Energy storage devices and energy storage modules

Abstract

To provide an energy storage device with improved external strength. [Solution] The energy storage device disclosed herein comprises an electrode body having a positive electrode and a negative electrode, and a metal casing 10 housing the electrode body. The casing 10 is wound with continuous fibers 60 arranged in a predetermined direction so as to cover its outer surface.

Description

Technical Field

[0001] The present disclosure relates to a power storage device and a power storage module including the power storage device.

Background Art

[0002] International Publication No. WO2018 / 168549 discloses a all-solid-state secondary battery having a cylindrical battery element member including a current collector, a solid electrolyte layer, and a positive electrode active material layer, an axis around which the battery element member is disposed on the outer periphery of the side surface, and a battery exterior body that houses the battery element member and the axis. A reinforcing cover is provided on the outer periphery of the side surface of the battery exterior body of such an all-solid-state secondary battery. This reinforcing cover is arranged to press the battery exterior body inward so as to have a compressive stress of 0.5 MPa or more between the axis and the battery element member and between the battery exterior body and the battery element member. Thereby, expansion of the battery exterior body can be suppressed.

[0003] Further, Japanese Patent Application Laid-Open No. 2020-155356 discloses a method for manufacturing a case in which carbon fiber impregnated with resin is wound following a mold (mandrel) for the case. The case manufactured by such a manufacturing method is made of fiber-reinforced plastic and has elasticity. The narrow surface of such a case is a contact portion that contacts the electrode body having a laminated structure. Further, the wide surface of the case has a spring structure that connects the contact portions.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] Energy storage devices such as lithium-ion secondary batteries expand during charging and discharging. The inventor aims to suppress this expansion of energy storage devices. [Means for solving the problem]

[0006] The energy storage device disclosed herein comprises an electrode body having a positive electrode and a negative electrode, and a metal casing housing the electrode body. The casing is wound with continuous fibers arranged in a predetermined direction so as to cover its outer surface.

[0007] Such an energy storage device can suppress the expansion of the device itself. In addition, it can improve the strength of the outer casing. [Brief explanation of the drawing]

[0008] [Figure 1] Figure 1 is a schematic perspective view of a lithium-ion secondary battery. [Figure 2] Figure 2 is a schematic perspective view of a lithium-ion secondary battery, viewed from a different direction than in Figure 1. [Figure 3] Figure 3 is a schematic longitudinal cross-sectional view of a lithium-ion secondary battery. [Figure 4] Figure 4 is an exploded view of the electrode body (wound electrode body). [Figure 5] Figure 5 is a schematic diagram illustrating the state of the energy storage device after expansion. [Figure 6] Figure 6 is a schematic, enlarged cross-sectional view illustrating the expanded state of the energy storage device. [Figure 7] Figure 7 is a schematic plan view of a lithium-ion secondary battery as seen from the narrow side. [Figure 8] Figure 8 is a schematic plan view of a lithium-ion secondary battery as seen from the wide side. [Figure 9] Figure 9 is an explanatory diagram illustrating how to wrap fibers around a lithium-ion secondary battery. [Figure 10]Figure 10 is a schematic perspective view showing an energy storage module including the energy storage device disclosed herein. [Figure 11] Figure 11 is a schematic perspective view showing a pack-case type energy storage module including the energy storage device disclosed herein. [Modes for carrying out the invention]

[0009] The energy storage device described in this disclosure will be explained in detail below. In the drawings, the same reference numerals are used to denote components 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. The reference numerals L, R, U, D, F, and Rr in the drawings represent the left, right, top, bottom, front, and rear of the lithium-ion secondary battery 1. The left-right direction is defined as X, the up-down direction as Y, and the front-back direction as Z. However, these directions are merely for the convenience of explanation and do not limit the installation method of the energy storage device (lithium-ion secondary battery 1) in any way.

[0010] <Definition of Terms> 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. The following description of this embodiment will use a lithium-ion secondary battery, 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.

[0011] 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."

[0012] <Power storage device: Lithium-ion secondary battery 1> FIG. 1 is a perspective view schematically showing the lithium-ion secondary battery 1. FIG. 2 is a schematic perspective view of the lithium-ion secondary battery 1 viewed from a direction different from that of FIG. 1. FIGS. 1 and 2 show the configuration of the exterior body 10 with a part of the fiber 60 removed so as to be understandable. FIG. 3 is a longitudinal sectional view schematically showing the lithium-ion secondary battery 1. In FIG. 3, a longitudinal sectional view taken along line III-III of FIG. 1 is shown. In FIG. 3, a part of the electrode body 20 is shown in a transmissive manner so as to understand the configuration of the electrode body 20 housed in the exterior body 10. FIG. 4 is an exploded view of the electrode body 20 (wound electrode body).

[0013] The lithium-ion secondary battery 1 shown in FIGS. 1 to 3 is a preferred example of the power storage device disclosed herein. The lithium-ion secondary battery 1 includes an electrode body 20 and an exterior body 10 as shown in FIGS. 1 to 3.

[0014] <Electrode body 20> As shown in FIGS. 3 and 4, the electrode body 20 has a positive electrode 30 and a negative electrode 40. In this embodiment, the electrode body 20 is a wound electrode body in which a strip-shaped positive electrode 30 and a strip-shaped negative electrode 40 are stacked along the length direction via strip-shaped separators 50a and 50b and wound around a winding axis WL set in the width direction of the positive electrode 30. In this embodiment, a positive electrode tab 31c is provided at one end in the winding axis direction of the electrode body 20. Also, a negative electrode tab 41c is provided at the other end in the winding axis direction. That is, in this embodiment, along the winding axis, a positive electrode tab 31c is provided at one end of the electrode body 20, and a negative electrode tab 41c is provided at the other end. Note that the electrode body 20 is not limited to a wound electrode body, and may be a laminated electrode body in which positive electrodes and negative electrodes are alternately stacked via separators. Also, in the laminated electrode body, the strip-shaped separator may be in a so-called zigzag folded form, i.e., folded in a zigzag while sandwiching the positive electrode and the negative electrode therebetween.

[0015] <Positive electrode 30> As shown in Figure 4, 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 is capable of reversibly intercepting and releasing charge carriers (e.g., lithium ions). That is, the positive electrode active material layer 32 contains a positive electrode active material that can release charge carriers during charging and intercept 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. The positive electrode 30 may also 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 body 20. In this embodiment, 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 is a layer containing an inorganic filler (for example, alumina).

[0016] The material of the positive electrode current collector foil 31 may be any known positive electrode current collector foil used in this type of energy storage device, and is not particularly limited. Examples of materials for the positive electrode current collector foil 31 include 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. Examples of lithium composite metal oxides include LiCoO2, LiNiO2, LiFeO2, and 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. The positive electrode active material layer 32 may also contain various additives such as binders, conductive additives, inorganic fillers, or thickeners.

[0017] <Negative electrode 40> As shown in Figure 4, 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 is capable of reversibly intercepting and releasing charge carriers (e.g., lithium ions). That is, the negative electrode active material layer 42 contains a negative electrode active material that can intercept charge carriers and release them 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. The negative electrode 40 may also 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 body 20.

[0018] 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 this type of energy storage device. Examples of materials for the negative electrode current collector foil 41 include copper or copper alloys. As the negative electrode active material of the negative electrode active material layer 42, negative electrode active materials used in the negative electrode of general lithium-ion secondary batteries can be used. Specifically, negative electrode active materials include soft carbon (easily graphitizable carbon), amorphous carbon materials, graphite, hard carbon (difficult to graphitize carbon), carbon nanotubes and other carbon materials, silicon compounds, etc. These negative electrode active materials may be used individually or in combination of two or more. The negative electrode active material layer 42 may also contain various additives such as binders, conductive additives, inorganic fillers, or thickeners.

[0019] <Separators 50a, 50b> The separators 50a and 50b in this embodiment are porous sheets having insulating properties. However, the shape and dimensions of the separators 50a and 50b can be appropriately determined according to the design of the energy storage device and are not particularly limited. Typically, since the separators 50a and 50b insulate the positive electrode 30 and the negative electrode 40, the dimensions of the separators 50a and 50b are larger than those of the positive electrode 30 and the negative electrode 40. The material of the separators 50a and 50b can be any known separator used in this type of energy storage device and are not particularly limited. For example, the material of the separators 50a and 50b can preferably be a polyolefin such as polyethylene or polypropylene, polyester, cellulose, or a resin such as polyamide.

[0020] <Exterior 10> The outer casing 10 is a metal case that houses the electrode body 20. In this embodiment, the outer casing 10 has a hexahedral shape (in other words, a rectangular shape) that can accommodate the electrode body 20. In this embodiment, the electrode body 20 is housed in the outer casing 10 in a laminated structure in which a strip-shaped positive electrode 30 and a strip-shaped negative electrode 40 are stacked along a pair of opposing wide surfaces 11a1 and 11a2 of the rectangular case, with separators 50a and 50b in between. The outer casing 10 consists of a case body 11 and two sealing plates 13a and 13b. In this embodiment, the two sealing plates 13a and 13b are each provided with either a positive electrode external terminal 14 or a negative electrode external terminal 15.

[0021] The case body 11 is a so-called rectangular tubular member. The case body 11 has a pair of opposing wide surfaces 11a1 and 11a2 and a pair of opposing narrow surfaces 11b1 and 11b2 around the left-right direction X. The pair of opposing narrow surfaces 11b1 and 11b2 and the pair of opposing wide surfaces 11a1 and 11a2 are continuous along their long sides. The case body 11 has openings 10a and 10b (see Figure 3) on both sides along the left-right direction X. For convenience, in the following explanation, one of the pair of opposing wide surfaces 11a1 and 11a2 will be referred to as the "first surface" and the other wide surface 11a2 as the "second surface". Also, one of the pair of opposing narrow surfaces 11b1 and 11b2 will be referred to as the "bottom surface" and the other narrow surface 11b2 as the "top surface".

[0022] The thickness (plate thickness) of the case body 11, that is, the average plate thickness of the wide surfaces 11a1, 11a2 and the narrow surfaces 11b1, 11b2, is not particularly limited. Typically, the upper limit of the thickness (plate thickness) of the case body 11 may be 3 mm or less, 2 mm or less, or 1 mm or less. The lower limit of the thickness (plate thickness) of the case body 11 may be 0.3 mm or more, 0.4 mm or more, or 0.5 mm or more.

[0023] In this embodiment, the case body 11 can be manufactured, for example, by bending a single metal plate into a cylindrical shape and joining the joints (for example, by welding or bonding). In this embodiment, a welded joint portion 10c (wavy line in Figure 1) is formed on the upper surface 11b2 along the left-right direction X.

[0024] The sealing plates 13a and 13b are plate-shaped members that close a pair of openings 10a and 10b of the case body 11. In this embodiment, the sealing plates 13a and 13b are rectangular members that rest on the side edges of the pair of openings 10a and 10b and close the pair of openings 10a and 10b of the case body 11. In this embodiment, the positive external terminal 14 is attached to one of the sealing plates 13a in an insulated state. The negative external terminal 15 is attached to the other sealing plate 13b in an insulated state. For convenience, in the following description, one of the sealing plates 13a, 13b, will also be referred to as the "first sealing plate" and the other sealing plate 13b, 13b, will also be referred to as the "second sealing plate".

[0025] The outer casing 10, with the electrode body 20 housed inside, has a pair of openings 10a and 10b sealed by sealing plates 13a and 13b. In this embodiment, for example, the positive electrode internal terminal 16 (see Figure 3) is joined to the positive electrode tab 31c of the electrode body 20. The negative electrode internal terminal 17 (see Figure 3) is also joined to the negative electrode tab 41c of the electrode body 20. Furthermore, the negative electrode external terminal 15 is joined to the negative electrode internal terminal 17, and the sealing plate 13b is attached to the negative electrode tab 41c of the electrode body 20. In this state, the side of the positive electrode tab 31c with the positive electrode internal terminal 16 attached is inserted into the opening 10b of the case body 11, and the electrode body 20 is inserted into the case body 11. Then, the positive electrode external terminal 14 attached to the sealing plate 13a is joined to the positive electrode internal terminal 16 protruding from the other opening 10a of the case body 11. As a result, the sealing plate 13a is attached to the positive electrode tab 31c of the electrode body 20 inserted into the case body 11, and the sealing plate 13b is attached to the negative electrode tab 41c. Subsequently, the peripheral edges of the sealing plates 13a and 13b are welded to the peripheral edges of the openings 10a and 10b, respectively. In this way, the pair of openings 10a and 10b of the case body 11 are sealed by the sealing plates 13a and 13b.

[0026] In the configurations shown in Figures 1 to 3, an exterior body 10 is exemplified, in which sealing plates 13a and 13b are attached to both sides of a rectangular tubular case body 11 with open ends. In other words, a so-called double-terminal type energy storage device is exemplified here, in which a positive external terminal 14 and a negative external terminal 15 are attached to the sealing plates 13a and 13b on both sides. However, the energy storage device is not limited to this configuration. The configuration of the energy storage device may, for example, consist of a box-shaped case body having a bottomed rectangular parallelepiped shape with one side (top) open, and a sealing plate that seals the top surface of the case body. In other words, both the positive external terminal and the negative external terminal may be attached to a single sealing plate.

[0027] From the viewpoint of protecting the electrode body 20 from impact and the durability of the outer casing 10, the material of the outer casing 10 is preferably a metal material such as aluminum, aluminum alloy, iron, or iron alloy.

[0028] The outer casing 10 may be provided with a safety valve (not shown) and an injection hole (not shown). The safety valve is a thin-walled valve designed to release internal pressure when the internal pressure of the outer casing 10 rises above a predetermined level. The injection hole is a hole for injecting electrolyte. The injection hole is no longer needed after the electrolyte is injected and can therefore be sealed by laser welding. Alternatively, the injection hole can be sealed by attaching a plug or the like. Although not shown here, the safety valve may be provided, for example, on the bottom surface 11b1. The injection hole may also be provided, for example, on either the first sealing plate 13a or the second sealing plate 13b.

[0029] External positive terminal 14 and negative terminal 15 for external connection are provided exposed to the outside of the casing 10. These external terminals are electrically connected to the electrode body 20 housed within the casing 10. More specifically, the positive electrode 30 of the electrode body 20 is electrically connected to the positive terminal 14 exposed from the casing 10. The negative electrode 40 of the electrode body 20 is electrically connected to the negative terminal 15 exposed from the casing 10. A preferred example of the energy storage device of this disclosure is to expose the external terminals from both ends of the casing 10, as shown in Figures 1 and 2. The positive terminal 14 is provided on one side of a pair of sealing plates 13a and 13b. The negative terminal 15 is provided on the other sealing plate opposite to the sealing plate on which the positive terminal 14 is provided. This allows sufficient space for current collectors such as tabs, even on narrow side surfaces. In this embodiment, the positive external terminal 14 is provided on the first sealing plate 13a. The negative external terminal 15 is provided on the second sealing plate 13b. The positive external terminal 14 and the negative external terminal 15 are made of metal. For example, aluminum or an aluminum-based alloy may be used for the positive external terminal 14. For example, copper or a copper alloy may be used for the negative external terminal 15.

[0030] As shown in Figure 3, the positive electrode external terminal 14 can be electrically connected to the electrode body 20 via the positive electrode internal terminal 16. The negative electrode external terminal 15 can also be electrically connected to the electrode body 20 via the negative electrode internal terminal 17. 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.

[0031] Furthermore, the positive external terminal 14 and the negative external terminal 15 are mounted to the outside of the sealing plates 13a and 13b in an insulated manner via a gasket (not shown). The positive internal terminal 16 and the negative internal terminal 17 are mounted to the inside of the sealing plates 13a and 13b via an insulator (not shown). The materials used for the gasket and insulator may be, for example, insulating materials with excellent chemical resistance and weather resistance.

[0032] <Electrolytes> The outer casing 10 contains the electrolyte. For example, the electrolyte can be a liquid electrolyte (electrolyte solution) that is liquid at room temperature (25°C). Conventional known non-aqueous electrolytes can be used without particular limitations. Carbonates are preferred as non-aqueous electrolytes. In addition to the non-aqueous electrolytes mentioned above, solid electrolytes consisting entirely of solid components may also be used as the electrolyte.

[0033] Incidentally, such sealed energy storage devices undergo expansion and contraction due to charging and discharging, and over time, the interior swells, causing the outer casing 10 to swell. This tendency for the outer casing 10 to swell becomes stronger when the sealed energy storage device is large and has a high energy density. The inventors of this invention want to suppress the swelling of energy storage devices. According to the inventors' findings, in rectangular energy storage devices, swelling makes the outer casing 10 particularly susceptible to deformation and puts stress on the corners of the outer casing.

[0034] Figure 5 is a schematic diagram illustrating the state of the energy storage device after expansion. Figure 6 is an enlarged cross-sectional view illustrating the state of the energy storage device after expansion. Figure 6 shows an enlarged cross-sectional view of the corner 70 formed by the short sides of the narrow surfaces 11b1, 11b2 and the sealing plates 13a, 13b of Figure 5.

[0035] Energy storage devices gradually expand as they undergo repeated charging and discharging. The causes of this expansion include, for example, the expansion of the contained electrode body and the generation of gas inside the outer casing. When gas is generated inside the outer casing, the internal pressure increases. As a result, the sides of the outer casing 10 expand significantly, as shown in Figure 5. In other words, a force is applied to the sides from the inside of the outer casing 10, and this stress makes the corners susceptible to load. As shown in Figure 6, the outer casing 10 expands as the internal pressure increases. Then, the corners 70 are pulled to both sides by a pair of opposing narrow surfaces 11b1, 11b2 and the second sealing plate 13b, which are pushed from the inside of the outer casing 10. This puts a load on the corners 70.

[0036] Furthermore, from the viewpoint of improving volumetric energy efficiency, it is preferable that the energy storage device has a rectangular casing 10. As described above, a rectangular energy storage device has a hexahedral shape (i.e., consisting of six faces). Because the pressure applied to each face of the rectangular casing 10 is not uniform, the larger the surface area, the greater the bulge (especially near the center of the surface). For this reason, the rectangular casing 10 is more susceptible to the effects of the increase in internal pressure of the energy storage device and is more prone to deformation on the larger surface area. As a result, stress tends to concentrate at the corners 70 formed by the short sides (in this embodiment, the joints between the case body 11 and the sealing plates 13a and 13b), and a load is applied.

[0037] Based on these findings, the inventors propose a novel configuration for an energy storage device. Figure 7 is a schematic plan view of the lithium-ion secondary battery 1 as seen from the narrow side 11b2. Figure 8 is a schematic plan view of the lithium-ion secondary battery 1 as seen from the wide side 11a1. Figure 9 is an explanatory diagram illustrating the winding method of the fibers 60 in the lithium-ion secondary battery 1. Note that Figure 9 is a simplified representation of Figure 6 in order to explain the winding method of the fibers 60. The structure of the energy storage device proposed here is adopted in the lithium-ion secondary battery 1 shown in Figures 7 to 9.

[0038] <Fiber 60> As shown in Figure 7, in this embodiment, the fiber 60 is wound around a pair of opposing narrow surfaces 11b1 and 11b2. Also, as shown in Figure 8, the fiber 60 is wound around a pair of opposing wide surfaces 11a1 and 11a2. That is, the fiber 60 is continuously wound around the pair of opposing wide surfaces 11a1 and 11a2 and the pair of opposing narrow surfaces 11b1 and 11b2 via corners 80 formed by the long sides.

[0039] The fiber 60 has a first fiber 61 wound around the narrow surfaces 11b1 and 11b2 along a first direction, and a second fiber 62 wound around the narrow surfaces 11b1 and 11b2 along a second direction. The second direction is different from the first direction. Specifically, as shown in Figure 7, the first fiber 61 and the second fiber 62 are wound around the outer casing 10 in an intersecting manner.

[0040] When the side surface around which the fiber 60 is wrapped is viewed from above, the angle α at which the first fiber 61 is wrapped around the outer casing 10 is preferably 10° to 80° (more preferably 20° to 70°, and even more preferably 30° to 60°). Hereinafter, the term "angle" used in this specification for fibers refers to the angle between the line that bisects the side surface of the outer casing 10 (here, the top surface 11b2) along the central axis AX, as shown in Figure 9, and the direction of the fiber 60 wrapped around the outer casing 10. The angle α is the angle at which the first fiber 61 is wrapped with respect to the line that bisects the side surface of the outer casing 10 (here, the top surface 11b2) along the central axis AX. The term "central axis" used in this specification for the outer casing refers to the line that passes through the center of each of the two opposing side surfaces. In this embodiment, the central axis AX is drawn so as to pass through the center of the smallest surface area. More specifically, it is a line passing through the center of the side surface (first sealing plate 13a) on which the external terminals (specifically, the positive external terminal 14 and / or the negative external terminal 15) are provided, and the center of the surface (second sealing plate 13b) opposite to that side surface. The angle β is the angle at which the second fiber 62 is wound around a line that bisects the side surface of the outer casing (here, the top surface 11b2) along the central axis AX. The angle β at which the second fiber 62 is wound around the outer casing 10 is preferably -80° to -10° (more preferably -70° to -20°, and even more preferably -60° to -30°).

[0041] Furthermore, as shown in Figure 9, let θ be the angle between the first direction and the second direction. θ is not particularly limited. From the viewpoint of making it easier to suppress bulging on the side surface of the outer casing 10, the upper limit of the angle θ between the first direction and the second direction may be 160° or less, preferably 140° or less, more preferably 120° or less, and even more preferably 90° or less. Also, the lower limit of θ is preferably 20° or more, more preferably 40° or more, and even more preferably 60° or more.

[0042] The thickness (e.g., diameter) of the fiber 60 is not particularly limited, as long as it does not significantly impair the effects of the technology of this disclosure. Furthermore, the fiber 60 can be formed by overlapping the first fiber 61 and the second fiber 62. In this embodiment, the second fiber 62 is wound on top of the first fiber 61 wound around the case body 11 (outside the case body 11). The fiber 60 layer has thickness. The thickness of the layer (in other words, the thickness when the fiber 60 is wound around the case body 11) is not particularly limited. From the viewpoint of improving impact resistance, the thickness of the layer is preferably 10% or more, more preferably 15% or more, and even more preferably 20% or more, relative to the thickness (plate thickness) of the case body 11. Also, the upper limit of the layer thickness may be 30% or less, 25% or less, or 22% or less, relative to the thickness (plate thickness) of the case body 11. The thickness of the first fiber 61 may be the same as or different from the thickness of the second fiber 62. The order in which the first fiber 61 and the second fiber 62 are wrapped is not particularly limited. The first fiber 61 may be wrapped on top of the second fiber 62. In addition, the first fiber 61 may be wrapped on top of the first fiber 61 again, and the second fiber 62 may be wrapped on top of the second fiber 62 again. After wrapping the first fiber 61 and the second fiber 62, the first fiber 61 and the second fiber 62 may be wrapped in any order.

[0043] The spacing between the fibers 60 (first fiber 61 or second fiber 62) wound in the same direction is not particularly limited, as long as it does not significantly impair the effects of the technology of this disclosure. Furthermore, the spacing between the fibers 60 may be the same or different for the first fiber 61 and the second fiber 62.

[0044] Suitable fibers 60 include, for example, glass fibers, carbon fibers, and aramid fibers. These fibers have high tensile strength, thus improving the strength of the area covered by them. Among these fibers, glass fibers have the advantage of excellent heat insulation. Carbon fibers have the advantage of excellent machinability and ease of processing. Aramid fibers have the advantage of excellent electrical insulation. The material of the fiber 60 can be appropriately determined depending on the purpose.

[0045] Fiber 60 contains a resin as a base material. Suitable resins include, for example, thermosetting resins and thermoplastic resins. Examples of thermosetting resins include epoxy resins, unsaturated polyester resins, vinyl ester resins, phenolic resins, polyurethane resins, and silicone resins. Examples of thermoplastic resins include polyolefin resins, polyvinyl chloride resins, polystyrene resins, and fluororesins.

[0046] A suitable manufacturing method for the outer casing 10 may include, for example, a step of wrapping resin-impregnated fibers 60 around the outer casing 10, and a step of curing the resin.

[0047] In the process of winding the resin-impregnated fibers 60 onto the outer casing 10, a rectangular tubular outer casing 10 is prepared before sealing the opening 10b. The mandrel (core metal) to which this outer casing 10 is fixed is rotated, and the fibers 60 are wound onto the sides of the outer casing 10 (in this case, a pair of opposing wide surfaces 11a1, 11a2 and a pair of opposing narrow surfaces 11b1, 11b2). At this time, by winding the fibers 60 onto the outer casing 10 while moving the mandrel and / or reel in the direction of the central axis AX, the fibers can be wound at an angle. In addition, in the energy storage module 100 described later, the wide surfaces 11a1, 11a2 of the lithium-ion secondary battery 1 are arranged facing each other, so as shown in Figure 5, in this embodiment, the fibers 60 are wound onto a pair of opposing wide surfaces 11a1, 11a2 so as to be perpendicular to the central axis AX (see Figure 8).

[0048] In the resin curing process, for example, if a thermosetting resin is used as the base material, the fibers 60 can be fixed by sintering using a heater or the like. With this manufacturing method, a fiber-reinforced layer is formed in which the sides of the energy storage device are continuously covered with fibers 60, thereby increasing resistance to internal pressure rise. However, the above manufacturing method is not limited to the manufacturing method of the energy storage device of this disclosure. As an alternative manufacturing method, the outer casing 10 covered with fibers 60 can also be manufactured by methods such as the sheet winding method.

[0049] Thus, the outer casing 10 of the energy storage device disclosed herein is covered with a fiber-reinforced resin layer. This improves the strength of the outer casing 10. Furthermore, the expansion of the outer casing 10 is suppressed by the wrapping of the fibers 60. This suppresses deformation of the outer casing 10.

[0050] In the embodiment described above, the outer casing 10 is wrapped with continuous fibers 60 arranged in a predetermined direction so as to cover the outer circumferential surface. These fibers 60 can suppress the expansion of the side surfaces of the outer casing 10. As a result, stress can be prevented from being applied to the corners 70 of the outer casing 10.

[0051] In the embodiment described above, the energy storage device comprises an electrode body 20 and an outer casing 10. The outer casing 10 is a rectangular case having a pair of opposing wide surfaces 11a1, 11a2 and a pair of continuous opposing narrow surfaces 11b1, 11b. The electrode body 20 has a laminated structure in which a strip-shaped positive electrode 30 and a strip-shaped negative electrode 40 are stacked along the pair of opposing wide surfaces 11a1, 11a2 of the rectangular case via a separator 50. With this configuration, the flattened surface 21 of the electrode body 20 faces the wide surface (first surface 11a1 or second surface 11a2) of the outer casing 10. As a result, even if the wide surfaces 11a1, 11a2 are pressed in accordance with the expansion of the electrode body 20, the outer casing 10 can be held down so as not to bulge. As a result, the load applied to the corners 80 can be reduced.

[0052] In the embodiment described above, the first fiber 61 is wound around the side surface of the outer casing 10 in a direction that results in an angle α. The second fiber 62 is wound around the side surface of the outer casing 10 in a direction that results in an angle β. As a result, the first fiber 61 and the second fiber 62 are wound around the pair of opposing narrow surfaces 11b1 and 11b2 of the outer casing 10 in an intersecting manner. This restrains the side surfaces of the outer casing 10 (wide surfaces 11a1 and 11a2 and narrow surfaces 11b1 and 11b2), effectively suppressing expansion due to increased internal pressure of the outer casing 10. In addition, in this embodiment, the narrow surface (here, the top surface 11b2) is welded during the process of manufacturing the rectangular tubular case body 11. Since the first fiber 61 and the second fiber 62 cover the top surface 11b2 of the outer casing 10 in an intersecting manner, the welded joint 10c can be effectively protected. As a result, the strength of the outer casing 10 can be improved.

[0053] <Energy storage module> The energy storage module comprises an energy storage device according to the disclosure and a restraining member that arranges and restrains a plurality of the energy storage devices in a predetermined direction.

[0054] A suitable example of using the energy storage device of this disclosure is the energy storage module 100 shown in Figure 9. Figure 10 is a schematic perspective view of an energy storage module including an energy storage device according to another embodiment of the present disclosure. This energy storage module 100 comprises a plurality of energy storage devices (e.g., lithium-ion secondary batteries 1) and a restraining member 110.

[0055] As shown in Figure 10, in this example, the wide surfaces 11a1 and 11a2 of lithium-ion secondary batteries 1 are arranged facing each other in the front-to-back direction Z to form a stack 2. Furthermore, the positive electrode external terminals 14 and negative electrode external terminals 15 provided on a pair of sealing plates 13a and 13b are arranged alternately, with their orientations reversed. Here, the positive electrode external terminal 14 of one adjacent lithium-ion secondary battery 1 and the negative electrode external terminal 15 of the other lithium-ion secondary battery 1 can be electrically connected to each other by a metal busbar (not shown). However, the configuration of this embodiment does not limit the arrangement or connection method of the lithium-ion secondary batteries 1. The lithium-ion secondary batteries 1 can be connected in series or in parallel.

[0056] Furthermore, the energy storage module disclosed herein may include a plurality of spacers. As shown in Figure 9, the energy storage module 100 includes a plurality of spacers 120. The spacers 120 are placed between the wide surfaces 11a1, 11a2 of the lithium-ion secondary battery 1 and the wide surfaces 11a1, 11a2 of the lithium-ion secondary battery 1 that are facing each other. The spacers 120 play a role in suppressing swelling by applying a load to the side surface of the lithium-ion secondary battery 1. In addition, the spacers 120 also play a role as a cushioning material that protects the lithium-ion secondary battery 1 from external shocks and vibrations. Note that conventionally known spacers 120 can be used. The material of the spacers 120 is not particularly limited. Rubber (thermosetting elastomer) is preferred as the material of the spacers 120.

[0057] <Restraining member> A preferred example of a restraining member constituting the energy storage module disclosed herein is shown in Figure 9. In this example, the restraining member 110 includes a pair of opposing end plates 112, a pair of side bars 113, and a bottom plate 111. The pair of end plates 112 includes a first end plate 112a positioned on one end (here, the front F side) of the arranged plurality of lithium-ion secondary batteries 1, and a second end plate 112b positioned on the other end (here, the rear Rr side). The pair of side bars 113 connect the first end plate 112a and the second end plate 112b opposite the first end plate 112a. In this example, two first side bars 113a and two second side bars 113b are arranged to support a pair of sealing plates 13a and 13b that form the sides of the lithium-ion secondary battery 1. The bottom plate 111 is positioned in contact with the bottom surface 11b1 of the plurality of lithium-ion secondary batteries 1. The upper surfaces 11b2 of the multiple lithium-ion secondary batteries 1 are not supported by the restraining member 110.

[0058] In the above-described energy storage module, a pair of opposing wide surfaces 11a1 and 11a2 of the lithium-ion secondary battery 1 are constrained. That is, a load is applied in the stacking direction of the lithium-ion secondary battery 1 (here, the front-to-back direction Z), suppressing the expansion of the pair of opposing wide surfaces 11a1 and 11a2. Therefore, in an energy storage device (i.e., an energy storage module) that is constrained in this way, pressure is concentrated on a pair of opposing narrow surfaces 11b1 and 11b2, making them more prone to expansion. In contrast, the lithium-ion secondary battery 1 has its pair of opposing narrow surfaces 11b1 and 11b2 covered with fibers 60. As a result, the expansion of the outer casing 10 is suppressed, and the load on the corners 70 can be reduced.

[0059] Another preferred example of the energy storage module disclosed herein is a pack-type module as shown in Figure 11. Figure 11 is a schematic perspective view of the pack-case type energy storage module 102 disclosed herein. In Figure 11, a portion of the pack-case type energy storage module 102 is shown disassembled to show its configuration. The pack-case type energy storage module 102 is a cell-to-pack structure in which a plurality of lithium-ion secondary batteries 1 are housed inside a restraining member 110 (in this example, a pack case 210).

[0060] The pack case 210 used in the pack case type energy storage module 102 disclosed herein comprises a bottom wall 211, side walls 212, and a top wall (not shown). As shown in Figure 11, the side walls 212 extending along the left-right direction X directly support both ends of the stack 2. Multiple lithium-ion secondary batteries 1 are arranged on the bottom wall 212. The lithium-ion secondary batteries 1 and the bottom wall 211 can be bonded together with an adhesive or the like. This fixes the lithium-ion secondary batteries 1 within the pack case 210. The top wall forms the upper part of the pack case 210. The top wall faces the bottom wall 211. The top wall is positioned to cover the multiple lithium-ion secondary batteries 1 housed within the pack case 210.

[0061] In this Cell-to-Pack structure, the side walls 212 of the pack case 210 directly support both ends of the stacked lithium-ion secondary battery 1. This configuration allows for a reduction in the number of restraining members, thereby improving the volumetric energy efficiency of the module.

[0062] In the Cell-to-Pack structure described above, a pair of opposing wide surfaces 11a1 and 11a2 of the lithium-ion secondary battery 1 are constrained. Therefore, swelling of the constrained wide surfaces 11a1 and 11a2 is suppressed. However, pressure is concentrated on the pair of opposing narrow surfaces 11b1 and 11b2 that are not constrained, making them more prone to swelling. In addition, unlike the energy storage module 102 described above, the number of restraining members 110 is small, so it is preferable to improve the strength of the energy storage device and protect it from shocks and vibrations. Here, the lithium-ion secondary battery 1 is covered with fibers 60. This suppresses swelling of the outer casing 10, thereby reducing the load on the corners 70. Furthermore, the strength of the outer casing 10 is improved, making it more resistant to shocks and vibrations.

[0063] The specific examples of the technology disclosed herein have been described in detail above, but these are merely illustrative and do not limit the scope of the claims. The technology described in the claims includes various modifications and changes to the specific examples described above.

[0064] 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.

[0065] Item 1: An energy storage device comprising an electrode body having a positive electrode and a negative electrode, and a metal casing body housing the electrode body, wherein the casing body is wound with continuous fibers arranged in a predetermined direction so as to cover its outer surface.

[0066] Item 2: The energy storage device according to Item 1, wherein the outer casing is a rectangular case having a pair of opposing wide surfaces and a pair of opposing narrow surfaces continuous with the wide surfaces, the electrode body has a laminated structure in which a sheet-like positive electrode and a sheet-like negative electrode are stacked along the pair of opposing wide surfaces of the rectangular case with a separator in between, and the fibers are continuously wound around the pair of opposing wide surfaces and the pair of opposing narrow surfaces.

[0067] Item 3: A power storage module comprising a power storage device as described in Item 1 or 2, and a restraining member for arranging and restraining a plurality of the power storage devices in a predetermined direction. [Explanation of Symbols]

[0068] 1. Lithium-ion rechargeable battery 2 Laminate 10 Exterior 10a, 10b opening 10c Welded joint 11 Case body 11a1, 11a2 Wide surface 11b1, 11b2 narrow side 13a, 13b Sealing plate 14 Positive external terminal 15 Negative external terminal 16 Positive internal terminal 17 Negative internal terminal 20 Electrode body 21 flat plane 30 positive electrode 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 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 50a, 50b Separator 60 fibers 61 First Fiber 62 Second Fiber 70, 80 corners 100 Energy Storage Modules 102 Pack-type energy storage module 110 Restraining member 111 Bottom Plate 112a First end plate 112b Second End Plate 113 Sidebar 114 Bis 120 Spacer 120a First Spacer 120b Second Spacer 210 pack case 211 Bottom wall 212 Side wall AX center axis WL winding shaft α angle β angle θ angle

Claims

1. An electrode body having a positive electrode and a negative electrode, A metal casing housing the electrode body, Equipped with, The aforementioned outer casing is an energy storage device in which continuous fibers are wound around the outer surface so as to be arranged in a predetermined direction.

2. The exterior body is, A pair of opposing wide surfaces, The rectangular case has a wide surface and a pair of opposing narrow surfaces that are continuous with it. The electrode body is The aforementioned rectangular case has a laminated structure in which a strip-shaped positive electrode and a strip-shaped negative electrode are stacked along a pair of opposing wide surfaces with a separator in between. The energy storage device according to claim 1, wherein the fibers are continuously wound around the pair of opposing wide surfaces and the pair of opposing narrow surfaces.

3. A power storage device according to claim 1 or 2, A restraining member that arranges and restrains multiple energy storage devices in a predetermined direction, A battery storage module equipped with the following features.

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