WO2020090932A1 - Power storage device - Google Patents

Power storage device Download PDF

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Publication number
WO2020090932A1
WO2020090932A1 PCT/JP2019/042670 JP2019042670W WO2020090932A1 WO 2020090932 A1 WO2020090932 A1 WO 2020090932A1 JP 2019042670 W JP2019042670 W JP 2019042670W WO 2020090932 A1 WO2020090932 A1 WO 2020090932A1
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WO
WIPO (PCT)
Prior art keywords
active material
electrode active
material layer
positive electrode
power storage
Prior art date
Application number
PCT/JP2019/042670
Other languages
French (fr)
Japanese (ja)
Inventor
晶 小島
厚志 南形
聡 河野
祐樹 杉本
卓郎 菊池
素宜 奥村
正人 穂積
Original Assignee
株式会社豊田自動織機
トヨタ自動車株式会社
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by 株式会社豊田自動織機, トヨタ自動車株式会社 filed Critical 株式会社豊田自動織機
Priority to JP2020554006A priority Critical patent/JP7057440B2/en
Publication of WO2020090932A1 publication Critical patent/WO2020090932A1/en

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES OR LIGHT-SENSITIVE DEVICES, OF THE ELECTROLYTIC TYPE
    • H01G11/00—Hybrid capacitors, i.e. capacitors having different positive and negative electrodes; Electric double-layer [EDL] capacitors; Processes for the manufacture thereof or of parts thereof
    • H01G11/22—Electrodes
    • H01G11/26—Electrodes characterised by their structure, e.g. multi-layered, porosity or surface features
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES OR LIGHT-SENSITIVE DEVICES, OF THE ELECTROLYTIC TYPE
    • H01G11/00—Hybrid capacitors, i.e. capacitors having different positive and negative electrodes; Electric double-layer [EDL] capacitors; Processes for the manufacture thereof or of parts thereof
    • H01G11/66—Current collectors
    • H01G11/70—Current collectors characterised by their structure
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/04—Construction or manufacture in general
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/24—Electrodes for alkaline accumulators
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/64—Carriers or collectors
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
    • Y02P70/50—Manufacturing or production processes characterised by the final manufactured product

Definitions

  • the present disclosure relates to a power storage device.
  • bipolar type power storage device including a bipolar electrode in which a positive electrode active material layer is provided on one surface of a current collector and a negative electrode active material layer is provided on the other surface.
  • An electrolytic solution is enclosed in the case of such a power storage device.
  • the electrolytic solution flows to some extent in the case during charging and discharging.
  • the positive electrode active material layer the positive electrode active material expands during charging and the electrolytic solution flows in, and during discharging, the positive electrode active material contracts and the electrolytic solution flows out. If the electrolyte solution flowing into the positive electrode active material layer during charging is insufficient, battery characteristics may deteriorate.
  • the present disclosure describes a power storage device with improved battery characteristics.
  • a power storage device includes a current collector, a positive electrode active material layer provided on a first surface of the current collector, a negative electrode active material layer provided on a second surface of the current collector, A plurality of bipolar electrodes each including the above are provided, a laminated body laminated via a separator, a case surrounding a side surface of the laminated body, and an electrolytic solution enclosed in the case.
  • the first surface of the current collector has a roughened roughened area on at least a part of the first surface. At least a part of the positive electrode active material layer is provided in the rough surface area.
  • the positive electrode active material layer has a groove portion that exposes the rough surface region.
  • the groove portion is provided in the positive electrode active material layer, and the rough surface region of the first surface of the current collector is exposed from the groove portion.
  • the electrolytic solution is more likely to stay than in the non-roughened smooth surface. Therefore, the rough surface area exposed from the groove can retain the electrolytic solution.
  • the electrolytic solution retained in the rough surface region is stored in the positive electrode active material layer. It can be supplied, and the situation in which the electrolyte solution is insufficient in the positive electrode active material layer is unlikely to occur. Therefore, according to the above power storage device, high battery characteristics can be realized.
  • the groove may have two openings in the side end surface of the positive electrode active material layer, or the two openings may communicate with each other.
  • the electrolytic solution when the electrolytic solution is injected into the case, the electrolytic solution quickly flows through the groove portion provided in the positive electrode active material layer, so that the liquid can be efficiently injected.
  • the rough surface area may be wider than the positive electrode active material layer, and the positive electrode active material layer may be provided in the rough surface area.
  • a part of the separator adjacent to the positive electrode active material layer in the stacking direction of the stacked body may enter the groove. Since the electrolytic solution is retained in the separator in the groove portion of the positive electrode active material layer, the electrolytic solution contained in the separator in the groove portion can be supplied into the positive electrode active material layer. It becomes even more difficult for the situation where the shortage occurs.
  • the groove may extend along one of the in-plane directions of the current collector.
  • the positive electrode active material layer may have at least a pair of strip-shaped portions sandwiching the groove portion in the width direction intersecting the extending direction of the groove portion.
  • the length of the groove portion in the width direction may be 0.04 times or more and 0.80 times or less the length of the strip portion in the width direction.
  • the bipolar electrodes are stacked via the separator, oxygen moving from the positive electrode active material layer to the negative electrode active material layer moves so as to wrap around the edge of the separator via the groove.
  • the length of the groove in the width direction is 0.04 times or more the length of the strip in the width direction, oxygen generated in the positive electrode active material layer of the bipolar electrode can be smoothly guided by the groove.
  • the length of the groove portion in the width direction is 0.80 times or less the length of the strip portion in the width direction, it is easy to secure a desired battery capacity.
  • the length of the strip-shaped portion in the width direction may be 25 mm or more and 50 mm or less.
  • the length of the strip portion in the width direction is 25 mm or more, it is easy to secure a desired battery capacity.
  • the length of the strip-shaped portion in the width direction is 50 mm or less, oxygen generated in the positive electrode active material layer of the bipolar electrode easily reaches the groove.
  • the rough surface area may be a plating layer having a plurality of protrusions.
  • the protrusion may have a structure in which a plurality of deposited metals are stacked on each other in the stacking direction of the stacked body.
  • the battery characteristics can be improved.
  • FIG. 1 is a cross-sectional view showing a power storage device according to an embodiment.
  • FIG. 2A is an enlarged view of a main part of the collector of the bipolar electrode shown in FIG.
  • FIG. 2B is a further enlarged view of the current collector shown in FIG.
  • FIG. 3 is an enlarged view of essential parts of the current collector, the positive electrode active material layer, and the separator shown in FIG.
  • FIG. 4 is a plan view showing the positive electrode active material layer provided on the first surface of the current collector.
  • FIG. 5 is a cross-sectional view taken along the line VV of FIG.
  • FIG. 6 is a graph showing the relationship between the number of cycles and the capacity change rate.
  • FIG. 1 is a cross-sectional view schematically showing a power storage device according to an embodiment.
  • Power storage device 1 is, for example, a nickel-hydrogen secondary battery, a secondary battery such as a lithium-ion secondary battery, or an electric double layer capacitor.
  • Power storage device 1 can be used, for example, as a battery in various vehicles such as forklifts, hybrid vehicles, and electric vehicles.
  • a case where the power storage device 1 is a nickel-hydrogen secondary battery will be described.
  • the power storage device 1 is a bipolar battery including a stack 2 of bipolar electrodes 3.
  • the power storage device 1 includes a stacked body 2 of the bipolar electrodes 3, a case 5 that holds the stacked body 2, and a restraining body 6 that restrains the stacked body 2.
  • the laminated body 2 is configured by laminating a plurality of bipolar electrodes 3 via the separator 7 along the first direction D1.
  • the first direction D1 is a direction along the Z-axis direction here, and is also referred to as a vertical direction or a stacking direction below.
  • a bipolar electrode 3 separated from a terminal member a negative electrode terminal member 25A, a positive electrode terminal member 25B
  • another bipolar electrode 3 is interposed above and below the bipolar electrode 3 with a separator 7 interposed therebetween.
  • a bipolar electrode 3 separated from a terminal member a negative electrode terminal member 25A, a positive electrode terminal member 25B
  • Each of the bipolar electrodes 3 includes a current collector 11, a positive electrode active material layer 12 provided on the first surface 11 a of the current collector 11, and a negative electrode active material layer provided on the second surface 11 b of the current collector 11. 13 and 13.
  • the second surface 11b is a surface opposite to the first surface 11a in the thickness direction of the current collector 11.
  • Each of the positive electrode active material layer 12 and the negative electrode active material layer 13 is provided in the central portion of the current collector 11. That is, the positive electrode active material layer 12 and the negative electrode active material layer 13 are not provided on the peripheral portion 11c of the current collector 11.
  • the peripheral portion 11c is an uncoated portion where the surface of the current collector 11 is exposed.
  • the positive electrode active material layer 12 of the one bipolar electrode 3 faces the negative electrode active material layer 13 of the one bipolar electrode 3 adjacent in the first direction D1 via the separator 7, and
  • the negative electrode active material layer 13 faces the positive electrode active material layer 12 of the other adjacent bipolar electrode in the first direction D1 via the separator 7.
  • Examples of the positive electrode active material forming the positive electrode active material layer 12 include nickel hydroxide.
  • Examples of the negative electrode active material forming the negative electrode active material layer 13 include a hydrogen storage alloy.
  • the area where the negative electrode active material layer 13 is formed on the second surface 11b of the current collector 11 may be slightly larger than the area where the positive electrode active material layer 12 is formed on the first surface 11a of the current collector 11.
  • the peripheral portion 11c of the current collector 11 is an uncoated region where the positive electrode active material and the negative electrode active material are not coated.
  • the case 5 holds the peripheral portion 11c in a state where the peripheral portion 11c is buried in the inner wall 5a of the case 5.
  • a resin spacer 4 is interposed between the first surface 11a of the peripheral edge portion 11c and the inner wall 5a along the peripheral edge portion 11c while being in contact with them.
  • the resin spacer 4 holds the space between two adjacent bipolar electrodes 3. Thereby, between the two current collectors 11 adjacent to each other in the first direction D1, the two current collectors 11 and the inner wall 5a of the case 5 cooperate to form a space.
  • An electrolytic solution made of an alkaline solution such as an aqueous solution of potassium hydroxide is sealed in the space.
  • Two spaces adjacent to each other in the first direction D1 (an enclosed space of an electrolyte formed between two adjacent bipolar electrodes 3) are liquid-tightly separated (sealed) by a resin spacer 4.
  • the resin spacer 4 is formed, for example, by curing the resin arranged on the peripheral portion 11c.
  • the resin before curing may be liquid, sheet, or gel.
  • a current collector 11A having only the negative electrode active material layer 13 provided on one surface is laminated at one lamination end of the laminate 2 (positive direction in the Z-axis direction).
  • the current collector 11A is arranged so that the negative electrode active material layer 13 and the positive electrode active material layer 12 of the uppermost bipolar electrode 3 face each other with the separator 7 interposed therebetween.
  • a current collector 11B provided with only the positive electrode active material layer 12 is stacked.
  • the current collector 11B is arranged such that the positive electrode active material layer 12 and the negative electrode active material layer 13 of the lowermost bipolar electrode 3 face each other with the separator 7 interposed therebetween.
  • the edge portions of the current collectors 11A and 11B are held in the case 5 while being buried in the inner wall 5a of the case 5.
  • the resin spacer 4 is interposed between the edge region of the first surface 11a of the current collectors 11A and 11B and the inner wall 5a.
  • the current collectors 11A and 11B may be formed thicker than the current collector 11 of the bipolar electrode 3.
  • the separator 7 is, for example, a sheet-shaped insulator.
  • the material for forming the separator include a porous film made of a polyolefin resin such as polyethylene (PE) and polypropylene (PP), and a woven or non-woven fabric made of polypropylene or the like.
  • the separator 7 may be reinforced with a vinylidene fluoride resin compound or the like.
  • the separator 7 is not limited to the sheet shape, and may be a bag-shaped insulator.
  • the case 5 is formed in a rectangular tubular shape by injection molding using an insulating resin, for example.
  • the resin material forming the resinous case 5 include polypropylene (PP), polyphenylene sulfide (PPS), modified polyphenylene ether (modified PPE), modified polyphenylene sulfide (modified PPS), and the like.
  • the case 5 is a member that surrounds and holds the side surface 2 a of the stacked body 2 formed by stacking the bipolar electrodes 3.
  • a plurality of liquid injection ports 51 are provided on one side surface 5b (see FIG. 5) of the case 5.
  • the liquid injection port 51 is used to inject the electrolytic solution into the case 5 (specifically, the enclosed space of the electrolytic solution).
  • the current collector 11 has an outer shape of a substantially rectangular flat plate, and the one side surface 5b is, for example, a surface along the short side of the current collector 11.
  • the liquid injection port 51 penetrates the case 5 and the resin spacer 4 along the long side of the current collector 11.
  • the plurality of liquid injection ports 51 are formed respectively corresponding to the enclosed spaces of the plurality of electrolytic solutions.
  • the positions at which the plurality of liquid injection ports 51 are provided are distributed at a plurality of positions (as one example, half the number of stacked layers, here 5 positions) in the direction along the short side of the current collector 11.
  • a plurality (two as an example) of the injection ports 51 are overlapped at every layer number (here, every five layers) according to the dispersion number.
  • the liquid injection port 51 is closed by, for example, sealing with resin.
  • the restraint body 6 is composed of a pair of restraint plates 21 and 21 and a connecting member (a bolt 22 and a nut 23) that connects the restraint plates 21 and 21 to each other.
  • the restraint plate 21 is formed in a flat plate shape with a metal such as iron.
  • An edge portion of the restraint plate 21 protruding outward from the case 5 is provided with an insertion hole 21a through which the bolt 22 is inserted.
  • the inner peripheral surface of the insertion hole 21a and the bolt seating surface of the restraint body 6 are insulated.
  • a terminal member (negative electrode terminal member 25A, positive electrode terminal member 25B) is coupled to one surface of the restraint plate 21 via an insulating member 24.
  • a material for forming the insulating member 24 for example, a fluorine resin or a polyethylene resin can be used.
  • the one restraint plate 21 is located above the case 5 in the first direction D1.
  • One of the restraint plates 21 is butted against one end surface of the case 5 so that the negative electrode terminal member 25A and the current collector 11A are in contact with each other inside the case 5.
  • the other restraint plate 21 is located below the case 5 in the first direction D1.
  • the other restraint plate 21 is abutted against the other end surface of the case 5 so that the positive electrode terminal member 25B and the current collector 11B contact each other inside the case 5.
  • the bolt 22 is passed through the insertion hole 21 a from, for example, one restraint plate 21 toward the other restraint plate 21, and a nut 23 is screwed onto the tip of the bolt 22 protruding from the other restraint plate 21.
  • the laminate 2, the current collectors 11A and 11B, and the case 5 are sandwiched and unitized, and a restraining load along the first direction D1 is applied to the laminate 2.
  • the negative electrode terminal member 25A is arranged between the one constraining plate 21 and the laminated body 2
  • the positive electrode terminal member 25B is arranged between the other constraining plate 21 and the laminated body 2.
  • the lead-out portion 26 is connected to the negative electrode terminal member 25A.
  • the lead-out portion 27 is connected to the positive electrode terminal member 25B.
  • the drawer 26 and the drawer 27 allow the power storage device 1 to be charged and discharged.
  • the current collector 11 will be described below with reference to FIGS. 2 (a) and 2 (b).
  • the current collector 11 has a steel plate 10 and a nickel plating layer 30 that covers one surface 10 a of the steel plate 10.
  • the first surface 11 a is the surface of the plating layer 30, and the second surface 11 b is the surface of the steel plate 10.
  • the first surface 11a has a surface roughness (arithmetic mean roughness Ra) larger than the surface 10a which is the natural surface of the steel plate 10 and the second surface 11b.
  • known surface treatments such as chemical treatments such as etching treatment and plating treatment, physical treatments such as sputtering, and mechanical treatments such as polishing treatment can be applied.
  • the plating layer 30 having the first surface 11a roughened by electrolytic nickel plating is formed.
  • the second surface 11b is a natural surface of the steel sheet 10, that is, a non-roughened surface that has not been subjected to the above-described roughening treatment.
  • the second surface 11b is, for example, a smooth surface.
  • Examples of the steel sheet 10 include cold rolled steel sheets (SPCC etc.) defined in JIS G 3141: 2005.
  • the thickness of the steel sheet 10 is, for example, 0.1 ⁇ m or more and 1000 ⁇ m or less, and is 50 ⁇ m as an example.
  • the plating layer 30 is formed by performing electrolytic nickel plating treatment.
  • the thickness of the plating layer 30 can be designed to be, for example, 5 ⁇ m or more and 20 ⁇ m or less.
  • the plating layer 30 includes a base nickel plating layer 31 provided on the surface 10 a of the steel sheet 10 and a main nickel plating layer provided on the base nickel plating layer 31. And a layer 32.
  • the base nickel plating layer 31 and the main nickel plating layer 32 are formed by performing electrolytic plating treatment under different conditions.
  • the base nickel plating layer 31 is an electrolytic plating layer provided on the surface 10a of the steel sheet 10 along the second direction D2 that intersects the first direction D1.
  • the second direction D2 corresponds to the direction along the XY plane or the extending direction of the one surface 10a. Therefore, the second direction D2 does not necessarily have to be orthogonal to the first direction D1.
  • the thickness of the underlying nickel plating layer 31 may be, for example, 0.5 ⁇ m or more and 5 ⁇ m or less, or may be 0.5 ⁇ m or more and 2 ⁇ m or less.
  • the base nickel plating layer 31 may cover the entire surface 10 a of the steel plate 10.
  • the surface shape of the base nickel plating layer 31 is different from the shape of the surface 10a. Specifically, the base nickel plating layer 31 has a plurality of protrusions 33 protruding along the first direction D1. Therefore, the surface shape of the base nickel plating layer 31 does not follow the surface 10a of the steel plate 10, and the surface roughness of the base nickel plating layer 31 is larger than the surface roughness of the surface 10a of the steel plate 10. Therefore, the base nickel plating layer 31 is provided differently from the smooth plating layer.
  • the smooth plating layer is a plating layer having a surface shape along the surface of the object to be plated.
  • the plurality of convex portions 33 are irregularly provided along the second direction D2.
  • the average height of the protrusions 33 may be, for example, 0.4 ⁇ m or more, and may be less than half the thickness of the underlying nickel plating layer 31. In this case, the shape of the nickel plating layer 32 can be improved.
  • the average height of the convex portion 33 is measured by, for example, a microscope using a laser confocal optical system.
  • the nickel plating layer 32 is an electrolytic plating layer provided with the underlying nickel plating layer 31 as a film formation surface, and has a surface roughness larger than that of the underlying nickel plating layer 31.
  • the surface roughness of the underlying nickel plating layer 31 and the main nickel plating layer 32 is represented by the arithmetic mean roughness Ra defined in JIS B 0601: 2013 (or ISO 4287: 1997, Amd.1: 2009). ..
  • the surface roughness of the present nickel plating layer 32 is, for example, 1.5 ⁇ m or more and 6.0 ⁇ m or less, which is 1.5 times or more and 60.0 times or less the surface roughness of the underlying nickel plating layer 31.
  • the surface area of the nickel plating layer 32 can be increased while suppressing the occurrence of pinholes or the like in the plating layer 30.
  • the thickness of the nickel plating layer 32 is, for example, 5 ⁇ m or more and 20 ⁇ m or less.
  • the present nickel plating layer 32 does not necessarily have to be formed so as to cover the entire surface of the base nickel plating layer 31.
  • the present nickel plating layer 32 may be an assembly of a plurality of protrusions 34 protruding from the base nickel plating layer 31 in the first direction D1.
  • the nickel plating layer 32 is also called a roughening plating layer.
  • Each of the plurality of protrusions 34 is formed so as to reach the tip 34b along the first direction D1 with the portion in contact with the corresponding protrusion 33 as the base end 34a.
  • a plurality of nickel crystals having, for example, a substantially spherical shape are superposed on at least a part of the plurality of protrusions 34.
  • These nickel crystals are a plurality of deposited metals (additives) formed by electrolytic plating. Such a plurality of deposited metals are overlapped with each other (stacked), so that the length (length dimension) of the protrusion 34 in the second direction D2 is larger than the length of the base end 34a in the second direction D2.
  • 34c is formed. That is, at least a part of the protrusions 34 has a tapered shape that is tapered from the base end 34a toward the distal end 34b.
  • the position of the enlarged portion 34c in the protrusion 34 does not necessarily have to be the tip end 34b, but is at least closer to the tip end 34b than the base end 34a.
  • the portion having the largest length in the second direction D2 in the protrusion 34 having the tapered shape does not have to be the tip end 34b, but is located at a position other than the base end 34a.
  • the position of the enlarged portion 34c in the protrusion 34 may be different for each protrusion 34 depending on the overlapping mode of the deposited metal.
  • the average height of the protrusions 34 is, for example, 30 ⁇ m or less. When the average height of the protrusions 34 is 30 ⁇ m or less, breakage of the protrusions 34 can be effectively suppressed.
  • the average height of the protrusions 34 is measured using, for example, a microscope using a laser confocal optical system.
  • the number of the protrusions 34 per unit area of the present nickel plating layer 32 is, for example, 2,500 or more and 7,000 or less in a plan view (that is, when viewed along the first direction D1). When the number of the protrusions 34 is 2,500 or more, the surface area of the nickel plating layer 32 can be sufficiently secured. When the number of the protrusions 34 is 7,000 or less, it is possible to suppress contact between two adjacent protrusions 34. In this embodiment, the unit area is 1 mm 2 .
  • the number of the protrusions 34 per unit area of the nickel plating layer 32 is calculated by the average length RSm of the roughness curve element defined in JIS B 0601: 2013 (or ISO 4287: 1997, Amd. 1: 2009), for example. To be done.
  • the current collectors 11A and 11B may be steel plates that have been electrolytically plated, or may be metal foil such as nickel foil.
  • the above-mentioned plating layer 30 can be formed by the following procedure, for example.
  • a base nickel plating layer 31 having a surface shape different from the surface shape of the steel plate 10 is formed on the surface 10a of the steel plate 10 constituting the current collector 11.
  • the base nickel plating layer 31 is formed by subjecting the steel plate 10 to electrolytic plating.
  • a nickel bath having a nickel concentration of 0.5 mol / L or more and 2.0 mol / L or less and a temperature of 40 ° C. or more and 65 ° C. or less is used.
  • the nickel bath is an electrolytic solution in which nickel cations are present, and examples thereof include nickel chloride solution and nickel sulfate solution.
  • the plating layer can be efficiently formed. Further, when the temperature of the nickel bath is 40 ° C. or higher and 65 ° C. or lower, the average height of the protrusions 33 provided on the base nickel plating layer 31 can be controlled well.
  • the steel plate 10 When performing the electrolytic plating treatment for forming the underlying nickel plating layer 31, for example, under a condition where the current density is 0.5 A / dm 2 or more and 5.0 A / dm 2 or less, 150 seconds or more and 2,400 seconds or less. Meanwhile, the steel plate 10 is immersed in a nickel bath. By setting the current density during the electrolytic plating process to 0.5 A / dm 2 or more and 5.0 A / dm 2 or less, it is possible to prevent the underlying nickel plating layer 31 from becoming a smooth plating layer. In addition, it is possible to prevent the convex portion 33 formed on the base nickel plating layer 31 from having a needle shape (or whisker shape). By immersing the steel sheet 10 in the nickel bath for 150 seconds or more and 2,400 seconds or less, the thickness of the base nickel plating layer 31 can be favorably set.
  • the conditions that are particularly important when forming the underlying nickel plating layer 31 are the temperature and current density of the nickel bath. Therefore, when both the temperature of the nickel bath and the current density are within the above ranges, the nickel concentration of the nickel bath and the time for which the steel sheet 10 is immersed need not necessarily be within the above ranges.
  • the present nickel plating layer 32 includes a plurality of protrusions 34 and has a surface roughness larger than that of the base nickel plating layer 31.
  • the current collector 11 including the steel plate 10 and the plated layer 30 having the base nickel plated layer 31 and the main nickel plated layer 32 is obtained.
  • the present nickel plating layer 32 is formed by subjecting the steel plate 10 on which the base nickel plating layer 31 is formed to electrolytic plating. In this electrolytic plating treatment, for example, a Watt bath having a nickel concentration of 0.15 mol / L or more and less than 0.30 mol / L and a temperature of 30 ° C. or more and 60 ° C.
  • the Watt's bath is an electrolytic solution containing nickel sulfate, nickel chloride, and boric acid as main components.
  • nickel concentration in the Watt bath is 0.15 mol / L or more and less than 0.30 mol / L, the protrusions 34 having a tapered shape can be favorably formed.
  • temperature of the Watt bath is 30 ° C. or higher and 60 ° C. or lower, the average height of the tapered shape can be well controlled.
  • the steel plate 10 Carrying out the electroplating process for forming the nickel plating layer 32, for example a current density of 30A / dm 2 or more 50A / dm 2 or less between at 60 seconds or less 30 seconds or more conditions, the steel plate 10 watts Immerse in bath.
  • the current density in the electrolytic plating process to 30A / dm 2 or more 50A / dm 2 or less, it can be favorably formed a projection 34 having a thickens shape.
  • the thickness of the present nickel plating layer 32 can be favorably set.
  • the conditions that are particularly important when forming the nickel plating layer 32 are the nickel concentration and the current density of the watt bath. Therefore, when both the nickel concentration of the Watt bath and the current density are within the above ranges, the temperature of the Watt bath and the time for which the steel sheet 10 is immersed need not necessarily be within the above range.
  • the positive electrode active material layer 12 has a substantially rectangular flat plate shape.
  • the current collector 11 has a substantially rectangular flat plate shape, and the short side and the long side of the positive electrode active material layer 12 are parallel to the short side and the long side of the current collector 11, respectively. It is provided in.
  • the positive electrode active material layer 12 is provided with a plurality of (four in the present embodiment) groove portions 15 extending in a direction parallel to the long sides of the current collector 11.
  • Each of the plurality of groove portions 15 continuously extends along one direction (in the present embodiment, a direction parallel to the long side of the current collector 11).
  • Each of the plurality of groove portions 15 has a uniform width in the extending direction.
  • the plurality of groove portions 15 have substantially the same groove width (a length L1 described later), and are arranged in parallel with each other at a substantially uniform distance. Further, all of the plurality of groove portions 15 penetrate the positive electrode active material layer 12. That is, the groove 15 has a plurality of openings (four in this embodiment) on the side end surfaces of the two short sides of the positive electrode active material layer 12. Therefore, the positive electrode active material layer 12 is divided into a plurality (five in this embodiment) of band-shaped portions 12a by a plurality (four in this embodiment) of the groove portions 15.
  • the length L2 in the width direction of the positive electrode active material layer 12 may be 100 mm or more and 330 mm or less.
  • the length L1 of the groove portion 15 in the width direction may be 0.04 times or more and 0.80 times or less than the length L3 of the strip portion 12a in the width direction.
  • the length L1 may be 0.08 times or more and 0.40 times or less than the length L3.
  • the length L3 may be 25 mm or more and 50 mm or less.
  • the length L1 is smaller than the length L4 of the liquid injection port 51 in the width direction.
  • the length L4 may be 1 mm or more and 20 mm or less.
  • the groove 15 can be formed when the positive electrode active material layer 12 is applied, for example. Specifically, when a positive electrode paste containing a positive electrode active material, a conductive additive, and a solvent is applied on the current collector 11 using a die coater, an obstacle such as a shim should be provided at the paste discharge port of the die coater. Thus, the groove portion 15 can be formed.
  • the first surface 11a of the current collector 11 provided with the positive electrode active material layer 12 is a rough surface area provided with the plurality of protrusions 34.
  • the rough surface area is an area wider than the positive electrode active material layer 12.
  • the entire first surface 11a is a rough surface area.
  • the positive electrode active material layer is provided in the rough surface area. Therefore, as shown in FIG. 3, the rough surface region of the first surface 11a is exposed from the groove 15 provided in the positive electrode active material layer 12. That is, the groove bottom of the groove portion 15 is a rough surface region of the first surface 11 a of the current collector 11.
  • the electrolytic solution is more likely to stay than in the non-roughened smooth surface. For example, the electrolytic solution penetrates into the gap between the protrusions 34 and soaks into the rough surface area. Therefore, the electrolytic solution can be retained to some extent in the rough surface region exposed from the groove portion 15.
  • the positive electrode active material expands and the electrolytic solution flows into the positive electrode active material layer 12, and when the power storage device 1 is discharged, the positive electrode active material contracts and the positive electrode active material layer 12 is electrolyzed. Liquid flows out.
  • the electrolytic solution flows out from the positive electrode active material layer 12 during discharge, the electrolytic solution is retained in the rough surface region that is the groove bottom of the groove portion 15 of the positive electrode active material layer 12. Therefore, the electrolytic solution retained in the rough surface region during charging can be supplied to the positive electrode active material layer 12.
  • the liquid can be supplied to the positive electrode active material layer 12 more quickly.
  • the electrolyte solution is insufficient, a high resistance portion is generated between the current collector 11 and the positive electrode active material layer 12, and the battery characteristics deteriorate. According to the power storage device 1, a situation in which the electrolyte solution is insufficient at the time of charging is effectively suppressed, and thus high battery characteristics are realized.
  • the rough surface area of the first surface 11 a of the current collector 11 is composed of a plurality of protrusions 34 having a tapered shape. Therefore, since the electrolytic solution can be retained in the space between the two adjacent protrusions 34, a larger amount of electrolytic solution can be retained.
  • the groove portion 15 Since the groove portion 15 has two openings on the side end surface of the positive electrode active material layer 12 and communicates the two openings, when the electrolytic solution is injected into the case 5, the electrolytic solution is filled with the positive electrode active material layer 12. It flows quickly through the groove portion 15 provided in the.
  • the electrolytic solution was provided in the positive electrode active material layer 12 by designing the extending direction of the groove portion 15 so as to be along the injection direction of the electrolytic solution into the case 5 (the penetrating direction of the injection port 51). It spreads through the groove 15 more quickly into the case. Therefore, the electrolytic solution can be efficiently injected into the case 5.
  • the entire first surface 11a of the current collector 11 is a rough surface area, so that the rough surface area is also exposed on the outer periphery of the positive electrode active material layer 12. Therefore, also on the outer periphery of the positive electrode active material layer 12, the electrolytic solution is retained in the rough surface region, similarly to the groove bottom of the groove portion 15. That is, since the electrolytic solution is retained in the groove bottoms of the groove portions 15 of the positive electrode active material layer 12 and the rough surface region of the outer periphery of the positive electrode active material layer 12, a larger amount of electrolytic solution can be retained. As a result, the situation in which the electrolyte solution is insufficient during charging is more effectively suppressed.
  • the rough surface area is wider than the positive electrode active material layer 12, and the positive electrode active material layer 12 is provided in the rough surface area. Therefore, when the positive electrode paste containing the positive electrode active material, the conductive auxiliary agent, and the solvent is applied and the applied positive electrode paste is dried to form the positive electrode active material layer 12, at least one of the plurality of protrusions 34 in the rough surface region is formed. The part enters the positive electrode active material layer 12. Therefore, the anchor effect of the protrusions 34 improves the adhesion of the positive electrode active material layer 12 to the current collector 11.
  • the positive electrode active material layer 12 is provided with a part 7 a of the separator 7 that is adjacent to the positive electrode active material layer 12 in the stacking direction of the stacked body 2 (first direction D ⁇ b> 1). It has entered the groove 15.
  • a part 7 a of the separator 7 enters the groove 15.
  • the separator 7 is in the form of a porous film, a woven fabric, a non-woven fabric or the like, it can absorb and retain the electrolytic solution.
  • the electrolytic solution flows out from the positive electrode active material layer 12 during discharging, the electrolytic solution is retained in the separator 7 in addition to the rough surface region of the first surface 11a of the current collector 11.
  • the electrolytic solution is applied to the positive electrode active material layer 12 from the rough surface region of the first surface 11 a that is the groove bottom of the groove portion 15 and the part 7 a of the separator 7 that has entered the groove portion 15 of the positive electrode active material layer 12. Can be supplied, and the situation in which the electrolyte solution is insufficient during charging is more effectively suppressed.
  • positive electrode active material layer 12 has groove portion 15
  • oxygen moving from positive electrode active material layer 12 to negative electrode active material layer 13 can be guided to the edge portion of separator 7 by groove portion 15. ..
  • the groove portion 15 is not formed in the positive electrode active material layer 12, it is possible to suppress the electrolytic solution in the positive electrode active material layer 12 from being pushed out by the generated oxygen toward the outside of the positive electrode active material layer 12. It becomes possible to do.
  • the groove portions 15 extend along one of the in-plane directions of the current collector 11, and each groove portion 15 is formed by the pair of strip-shaped portions 12 a of the positive electrode active material layer 12 in the extending direction of the groove portions 15. It is sandwiched in the width direction that intersects.
  • the length L1 of the groove portion 15 may be 0.04 times or more and 0.80 times or less than the length L3 of the strip portion 12a.
  • the length L3 may be 25 mm or more and 50 mm or less. By setting the length L3 to 25 mm or more, it is easy to secure a desired battery capacity. By setting the length L3 to 50 mm or less, oxygen generated in the positive electrode active material layer 12 of the bipolar electrode 3 easily reaches the groove portion 15.
  • Example 1 The configuration of the power storage device according to the first embodiment is the same as that of the power storage device 1 according to the above-described embodiment.
  • the length L1 of the groove portion 15 was 3 mm
  • the number of the strip-shaped portions 12a was 5
  • the length L3 of the strip-shaped portion 12a was 33 mm.
  • Comparative Example 1 The power storage device according to Comparative Example 1 is different from the power storage device according to the first embodiment in that the first surface 11a is not roughened, and is otherwise similar to the power storage device according to the first embodiment. Is configured.
  • FIG. 6 is a graph showing the relationship between the number of cycles and the capacity change rate.
  • the horizontal axis represents the number of cycles and the vertical axis represents the capacity change rate.
  • One cycle is from when the SOC (state of charge) of the power storage device reaches 80% until it reaches 0% (completely discharged state), and then the battery is recharged until the SOC reaches 80%. ..
  • the capacity change rate is the ratio of the battery capacity in each cycle when the battery capacity of the power storage device in the first cycle is 1.
  • the battery capacity of the power storage device was measured by a charging / discharging device (eg: manufactured by Toyo System Co., Ltd.).
  • Battery characteristics evaluation result 1 As shown in FIG. 6, in Example 1, it was found that the battery capacity hardly changed even when the number of cycles exceeded 800. In Comparative Example 1, it was found that the battery capacity decreased as the number of cycles exceeded 670. It is considered that the deterioration of the rate of change in battery capacity in Comparative Example 1 is due to liquid depletion due to the inability to supply the electrolytic solution to the positive electrode active material. From FIG. 6, it was found that the battery capacity of Example 1 was more suppressed than that of Comparative Example 1.
  • Example 2 to 11 The configurations of the power storage devices according to Examples 2 to 11 and Reference Example 1 are the same as those of the power storage device 1 according to the above-described embodiment.
  • the length L2 of the positive electrode active material layer 12 was 100 mm
  • the number of the strip portions 12a was 2
  • the number of the groove portions 15 was 1
  • the length L3 of the strip portion 12a and the length of the groove portions 15 were set. L1 was changed.
  • the power storage device according to the first reference example is different from the power storage devices according to the second to eleventh embodiments in that the number of the strip portions 12a is one and the groove portion 15 is not provided, and in other respects, the second to eleventh embodiments are described. It is configured similarly to the power storage device according to.
  • Battery characteristics evaluation method 2 The battery capacities of the power storage devices of Examples 2 to 11 and Reference Example 1 were measured. Table 1 shows the measurement results. Each capacity (battery capacity) in Table 1 shows the ratio of the battery capacity in each example when the battery capacity of the power storage device of Reference Example 1 is 100.
  • Example 4 As shown in Table 1, in Example 4, it was found that a battery capacity of 70% or more was secured. Therefore, it was found that the power storage device had a battery capacity of 70% or more when the length L1 of the groove 15 was 0.80 times or less the length L3 of the strip portion 12a. In Example 6, it was found that a battery capacity of 80% or more was secured. Therefore, it was found that the power storage device had a battery capacity of 80% or more when the length L1 of the groove 15 was 0.40 times or less the length L3 of the strip portion 12a.
  • the length L1 of the groove portion 15 is 0.80 times or less of the length L3 of the strip portion 12a, a more sufficient battery capacity can be secured, and by setting it to 0.40 times or less, a further sufficient battery capacity can be obtained. It turns out that the capacity can be secured.
  • the internal pressures before and after charging were measured for the power storage devices of Examples 2 to 11 and Reference Example 1.
  • the internal pressure of the power storage device before charging and the internal pressure of the power storage device after charging were measured by a pressure transmitter (KM18 manufactured by Nagano Keiki Co., Ltd.).
  • the internal pressure of the power storage device charged at 0.5C until the SOC changed from 0% to 100% and rested for 1 hour was defined as the internal pressure of the power storage device after charging.
  • Table 2 shows the evaluation results of the internal pressure of the power storage devices of Examples 2 to 11 and Reference Example 1 together with the evaluation result 2.
  • the "internal pressure" in Table 2 is the internal pressure after charging when the internal pressure before charging is 0 (that is, the increase value of the internal pressure before and after charging).
  • the length L1 of the groove 15 is 0.04 times or more and 0.80 times or less the length L3 of the strip-shaped portion 12a, it is possible to secure a more sufficient battery capacity and increase the internal pressure of the power storage device after charging. It has been found that it is possible to sufficiently suppress, and by setting it to be 0.08 times or more and 0.40 times or less, it is possible to further secure a sufficient battery capacity and it is possible to further sufficiently suppress an increase in internal pressure of the power storage device after charging.
  • the power storage device according to the present disclosure is not limited to the above embodiment, and various modifications can be made.
  • the entire first surface of the current collector may be roughened, or a part of the first surface may be roughened. Only the first surface of the current collector may be roughened, or both the first surface and the second surface may be roughened.
  • a groove similar to that of the positive electrode active material layer may be provided in the negative electrode active material layer provided on the second surface of the current collector.
  • the groove part of the negative electrode active material layer and the groove part of the positive electrode active material layer may be provided in regions corresponding to each other or may be provided in different regions.
  • the groove extends in the direction parallel to the long side of the current collector, but the direction in which the groove extends is not limited to this.
  • the groove may be formed so as to extend in a direction parallel to the short side of the current collector. That is, the groove may be formed so as to extend in the in-plane direction of the current collector (that is, the direction along the first surface of the current collector, here, the direction parallel to the XY plane).
  • the groove portion linearly penetrates the positive electrode active material layer in a direction parallel to the long side of the current collector, but the groove portion has two openings on the side end surface of the positive electrode active material layer,
  • the shape is not limited to a straight line.
  • the groove section has these two openings.
  • the shape may be curved and bent so as to connect to each other.
  • the groove portion continuously extends along one direction, but the configuration of the groove portion is not limited to this.
  • the groove may extend intermittently along one direction.
  • the number of grooves and the number of strips of the positive electrode active material layer can be changed as appropriate.
  • the positive electrode active material layer may be provided with only one groove.
  • the positive electrode active material layer may include a pair of strip-shaped portions sandwiching the groove portion in the width direction intersecting the extending direction of the groove portion.
  • the first surface of the current collector has a roughened surface area that is roughened as a whole, and the positive electrode active material layer is entirely provided on the roughened surface area.
  • the area provided is not limited to this.
  • the current collector may have a rough surface area on a part of the first surface, and the positive electrode active material layer may be formed on the surface of the rough surface area and the surface of the non-roughened area. In this case, the groove may expose a region that is not roughened.
  • the number of stacked bipolar electrodes and the number of injection ports can be changed appropriately.
  • the number of stacked bipolar electrodes and the number of injection ports may be 24 each.
  • the positions where the liquid injection ports are provided are distributed in 12 positions in the direction along the short side of the current collector, and two liquid injection ports may be overlapped every 12 layers at each position.
  • the positions where the liquid injection ports are provided may be dispersed in places (for example, 24 places in the case of 24 layers) corresponding to the number of stacked layers in the direction along the short side of the current collector.
  • the positions of all the liquid injection ports may be different from each other in the direction along the short side of the current collector.
  • SYMBOLS 1 Electric storage device, 3 ... Bipolar electrode, 11 ... Current collector, 11a ... 1st surface, 11b ... 2nd surface, 12 ... Positive electrode active material layer, 12a ... Strip part, 13 ... Negative electrode active material layer, 15 ... Groove part , 30 ... Plating layer, 34 ... Protrusion, L1, L3 ... Length.

Abstract

This power storage device includes: a laminate in which a plurality of bipolar electrodes each including a collector, a positive electrode active material layer provided on a first surface of the collector, and a negative active material layer provided on a second surface of the collector are laminated through separators; a case which encloses the side surfaces of the laminate; and electrolyte encapsulated in the case, wherein at least a part of the first surface of the laminate has a roughened surface region that is surface-roughened, at least a part of the positive electrode active material layer is provided on the roughened surface region, and the positive electrode active material layer has a groove part that exposes the roughened surface region.

Description

蓄電装置Power storage device
　本開示は、蓄電装置に関する。 The present disclosure relates to a power storage device.
　従来、集電体の一方の面上に正極活物質層が設けられ、他方の面上に負極活物質層が設けられたバイポーラ電極を備えた、いわゆるバイポーラ型の蓄電装置が知られている。このような蓄電装置のケース内には電解液が封入されている。 Conventionally, there is known a so-called bipolar type power storage device including a bipolar electrode in which a positive electrode active material layer is provided on one surface of a current collector and a negative electrode active material layer is provided on the other surface. An electrolytic solution is enclosed in the case of such a power storage device.
特開２０１４－５６７９９号公報JP, 2014-56799, A
　上述した蓄電装置では、充電時および放電時に、ケース内において電解液がある程度流動する。たとえば正極活物質層では、充電時に正極活物質が膨張して電解液が流れ込み、放電時に正極活物質が収縮して電解液が流れ出す。充電時において正極活物質層に流れ込む電解液が不足する場合には電池特性が劣化し得る。 In the above-described power storage device, the electrolytic solution flows to some extent in the case during charging and discharging. For example, in the positive electrode active material layer, the positive electrode active material expands during charging and the electrolytic solution flows in, and during discharging, the positive electrode active material contracts and the electrolytic solution flows out. If the electrolyte solution flowing into the positive electrode active material layer during charging is insufficient, battery characteristics may deteriorate.
　本開示は、電池特性の向上が図られた蓄電装置を説明する。 The present disclosure describes a power storage device with improved battery characteristics.
　本開示の一側面に係る蓄電装置は、集電体と、集電体の第１面に設けられた正極活物質層と、集電体の第２面に設けられた負極活物質層と、をそれぞれ含む複数のバイポーラ電極が、セパレータを介して積層された積層体と、積層体の側面を囲むケースと、ケース内に封入された電解液とを備える。集電体の第１面は、粗面化された粗面領域を第１面の少なくとも一部に有する。正極活物質層の少なくとも一部は粗面領域に設けられている。正極活物質層は、粗面領域を露出させる溝部を有する。 A power storage device according to one aspect of the present disclosure includes a current collector, a positive electrode active material layer provided on a first surface of the current collector, a negative electrode active material layer provided on a second surface of the current collector, A plurality of bipolar electrodes each including the above are provided, a laminated body laminated via a separator, a case surrounding a side surface of the laminated body, and an electrolytic solution enclosed in the case. The first surface of the current collector has a roughened roughened area on at least a part of the first surface. At least a part of the positive electrode active material layer is provided in the rough surface area. The positive electrode active material layer has a groove portion that exposes the rough surface region.
　上記蓄電装置では、正極活物質層に溝部が設けられており、溝部から集電体の第１面の粗面領域が露出している。粗面領域では、粗面化されていない平滑面に比べて、電解液が留まりやすい。そのため、溝部から露出した粗面領域は電解液を保液することができる。このように、正極活物質層が設けられた集電体の第１面において電解液を粗面領域に保液することで、粗面領域に保液された電解液を正極活物質層内に供給することができ、正極活物質層内で電解液が不足する事態が生じにくくなる。そのため、上記蓄電装置によれば、高い電池特性を実現することができる。 In the above power storage device, the groove portion is provided in the positive electrode active material layer, and the rough surface region of the first surface of the current collector is exposed from the groove portion. In the rough surface region, the electrolytic solution is more likely to stay than in the non-roughened smooth surface. Therefore, the rough surface area exposed from the groove can retain the electrolytic solution. In this way, by retaining the electrolytic solution in the rough surface region on the first surface of the current collector provided with the positive electrode active material layer, the electrolytic solution retained in the rough surface region is stored in the positive electrode active material layer. It can be supplied, and the situation in which the electrolyte solution is insufficient in the positive electrode active material layer is unlikely to occur. Therefore, according to the above power storage device, high battery characteristics can be realized.
　他の側面に係る蓄電装置において、溝部は、正極活物質層の側端面に２つの開口を有してもよく、２つの開口を連通していてもよい。この場合、ケース内に電解液を注入したときに、電解液が正極活物質層に設けられた溝部を通って速やかに流れるので、効率良く注液することができる。 In the power storage device according to another aspect, the groove may have two openings in the side end surface of the positive electrode active material layer, or the two openings may communicate with each other. In this case, when the electrolytic solution is injected into the case, the electrolytic solution quickly flows through the groove portion provided in the positive electrode active material layer, so that the liquid can be efficiently injected.
　他の側面に係る蓄電装置において、粗面領域は、正極活物質層よりも広い領域であってもよく、正極活物質層は、粗面領域内に設けられていてもよい。 In the power storage device according to another aspect, the rough surface area may be wider than the positive electrode active material layer, and the positive electrode active material layer may be provided in the rough surface area.
　他の側面に係る蓄電装置においては、積層体の積層方向において正極活物質層と隣り合うセパレータの一部が、溝部に入り込んでいてもよい。正極活物質層の溝部に入り込んだ部分のセパレータに電解液が保液されることで、溝部に入り込んだ部分のセパレータに含まれる電解液を正極活物質層内に供給することができ、電解液が不足する事態がさらに生じにくくなる。 In the power storage device according to another aspect, a part of the separator adjacent to the positive electrode active material layer in the stacking direction of the stacked body may enter the groove. Since the electrolytic solution is retained in the separator in the groove portion of the positive electrode active material layer, the electrolytic solution contained in the separator in the groove portion can be supplied into the positive electrode active material layer. It becomes even more difficult for the situation where the shortage occurs.
　他の側面に係る蓄電装置において、溝部は、集電体の面内方向のうちの一方向に沿って延在していてもよい。正極活物質層は、溝部の延在方向に交差する幅方向に溝部を挟む少なくとも一対の帯状部分を有していてもよい。溝部の幅方向における長さは、帯状部分の幅方向における長さの０．０４倍以上０．８０倍以下であってもよい。たとえば、蓄電装置が電池容量に対して過剰に充電された場合、ケース内において電解液中の水が電気分解されて酸素が発生する。この酸素は、バイポーラ電極の正極活物質層において発生し、積層方向に隣り合う別のバイポーラ電極の負極活物質に吸収される。バイポーラ電極同士はセパレータを介して積層されているので、正極活物質層から負極活物質層に移動する酸素は、溝部を介してセパレータの縁部を回り込むように移動する。溝部の幅方向における長さが帯状部分の幅方向における長さの０．０４倍以上である場合、バイポーラ電極の正極活物質層において発生した酸素を溝部によって円滑に導くことができる。溝部の幅方向における長さが帯状部分の幅方向における長さの０．８０倍以下である場合、所望の電池容量を確保しやすい。 In the power storage device according to another aspect, the groove may extend along one of the in-plane directions of the current collector. The positive electrode active material layer may have at least a pair of strip-shaped portions sandwiching the groove portion in the width direction intersecting the extending direction of the groove portion. The length of the groove portion in the width direction may be 0.04 times or more and 0.80 times or less the length of the strip portion in the width direction. For example, when the power storage device is overcharged with respect to the battery capacity, water in the electrolytic solution is electrolyzed in the case to generate oxygen. This oxygen is generated in the positive electrode active material layer of the bipolar electrode and is absorbed by the negative electrode active material of another bipolar electrode adjacent in the stacking direction. Since the bipolar electrodes are stacked via the separator, oxygen moving from the positive electrode active material layer to the negative electrode active material layer moves so as to wrap around the edge of the separator via the groove. When the length of the groove in the width direction is 0.04 times or more the length of the strip in the width direction, oxygen generated in the positive electrode active material layer of the bipolar electrode can be smoothly guided by the groove. When the length of the groove portion in the width direction is 0.80 times or less the length of the strip portion in the width direction, it is easy to secure a desired battery capacity.
　他の側面に係る蓄電装置において、帯状部分の幅方向における長さは、２５ｍｍ以上５０ｍｍ以下であってもよい。帯状部分の幅方向における長さが２５ｍｍ以上である場合、所望の電池容量を確保しやすい。帯状部分の幅方向における長さが５０ｍｍ以下である場合、バイポーラ電極の正極活物質層において発生した酸素が溝部に到達しやすい。 In the power storage device according to another aspect, the length of the strip-shaped portion in the width direction may be 25 mm or more and 50 mm or less. When the length of the strip portion in the width direction is 25 mm or more, it is easy to secure a desired battery capacity. When the length of the strip-shaped portion in the width direction is 50 mm or less, oxygen generated in the positive electrode active material layer of the bipolar electrode easily reaches the groove.
　他の側面に係る蓄電装置において、粗面領域は、複数の突起を有するメッキ層であってもよい。突起は、複数の析出金属が積層体の積層方向に互いに積み重なった構造であってもよい。 In the power storage device according to another aspect, the rough surface area may be a plating layer having a plurality of protrusions. The protrusion may have a structure in which a plurality of deposited metals are stacked on each other in the stacking direction of the stacked body.
　本開示に係る蓄電装置によれば、電池特性の向上が図られる。 According to the power storage device according to the present disclosure, the battery characteristics can be improved.
図１は、一実施形態に係る蓄電装置を示す断面図である。FIG. 1 is a cross-sectional view showing a power storage device according to an embodiment. 図２（ａ）は、図１に示したバイポーラ電極の集電体の要部拡大図である。図２（ｂ）は、図２（ａ）に示した集電体をさらに拡大した図である。FIG. 2A is an enlarged view of a main part of the collector of the bipolar electrode shown in FIG. FIG. 2B is a further enlarged view of the current collector shown in FIG. 図３は、図１に示した集電体、正極活物質層、および、セパレータの要部拡大図である。FIG. 3 is an enlarged view of essential parts of the current collector, the positive electrode active material layer, and the separator shown in FIG. 図４は、集電体の第１面に設けられた正極活物質層を示した平面図である。FIG. 4 is a plan view showing the positive electrode active material layer provided on the first surface of the current collector. 図５は、図１のＶ－Ｖ線に沿った断面図である。FIG. 5 is a cross-sectional view taken along the line VV of FIG. 図６は、サイクル数と容量変化率との関係を示すグラフである。FIG. 6 is a graph showing the relationship between the number of cycles and the capacity change rate.
　以下、本開示の一実施形態について、図面を参照しつつ詳細に説明する。なお、以下の説明において、同一または相当要素には同一符号を用い、重複する説明を省略する。 Hereinafter, an embodiment of the present disclosure will be described in detail with reference to the drawings. In the following description, the same or corresponding elements will be denoted by the same reference symbols, without redundant description.
　図１は、一実施形態に係る蓄電装置を模式的に示す断面図である。蓄電装置１は、たとえば、ニッケル水素二次電池、およびリチウムイオン二次電池等の二次電池、または、電気二重層キャパシタである。蓄電装置１は、たとえば、フォークリフト、ハイブリッド自動車、および電気自動車等の各種車両のバッテリとして用いることができる。以下、一例として、蓄電装置１がニッケル水素二次電池である場合について説明する。 FIG. 1 is a cross-sectional view schematically showing a power storage device according to an embodiment. Power storage device 1 is, for example, a nickel-hydrogen secondary battery, a secondary battery such as a lithium-ion secondary battery, or an electric double layer capacitor. Power storage device 1 can be used, for example, as a battery in various vehicles such as forklifts, hybrid vehicles, and electric vehicles. Hereinafter, as an example, a case where the power storage device 1 is a nickel-hydrogen secondary battery will be described.
　蓄電装置１は、バイポーラ電極３の積層体２を備えたバイポーラ電池である。蓄電装置１は、バイポーラ電極３の積層体２と、積層体２を保持するケース５と、積層体２を拘束する拘束体６とを備えている。 The power storage device 1 is a bipolar battery including a stack 2 of bipolar electrodes 3. The power storage device 1 includes a stacked body 2 of the bipolar electrodes 3, a case 5 that holds the stacked body 2, and a restraining body 6 that restrains the stacked body 2.
　積層体２は、セパレータ７を介して複数のバイポーラ電極３を第１方向Ｄ１に沿って積層することによって構成されている。第１方向Ｄ１は、ここではＺ軸方向に沿う方向であり、以下では上下方向または積層方向とも称する。たとえば、後述する端子部材（負極端子部材２５Ａ，正極端子部材２５Ｂ）から離れたバイポーラ電極３を基準とした場合、当該バイポーラ電極３の上下にはセパレータ７を間に挟んで別のバイポーラ電極３がそれぞれ設けられている。バイポーラ電極３のそれぞれは、集電体１１と、集電体１１の第１面１１ａに設けられた正極活物質層１２と、集電体１１の第２面１１ｂに設けられた負極活物質層１３とを有している。第２面１１ｂは、集電体１１の厚み方向において第１面１１ａとは反対側の面である。正極活物質層１２および負極活物質層１３のそれぞれは、集電体１１の中央部に設けられている。すなわち、集電体１１の周縁部１１ｃには、正極活物質層１２および負極活物質層１３が設けられていない。周縁部１１ｃは、集電体１１の表面が露出した未塗工部である。積層体２において、一のバイポーラ電極３の正極活物質層１２は、第１方向Ｄ１において隣り合う一方のバイポーラ電極３の負極活物質層１３とセパレータ７を介して向かい合い、一のバイポーラ電極３の負極活物質層１３は、第１方向Ｄ１において隣り合う他方のバイポーラ電極の正極活物質層１２とセパレータ７を介して向かい合っている。 The laminated body 2 is configured by laminating a plurality of bipolar electrodes 3 via the separator 7 along the first direction D1. The first direction D1 is a direction along the Z-axis direction here, and is also referred to as a vertical direction or a stacking direction below. For example, when a bipolar electrode 3 separated from a terminal member (a negative electrode terminal member 25A, a positive electrode terminal member 25B) described later is used as a reference, another bipolar electrode 3 is interposed above and below the bipolar electrode 3 with a separator 7 interposed therebetween. Each is provided. Each of the bipolar electrodes 3 includes a current collector 11, a positive electrode active material layer 12 provided on the first surface 11 a of the current collector 11, and a negative electrode active material layer provided on the second surface 11 b of the current collector 11. 13 and 13. The second surface 11b is a surface opposite to the first surface 11a in the thickness direction of the current collector 11. Each of the positive electrode active material layer 12 and the negative electrode active material layer 13 is provided in the central portion of the current collector 11. That is, the positive electrode active material layer 12 and the negative electrode active material layer 13 are not provided on the peripheral portion 11c of the current collector 11. The peripheral portion 11c is an uncoated portion where the surface of the current collector 11 is exposed. In the laminated body 2, the positive electrode active material layer 12 of the one bipolar electrode 3 faces the negative electrode active material layer 13 of the one bipolar electrode 3 adjacent in the first direction D1 via the separator 7, and The negative electrode active material layer 13 faces the positive electrode active material layer 12 of the other adjacent bipolar electrode in the first direction D1 via the separator 7.
　正極活物質層１２を構成する正極活物質としては、たとえば水酸化ニッケルが挙げられる。負極活物質層１３を構成する負極活物質としては、たとえば水素吸蔵合金が挙げられる。集電体１１の第２面１１ｂにおける負極活物質層１３の形成領域は、集電体１１の第１面１１ａにおける正極活物質層１２の形成領域に対して一回り大きくてもよい。 Examples of the positive electrode active material forming the positive electrode active material layer 12 include nickel hydroxide. Examples of the negative electrode active material forming the negative electrode active material layer 13 include a hydrogen storage alloy. The area where the negative electrode active material layer 13 is formed on the second surface 11b of the current collector 11 may be slightly larger than the area where the positive electrode active material layer 12 is formed on the first surface 11a of the current collector 11.
　集電体１１の周縁部１１ｃは、正極活物質および負極活物質が塗工されない未塗工領域である。周縁部１１ｃがケース５の内壁５ａに埋没した状態で、ケース５は周縁部１１ｃを保持している。周縁部１１ｃの第１面１１ａと内壁５ａとの間には、それらに接した状態で周縁部１１ｃに沿って樹脂スペーサ４が介在している。樹脂スペーサ４は、隣り合う２つのバイポーラ電極３の間隔を保持する。これにより、第１方向Ｄ１において隣り合う２つの集電体１１間に、当該２つの集電体１１とケース５の内壁５ａとが協働して空間を形成している。当該空間には、たとえば水酸化カリウム水溶液等のアルカリ溶液からなる電解液（不図示）が封入されている。第１方向Ｄ１において隣り合う２つの空間（隣り合う２つのバイポーラ電極３の間に形成される電解液の封入空間）は、樹脂スペーサ４によって互いに液密に分離（シール）されている。樹脂スペーサ４は、たとえば周縁部１１ｃ上に配置された樹脂を硬化することによって形成される。硬化前の樹脂は、液体状でもよく、シート状でもよく、ゲル状でもよい。 The peripheral portion 11c of the current collector 11 is an uncoated region where the positive electrode active material and the negative electrode active material are not coated. The case 5 holds the peripheral portion 11c in a state where the peripheral portion 11c is buried in the inner wall 5a of the case 5. A resin spacer 4 is interposed between the first surface 11a of the peripheral edge portion 11c and the inner wall 5a along the peripheral edge portion 11c while being in contact with them. The resin spacer 4 holds the space between two adjacent bipolar electrodes 3. Thereby, between the two current collectors 11 adjacent to each other in the first direction D1, the two current collectors 11 and the inner wall 5a of the case 5 cooperate to form a space. An electrolytic solution (not shown) made of an alkaline solution such as an aqueous solution of potassium hydroxide is sealed in the space. Two spaces adjacent to each other in the first direction D1 (an enclosed space of an electrolyte formed between two adjacent bipolar electrodes 3) are liquid-tightly separated (sealed) by a resin spacer 4. The resin spacer 4 is formed, for example, by curing the resin arranged on the peripheral portion 11c. The resin before curing may be liquid, sheet, or gel.
　積層体２の一方（Ｚ軸方向正方向）の積層端には、片面に負極活物質層１３のみが設けられた集電体１１Ａが積層されている。当該集電体１１Ａは、セパレータ７を介して負極活物質層１３と最上層のバイポーラ電極３の正極活物質層１２とが向かい合うように配置されている。積層体２の他方（Ｚ軸方向負方向）の積層端には、正極活物質層１２のみが設けられた集電体１１Ｂが積層されている。当該集電体１１Ｂは、セパレータ７を介して正極活物質層１２と最下層のバイポーラ電極３の負極活物質層１３とが向かい合うように配置されている。集電体１１Ａ，１１Ｂの縁部は、バイポーラ電極３の集電体１１と同様に、ケース５の内壁５ａに埋没した状態でケース５に保持されている。集電体１１Ａ，１１Ｂの第１面１１ａの縁領域と内壁５ａとの間には、樹脂スペーサ４が介在している。集電体１１Ａ，１１Ｂは、バイポーラ電極３の集電体１１に比べて厚く形成されてもよい。 A current collector 11A having only the negative electrode active material layer 13 provided on one surface is laminated at one lamination end of the laminate 2 (positive direction in the Z-axis direction). The current collector 11A is arranged so that the negative electrode active material layer 13 and the positive electrode active material layer 12 of the uppermost bipolar electrode 3 face each other with the separator 7 interposed therebetween. On the other (Z-axis direction negative direction) stacking end of the stack 2, a current collector 11B provided with only the positive electrode active material layer 12 is stacked. The current collector 11B is arranged such that the positive electrode active material layer 12 and the negative electrode active material layer 13 of the lowermost bipolar electrode 3 face each other with the separator 7 interposed therebetween. Like the current collector 11 of the bipolar electrode 3, the edge portions of the current collectors 11A and 11B are held in the case 5 while being buried in the inner wall 5a of the case 5. The resin spacer 4 is interposed between the edge region of the first surface 11a of the current collectors 11A and 11B and the inner wall 5a. The current collectors 11A and 11B may be formed thicker than the current collector 11 of the bipolar electrode 3.
　セパレータ７は、たとえばシート状に形成されている絶縁物である。セパレータの形成材料としては、ポリエチレン（ＰＥ）およびポリプロピレン（ＰＰ）等のポリオレフィン系樹脂からなる多孔質フィルム、ならびに、ポリプロピレン等からなる織布または不織布等が例示される。セパレータ７は、フッ化ビニリデン樹脂化合物等で補強されてもよい。なお、セパレータ７は、シート状に限られず、袋状の絶縁物であってもよい。 The separator 7 is, for example, a sheet-shaped insulator. Examples of the material for forming the separator include a porous film made of a polyolefin resin such as polyethylene (PE) and polypropylene (PP), and a woven or non-woven fabric made of polypropylene or the like. The separator 7 may be reinforced with a vinylidene fluoride resin compound or the like. The separator 7 is not limited to the sheet shape, and may be a bag-shaped insulator.
　ケース５は、たとえば絶縁性の樹脂を用いた射出成形によって矩形の筒状に形成されている。樹脂性のケース５を構成する樹脂材料としては、たとえばポリプロピレン（ＰＰ）、ポリフェニレンサルファイド（ＰＰＳ）、変性ポリフェニレンエーテル（変性ＰＰＥ）、および変性ポリフェニレンサルファイド（変性ＰＰＳ）等が挙げられる。ケース５は、バイポーラ電極３の積層によって形成される積層体２の側面２ａを取り囲んで保持する部材である。 The case 5 is formed in a rectangular tubular shape by injection molding using an insulating resin, for example. Examples of the resin material forming the resinous case 5 include polypropylene (PP), polyphenylene sulfide (PPS), modified polyphenylene ether (modified PPE), modified polyphenylene sulfide (modified PPS), and the like. The case 5 is a member that surrounds and holds the side surface 2 a of the stacked body 2 formed by stacking the bipolar electrodes 3.
　ケース５の一側面５ｂ（図５参照）には、複数の注液口５１（図５参照）が設けられている。注液口５１は、ケース５内（具体的には、電解液の封入空間）に電解液を注入するために用いられる。集電体１１は略矩形平板状の外形を有し、一側面５ｂは、たとえば集電体１１の短辺に沿う面である。注液口５１は、集電体１１の長辺に沿ってケース５および樹脂スペーサ４を貫通している。複数の注液口５１は、複数の電解液の封入空間に対応してそれぞれ形成されている。本実施形態では、複数の注液口５１が設けられる位置は、集電体１１の短辺に沿う方向に関して複数箇所（一例として、積層数の半数であって、ここでは５箇所）に分散されており、各箇所において複数（一例として、２つ）の注液口５１が分散数に応じた層数おき（ここでは、５層おき）に重なっている。なお、電解液が注入された状態では、たとえば樹脂による封止等によって注液口５１が塞がれている。 A plurality of liquid injection ports 51 (see FIG. 5) are provided on one side surface 5b (see FIG. 5) of the case 5. The liquid injection port 51 is used to inject the electrolytic solution into the case 5 (specifically, the enclosed space of the electrolytic solution). The current collector 11 has an outer shape of a substantially rectangular flat plate, and the one side surface 5b is, for example, a surface along the short side of the current collector 11. The liquid injection port 51 penetrates the case 5 and the resin spacer 4 along the long side of the current collector 11. The plurality of liquid injection ports 51 are formed respectively corresponding to the enclosed spaces of the plurality of electrolytic solutions. In the present embodiment, the positions at which the plurality of liquid injection ports 51 are provided are distributed at a plurality of positions (as one example, half the number of stacked layers, here 5 positions) in the direction along the short side of the current collector 11. In each location, a plurality (two as an example) of the injection ports 51 are overlapped at every layer number (here, every five layers) according to the dispersion number. In the state where the electrolytic solution is injected, the liquid injection port 51 is closed by, for example, sealing with resin.
　拘束体６は、一対の拘束プレート２１，２１と、拘束プレート２１，２１同士を連結する連結部材（ボルト２２およびナット２３）とによって構成されている。拘束プレート２１は、たとえば鉄等の金属によって平板状に形成されている。ケース５よりも外側に突出する拘束プレート２１の縁部は、ボルト２２を挿通させる挿通孔２１ａを備える。拘束体６における挿通孔２１ａの内周面およびボルト座面には、絶縁処理がなされている。拘束プレート２１の一方の面には、絶縁性部材２４を介して端子部材（負極端子部材２５Ａ，正極端子部材２５Ｂ）が結合されている。絶縁性部材２４の形成材料としては、たとえばフッ素系樹脂またはポリエチレン樹脂が挙げられる。 The restraint body 6 is composed of a pair of restraint plates 21 and 21 and a connecting member (a bolt 22 and a nut 23) that connects the restraint plates 21 and 21 to each other. The restraint plate 21 is formed in a flat plate shape with a metal such as iron. An edge portion of the restraint plate 21 protruding outward from the case 5 is provided with an insertion hole 21a through which the bolt 22 is inserted. The inner peripheral surface of the insertion hole 21a and the bolt seating surface of the restraint body 6 are insulated. A terminal member (negative electrode terminal member 25A, positive electrode terminal member 25B) is coupled to one surface of the restraint plate 21 via an insulating member 24. As a material for forming the insulating member 24, for example, a fluorine resin or a polyethylene resin can be used.
　一方の拘束プレート２１は、第１方向Ｄ１においてケース５よりも上方に位置している。一方の拘束プレート２１は、ケース５の内側で負極端子部材２５Ａと集電体１１Ａとが当接するようにケース５の一端面に突き当てられる。他方の拘束プレート２１は、第１方向Ｄ１においてケース５よりも下方に位置している。他方の拘束プレート２１は、ケース５の内側で正極端子部材２５Ｂと集電体１１Ｂとが当接するようにケース５の他端面に突き当てられる。ボルト２２は、たとえば一方の拘束プレート２１から他方の拘束プレート２１に向かって挿通孔２１ａに通され、他方の拘束プレート２１から突出するボルト２２の先端には、ナット２３が螺合されている。 The one restraint plate 21 is located above the case 5 in the first direction D1. One of the restraint plates 21 is butted against one end surface of the case 5 so that the negative electrode terminal member 25A and the current collector 11A are in contact with each other inside the case 5. The other restraint plate 21 is located below the case 5 in the first direction D1. The other restraint plate 21 is abutted against the other end surface of the case 5 so that the positive electrode terminal member 25B and the current collector 11B contact each other inside the case 5. The bolt 22 is passed through the insertion hole 21 a from, for example, one restraint plate 21 toward the other restraint plate 21, and a nut 23 is screwed onto the tip of the bolt 22 protruding from the other restraint plate 21.
　これにより、積層体２、集電体１１Ａ，１１Ｂ、およびケース５が挟持されてユニット化されると共に、積層体２には第１方向Ｄ１に沿った拘束荷重が付加される。負極端子部材２５Ａは、一方の拘束プレート２１と積層体２との間に配置され、正極端子部材２５Ｂは、他方の拘束プレート２１と積層体２との間に配置される。負極端子部材２５Ａには、引出部２６が接続されている。正極端子部材２５Ｂには、引出部２７が接続されている。引出部２６および引出部２７によって、蓄電装置１の充放電をおこなうことができる。 As a result, the laminate 2, the current collectors 11A and 11B, and the case 5 are sandwiched and unitized, and a restraining load along the first direction D1 is applied to the laminate 2. The negative electrode terminal member 25A is arranged between the one constraining plate 21 and the laminated body 2, and the positive electrode terminal member 25B is arranged between the other constraining plate 21 and the laminated body 2. The lead-out portion 26 is connected to the negative electrode terminal member 25A. The lead-out portion 27 is connected to the positive electrode terminal member 25B. The drawer 26 and the drawer 27 allow the power storage device 1 to be charged and discharged.
　以下、集電体１１について、図２（ａ）および図２（ｂ）を参照しつつ説明する。 The current collector 11 will be described below with reference to FIGS. 2 (a) and 2 (b).
　図２（ａ）に示されるように、集電体１１は、鋼板１０と、鋼板１０の一方の表面１０ａを覆うニッケルのメッキ層３０と、を有する。第１面１１ａはメッキ層３０の表面であり、第２面１１ｂは鋼板１０の表面である。第１面１１ａに粗面化処理を施すことで、第１面１１ａが、鋼板１０の自然面である表面１０ａおよび第２面１１ｂより大きい表面粗さ（算術平均粗さＲａ）を有する。粗面化処理としては、たとえば、エッチング処理およびメッキ処理等の化学的処理、スパッタリング等の物理的処理、ならびに、研磨処理等の機械的処理等の公知の表面処理を適用することができる。本実施形態では、電解ニッケルメッキ処理によって粗面化された第１面１１ａを有するメッキ層３０が形成される。第２面１１ｂは、鋼板１０の自然面、すなわち、上記の粗面化処理が施されていない非粗面である。第２面１１ｂはたとえば平滑面である。鋼板１０としては、たとえばＪＩＳ　Ｇ　３１４１：２００５にて規定される冷間圧延鋼板（ＳＰＣＣ等）が挙げられる。鋼板１０の厚さは、たとえば０．１μｍ以上１０００μｍ以下であり、一例として５０μｍである。メッキ層３０は、電解ニッケルメッキ処理を実施することによって形成される。メッキ層３０の厚さは、たとえば５μｍ以上２０μｍ以下に設計され得る。 As shown in FIG. 2A, the current collector 11 has a steel plate 10 and a nickel plating layer 30 that covers one surface 10 a of the steel plate 10. The first surface 11 a is the surface of the plating layer 30, and the second surface 11 b is the surface of the steel plate 10. By subjecting the first surface 11a to the roughening treatment, the first surface 11a has a surface roughness (arithmetic mean roughness Ra) larger than the surface 10a which is the natural surface of the steel plate 10 and the second surface 11b. As the roughening treatment, known surface treatments such as chemical treatments such as etching treatment and plating treatment, physical treatments such as sputtering, and mechanical treatments such as polishing treatment can be applied. In this embodiment, the plating layer 30 having the first surface 11a roughened by electrolytic nickel plating is formed. The second surface 11b is a natural surface of the steel sheet 10, that is, a non-roughened surface that has not been subjected to the above-described roughening treatment. The second surface 11b is, for example, a smooth surface. Examples of the steel sheet 10 include cold rolled steel sheets (SPCC etc.) defined in JIS G 3141: 2005. The thickness of the steel sheet 10 is, for example, 0.1 μm or more and 1000 μm or less, and is 50 μm as an example. The plating layer 30 is formed by performing electrolytic nickel plating treatment. The thickness of the plating layer 30 can be designed to be, for example, 5 μm or more and 20 μm or less.
　図２（ａ）および図２（ｂ）に示されるように、メッキ層３０は、鋼板１０の表面１０ａ上に設けられる下地ニッケルメッキ層３１と、下地ニッケルメッキ層３１上に設けられる本ニッケルメッキ層３２とを含む。下地ニッケルメッキ層３１と、本ニッケルメッキ層３２とは、互いに異なる条件にて電解メッキ処理を実施することによって形成されている。 As shown in FIGS. 2A and 2B, the plating layer 30 includes a base nickel plating layer 31 provided on the surface 10 a of the steel sheet 10 and a main nickel plating layer provided on the base nickel plating layer 31. And a layer 32. The base nickel plating layer 31 and the main nickel plating layer 32 are formed by performing electrolytic plating treatment under different conditions.
　下地ニッケルメッキ層３１は、第１方向Ｄ１に交差する第２方向Ｄ２に沿って鋼板１０の表面１０ａ上に設けられる電解メッキ層である。第２方向Ｄ２は、ＸＹ平面に沿う方向、もしくは一方の表面１０ａの延在方向に相当する。したがって、第２方向Ｄ２は、必ずしも第１方向Ｄ１に直交しなくてもよい。下地ニッケルメッキ層３１の厚さは、たとえば０．５μｍ以上５μｍ以下であってもよく、０．５μｍ以上２μｍ以下であってもよい。下地ニッケルメッキ層３１は、鋼板１０の表面１０ａの全てを覆っていてもよい。この場合、メッキ層３０にピンホール等が形成されにくくなるので、リーク電流の発生を抑制できる。下地ニッケルメッキ層３１の表面形状は、表面１０ａの形状と異なっている。具体的には、下地ニッケルメッキ層３１は、第１方向Ｄ１に沿って突出する複数の凸部３３を有する。このため、下地ニッケルメッキ層３１の表面形状は、鋼板１０の表面１０ａに沿っておらず、下地ニッケルメッキ層３１の表面粗さは、鋼板１０の表面１０ａの表面粗さよりも大きい。したがって、下地ニッケルメッキ層３１は、平滑メッキ層とは異なるように設けられている。平滑メッキ層は、メッキされる対象の表面に沿った表面形状を有するメッキ層である。 The base nickel plating layer 31 is an electrolytic plating layer provided on the surface 10a of the steel sheet 10 along the second direction D2 that intersects the first direction D1. The second direction D2 corresponds to the direction along the XY plane or the extending direction of the one surface 10a. Therefore, the second direction D2 does not necessarily have to be orthogonal to the first direction D1. The thickness of the underlying nickel plating layer 31 may be, for example, 0.5 μm or more and 5 μm or less, or may be 0.5 μm or more and 2 μm or less. The base nickel plating layer 31 may cover the entire surface 10 a of the steel plate 10. In this case, a pinhole or the like is less likely to be formed in the plated layer 30, so that the generation of leak current can be suppressed. The surface shape of the base nickel plating layer 31 is different from the shape of the surface 10a. Specifically, the base nickel plating layer 31 has a plurality of protrusions 33 protruding along the first direction D1. Therefore, the surface shape of the base nickel plating layer 31 does not follow the surface 10a of the steel plate 10, and the surface roughness of the base nickel plating layer 31 is larger than the surface roughness of the surface 10a of the steel plate 10. Therefore, the base nickel plating layer 31 is provided differently from the smooth plating layer. The smooth plating layer is a plating layer having a surface shape along the surface of the object to be plated.
　複数の凸部３３は、第２方向Ｄ２に沿って不規則に設けられる。下地ニッケルメッキ層３１の厚さが約１μｍまたはそれ以上である場合、凸部３３の平均高さは、たとえば０．４μｍ以上であって、下地ニッケルメッキ層３１の厚さの半分以下でもよい。この場合、本ニッケルメッキ層３２の形状を良好にすることができる。凸部３３の平均高さは、たとえばレーザ共焦点光学系を用いた顕微鏡によって測定される。 The plurality of convex portions 33 are irregularly provided along the second direction D2. When the thickness of the underlying nickel plating layer 31 is about 1 μm or more, the average height of the protrusions 33 may be, for example, 0.4 μm or more, and may be less than half the thickness of the underlying nickel plating layer 31. In this case, the shape of the nickel plating layer 32 can be improved. The average height of the convex portion 33 is measured by, for example, a microscope using a laser confocal optical system.
　本ニッケルメッキ層３２は、下地ニッケルメッキ層３１を被成膜面として設けられる電解メッキ層であり、下地ニッケルメッキ層３１よりも大きい表面粗さを有する。下地ニッケルメッキ層３１および本ニッケルメッキ層３２の表面粗さのそれぞれは、ＪＩＳ　Ｂ　０６０１：２０１３（あるいはＩＳＯ　４２８７：１９９７，　Ａｍｄ．１：２００９）に規定される算術平均粗さＲａで表される。本ニッケルメッキ層３２の表面粗さは、たとえば１．５μｍ以上６．０μｍ以下であり、下地ニッケルメッキ層３１の表面粗さの１．５倍以上６０．０倍以下である。この場合、メッキ層３０にピンホール等が発生することを抑制しつつ、本ニッケルメッキ層３２の表面積を大きくできる。本ニッケルメッキ層３２の厚さは、たとえば５μｍ以上２０μｍ以下である。本ニッケルメッキ層３２は、必ずしも下地ニッケルメッキ層３１の表面全体を覆うように形成されなくてもよい。たとえば、本ニッケルメッキ層３２は、下地ニッケルメッキ層３１から第１方向Ｄ１に突出する複数の突起３４の集合体であってもよい。この場合、本ニッケルメッキ層３２は、粗化メッキ層とも呼称される。複数の突起３４のそれぞれは、対応する凸部３３に接する部分を基端３４ａとして、第１方向Ｄ１に沿って先端３４ｂに至るように形成されている。 The nickel plating layer 32 is an electrolytic plating layer provided with the underlying nickel plating layer 31 as a film formation surface, and has a surface roughness larger than that of the underlying nickel plating layer 31. The surface roughness of the underlying nickel plating layer 31 and the main nickel plating layer 32 is represented by the arithmetic mean roughness Ra defined in JIS B 0601: 2013 (or ISO 4287: 1997, Amd.1: 2009). .. The surface roughness of the present nickel plating layer 32 is, for example, 1.5 μm or more and 6.0 μm or less, which is 1.5 times or more and 60.0 times or less the surface roughness of the underlying nickel plating layer 31. In this case, the surface area of the nickel plating layer 32 can be increased while suppressing the occurrence of pinholes or the like in the plating layer 30. The thickness of the nickel plating layer 32 is, for example, 5 μm or more and 20 μm or less. The present nickel plating layer 32 does not necessarily have to be formed so as to cover the entire surface of the base nickel plating layer 31. For example, the present nickel plating layer 32 may be an assembly of a plurality of protrusions 34 protruding from the base nickel plating layer 31 in the first direction D1. In this case, the nickel plating layer 32 is also called a roughening plating layer. Each of the plurality of protrusions 34 is formed so as to reach the tip 34b along the first direction D1 with the portion in contact with the corresponding protrusion 33 as the base end 34a.
　複数の突起３４の少なくとも一部には、たとえば略球形状を有する複数のニッケル結晶が重畳している。これらのニッケル結晶は、電解メッキ処理により形成された複数の析出金属（付与物）である。このような複数の析出金属が互いに重畳する（積み重なる）ことによって、当該突起３４の第２方向Ｄ２における長さ（長さ寸法）が、基端３４ａにおける第２方向Ｄ２の長さよりも大きい拡大部３４ｃが形成されている。すなわち、少なくとも一部の突起３４は、基端３４ａから先端３４ｂに向かって先太りとなる先太り形状を有している。突起３４における拡大部３４ｃの位置は、必ずしも先端３４ｂでなくてもよいが、少なくとも基端３４ａよりも先端３４ｂに近い。換言すると、先太り形状を有する突起３４において第２方向Ｄ２の長さが最も大きい箇所は、先端３４ｂでなくてもよいが、基端３４ａ以外に位置している。突起３４における拡大部３４ｃの位置は、析出金属の重複態様により突起３４ごとに異なってもよい。 A plurality of nickel crystals having, for example, a substantially spherical shape are superposed on at least a part of the plurality of protrusions 34. These nickel crystals are a plurality of deposited metals (additives) formed by electrolytic plating. Such a plurality of deposited metals are overlapped with each other (stacked), so that the length (length dimension) of the protrusion 34 in the second direction D2 is larger than the length of the base end 34a in the second direction D2. 34c is formed. That is, at least a part of the protrusions 34 has a tapered shape that is tapered from the base end 34a toward the distal end 34b. The position of the enlarged portion 34c in the protrusion 34 does not necessarily have to be the tip end 34b, but is at least closer to the tip end 34b than the base end 34a. In other words, the portion having the largest length in the second direction D2 in the protrusion 34 having the tapered shape does not have to be the tip end 34b, but is located at a position other than the base end 34a. The position of the enlarged portion 34c in the protrusion 34 may be different for each protrusion 34 depending on the overlapping mode of the deposited metal.
　突起３４の平均高さは、たとえば３０μｍ以下である。突起３４の平均高さが３０μｍ以下であることによって、突起３４の折損を良好に抑制できる。突起３４の平均高さは、たとえばレーザ共焦点光学系を用いた顕微鏡を用いて測定される。 The average height of the protrusions 34 is, for example, 30 μm or less. When the average height of the protrusions 34 is 30 μm or less, breakage of the protrusions 34 can be effectively suppressed. The average height of the protrusions 34 is measured using, for example, a microscope using a laser confocal optical system.
　平面視（すなわち、第１方向Ｄ１に沿って見た場合）において、本ニッケルメッキ層３２の単位面積あたりにおける突起３４の数は、たとえば２，５００個以上７，０００個以下である。突起３４の上記数が２，５００個以上であることによって、本ニッケルメッキ層３２の表面積を十分に確保することができる。突起３４の上記数が７，０００個以下であることによって、隣り合う２つの突起３４が接触することを抑制できる。本実施形態では、単位面積は１ｍｍ２である。本ニッケルメッキ層３２の単位面積あたりにおける突起３４の数は、たとえばＪＩＳ　Ｂ　０６０１：２０１３（またはＩＳＯ　４２８７：１９９７，　Ａｍｄ．１：２００９）に規定される粗さ曲線要素の平均長さＲＳｍによって算出される。 The number of the protrusions 34 per unit area of the present nickel plating layer 32 is, for example, 2,500 or more and 7,000 or less in a plan view (that is, when viewed along the first direction D1). When the number of the protrusions 34 is 2,500 or more, the surface area of the nickel plating layer 32 can be sufficiently secured. When the number of the protrusions 34 is 7,000 or less, it is possible to suppress contact between two adjacent protrusions 34. In this embodiment, the unit area is 1 mm 2 . The number of the protrusions 34 per unit area of the nickel plating layer 32 is calculated by the average length RSm of the roughness curve element defined in JIS B 0601: 2013 (or ISO 4287: 1997, Amd. 1: 2009), for example. To be done.
　集電体１１Ａ、１１Ｂは、集電体１１と同様に電解メッキ処理が施された鋼板でもよく、ニッケル箔等の金属箔でもよい。 Like the current collector 11, the current collectors 11A and 11B may be steel plates that have been electrolytically plated, or may be metal foil such as nickel foil.
　上述したメッキ層３０は、たとえば以下に示す手順によって形成することができる。 The above-mentioned plating layer 30 can be formed by the following procedure, for example.
　まず、集電体１１を構成する鋼板１０の表面１０ａ上に、鋼板１０の表面形状とは異なる表面形状を有する下地ニッケルメッキ層３１を形成する。下地ニッケルメッキ層３１は、鋼板１０に対して電解メッキ処理を施すことによって形成される。電解メッキ処理では、たとえばニッケル濃度が０．５ｍｏｌ／Ｌ以上２．０ｍｏｌ／Ｌ以下、温度が４０℃以上６５℃以下に設定されたニッケル浴が用いられる。ニッケル浴とは、ニッケル陽イオンが存在する電解液であり、たとえば塩化ニッケル溶液および硫酸ニッケル溶液等である。ニッケル浴のニッケル濃度が０．５ｍｏｌ／Ｌ以上２．０ｍｏｌ／Ｌ以下であることによって、効率良くメッキ層を形成することができる。また、ニッケル浴の温度が４０℃以上６５℃以下であることによって、下地ニッケルメッキ層３１に設けられる凸部３３の平均高さを良好に制御できる。 First, a base nickel plating layer 31 having a surface shape different from the surface shape of the steel plate 10 is formed on the surface 10a of the steel plate 10 constituting the current collector 11. The base nickel plating layer 31 is formed by subjecting the steel plate 10 to electrolytic plating. In the electrolytic plating treatment, for example, a nickel bath having a nickel concentration of 0.5 mol / L or more and 2.0 mol / L or less and a temperature of 40 ° C. or more and 65 ° C. or less is used. The nickel bath is an electrolytic solution in which nickel cations are present, and examples thereof include nickel chloride solution and nickel sulfate solution. When the nickel concentration of the nickel bath is 0.5 mol / L or more and 2.0 mol / L or less, the plating layer can be efficiently formed. Further, when the temperature of the nickel bath is 40 ° C. or higher and 65 ° C. or lower, the average height of the protrusions 33 provided on the base nickel plating layer 31 can be controlled well.
　下地ニッケルメッキ層３１を形成するための電解メッキ処理を実施する際、たとえば電流密度が０．５Ａ／ｄｍ２以上５．０Ａ／ｄｍ２以下の条件下にて１５０秒以上２，４００秒以下の間、鋼板１０をニッケル浴に浸漬させる。電解メッキ処理中における電流密度を０．５Ａ／ｄｍ２以上５．０Ａ／ｄｍ２以下に設定することによって、下地ニッケルメッキ層３１が平滑メッキ層になることを防止できる。加えて、下地ニッケルメッキ層３１に形成された凸部３３が針形状（もしくはウィスカー形状）を有することを抑制できる。１５０秒以上２，４００秒以下の間、鋼板１０をニッケル浴に浸漬させることによって、下地ニッケルメッキ層３１の厚さを良好に設定できる。 When performing the electrolytic plating treatment for forming the underlying nickel plating layer 31, for example, under a condition where the current density is 0.5 A / dm 2 or more and 5.0 A / dm 2 or less, 150 seconds or more and 2,400 seconds or less. Meanwhile, the steel plate 10 is immersed in a nickel bath. By setting the current density during the electrolytic plating process to 0.5 A / dm 2 or more and 5.0 A / dm 2 or less, it is possible to prevent the underlying nickel plating layer 31 from becoming a smooth plating layer. In addition, it is possible to prevent the convex portion 33 formed on the base nickel plating layer 31 from having a needle shape (or whisker shape). By immersing the steel sheet 10 in the nickel bath for 150 seconds or more and 2,400 seconds or less, the thickness of the base nickel plating layer 31 can be favorably set.
　下地ニッケルメッキ層３１を形成する際に特に重要とされる条件は、ニッケル浴の温度および電流密度である。したがって、ニッケル浴の温度と、電流密度とのいずれも上記範囲内であるとき、ニッケル浴のニッケル濃度と、鋼板１０が浸漬される時間とは、必ずしも上記範囲内でなくてもよい。 The conditions that are particularly important when forming the underlying nickel plating layer 31 are the temperature and current density of the nickel bath. Therefore, when both the temperature of the nickel bath and the current density are within the above ranges, the nickel concentration of the nickel bath and the time for which the steel sheet 10 is immersed need not necessarily be within the above ranges.
　次に、下地ニッケルメッキ層３１上に、本ニッケルメッキ層３２（図２（ｂ）を参照）を形成する。本ニッケルメッキ層３２は、複数の突起３４を含み、下地ニッケルメッキ層３１よりも大きい表面粗さを有する。これにより、鋼板１０と、下地ニッケルメッキ層３１および本ニッケルメッキ層３２を有するメッキ層３０とを備える集電体１１が得られる。本ニッケルメッキ層３２は、下地ニッケルメッキ層３１が形成された鋼板１０に対して電解メッキ処理を施すことによって形成される。この電解メッキ処理では、たとえばニッケル濃度が０．１５ｍｏｌ／Ｌ以上０．３０ｍｏｌ／Ｌ未満、温度が３０℃以上６０℃以下に設定されたワット浴が用いられる。ワット浴とは、硫酸ニッケル、塩化ニッケル、および、ホウ酸を主成分とする電解液である。ワット浴のニッケル濃度が０．１５ｍｏｌ／Ｌ以上０．３０ｍｏｌ／Ｌ未満であることによって、先太り形状を有する突起３４を良好に形成できる。また、ワット浴の温度が３０℃以上６０℃以下であることによって、先太り形状の平均高さを良好に制御できる。 Next, the main nickel plating layer 32 (see FIG. 2B) is formed on the base nickel plating layer 31. The present nickel plating layer 32 includes a plurality of protrusions 34 and has a surface roughness larger than that of the base nickel plating layer 31. Thereby, the current collector 11 including the steel plate 10 and the plated layer 30 having the base nickel plated layer 31 and the main nickel plated layer 32 is obtained. The present nickel plating layer 32 is formed by subjecting the steel plate 10 on which the base nickel plating layer 31 is formed to electrolytic plating. In this electrolytic plating treatment, for example, a Watt bath having a nickel concentration of 0.15 mol / L or more and less than 0.30 mol / L and a temperature of 30 ° C. or more and 60 ° C. or less is used. The Watt's bath is an electrolytic solution containing nickel sulfate, nickel chloride, and boric acid as main components. When the nickel concentration in the Watt bath is 0.15 mol / L or more and less than 0.30 mol / L, the protrusions 34 having a tapered shape can be favorably formed. Further, when the temperature of the Watt bath is 30 ° C. or higher and 60 ° C. or lower, the average height of the tapered shape can be well controlled.
　本ニッケルメッキ層３２を形成するための電解メッキ処理を実施する際、たとえば電流密度が３０Ａ／ｄｍ２以上５０Ａ／ｄｍ２以下の条件下にて３０秒以上６０秒以下の間、鋼板１０をワット浴に浸漬させる。電解メッキ処理中における電流密度を３０Ａ／ｄｍ２以上５０Ａ／ｄｍ２以下に設定することによって、先太り形状を有する突起３４を良好に形成できる。また、３０秒以上６０秒以下の間、鋼板１０をワット浴に浸漬させることによって、本ニッケルメッキ層３２の厚さを良好に設定できる。 Carrying out the electroplating process for forming the nickel plating layer 32, for example a current density of 30A / dm 2 or more 50A / dm 2 or less between at 60 seconds or less 30 seconds or more conditions, the steel plate 10 watts Immerse in bath. By setting the current density in the electrolytic plating process to 30A / dm 2 or more 50A / dm 2 or less, it can be favorably formed a projection 34 having a thickens shape. Further, by immersing the steel plate 10 in the Watt bath for 30 seconds or more and 60 seconds or less, the thickness of the present nickel plating layer 32 can be favorably set.
　本ニッケルメッキ層３２を形成する際に特に重要とされる条件は、ワット浴のニッケル濃度および電流密度である。したがって、ワット浴のニッケル濃度と、電流密度とのいずれも上記範囲内であるとき、ワット浴の温度と、鋼板１０が浸漬される時間とは、必ずしも上記範囲内でなくてもよい。 The conditions that are particularly important when forming the nickel plating layer 32 are the nickel concentration and the current density of the watt bath. Therefore, when both the nickel concentration of the Watt bath and the current density are within the above ranges, the temperature of the Watt bath and the time for which the steel sheet 10 is immersed need not necessarily be within the above range.
　続いて、図３から図５を参照しつつ、集電体１１の第１面１１ａ上に設けられた正極活物質層１２について説明する。 Next, the positive electrode active material layer 12 provided on the first surface 11a of the current collector 11 will be described with reference to FIGS. 3 to 5.
　正極活物質層１２は、略矩形平板状の外形を有する。上述したように、集電体１１は略矩形平板状の外形を有し、正極活物質層１２の短辺および長辺は、集電体１１の短辺及び長辺のそれぞれと平行になるように設けられている。図４に示すように、正極活物質層１２に、集電体１１の長辺に平行な方向に延びる複数（本実施形態では４本）の溝部１５が設けられている。複数の溝部１５はいずれも一方向（本実施形態では、集電体１１の長辺に平行な方向）に沿って連続的に延在している。複数の溝部１５はいずれも延在方向にわたって均一幅を有する。複数の溝部１５は、略同一の溝幅（後述する長さＬ１）を有し、略均等な離間距離で互いに平行に並んでいる。また、複数の溝部１５はいずれも正極活物質層１２を貫通している。つまり、溝部１５は正極活物質層１２の２つの短辺の側端面にそれぞれ複数（本実施形態では４つ）の開口を有する。そのため、複数（本実施形態では４本）の溝部１５により、正極活物質層１２は複数（本実施形態では５つ）の帯状部分１２ａに分断されている。 The positive electrode active material layer 12 has a substantially rectangular flat plate shape. As described above, the current collector 11 has a substantially rectangular flat plate shape, and the short side and the long side of the positive electrode active material layer 12 are parallel to the short side and the long side of the current collector 11, respectively. It is provided in. As shown in FIG. 4, the positive electrode active material layer 12 is provided with a plurality of (four in the present embodiment) groove portions 15 extending in a direction parallel to the long sides of the current collector 11. Each of the plurality of groove portions 15 continuously extends along one direction (in the present embodiment, a direction parallel to the long side of the current collector 11). Each of the plurality of groove portions 15 has a uniform width in the extending direction. The plurality of groove portions 15 have substantially the same groove width (a length L1 described later), and are arranged in parallel with each other at a substantially uniform distance. Further, all of the plurality of groove portions 15 penetrate the positive electrode active material layer 12. That is, the groove 15 has a plurality of openings (four in this embodiment) on the side end surfaces of the two short sides of the positive electrode active material layer 12. Therefore, the positive electrode active material layer 12 is divided into a plurality (five in this embodiment) of band-shaped portions 12a by a plurality (four in this embodiment) of the groove portions 15.
　本実施形態において、正極活物質層１２の幅方向における長さＬ２は１００ｍｍ以上３３０ｍｍ以下であってもよい。溝部１５の幅方向における長さＬ１は、帯状部分１２ａの幅方向における長さＬ３の０．０４倍以上０．８０倍以下であってもよい。あるいは、長さＬ１は、長さＬ３の０．０８倍以上０．４０倍以下であってもよい。長さＬ３は、２５ｍｍ以上５０ｍｍ以下であってもよい。また、図５に示すように、長さＬ１は、上記注液口５１の幅方向における長さＬ４よりも小さい。長さＬ４は、１ｍｍ以上２０ｍｍ以下であってもよい。 In the present embodiment, the length L2 in the width direction of the positive electrode active material layer 12 may be 100 mm or more and 330 mm or less. The length L1 of the groove portion 15 in the width direction may be 0.04 times or more and 0.80 times or less than the length L3 of the strip portion 12a in the width direction. Alternatively, the length L1 may be 0.08 times or more and 0.40 times or less than the length L3. The length L3 may be 25 mm or more and 50 mm or less. Further, as shown in FIG. 5, the length L1 is smaller than the length L4 of the liquid injection port 51 in the width direction. The length L4 may be 1 mm or more and 20 mm or less.
　溝部１５は、たとえば正極活物質層１２を塗工する際に形成することができる。具体的には、正極活物質、導電助剤、および溶媒を含む正極ペーストを、ダイコータを用いて集電体１１上に塗工する場合、ダイコータのペースト吐出口にシム等の障害物を設けることで、溝部１５を形成することができる。 The groove 15 can be formed when the positive electrode active material layer 12 is applied, for example. Specifically, when a positive electrode paste containing a positive electrode active material, a conductive additive, and a solvent is applied on the current collector 11 using a die coater, an obstacle such as a shim should be provided at the paste discharge port of the die coater. Thus, the groove portion 15 can be formed.
　上述したとおり、正極活物質層１２が設けられる集電体１１の第１面１１ａは、複数の突起３４が設けられた粗面領域である。粗面領域は、正極活物質層１２よりも広い領域である。本実施形態では、第１面１１ａの全面が粗面領域である。正極活物質層は、粗面領域内に設けられている。そのため、図３に示すように、正極活物質層１２に設けられた溝部１５から第１面１１ａの粗面領域が露出する。すなわち、溝部１５の溝底は、集電体１１の第１面１１ａの粗面領域である。集電体１１の第１面１１ａの粗面領域では、粗面化されていない平滑面に比べて、電解液が留まりやすい。たとえば、電解液は、突起３４の隙間に入り込むようにして、粗面領域に染み込む。そのため、溝部１５から露出した粗面領域において電解液をある程度保液することができる。 As described above, the first surface 11a of the current collector 11 provided with the positive electrode active material layer 12 is a rough surface area provided with the plurality of protrusions 34. The rough surface area is an area wider than the positive electrode active material layer 12. In the present embodiment, the entire first surface 11a is a rough surface area. The positive electrode active material layer is provided in the rough surface area. Therefore, as shown in FIG. 3, the rough surface region of the first surface 11a is exposed from the groove 15 provided in the positive electrode active material layer 12. That is, the groove bottom of the groove portion 15 is a rough surface region of the first surface 11 a of the current collector 11. In the rough surface region of the first surface 11a of the current collector 11, the electrolytic solution is more likely to stay than in the non-roughened smooth surface. For example, the electrolytic solution penetrates into the gap between the protrusions 34 and soaks into the rough surface area. Therefore, the electrolytic solution can be retained to some extent in the rough surface region exposed from the groove portion 15.
　蓄電装置１の充電時においては、正極活物質が膨張して正極活物質層１２に電解液が流れ込み、蓄電装置１の放電時においては、正極活物質が収縮して正極活物質層１２から電解液が流れ出す。放電時に正極活物質層１２から電解液が流れ出す際、正極活物質層１２の溝部１５の溝底である粗面領域に電解液が保液される。そのため、充電時に粗面領域に保液された電解液を正極活物質層１２に供給することができる。特に、図３の符号Ｓで示された正極活物質層１２の帯状部分１２ａの近傍（帯状部分１２ａの形成領域と粗面領域との隣接部分）においては、粗面領域に保液された電解液をより素早く正極活物質層１２に供給することができる。 When the power storage device 1 is charged, the positive electrode active material expands and the electrolytic solution flows into the positive electrode active material layer 12, and when the power storage device 1 is discharged, the positive electrode active material contracts and the positive electrode active material layer 12 is electrolyzed. Liquid flows out. When the electrolytic solution flows out from the positive electrode active material layer 12 during discharge, the electrolytic solution is retained in the rough surface region that is the groove bottom of the groove portion 15 of the positive electrode active material layer 12. Therefore, the electrolytic solution retained in the rough surface region during charging can be supplied to the positive electrode active material layer 12. In particular, in the vicinity of the strip-shaped portion 12a of the positive electrode active material layer 12 (adjacent portion between the region where the strip-shaped portion 12a is formed and the rough surface region) shown by symbol S in FIG. The liquid can be supplied to the positive electrode active material layer 12 more quickly.
　以上において説明したとおり、蓄電装置１においては、正極活物質層１２の溝部１５の溝底である集電体１１の第１面１１ａの粗面領域が電解液を保液することで、充電時に正極活物質層１２内に流れ込む電解液を確保することができる。このため、電解液が不足する事態が生じにくい。電解液が不足した場合には、集電体１１と正極活物質層１２との間に高抵抗部分が生じ、電池特性が劣化する。蓄電装置１によれば、充電時に電解液が不足する事態が効果的に抑制されているため、高い電池特性が実現されている。 As described above, in the electricity storage device 1, the rough surface region of the first surface 11a of the current collector 11, which is the groove bottom of the groove portion 15 of the positive electrode active material layer 12, retains the electrolytic solution, so that during charging, It is possible to secure the electrolytic solution that flows into the positive electrode active material layer 12. For this reason, a situation in which the electrolyte is insufficient is unlikely to occur. When the electrolyte solution is insufficient, a high resistance portion is generated between the current collector 11 and the positive electrode active material layer 12, and the battery characteristics deteriorate. According to the power storage device 1, a situation in which the electrolyte solution is insufficient at the time of charging is effectively suppressed, and thus high battery characteristics are realized.
　集電体１１の第１面１１ａの粗面領域は、先太り形状を有する複数の突起３４によって構成されている。そのため、隣接する２つの突起３４間の空間に電解液を保液することができるので、より多量の電解液を保液することができる。 The rough surface area of the first surface 11 a of the current collector 11 is composed of a plurality of protrusions 34 having a tapered shape. Therefore, since the electrolytic solution can be retained in the space between the two adjacent protrusions 34, a larger amount of electrolytic solution can be retained.
　溝部１５は、正極活物質層１２の側端面に２つの開口を有し、２つの開口を連通しているので、ケース５内に電解液を注入したときに、電解液が正極活物質層１２に設けられた溝部１５を通って速やかに流れる。特に、溝部１５の延在方向をケース５内への電解液の注液方向（注液口５１の貫通方向）に沿うように設計することで、電解液が正極活物質層１２に設けられた溝部１５を通ってより速やかにケース内に行き渡る。そのため、ケース５内へ電解液を効率良く注液することができる。 Since the groove portion 15 has two openings on the side end surface of the positive electrode active material layer 12 and communicates the two openings, when the electrolytic solution is injected into the case 5, the electrolytic solution is filled with the positive electrode active material layer 12. It flows quickly through the groove portion 15 provided in the. In particular, the electrolytic solution was provided in the positive electrode active material layer 12 by designing the extending direction of the groove portion 15 so as to be along the injection direction of the electrolytic solution into the case 5 (the penetrating direction of the injection port 51). It spreads through the groove 15 more quickly into the case. Therefore, the electrolytic solution can be efficiently injected into the case 5.
　なお、本実施形態では、集電体１１の第１面１１ａの全面が粗面領域であることにより、正極活物質層１２の外周にも粗面領域が露出している。そのため、正極活物質層１２の外周においても、溝部１５の溝底と同様に、粗面領域に電解液が保液される。すなわち、正極活物質層１２の溝部１５の溝底および正極活物質層１２の外周の粗面領域に電解液が保液されるので、より多量の電解液を保液することができる。その結果、充電時に電解液が不足する事態がより効果的に抑制されている。 In the present embodiment, the entire first surface 11a of the current collector 11 is a rough surface area, so that the rough surface area is also exposed on the outer periphery of the positive electrode active material layer 12. Therefore, also on the outer periphery of the positive electrode active material layer 12, the electrolytic solution is retained in the rough surface region, similarly to the groove bottom of the groove portion 15. That is, since the electrolytic solution is retained in the groove bottoms of the groove portions 15 of the positive electrode active material layer 12 and the rough surface region of the outer periphery of the positive electrode active material layer 12, a larger amount of electrolytic solution can be retained. As a result, the situation in which the electrolyte solution is insufficient during charging is more effectively suppressed.
　本実施形態では、粗面領域は、正極活物質層１２よりも広い領域であって、正極活物質層１２は、粗面領域内に設けられている。そのため、正極活物質、導電助剤、および溶媒を含む正極ペーストを塗布し、塗布した正極ペーストを乾燥させて正極活物質層１２を形成する際に、粗面領域の複数の突起３４の少なくとも一部が正極活物質層１２に入り込む。したがって、突起３４によるアンカー効果で、集電体１１に対する正極活物質層１２の密着力が向上する。 In the present embodiment, the rough surface area is wider than the positive electrode active material layer 12, and the positive electrode active material layer 12 is provided in the rough surface area. Therefore, when the positive electrode paste containing the positive electrode active material, the conductive auxiliary agent, and the solvent is applied and the applied positive electrode paste is dried to form the positive electrode active material layer 12, at least one of the plurality of protrusions 34 in the rough surface region is formed. The part enters the positive electrode active material layer 12. Therefore, the anchor effect of the protrusions 34 improves the adhesion of the positive electrode active material layer 12 to the current collector 11.
　蓄電装置１では、図３に示すように、積層体２の積層方向（第１方向Ｄ１）において正極活物質層１２と隣り合うセパレータ７の一部７ａが、正極活物質層１２に設けられた溝部１５に入り込んでいる。セパレータ７の元々の厚さよりも小さくなるように積層体２の拘束時にセパレータ７を圧縮することで、セパレータ７の一部７ａは溝部１５に入り込んだ状態となる。セパレータ７が、多孔質フィルム、織布、および不織布等の形態である場合、電解液を吸液および保液することができる。そのため、放電時に正極活物質層１２から電解液が流れ出す際、集電体１１の第１面１１ａの粗面領域に加えて、セパレータ７でも電解液が保液される。特に、蓄電装置１では、セパレータ７における正極活物質層１２の溝部１５に入り込んだ部分７ａに電解液が保液されることで、溝部１５内に保液される電解液の量が増す。したがって、蓄電装置１では、溝部１５の溝底である第１面１１ａの粗面領域、および正極活物質層１２の溝部１５に入り込んだセパレータ７の一部７ａから正極活物質層１２に電解液を供給することができ、充電時に電解液が不足する事態がより効果的に抑制されている。 In the electricity storage device 1, as shown in FIG. 3, the positive electrode active material layer 12 is provided with a part 7 a of the separator 7 that is adjacent to the positive electrode active material layer 12 in the stacking direction of the stacked body 2 (first direction D <b> 1). It has entered the groove 15. By compressing the separator 7 when the laminated body 2 is constrained so as to be smaller than the original thickness of the separator 7, a part 7 a of the separator 7 enters the groove 15. When the separator 7 is in the form of a porous film, a woven fabric, a non-woven fabric or the like, it can absorb and retain the electrolytic solution. Therefore, when the electrolytic solution flows out from the positive electrode active material layer 12 during discharging, the electrolytic solution is retained in the separator 7 in addition to the rough surface region of the first surface 11a of the current collector 11. Particularly, in the electricity storage device 1, since the electrolytic solution is retained in the portion 7a of the positive electrode active material layer 12 of the separator 7 that has entered the groove portion 15, the amount of the electrolytic solution retained in the groove portion 15 increases. Therefore, in the electricity storage device 1, the electrolytic solution is applied to the positive electrode active material layer 12 from the rough surface region of the first surface 11 a that is the groove bottom of the groove portion 15 and the part 7 a of the separator 7 that has entered the groove portion 15 of the positive electrode active material layer 12. Can be supplied, and the situation in which the electrolyte solution is insufficient during charging is more effectively suppressed.
　ところで、蓄電装置１が電池容量に対して過剰に充電された場合、ケース５内において電解液中の水が電気分解されて酸素が発生する。この酸素は、バイポーラ電極３の正極活物質層１２において発生し、第１方向Ｄ１に隣り合う別のバイポーラ電極３の負極活物質層１３に吸収される。隣り合う２つのバイポーラ電極３はセパレータ７を介して積層されているので、正極活物質層１２から負極活物質層１３に移動する酸素は、セパレータ７の縁部を回り込むように移動する。 By the way, when the power storage device 1 is overcharged with respect to the battery capacity, water in the electrolytic solution is electrolyzed in the case 5 to generate oxygen. This oxygen is generated in the positive electrode active material layer 12 of the bipolar electrode 3 and is absorbed by the negative electrode active material layer 13 of another bipolar electrode 3 adjacent in the first direction D1. Since the two adjacent bipolar electrodes 3 are stacked with the separator 7 interposed therebetween, oxygen moving from the positive electrode active material layer 12 to the negative electrode active material layer 13 moves so as to wrap around the edge of the separator 7.
　蓄電装置１においては、正極活物質層１２が溝部１５を有するので、正極活物質層１２から負極活物質層１３に移動する酸素を、溝部１５によってセパレータ７の縁部に向けて導くことができる。これにより、正極活物質層１２に溝部１５が形成されていない場合と比較して、発生した酸素によって正極活物質層１２内の電解液が正極活物質層１２外に向けて押し出されることを抑制することが可能となる。 In power storage device 1, since positive electrode active material layer 12 has groove portion 15, oxygen moving from positive electrode active material layer 12 to negative electrode active material layer 13 can be guided to the edge portion of separator 7 by groove portion 15. .. Thereby, as compared with the case where the groove portion 15 is not formed in the positive electrode active material layer 12, it is possible to suppress the electrolytic solution in the positive electrode active material layer 12 from being pushed out by the generated oxygen toward the outside of the positive electrode active material layer 12. It becomes possible to do.
　溝部１５は、集電体１１の面内方向のうちの一方向に沿って延在しており、各溝部１５は、正極活物質層１２の一対の帯状部分１２ａによって溝部１５の延在方向に交差する幅方向に挟まれている。幅方向において、溝部１５の長さＬ１は、帯状部分１２ａの長さＬ３の０．０４倍以上０．８０倍以下であってもよい。長さＬ１を長さＬ３の０．０４倍以上とすることにより、バイポーラ電極３の正極活物質層１２において発生した酸素を溝部１５によって円滑に導くことができる。長さＬ１を長さＬ３の０．８０倍以下とすることにより、所望の電池容量を確保しやすい。 The groove portions 15 extend along one of the in-plane directions of the current collector 11, and each groove portion 15 is formed by the pair of strip-shaped portions 12 a of the positive electrode active material layer 12 in the extending direction of the groove portions 15. It is sandwiched in the width direction that intersects. In the width direction, the length L1 of the groove portion 15 may be 0.04 times or more and 0.80 times or less than the length L3 of the strip portion 12a. By setting the length L1 to be 0.04 times or more the length L3, oxygen generated in the positive electrode active material layer 12 of the bipolar electrode 3 can be smoothly guided by the groove portion 15. By setting the length L1 to 0.80 times or less the length L3, it is easy to secure a desired battery capacity.
　蓄電装置１において、長さＬ３は、２５ｍｍ以上５０ｍｍ以下であってもよい。長さＬ３を２５ｍｍ以上とすることにより、所望の電池容量を確保しやすい。長さＬ３を５０ｍｍ以下とすることにより、バイポーラ電極３の正極活物質層１２において発生した酸素が溝部１５に到達しやすくなる。 In the power storage device 1, the length L3 may be 25 mm or more and 50 mm or less. By setting the length L3 to 25 mm or more, it is easy to secure a desired battery capacity. By setting the length L3 to 50 mm or less, oxygen generated in the positive electrode active material layer 12 of the bipolar electrode 3 easily reaches the groove portion 15.
　［実施例］
　以下、実施例について説明するが、上記実施形態は実施例に限定されない。 [Example]
Examples will be described below, but the above embodiment is not limited to the examples.
　（実施例１）
　実施例１に係る蓄電装置の構成は、上記実施形態に係る蓄電装置１と同様である。実施例１では、溝部１５の長さＬ１を３ｍｍ、帯状部分１２ａの数を５個、帯状部分１２ａの長さＬ３を３３ｍｍとした。 (Example 1)
The configuration of the power storage device according to the first embodiment is the same as that of the power storage device 1 according to the above-described embodiment. In Example 1, the length L1 of the groove portion 15 was 3 mm, the number of the strip-shaped portions 12a was 5, and the length L3 of the strip-shaped portion 12a was 33 mm.
　（比較例１）
　比較例１に係る蓄電装置は、第１面１１ａに粗面化処理を施していない点で上記実施例１に係る蓄電装置と相違し、その他の点において上記実施例１に係る蓄電装置と同様に構成されている。 (Comparative Example 1)
The power storage device according to Comparative Example 1 is different from the power storage device according to the first embodiment in that the first surface 11a is not roughened, and is otherwise similar to the power storage device according to the first embodiment. Is configured.
　（電池特性の評価方法１）
　実施例１および比較例１の蓄電装置に対し、電池特性として、充電および放電を繰り返した場合の蓄電装置の電池容量の変化率を計測した。図６は、サイクル数と容量変化率との関係を示すグラフである。図６に示すグラフにおいて、横軸は、サイクル数を示し、縦軸は、容量変化率を示す。蓄電装置のＳＯＣ(充電状態；State　of　Charge)が８０％に達したときから０％（完全放電状態）となるまで放電し、その後再び充電してＳＯＣが８０％に達するまでを１サイクルとした。容量変化率は、１サイクル目の蓄電装置の電池容量を１としたときの各サイクルにおける電池容量の割合である。蓄電装置の電池容量は、充放電装置(例：東洋システム株式会社製)によって計測した。 (Battery characteristic evaluation method 1)
As the battery characteristics of the power storage devices of Example 1 and Comparative Example 1, the rate of change in the battery capacity of the power storage device when charging and discharging were repeated was measured. FIG. 6 is a graph showing the relationship between the number of cycles and the capacity change rate. In the graph shown in FIG. 6, the horizontal axis represents the number of cycles and the vertical axis represents the capacity change rate. One cycle is from when the SOC (state of charge) of the power storage device reaches 80% until it reaches 0% (completely discharged state), and then the battery is recharged until the SOC reaches 80%. .. The capacity change rate is the ratio of the battery capacity in each cycle when the battery capacity of the power storage device in the first cycle is 1. The battery capacity of the power storage device was measured by a charging / discharging device (eg: manufactured by Toyo System Co., Ltd.).
　（電池特性の評価結果１）
　図６に示されるように、実施例１においては、サイクル数が８００を超えても電池容量がほぼ変化しないことがわかった。比較例１においては、サイクル数が６７０を超えたあたりから電池容量は低下していくことがわかった。比較例１の電池容量の変化率の悪化は、正極活物質に電解液を供給できなくなったことによる液枯れに起因すると考えられる。図６により、比較例１に対し、実施例１の方が電池容量の低下を抑制できていることがわかった。 (Battery characteristics evaluation result 1)
As shown in FIG. 6, in Example 1, it was found that the battery capacity hardly changed even when the number of cycles exceeded 800. In Comparative Example 1, it was found that the battery capacity decreased as the number of cycles exceeded 670. It is considered that the deterioration of the rate of change in battery capacity in Comparative Example 1 is due to liquid depletion due to the inability to supply the electrolytic solution to the positive electrode active material. From FIG. 6, it was found that the battery capacity of Example 1 was more suppressed than that of Comparative Example 1.
　（実施例２～１１）
　実施例２～１１、及び参考例１に係る蓄電装置の構成は、上記実施形態に係る蓄電装置１と同様である。実施例２～１１は、正極活物質層１２の長さＬ２を１００ｍｍ、帯状部分１２ａの数を２つ、溝部１５の数を１つとし、帯状部分１２ａの長さＬ３及び溝部１５の長さＬ１を変化させた。 (Examples 2 to 11)
The configurations of the power storage devices according to Examples 2 to 11 and Reference Example 1 are the same as those of the power storage device 1 according to the above-described embodiment. In Examples 2 to 11, the length L2 of the positive electrode active material layer 12 was 100 mm, the number of the strip portions 12a was 2, the number of the groove portions 15 was 1, and the length L3 of the strip portion 12a and the length of the groove portions 15 were set. L1 was changed.
　（参考例１）
　参考例１に係る蓄電装置は、帯状部分１２ａの数を１つとし、溝部１５を設けない点で上記実施例２～１１に係る蓄電装置と相違し、その他の点において上記実施例２～１１に係る蓄電装置と同様に構成されている。 (Reference example 1)
The power storage device according to the first reference example is different from the power storage devices according to the second to eleventh embodiments in that the number of the strip portions 12a is one and the groove portion 15 is not provided, and in other respects, the second to eleventh embodiments are described. It is configured similarly to the power storage device according to.
　（電池特性の評価方法２）
　実施例２～１１、及び参考例１の蓄電装置に対し、電池容量を計測した。表１は、計測結果を示す。表１の各容量（電池容量）は、参考例１の蓄電装置の電池容量を１００としたときの各実施例における電池容量の割合を示す。 (Battery characteristics evaluation method 2)
The battery capacities of the power storage devices of Examples 2 to 11 and Reference Example 1 were measured. Table 1 shows the measurement results. Each capacity (battery capacity) in Table 1 shows the ratio of the battery capacity in each example when the battery capacity of the power storage device of Reference Example 1 is 100.
Figure JPOXMLDOC01-appb-T000001
Figure JPOXMLDOC01-appb-T000001
　（電池特性の評価結果２）
　表１に示されるように、実施例４において、７０％以上の電池容量が確保されることがわかった。したがって、溝部１５の長さＬ１が帯状部分１２ａの長さＬ３の０．８０倍以下である場合には、蓄電装置が７０％以上の電池容量を有することがわかった。実施例６において、８０％以上の電池容量が確保されることがわかった。したがって、溝部１５の長さＬ１が帯状部分１２ａの長さＬ３の０．４０倍以下である場合には、蓄電装置が８０％以上の電池容量を有することがわかった。そのため、溝部１５の長さＬ１を帯状部分１２ａの長さＬ３の０．８０倍以下とすることによって、より十分な電池容量を確保でき、０．４０倍以下とすることによって、さらに十分な電池容量を確保できることがわかった。 (Battery characteristics evaluation result 2)
As shown in Table 1, in Example 4, it was found that a battery capacity of 70% or more was secured. Therefore, it was found that the power storage device had a battery capacity of 70% or more when the length L1 of the groove 15 was 0.80 times or less the length L3 of the strip portion 12a. In Example 6, it was found that a battery capacity of 80% or more was secured. Therefore, it was found that the power storage device had a battery capacity of 80% or more when the length L1 of the groove 15 was 0.40 times or less the length L3 of the strip portion 12a. Therefore, by setting the length L1 of the groove portion 15 to be 0.80 times or less of the length L3 of the strip portion 12a, a more sufficient battery capacity can be secured, and by setting it to 0.40 times or less, a further sufficient battery capacity can be obtained. It turns out that the capacity can be secured.
　（電池特性の評価方法３）
　さらに、実施例２～１１、及び参考例１の蓄電装置に対し、充電前後の内圧の測定を行った。充電前の蓄電装置の内圧及び、充電後の蓄電装置の内圧を圧力トランスミッタ（長野計器株式会社製ＫＭ１８）によって測定した。蓄電装置のＳＯＣが０％から１００％となるまで０．５Ｃで充電し、１時間休止した時の内圧を、充電後の蓄電装置の内圧とした。実施例２～１１、及び参考例１の蓄電装置の内圧の評価結果を評価結果２と併せて表２に示す。なお、表２中の「内圧」は充電前の内圧を０とした時の充電後の内圧（すなわち、充電前後の内圧の上昇値）である。 (Battery characteristics evaluation method 3)
Further, the internal pressures before and after charging were measured for the power storage devices of Examples 2 to 11 and Reference Example 1. The internal pressure of the power storage device before charging and the internal pressure of the power storage device after charging were measured by a pressure transmitter (KM18 manufactured by Nagano Keiki Co., Ltd.). The internal pressure of the power storage device charged at 0.5C until the SOC changed from 0% to 100% and rested for 1 hour was defined as the internal pressure of the power storage device after charging. Table 2 shows the evaluation results of the internal pressure of the power storage devices of Examples 2 to 11 and Reference Example 1 together with the evaluation result 2. The "internal pressure" in Table 2 is the internal pressure after charging when the internal pressure before charging is 0 (that is, the increase value of the internal pressure before and after charging).
Figure JPOXMLDOC01-appb-T000002
Figure JPOXMLDOC01-appb-T000002
　（電池特性の評価結果３）
　表２に示されるように、参考例１と比べて実施例２～１１の蓄電装置は充電後の内圧上昇が抑制された。さらに、実施例２～１０の蓄電装置は実施例１１の蓄電装置と比べて、充電後の内圧上昇が顕著に抑制された。そのため、溝部１５の長さＬ１を帯状部分１２ａの長さＬ３の０．０４倍以上とすることによって、充電後の蓄電装置の内圧上昇をより十分に抑制でき、０．０８倍以上とすることによって、さらに十分に抑制できることがわかった。 (Battery characteristics evaluation result 3)
As shown in Table 2, in the power storage devices of Examples 2 to 11, compared with Reference Example 1, the increase in internal pressure after charging was suppressed. Furthermore, in the power storage devices of Examples 2 to 10, the increase in internal pressure after charging was significantly suppressed as compared with the power storage devices of Example 11. Therefore, by setting the length L1 of the groove portion 15 to be 0.04 times or more the length L3 of the strip portion 12a, it is possible to more sufficiently suppress the increase in the internal pressure of the power storage device after charging, and to set it to 0.08 times or more. It has been found that this can be suppressed more sufficiently.
　また、溝部１５の長さＬ１を帯状部分１２ａの長さＬ３の０．０４倍以上０．８０倍以下とすることによって、より十分な電池容量を確保できるとともに充電後の蓄電装置の内圧上昇を十分に抑制でき、０．０８倍以上０．４０倍以下とすることによって、さらに十分な電池容量を確保できるとともに充電後の蓄電装置の内圧上昇をさらに十分に抑制できることがわかった。 Further, by setting the length L1 of the groove 15 to be 0.04 times or more and 0.80 times or less the length L3 of the strip-shaped portion 12a, it is possible to secure a more sufficient battery capacity and increase the internal pressure of the power storage device after charging. It has been found that it is possible to sufficiently suppress, and by setting it to be 0.08 times or more and 0.40 times or less, it is possible to further secure a sufficient battery capacity and it is possible to further sufficiently suppress an increase in internal pressure of the power storage device after charging.
　本開示に係る蓄電装置は、上記実施形態に限定されず、他に様々な変形が可能である。 The power storage device according to the present disclosure is not limited to the above embodiment, and various modifications can be made.
　たとえば、集電体の第１面の全体が粗面化されてもよいし、第１面の一部が粗面化されてもよい。集電体の第１面のみが粗面化されてもよいし、第１面および第２面の両方が粗面化されてもよい。集電体の第２面に設けられる負極活物質層に、正極活物質層と同様の溝部が設けられてもよい。この場合、負極活物質層の溝部と正極活物質層の溝部とは、互いに対応する領域に設けられてもよく、異なる領域に設けられてもよい。 For example, the entire first surface of the current collector may be roughened, or a part of the first surface may be roughened. Only the first surface of the current collector may be roughened, or both the first surface and the second surface may be roughened. A groove similar to that of the positive electrode active material layer may be provided in the negative electrode active material layer provided on the second surface of the current collector. In this case, the groove part of the negative electrode active material layer and the groove part of the positive electrode active material layer may be provided in regions corresponding to each other or may be provided in different regions.
　上記実施形態では、溝部は集電体の長辺に平行な方向に延びていたが、溝部が延びる方向はこれに限らない。たとえば、溝部は集電体の短辺に平行な方向に延びるように形成されていてもよい。つまり、溝部は集電体の面内方向（すなわち、集電体の第１面に沿う方向であって、ここでは、ＸＹ平面に平行な方向）に延びるように形成されていればよい。 In the above embodiment, the groove extends in the direction parallel to the long side of the current collector, but the direction in which the groove extends is not limited to this. For example, the groove may be formed so as to extend in a direction parallel to the short side of the current collector. That is, the groove may be formed so as to extend in the in-plane direction of the current collector (that is, the direction along the first surface of the current collector, here, the direction parallel to the XY plane).
　上記実施形態では、溝部は集電体の長辺に平行な方向に直線状に正極活物質層を貫通していたが、溝部は正極活物質層の側端面に２つの開口を有すれば、直線状に限定されない。たとえば、溝部が正極活物質層の短辺の側端面に１つの開口を有し、正極活物質層の長辺の側端面にもう一つ開口を有している場合、溝部はこれら２つの開口を繋ぐように湾曲および屈曲した形状であってもよい。 In the above embodiment, the groove portion linearly penetrates the positive electrode active material layer in a direction parallel to the long side of the current collector, but the groove portion has two openings on the side end surface of the positive electrode active material layer, The shape is not limited to a straight line. For example, when the groove has one opening at the side end surface of the short side of the positive electrode active material layer and another opening at the side end surface of the long side of the positive electrode active material layer, the groove section has these two openings. The shape may be curved and bent so as to connect to each other.
　上記実施形態では、溝部は一方向に沿って連続的に延在していたが、溝部の構成はこれに限らない。たとえば、溝部は一方向に沿って間欠的に延在していてもよい。 In the above embodiment, the groove portion continuously extends along one direction, but the configuration of the groove portion is not limited to this. For example, the groove may extend intermittently along one direction.
　溝部の数及び正極活物質層の帯状部分の数は適宜変更可能である。たとえば、正極活物質層には溝部が１つのみ設けられていてもよい。正極活物質層は、溝部の延在方向に交差する幅方向に溝部を挟む一対の帯状部分を含んでいてもよい。 The number of grooves and the number of strips of the positive electrode active material layer can be changed as appropriate. For example, the positive electrode active material layer may be provided with only one groove. The positive electrode active material layer may include a pair of strip-shaped portions sandwiching the groove portion in the width direction intersecting the extending direction of the groove portion.
　上記実施形態では、集電体の第１面は、全体が粗面化された粗面領域を有し、正極活物質層はすべて粗面領域上に設けられていたが、正極活物質層が設けられる領域はこの限りでない。たとえば、集電体が第１面の一部に粗面領域を有し、正極活物質層は粗面領域の表面上および粗面化されていない領域の表面上に形成されてもよい。この場合、溝部は粗面化されていない領域を露出させていてもよい。 In the above-described embodiment, the first surface of the current collector has a roughened surface area that is roughened as a whole, and the positive electrode active material layer is entirely provided on the roughened surface area. The area provided is not limited to this. For example, the current collector may have a rough surface area on a part of the first surface, and the positive electrode active material layer may be formed on the surface of the rough surface area and the surface of the non-roughened area. In this case, the groove may expose a region that is not roughened.
　バイポーラ電極の積層数および注液口の数は適宜変更可能である。たとえば、バイポーラ電極の積層数および注液口の数がそれぞれ２４であってもよい。この場合、注液口が設けられる位置が集電体の短辺に沿う方向に関して１２箇所に分散されており、各箇所において２つの注液口が１２層おきに重なっていてもよい。あるいは、注液口が設けられる位置が集電体の短辺に沿う方向に関して積層数に応じた箇所（たとえば、２４層の場合、２４箇所）に分散されていてもよい。換言すると、集電体の短辺に沿う方向に関して、すべての注液口の位置が互いに異なっていてもよい。 The number of stacked bipolar electrodes and the number of injection ports can be changed appropriately. For example, the number of stacked bipolar electrodes and the number of injection ports may be 24 each. In this case, the positions where the liquid injection ports are provided are distributed in 12 positions in the direction along the short side of the current collector, and two liquid injection ports may be overlapped every 12 layers at each position. Alternatively, the positions where the liquid injection ports are provided may be dispersed in places (for example, 24 places in the case of 24 layers) corresponding to the number of stacked layers in the direction along the short side of the current collector. In other words, the positions of all the liquid injection ports may be different from each other in the direction along the short side of the current collector.
　１…蓄電装置、３…バイポーラ電極、１１…集電体、１１ａ…第１面、１１ｂ…第２面、１２…正極活物質層、１２ａ…帯状部分、１３…負極活物質層、１５…溝部、３０…メッキ層、３４…突起、Ｌ１，Ｌ３…長さ。

  DESCRIPTION OF SYMBOLS 1 ... Electric storage device, 3 ... Bipolar electrode, 11 ... Current collector, 11a ... 1st surface, 11b ... 2nd surface, 12 ... Positive electrode active material layer, 12a ... Strip part, 13 ... Negative electrode active material layer, 15 ... Groove part , 30 ... Plating layer, 34 ... Protrusion, L1, L3 ... Length.

Claims (8)

  1. 　集電体と、前記集電体の第１面に設けられた正極活物質層と、前記集電体の第２面に設けられた負極活物質層と、をそれぞれ含む複数のバイポーラ電極が、セパレータを介して積層された積層体と、
    　前記積層体の側面を囲むケースと、
    　前記ケース内に封入された電解液と、
    を備え、
    　前記集電体の前記第１面は、粗面化された粗面領域を前記第１面の少なくとも一部に有し、
    　前記正極活物質層の少なくとも一部は前記粗面領域に設けられ、
    　前記正極活物質層は、前記粗面領域を露出させる溝部を有する、蓄電装置。     A plurality of bipolar electrodes each including a current collector, a positive electrode active material layer provided on the first surface of the current collector, and a negative electrode active material layer provided on the second surface of the current collector, A laminated body laminated via a separator,
    A case surrounding the side surface of the laminate,
    An electrolytic solution enclosed in the case,
    Equipped with
    The first surface of the current collector has a roughened roughened surface area on at least a part of the first surface,
    At least a part of the positive electrode active material layer is provided in the rough surface region,
    The power storage device, wherein the positive electrode active material layer has a groove portion that exposes the rough surface region.
  2. 　前記溝部は、前記正極活物質層の側端面に２つの開口を有し、前記２つの開口を連通している、請求項１に記載の蓄電装置。 The power storage device according to claim 1, wherein the groove portion has two openings on a side end surface of the positive electrode active material layer and communicates the two openings.
  3. 　前記粗面領域は、前記正極活物質層よりも広い領域であって、
    　前記正極活物質層は、前記粗面領域内に設けられる、請求項１または２に記載の蓄電装置。     The rough surface region is a region wider than the positive electrode active material layer,
    The power storage device according to claim 1, wherein the positive electrode active material layer is provided in the rough surface region.
  4. 　前記積層体の積層方向において前記正極活物質層と隣り合う前記セパレータの一部が、前記溝部に入り込んでいる、請求項１～３のいずれか一項に記載の蓄電装置。 The power storage device according to any one of claims 1 to 3, wherein a part of the separator adjacent to the positive electrode active material layer in the stacking direction of the stacked body enters the groove.
  5. 　前記溝部は、前記集電体の面内方向のうちの一方向に沿って延在しており、
    　前記正極活物質層は、前記溝部の延在方向に交差する幅方向に前記溝部を挟む一対の帯状部分を有し、
    　前記溝部の前記幅方向における長さは、前記帯状部分の前記幅方向における長さの０．０４倍以上０．８０倍以下である、請求項１～４のいずれか一項に記載の蓄電装置。     The groove portion extends along one of the in-plane directions of the current collector,
    The positive electrode active material layer has a pair of strip-shaped portions sandwiching the groove portion in a width direction intersecting the extending direction of the groove portion,
    5. The power storage device according to claim 1, wherein a length of the groove portion in the width direction is 0.04 times or more and 0.80 times or less of a length of the strip portion in the width direction. ..
  6. 前記帯状部分の前記幅方向における長さは、２５ｍｍ以上５０ｍｍ以下である、請求項５に記載の蓄電装置。 The power storage device according to claim 5, wherein a length of the strip-shaped portion in the width direction is 25 mm or more and 50 mm or less.
  7. 　前記粗面領域は、複数の突起を有するメッキ層である、請求項１～６のいずれか一項に記載の蓄電装置。 The power storage device according to any one of claims 1 to 6, wherein the rough surface area is a plating layer having a plurality of protrusions.
  8. 　前記突起は、複数の析出金属が前記積層体の積層方向に互いに積み重なった構造である、請求項７に記載の蓄電装置。 The power storage device according to claim 7, wherein the protrusion has a structure in which a plurality of deposited metals are stacked on each other in a stacking direction of the stacked body.
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