Electrode bodies and energy storage devices

Abstract

To provide an electrode body with good volumetric efficiency within the case. [Solution] The electrode unit 25 of the electrode body disclosed herein includes a first electrode sheet 101, a second electrode sheet 102 having a different polarity from the first electrode sheet 101, and a separator 50. The first electrode sheet 101 has a first surface 30a and a second surface 30b. The second electrode sheet 102 has a first opposing portion facing the first surface 30a of the first electrode sheet 101, a second opposing portion 45b facing the second surface 30b, and a connecting portion 46 connecting the first opposing portion and the second opposing portion 45b. The separator 50 has a first sheet portion interposed between the first electrode sheet 101 and the first opposing portion of the second electrode sheet 102, a second sheet portion 55b interposed between the first electrode sheet 101 and the second opposing portion 45b of the second electrode sheet 102, and a third sheet portion 55c covering the outside of the first opposing portion of the second electrode sheet 102.

Description

Technical Field

[0001] The present disclosure relates to an electrode body and a power storage device using the electrode body.

Background Art

[0002] Power storage devices such as lithium-ion secondary batteries, nickel-metal hydride batteries, other secondary batteries, or capacitors are used as power sources for portable devices such as personal computers and mobile terminals, and as high-output power sources for vehicles such as vehicle drive power sources for battery electric vehicles (BEVs). Generally, such power storage devices include an electrode body in which a positive electrode and a negative electrode are laminated via a separator. More specifically, this electrode body is roughly classified into a laminated electrode body and a wound electrode body.

[0003] For example, Japanese Unexamined Patent Application Publication No. 2018-137166 discloses a laminated electrode body in which a plurality of electrode plates are laminated via a separator. Japanese Unexamined Patent Application Publication No. 2016-139596 discloses a wound electrode body wound with a separator interposed between a first electrode and a second electrode.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] In a laminated electrode body as disclosed in Japanese Patent Publication No. 2018-137166, the positive electrode, negative electrode, and separator are separated in all layers. Therefore, in a laminated electrode body, the alignment of each electrode sheet is required, which tends to reduce production efficiency. On the other hand, in a wound electrode body as disclosed in Japanese Patent Publication No. 2016-139596, dead space is created between the electrode body and the case that houses the electrode body. Therefore, in a wound electrode body, the energy density of the energy storage device tends to decrease, and the volumetric efficiency tends to be low.

[0006] In view of the above circumstances, the present invention aims to provide a novel electrode structure with high volumetric efficiency. [Means for solving the problem]

[0007] The electrode body disclosed herein comprises a plurality of electrode units stacked on top of each other. Each electrode unit includes a rectangular first electrode sheet, a rectangular second electrode sheet having a different polarity from the first electrode sheet, and a separator. The first electrode sheet has a first surface and a second surface which is the back surface of the first surface. The second electrode sheet has a first opposing portion that contacts the first surface of the first electrode sheet, a second opposing portion that contacts the second surface of the first electrode sheet, and a connecting portion that connects the first opposing portion and the second opposing portion. The separator has a first sheet portion interposed between the first surface of the first electrode sheet and the first opposing portion of the second electrode sheet, a second sheet portion interposed between the second surface of the first electrode sheet and the second opposing portion of the second electrode sheet, and a third sheet portion that covers the outside of the first opposing portion of the second electrode sheet. Furthermore, the separator has a first bent portion connecting the first sheet portion and the second sheet portion, and a second bent portion connecting the second sheet portion and the third sheet portion.

[0008] With such an electrode body, the overlap of the sheets is reduced at the folded portion of the sheet. This reduces the thickness in the direction perpendicular to the sheet stacking direction. This effect can reduce the dead space that occurs between the case and the electrode body. As a result, the energy density of the energy storage device can be increased and the volumetric efficiency can be improved.

[0009] In one embodiment of the electrode body disclosed herein, the second electrode sheet has an electrode current collector foil and an electrode active material layer formed on the surface of the electrode current collector foil. Furthermore, the electrode current collector foil is exposed at the connecting portion. This makes it possible to further reduce dead space within the case housing the electrode body.

[0010] In one embodiment of the electrode body disclosed herein, an insulating coating is applied to the surface of the electrode current collector foil exposed at the connecting portion. This improves the safety of the electrode body.

[0011] In one embodiment of the electrode body disclosed herein, the separator of the electrode unit is formed in a sheet shape and is a single sheet. This makes it possible to increase the energy density of the energy storage device and further improve the volumetric efficiency.

[0012] In one embodiment of the electrode body disclosed herein, the plurality of electrode units include a first unit in which the first electrode sheet is the positive electrode and the second electrode sheet is the negative electrode, and a second unit in which the first electrode sheet is the negative electrode and the second electrode sheet is the positive electrode. Furthermore, in two adjacent electrode units, the second electrode sheet of the first unit and the second electrode sheet of the second unit face each other via a third sheet portion of one of the electrode units. This ensures that the positive and negative electrodes are well-balanced, enabling efficient charging and discharging.

[0013] One embodiment of an energy storage device disclosed herein comprises an electrode body disclosed herein and a case housing the electrode body.

[0014] In the power storage device of one aspect disclosed herein, the case that houses the electrode body is a rectangular case.

Brief Description of the Drawings

[0015] [Figure 1] FIG. 1 is a perspective view of a power storage device according to one embodiment disclosed herein. [Figure 2] FIG. 2 is a longitudinal sectional view of a power storage device according to one embodiment disclosed herein. [Figure 3] FIG. 3 is a perspective view of an electrode unit according to one embodiment disclosed herein. [Figure 4] FIG. 4 is a developed view of an electrode unit according to one embodiment disclosed herein as viewed in plan from the first electrode sheet side. [Figure 5] FIG. 5 is a developed view of an electrode unit according to one embodiment disclosed herein as viewed in plan from the second electrode sheet side. [Figure 6] FIG. 6 is a longitudinal sectional view of an electrode unit according to one embodiment disclosed herein. [Figure 7] FIG. 7 is a perspective view schematically showing an electrode body in which a plurality of electrode units according to one embodiment disclosed herein are stacked. [Figure 8] FIG. 8 is a diagram schematically showing a state in which a conventional wound electrode body is housed in a case. [Figure 9] FIG. 9 is a diagram schematically showing a state in which a conventional laminated electrode body is housed in a case. [Figure 10] FIG. 10 is a diagram schematically showing a state in which an electrode body according to one embodiment disclosed herein is housed in a power storage device. [[ID=—36]] [Figure 11] FIG. 11 is a longitudinal sectional view of an electrode unit according to another embodiment.

Modes for Carrying Out the Invention

[0016] <Definition of Terms> Hereinafter, one typical embodiment of the electrode body (or electrode unit) in this disclosure will be described in detail with reference to the drawings. Matters other than those specifically mentioned herein but necessary for implementation (e.g., general configuration and manufacturing process of energy storage devices not characterizing this disclosure) can be understood as design matters for those skilled in the art based on the prior art. This disclosure can be implemented based on the contents disclosed herein and common technical knowledge in the art. In the following drawings, the same reference numerals are used to denote members and parts that perform the same function. Also, the dimensional relationships (length, width, thickness, etc.) in each figure do not reflect the actual dimensional relationships.

[0017] In this specification, "energy storage device" is a concept that encompasses devices in which a charge-discharge reaction occurs through the movement of a charge carrier between a pair of electrodes (positive electrode and negative electrode). In other words, energy storage devices include batteries such as secondary batteries (e.g., lithium-ion secondary batteries, nickel-metal hydride batteries, nickel-cadmium batteries) and capacitors (physical batteries) such as lithium-ion capacitors and electric double-layer capacitors. In this specification, this embodiment will be described using a lithium-ion secondary battery, which is one of the typical energy storage devices, as an example. Furthermore, in this specification, "lithium-ion secondary battery" refers to an energy storage device that utilizes lithium ions as a charge carrier and achieves repeated charging and discharging through the movement of charge associated with lithium ions between the positive and negative electrodes.

[0018] In this specification, when a numerical range is described as "A to B (where A and B are arbitrary numbers)," it means "greater than or equal to A and less than or equal to B," and also encompasses the meanings of "greater than A and less than B," "greater than A and less than or equal to B," and "greater than or equal to A and less than B."

[0019] <Energy storage devices> The lithium-ion secondary battery 1 in this embodiment comprises a case 10, an electrode body 20 housed in the case 10, and an electrolyte. Figure 1 is a perspective view of the lithium-ion secondary battery 1 according to one embodiment. Figure 2 is a schematic longitudinal cross-sectional view of the lithium-ion secondary battery 1 along the line II-II in Figure 1. In Figure 2, a portion of the electrode body 20 is shown transparently so that the configuration of the electrode body 20 can be seen. In the following description, the symbols L, R, U, D, F, and Rr in the drawings represent the left, right, top, bottom, front, and back of the lithium-ion secondary battery 1. In the drawings, these are defined as the vertical direction (height direction Y), the horizontal direction (width direction X), and the front-to-back direction (thickness direction Z). However, these are merely directions for the convenience of explanation and do not limit the installation configuration of the lithium-ion secondary battery 1 in any way. For example, in the following description, specific positions and directions such as "top," "bottom," "left," "right," "front," or "back" do not necessarily coincide with the actual positions and directions in implementation.

[0020] <Case> Case 10 is a case that primarily houses the electrode body 20 and the electrolyte (not shown). As shown in Figure 1, in the lithium-ion secondary battery 1 according to this embodiment, the shape of case 10 is a hexahedral box shape. More specifically, the shape of case 10 is a rectangular parallelepiped, or a flattened rectangular shape. Case 10 comprises a main body 11 that houses the electrode body 20 and the electrolyte (not shown), and a sealing plate (lid) 12 that seals the opening of the main body 11. The main body 11 and the sealing plate 12 are sealed by welding, such as by laser welding.

[0021] The material of case 10 can be the same as that used in conventional energy storage devices of this type, and there are no particular restrictions. For example, the material of case 10 may be a lightweight, thermally conductive metal such as aluminum or an aluminum alloy. The thickness of case 10 is not particularly limited. It is also possible to change the configuration of case 10. For example, a flexible laminate film may be used as the case.

[0022] The case 10 is provided with a safety valve 13 and an injection hole (not shown). The safety valve 13 is a thin-walled valve designed to release internal pressure when the internal pressure of the case 10 rises above a predetermined level. The injection hole is a hole for injecting electrolyte. Since the injection hole becomes unnecessary after the electrolyte is injected, it can be sealed by laser welding or the like. Alternatively, the injection hole can be sealed by attaching a plug. In this embodiment, the body 11 of the case 10 is composed of a long rectangular bottom wall 11a, a pair of long sides 11b1, 11b2 and short sides 11c1, 11c2 that extend from the bottom wall 11a and face each other. Here, the sealing plate 12 is provided with the safety valve 13 and the injection hole.

[0023] External positive terminal 14 and negative terminal 15 are provided exposed to the outside of the case 10. These external terminals are electrically connected to the electrode body 20 housed inside the case 10 via the positive terminal internal terminal 16 or the negative terminal internal terminal 17. These external terminals are made of metal. For example, aluminum or an aluminum-based alloy may be used for the positive terminal 14. For example, copper or a copper alloy may be used for the negative terminal 15.

[0024] The positive electrode internal terminal 16 and the negative electrode internal terminal 17 are made of metal. For the positive electrode internal terminal 16, from the viewpoint of improving the bonding strength with the positive electrode tab 31c (or the portion 31a where the positive electrode active material layer is not formed), for example, aluminum or an aluminum alloy may be used. For the negative electrode internal terminal 17, from the viewpoint of improving the bonding strength with the negative electrode tab 41c (or the portion 41a where the negative electrode active material layer is not formed), for example, copper or a copper alloy may be used.

[0025] In this embodiment, the positive external terminal 14 and the negative external terminal 15 are attached to the outside of the sealing plate 12 via a gasket 18. The positive internal terminal 16 and the negative internal terminal 17 are attached to the inside of the sealing plate 12 via an insulator 19. The materials of the gasket 18 and the insulator 19 are not particularly limited. Insulating materials with excellent chemical resistance and weather resistance can be used for the gasket 18 and the insulator 19. For example, resins such as polyfluoroethylene-polyfluoroalkyl vinyl ether copolymer (PFA), polyethylene (PE), polypropylene (PP), and polyphenylene sulfide (PPS) can be used for the gasket 18 and the insulator 19.

[0026] <Electrolyte> The electrolyte can be a non-aqueous electrolyte prepared by dissolving a supporting salt in a suitable non-aqueous solvent. Conventionally known non-aqueous electrolytes can be used without particular limitation. Examples of non-aqueous solvents include carbonates, ethers, esters, sulfones, or lactones. Of these, carbonates are preferred from the viewpoint of improving the performance of the energy storage device. Examples of carbonates include ethylene carbonate (EC), propylene carbonate (PC), diethyl carbonate (DEC), dimethyl carbonate (DMC), and ethyl methyl carbonate (EMC). In addition, lithium salts (e.g., LiBOB, LiPF6, etc.) can be used as an example of a supporting salt.

[0027] <Electrode body> The electrode body 20 disclosed herein comprises a plurality of electrode units 25 stacked on top of each other (see Figure 7). Each electrode unit 25 includes a first electrode sheet 101 consisting of either a positive electrode 30 or a negative electrode 40, a second electrode sheet 102 having a different polarity from the first electrode sheet 101, and a separator 50 (see Figure 6). The first electrode sheet 101 has an electrode current collector foil and an electrode active material layer formed on the surface of the electrode current collector foil. The second electrode sheet 102 has an electrode current collector foil and an electrode active material layer formed on the surface of the electrode current collector foil. Furthermore, the electrode active material layer of the second electrode sheet 102 has a different polarity from the electrode active material layer of the first electrode sheet 101.

[0028] <Electrode Unit> The following describes an example of the configuration of the electrode unit 25. In this embodiment, the first electrode sheet 101 is the positive electrode 30, and the second electrode sheet 102 is the negative electrode 40. However, the electrode unit is not limited to this configuration, and the first electrode sheet may be the negative electrode and the second electrode sheet may be the positive electrode.

[0029] Figure 3 is a perspective view of an electrode unit 25a according to one embodiment disclosed herein. As shown in Figure 3, the electrode unit 25a has a rectangular and flattened shape. The electrode unit 25a has a first side 26a, a second side 26b, a third side 26c opposite the first side 26a, and a fourth side 26d opposite the second side 26b. Here, a positive electrode tab 31c protrudes from the fourth side 26d. Also, a negative electrode tab 41c protrudes from the second side 26b opposite the positive electrode tab 31c. The third side 26c is a side created by folding back the second electrode sheet 102 and the separator 50. At the third side 26c, the second electrode sheet 102 is bent along the connecting portion 46. Also, at the third side 26c, the separator 50 is bent along the first bent portion 56. The first side 26a is the side created by folding the separator 50 along the second folding portion 57. That is, the third side 26c of the electrode unit 25a corresponds to the connecting portion 46 of the second electrode sheet 102 and the first folding portion 56 of the separator 50. Also, the first side 26a of the electrode unit 25a corresponds to the second folding portion 57 of the separator 50.

[0030] Figure 4 is a plan view of the electrode unit 25a according to one embodiment disclosed herein, viewed from the first electrode sheet 101 side. Figure 5 is a plan view of the electrode unit 25 according to one embodiment disclosed herein, viewed from the second electrode sheet 102 side. Figures 4 and 5 show the folded electrode unit 25a (see Figure 3) unfolded. In Figure 4, the second electrode sheet 102 (here, the negative electrode 40), the separator 50, and the first electrode sheet 101 (here, the positive electrode 30) are shown stacked from back to front in this order. Therefore, in Figure 4, the positive electrode 30 is shown on the outermost surface (closest to the viewer). In Figure 5, the negative electrode 40, the separator 50, and the positive electrode 30 are shown stacked from front to back in this order. Figure 4 is a view of Figure 5 from the opposite side.

[0031] <Positive electrode> As shown in Figure 4, the positive electrode 30 contained in one electrode unit 25a is formed in a rectangular shape and is a single piece. The positive electrode 30 has a first surface 30a (the front surface) and a second surface 30b which is the back surface of the first surface 30a. The first surface 30a of the positive electrode 30 is the surface that is visible on the outermost surface (closest to the viewer) in Figure 4.

[0032] The positive electrode 30 comprises a rectangular positive electrode current collector foil 31 and a positive electrode active material layer 32 formed on the surface of the positive electrode current collector foil 31. The positive electrode active material layer 32 contains a positive electrode active material that can reversibly absorb and release charge carriers (in this case, lithium ions), that is, it can release charge carriers during charging and absorb charge carriers during discharge. The positive electrode active material layer 32 may be formed on one side or both sides (in this case, both sides) of the positive electrode current collector foil 31. Also, as shown in Figure 4, the positive electrode 30 may have a portion 31a where the positive electrode active material layer 32 is not formed and the positive electrode current collector foil 31 is exposed. The portion 31a where the positive electrode active material layer is not formed is provided at one end of the electrode unit 25. In this embodiment, a positive electrode tab 31c is provided on the portion 31a where the positive electrode active material layer is not formed. The positive electrode tab 31c is provided so as to protrude in the width direction when the electrode unit 25 is folded. When multiple electrode units 25 are stacked, the positive electrode tabs 31c of each unit are positioned in predetermined locations so that they align when stacked. The positive electrode internal terminals 16 can be joined to the positive electrode tabs 31c. In addition, a positive electrode protective layer 31b is provided on the edge of the positive electrode active material layer 32, on the positive electrode current collector foil 31 (more specifically, the portion 31a where the positive electrode active material layer is not formed). The positive electrode protective layer 31b is a layer that protects the portion 31a where the positive electrode active material layer is not formed, and may be a layer containing an inorganic filler (e.g., alumina).

[0033] The material of the positive electrode current collector foil 31 may be any known positive electrode current collector foil 31 used in energy storage devices, and is not particularly limited. The material of the positive electrode current collector foil 31 is, for example, aluminum or an aluminum alloy. As the positive electrode active material of the positive electrode active material layer 32, a positive electrode active material used in the positive electrode of a general lithium-ion secondary battery can be used. Specifically, the positive electrode active material is a lithium composite metal oxide such as a layered rock salt structure, spinel structure, or olivine structure. Lithium composite metal oxides include LiCoO2, LiNiO2, LiFeO2, LiNi x Co y Mn 1-x-y O2(NCM), LiNi 0.5 Mn 1.5 O4, LiSa 0.8 Co 0.15 Al 0.05 Examples include O2(NCA), LiCrMO4, LiMn2O4, and LiFePO4(LFP). These positive electrode active materials may be used individually or in combination of two or more. Of these, NCM is preferred as the positive electrode active material from the viewpoint of improving the cycle characteristics of the energy storage device. The positive electrode active material layer 32 may contain various additives such as binders, conductive additives, inorganic fillers, or thickeners.

[0034] The thickness of the positive electrode current collector foil 31 is not particularly limited. From the viewpoint of the strength of the electrode current collector foil, the lower limit of the thickness of the positive electrode current collector foil 31 is preferably 5 μm or more, more preferably 8 μm or more, and even more preferably 10 μm or more. From the viewpoint of the capacity density of the electrode unit, the upper limit of the thickness of the positive electrode current collector foil 31 is preferably 50 μm or less, more preferably 35 μm or less, and even more preferably 20 μm or less. Furthermore, the thickness (film thickness) of one side of the positive electrode active material layer 32 is not particularly limited. From the viewpoint of the capacity density of the electrode unit, the lower limit of the thickness of one side of the positive electrode active material layer 32 is preferably 30 μm or more, more preferably 35 μm or more, and even more preferably 50 μm or more. From the viewpoint of making the electrode unit thinner, the upper limit of the thickness of one side of the positive electrode active material layer 32 is preferably 90 μm or less, more preferably 80 μm or less, and even more preferably 70 μm or less.

[0035] <Negative electrode> As shown in Figure 5, the negative electrode 40 included in one electrode unit 25a is formed in a rectangular shape and is a single piece. The negative electrode 40 has a first surface 40a (front surface) and a second surface 40b which is the back surface of the first surface 40a. In Figure 5, the surface that is visible on the outermost surface (closest to the viewer) is the second surface 40b of the negative electrode 40. The negative electrode 40 has a first opposing portion 45a that is in contact with the first surface 30a of the positive electrode 30 and a second opposing portion 45b that is in contact with the second surface 30b of the positive electrode 30 (see Figure 6). The negative electrode 40 has a connecting portion 46 that connects the first opposing portion 45a and the second opposing portion 45b. The connecting portion 46 is the boundary between the first opposing portion 45a and the second opposing portion 45b.

[0036] The negative electrode 40 comprises a rectangular negative electrode current collector foil 41 and a negative electrode active material layer 42 formed on the surface of the negative electrode current collector foil 41. The negative electrode active material layer 42 contains a negative electrode active material that can reversibly absorb and release charge carriers (in this case, lithium ions), that is, it can absorb charge carriers during charging and release charge carriers during discharge. The negative electrode active material layer 42 may be formed on one side or both sides (in this case, both sides) of the negative electrode current collector foil 41. Furthermore, as shown in Figure 5, the negative electrode 40 may have a portion 41a where the negative electrode active material layer 42 is not formed and the negative electrode current collector foil 41 is exposed. The portion 41a where the negative electrode active material layer is not formed is provided at one end of the electrode unit 25a. In this embodiment, two negative electrode tabs 41c are intermittently provided in the portion 41a where the negative electrode active material layer is not formed at predetermined positions along the longitudinal direction of the negative electrode 40. The two negative electrode tabs 41c protrude in the width direction of the electrode unit 25a when the electrode unit 25a is folded. The two negative electrode tabs 41c shown in Figure 3 are positioned in predetermined locations so that they are aligned when the electrode unit 25a is folded. The negative electrode internal terminals 17 can be connected to the negative electrode tabs 41c.

[0037] The material of the negative electrode current collector foil 41 is not particularly limited and may be any known negative electrode current collector foil used in energy storage devices. For example, the material of the negative electrode current collector foil 41 may be copper or a copper alloy. As the negative electrode active material of the negative electrode active material layer 42, a negative electrode active material used in the negative electrode of a general lithium-ion secondary battery can be used. Specifically, examples of negative electrode active materials include carbon materials such as soft carbon (easily graphitizable carbon), amorphous carbon materials, graphite, hard carbon (difficult to graphitize carbon), and carbon nanotubes; metal oxide materials such as silicon oxide, titanium oxide, vanadium oxide, and lithium titanium composite oxide; metal nitride materials such as lithium nitride and lithium cobalt composite nitride; and silicon compounds. These negative electrode active materials may be used individually or in combination of two or more. Of these, graphite is preferred as the negative electrode active material from the viewpoint of improving energy density. The negative electrode active material layer 42 may also contain various additives such as binders, conductive additives, inorganic fillers, or thickeners.

[0038] The thickness of the negative electrode current collector foil 41 is not particularly limited. From the viewpoint of the strength of the electrode current collector foil, the lower limit of the thickness of the negative electrode current collector foil 41 is preferably 3 μm or more, more preferably 5 μm or more, and even more preferably 8 μm or more. From the viewpoint of the capacity density of the electrode unit, the upper limit of the thickness of the negative electrode current collector foil 41 is preferably 40 μm or less, more preferably 25 μm or less, and even more preferably 15 μm or less. Furthermore, the thickness (film thickness) of one side of the negative electrode active material layer 42 is not particularly limited. From the viewpoint of the capacity density of the electrode unit, the lower limit of the thickness of one side of the negative electrode active material layer 42 is preferably 50 μm or more, more preferably 55 μm or more, and even more preferably 60 μm or more. From the viewpoint of making the electrode unit thinner, the upper limit of the thickness of one side of the negative electrode active material layer 42 is preferably 100 μm or less, more preferably 90 μm or less, and even more preferably 80 μm or less.

[0039] <Separator> As shown in Figures 4 and 5, the separator 50 included in one electrode unit 25a is formed in the shape of a rectangular sheet and is a single sheet. The separator 50 has a first surface 50a (the front surface) and a second surface 50b which is the back surface of the first surface 50a. The separator 50 also has a first sheet portion 55a interposed between the first surface 30a of the positive electrode 30 and the first opposing portion 45a of the negative electrode 40, and a second sheet portion 55b interposed between the second surface 30b of the positive electrode 30 and the first opposing portion 45a of the negative electrode 40 (see Figure 6). The separator 50 has a third sheet portion 55c that covers the outside (second surface 40b) of the first opposing portion 45a of the negative electrode 40 (in other words, the third sheet portion 55c and the second surface 40b of the first opposing portion 45a of the negative electrode 40 are in contact) (see Figure 6). Furthermore, the separator 50 has a first bent portion 56 that connects the first sheet portion 55a and the second sheet portion 55b, and a second bent portion 57 that connects the second sheet portion 55b and the third sheet portion 55c. The first bent portion 56 is the boundary between the first sheet portion 55a and the second sheet portion 55b. The second bent portion 57 is the boundary between the second sheet portion 55b and the third sheet portion 55c.

[0040] The separator 50 according to this embodiment is porous and has insulating properties. Since the separator 50 insulates the positive electrode 30 and the negative electrode 40, the dimensions of the separator 50 are larger than those of the positive electrode 30 and the negative electrode 40. The material of the separator 50 may be a known separator used in energy storage devices and is not particularly limited. For example, the material of the separator 50 can preferably be a polyolefin such as polyethylene or polypropylene, polyester, cellulose, or a resin such as polyamide. Furthermore, the surface of the separator 50 may be provided with a heat-resistant layer, as long as it does not significantly impair the effects of the technology according to this disclosure.

[0041] The thickness (film thickness) of the separator 50 is not particularly limited. From the viewpoint of the strength of the separator 50, the lower limit of the thickness of the separator 50 is preferably 5 μm or more, more preferably 8 μm or more, and even more preferably 12 μm or more. From the viewpoint of the capacitance density of the electrode unit, the upper limit of the thickness of the separator 50 is preferably 40 μm or less, more preferably 30 μm or less, and even more preferably 20 μm or less.

[0042] As shown in FIG. 4, in the unfolded state, the positive electrode 30 is disposed on the second surface b of the second sheet portion 55b of the separator 50. As shown in FIGS. 4 and 5, the first sheet portion 55a of the separator 50 is disposed on the first surface 40a of the first opposing portion 45a of the negative electrode 40. Further, the second sheet portion 55b of the separator 50 is disposed on the first surface 40a of the second opposing portion 45b of the negative electrode 40. That is, in the electrode unit 25a before being folded, the second opposing portion 45b of the negative electrode 40, the second sheet portion 55b of the separator 50, and the positive electrode 30 are disposed overlapping each other.

[0043] In the present embodiment, as shown in FIGS. 4 and 5, the width Ln of the negative electrode active material layer 42 is formed wider than the width Lp of the positive electrode active material layer 32, for example. The width Ls of the separator 50 is formed wider than the negative electrode active material layer 42. That is, as shown in FIGS. 4 and 5, Lp < Ln < Ls. Thereby, at the time of charging, charge carriers (here, lithium ions) can be more reliably occluded in the negative electrode 40. However, the relationship between the widths of the positive electrode 30 and the negative electrode 40 is not limited to this. The relationship between the respective widths may be Ln < Lp < Ls. Further, when the electrode unit 25a is folded, the positive electrode tab 3lc of the positive electrode current collector foil 31 and the negative electrode tab 41c of the negative electrode current collector foil 41 are provided so as to protrude from the separator 50 toward opposite sides in the width direction. The positive electrode protective layer 41b faces the edge of the negative electrode 40 on the side opposite to the side where the negative electrode tab 41c is provided, via the separator 50. As shown in FIG. 2, the positive electrode tab 31c protrudes from one side of the electrode body 20. Further, the negative electrode tab 41c protrudes from the other side of the electrode body 20.

[0044] <Assembly of electrode unit> An example of how to transform the electrode unit 25a from the unfolded state (in other words, before folding) shown in Figure 4 to the folded state shown in Figure 3 will be described. First, each sheet is arranged as shown in Figure 4. The separator 50 is folded towards the front along the first folding portion 56 so as to enclose the positive electrode 30. As a result, the positive electrode 30 is positioned inside the separator 50. Therefore, the positive electrode 30 and the negative electrode 40 do not come into direct contact, thus avoiding a short circuit. The negative electrode 40 is also folded towards the front along the connecting portion 46 so as to enclose the first sheet portion 55a of the separator 50, the positive electrode 30, and the second sheet portion 55b of the separator 50. It is then folded towards the front along the second folding portion 57 of the separator 50. As a result, the third sheet portion 55c can cover the first opposing portion 45a of the negative electrode 40. Thus, the negative electrode 40 is folded only once along the connecting portion 46. The separator 50 is folded once along the first folding portion 56 and once along the second folding portion 57 (a total of two times). The positive electrode 30 is not folded even once during the formation of the electrode unit 25. Note that the folding method of the electrode unit 25a described here is merely one example. As long as it is possible to create the electrode unit of this disclosure, the arrangement of each sheet before folding and the folding direction can be changed as appropriate.

[0045] <Electrode Unit Configuration> Figure 6 is a longitudinal cross-sectional view of an electrode unit 25 according to one embodiment disclosed herein. Figure 6 schematically shows a cross-section along the line VI-VI in Figure 3. As shown in Figure 6, the first surface 30a of the positive electrode 30 faces in the Rr direction. The second surface 30b of the positive electrode 30 faces in the F direction. The first surface 40a of the negative electrode 40 faces inward (towards the center of the electrode unit 25a) when the electrode unit 25a is folded. The second surface 40b of the negative electrode 40 faces outward when the electrode unit 25a is folded. The first surface 50a of the separator 50 is the surface that faces inward when the electrode unit 25a is folded. The second surface 50b of the separator 50 is the surface that faces outward when the electrode unit 25a is folded. In this specification, "inside" with respect to the electrode unit refers to the side that faces in the direction approaching the center of the electrode unit. In relation to the electrode unit, "outside" refers to the side facing away from the center of the electrode unit. Furthermore, "center" in relation to the electrode unit refers to the center of the first electrode sheet.

[0046] As shown in Figure 6, the positive electrode 30 is positioned on the innermost side of the electrode unit 25a without being bent. The negative electrode 40 is bent along the connecting portion 46 to divide it into a first opposing portion 45a and a second opposing portion 45b. The separator 50 is also bent along the first bending portion 56 to divide it into two continuous regions (first sheet portion 55a and second sheet portion 55b). The separator 50 is also bent along the second bending portion 57 to divide it into a second sheet portion 55b and a third sheet portion 55c. In other words, the separator 50 is bent along the first bending portion 56 and the second bending portion 57 to divide it into three continuous regions (first sheet portion 55a, second sheet portion 55b, and third sheet portion 55c).

[0047] As shown in Figure 6, the positive electrode 30 is sandwiched between the first sheet portion 55a and the second sheet portion 55b of the separator 50. The first surface 30a of the positive electrode 30 is in contact with the first surface 50a of the first sheet portion 55a of the separator 50. The second surface 30b of the positive electrode 30 is in contact with the first surface 50a of the second sheet portion 55b of the separator 50. The negative electrode 40 sandwiches the positive electrode 30 via the separator 50. That is, the first surface 30a of the positive electrode 30 and the first surface 40a of the first opposing portion 45a of the negative electrode 40 are in contact via the first sheet portion 55a of the separator 50. Also, the first surface 40a of the first opposing portion 45a of the negative electrode 40 and the second surface 50b of the first sheet portion 55a of the separator 50 are in contact. Specifically, the second surface 30b of the positive electrode 30 and the first surface 40a of the second opposing portion 45b of the negative electrode 40 face each other via the second sheet portion 55b of the separator 50. The first surface 40a of the second opposing portion 45b of the negative electrode 40 and the second surface 50b of the second sheet portion 55b of the separator 50 are in contact. The first opposing portion 45a of the negative electrode 40 is sandwiched between the first sheet portion 55a and the third sheet portion 55c of the separator 50. The second surface 40b of the first opposing portion 45a of the negative electrode 40 and the first surface 50a of the third sheet portion 55c of the separator 50 are in contact. The second surface 40b of the second opposing portion 45b of the negative electrode 40 is exposed to the outside of the electrode unit 25a. The second surface 50b of the third sheet portion 55c of the separator 50 is located outside the electrode unit 25a.

[0048] The thickness of the electrode unit 25a is not particularly limited, as long as it does not significantly impair the effects of the technology of this disclosure. From the viewpoint of the capacity density of the electrode unit, the lower limit of the thickness of the electrode unit 25a is preferably 248 μm or more, more preferably 295 μm or more, and even more preferably 344 μm or more. From the viewpoint of reducing the thickness of the electrode unit, the upper limit of the thickness of the electrode unit 25a is preferably 830 μm or less, more preferably 695 μm or less, and even more preferably 570 μm or less.

[0049] <Lamination of electrode units> An electrode body 20 can be constructed by stacking multiple electrode units 25. Each electrode unit 25 consists of a single positive electrode 30, a negative electrode 40, and a separator 50. Therefore, the electrode unit 25 is thinner than a conventional laminated electrode body 200 or wound electrode body 210. Furthermore, the electrode unit 25 of this embodiment can function as an energy storage device on its own. For this reason, the electrode unit 25 can be inserted into the gap between the case 10 and the electrode body in the stacking direction of the electrode body (see Figures 9, 10, and 11). This eliminates dead space by filling the gap between the case 10 and the electrode body. Therefore, the electrode unit 25 can be suitably used to adjust the gap between the case 10 and the electrode body. Moreover, the configuration of the electrode body 20 is not limited to a configuration in which multiple electrode units 25 are stacked. The electrode unit disclosed herein may be used in combination with a conventional laminated electrode body 200 or wound electrode body 210. In other words, the electrode body may comprise a stacked electrode body 200 and / or a wound electrode body 210 and at least one electrode unit. This allows the gaps in the stacking direction (here, the thickness direction Z) within the case 10 to be filled, thereby increasing the capacity of the energy storage device.

[0050] The number of electrode units 25 included in the electrode body 20 is not particularly limited. As described above, the electrode unit 25 of this embodiment can function as an energy storage device on its own, so the number of electrode units 25 included in the electrode body 20 may be as small as one. The number of electrode units 25 included in the electrode body 20 can be appropriately set depending on the purpose of use, the size of the case 10, etc. The number of electrode units 25 included in the electrode body 20 may be five or more, and from the viewpoint of increasing the capacity of the energy storage device, ten or more is preferable, twenty or more is more preferable, and thirty or more is even more preferable.

[0051] Figure 7 is a schematic perspective view showing an electrode body 20 in which a plurality of electrode units are stacked according to one embodiment disclosed herein. The electrode body 20 is formed by arranging a plurality of electrode units in the stacking direction. In Figure 7, the electrode units are shown separated from each other so that the stacked state can be seen. As shown in Figure 7, in this embodiment, the electrode body 20 is constructed by alternately stacking first units 25a and second units 25b. The first unit 25a has the same configuration as the electrode unit 25a described above.

[0052] In this embodiment, in two adjacent electrode units, one electrode unit (first unit 25a) is laminated such that the first electrode sheet 101 is the positive electrode 30, and the other (second unit 25b) is laminated such that the first electrode sheet 101 is the negative electrode 40. More specifically, the electrode body 20 of this embodiment includes a first unit 25a in which the first electrode sheet 101 is the positive electrode 30 and the second electrode sheet 102 is the negative electrode 40. The electrode body 20 also includes a second unit 25b in which the first electrode sheet 101 is the negative electrode 40 and the second electrode sheet 102 is the positive electrode 30. In the two adjacent electrode units, the second electrode sheet 102 of the first unit 25a and the second electrode sheet 102 of the second unit 25b face each other via the third sheet portion 55c of the separator 50 of one of the electrode units. This ensures that the positive electrode 30 and the negative electrode 40 are well-balanced in the electrode body 20, allowing for efficient charging and discharging. The arrangement of the electrode units is not limited to stacking them alternately as described above. The electrode body may consist of stacking only the first unit 25a, or only the first unit 25a. Alternatively, the first unit 25a and the second unit 25b may be randomly selected and stacked. The number of first units 25a and second units 25b in the electrode body 20 may be equal, or there may be a bias towards one or the other.

[0053] As shown in Figure 7, in the electrode body 20, the second unit 25b is stacked on top of the first unit 25a, and the first unit 25a is stacked on top of the second unit 25b. The electrode body 20 is formed by alternately stacking the first unit 25a and the second unit 25b up to a predetermined number. As shown in Figure 7, the second unit 25b is stacked on the second surface 40b of the second opposing portion 45b of the negative electrode 40 of the first unit 25a. The second unit 25b is in contact with the second surface 40b of the second opposing portion 45b of the negative electrode 40 of the first unit 25a by the second surface 50b of the third sheet portion 55c of the separator 50. In this way, the first electrode sheet 101 of the first unit 25a (the negative electrode 40 of the first unit 25a) and the second electrode sheet 102 of the second unit 25b (the positive electrode 30 of the second unit 25b) are stacked via the third sheet portion 55c of the separator 50 of the second unit 25b. This allows for efficient exchange of charge carriers (in this case, lithium ions) between the first unit 25a and the second unit 25b. Similarly, the first unit 25a is stacked on top of the second unit 25b. The first unit 25a is stacked on the second surface 40b of the second opposing portion 45b of the positive electrode 30 of the second unit 25b. The first unit 25a is in contact with the second surface 40b of the second opposing portion 45b of the positive electrode 30 of the second unit 25b via the second surface 50b of the third sheet portion 55c of the separator 50. In this way, the first electrode sheet 101 of the second unit 25b (the positive electrode 30 of the second unit 25b) and the second electrode sheet 102 of the first unit 25a (the negative electrode 40 of the first unit 25a) are laminated together via the third sheet portion 55c of the separator 50 of the first unit 25a.

[0054] As shown in Figure 7, the electrode active material layer is exposed at the top of the electrode body 20. Here, the second surface 40b of the second opposing portion 45b of the negative electrode 40 of the first unit 25a is exposed. Therefore, it is preferable to cover the second electrode sheet 102 (in this case, the second surface 40b of the second opposing portion 45b of the negative electrode 40 of the first unit 25a) that is exposed at least at the top of the electrode body 20 with the separator 60. This improves the safety of the electrode body 20. The separator 60 may be made of the same material as the separator 50 used in the electrode unit 25.

[0055] When stacking multiple electrode units (first unit 25a and / or second unit 25b), it is preferable that the electrode tabs (positive electrode tab 31c or negative electrode tab 41c) of each electrode unit protrude in the same direction. As shown in Figure 7, the positive electrode tab 31c protrudes in the L direction. The negative electrode tab 41c protrudes in the R direction opposite to the positive electrode tab 31c. In addition, the electrode tabs are aligned along the stacking direction (thickness direction Z) of the electrode units. This makes it easier to weld the electrode tabs together.

[0056] <Effects of this embodiment> The electrode body 20 with the above configuration reduces dead space within the case 10 and improves the volumetric efficiency of the electrode body 20 in the energy storage device (lithium-ion secondary battery 1). The following explanation will be given in comparison with conventional electrode bodies.

[0057] First, the wound electrode body 300 shown in Figure 8 is manufactured by winding a strip-shaped positive electrode 303, a negative electrode 304, and separators 305a and 305b. Therefore, the wound electrode body 300 has a pair of opposing flat sections 306 and a corner section 307 connecting the pair of flat sections 306. This corner section 307 has a very large outer surface with a radius of curvature equal to the thickness of the wound electrode body 300. As a result, a very large dead space 308 is created between the four corners of the case 10 and the corner section 307. Consequently, the volumetric efficiency of the electrode body in the energy storage device is greatly reduced. On the other hand, the laminated electrode body 200 shown in Figure 9 is made by alternately stacking short positive electrodes 203, negative electrodes 204, and separators 205. Since this laminated electrode body 200 does not have large corner sections, it does not have the dead space 308 that occurs in the wound electrode body 300 (see Figure 8). However, in the fabrication of the laminated electrode body 200, it is necessary to precisely align each sheet component, which tends to reduce production efficiency.

[0058] In contrast, the second electrode sheet 102 of the electrode body 20 according to this embodiment, as shown in Figure 6, has a first opposing portion 45a that contacts the first surface 30a of the first electrode sheet 101, a second opposing portion 45b that contacts the second surface 30b of the first electrode sheet 101, and a connecting portion 46 that connects the first opposing portion 45a and the second opposing portion 45b. In other words, in this embodiment, a short first electrode sheet 101 is sandwiched between a second electrode sheet 102 that is longer than the first electrode sheet 101. By adopting this configuration, a connecting portion 46 with a significantly smaller radius of curvature is formed compared to the corner portion 307 of a conventional wound electrode body 300. Similarly, in the electrode body 20 according to this embodiment, the second bent portion 57 of the separator 50 also has a significantly smaller radius of curvature compared to the corner portion 307 of a conventional wound electrode body 300. In other words, in this embodiment, the electrode unit 25a has a very small radius of curvature at both side edges (connecting portion 46, second bent portion 57). Furthermore, as shown in Figure 10, stacking multiple such electrode units 25a prevents the occurrence of dead space (see reference numeral 308 in Figure 8) between the four corners of the case 10 and the electrode body 20. Moreover, in this embodiment, the electrode unit 25a is manufactured by bending the first electrode sheet 101, the second electrode sheet 102, and the separator 50 while interlocking them with each other. This significantly improves production efficiency compared to a stacked electrode body where all sheets need to be aligned.

[0059] Furthermore, although not limiting the technologies disclosed herein, in this embodiment, the negative electrode current collector foil 41 is exposed at the connecting portion 46 of the negative electrode 40 (second electrode sheet 102). By not applying the negative electrode active material layer 42 to the connecting portion 46 in this way, the radius of curvature of the connecting portion 46 can be further reduced. As a result, the dead space between the case 10 and the electrode body 20 can be further reduced, and the volumetric efficiency can be improved.

[0060] As shown in Figure 8, in the electrode body 20, the electrode unit located at one end in the stacking direction (here, the topmost part) (here, the first electrode unit 25) has the second sheet portion of the second electrode sheet (here, the second surface 40b of the negative electrode 40) exposed. Therefore, it is preferable to place a separator 60 consisting of one surface in contact with the second sheet portion 40b of the negative electrode 40 at the topmost part of the first electrode unit 25. This prevents the electrode located at one end of the electrode body 20 from being exposed, thereby improving safety.

[0061] <Other Embodiments> Although preferred embodiments of this disclosure have been described above based on the drawings, this description is not limiting, and various modifications are of course possible.

[0062] <Electrode body of one electrode unit> As described above, the electrode unit 25 has a pair of electrodes (i.e., a positive electrode 30 and a negative electrode 40) and a separator 50, and therefore can generate a charge-discharge reaction even with just one unit. For this reason, if even one electrode unit 25 is housed in the case 10, it can function as a lithium-ion secondary battery 1. Accordingly, the electrode body 20 may be composed of at least one electrode unit 25.

[0063] <Insulating coating> In other embodiments of the electrode body disclosed herein, an insulating coating 24 is applied to the electrode unit 25c. Figure 11 is a longitudinal cross-sectional view of the electrode unit 25c according to another embodiment. In the electrode unit 25c, the first electrode sheet 101 is the positive electrode 30, and the second electrode sheet 102 is the negative electrode 40. As shown in Figure 11, in the electrode unit 25c, the electrode current collector foil is exposed at the connecting portion 46 of the negative electrode 40. The insulating coating 24 is applied to the surface of the electrode current collector foil exposed at the connecting portion 46 of the negative electrode 40. That is, the connecting portion 46 has an insulating coating layer. This improves the safety of the electrode unit 25c. The insulating coating 24 includes an insulating material. The insulating material is not particularly limited as long as it does not significantly impair the effects of the technology of this disclosure. Examples of insulating materials include resins and ceramics. Examples of ceramics include barium titanate (BaTiO3) and aluminum oxide (Al2O3). Typically, conventionally known methods such as sputtering can be used for coating. However, insulation can be achieved not only through coating, but also by applying insulating tape or separators.

[0064] Furthermore, as shown in Figure 12, the electrode unit 25c has the electrode current collector foil exposed on the second surface 40b of the second opposing portion 45b of the negative electrode 40. The insulating coat 24 is also applied to the surface of the electrode current collector foil that is exposed on the second surface 40b of the second opposing portion 45b of the negative electrode 40. This improves the safety of the electrode unit 25c. However, it is preferable to place such an electrode unit 25c at the end of the electrode body (the topmost in the stacking direction, see Figure 7). When electrode units are stacked, the electrode active material layer of the second electrode sheet 102 becomes exposed at one end (the topmost). Therefore, it is preferable to place an electrode unit 25c at one end of the electrode body in which the electrode current collector foil is exposed and an insulating coat is applied to the surface of the exposed electrode current collector foil. This further improves the safety of the electrode body.

[0065] The technologies disclosed herein may be omitted or combined as appropriate, unless no particular problems arise. Furthermore, this specification includes the disclosures described in the following sections.

[0066] Item 1: An electrode body for an energy storage device, comprising a plurality of electrode units stacked on top of each other, each of the electrode units including a rectangular first electrode sheet, a rectangular second electrode sheet having a different polarity from the first electrode sheet, and a separator, the first electrode sheet having a first surface and a second surface which is the back surface of the first surface, the second electrode sheet having a first opposing portion that contacts the first surface of the first electrode sheet opposite to it, and a second opposing portion that contacts the second surface of the first electrode sheet opposite to it, and the first opposing portion and the second An electrode body having a connecting portion that connects two opposing portions, wherein the separator has a first sheet portion interposed between the first surface of the first electrode sheet and the first opposing portion of the second electrode sheet, a second sheet portion interposed between the second surface of the first electrode sheet and the second opposing portion of the second electrode sheet, a third sheet portion that covers the outside of the first opposing portion of the second electrode sheet, a first bent portion that connects the first sheet portion and the second sheet portion, and a second bent portion that connects the second sheet portion and the third sheet portion.

[0067] Item 2: The electrode body according to Item 1, wherein the second electrode sheet comprises an electrode current collector foil and an electrode active material layer formed on the surface of the electrode current collector foil, and the electrode current collector foil is exposed at the connecting portion.

[0068] Item 3: The electrode body according to Item 2, wherein an insulating coating is applied to the surface of the electrode current collector foil exposed at the above-mentioned connecting portion.

[0069] Item 4: The electrode body according to any one of items 1 to 3, wherein the separator is formed in a sheet and is a single sheet.

[0070] Item 5: The above-mentioned multiple electrode units are, A first unit in which the first electrode sheet is the positive electrode and the second electrode sheet is the negative electrode, A second unit in which the first electrode sheet is the negative electrode and the second electrode sheet is the positive electrode, Includes, The electrode body according to any one of claims 1 to 4, wherein in two adjacent electrode units, the second electrode sheet of the first unit and the second electrode sheet of the second unit face each other via a third sheet portion of one of the electrode units.

[0071] Item 6: An electrode body described in any one of items 1 to 5, A case for housing the electrode body, A power storage device having the following features.

[0072] Item 7: The energy storage device according to Item 6, wherein the case housing the electrode body is rectangular. [Explanation of Symbols]

[0073] 1. Lithium-ion rechargeable battery 10 cases 11 Main unit 11a Bottom wall 11b1, 11b2 long side 11c1, 11c2 short side 12 Sealing plate 13 Safety valve 14 Positive external terminal 15 Negative external terminal 16 Positive internal terminal 17 Negative internal terminal 18 Gaskets 19 Insulators 20 Electrode body 24 Insulating coating layer 25 Electrode Units 25a Unit 1 25b Unit 2 25c electrode unit 26a First side 26b Second side 26c Third side 26d Fourth side 30 positive electrode 30a 1st page 30b 2nd side 31 Positive electrode current collector foil 31a Portion where positive electrode active material layer is not formed 31b Positive electrode protective layer 31c positive electrode tab 32 Positive electrode active material layer 40 negative electrode 40a Page 1 40b 2nd side 41 Negative electrode current collector foil 41a Part where negative electrode active material layer is not formed 41c Negative Electrode Tab 42 Negative electrode active material layer 45a 1st opposing part 45b 2nd opposing part 46 Connecting part 50 Separators 50a Page 1 50b 2nd side 55a First sheet section 55b Second Sheet Section 55c Third seat section 56 First folding section 57 Second folding section 60 Separators 101 First electrode sheet 102 Second electrode sheet 200 Stacked Electrode Body 203 Positive electrode 204 Negative electrode 205 Separator 300-wound electrode body 303 Positive electrode 304 negative electrode 305a, 305b Separators 306 Flat area 307 Corner section 308 Dead space

Claims

1. An electrode body for an energy storage device, It has multiple electrode units stacked on top of each other, Each of the electrode units is A rectangular first electrode sheet, A rectangular second electrode sheet with a different polarity from the first electrode sheet, Separator and, Includes, The first electrode sheet is It has a first surface and a second surface which is the reverse side of the first surface, The second electrode sheet is A first opposing portion that is in contact with the first surface of the first electrode sheet, A second opposing portion that is in contact with the second surface of the first electrode sheet, It has a connecting portion that connects the first opposing portion and the second opposing portion, The aforementioned separator is, Interposed between the first surface of the first electrode sheet and the first opposing portion of the second electrode sheet One sheet section, Interposed between the second surface of the first electrode sheet and the second opposing portion of the second electrode sheet Two sheet sections, A third sheet portion covering the outside of the first opposing portion of the second electrode sheet, A first folded portion connecting the first sheet portion and the second sheet portion, An electrode body having a second sheet portion and a second bent portion connecting the third sheet portion.

2. The second electrode sheet is Electrode current collector foil, The electrode current collector foil has an electrode active material layer formed on its surface, The electrode body according to claim 1, wherein the electrode current collector foil is exposed at the connecting portion.

3. The electrode body according to claim 2, wherein an insulating coating is applied to the surface of the electrode current collector foil exposed at the connecting portion.

4. The electrode body according to claim 1, wherein the separator is formed in a sheet shape and is a single sheet.

5. The plurality of electrode units are, A first unit in which the first electrode sheet is the positive electrode and the second electrode sheet is the negative electrode, A second unit in which the first electrode sheet is the negative electrode and the second electrode sheet is the positive electrode, Includes, The electrode body according to claim 1, wherein in two adjacent electrode units, the second electrode sheet of the first unit and the second electrode sheet of the second unit face each other via a third sheet portion of one of the electrode units.

6. An electrode body according to any one of claims 1 to 5, A case for housing the electrode body, A power storage device having the following features.

7. The energy storage device according to claim 6, wherein the case housing the electrode body is rectangular in shape.

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