Method for manufacturing power storage device

Abstract

The present invention can provide a method for manufacturing an electricity storage device capable of suppressing warping of an electrode caused by a pressing step. A method for manufacturing a power storage device according to the present invention comprises: a first pressing step for pressing an electrode in which an active material layer and an active material layer are formed on an electrode plate, thereby increasing the density of the active material layer and the active material layer; and a second pressing step in which the electrode is pressed by a correction die having a curved pressing surface, and the electrode is corrected into a shape including the curved portion.

Description

Technical Field

[0001] This invention relates to a method for manufacturing an energy storage device. Background Technology

[0002] For example, as disclosed in Patent Document 1, the unipolar or bipolar electrode constituting the energy storage device is made by forming an active material layer on the surface of the electrode plate.

[0003] Patent Document 1: Japanese Patent Application Publication No. 2021-082504 Summary of the Invention

[0004] Regarding the manufacturing method of the energy storage device disclosed in Patent Document 1, the inventors have discovered the following problems. In order to achieve a high density of the active material layer, the electrodes on the electrode plates are pressed under a specified pressure. Here, warping sometimes occurs on the pressed electrodes due to the difference between the elongation of the active material layer and the elongation of the electrode plate. If an energy storage module with multiple warped electrodes stacked on it is used in an energy storage device, the battery capacity of the energy storage device may decrease.

[0005] The present invention was made to solve this problem, and its object is to provide a method for manufacturing an energy storage device that can suppress electrode warping caused by the pressing process.

[0006] The method for manufacturing an energy storage device according to the present invention includes: a first pressing step, which presses an electrode on which an active material layer is formed on an electrode plate to increase the density of the active material layer; and a second pressing step, which presses the electrode through a straightening mold having a curved pressing surface to straighten the electrode into a shape including a curved portion. By intentionally straightening the electrode into a curved shape, the warping of the electrode that occurs in the first pressing step can be suppressed.

[0007] The electrode plate has a coated portion on which the active material layer is formed and an uncoated portion on which the active material layer is not formed. Multiple curved portions may be provided on the coated portion.

[0008] The pressure applied in the second pressing process can be less than the pressure applied in the first pressing process.

[0009] The second pressing process can pressurize the electrode stack having multiple electrodes stacked on top of each other.

[0010] It may also include an electrolyte injection process, which, after the second pressing process, involves injecting electrolyte into the interior of the electrode stack while the electrode stack is held in place by the straightening mold.

[0011] Invention Effects

[0012] The present invention provides a method for manufacturing an energy storage device that can suppress electrode warping caused by the pressing process. Attached Figure Description

[0013] Figure 1 This is a schematic cross-sectional view showing the internal structure of the energy storage module involved in Embodiment 1.

[0014] Figure 2 This is a diagram showing the structure of the electrode after an active material layer has been formed on the electrode plate according to Embodiment 1.

[0015] Figure 3 This is a flowchart of the manufacturing method of the energy storage device according to Embodiment 1.

[0016] Figure 4 This is a cross-sectional view showing the electrodes before and after the second pressing process involved in Embodiment 1.

[0017] Figure 5 This is a cross-sectional view of the electrode and the straightening mold in the second pressing process according to Embodiment 1.

[0018] Figure 6 This is an embodiment of the lower mold of the straightening mold in the second pressing process involved in Embodiment 1. Detailed Implementation

[0019] Hereinafter, specific embodiments of the present invention will be described in detail with reference to the accompanying drawings. However, the present invention is not limited to the following embodiments. Furthermore, for clarity, the following description and drawings have been appropriately simplified.

[0020] (Implementation Method 1)

[0021] <Structure of Energy Storage Device>

[0022] The energy storage device has one or more energy storage modules. The energy storage module is a plate-shaped non-aqueous battery, such as a bipolar battery with bipolar electrodes or a unipolar battery with unipolar electrodes. An example of a bipolar battery with bipolar electrodes is given below.

[0023] refer to Figure 1 The energy storage module included in the energy storage device according to Embodiment 1 will be described. Figure 1 This is a schematic cross-sectional view showing the internal structure of the energy storage module according to Embodiment 1. The energy storage module 1 includes: an electrode stack 11, which includes a plurality of electrodes 14; and a sealing body 12, which is used to seal the electrode stack 11.

[0024] Within the electrode stack 11, multiple electrodes 14 are stacked with partitions 13 in between. Each electrode 14 is a bipolar electrode having an electrode plate 15, a positive electrode layer 16, and a negative electrode layer 17.

[0025] The electrode plate 15 is a sheet-like conductive component, generally rectangular in shape. The electrode plate 15 may have, for example, a structure integrating multiple metal foils of different types. The multiple metal foils are bonded together. Each metal foil may be, for example, copper foil, aluminum foil, titanium foil, or nickel foil.

[0026] The positive electrode layer 16 is formed by coating a positive electrode layer material onto the surface of the electrode plate 15 and then drying it. The positive electrode layer material includes a positive electrode active material, a conductive additive, and a binder. The negative electrode layer 17 is formed by coating a negative electrode layer material onto the side of the electrode plate 15 opposite to the side where the positive electrode layer 16 is formed, and then drying it. The negative electrode layer material includes a negative electrode active material, a conductive additive, and a binder. The positive electrode layer 16 and the negative electrode layer 17 are collectively referred to as the active material layers.

[0027] Figure 2 This is a diagram showing the structure of the electrode after an active material layer has been formed on the electrode plate according to Embodiment 1. Figure 2 The image above is a top view of electrode 14. Figure 2 The figure below is a cross-sectional view of electrode 14. Electrode 14 has a coated portion P1 on which an active material layer is formed on electrode plate 15 and an uncoated portion P2 on which no active material layer is formed on electrode plate 15.

[0028] Return to Figure 1 The following description is provided. A negative electrode layer terminal electrode 18 is disposed at the first end of the electrode stack 11, and a positive electrode layer terminal electrode 19 is disposed at the second end opposite to the first end of the electrode stack 11. The negative electrode layer terminal electrode 18 is an electrode having an electrode plate 15 and a negative electrode layer 17. The positive electrode layer terminal electrode 19 is an electrode having an electrode plate 15 and a positive electrode layer 16. A plurality of electrodes 14 are disposed between the negative electrode layer terminal electrode 18 and the positive electrode layer terminal electrode 19 in the stacking direction.

[0029] The sealing body 12 is provided to surround the sides of the electrode stack 11. Examples of materials used in the sealing body 12 include polypropylene, polyphenylene sulfide, or modified polyphenylene sulfide. Furthermore, the sealing body 12 has a through-hole (not shown) for supplying electrolyte to the interior of the electrode stack 11.

[0030] <Manufacturing Method of Energy Storage Device>

[0031] Next, the manufacturing method of the energy storage device according to Embodiment 1 will be described. Figure 3 This is a flowchart of the manufacturing method of the energy storage device according to Embodiment 1.

[0032] First, a coating process is performed to coat a positive electrode layer material on one side of the electrode plate 15 and a negative electrode layer material on the other side (step S101).

[0033] Next, a drying process (step S102) is performed to dry the positive electrode layer material and the negative electrode layer material coated on the electrode plate 15. The solvent of the positive electrode layer material and the negative electrode layer material is removed by drying, and the positive electrode layer 16 and the negative electrode layer 17 are formed.

[0034] Furthermore, the formation of the positive electrode layer 16 and the negative electrode layer 17 based on the coating process (step S101) and the drying process (step S102) can be performed at different times. In other words, for example, the positive electrode layer 16 can be formed first by the coating process (step S101) and the drying process (step S102), and then the negative electrode layer 17 can be formed again by the coating process (step S101) and the drying process (step S102).

[0035] Next, a first pressing process (step S103) is performed to pressurize the electrode 14, thereby increasing the density of the positive electrode layer 16 and the negative electrode layer 17. By pressing, the thicknesses of the positive electrode layer 16 and the negative electrode layer 17 decrease, thereby increasing the density of the active material in the positive electrode layer 16 and the negative electrode layer 17. In the first pressing process, the electrode 14 is conveyed and pressed simultaneously, for example, by rotating a pair of pressing rollers. However, it is not limited to a pair of pressing rollers; the electrode 14 can also be pressed using a pair of molds.

[0036] Next, a cutting process (step S104) is performed to divide the electrode 14 into multiple parts. The electrode 14 is cut into a specified length, for example, using a cutting device with a blade.

[0037] Next, a second pressing process (step S105) is performed, in which the electrode 14 is pressed by a straightening mold T having a curved pressing surface, and the electrode 14 is straightened into a shape including the curved portion C. The second pressing process (step S105) will be described in detail later.

[0038] Next, a stacking process is performed to form an electrode stack 11 by stacking multiple electrodes 14 with the partition 13 in between (step S106). Thereafter, a sealing body 12 is formed on the electrode stack 11.

[0039] Next, an electrolyte injection process (step S107) is performed to inject electrolyte into the interior of the electrode stack 11. First, the electrode stack 11 and the sealing body 12 are clamped in the stacking direction by a constraint plate. Furthermore, the electrode stack 11 and the sealing body 12 are constrained at a predetermined pressure. While maintaining the constraint, electrolyte is injected into the interior of the electrode stack 11 through a through-hole (not shown) provided in the sealing body 12. The injected electrolyte impregnates the separator 13, the positive electrode layer 16, and the negative electrode layer 17, respectively. Thus, the energy storage module 1 is obtained. Furthermore, the electrolyte injection method is not particularly limited; for example, a known method utilizing an injection device can be used. As the electrolyte, for example, a known organic electrolyte used in lithium-ion secondary batteries can be appropriately used.

[0040] Next, an activation process (step S108) is performed to activate the energy storage module 1 as a battery. In the activation process (step S108), the energy storage module 1 is activated, for example, by sequentially performing an initial charging process, a high-temperature aging process, and a self-discharge check.

[0041] Finally, a sealing process (step S109) is performed to seal the energy storage module 1 under reduced pressure. First, the energy storage module 1 is placed in the chamber, and a vacuum is evacuated from the chamber. Then, the through hole (not shown) provided in the sealing body 12 is sealed. Thus, the energy storage module 1 can be sealed under reduced pressure.

[0042] <Second pressing process>

[0043] The second pressing process (step S105) will be described in detail. Figure 4 This is a cross-sectional view showing the electrodes before and after the second pressing process involved in Embodiment 1. Figure 4 The above figure is a cross-sectional view of electrode 14 before the second pressing process (step S105). Figure 4 The figure below is a cross-sectional view of electrode 14 after the second pressing process (step S105).

[0044] Due to the different elongation rates of the electrode plate 15, the positive electrode layer 16, and the negative electrode layer 17, a process is achieved on the electrode 14 after the first pressing process (step S103) as follows: Figure 4 The warping shown in the figure above. If an energy storage module 1 with multiple warped electrodes 14 stacked together is used in an energy storage device, the battery capacity of the energy storage device may decrease. Therefore, in order to suppress the warping generated by the first pressing process (step S103), a second pressing process (step S105) is performed.

[0045] Through the second pressing process (step S105), such as Figure 4 As shown in the figure below, electrode 14 is corrected to include a curved portion C. In this way, by intentionally correcting electrode 14 to be curved, warping caused by the first pressing process (step S103) can be suppressed.

[0046] Figure 5 This is a cross-sectional view of the electrode and the straightening mold in the second pressing process according to Embodiment 1. Figure 5 As shown, electrode 14 is pressurized by a pair of straightening dies T having a bent pressing surface. Alternatively, the straightening die T can be a pressure roller. When the straightening die T is a pressure roller, the electrode 14 is conveyed and pressurized simultaneously by rotating the pair of pressure rollers. Furthermore, the pair of straightening dies T can be a die made of elastic material, one having a bent pressing surface and the other having a flat processing surface.

[0047] The number or shape of the bent portion C of electrode 14 is determined based on the number or shape of the protrusions and concave portions provided on the machining surface of the straightening mold T. Figure 6 This is an embodiment of the lower die of the straightening mold in the second pressing process according to Embodiment 1. Using Figure 6 The electrode 14 produced by the lower mold of the corrective mold T shown has, for example, one bent portion C in Embodiment 1, 16 bent portions C in Embodiment 5, and eight bent portions C in Embodiment 6. Figure 6 As shown, in electrode 14, the curved portion C can be alternately configured with an upwardly convex curved portion C and a downwardly convex curved portion C. Furthermore, the shape of the curved portion C can be elliptical, as in Embodiments 3 and 6.

[0048] The more bends C there are in electrode 14, the greater the warpage suppression effect. For example... Figure 6 As shown, the number of uneven portions provided on the machining surface of the straightening mold T is the highest in Embodiment 5. Furthermore, the electrode 14, which is pressurized by the straightening mold T of Embodiment 5, has... Figure 6 The illustrated embodiment showed the highest warpage suppression effect.

[0049] Furthermore, the pressure applied in the second pressing step (step S105) is preferably less than the pressure applied in the first pressing step (step S103). This suppresses the localized load on the bent portion C of the electrode 14 caused by the pressure applied by the straightening mold T. Moreover, it suppresses the occurrence of damage to the positive electrode layer 16 and the negative electrode layer 17.

[0050] Electrode 14 exhibits creep characteristics; therefore, by appropriately optimizing the pressure, room temperature, and pressing time in the second pressing step (step S105), warping can be more effectively suppressed. For example, the pressure is preferably 40 to 80 kPa, and the temperature is preferably 80°C or higher. Furthermore, the optimal values ​​for pressure, room temperature, and pressing time vary depending on the material or size of electrode 14, and are therefore not limited to the values ​​described above.

[0051] A bus bar is provided on the uncoated portion P2 of electrode 14. Therefore, the bent portion C of electrode 14 is preferably provided on the coated portion P1 rather than on the uncoated portion P2.

[0052] The manufacturing method of the energy storage device according to Embodiment 1 has been described above, but the order of the steps is not limited thereto and can be appropriately replaced. For example, the second pressing step (step S105) can be performed after the lamination step (step S106). In this case, the second pressing step (step S105) applies pressure to the electrode laminate 11 using a straightening mold T, straightening the electrode laminate 11 into a shape including multiple bends C.

[0053] Furthermore, in the subsequent electrolyte injection process (step S107), electrolyte can be injected into the interior of the electrode stack 11 while the electrode stack 11 and the sealing body 12 are held by the straightening mold T. This reduces the time required to move the electrode stack 11 and the sealing body 12 from the straightening mold T to the constraint plate.

[0054] Symbol Explanation

[0055] 1-Electric storage module, 11-Electrode stack, 12-Sealing body, 13-Separator, 14-Electrode, 15-Electrode plate, 16-Positive electrode layer, 17-Negative electrode layer, 18-Negative electrode layer terminal electrode, 19-Positive electrode layer terminal electrode, C-Bending part, P1-Coated part, P2-Uncoated part, T-Correcting mold.

Claims

1. A method for manufacturing an energy storage device, characterized in that, have: The first pressing process involves applying pressure to an electrode on which an active material layer has been formed on an electrode plate, thereby increasing the density of the active material layer; and The second pressing process involves pressing the electrode with a straightening mold having a curved pressing surface to straighten the electrode into a shape including a curved portion.

2. The method for manufacturing the energy storage device according to claim 1, characterized in that, The electrode plate has a coated portion with the active material layer formed thereon and an uncoated portion without the active material layer formed thereon. The coated portion has a plurality of curved sections.

3. The method for manufacturing the energy storage device according to claim 1 or 2, characterized in that, The pressure applied in the second pressing process is less than the pressure applied in the first pressing process.

4. The method for manufacturing the energy storage device according to claim 1 or 2, characterized in that, The second pressing process applies pressure to the electrode stack having multiple electrodes.

5. The method for manufacturing the energy storage device according to claim 4, characterized in that, It also has: The electrolyte injection process, which occurs after the second pressing process, involves injecting electrolyte into the interior of the electrode stack while the electrode stack is held in place by the straightening mold.

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