Method of manufacturing bipolar electrode

Abstract

To provide a method of manufacturing a bipolar electrode capable of satisfactorily forming a positive electrode mixture layer and a negative electrode mixture layer on both faces of an electrode foil and adjusting the positive electrode mixture layer and the negative electrode mixture layer into any densities.SOLUTION: A method of manufacturing a bipolar electrode is provided for obtaining a bipolar electrode including a positive electrode mixture layer and a negative electrode mixture layer on both faces of an electrode foil by undergoing: a positive electrode mixture coating step of coating one face of an electrode foil with a positive electrode mixture coating liquid and drying it, thereby forming a positive electrode mixture coated film; a first press step of pressing the electrode foil including the positive electrode mixture coated film; a negative electrode mixture coating step of coating the other face of the electrode foil with a negative electrode coating liquid according to a screen printing method and drying it, thereby forming a negative electrode mixture coated film; and a second press step of pressing the electrode foil including the negative electrode mixture coated film.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a method for manufacturing a bipolar electrode. [Background technology]

[0002] Conventionally, various application methods have been used as methods for applying paste when manufacturing batteries. For example, Patent Document 1 discloses a method for producing a thin battery, in which a metal mask comprises a printed pattern portion in which a paste filling window is formed and a thin mask holding portion surrounding the printed pattern portion, positioning pins are pushed into fixing pin insertion holes formed in the mask holding portion to fix the metal mask to a frame member for battery production, and at this time, a tensile force is applied to the printed pattern portion by the mask holding portion to maintain its expanded state, a sheet member having an active material filling chamber filled with a first active material is fixed to the frame member and sandwiched between an electrode plate and a separator, the metal mask and the frame member are fastened to each other so that the paste filling window is positioned on the surface of the separator, and a second electrode active material is filled into the paste filling window with a squeegee. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2003-276353 Summary of the Invention [Problem to be solved by the invention]

[0004] Conventionally, when manufacturing a bipolar electrode having a positive electrode composite layer and a negative electrode composite layer on both sides of an electrode foil, a positive electrode composite coating liquid is applied to one side of the electrode foil, and a negative electrode composite coating liquid is applied to the other side, and then the electrodes are pressed together. However, when the electrodes are pressed together after applying the positive electrode composite coating liquid and the negative electrode composite coating liquid, it is difficult to adjust the positive electrode composite layer and the negative electrode composite layer to a desired density. Therefore, a manufacturing method is desired that can adjust the positive electrode composite layer and the negative electrode composite layer to a desired density and can form the positive electrode composite layer and the negative electrode composite layer well.

[0005] The present disclosure has been made in consideration of the above circumstances, and aims to provide a method for manufacturing a bipolar electrode that can satisfactorily form a positive electrode composite layer and a negative electrode composite layer on both sides of an electrode foil, and that can adjust the density of the positive electrode composite layer and the negative electrode composite layer to any desired density. [Means for solving the problem]

[0006] Means for solving the above problems include the following aspects. <1> a positive electrode composite coating step of applying a positive electrode composite coating solution to one surface of the electrode foil and drying the solution to form a positive electrode composite coating film; a first pressing step of pressing the electrode foil having the positive electrode composite coating film; a negative electrode composite coating step of applying a negative electrode composite coating liquid to the other surface of the electrode foil by a screen printing method and drying the liquid to form a negative electrode composite coating film; a second pressing step of pressing the electrode foil having the negative electrode composite coating film; and obtaining a bipolar electrode having a positive electrode composite layer and a negative electrode composite layer on both sides of the electrode foil through the steps of: <2> The negative electrode composite coating liquid has a viscosity of 10000 mPa·s to 30000 mPa·s at a shear rate of 1 s. <1> A method for producing the bipolar electrode according to claim 1. <3> the printing pressure in the screen printing method in the negative electrode composite application step is 0.15 MPa to 0.4 MPa; <1> or <2> A method for producing the bipolar electrode according to claim 1. <4> a squeegee speed in the screen printing method in the negative electrode composite application step is 200 mm / s or less; <1> ~ <3> 10. A method for producing a bipolar electrode according to claim 9. <5> The negative electrode composite coating step includes: adsorbing a surface of the electrode foil having the positive electrode composite coating film onto a suction table; and applying the negative electrode composite coating liquid to the other surface by the screen printing method while fixing an uncoated portion of the other surface, to which the negative electrode composite coating liquid is not applied, with a jig. <1> ~ <4> 10. A method for producing a bipolar electrode according to claim 9. [Effects of the Invention]

[0007] According to the present disclosure, a method for manufacturing a bipolar electrode is provided that can satisfactorily form a positive electrode composite layer and a negative electrode composite layer on both sides of an electrode foil, and can adjust the density of the positive electrode composite layer and the negative electrode composite layer to any desired value. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 2 is a schematic perspective view showing an example of a method for applying a negative electrode composite coating liquid onto an electrode foil by screen printing. [Figure 2] 1A is a schematic top view showing an electrode foil in a state where the surface having a positive electrode composite coating film is adsorbed to an adsorption stand and the other surface of the electrode foil has an uncoated portion, to which the negative electrode composite coating solution is not applied, fixed with a jig; FIG. 1B is a schematic cross-sectional view of FIG. 1A. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, embodiments of the present disclosure will be described. These descriptions are for illustrative purposes only and are not intended to limit the scope of the present invention. In the present specification, in which numerical ranges are described in stages, the upper or lower limit value described in one numerical range may be replaced with the upper or lower limit value of another numerical range described in stages.

[0010] Each component may contain multiple types of the corresponding substance. When referring to the amount of each component in a composition, if there are multiple substances corresponding to each component in the composition, the amount refers to the total amount of those multiple substances present in the composition, unless otherwise specified. The term "process" includes not only independent processes but also processes that cannot be clearly distinguished from other processes as long as the intended effect of the process is achieved.

[0011] <Bipolar electrode manufacturing method> In the method for manufacturing a bipolar electrode according to an embodiment of the present disclosure, a bipolar electrode having a positive electrode composite layer and a negative electrode composite layer on both sides of an electrode foil is obtained through the following steps. (1) A positive electrode composite coating process in which a positive electrode composite coating solution is applied to one surface of the electrode foil and dried to form a positive electrode composite coating film. (2) a first pressing step of pressing the electrode foil having the positive electrode composite coating film; (3) a negative electrode composite coating step of applying a negative electrode composite coating solution to the other surface of the electrode foil by screen printing and drying the solution to form a negative electrode composite coating film; (4) a second pressing step of pressing the electrode foil having the negative electrode composite coating film;

[0012] According to the method for manufacturing a bipolar electrode according to an embodiment of the present disclosure, a positive electrode composite layer and a negative electrode composite layer can be formed satisfactorily on both sides of an electrode foil, and the positive electrode composite layer and the negative electrode composite layer can each be adjusted to any density.

[0013] In a conventional method for manufacturing a bipolar electrode having a positive electrode composite layer and a negative electrode composite layer on both sides of an electrode foil, a positive electrode composite coating liquid is applied to one side of the electrode foil to form a positive electrode composite coating film, and a negative electrode composite coating liquid is applied to the other side of the electrode foil to form a negative electrode composite coating film. The electrode foil having the positive electrode composite coating film and the negative electrode composite coating film is then pressed. That is, a bipolar electrode is manufactured by forming the positive electrode composite coating film and the negative electrode composite coating film, and then simultaneously pressing both coating films. However, simultaneously pressing the positive electrode composite coating film and the negative electrode composite coating film makes it difficult to adjust the densities of the positive electrode composite layer and the negative electrode composite layer to desired levels.

[0014] Therefore, in the method for manufacturing a bipolar electrode according to an embodiment of the present disclosure, a first press step is performed after forming a positive electrode composite coating film on one side of the electrode foil, and then a second press step is performed after forming a negative electrode composite coating film on the other side of the electrode foil, thereby allowing the densities of the positive electrode composite layer and the negative electrode composite layer to be adjusted separately. However, in the first press process for forming the positive electrode composite layer, the positive electrode composite layer is formed only on one side of the electrode foil, resulting in warping after pressing. Furthermore, when the positive electrode composite layer is formed on one side of the electrode foil in the first press process, so-called dents, which are marks in the shape of the positive electrode composite layer, may appear on the electrode foil. Therefore, the warping and dents cause unevenness in the electrode foil, making it difficult to apply a negative electrode composite coating solution to the other side of the electrode foil to form a negative electrode composite coating film.

[0015] Therefore, in the method for manufacturing a bipolar electrode according to an embodiment of the present disclosure, a screen printing method is used to apply the negative electrode composite coating liquid to form a negative electrode composite coating film, which improves conformability to irregularities, allowing the negative electrode composite coating liquid to be applied satisfactorily to the other surface of the electrode foil, thereby enabling a satisfactory formation of a negative electrode composite coating film. As described above, according to the embodiment of the present disclosure, a positive electrode composite layer and a negative electrode composite layer can be formed satisfactorily on both sides of the electrode foil, and the positive electrode composite layer and the negative electrode composite layer can each be adjusted to any density.

[0016] In the positive electrode composite layer of the bipolar electrode, for example, the energy density can be improved by increasing the density, while in the negative electrode composite layer, the ion diffusibility can be improved by, for example, reducing the density. According to the embodiments of the present disclosure, the densities of the positive electrode composite layer and the negative electrode composite layer can be arbitrarily adjusted even for such requirements.

[0017] Hereinafter, the manufacturing method of the bipolar electrode according to the embodiments of the present disclosure will be described for each step.

[0018] (1) Positive electrode composite coating step In the positive electrode composite coating step, a positive electrode composite coating solution is applied to one surface of the electrode foil and dried to form a positive electrode composite coating film.

[0019] · Electrode foil As the electrode foil, a conventionally known bipolar type electrode foil is used. Specifically, a laminated foil in which a positive electrode foil and a negative electrode foil are laminated can be mentioned. For the positive electrode foil in the laminated foil, a metal with good conductivity is used, for example, an aluminum foil is suitable. For the negative electrode foil, a metal with good conductivity is used, for example, a copper foil is suitable.

[0020] · Positive electrode composite coating solution The positive electrode composite coating solution contains, for example, a positive electrode active material, a binder, other components, and a solvent. Examples of the positive electrode active material include lithium nickel cobalt manganese composite oxide (hereinafter, may be simply referred to as "LNCM"). The simplest LNCM has the following general formula: LiNi x Co y Mn z O2 (where x, y, z satisfy 0 < x < 1, 0 < y < 1, 0 < z < 1, and x + y + z = 1). LNCM may contain other additive elements in addition to Li, Ni, Co, and Mn, for example, transition metal elements other than Ni, Co, and Mn, and typical metal elements other than Li. Further, examples of other positive electrode active materials include lithium nickel composite oxide, lithium cobalt composite oxide, lithium nickel manganese composite oxide, and the like.

[0021] Examples of the binder contained in the positive electrode mixture coating liquid include vinyl halide resins such as polyvinylidene fluoride (PVdF). The positive electrode mixture coating liquid may further contain other components, such as a conductive material, etc. Examples of the conductive material include non-graphitizable carbon, easily graphitizable carbon such as carbon black, and graphite.

[0022] An example of the solvent contained in the positive electrode mixture coating liquid is water.

[0023] Application and drying In the positive electrode composite coating step, the positive electrode composite coating liquid is coated on one side of the electrode foil (for example, on the aluminum foil side when a laminated foil of aluminum foil and copper foil is used), and then dried. The coating method is not particularly limited, and any conventionally known coating method can be used. The drying method is also not particularly limited, and any conventionally known drying method, such as a drying method using a drying oven, can be used.

[0024] Typically, the positive electrode composite coating liquid is applied to the electrode foil so that an uncoated portion where the positive electrode composite coating liquid is not applied is formed around the positive electrode composite coating film.

[0025] (2) First press process In the first pressing step, the electrode foil having the positive electrode composite coating film is pressed. The pressing method is not particularly limited, and any conventionally known pressing method can be used. For example, the pressing method includes a method in which the electrode foil having the positive electrode composite coating film is passed between a pair of press rolls.

[0026] (3) Negative electrode composite coating process In the negative electrode composite coating step, the negative electrode composite coating liquid is applied to the other side of the electrode foil (for example, the copper foil side when a laminated foil of aluminum foil and copper foil is used) by screen printing and dried to form a negative electrode composite coating film.

[0027] Application by screen printing A method for applying a negative electrode composite coating solution to the other surface of an electrode foil by screen printing will be described with reference to Fig. 1. Fig. 1 is a schematic perspective view showing an example of a method for applying a negative electrode composite coating solution to an electrode foil by screen printing.

[0028] As shown in FIG. 1 , the other side of electrode foil 4 is placed with its other surface facing up (up in the direction of gravity), and a screen 6 stretched within a frame 60 is placed on top of electrode foil 4. Negative electrode composite coating liquid 2 is placed on screen 6, and while a squeegee 8 is used to press the negative electrode composite coating liquid 2 against the screen 6, the squeegee 8 is moved in the direction of arrow A. The screen 6 is meshed only in the area on the electrode foil 4 where the negative electrode composite coating liquid 2 is to be applied, and the negative electrode composite coating liquid 2 passes through the holes in the mesh, thereby applying the negative electrode composite coating liquid 2 to the desired area on the electrode foil 4.

[0029] By applying the screen printing method, the conformability to the irregularities can be improved, and the negative electrode composite coating liquid can be applied well to the other surface of the electrode foil. As the screen printer to be used, for example, a commercially available screen printer may be used, and a sheet-fed type is preferable.

[0030] The viscosity of the negative electrode composite coating liquid at a shear rate of 1 s is preferably 10,000 mPa·s to 30,000 mPa·s. A viscosity of 10,000 mPa·s or higher prevents the negative electrode composite coating liquid from dripping from the screen (so-called mesh sagging). A viscosity of 30,000 mPa·s or lower prevents the negative electrode composite coating liquid, which should be applied to the electrode foil, from remaining on the screen (so-called mesh residue). The viscosity of the negative electrode composite coating liquid is measured using a viscometer at a shear rate of 1 s.

[0031] The printing pressure in the screen printing method (i.e., the pressure applied by the squeegee) is preferably 0.15 MPa to 0.4 MPa. A printing pressure of 0.15 MPa or more reduces variation in the amount of negative electrode composite coating solution that is applied onto the electrode foil through the mesh of the screen. A printing pressure of 0.4 MPa or less reduces damage to the screen.

[0032] In the screen printing method, the squeegee movement speed is preferably 200 mm / s or less. By keeping the squeegee movement speed at 200 mm / s or less, variation in the amount of negative electrode composite coating liquid applied onto the electrode foil through the mesh of the screen is suppressed. The lower limit of the movement speed may be greater than 0 mm / s.

[0033] Here, the effects of the viscosity of the negative electrode composite coating liquid, the printing pressure in the screen printing method, and the squeegee movement speed will be explained using experimental examples. In the tests shown below, as shown in Figures 2(A) and 2(B), the surface of the electrode foil having the positive electrode composite coating film was attached to an attachment table, and the uncoated portion of the other surface, where the negative electrode composite coating liquid was not applied, was fixed with a jig, and the negative electrode composite coating liquid was applied to the other surface by screen printing (details of Figures 2(A) and 2(B) will be described later).

[0034] The viscosity of the negative electrode composite coating solution was changed, and the negative electrode composite coating solution was applied to the electrode foil by screen printing. As a result, the coating was performed well in the examples with a viscosity of 10,000 mPa·s and 30,000 mPa·s, but at a viscosity of 5,000 mPa·s, mesh sagging (mesh leakage) occurred, and at a viscosity of 50,000 mPa·s, mesh residue remained.

[0035] [Table 1]

[0036] The negative electrode composite coating solution was applied to the electrode foil by screen printing while changing the printing pressure. As a result, the coating was performed well in the cases where the printing pressure was 0.15 MPa and 0.35 MPa, but at 0.06 MPa, the amount of the negative electrode composite coating solution applied to the electrode foil varied.

[0037] [Table 2]

[0038] The negative electrode composite coating solution was applied to the electrode foil by screen printing while changing the squeegee speed. As a result, the coating was performed well at speeds of 50 mm / s and 200 mm / s, but at 500 mm / s, the amount of negative electrode composite coating solution applied to the electrode foil varied.

[0039] [Table 3]

[0040] In the negative electrode composite coating step, the surface of the electrode foil having the positive electrode composite coating film is preferably attached to an attachment stand, and the negative electrode composite coating liquid is applied to the other surface by screen printing while the uncoated portion of the other surface, where the negative electrode composite coating liquid is not applied, is fixed with a jig. By attaching the electrode foil to the attachment stand and fixing the jig, the negative electrode composite coating liquid can be applied to the electrode foil more efficiently, and the negative electrode composite coating film can be more efficiently formed.

[0041] Here, a method of performing screen printing while adsorbing the surface of the electrode foil having the positive electrode composite coating film to an adsorption stand and fixing the uncoated portion of the other surface, where the negative electrode composite coating liquid is not applied, with a jig will be described with reference to FIG. 2. FIG. 2 shows the electrode foil in a state where the surface having the positive electrode composite coating film is adsorbed to an adsorption stand and the uncoated portion of the other surface, where the negative electrode composite coating liquid is not applied, is fixed with a jig. FIG. 2(A) shows a top view, and FIG. 2(B) shows a cross-sectional view. For convenience, FIGS. 2(A) and (B) show the state after the negative electrode composite coating film has been formed on the other surface.

[0042] As shown in FIGS. 2A and 2B, the electrode foil 4 is placed on the suction table 20 with one side of the electrode foil 4, i.e., the side on which the positive electrode composite coating film 12 is formed, facing the suction table 20. The electrode foil 4 is attracted to and fixed to the suction table 20 by suction through the suction holes 22 of the suction table 20. Furthermore, on the other side, i.e., the side on which the negative electrode composite coating liquid 2 is applied, an uncoated portion where the negative electrode composite coating liquid 2 is not applied is fixed with a jig 30. In FIGS. 2A and 2B, an uncoated portion exists around the area where the negative electrode composite coating liquid is applied, and the jig 30 is placed on this uncoated portion. An example of the jig 30 is a member that fixes the electrode foil 4 to the suction table 20 by magnetic force. In this case, the suction table 20 is made of a member (e.g., steel) that is attracted to each other by magnetic force.

[0043] In this way, the surface of the electrode foil 4 having the positive electrode composite coating film 12 is adsorbed onto the adsorption stand 20, and the uncoated portion of the other surface to which the negative electrode composite coating liquid 2 is not applied is fixed with a jig 30, and the negative electrode composite coating liquid 2 is applied to the other surface of the electrode foil 4 by screen printing.

[0044] Drying The drying method in the negative electrode mixture application step is not particularly limited, and a conventionally known drying method, such as a drying method using a drying oven, can be employed.

[0045] Negative electrode mixture coating liquid The negative electrode composite coating liquid contains, for example, a negative electrode active material, a binder, other components, and a solvent. Examples of the negative electrode active material include graphite-based carbon such as natural graphite, artificial graphite, and amorphous-coated graphite. Examples of the binder contained in the negative electrode composite coating liquid include rubbers such as styrene butadiene copolymer (SBR) and vinyl halide resins such as polyvinylidene fluoride (PVdF). The negative electrode composite coating liquid may further contain other components, such as a thickener. Examples of the thickener include celluloses such as carboxymethyl cellulose (CMC). Examples of the solvent contained in the negative electrode composite coating liquid include water.

[0046] (4) Second pressing process In the second pressing step, the electrode foil having the negative electrode composite coating film is pressed. As in the first pressing step, the pressing method is not particularly limited, and any conventionally known pressing method can be used. For example, a pressing method can be used in which the electrode foil having the negative electrode composite coating film is passed between a pair of press rolls. By adjusting the pressure in the first press step and the pressure in the second press step, the densities of the positive electrode composite material layer and the negative electrode composite material layer can be adjusted as desired.

[0047] A bipolar electrode is obtained through the above (1) positive electrode composite application step, (2) first pressing step, (3) negative electrode composite application step, and (4) second pressing step.

[0048] <Battery> The bipolar electrode manufactured by the bipolar electrode manufacturing method according to the embodiment of the present disclosure is used as an electrode for a bipolar battery. The bipolar battery includes a bipolar electrode, a separator, and an electrolyte. The electrolyte may be either a liquid electrolyte (i.e., an electrolytic solution) or a solid electrolyte.

[0049] Examples of applications of bipolar batteries include power sources for hybrid electric vehicles (HEVs), plug-in hybrid electric vehicles (PHEVs), and electric vehicles (BEVs). [Explanation of symbols]

[0050] 2 negative electrode composite coating solution, 4 electrode foil, 6 screen, 8 squeegee, 12 positive electrode composite coating film, 20 suction stand, 22 suction hole, 30 jig, 60 frame

Claims

1. a positive electrode composite coating step of applying a positive electrode composite coating solution to one surface of the electrode foil and drying the solution to form a positive electrode composite coating film; a first pressing step of pressing the electrode foil having the positive electrode composite coating film; a negative electrode composite coating step of applying a negative electrode composite coating liquid to the other surface of the electrode foil by a screen printing method and drying the liquid to form a negative electrode composite coating film; a second pressing step of pressing the electrode foil having the negative electrode composite coating film; and obtaining a bipolar electrode having a positive electrode composite layer and a negative electrode composite layer on both sides of the electrode foil through the steps of:

2. 2. The method for producing a bipolar electrode according to claim 1, wherein the negative electrode composite coating liquid has a viscosity of 10,000 mPa·s to 30,000 mPa·s at a shear rate of 1 s.

3. 2. The method for manufacturing a bipolar electrode according to claim 1, wherein the printing pressure in the screen printing method in the negative electrode composite application step is 0.15 MPa to 0.4 MPa.

4. 2. The method for manufacturing a bipolar electrode according to claim 1, wherein a squeegee speed in the screen printing method in the negative electrode composite coating step is 200 mm / s or less.

5. 2. The method for manufacturing a bipolar electrode according to claim 1, wherein the negative electrode composite coating step comprises: sucking a surface of the electrode foil having the positive electrode composite coating film onto a suction table; and fixing an uncoated portion of the other surface, where the negative electrode composite coating liquid is not coated, with a jig, while applying the negative electrode composite coating liquid to the other surface by the screen printing method.

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