applied to the positive electrode current collector side of one structure, and the negative electrode composite is applied to the negative electrode current collector side of another structure, so that the composite only needs to be applied twice. In this case, the positive electrode composite and the negative electrode composite can be formed to twice the thickness compared to the comparative example. In this way, the process of forming the composite layer can be reduced, thereby simplifying the manufacturing process as much as possible. Coating the composite layer requires a long process time, including drying, and a large amount of energy, so halving the number of coating times is extremely effective and also leads to cost reductions.

[0049] FIG. 7 is an explanatory diagram of the number of stacking steps in the example and the comparative example. As shown in FIG. 7, the comparative example of the conventional structure requires three steps: stacking a separator on a positive electrode current collector on which a positive electrode composite is formed, and then stacking a negative electrode current collector on which a negative electrode composite is formed. On the other hand, the example requires only two steps: stacking a structure on which a negative electrode composite is formed on a structure on which a positive electrode composite is formed. In this way, the example can reduce the number of assembly steps, thereby simplifying the manufacturing process as much as possible. Furthermore, the assembly work in the stacking process needs to be performed with high positional accuracy, and an increase in the number of steps takes time and increases the possibility of producing defective products. This reduction in assembly work is extremely effective, and it can also lead to cost reduction.

[0050] FIG. 8 is an explanatory diagram of the impregnation of an electrolyte solution in an example and a comparative example. As shown in FIG. 8, in the comparative example with a conventional structure, because the metal current collectors are foil-shaped, the electrolyte solution only penetrates the electrodes in the plane direction after stacking, which makes the injection of the electrolyte time-consuming. On the other hand, in the example, the positive and negative electrode current collectors have openings that communicate with the separator, so the electrolyte penetrates the current collectors not only in the plane direction but also in the thickness direction, allowing for smoother electrolyte penetration. Generally, the electrode shape is 10 cm to several tens of cm in the horizontal direction in FIG. 8 and approximately 1 cm or less in the vertical direction. Therefore, in the comparative example, where the electrolyte solution cannot penetrate from the top and bottom, the injection takes an extremely long time. On the other hand, in the example, the injection time can be significantly reduced, which is extremely effective and also contributes to cost reduction. Furthermore, in the example, the positive and negative electrode current collectors have openings, which reduces the proportion of the current collectors in the stacked electrode, thereby relatively increasing the proportion of positive and negative electrode active materials and improving energy density.

[0051] Figure 9 is an explanatory diagram of a partial short circuit in an example. As shown in Figure 9, normal charging and discharging is performed without any problems even when the current collectors are arranged in a striped pattern. However, if an internal short circuit occurs within the electrode and all current is concentrated at the shorted location, current tends to concentrate in the current collectors near the shorted location. However, because a single current collector has a much smaller volume than a continuous current collector foil, its resistance increases even when using materials with the same volume resistivity. As a result, the current concentrated at the shorted location decreases, and the current discharges slowly over a long period of time, resulting in a so-called gradual discharge. This significantly reduces Joule heating at the shorted location, ensuring safety. Although the resistance of a single current collector increases, the current flowing through a single current collector during normal use is small, only for the electrode near the current collector, so it flows without any problems. In other words, the current collector resistance within the electrode for the entire cell is reduced to the value obtained by dividing the current collector resistance by the number of current collectors. In other words, by connecting a large number of relatively high resistance collector wires in parallel, the collector resistance of the entire cell can be designed to be low, allowing for smooth charging and discharging.If an internal short circuit occurs anywhere, the discharge will be gradual as it will pass through a single high resistance collector wire, ensuring a high level of safety.

[0052] As described above, in the structures and energy storage devices of the examples, the manufacturing process can be simplified as much as possible by arranging the positive electrode / negative electrode current collectors having openings on the front and back of the separator. Furthermore, the examples can also reduce the manufacturing time and material management. Furthermore, the examples can further increase the energy density, and the current path in the event of an internal short circuit becomes highly resistive, suppressing current concentration in the event of an internal short circuit, thereby significantly improving safety.

[0053] It goes without saying that the present disclosure is not limited to the above-described embodiments, and can be embodied in various forms as long as they fall within the technical scope of the present disclosure. [Explanation of symbols]

[0054] 10, 10B: Structure, 11: First surface, 12: Second surface, 13: Separator, 14: Positive electrode current collector, 14a: Current collector, 15: Connection portion, 16: Opening, 17: Negative electrode current collector, 17a: Current collector, 18: Connection portion, 19: Opening, 20, 20B: Energy storage device, 21: Positive electrode composite layer, 22: Negative electrode composite layer, 23, 23B: Single cell, 25: Positive electrode, 26: Negative electrode, M, N: Number, L: Length, t: Width, s: Width.

Claims

1. A structure used in an electricity storage device, A separator; a positive electrode current collector having an opening formed on a first surface of the separator and communicating with the separator; a negative electrode current collector formed on the second surface of the separator and having an opening communicating with the separator, The positive electrode current collector and / or the negative electrode current collector have a comb-like shape.

2. The structure according to claim 1 , wherein the opening ratio of the openings in the positive electrode current collector and / or the negative electrode current collector is 20% or more in terms of area ratio.

3. the positive electrode current collector has a positive electrode current collecting portion at an end thereof that does not have the opening, the negative electrode current collector has a negative electrode current collecting portion at an end thereof that does not have the opening, The structure according to claim 1 or 2, wherein the positive electrode current collecting portion and the negative electrode current collecting portion are formed on opposite sides.

4. The structure according to any one of claims 1 to 3, comprising at least one of a positive electrode mixture layer formed on the positive electrode current collector side and / or a negative electrode mixture layer formed on the negative electrode current collector side.

5. The structure according to any one of claims 1 to 4, a positive electrode mixture layer formed on the positive electrode current collector side; a negative electrode mixture layer formed on the negative electrode current collector side; An electricity storage device comprising:

6. A method for manufacturing an electricity storage device, comprising: a positive electrode structure fabrication step of forming a positive electrode composite layer on the positive electrode current collector side of a structure including a separator, a positive electrode current collector having an opening formed on a first surface of the separator and communicating with the separator, and a negative electrode current collector having an opening formed on a second surface of the separator and communicating with the separator, to obtain a positive electrode structure; a negative electrode structure fabrication step of forming a negative electrode composite layer on the negative electrode current collector side of the structure to obtain a negative electrode structure; a lamination step of laminating the positive electrode structure and the negative electrode structure; A method for manufacturing an electricity storage device comprising:

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