JP2020047509A - Manufacturing method of bipolar electrode - Google Patents

Abstract

To provide a manufacturing method of a bipolar electrode capable of increasing the fluidity of an electrolyte.SOLUTION: In a positive electrode paste coating step S2, by coating a positive electrode paste 42 from below a current collecting sheet 40 with the roughened first surface 40a of the current collecting sheet 40 facing vertically downward, the irregularities on the first surface 40a are hard to be filled with a positive electrode paste 42. Therefore, a bipolar electrode 3 having a gap V between the first surface 11a of a current collector 11 and a positive electrode active material layer 12 is obtained. An electrolytic solution sealed in a power storage device 1 flows through the gap V between the first surface 11a of the current collector 11 of the bipolar electrode 3 and the positive electrode active material layer 12, thereby obtaining high fluidity.SELECTED DRAWING: Figure 4

Description

  The present invention relates to a method for manufacturing a bipolar electrode.

  Conventionally, a so-called bipolar 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 has been known. An electrolytic solution is sealed in the case of such a power storage device.

JP 2014-56799 A

  In the above-described power storage device, when the electrolytic solution is injected into the case at the manufacturing stage, or when the electrolytic solution flows from another place to a place where the electrolytic solution is consumed during use, the electrolytic solution is somewhat in the case. It needs to flow.

  However, in the bipolar type power storage device, the gap between the bipolar electrodes overlapping each other is narrow, and the area of the bipolar electrode itself (that is, the facing area between the bipolar electrodes) is relatively large in the large-capacity type. It was difficult to ensure sufficient fluidity.

  An object of the present invention is to provide a method for manufacturing a bipolar electrode that can enhance the fluidity of an electrolytic solution.

  A method for manufacturing a bipolar electrode according to one aspect of the present invention includes a current collector having a roughened first surface, a second surface opposite to the first surface, a first surface and a second surface. A method for manufacturing a bipolar electrode, comprising: a positive electrode active material layer provided on one of the surfaces; and a negative electrode active material layer provided on the other of the first and second surfaces, wherein the first surface faces vertically downward. A first coating step of applying one of a positive electrode paste for forming a positive electrode active material layer and a negative electrode paste for forming a negative electrode active material layer to the first surface from below the current collector.

  In the above-described method for manufacturing a bipolar electrode, in the first coating step, the roughened irregularities on the first surface are hard to be filled with the applied paste (a positive electrode paste or a negative electrode paste). A bipolar electrode having a gap between the layer (the positive electrode active material layer or the negative electrode active material layer) can be obtained. Since the electrolytic solution can flow through the gap between the first surface and the active material layer, the flowability of the electrolytic solution can be increased according to the method for manufacturing a bipolar electrode.

  The method for manufacturing a bipolar electrode according to another aspect further includes, before the first coating step, a second coating step of coating the second surface with the other of the positive electrode paste and the negative electrode paste. In this case, when the paste is applied to the second surface in the second application step, the paste is not applied to the first surface yet, so that compared to the case where the paste is already applied to the first surface. Therefore, the degree of freedom in the paste application conditions in the second application step is high.

  In the method for manufacturing a bipolar electrode according to another aspect, the positive electrode active material layer is provided on the first surface. The electrolytic solution is gasified and consumed particularly in the positive electrode active material layer. However, when the electrolytic solution flows through a gap between the first surface and the positive electrode active material layer, the electrolytic solution flows from another portion to the consumed portion. Is easy to flow.

  According to the present invention, there is provided a method of manufacturing a bipolar electrode capable of increasing the fluidity of an electrolytic solution.

FIG. 1 is a cross-sectional view illustrating a power storage device according to one embodiment. FIG. 2 is an enlarged view of a main part of the current collector of the bipolar electrode shown in FIG. FIG. 3 is a flowchart showing a method for manufacturing the bipolar electrode shown in FIG. FIG. 4 is a diagram showing each step of the flow chart shown in FIG. FIG. 5 is an enlarged view of a main part showing the current collector sheet after the positive electrode paste application step in the flow chart shown in FIG.

Hereinafter, an embodiment of the present invention 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 characters, without redundant description.
FIG. 1 is a cross-sectional view schematically illustrating a power storage device according to one embodiment. Power storage device 1 is, for example, a secondary battery such as a nickel hydride secondary battery or a lithium ion secondary battery, or an electric double layer capacitor. The power storage device 1 can be used, for example, as a battery of various vehicles such as a forklift, a hybrid vehicle, and an electric vehicle. Hereinafter, a case where power storage device 1 is a nickel-metal hydride secondary battery will be described as an example.

  Power storage device 1 is a bipolar battery including stacked body 2 of bipolar electrodes 3. The power storage device 1 includes a stacked body 2 of bipolar electrodes 3, a case 5 for holding the stacked body 2, and a restraining body 6 for restraining the stacked body 2.

  The laminate 2 is configured by laminating a plurality of individual bipolar electrodes 3 along a first direction D1 with a separator 7 interposed therebetween. 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 distant from a terminal member 25 described later is used as a reference, another bipolar electrode 3 is provided above and below the bipolar electrode 3 with a separator 7 interposed therebetween. Each of the bipolar electrodes 3 includes a current collector 11, a positive electrode active material layer 12 provided on a first surface 11 a of the current collector 11, and a positive electrode active material layer 12 on a side opposite to the first surface 11 a in a thickness direction of the current collector 11. And a negative electrode active material layer 13 provided on a certain second surface 11b. In the laminate 2, the positive electrode active material layer 12 of one bipolar electrode 3 faces the negative electrode active material layer 13 of one adjacent bipolar electrode 3 in the first direction D <b> 1, and the negative electrode active material layer of one bipolar electrode 3 Reference numeral 13 faces the positive electrode active material layer 12 of the other bipolar electrode adjacent in the first direction D1.

  As a positive electrode active material constituting the positive electrode active material layer 12, for example, nickel hydroxide is given. Examples of the negative electrode active material constituting the negative electrode active material layer 13 include a hydrogen storage alloy. The formation region of the negative electrode active material layer 13 on the second surface 11b of the current collector 11 may be slightly larger than the formation region of the positive electrode active material layer 12 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 applied. The case 5 holds the peripheral portion 11c while being buried in the inner wall 5a of the case 5. A resin spacer 4 is interposed between the first surface 11a of the peripheral portion 11c and the inner wall 5a along the peripheral portion 11c in a state of being in contact therewith. The resin spacer 4 keeps an interval between the adjacent bipolar electrodes 3. As a result, the current collectors 11, 11 and the inner wall 5a of the case 5 cooperate to form a space between the current collectors 11, 11 adjacent in the first direction D1. The space accommodates an electrolytic solution (not shown) made of an alkaline solution such as an aqueous potassium hydroxide solution. The space for accommodating the electrolytic solution formed between the bipolar electrodes 3 adjacent to each other in the first direction D1 is liquid-tightly separated (sealed) by the resin spacer 4. The resin spacer 4 is formed, for example, by curing a resin disposed on the peripheral portion 11c. The resin before curing may be in a liquid state, a sheet state, or a gel state.

  A current collector 11 </ b> A having only one negative electrode active material layer 13 on one surface is stacked on one end of the stacked body 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. Further, a current collector 11B provided with only the positive electrode active material layer 12 is stacked on the other end (the negative direction in the Z-axis direction) of the stack 2. The current collector 11B is arranged so 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 edges of the current collectors 11 </ b> A and 11 </ b> B are held in the case 5 while being buried in the inner wall 5 a of the case 5, similarly to the current collector 11 of the bipolar electrode 3. A 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, an insulator formed in a sheet shape. 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 nonwoven fabric made of polypropylene or the like. Further, the separator 7 may be reinforced with a vinylidene fluoride resin compound or the like. Note that the separator 7 is not limited to a sheet shape, and a bag-shaped insulator may be used.

  The case 5 is formed in a rectangular cylindrical shape by, for example, injection molding using an insulating resin. Examples of the resin material constituting the resin case 5 include polypropylene (PP), polyphenylene sulfide (PPS), modified polyphenylene ether (modified PPE), and modified polyphenylene sulfide (modified PPS). 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.

  The restricting body 6 includes a pair of restricting plates 21 and 21 and a connecting member (a bolt 22 and a nut 23) that connects the restricting plates 21 and 21 to each other. The constraining plate 21 is formed in a flat plate shape from a metal such as iron, for example. The edge of the restraining plate 21 protruding outside 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 seat surface of the restraining body 6 are insulated. Terminal members 25 (negative electrode terminal members 25A and positive electrode terminal members 25B) are coupled to one surface side of the constraining plate 21 via an insulating member 24. As a material for forming the insulating member 24 interposed between the constraint plate 21 and the terminal member 25, for example, a fluorine-based resin or a polyethylene resin is used.

  One constraint plate 21 is located on one side of the case 5 in the first direction D1. One restraining plate 21 is abutted against one end surface of the case 5 such that the negative electrode terminal member 25A and the current collector 11A abut on the inside of the case 5. The other restraining plate 21 is located on the other side of the case 5 in the first direction D1. The other restraining plate 21 is abutted against the other end surface of the case 5 such that the positive electrode terminal member 25B and the current collector 11B abut inside the case 5. The bolt 22 is passed through the insertion hole 21 a from, for example, one constraint plate 21 side to the other constraint plate 21 side, and a nut 23 is screwed into a tip of the bolt 22 protruding from the other constraint plate 21. I have.

  As a result, the stacked body 2, the current collectors 11A and 11B, and the case 5 are sandwiched to form a unit, and a restrained load is applied to the stacked body 2 along the first direction D1. Further, the negative electrode terminal member 25A is disposed between one of the constraint plates 21 and the laminate 2, and the positive electrode terminal member 25B is disposed between the other constraint plate 21 and the laminate 2. The lead portion 26 is connected to the negative electrode terminal member 25A. The lead portion 27 is connected to the positive electrode terminal member 25B. The power storage device 1 can be charged and discharged by the extraction unit 26 and the extraction unit 27.

  Hereinafter, the current collector 11 will be described with reference to FIG.

  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 11a is the surface of the plating layer 30, and the second surface 11b is the surface of the steel plate 10. By subjecting the first surface 11a to a roughening treatment, the first surface 11a has a larger surface roughness (arithmetic average roughness Ra) than the one surface 10a and the second surface 11b which are the natural surfaces of the steel plate 10. . Known surface treatments such as chemical treatments such as etching and plating, physical treatments such as sputtering, and mechanical treatments such as polishing can be applied as the surface roughening treatment. In the present embodiment, the plating layer 30 having the first surface 11a roughened by the electrolytic nickel plating process is formed. The second surface 11b is a natural surface of the steel sheet 10, that is, a non-rough 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 include a cold-rolled steel sheet (such as SPCC) specified in JIS G 3141: 2005. The thickness of the current collector 11 is, for example, 0.1 μm or more and 1000 μm or less, and is, for example, 50 μm. The plating layer 30 is formed by electrolytic nickel plating. The thickness of the plating layer 30 can be designed to be, for example, not less than 5 μm and not more than 20 μm.

  As shown in FIGS. 2A and 2B, the plating layer 30 includes a base nickel plating layer 31 provided on one 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 present nickel plating layer 32 are formed by performing electrolytic plating under different conditions.

  The base nickel plating layer 31 is an electrolytic plating layer provided on one surface 10a of the steel sheet 10 along a second direction D2 intersecting the first direction D1. The second direction D2 corresponds to a direction along the XY plane or an extending direction of one surface 10a. Therefore, the second direction D2 does not necessarily have to be orthogonal to the first direction D1. The thickness of base nickel plating layer 31 is, for example, 0.5 μm or more and 2 μm or less. It is preferable that base nickel plating layer 31 covers all of one surface 10a of steel plate 10. In this case, since it is difficult to form a pinhole or the like in the plating layer 30, the occurrence of a leak current can be suppressed. The surface shape of the base nickel plating layer 31 is different from the shape of one surface 10a. Specifically, the base nickel plating layer 31 has a plurality of protrusions 33 protruding along the first direction D1. For this reason, the surface shape of the base nickel plating layer 31 is not along the one 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 one surface 10a of the steel plate 10. Has become. Therefore, the base nickel plating layer 31 is provided so as to be different 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 protrusions 33 are provided irregularly along the second direction D2. When the thickness of the base nickel plating layer 31 is about 1 μm or more, the average height of the protrusions 33 is, for example, 0.4 μm or more and half or less of the thickness of the base nickel plating layer 31. Good. In this case, the shape of the nickel plating layer 32 can be made good. The average height of the protrusions 33 is measured by using, for example, a microscope using a laser confocal optical system.

  The nickel plating layer 32 is an electrolytic plating layer provided with the base nickel plating layer 31 as a film formation surface, and has a surface roughness greater than that of the base nickel plating layer 31. Each of the surface roughness of the base nickel plating layer 31 and the present nickel plating layer 32 is represented by an arithmetic average roughness Ra specified 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, and is 1.5 times or more and 60.0 times or less of the base 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 and the like in the plating layer 30. The thickness of the nickel plating layer 32 is, for example, not less than 5 μm and not more than 20 μm. The nickel plating layer 32 does not necessarily need to be formed so as to cover the entire surface of the base nickel plating layer 31. For example, the nickel plating layer 32 may be an aggregate of a plurality of protrusions 34 projecting from the base nickel plating layer 31 in the first direction D1. In this case, the nickel plating layer 32 is also called a roughened plating layer. Each of the plurality of protrusions 34 is formed so as to reach a distal end 34b along the first direction D1 with a portion contacting the corresponding convex portion 33 as a base end 34a.

  A plurality of nickel crystals having, for example, a substantially spherical shape are superimposed on at least a part of the plurality of protrusions 34. These nickel crystals are a plurality of deposited metals (substances) formed by electrolytic plating. When such deposited metals overlap with each other, an enlarged portion 34c is formed in which the length of the projection 34 in the second direction D2 is larger than the length of the base end 34a in the second direction D2. That is, at least a portion of the projection 34 has a tapered shape in which the tapered shape is tapered from the base end 34a side toward the distal end 34b side. The position of the enlarged portion 34c in the projection 34 does not necessarily have to be the distal end 34b, but is located at least on the distal end 34b side than the proximal end 34a. In other words, in the protrusion 34 having the tapered shape, the portion having the largest length dimension in the second direction D2 may not be the distal end 34b, but is located other than the proximal 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 projections 34 is, for example, 30 μm or less. When the average height of the projections 34 is 30 μm or less, breakage of the projections 34 can be favorably suppressed. The average height of the projections 34 is measured using, for example, a microscope using a laser confocal optical system.

In a plan view (that is, when viewed along the first direction D1), the number of protrusions 34 per unit area of the nickel plating layer 32 is, for example, 2,500 or more and 7,000 or less. When the number of the protrusions 34 is 2,500 or more, the surface area of the nickel plating layer 32 can be sufficiently ensured. When the number of the protrusions 34 is 7,000 or less, contact between adjacent protrusions 34 can be suppressed. In the present embodiment, the unit area is 1 mm ² . The number of the projections 34 per unit area of the nickel plating layer 32 is calculated by, for example, an average length RSm of a roughness curve element specified in JIS B 0601: 2013 (or ISO 4287: 1997, Amd. 1: 2009). Is done.

  The current collectors 11A and 11B may be a steel plate subjected to electrolytic plating similarly to the current collector 11, or may be a metal foil such as a nickel foil.

  The above-described plating layer 30 can be formed, for example, by the following procedure.

  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, 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 containing a nickel cation, such as a nickel chloride solution or a 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, a plating layer can be efficiently formed. When the temperature of the nickel bath is 40 ° C. or more and 65 ° C. or less, the average height of the protrusions 33 provided on the base nickel plating layer 31 can be controlled well.

When the electrolytic plating for forming the base nickel plating layer 31 is performed, for example, when the current density is 0.5 A / dm ² or more and 5.0 A / dm ² or less, for 150 seconds or more and 2,400 seconds or less. Then, the steel sheet 10 is immersed in a nickel bath. By setting the current density during electrolytic plating to be 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 protrusions 33 formed on the base nickel plating layer 31 from exhibiting a needle shape (or a whisker shape). Also, by dipping 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 set well.

  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 during which the steel sheet 10 is immersed need not necessarily be within the above ranges.

  Next, the present nickel plating layer 32 (see FIG. 2B) including the plurality of protrusions 34 and having a surface roughness greater than that of the base nickel plating layer 31 is formed on the base nickel plating layer 31. Thus, the current collector 11 including the steel plate 10 and the plating layer 30 having the base nickel plating layer 31 and the present nickel plating layer 32 is obtained. The nickel plating layer 32 is formed by subjecting the steel sheet 10 on which the base nickel plating layer 31 is formed to electrolytic plating. In this electrolytic plating, 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 bath is an electrolytic solution containing nickel sulfate, nickel chloride, and boric acid as main components. When the nickel concentration of the Watt bath is 0.15 mol / L or more and less than 0.30 mol / L, the projection 34 having a tapered shape can be formed favorably. Further, when the temperature of the Watt bath is 30 ° C. or more and 60 ° C. or less, the average height of the tapered shape can be controlled well.

In practicing the electrolytic plating 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 nickel bath Soak in By setting the current density in the electrolytic plating 30A / dm ² or more 50A / dm ² or less, it can be favorably formed a projection 34 which exhibits thickens shape. Further, by immersing the steel sheet 10 in the Watt bath for 30 seconds or more and 60 seconds or less, the thickness of the nickel plating layer 32 can be set well.

  Conditions that are particularly important when forming the present nickel plating layer 32 are the nickel concentration and the current density of the watt bath. Therefore, when both the nickel concentration and the current density of the watt bath are within the above ranges, the temperature of the watt bath and the time during which the steel sheet 10 is immersed need not necessarily be within the above ranges.

  Subsequently, a method for manufacturing the above-described bipolar electrode 3 will be described with reference to FIGS.

  In the manufacturing method of the bipolar electrode 3, a negative electrode paste 41 including a negative electrode active material and a positive electrode paste 42 including a positive electrode active material are applied to the current collecting sheet 40 while conveying the current collecting sheet 40 to be the current collector 11. .

  The current collector sheet 40 has a first surface 40a corresponding to the first surface 11a of the current collector 11, and a second surface 40b corresponding to the second surface 11b of the current collector 11. The first surface 40a of the current collector sheet 40 corresponding to the first surface 11a of the current collector 11 is roughened and provided with the protrusions 34 of the plating layer 30 described above.

  As shown in FIG. 4, the current collecting sheet 40 is transported in a horizontal direction by predetermined transport rollers R1 and R2. At this time, the first surface 40a of the current collecting sheet 40 faces vertically downward, and the second surface 40b faces vertically upward.

  When the bipolar electrode 3 is manufactured, as shown in FIG. 4A, a second surface 40b, which is the upper surface of the current collecting sheet 40, is used as a negative electrode paste coating step (second coating step) S1 in FIG. A negative electrode paste 41 is applied thereon. In the negative electrode paste coating step S1, a die coater 50 disposed above the current collecting sheet 40 is used. In the negative electrode paste coating step S1, since the positive electrode paste 42 has not yet been coated on the first surface 40a, which is the lower surface of the current collecting sheet 40, the lower transport roller R2 is located at a position facing the die coater 50. It is possible to arrange. By disposing the lower transport roller R2 at a position facing the die coater 50, the bending of the current collecting sheet 40 during coating is suppressed, so that the negative electrode paste can be coated with high positional accuracy and dimensional accuracy. .

  The current collecting sheet 40 has a large thickness dimension so as not to bend during transportation and coating. The current collecting sheet 40 has a thickness similar to the thickness of the current collector 11 (that is, 50 μm). In addition, the current collecting sheet 40 can be held at a high tension of 100 N / m or more so as not to bend during transportation and coating.

  Following the negative electrode paste application step S1, as shown in FIG. 4B, the positive electrode paste application step (first application step) S2 on the first surface 40a of the current collector sheet 40 is performed as a positive electrode paste application step (first application step). The paste 42 is applied. In the positive electrode paste coating step S2, a die coater 52 disposed below the current collecting sheet 40 is used.

  In the positive electrode paste coating step S2, by applying the positive electrode paste 42 from below the current collecting sheet 40, a configuration as shown in FIG. 5 can be obtained. In FIG. 5, reference numeral 42a indicates a positive electrode active material included in the positive electrode paste 42, and reference numeral 41a indicates a negative electrode active material included in the negative electrode paste 41. As shown in FIG. 5, the positive electrode paste 42 adheres to the first surface 40 a of the current collector sheet 40, but the positive electrode active material 42 a and the solvent contained in the positive electrode paste 42 include the plurality of protrusions 34 provided on the first surface 40 a. Do not fill the gap. Further, due to the presence of the plurality of protrusions 34, the positive electrode paste 42 and the first surface 40a do not completely adhere to each other, and a gap V is formed between the positive electrode paste 42 and the first surface 40a. The positive electrode active material 42 a is electrically connected to the current collecting sheet 40 via the protrusion 34. On the other hand, since the negative electrode paste 41 is applied from the upper side to the second surface 40b of the current collecting sheet 40 that is not roughened, the negative electrode paste 41 is completely adhered to the second surface 40b, and the negative electrode paste 41 and the second surface 40b are No substantial gap is formed between them.

  After the positive electrode paste application step S2, the negative electrode paste 41 and the positive electrode paste 42 are dried under predetermined drying conditions as a drying step S3 in FIG. In the drying step S3, the solvent is removed from the positive electrode paste 42 to form the positive electrode active material layer 12, and the solvent is removed from the negative electrode paste 41 to form the negative electrode active material layer 13.

  Finally, as a cutting step S4 in FIG. 3, as shown in FIG. 4 (c), the bipolar electrode 3 formed in a strip shape is cut or punched to a predetermined size to form the bipolar electrode 3 as an individual piece.

  As described above, in the method of manufacturing the bipolar electrode 3, in the positive electrode paste coating step S2, the positive electrode paste 42 is placed on the lower side of the current collector sheet 40 with the first surface 40a of the current collector sheet 40 facing vertically downward. As a result, the unevenness of the first surface 40a (that is, the gap defined by the plurality of protrusions 34) is not easily filled with the positive electrode paste 42. Therefore, according to the above-described method for manufacturing bipolar electrode 3, bipolar electrode 3 in which gap V exists between first surface 11 a of current collector 11 and positive electrode active material layer 12 can be obtained.

  In the power storage device 1, an electrolyte is injected between a plurality of bipolar electrodes 3 constituting the stacked body 2 in a manufacturing stage. In addition, in the power storage device 1, particularly in the positive electrode active material layer 12, the electrolytic solution may be gasified and the electrolytic solution may be consumed, so that the electrolytic solution flows into the consumed portion from another location. In such a case, the electrolyte needs to flow to some extent. If the electrolyte does not sufficiently flow into the portion where the electrolyte has been consumed due to the low fluidity of the electrolyte, the battery characteristics may be deteriorated.

  The electrolytic solution sealed in power storage device 1 can flow through gap V between first surface 11 a of current collector 11 of bipolar electrode 3 and positive electrode active material layer 12. The electrolyte can flow due to the capillary phenomenon even if the size of the gap V is small. Therefore, according to the manufacturing method of the bipolar electrode 3 described above, the fluidity of the electrolytic solution can be increased.

  In the above-described method for manufacturing the bipolar electrode 3, when the negative electrode paste 41 is applied to the current collecting sheet 40, the positive electrode paste 42 has not been applied yet. Therefore, when applying the negative electrode paste 41 to the current collecting sheet 40, the degree of freedom of the application conditions of the negative electrode paste 41 is higher than when the positive electrode paste 42 is already applied. For example, it is possible to dispose the lower conveying roller R2 at a position facing the die coater 50 of the negative electrode paste 41. In this case, since the bending of the current collecting sheet 40 during coating is suppressed, the negative electrode paste needs to be high. Coating can be performed with positional accuracy and dimensional accuracy.

  The present invention is not limited to the above embodiment, and various other modifications are possible. For example, in the above embodiment, the positive electrode active material layer 12 is provided on the roughened first surface 11a, but the negative electrode active material layer 13 may be provided on the roughened first surface 11a. . That is, the first application step may be a negative electrode paste application step, and the second application step may be a positive electrode paste application step. In addition, although the aspect in which only the first surface of the current collector and the current collecting sheet are subjected to the surface roughening treatment is shown, both the first surface and the second surface are subjected to the surface roughening treatment. You may.

  DESCRIPTION OF SYMBOLS 1 ... Power storage device, 3 ... Bipolar electrode, 11 ... Current collector, 11a ... 1st surface, 11b ... 2nd surface, 12 ... Positive electrode active material layer, 13 ... Negative electrode active material layer, 30 ... Plating layer, 34 ... Projection , 40: current collector sheet, 40a: first surface, 40b: second surface, S1: negative electrode paste application step, S2: positive electrode paste application step.

Claims (3)

A current collector having a roughened first surface, a second surface opposite to the first surface, and a positive electrode active material layer provided on one of the first and second surfaces. A method of manufacturing a bipolar electrode, comprising: a negative electrode active material layer provided on the other of the first surface and the second surface;
With the first surface facing vertically downward, one of the positive electrode paste forming the positive electrode active material layer and the negative electrode paste forming the negative electrode active material layer is placed on the first surface under the current collector. A method for producing a bipolar electrode, comprising a first coating step of coating from a surface.   The method for manufacturing a bipolar electrode according to claim 1, further comprising a second coating step of coating the other of the positive electrode paste and the negative electrode paste on the second surface before the first coating step. The method for manufacturing a bipolar electrode according to claim 1, wherein the positive electrode active material layer is provided on the first surface.

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