Energy storage device

Abstract

The present invention relates to an energy storage device, comprising: a first metal layer formed on a first side of a first current collector foil in which a first active material layer is not formed; and a second metal layer formed on a second side of a second current collector foil in which a second active material layer is not formed, wherein the first metal layer and the second metal layer are disposed at a position overlapping in the thickness direction of the electrode foil, wherein the coefficient of thermal expansion of the first current collector foil is greater than that of the second current collector foil, and the coefficient of thermal expansion of the first metal layer is smaller than that of the second metal layer.

Description

Technical Field

[0001] This invention relates to energy storage devices. Background Technology

[0002] Japanese Patent Application Publication No. 2005-317468 discloses a bipolar electrode in which the surface of the positive current collector without the positive active material layer is connected to the surface of the negative current collector without the negative active material layer. Summary of the Invention

[0003] In the bipolar electrode disclosed in Japanese Patent Application Publication No. 2005-317468, when current flows and the positive and negative current collectors heat up, warping occurs in the thinner portions where the positive and negative active material layers are not formed, due to the difference in the coefficients of thermal expansion between the positive and negative current collectors.

[0004] The present invention was made in view of the above-mentioned problems, and its object is to provide an energy storage device capable of suppressing warping of an electrode foil having a first current collector foil having a first active material layer and a second current collector foil having a second active material layer.

[0005] To address the aforementioned issues and achieve the objectives, the energy storage device of the present invention comprises an electrode foil having a first current-collecting foil on a first surface having a first active material layer formed thereon and a second current-collecting foil on a second surface having a second active material layer formed thereon. A third surface of the first current-collecting foil opposite to the first surface and a fourth surface of the second current-collecting foil opposite to the second surface are connected facing each other. The energy storage device is characterized by having: a first metal layer formed on a portion of the first surface of the first current-collecting foil where the first active material layer is not formed; and a second metal layer formed on a portion of the second surface of the second current-collecting foil where the second active material layer is not formed. The first metal layer and the second metal layer are disposed at an overlapping position in the thickness direction of the electrode foil. The coefficient of thermal expansion of the first current-collecting foil is greater than that of the second current-collecting foil, and the coefficient of thermal expansion of the first metal layer is smaller than that of the second metal layer.

[0006] Therefore, in the energy storage device of the present invention, warping of the electrode foil having a first current collector foil having a first active material layer and a second current collector foil having a second active material layer can be suppressed.

[0007] Alternatively, as described above, the first current collector foil and the second metal layer may be of the same type of metal, and the second current collector foil and the first metal layer may also be of the same type of metal.

[0008] Therefore, the metal materials used for the first current collector foil and the second current collector foil can be used in the first metal layer and the second metal layer respectively, thus simplifying the structure of the electrode foil.

[0009] Alternatively, in the above, the portion of the first surface on which the first metal layer is formed that does not have the first active material layer can be the peripheral portion of the first surface, and the portion of the second surface on which the second metal layer is formed that does not have the second active material layer can be the peripheral portion of the second surface.

[0010] Therefore, it is possible to suppress the buckling of the electrode foil at its periphery caused by the difference in thermal expansion coefficients between the first and second current collector foils.

[0011] The energy storage device of the present invention has the effect of suppressing warping of the electrode foil having a first current collector foil having a first active material layer and a second current collector foil having a second active material layer. Attached Figure Description

[0012] The features, advantages, and technical and industrial significance of exemplary embodiments of the present invention will now be described with reference to the accompanying drawings, wherein the same reference numerals denote the same elements.

[0013] Figure 1 This is a cross-sectional view showing the general structure of the main parts of the energy storage device in the embodiment.

[0014] Figure 2 This is a top view showing the schematic structure of the energy storage device according to the embodiment;

[0015] Figure 3 This is a cross-sectional view showing another example of the schematic structure of the main parts of the energy storage device in the embodiment. Detailed Implementation

[0016] Hereinafter, embodiments of the energy storage device of the present invention will be described. However, the present invention is not limited to these embodiments.

[0017] Figure 1 This is a cross-sectional view showing the schematic structure of the main parts of the energy storage device 1 in the embodiment. Figure 2 This is a top view showing the schematic structure of the energy storage device 1 according to the embodiment. Figure 3 This is a cross-sectional view showing another example of the schematic structure of the main parts of the energy storage device 1 in the embodiment.

[0018] The energy storage device 1 of the embodiment includes a plurality of bipolar electrode foils 2, a plurality of spacers 3, and an end face welding portion 4. The plurality of bipolar electrode foils 2 and the plurality of spacers 3 are each flat and are stacked alternately, and their outer ends (peripheral ends) are embedded in the end face welding portion 4 made of resin and fused together.

[0019] The bipolar electrode foil 2 is a bonded electrode foil formed by bonding a positive current-collecting foil 21, which is a first current-collecting foil in the shape of a flat plate, and a negative current-collecting foil 22, which is a second current-collecting foil in the shape of a flat plate. For example... Figure 2 As shown, on the first surface 21a of the positive electrode current collector foil 21, there is a coated portion in the inward direction where a positive electrode active material, which is the first active material, is coated, and an uncoated portion in the outward direction (peripheral portion of surface 21a) where no positive electrode active material is coated. On the coated portion on the surface 21a of the positive electrode current collector foil 21, a positive electrode active material layer 211, which is the first active material layer, is formed by coating the positive electrode active material. On the uncoated portion on the surface 21a of the positive electrode current collector foil 21, a first metal layer 212 is formed, which is made of the same type of metal as the negative electrode current collector foil 22. The thickness of the first metal layer 212 is, for example, tens of μm to hundreds of μm, preferably less than or equal to the thickness of the positive electrode active material layer (first active material layer) 211.

[0020] On the surface 22a of the negative electrode current collector foil 22, which serves as the second surface, there are coated portions where a negative electrode active material is coated on the inner side in the surface direction, and uncoated portions where no negative electrode active material is coated on the outer side (peripheral portion of surface 22a) in the surface direction. A negative electrode active material is coated on the coated portions on the surface 22a of the negative electrode current collector foil 22 to form a negative electrode active material layer 221, which serves as the second active material layer. Furthermore, a second metal layer 222, made of the same metal as the positive electrode current collector foil 21, is formed on the uncoated portions on the surface 22a of the negative electrode current collector foil 22. The thickness of the second metal layer 222 is, for example, tens of μm to hundreds of μm, preferably less than or equal to the thickness of the negative electrode active material layer (second active material layer) 221.

[0021] Furthermore, in the bipolar electrode foil 2, the third side (back side 21b) of the positive current collector foil 21, opposite to the front side 21a, and the fourth side (back side 22b) of the negative current collector foil 22, opposite to the front side 22a, are connected facing each other. Additionally, in the bipolar electrode foil 2, one of the front side 21a of the positive current collector foil 21 and the front side 22a of the negative current collector foil 22 becomes the front side of the bipolar electrode foil 2, and the other becomes the back side of the bipolar electrode foil 2. Furthermore, the coated portions of the positive current collector foil 21 and the coated portions of the negative current collector foil 22 are the coated portions of the bipolar electrode foil 2. Furthermore, the uncoated portions of the positive current collector foil 21 and the uncoated portions of the negative current collector foil 22 are the uncoated portions of the bipolar electrode foil 2.

[0022] like Figure 1 As shown, the first metal layer 212 of the positive electrode current collector foil 21 and the second metal layer 222 of the negative electrode current collector foil 22 are arranged at a position where they overlap in the thickness direction of the bipolar electrode foil 2. Furthermore, as... Figure 1As shown, the outer end faces of the first metal layer 212 of the positive electrode current collector foil 21 and the second metal layer 222 of the negative electrode current collector foil 22, respectively, are in contact with the side surface of the end face fusion portion 4 in the planar direction. Furthermore, as... Figure 3 As shown, the outer end of the first metal layer 212 in the surface direction and the outer end of the second metal layer 222 in the surface direction can also be embedded in the end face weld portion 4.

[0023] The positive electrode current collector foil 21 and the negative electrode current collector foil 22 are made of different metallic materials, resulting in the positive electrode current collector foil 21 having a larger coefficient of thermal expansion than the negative electrode current collector foil 22. For example, the positive electrode current collector foil 21 is made of aluminum, and the negative electrode current collector foil 22 is made of copper. For reference, the coefficient of thermal expansion of aluminum is 23.1 × 10⁻⁶. -6 At ℃, the coefficient of thermal expansion of copper is 16.5 × 10⁻⁶. -6 At ℃, aluminum has a coefficient of thermal expansion that is 1.4 times greater than that of copper.

[0024] Furthermore, the first metal layer 212 and the negative electrode current collector foil 22 are made of the same metal material (metal type), and the second metal layer 222 and the positive electrode current collector foil 21 are made of the same metal material (metal type). Therefore, the metal materials used for the positive electrode current collector foil 21 and the negative electrode current collector foil 22 can be used for the first metal layer 212 and the second metal layer 222 respectively, thus simplifying the structure of the bipolar electrode foil 2. For example, in the energy storage device 1 of the embodiment, a metal foil (copper foil) identical to that of the negative electrode current collector foil 22 (copper foil) is bonded to the uncoated portion of the front side 21a of the positive electrode current collector foil 21 (aluminum foil) using a conductive adhesive to form the first metal layer 212. Similarly, in the energy storage device 1 of the embodiment, a metal foil (aluminum foil) identical to that of the positive electrode current collector foil 21 (aluminum foil) is bonded to the uncoated portion of the front side 22a of the negative electrode current collector foil 22 (copper foil) using a conductive adhesive to form the second metal layer 222. Therefore, the coefficient of thermal expansion of the first metal layer 212 is smaller than that of the second metal layer 222.

[0025] In the bipolar electrode foil 2, when current flows and the positive electrode current collector foil 21 and the negative electrode current collector foil 22 heat up, due to the difference in the coefficients of thermal expansion between the positive electrode current collector foil 21 and the negative electrode current collector foil 22, an upward convex warping stress protruding from the positive electrode current collector foil 21 side is generated in the uncoated area. Furthermore, when heat is applied to the first metal layer 212 and the second metal layer 222 via the positive electrode current collector foil 21 and the negative electrode current collector foil 22, due to the difference in the coefficients of thermal expansion between the first metal layer 212 and the second metal layer 222, a downward convex warping stress protruding from the second metal layer 222 side is generated in the uncoated area. Therefore, in the bipolar electrode foil 2, the upward convex warping stress is offset by the downward convex warping stress, and warping of the uncoated area can be suppressed. Therefore, in the energy storage device 1 of the embodiment, warping of the bipolar electrode foil 2, which has a positive electrode current collector foil 21 with a positive electrode active material layer 211 and a negative electrode current collector foil 22 with a negative electrode active material layer 221, can be suppressed. In particular, in the energy storage device 1 of the embodiment, warping and bending of the uncoated portion (peripheral portion) of the bipolar electrode foil 2, which has a positive electrode current collector foil 21 with a positive electrode active material layer 211 formed on the coated portion and a negative electrode current collector foil 22 with a negative electrode active material layer 221 formed on the coated portion, can be suppressed.

Claims

1. An energy storage device comprising an electrode foil, the electrode foil having a first current-collecting foil having a first active material layer formed on a first surface and a second current-collecting foil having a second active material layer formed on a second surface, wherein a third surface of the first current-collecting foil opposite to the first surface and a fourth surface of the second current-collecting foil opposite to the second surface are connected facing each other. Its features are, The energy storage device has: The first metal layer is formed on the portion of the first surface of the first current collector foil where the first active material layer is not formed; and The second metal layer is formed on the portion of the second surface of the second current collector foil where the second active material layer is not formed. The first metal layer and the second metal layer are disposed at a position where they overlap in the thickness direction of the electrode foil. The coefficient of thermal expansion of the first current collector foil is greater than that of the second current collector foil. The coefficient of thermal expansion of the first metal layer is smaller than that of the second metal layer.

2. The energy storage device according to claim 1, characterized in that, The first current-collecting foil and the second metal layer are made of the same type of metal. The second current collector foil is made of the same type of metal as the first metal layer.

3. The energy storage device according to claim 1 or 2, characterized in that, The portion of the first surface on which the first metal layer is formed that does not have the first active material layer is the peripheral portion of the first surface. The portion of the second surface on which the second metal layer is formed that does not have the second active material layer is the peripheral portion of the second surface.

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