Manufacturing method for electrode body

Abstract

To provide a manufacturing method for an electrode body that can adjust a thickness of the electrode body.SOLUTION: The manufacturing method for an electrode body includes a pressing step of forming an electrode body 10 by applying pressure, and a baking step of removing a solvent included in an active material layer by heating the electrode body 10 after the pressing step. In the baking step, a baking furnace 30A having a heating source 32, a first measuring instrument 22 provided at an inlet side of the baking furnace 30A and a second measuring instrument 24 provided at an outlet side of the baking furnace 30A are used; a spring-back amount is derived based on a differential between a thickness of the electrode body 10 not heated and measured by the first measuring instrument 22 and a thickness of the electrode body 10 heated and measured by the second measuring instrument 24; and when the derived spring-back amount is a predetermined value or lower, a temperature of the electrode body is increased by the heating source 32 on the basis of a differentia between the predetermined value and the spring-back amount.SELECTED DRAWING: Figure 3

Description

[Technical field]

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

[0002] Conventionally, in a method for manufacturing a secondary battery, a technique is known in which an active material layer is applied to a current collector, the applied active material layer is dried, and the active material layer is pressed onto the current collector to manufacture an electrode body. When manufacturing an electrode body in this manner, a baking step may be provided in which the pressed electrode body is further heated in order to remove the solvent contained in the active material layer. Patent Document 1 discloses a technique in which the applied coating layer is heated by a laser to remove the solvent from the coating layer. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 06-063495 Summary of the Invention [Problem to be solved by the invention]

[0004] However, when manufacturing an electrode body, if a baking step is performed after the pressing step, springback is promoted by heating, causing variation in the thickness of the pressed active material layer, and there is room for improvement in the thickness of the electrode body.

[0005] In consideration of the above, an object of the present invention is to provide a method for manufacturing an electrode assembly that allows the thickness of the electrode assembly to be adjusted. [Means for solving the problem]

[0006] The manufacturing method of the electrode body according to the present invention described in claim 1 includes a film forming step of coating one or both sides of a current collector with an active material and drying it to form an active material layer, a pressing step of applying pressure to the current collector to compress the active material layer to form an electrode body, and a baking step of heating the electrode body after the pressing step to remove solvent contained in the active material layer. In the baking step, a bake furnace having a heat source, a first measuring device provided at the entrance side of the bake furnace for measuring the thickness of the electrode body before heating, and a second measuring device provided at the exit side of the bake furnace for measuring the thickness of the electrode body after heating are used, and a springback amount is calculated based on the difference between the thickness of the electrode body before heating measured by the first measuring device and the thickness of the electrode body after heating measured by the second measuring device. If the calculated springback amount is equal to or less than a predetermined value, the temperature is increased by the heat source based on the difference between the predetermined value and the springback amount.

[0007] In the manufacturing method of the electrode body according to the present invention, a baking step is performed after the pressing step, and in the baking step, the amount of springback is derived based on the difference between the thickness of the electrode body before heating in a baking furnace and the thickness of the electrode body after heating in a baking furnace. If the derived amount of springback is equal to or less than a predetermined value, the heating source of the baking furnace is heated based on the difference between the predetermined value and the amount of springback. Therefore, if the amount of return of the thickness of the electrode body is insufficient, the heating source is heated, so that the insufficient amount of heating can be compensated for and the amount of springback can be adjusted. This allows the thickness of the electrode body to be adjusted. Effect of the Invention

[0008] As described above, the method for manufacturing an electrode assembly according to the present invention has the excellent effect of being able to adjust the thickness of the electrode assembly. [Brief description of the drawings]

[0009] [Figure 1] 1 is a cross-sectional view of an electrode body according to one embodiment of the present invention. [Diagram 2]1 is a flowchart showing a series of steps in a method for manufacturing an electrode assembly according to one embodiment of the present invention. [Diagram 3] FIG. 2 is a perspective view showing a baking step included in a manufacturing method of an electrode body according to one embodiment of the present invention. [Figure 4] 13 is a plan view showing a baking step included in a manufacturing method of an electrode body according to another embodiment of the present invention. FIG. [Diagram 5] 3 is a flowchart showing an example of the process flow of the baking step in FIG. 2. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] A method for manufacturing an electrode body 10 according to an embodiment of the present invention will be described below with reference to the accompanying drawings. The electrode body 10 of this embodiment is used, for example, in a lithium ion secondary battery or a nickel-hydrogen secondary battery, which are examples of non-aqueous electrolyte secondary batteries. Non-aqueous electrolyte secondary batteries are used, for example, in batteries for various vehicles such as forklifts, hybrid cars, and electric cars. The non-aqueous electrolyte secondary battery is, for example, a flat laminated battery, and specifically, is configured by laminating a plurality of electrode bodies 10, which will be described later.

[0011] 1, the electrode body 10 has a current collector 12 formed of a metal plate, and an active material layer 14 provided on one side of the current collector 12. In the present embodiment, the electrode body 10 will be described below as having the active material layer 14 provided on one side, but the present invention is not limited to this, and can also be applied to an embodiment in which the active material layer 14 is provided on both sides.

[0012] Examples of the electrode body 10 include a positive electrode body in which a positive electrode active material layer is provided on one or both sides of the current collector 12, a negative electrode body in which a negative electrode active material layer is provided on one or both sides of the current collector 12, and a bipolar electrode body in which a positive electrode active material layer is provided on one side of the current collector 12 and a negative electrode active material layer is provided on the other side of the current collector 12. In this embodiment, both the positive electrode active material layer and the negative electrode active material layer correspond to the "active material layer" in the present invention.

[0013] The current collector 12 is formed of a rectangular metal plate made of a metal such as aluminum, stainless steel, nickel, copper, etc. Alternatively, it may be a foil whose metal surface is coated with aluminum, copper, etc. Moreover, the edge portion 12c of the current collector 12 is formed into a rectangular frame shape, and serves as an uncoated region where the active material layer 14 is not coated.

[0014] The active material layer 14 is formed by applying an active material to the current collector 12. In this embodiment, both the positive electrode active material and the negative electrode active material correspond to the "active material" in the present invention.

[0015] The positive electrode active material layer as the active material layer 14 is formed by applying a positive electrode active material to the current collector 12. Examples of the positive electrode active material include oxide active materials. Examples of the oxide active material include LiCoO2, LiMnO2, LiNiO2, LiVO2, LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2, etc., rock salt layered active materials, LiMn2O4, Li(Ni 0.5 Mn 1.5 )O4 and the like; and olivine type active materials such as LiFePO4, LiMnPO4, LiNiPO4, and LiCuPO4.

[0016] The negative electrode active material layer as the active material layer 14 is formed by applying a negative electrode active material to the current collector 12. Examples of the negative electrode active material include a carbon active material, an oxide active material, and a metal active material.

[0017] As shown in Fig. 2, the manufacturing method of the electrode body 10 configured as described above first includes a kneading step S11 in which solid components including an active material are dissolved in a solvent and kneaded to prepare a slurry in a general environment. Note that the "solid components" here refer to components other than the solvent contained in the slurry. In addition, in this embodiment, a non-aqueous solvent is used as the "solvent".

[0018] Next, in step S12, a film-forming process is performed in which the slurry is applied to the current collector 12 and dried to form the active material layer 14. Specifically, the current collector 12 is in a roll shape, and a slurry containing an active material is applied to one surface of the sheet-like current collector 12 extending from the roll-shaped current collector 12, and then dried. The film-forming method in the film-forming process is not particularly limited, and a known method can be used.

[0019] Next, in step S13, a pressing step is performed in which pressure is applied to the current collector 12 to compress the formed active material layer 14 and adjust the active material layer 14 to a target density (thickness) to form the electrode body 10. The pressing method in the pressing step is not particularly limited, and any known method can be used.

[0020] In this embodiment, after the pressing step, in step S14, a baking step is performed in which the electrode body 10 is heated in a dry environment to remove the solvent contained in the active material layer 14. At this time, the moisture in the active material layer 14 is completely dried to the order of several hundred ppm (parts per million).

[0021] Next, in step S15, a cutting process is performed in which the sheet-shaped electrode body 10 is cut to a predetermined size in a dry environment. The cutting method in the cutting process is not particularly limited, and any known method can be used. In this manner, the rectangular electrode body 10 shown in FIG. 1 is manufactured.

[0022] Next, the baking step will be described in detail. The baking step is performed using an electrode drying device 20 shown in Fig. 3. The electrode drying device 20 includes a heating section 30, a first measuring section 22 provided on the inlet side of the heating section 30, a second measuring section 24 provided on the outlet side of the heating section 30, and a control device (not shown). The heating section 30 includes a baking furnace 30A that uses a laser as a heating source, and a hot air oven 30B that uses hot air as a heating source.

[0023] 3, since the baking step is performed before the cutting step, the edge portions 12c of the multiple electrode assemblies 10 are connected to each other as uncoated regions. The electrode assemblies 10 are transported by a known transport device (not shown) at a speed V of, for example, 30 m / min in the order of the first measurement section 22, the heating section 30, and the second measurement section 24.

[0024] The bake furnace 30A includes a laser irradiator 32 as a heating source and a radiation thermometer 34. As an example, the laser irradiator 32 irradiates a near-infrared laser having a wavelength of about 1 μm. Note that the wavelength of the laser irradiated by the laser irradiator 32 can be appropriately adjusted depending on the type of solvent.

[0025] The radiation thermometer 34 is a thermometer that detects infrared rays to measure temperature, and uses a thermometer that has a detection range that is outside the vicinity of the wavelength of the laser irradiated by the laser irradiator 32 (a wavelength of 1 μm in this embodiment) so as not to detect the wavelength originating from the laser irradiator 32. In this embodiment, the radiation thermometer 34 measures the radiation temperature from the surface of the active material layer 14.

[0026] Hot air oven 30B is a device that blows hot air onto active material layer 14, and a known device can be used. By using hot air oven 30B in addition to bake oven 30A in this way, the drying speed can be increased.

[0027] The first measuring unit 22 and the second measuring unit 24 are equipped with a measuring device for measuring the thickness of the electrode body 10, and as an example of the measuring device, a laser displacement sensor can be used. In this embodiment, the laser displacement sensors are installed on the upper and lower sides of the electrode body 10, for example, at positions separated by a distance L. If the distance to the upper surface of the electrode body 10 measured by the upper laser displacement sensor is distance A, and the distance to the lower surface of the electrode body 10 measured by the lower laser displacement sensor is distance B, the thickness t can be measured by t = L - (A + B).

[0028] The first measuring unit 22 is provided on the entrance side of the bake furnace 30A, and measures the thickness of the electrode assembly 10 before heating by the heating unit 30. The second measuring unit 24 is provided on the exit side of the bake furnace 30A and on the exit side of the hot air oven 30B, and measures the thickness of the electrode assembly 10 after heating by the heating unit 30.

[0029] 4, for example, when the electrode body 10 is provided with grooves 10A in the transport direction (from left to right on the paper) and is in a striped shape, each stripe is provided with the above-mentioned first measurement unit 22, laser irradiator 32, radiation thermometer 34, and second measurement unit 24. Even if the grooves 10A are not provided, multiple sets of the first measurement unit 22, laser irradiator 32, radiation thermometer 34, and second measurement unit 24 may be provided at a predetermined pitch in the width direction of the electrode body 10 (direction substantially perpendicular to the transport direction).

[0030] Although not shown, the control device includes a CPU, RAM, ROM, and a communication I / F, and controls an example of processing in the baking process. Fig. 5 is a flow chart showing an example of the processing flow of the baking process in Fig. 2. In this embodiment, the control device repeatedly performs the processing in Fig. 5 at a predetermined interval.

[0031] As shown in FIG. 5, in step S21, the control device derives the amount of springback from the difference in thickness of the electrode assembly 10 before and after heating by the heating unit 30 based on the thickness acquired by the first measuring unit 22 and the second measuring unit 24. At this time, the electrode assembly 10 to be measured by the first measuring unit 22 and the electrode assembly 10 to be measured by the second measuring unit 24 do not have to be the same electrode assembly 10. That is, as shown in FIG. 3, the control device detects the difference in thickness when, for example, two electrode bodies 10-1 and 10-4 sandwiching two electrode bodies 10 therebetween are measured at the same time. In this embodiment, the detected difference in thickness is taken as the amount of springback generated by the return of the thickness of the pressed electrode assembly 10.

[0032] Next, in step S22, the control device determines whether the springback amount derived in step S21 is smaller than a predetermined value. Here, the predetermined value is a value that is previously determined for each type of electrode body 10. In step S22, if the springback amount is equal to or greater than the predetermined value (step S22; NO), the process ends. That is, the heating temperature by the laser irradiator 32 is maintained as it is.

[0033] On the other hand, if the amount of springback is smaller than the predetermined value in step S22 (step S22; YES), in step S23, the control device calculates the difference between the amount of springback and the predetermined value. Next, in step S24, the control device increases the temperature by the laser irradiator 32, which is the heating source, based on the difference between the amount of springback calculated in step S23 and the predetermined value. Specifically, the control device increases the temperature by increasing the laser output of the laser irradiator 32. The control device increases the laser output by, for example, PID (Proportional-Integral-Differential Controller) control while checking the temperature output by the radiation thermometer 34.

[0034] In addition, when there is variation in thickness within the width direction of the electrode body 10, as an example, as shown in Figure 4, multiple sets of first measuring unit 22, laser irradiator 32, radiation thermometer 34, and second measuring unit 24 are arranged in the width direction of the electrode body 10 (a direction approximately perpendicular to the conveying direction), and the control device performs feedback control for each laser irradiator 32 so that the thickness within the plane is uniform.

[0035] In addition, since the heating conditions required for springback depend on the specifications of the electrode body 10, heating is performed in advance at a temperature within the practical range for each specification of the electrode body 10, and the springback amount at the heating temperature is calculated. That is, a setting table showing the springback amount relative to the heating temperature is obtained. For example, in the case of an LFP (lithium iron phosphate) positive electrode, the springback amount increases by 0.2 μm every time the heating temperature increases by 1° C. Therefore, the temperature for filling the difference between the springback amount and a predetermined value can be calculated by dividing the difference by 0.2.

[0036] Next, the effects of the method for manufacturing the electrode body 10 in this embodiment will be described.

[0037] In the manufacturing method of the electrode body 10 in this embodiment, a baking process is performed after the pressing process, and in the baking process, the springback amount is derived based on the difference between the thickness of the electrode body 10 before heating by the baking furnace 30A and the thickness of the electrode body 10 after heating by the baking furnace 30A. Then, when the derived springback amount is equal to or less than a predetermined value, the temperature of the laser irradiator 32, which is the heating source of the baking furnace 30A, is increased based on the difference between the predetermined value and the springback amount. Therefore, when the return amount of the thickness of the electrode body 10 is insufficient, the temperature is increased by the laser irradiator 32, which is the heating source, so that the insufficient heating can be compensated for and the springback amount can be adjusted. This allows the thickness of the electrode body 10 to be adjusted.

[0038] [remarks] In the above embodiment, the heating unit 30 includes the bake furnace 30A and the hot air furnace 30B, but the present invention is not limited to this, and may include only the bake furnace 30A. Heating by laser has better responsiveness than heating by hot air, and the temperature-raising section can be precisely divided.

[0039] The temperature of the electrode assembly 10 can also be adjusted by the control device controlling the transport speed V of the electrode assembly 10.

[0040] Furthermore, the configuration of the present disclosure is not limited to the above-described embodiment, and the configuration can be modified as appropriate as long as the problem can be solved. [Explanation of symbols]

[0041] 10 electrode body, 12 current collector, 14 active material layer, 32 laser irradiator (heat source), 30A bake oven, 22 first measurement section (first measurement device), 24 second measurement section (second measurement device)

Claims

[Claim 1] a film-forming step of coating one or both sides of a current collector with an active material and drying the coating to form an active material layer; a pressing step of applying pressure to the current collector to compress the active material layer to form an electrode body; a baking step of removing a solvent contained in the active material layer by heating the electrode body after the pressing step, The baking process uses a bake furnace having a heating source, a first measuring device provided on the entrance side of the bake furnace for measuring the thickness of the electrode body before heating, and a second measuring device provided on the exit side of the bake furnace for measuring the thickness of the electrode body after heating, and derives the amount of springback based on the difference between the thickness of the electrode body before heating measured by the first measuring device and the thickness of the electrode body after heating measured by the second measuring device, and if the derived amount of springback is less than a predetermined value, the temperature is raised by the heating source based on the difference between the predetermined value and the amount of springback.

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