Manufacturing method of electrode sheet

Abstract

To improve adhesion between active material layers while maintaining a target layer ratio.SOLUTION: A manufacturing method of a negative electrode sheet 20, includes: an upper layer slurry wettability calculation step of calculating wettability of an upper layer slurry 24A on the basis of a viscosity of the upper layer slurry 24A forming a negative electrode active material layer 22 arranged to an upper layer; a plasma processing step of executing plasma processing to the negative electrode material of a lower layer slurry 23A so that the lower layer slurry 23A forming the negative electrode active material layer 22 arranged to a lower layer has target wettability with the viscosity that is higher than the upper layer slurry 24A on the basis of the wettability of the upper layer slurry 24A; and a superposition coating step of executing superposition coating by the lower layer slurry 23A containing the negative electrode active material to which the plasma processing is executed, and the upper layer slurry 24A.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present invention relates to a method for producing an electrode sheet. [Background technology]

[0002] It is known that an electrode sheet has two active material layers (see, for example, Patent Document 1).

[0003] Patent Document 1 discloses a positive electrode for a lithium secondary battery, which is formed by laminating, on a current collector, a lower layer containing an active material capable of absorbing and releasing lithium ions and a binder, and an upper layer containing a material capable of physically absorbing and desorbing lithium ions on its surface and capable of forming an electric double layer and a binder.

[0004] In an electrode sheet having a plurality of active material layers, it is preferable to improve the adhesion between the active material layers while maintaining a target layer ratio. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2008-34215 A Summary of the Invention [Problem to be solved by the invention]

[0006] In consideration of the above, an object of the present invention is to improve the adhesion between active material layers while maintaining a target layer ratio. [Means for solving the problem]

[0007] The manufacturing method of an electrode sheet according to the first aspect of the present invention includes an upper layer slurry wettability calculation step of calculating the wettability of an upper layer slurry based on the viscosity of an upper layer slurry that forms an active material layer to be placed in an upper layer, a functional group introduction treatment step of performing a functional group introduction treatment on the active material of the lower layer slurry so that a lower layer slurry that forms an active material layer to be placed in a lower layer has a target wettability of a higher viscosity than the upper layer slurry based on the wettability of the upper layer slurry, and a multilayer coating step of performing a multilayer coating using the lower layer slurry containing the active material that has been subjected to the functional group introduction treatment and the upper layer slurry.

[0008] The electrode sheet manufacturing method of the second aspect of the present invention includes the electrode sheet manufacturing method of the first aspect of the present invention, and further includes a lower layer slurry wettability determination step of determining a target wettability of the lower layer slurry, which is higher in viscosity than the upper layer slurry, based on the wettability of the upper layer slurry, a gap calculation step of calculating a gap between a target wettability of the active material of the lower layer slurry calculated based on the target wettability of the lower layer slurry and an actually measured wettability of the active material of the lower layer slurry, and a functional group introduction treatment condition determination step of determining functional group introduction treatment conditions for the active material of the lower layer slurry based on the gap.

[0009] A third aspect of the present invention is a method for manufacturing an electrode sheet according to the second aspect of the present invention, wherein in the lower layer slurry wettability determination step, the wettability of the lower layer slurry is determined based on a relational equation between the wettability of the upper layer slurry and the lower layer slurry and the viscosity of the upper layer slurry and the lower layer slurry, which has been previously obtained.

[0010] In a fourth aspect of the present invention, the electrode sheet manufacturing method is the electrode sheet manufacturing method of the second or third aspect of the present invention, and in the gap calculation step, the gap is calculated based on a relational equation between the wettability of the lower layer slurry and the wettability of the active material of the lower layer slurry, which has been obtained in advance.

[0011] A fifth aspect of the present invention is a method for manufacturing an electrode sheet according to any one of the second to fourth aspects of the present invention, and in the functional group introduction treatment condition determination step, the functional group introduction treatment conditions are determined based on a relational equation between the wettability of the active material of the lower layer slurry and the functional group introduction treatment conditions, which has been previously obtained. Effect of the Invention

[0012] In the manufacturing method of the electrode sheet of the first aspect of the present invention, a functional group introduction treatment is performed on the active material of the lower layer slurry so that the lower layer slurry has a target wettability of a higher viscosity than the upper layer slurry based on the wettability of the upper layer slurry, and multi-layer coating is performed with the lower layer slurry containing the active material that has been subjected to the functional group introduction treatment and the upper layer slurry, so that the lower layer slurry has a higher viscosity than the upper layer slurry and the lower layer slurry has a target wettability. Therefore, the active material layer can be coated with a target layer ratio, and the wettability of the lower layer slurry can be made close to that of the upper layer slurry. As a result, the adhesion between the active material layers can be improved while maintaining the target layer ratio.

[0013] In the manufacturing method of the electrode sheet according to the second aspect of the present invention, the gap between the target wettability of the active material of the lower layer slurry calculated based on the target wettability of the lower layer slurry and the measured wettability of the active material of the lower layer slurry is calculated, and the functional group introduction treatment conditions of the active material of the lower layer slurry are determined based on the gap, so that the active material of the lower layer slurry has the target wettability. Therefore, the lower layer slurry has the target wettability. As a result, the adhesion between the active material layers can be improved by a simple method.

[0014] In the electrode sheet manufacturing method according to the third aspect of the present invention, the wettability of the lower layer slurry is determined in the lower layer slurry wettability determination step based on a relational expression between the wettability of the upper layer slurry and the lower layer slurry and the viscosity of the upper layer slurry and the lower layer slurry, which is previously obtained, thereby determining the wettability of the lower layer slurry in a simple manner. Therefore, the adhesion between the active material layers can be improved in a simple manner.

[0015] In the electrode sheet manufacturing method according to the fourth aspect of the present invention, the gap is calculated in a simple manner in the gap calculation step by calculating the gap based on a previously obtained relational expression between the wettability of the lower layer slurry and the wettability of the active material of the lower layer slurry, thereby making it possible to improve the adhesion between the active material layers in a simple manner.

[0016] In the electrode sheet manufacturing method according to the fifth aspect of the present invention, in the functional group introduction treatment condition determination step, the functional group introduction treatment conditions are determined based on a previously obtained relational expression between the wettability of the active material of the lower layer slurry and the functional group introduction treatment conditions, thereby allowing the functional group introduction treatment conditions to be determined in a simple manner, thereby improving the adhesion between the active material layers in a simple manner. [Brief description of the drawings]

[0017] [Figure 1] FIG. 2 is a perspective view showing a partially developed state of the wound body according to the embodiment. [Diagram 2] 2 is a cross-sectional view showing a schematic view of a wound body according to the embodiment, showing a cross section taken along line SS in FIG. 1. [Diagram 3] FIG. 2 is a configuration diagram that illustrates a configuration of an electrode sheet manufacturing device according to an embodiment. [Figure 4] 4 is a flowchart showing a manufacturing procedure of the electrode sheet according to the embodiment. [Diagram 5] 1 is a graph showing the relationship between slurry viscosity and slurry wettability. [Figure 6] 1 is a graph showing the relationship between the wettability of a lower layer negative electrode active material and the wettability of a lower layer slurry. [Figure 7] 1 is a graph showing the relationship between the wettability of a lower-layer negative electrode active material and plasma treatment time. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] Hereinafter, an electrode assembly according to an embodiment will be described with reference to the drawings. A wound body 10 as an electrode assembly according to an embodiment is provided in a lithium ion secondary battery and is used, for example, as an on-board power source for electric vehicles, hybrid vehicles, and the like. In each drawing, an arrow D indicates the width direction D of the wound body 10, and an arrow R indicates the conveying direction R by the conveying unit.

[0019] [Configuration of winding body 10] As shown in FIG. 1, the wound body 10 has a power generating section 11, a negative electrode current collecting section 12, and a positive electrode current collecting section 13.

[0020] As shown in FIGS. 1 and 2, the wound body 10 is formed in a flat shape by winding a negative electrode sheet (an example of an electrode sheet) 20, a positive electrode sheet (an example of an electrode sheet) 30, and two separators 25 in a stacked state.

[0021] The power generation section 11 is formed by laminating an area of ​​the positive electrode sheet 30 where a positive electrode active material (an example of an active material) is applied, an area of ​​the negative electrode sheet 20 where a negative electrode active material (an example of an active material) is applied, and a separator 25.

[0022] The power generating section 11 has a function of storing electric energy. The negative electrode current collecting section 12 is not coated with a negative electrode active material, and is formed by winding a negative electrode sheet 20. The positive electrode current collecting section 13 is not coated with a positive electrode active material, and is formed by winding a positive electrode sheet 30.

[0023] 2, the negative electrode sheet 20 has a long strip-shaped negative electrode current collector sheet (an example of a current collector sheet) 21 coated with a negative electrode active material on both sides thereof to form a negative electrode active material layer (an example of an active material layer) 22. The negative electrode active material layer 22 is formed in two layers, a lower-layer negative electrode active material layer 23 disposed in the lower layer, and an upper-layer negative electrode active material layer 24 disposed in the upper layer of the lower-layer negative electrode active material layer 23. The other end side in the width direction D of the negative electrode sheet 20 is not coated with a negative electrode active material, and the negative electrode current collector sheet 21 is exposed.

[0024] The positive electrode sheet 30 has a positive electrode active material applied to both sides of a long strip-shaped positive electrode current collector sheet (an example of a current collector sheet) 31 to form a positive electrode active material layer (an example of an active material layer) 32. The positive electrode active material layer 32 is formed in two layers, a lower layer positive electrode active material layer 33 disposed in the lower layer, and an upper layer positive electrode active material layer 34 disposed in the upper layer of the lower layer positive electrode active material layer 33. At one end side in the width direction D of the positive electrode sheet 30, the positive electrode active material is not applied, and the positive electrode current collector sheet 31 is exposed.

[0025] The separator 25 is formed of an insulating material such as polypropylene, polyethylene, etc. The separator 25 is disposed between the positive electrode sheet 30 and the negative electrode sheet 20, and insulates the positive electrode sheet 30 from the negative electrode sheet 20.

[0026] The wound body 10 is housed in a case (not shown) together with an electrolyte, and the output of the wound body 10 is taken out from an external terminal (not shown) and used as a power source for electric vehicles, hybrid vehicles, and the like.

[0027] [Configuration of electrode sheet manufacturing equipment] A method for forming the lower negative electrode active material layer 23 and the upper negative electrode active material layer 24 on the upper surface of the negative electrode current collector sheet 21 will be described below.

[0028] As shown in FIG. 3, the manufacturing apparatus 100 includes a transfer section 90, a first slurry supplying apparatus 40, and a second slurry supplying apparatus 50.

[0029] In the transport path of the transport section 90, a first slurry supplying device 40 and a second slurry supplying device 50 are arranged in sequence from the upstream side to the downstream side in the transport direction R.

[0030] The transport unit 90 includes, for example, a drive roller 91 and a driven roller 92. The negative electrode current collector sheet 21 moves in a transport direction R as the drive roller 91 is driven.

[0031] The first slurry supplying device 40 includes a storage section 40A and a slurry supplying section 41. The storage section 40A stores a lower layer slurry 23A that forms the lower layer negative electrode active material layer 23. The lower layer slurry 23A may be, for example, a slurry composed of natural graphite, CMC (carboxymethyl cellulose), and SBR (styrene butadiene rubber). The lower layer slurry 23A stored in the storage section 40A is supplied from the slurry supplying section 41 to the negative electrode current collecting sheet 21 moving in the transport direction R.

[0032] The second slurry supplying device 50 includes a storage section 50A and a slurry supplying section 51. The storage section 50A stores an upper layer slurry 24A that forms the upper layer negative electrode active material layer 24. The upper layer slurry 24A may be, for example, a slurry composed of natural graphite, CMC (carboxymethyl cellulose), and SBR (styrene butadiene rubber). The upper layer slurry 24A stored in the storage section 50A is supplied from the slurry supplying section 51 to the negative electrode current collecting sheet 21 moving in the conveying direction R.

[0033] [Operation of electrode sheet manufacturing equipment] 3, when the drive roller 91 is driven, the negative electrode current collector sheet 21 moves in the transport direction R. Next, a lower-layer slurry 23A is supplied from a first slurry supplying device 40 to the upper surface of the negative electrode current collector sheet 21, and an upper-layer slurry 24A is supplied from a second slurry supplying device 50 to the upper surface of the lower-layer negative electrode active material layer 23. As a result, the lower-layer negative electrode active material layer 23 and the upper-layer negative electrode active material layer 24 are formed on the negative electrode current collector sheet 21.

[0034] [Electrode sheet manufacturing procedure] The procedure for forming the lower negative electrode active material layer 23 and the upper negative electrode active material layer 24 on the upper surface of the negative electrode current collector sheet 21 will be described below.

[0035] (Upper layer slurry viscosity confirmation process) 4, in the upper layer slurry viscosity confirmation step, the viscosity of upper layer slurry 24A forming upper layer negative electrode active material layer 24 is confirmed (measured) (Step S101). A viscometer can be used to confirm the viscosity.

[0036] (Upper layer slurry wettability calculation process) In the upper layer slurry wettability calculation step, the wettability of the upper layer slurry 24A is calculated based on the viscosity of the upper layer slurry 24A (step S102). Specifically, as shown in Fig. 5, the wettability of the upper layer slurry 24A is calculated based on a relational expression derived from a graph showing the relationship between the wettability of the upper layer slurry 24A previously acquired and the viscosity of the upper layer slurry 24A.

[0037] Here, the wettability of the slurry can be obtained, for example, by measuring the absorbance when the slurry is dissolved (stirred) in water and allowed to stand for a certain period of time, the zeta potential of the slurry, the contact angle of the slurry, etc.

[0038] (Lower layer slurry wettability determination process) In the lower-layer slurry wettability determination step, the wettability of the lower-layer slurry 23A is determined based on the wettability of the upper-layer slurry 24A so that the lower-layer slurry 23A forming the lower-layer negative electrode active material layer 23 has a higher viscosity than the upper-layer slurry 24A and the same wettability as the upper-layer slurry 24A (step S103). Specifically, as shown in Fig. 5, based on a graph showing the relationship between the wettability of the upper-layer slurry 24A and the viscosity of the upper-layer slurry 24A obtained in advance and a graph showing the relationship between the wettability of the lower-layer slurry 23A and the viscosity of the lower-layer slurry 23A obtained in advance, the wettability of the lower-layer slurry 23A is determined so that the lower-layer slurry 23A has a higher viscosity than the upper-layer slurry 24A and the same wettability as the upper-layer slurry 24A. That is, the target wettability of the lower layer slurry 23A is determined based on a relational expression indicating the relationship between the previously acquired wettability of the upper layer slurry 24A and the lower layer slurry 23A and the viscosity of the upper layer slurry 24A and the lower layer slurry 23A.

[0039] (Underlayer active material wettability calculation process) In the lower-layer active material wettability calculation step, the target wettability of the negative electrode active material of the lower-layer slurry 23A is calculated based on the target wettability of the lower-layer slurry 23A (step S104). Specifically, as shown in Fig. 6, the target wettability of the negative electrode active material of the lower-layer slurry 23A is calculated based on a relational expression derived from a graph of the wettability of the lower-layer slurry 23A and the wettability of the negative electrode active material of the lower-layer slurry 23A obtained in advance.

[0040] Here, the wettability of the negative electrode active material can be obtained, for example, by measuring the absorbance when the negative electrode active material is dissolved (stirred) in water and allowed to stand for a certain period of time, the zeta potential of the negative electrode active material, the permeation rate of water into the negative electrode active material, etc. The permeation rate of water into the negative electrode active material is measured by contacting the bottom of a cell filled with the powder with a liquid medium and measuring the change in the permeation weight of the liquid medium sucked up by capillary rise.

[0041] (Underlayer active material wettability confirmation process) In the lower layer active material wettability checking step, the wettability of the negative electrode active material of the lower layer slurry 23A is checked (measured) (Step S105).

[0042] (Gap calculation process) In the gap calculation step, a gap between the target wettability of the negative electrode active material of the lower layer slurry 23A and the measured wettability of the negative electrode active material of the lower layer slurry 23A is calculated (step S106). Specifically, as shown in Fig. 6, a gap G between the target wettability of the negative electrode active material of the lower layer slurry 23A and the measured wettability of the negative electrode active material of the lower layer slurry 23A is calculated based on a relational expression derived from a graph of the wettability of the lower layer slurry 23A and the wettability of the negative electrode active material of the lower layer slurry 23A obtained in advance.

[0043] (Plasma treatment time determination step) In the plasma treatment time determination step (an example of a functional group introduction treatment condition determination step), a plasma treatment time (an example of a functional group introduction treatment condition) for the negative electrode active material of the lower-layer slurry 23A is determined (step S107) based on the gap G. Specifically, as shown in Fig. 7, a plasma treatment time for the negative electrode active material of the lower-layer slurry 23A to have a target wettability is determined based on a relational expression derived from a previously obtained graph of the wettability of the negative electrode active material of the lower-layer slurry 23A and the plasma treatment time.

[0044] (Plasma treatment process) In the plasma treatment step (an example of a functional group introduction treatment step), a plasma treatment (an example of a functional group introduction treatment) is performed on the negative electrode active material of the lower layer slurry 23A for a determined plasma treatment time (step S108). That is, in the plasma treatment step, a plasma treatment is performed on the negative electrode active material of the lower layer slurry 23A for a determined plasma treatment time based on the wettability of the upper layer slurry 24A so that the lower layer slurry 23A has a target wettability of a higher viscosity than the upper layer slurry 24A. The plasma treatment is an example of a functional group introduction treatment, and the functional group introduction treatment refers to a treatment in which the surface of the negative electrode active material of the lower layer slurry 23A, the wettability of which is to be increased, is irradiated with energy higher than the molecular bond energy of the surface, thereby breaking the bonds and newly introducing hydrophilic functional groups such as -COOH and -OH.

[0045] (Layering process) In the multi-layering step, the manufacturing apparatus 100 applies multi-layer coating to the negative electrode current collector sheet 21 with the lower layer slurry 23A containing the negative electrode active material that has been subjected to the plasma treatment and the upper layer slurry 24A.

[0046] [Effect] However, when the viscosity of the lower-layer slurry 23A is low, the thickness of the lower-layer negative electrode active material layer 23 is unstable during coating, and the lower-layer negative electrode active material layer 23 cannot be coated at a desired layer ratio. In addition, when the solid content rate of the upper-layer slurry 24A is lower than that of the lower-layer slurry 23A, migration occurs in the upper-layer slurry 24A, and the peel strength at the interface between the upper-layer negative electrode active material layer 24 and the lower-layer negative electrode active material layer 23 decreases.

[0047] The manufacturing method of the negative electrode sheet 20 according to the embodiment includes an upper layer slurry wettability calculation step of calculating the wettability of the upper layer slurry 24A based on the viscosity of the upper layer slurry 24A forming the upper-layer negative electrode active material layer 24 to be placed in the upper layer, a plasma treatment step of performing plasma treatment on the negative electrode active material of the lower layer slurry 23A based on the wettability of the upper layer slurry 24A so that the lower layer slurry 23A forming the lower-layer negative electrode active material layer 23 to be placed in the lower layer has a target wettability with a higher viscosity than the upper layer slurry 24A, and a multi-layer coating step of performing multi-layer coating with the lower layer slurry 23A containing the negative electrode active material that has been subjected to the plasma treatment and the upper layer slurry 24A (see FIG. 4).

[0048] Based on the wettability of the upper layer slurry 24A, the negative electrode active material of the lower layer slurry 23A is subjected to plasma treatment so that the lower layer slurry 23A has a target wettability of a higher viscosity than the upper layer slurry 24A, and multi-layer coating is performed with the lower layer slurry 23A containing the negative electrode active material subjected to the plasma treatment and the upper layer slurry 24A, so that the lower layer slurry 23A has a higher viscosity than the upper layer slurry 24A and the lower layer slurry 23A has a target wettability. Therefore, the negative electrode active material layer 22 can be coated with a target layer ratio, and the wettability of the lower layer slurry 23A can be made closer to the wettability of the upper layer slurry 24A. As a result, the adhesion at the interface between the upper layer negative electrode active material layer 24 and the lower layer negative electrode active material layer 23 can be improved while maintaining the target layer ratio.

[0049] The manufacturing method of the negative electrode sheet 20 according to the embodiment includes a lower layer slurry wettability determination step of determining a target wettability of the lower layer slurry 23A having a higher viscosity than that of the upper layer slurry 24A based on the wettability of the upper layer slurry 24A, a gap calculation step of calculating a gap G between the target wettability of the negative electrode active material of the lower layer slurry 23A calculated based on the target wettability of the lower layer slurry 23A and the actually measured wettability of the negative electrode active material of the lower layer slurry 23A, and a plasma treatment time determination step of determining a plasma treatment time for the negative electrode active material of the lower layer slurry 23A based on the gap G (see FIG. 4).

[0050] A gap G between the target wettability of the negative electrode active material of the lower layer slurry 23A calculated based on the target wettability of the lower layer slurry 23A and the measured wettability of the negative electrode active material of the lower layer slurry 23A is calculated, and the plasma treatment time of the negative electrode active material of the lower layer slurry 23A is determined based on the gap G, so that the negative electrode active material of the lower layer slurry 23A has the target wettability. Therefore, the lower layer slurry 23A has the target wettability. As a result, the adhesion at the interface between the upper layer negative electrode active material layer 24 and the lower layer negative electrode active material layer 23 can be improved by a simple method.

[0051] In the manufacturing method of the negative electrode sheet 20 according to the embodiment, in the lower layer slurry wettability determination process, the wettability of the lower layer slurry 23A is determined based on a relational equation between the wettability of the upper layer slurry 24A and the lower layer slurry 23A and the viscosity of the upper layer slurry 24A and the lower layer slurry 23A, which has been previously obtained (see FIG. 4).

[0052] In the lower-layer slurry wettability determination step, the wettability of the lower-layer slurry 23A is determined based on a relational expression between the wettability of the upper-layer slurry 24A and the lower-layer slurry 23A and the viscosity of the upper-layer slurry 24A and the lower-layer slurry 23A, which has been previously obtained, thereby determining the wettability of the lower-layer slurry 23A in a simple manner. Therefore, the adhesion at the interface between the upper-layer negative electrode active material layer 24 and the lower-layer negative electrode active material layer 23 can be improved in a simple manner.

[0053] In the manufacturing method of the negative electrode sheet 20 according to the embodiment, in the gap calculation step, the gap G is calculated based on a relational expression between the wettability of the lower layer slurry 23A and the wettability of the negative electrode active material of the lower layer slurry 23A, which has been acquired in advance (see FIG. 4).

[0054] In the gap calculation step, the gap G is calculated based on a relational expression between the wettability of the lower-layer slurry 23A and the wettability of the negative electrode active material of the lower-layer slurry 23A, which has been obtained in advance, thereby calculating the gap G in a simple manner. Therefore, the adhesion at the interface between the upper-layer negative electrode active material layer 24 and the lower-layer negative electrode active material layer 23 can be improved in a simple manner.

[0055] In the manufacturing method of the negative electrode sheet 20 according to the embodiment, in the plasma treatment time determination step, the plasma treatment time is determined based on a previously obtained relational expression between the wettability of the negative electrode active material of the lower layer slurry 23A and the plasma treatment time (see FIG. 4).

[0056] In the plasma treatment time determination step, the plasma treatment time is determined based on a previously obtained relational expression between the wettability of the negative electrode active material of the lower-layer slurry 23A and the plasma treatment time, thereby determining the plasma treatment time in a simple manner. Therefore, the adhesion at the interface between the upper-layer negative electrode active material layer 24 and the lower-layer negative electrode active material layer 23 can be improved in a simple manner.

[0057] The manufacturing method of the electrode sheet of the present invention has been described above based on the embodiment. However, the specific configuration is not limited to this embodiment, and design changes and the like are permitted as long as they do not deviate from the gist of the invention according to each claim of the claims.

[0058] In the embodiment, an example was shown in which the plasma treatment time was determined as a functional group introduction treatment condition so that the negative electrode active material of the lower layer slurry 23A had a desired wettability. However, the functional group introduction treatment condition is not limited to the plasma treatment time, and may be, for example, at least one of the plasma treatment time, the plasma applied current, and the plasma applied voltage.

[0059] In the embodiment, an example in which a plasma treatment is performed as the functional group introduction treatment has been shown, but the functional group introduction treatment may be a corona treatment, an ultraviolet treatment, a flame treatment, or the like.

[0060] In the embodiment, the upper layer slurry 24A and the lower layer slurry 23A are slurries composed of natural graphite, CMC (carboxymethyl cellulose), and SBR (styrene butadiene rubber). However, the upper layer slurry and the lower layer slurry may be slurries composed of other materials.

[0061] In the embodiment, a manufacturing method for forming the lower-layer negative electrode active material layer 23 and the upper-layer negative electrode active material layer 24 on the negative electrode current collector sheet 21 has been shown. However, the manufacturing method for the electrode sheet can also be applied when forming the lower-layer positive electrode active material layer 33 and the upper positive electrode active material layer 34 on the positive electrode current collector sheet 31.

[0062] In the embodiment, an example has been shown in which the electrode sheet manufacturing method is applied to the negative electrode sheet 20 constituting the wound body 10. However, the electrode sheet manufacturing method can also be applied to an electrode sheet constituting a laminated type electrode body formed by laminating a positive electrode sheet and a negative electrode sheet.

[0063] In the embodiment, the electrode sheet manufacturing method is applied to an electrode sheet of a lithium ion secondary battery, but the electrode sheet manufacturing method can be applied to an electrode sheet having two or more active material layers. [Explanation of symbols]

[0064] 20 Negative electrode sheet (an example of an electrode sheet) 22 Negative electrode active material layer (an example of an active material layer) 23A Lower Slurry 24A Upper layer slurry G Gap

Claims

1. an upper layer slurry wettability calculation step of calculating wettability of the upper layer slurry based on the viscosity of the upper layer slurry that forms an active material layer to be disposed on the upper layer; a functional group introduction treatment step of introducing a functional group into the active material of the lower layer slurry so that a lower layer slurry forming an active material layer to be disposed in a lower layer has a target wettability of a higher viscosity than that of the upper layer slurry based on the wettability of the upper layer slurry; a multi-layer coating step of performing multi-layer coating using the lower layer slurry containing the active material to which a functional group introduction treatment has been performed and the upper layer slurry; A method for producing an electrode sheet comprising the steps of:

2. a lower layer slurry wettability determination step of determining a target wettability of the lower layer slurry, the target wettability being higher than that of the upper layer slurry, based on the wettability of the upper layer slurry; a gap calculation step of calculating a gap between a target wettability of the active material of the lower-layer slurry calculated based on the target wettability of the lower-layer slurry and an actual measured wettability of the active material of the lower-layer slurry; a functional group introduction treatment condition determination step of determining a functional group introduction treatment condition for the active material of the lower layer slurry based on the gap; The method for producing the electrode sheet according to claim 1 ,

3. In the lower layer slurry wettability determination step, the wettability of the lower layer slurry is determined based on a relational expression between the wettability of the upper layer slurry and the lower layer slurry and the viscosity of the upper layer slurry and the lower layer slurry, which has been previously obtained. A method for producing the electrode sheet according to claim 2 .

4. In the gap calculation step, the gap is calculated based on a relational expression between the wettability of the lower layer slurry and the wettability of the active material of the lower layer slurry, which has been previously obtained. A method for producing the electrode sheet according to claim 2 .

5. In the functional group introduction treatment condition determination step, the functional group introduction treatment conditions are determined based on a previously obtained relational expression between the wettability of the active material of the lower layer slurry and the functional group introduction treatment conditions. A method for producing the electrode sheet according to claim 2 .

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