Energy storage module and spacers used therein

Abstract

To provide an energy storage module that can stably press on an energy storage device. [Solution] The energy storage module disclosed herein comprises a first energy storage device and a second energy storage device, and a spacer. The spacer comprises a base portion and a plurality of cylindrical projections 220. The cylindrical projections 220 have a peripheral wall portion 220w and a hollow portion 220h surrounded by the peripheral wall portion 220w. The peripheral wall portion 220w has a first portion 221 and a second portion 222, and the hollow portion 220h is provided offset to one side from the center of the cylindrical projection 220 in a plan view, and is configured such that when a predetermined load is applied from the alignment direction X, the first portion 221 of the peripheral wall portion 220w is compressed and deformed, while the second portion 222 is buckled.

Description

Technical Field

[0001] The present invention relates to a power storage module and a spacer used therefor.

Background Art

[0002] Conventionally, a power storage module including a plurality of power storage devices arranged along an array direction, a spacer arranged between the plurality of power storage devices, and a restraint mechanism for restraining the plurality of power storage devices and the spacer in the array direction has been widely used (for example, Patent Documents 1-3).

[0003] For example, Patent Document 1 discloses a spacer having a flat base portion and a plurality of columnar protrusions protruding from the base portion toward the power storage device. Patent Document 1 describes that when the power storage device expands, the protrusions are compressed and deformed so that the cross section expands, and the expansion of the power storage device can be absorbed.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0005] In recent years, high-capacity energy storage devices tend to expand significantly. This makes the protrusions of the spacer more prone to compression. According to our research, when the compression ratio of the protrusions is high, the "compression deformation" of the protrusions alone may not be able to absorb the expansion of the energy storage device, potentially leading to a rapid increase in the reaction force on the energy storage device. Therefore, a novel configuration was needed that could stably press the energy storage device with a predetermined load.

[0006] The present invention has been made in view of the above circumstances, and its main objective is to provide a novel energy storage module and spacer that can stably press an energy storage device. [Means for solving the problem]

[0007] The present invention discloses an energy storage module comprising a first energy storage device and a second energy storage device arranged along the alignment direction, a spacer disposed between the first energy storage device and the second energy storage device, and a restraining mechanism that restrains the first energy storage device, the second energy storage device, and the spacer in the alignment direction. The spacer comprises a flat base portion and a plurality of cylindrical projections protruding from the base portion toward the first energy storage device. Each of the plurality of cylindrical projections has a peripheral wall portion extending toward the first energy storage device and a hollow portion surrounded by the peripheral wall portion. The peripheral wall portion has a first portion with a relatively thicker thickness and a second portion with a relatively thinner thickness, and the hollow portion is provided offset to one side from the center of the cylindrical projection portion in a plan view, and is configured such that when a predetermined load is applied from the alignment direction, the first portion of the peripheral wall portion is compressed and deformed, while the second portion is buckled.

[0008] In the above spacer, when the energy storage device expands and a predetermined load is applied from the alignment direction, the second portion of the cylindrical projection partially buckles. This suppresses an increase in reaction force even when the compressibility of the cylindrical projection increases. As a result, excessive load on the energy storage device can be suppressed, and the energy storage device can be pressed stably. [Brief explanation of the drawing]

[0009] [Figure 1] Figure 1 is a schematic perspective view showing an energy storage module according to one embodiment. [Figure 2] Figure 2 is a schematic perspective view showing the energy storage device shown in Figure 1. [Figure 3] Figure 3 is a schematic longitudinal cross-sectional view along the line III-III in Figure 2. [Figure 4] Figure 4 is a schematic perspective view showing the spacer in Figure 1. [Figure 5] Figure 5 is a schematic perspective view showing the cylindrical projection. [Figure 6] Figure 6 is a schematic plan view showing the cylindrical projection. [Figure 7] Figure 7 shows the simulation results when the cylindrical projection in Figure 5 is compressed. [Figure 8] Figure 8 shows the simulation results when the cylindrical projection in Figure 6 is compressed. [Figure 9] Figure 9 is a schematic longitudinal cross-sectional view along the line IV-IV in Figure 8. [Figure 10] Figures 10(A) and (B) are explanatory diagrams illustrating the concept of the technology disclosed herein. [Figure 11] Figure 11 shows the simulation results illustrating the relationship between compressibility and reaction force. [Figure 12] Figures 12(A) to (C) are equivalent to Figure 6 of the cylindrical projection in a modified example. [Modes for carrying out the invention]

[0010] Hereinafter, a preferred embodiment of the power storage module disclosed herein will be described while referring to the drawings as appropriate. Matters other than those specifically mentioned in this specification and necessary for the implementation of the present invention (for example, the general configurations and manufacturing processes of power storage modules and power storage devices that do not characterize the present invention) can be grasped as the design matters of those skilled in the art based on the prior art in the relevant field. The power storage module disclosed herein can be implemented based on the content disclosed in this specification and the common technical knowledge in the relevant field.

[0011] In the following drawings, members and parts having the same function are denoted by the same reference numerals, and duplicate explanations may be omitted or simplified. Also, the notation "A to B" indicating a range in this specification shall include the meanings of "not less than A and not more than B", "preferably greater than A", and "preferably less than B".

[0012] FIG. 1 is a perspective view schematically showing a power storage module 500 according to an embodiment. The power storage module 500 includes a plurality of power storage devices (first power storage device and second power storage device) 100 arranged along the arrangement direction X, a spacer 200 arranged between adjacent power storage devices 100 in the arrangement direction X (between the first power storage device and the second power storage device), and a restraint mechanism 300 that restrains the plurality of power storage devices 100 and the spacer 200 in the arrangement direction X. In the following description, the reference signs F, Rr, L, R, U, and D in the drawings represent front, rear, left, right, up, and down, respectively, and the reference signs X, Y, and Z in the drawings represent the thickness direction, the width direction orthogonal to the thickness direction, and the height direction orthogonal to the thickness direction and the width direction of the power storage device 100, respectively. The thickness direction X is also the arrangement direction of the power storage devices 100. However, these are merely directions for convenience of explanation and do not limit the installation form of the power storage module 500 in any way.

[0013] The restraining mechanism 300 is a mechanism that restrains a plurality of power storage devices 100 and spacers 200 in the array direction X. The restraining mechanism 300 is configured to apply a specified restraining load to the plurality of power storage devices 100 and spacers 200 from the array direction X. Here, the restraining mechanism 300 includes a pair of end plates 310, a pair of side plates 320, and a plurality of screws 330. The pair of end plates 310 and the pair of side plates 320 are preferably made of metal. However, a part of the pair of end plates 310 and / or the pair of side plates 320 may be made of resin.

[0014] The pair of end plates 310 are respectively arranged at both ends of the power storage module 500 in the array direction X. The pair of end plates 310 sandwich the plurality of power storage devices 100 and spacers 200 in the array direction X.

[0015] The pair of side plates 320 bridge the pair of end plates 310. The pair of side plates 320 are fixed to the end plates 310 by a plurality of screws 330 so that the restraining load is approximately 10 to 15 kN, for example. Thereby, a restraining load is applied to the plurality of power storage devices 100 and spacers 200 from the array direction X, and the power storage module 500 is integrally held. However, the configuration of the restraining mechanism is not limited to this. The restraining mechanism 300 may include, for example, a plurality of restraining bands, binding bars, etc. instead of the side plates 320.

[0016] The plurality of power storage devices 100 are arranged side by side along the array direction X (the thickness direction X of the power storage device 100) between the pair of end plates 310. A spacer 200 is arranged between adjacent power storage devices 100 in the array direction X. In the array direction X, the power storage devices 100 and spacers 200 are arranged alternately.

[0017] The energy storage device 100 is a device that can be repeatedly charged and discharged. In this specification, "energy storage device" is a concept that encompasses secondary batteries such as lithium-ion secondary batteries and nickel-metal hydride batteries, and capacitors that utilize chemical reactions such as lithium-ion capacitors and pseudocapacitance capacitors. The shape, size, number, arrangement, etc. of the multiple energy storage devices 100 that constitute the energy storage module 500 can be changed as appropriate without being limited to the embodiments disclosed herein.

[0018] Figure 2 is a perspective view of the energy storage device 100. As can be seen from Figures 1 and 2, the multiple energy storage devices 100 are all flattened rectangular in shape and are identical in this respect. The multiple energy storage devices 100 are arranged so that their long sides 12b, which will be described later, face each other. The multiple energy storage devices 100 are arranged so that their long sides 12b are parallel to each other.

[0019] Figure 3 is a schematic longitudinal cross-sectional view along the line III-III in Figure 2. As shown in Figure 3, the energy storage device 100 here comprises a battery case 10, an electrode body 20, a positive electrode terminal 30, a negative electrode terminal 40, and an electrolyte (not shown). The energy storage device 100 here is a non-aqueous electrolyte secondary battery, and more specifically, a lithium-ion secondary battery.

[0020] The battery case 10 is a housing that contains the electrode body 20 and the electrolyte. As shown in Figure 2, the battery case 10 has a flat, bottomed rectangular parallelepiped (square) shape. The material of the battery case 10 can be the same as that used conventionally, and there are no particular restrictions. The battery case 10 is preferably made of metal, and more preferably of aluminum, aluminum alloy, iron, iron alloy, etc. As shown in Figure 3, the battery case 10 comprises an outer casing 12 having an opening 12h and a sealing plate (lid) 14 that seals the opening 12h.

[0021] As shown in Figure 2, the exterior body 12 comprises a substantially rectangular bottom surface 12a having long and short sides, a pair of long sides 12b extending from the long side of the bottom surface 12a and facing each other, and a pair of short sides 12c extending from the short side of the bottom surface 12a and facing each other. The bottom surface 12a faces the opening 12h (see Figure 3). In this specification, "substantially rectangular" is a term that includes not only a perfect rectangle, but also shapes such as those in which the corners connecting the long and short sides of a rectangle are rounded (R-shaped), or shapes with notches at the corners.

[0022] The long side 12b is the surface facing the spacer 200. As shown in Figure 2, the long side 12b is flat. Here, the long side 12b is in direct contact with the spacer 200. However, in other embodiments, it may face the spacer 200 via other members. In a plan view, the area of ​​the long side 12b is larger than the area of ​​the short side 12c. Although not particularly limited, in the case of high-capacity types used for automotive applications, etc., the area of ​​the long side 12b is approximately 10,000 mm². 2 It is good if it is greater than or equal to 15,000 mm 2 The above is preferable, and 20,000 mm 2 The above is more preferable, 25,000 mm 2 The above is even more preferable, 30,000 mm 2 The above are particularly preferable.

[0023] As shown in Figure 1, the sealing plate 14 is substantially rectangular in plan view. As shown in Figure 2, the sealing plate 14 is a plate-like member that extends along the XY plane. As shown in Figure 3, the sealing plate 14 is attached to the outer casing 12 so as to close the opening 12h. The sealing plate 14 faces the bottom surface 12a of the outer casing 12. The sealing plate 14 is substantially rectangular. The battery case 10 is integrated by joining (preferably by welding) the sealing plate 14 to the periphery of the opening 12h of the outer casing 12. The battery case 10 is airtightly sealed.

[0024] As shown in Figure 3, the sealing plate 14 is provided with an electrolyte injection hole 15, a discharge valve 17, and two terminal lead-out holes 18 and 19. The electrolyte injection hole 15 is for injecting electrolyte into the battery case 10 after the sealing plate 14 has been assembled to the outer casing 12. The electrolyte injection hole 15 is sealed by a sealing member 16. The discharge valve 17 is configured to rupture when the pressure inside the battery case 10 exceeds a predetermined value, thereby releasing gas from inside the battery case 10 to the outside. The terminal lead-out holes 18 and 19 penetrate the sealing plate 14 in the height direction Z.

[0025] The positive terminal 30 is located at one end of the sealing plate 14 in the width direction Y (the left end in Figures 2 and 3). The negative terminal 40 is located at the other end of the sealing plate 14 in the width direction Y (the right end in Figures 2 and 3). As shown in Figure 3, the positive terminal 30 and the negative terminal 40 extend from the inside to the outside of the sealing plate 14 through terminal lead holes 18 and 19, respectively. The positive terminal 30 and the negative terminal 40 are crimped to the peripheral portion surrounding the terminal lead holes 18 and 19 of the sealing plate 14 by a crimping process. Crimped portions 30c and 40c are formed at the ends of the outer casing 12 side of the positive terminal 30 and the negative terminal 40 (the lower end in Figure 3). In this way, the positive terminal 30 and the negative terminal 40 are fixed to the sealing plate 14.

[0026] As shown in Figure 3, the positive terminal 30 is electrically connected to the positive tab 23 of the electrode body 20 via the positive current collector 50 inside the casing 12. The positive terminal 30 is insulated from the sealing plate 14 by the internal insulating member 80 and the gasket 90. The negative terminal 40 is electrically connected to the negative tab 25 of the electrode body 20 via the negative current collector 60 inside the casing 12. The negative terminal 40 is insulated from the sealing plate 14 by the internal insulating member 80 and the gasket 90.

[0027] As shown in Figures 2 and 3, plate-shaped positive electrode external conductive members 32 and negative electrode external conductive members 42 are attached to the outer surface of the sealing plate 14. The positive electrode external conductive member 32 is electrically connected to the positive electrode terminal 30. The negative electrode external conductive member 42 is electrically connected to the negative electrode terminal 40. The positive electrode external conductive member 32 and the negative electrode external conductive member 42 are insulated from the sealing plate 14 by an external insulating member 92.

[0028] As shown in Figure 1, the positive electrode external conductive member 32 and the negative electrode external conductive member 42 are equipped with busbars that electrically connect multiple energy storage devices 100 to each other. Here, of two energy storage devices 100 adjacent to each other in the array direction X, the positive electrode external conductive member 32 of one energy storage device 100 and the negative electrode external conductive member 42 of the other energy storage device 100 are electrically connected by the busbars. As a result, the energy storage module 500 is electrically connected in series. However, the method of connecting multiple energy storage devices 100 is not limited to series; for example, they may be connected in parallel, multiple series, multiple parallel, etc.

[0029] The electrode body 20 has a positive electrode and a negative electrode. The configuration of the electrode body 20 may be the same as in the conventional design and is not particularly limited. Also, the number of electrode bodies 20 arranged inside one battery case 10 is not particularly limited and may be one or two or more. In this embodiment, the electrode body 20 is a flat wound electrode body formed by stacking a strip-shaped positive electrode and a strip-shaped negative electrode insulated via a separator and winding them around a winding axis. In this embodiment, the positive electrode has a strip-shaped positive electrode current collector and a positive electrode active material layer provided in a strip shape along the longitudinal direction of the positive electrode current collector. In this embodiment, the negative electrode has a strip-shaped negative electrode current collector and a negative electrode active material layer provided in a strip shape along the longitudinal direction of the negative electrode current collector. However, in other embodiments, the electrode body 20 may be a laminated electrode body in which a plurality of rectangular positive electrodes and a plurality of rectangular negative electrodes are stacked in an insulated state.

[0030] As shown in Figure 3, a positive electrode tab 23 is provided at one end of the electrode body 20 in the winding axis direction (width direction Y in Figure 3). A positive electrode current collector 50 is attached to the positive electrode tab 23. The positive electrode current collector 50 constitutes a conductive path that electrically connects the positive electrode terminal 30 and the positive electrode of the electrode body 20. A negative electrode tab 25 is provided at the other end of the electrode body 20 in the winding axis direction (width direction Y in Figure 3). A negative electrode current collector 60 is attached to the negative electrode tab 25. The negative electrode current collector 60 constitutes a conductive path that electrically connects the negative electrode terminal 40 and the negative electrode of the electrode body 20.

[0031] The electrolyte can be the same as conventional solutions and is not particularly limited. The electrolyte is typically a non-aqueous electrolyte containing a non-aqueous solvent and a supporting salt (electrolyte salt). Examples of non-aqueous solvents include carbonates, esters, ethers, nitriles, sulfones, lactones, etc. These can be used individually or in combination of two or more. Among these, carbonates are preferred. Examples of electrolyte salts include fluorine-containing lithium salts such as lithium hexafluoride phosphate (LiPF6) and lithium tetrafluoroborate (LiBF4). The electrolyte may also contain additives as needed.

[0032] As shown in Figure 1, the spacers 200 are positioned between each of the multiple energy storage devices 100 in the array direction X. However, the spacers 200 only need to be positioned between at least two adjacent energy storage devices (first energy storage device and second energy storage device) 100 in the array direction X, and do not necessarily need to be positioned between all of the energy storage devices 100. In this embodiment, the spacers 200 are in contact with the long side surfaces 12b of the energy storage devices 100. However, in other embodiments, other materials (e.g., conventionally known thermal insulation materials) may be interposed between the energy storage devices 100 and the spacers 200.

[0033] Figure 4 is a schematic perspective view of the spacer 200. As shown in Figure 4, the spacer 200 comprises a base portion 210 and a plurality of cylindrical protrusions 220. The base portion 210 and the plurality of cylindrical protrusions 220 are integrally formed in this case. The material of the spacer 200 (base portion 210 and plurality of cylindrical protrusions 220) is not particularly limited, but it is preferably made of a polymer material, and more preferably made of rubbers (thermosetting elastomers) such as silicone rubber, fluororubber, urethane rubber, natural rubber, styrene-butadiene rubber, butyl rubber, ethylene propylene rubber (EPM, EPDM), butadiene rubber, isoprene rubber, norbornene rubber, etc. Among these, silicone rubber and EPDM are preferred.

[0034] In some embodiments, the spacer 200 is preferably insulating. In this specification, "insulating" means that the volume resistivity measured according to JIS K6911:2006 is 1.0 × 10⁻⁶. 10 This means that the resistivity is Ω·cm or greater. The above volume resistivity of spacer 200 is 1.0 × 10⁻⁶ 12 A value of Ω·cm or higher is preferable.

[0035] The base portion 210 is a flat plate-like portion with a substantially uniform thickness. Although not particularly limited, the thickness of the base portion 210 (length in the arrangement direction X) is preferably 0.1 to 5 mm, and more preferably 0.3 to 2 mm. Having the base portion 210 improves productivity and workability when arranging the spacer 200 between multiple energy storage devices 100.

[0036] As shown in Figure 4, the base portion 210 has a pair of opposing surfaces 212 that intersect the array direction X and extend along the YZ plane. Each of the pair of opposing surfaces 212 is a surface that faces the energy storage device 100 (specifically the long side surface 12b). The size of the opposing surfaces 212, i.e., the height (length in the height direction Z) and / or the width (length in the width direction Y), is preferably approximately the same as the size of the opposing surface of the energy storage device 100 (here, the long side surface 12b), i.e., the height and / or width (approximately ±1 cm). This facilitates alignment with the energy storage device 100 and improves the productivity and workability of the energy storage module 500.

[0037] Multiple cylindrical protrusions 220 protrude from one opposing surface 212Rr (the surface facing the first energy storage device 100) of the base portion 210. In this embodiment, the other opposing surface 212F (the surface facing the second energy storage device 100) of the base portion 210 has a flat surface and does not have multiple cylindrical protrusions 220. That is, of the pair of opposing surfaces 212 of the base portion 210, multiple cylindrical protrusions 220 are provided only on one opposing surface 212Rr. However, in other embodiments, multiple cylindrical protrusions 220 may also be provided on the other opposing surface 212F of the base portion 210. In other words, the base portion 210 may have multiple cylindrical protrusions 220 on each of the pair of opposing surfaces 212.

[0038] Each of the multiple cylindrical protrusions 220 is a portion that protrudes from the base portion 210 toward the first energy storage device 100 (the rear side in Figure 4). The multiple cylindrical protrusions 220 here extend toward the long side surface 12b of the first energy storage device 100. The multiple cylindrical protrusions 220 are regularly arranged on one opposing surface 212Rr of the base portion 210. The multiple cylindrical protrusions 220 are scattered in an island-like (spot-like) manner on the opposing surface 212Rr of the base portion 210. The multiple cylindrical protrusions 220 here are identical in size and shape. A predetermined gap is ensured between adjacent cylindrical protrusions 220 on the opposing surface 212Rr of the base portion 210. In some embodiments, it is preferable that adjacent cylindrical protrusions 220 are arranged so that they do not come into contact with each other even when a restraining load is applied from the arrangement direction X.

[0039] In some embodiments, the cylindrical projection 220 located on the outermost edge of the opposing surface 212Rr is preferably located inward from the outer edge of the long side surface 12b of the opposing first energy storage device 100. Also, in some embodiments, one or more cylindrical projections 220 are preferably arranged over a wider area than the region facing the electrode body 20 of the opposing first energy storage device 100 (the region of the electrode body 20 that contacts the long side surface 12b of the battery case 10, and especially in the case of a wound electrode body, the flat portion excluding the curved portion). However, the shape, size, arrangement, etc. of the multiple cylindrical projections 220 are not limited to the embodiment shown in Figure 4 and can be appropriately changed, for example, depending on the shape, size, capacity, constraint load, etc. of the energy storage device 100. Furthermore, the shapes, sizes, and spacing of the multiple cylindrical projections 220 may differ from each other.

[0040] Figure 5 is a schematic perspective view showing one cylindrical projection 220. Figure 6 is a schematic plan view showing one cylindrical projection 220. As shown in Figure 5, the cylindrical projection 220 here has an outer shape that is approximately prismatic (approximately quadrangular). However, in other embodiments, the outer shape of the cylindrical projection 220 may be cylindrical (including elliptical), or an approximately polygonal prismatic shape other than a prismatic (approximately triangular, approximately hexagonal, etc.). In this specification, "approximately prismatic" is a term that includes not only a perfect prismatic shape, but also shapes such as those where the corners connecting two sides are rounded (R-shaped), or shapes with notches at the corners, as shown in Figure 5. The same applies to other polygonal prismatic shapes described as "approximately ○○ shape" in this specification.

[0041] Although not particularly limited, as shown in Figure 5, the protruding height Da (length in the arrangement direction X) of the cylindrical projection 220 is typically greater than the thickness of the base portion 210 when assembled to the energy storage module 500 and before being compressed by the restraining mechanism 300, and is generally 1 to 10 mm, more preferably 1 to 8 mm, and even more preferably 3 to 5 mm. Also, as shown in Figure 6, the width (length in the width direction Y) Wa and height (length in the height direction Z) Ha of the cylindrical projection 220 are generally 2 to 30 mm, more preferably 3 to 20 mm, and even more preferably 5 to 10 mm, respectively. In some embodiments, it is preferable that the width Wa and height Ha of the cylindrical projection 220 are the same length.

[0042] As shown in Figures 5 and 6, each of the multiple cylindrical projections 220 has a peripheral wall portion 220w extending toward the first energy storage device 100 side (the rear side in Figure 5) and a hollow portion 220h surrounded by the peripheral wall portion 220w. The peripheral wall portion 220w is provided in an annular shape and constitutes the outer edge of the cylindrical projection 220. The peripheral wall portion 220w has a first portion 221 which is relatively thicker and a second portion 222 which is relatively thinner. The peripheral wall portion 220w may further have a third portion which is thinner than the first portion 221 and thicker than the second portion 222.

[0043] The first part 221 is configured to compress and deform without bending when a predetermined load is applied from the alignment direction X. In this specification, "compression deformation" means deformation such that it is crushed and its cross-section expands. The first part 221 is preferably a so-called solid structure (a structure filled with contents) that does not have hollow parts or voids. The first part 221 is the part that includes the thickest part of the peripheral wall 220w. As shown in Figure 6, the first part 221 is substantially I-shaped in plan view. The first part 221 is provided in a strip shape with substantially uniform thickness along one side of the hollow part 220h (the lower side in Figure 6) along one side of the hollow part 220h (the width direction Y in Figure 6). Although not particularly limited, the thickness H1 (average length in the height direction Z) of the first part 221 is preferably about 0.5 to 10 mm, more preferably 1 to 8 mm, and even more preferably 2 to 5 mm.

[0044] The second part 222 is a part configured to buckle when a predetermined load is applied from the alignment direction X. In this specification, "buckling" refers to bending under a certain load (buckling load) and bending in the alignment direction X. As shown in Figure 6, the second part 222 is substantially U-shaped in plan view. The second part 222 has a left portion provided on the left side of the hollow part 220h in a strip shape with substantially uniform thickness along the height direction Z, an upper portion provided on the upper side of the hollow part 220h in a strip shape with substantially uniform thickness along the width direction Y, and a right portion provided on the right side of the hollow part 220h in a strip shape with substantially uniform thickness along the height direction Z. The second part 222 has rounded R-shaped portions (R-sections) at its corners. Structures with R-sections at such corners are prone to bending (folding) because the deformation of the outer and inner parts of the R-section differs during the loading process.

[0045] While not particularly limited, the thickness H2 of the second part 222 (average length in the left, upper, and right parts) is preferably about 0.1 to 8 mm, more preferably 0.5 to 5 mm, and even more preferably 1 to 3 mm. By setting the thickness H2 to a predetermined value or less, the second part 222 takes on an elongated shape in the arrangement direction X (the protruding height Da becomes longer relative to the cross-sectional area). This makes it more susceptible to buckling. While not particularly limited, the ratio of the thickness H1 of the first part 221 to the thickness H2 of the second part 222 (H1 / H2) is greater than 1, preferably 1.2 to 10, more preferably 1.5 to 5, and even more preferably 2 to 4.

[0046] As shown in Figure 5, the hollow portion 220h is provided inside the peripheral wall portion 220w. In this embodiment, the hollow portion 220h has an outer shape that is approximately prismatic (approximately square-prism). The outer shape of the hollow portion 220h is the same as the outer shape of the cylindrical projection portion 220. However, in other embodiments, the outer shape of the hollow portion 220h may be cylindrical (including elliptical), or an approximately polygonal prism other than a prismatic (approximately triangular, approximately hexagonal, etc.). Furthermore, the outer shape of the hollow portion 220h may be different from that of the cylindrical projection portion 220.

[0047] As shown in Figure 6, the hollow portion 220h is approximately square in shape when viewed from the tip side of the cylindrical projection 220 in a plan view. More specifically, it is rectangular. However, in other embodiments, the hollow portion 220h may be approximately circular, semicircular, semielliptical, or an approximately polygonal shape other than a square (e.g., approximately triangular) in a plan view. In this specification, "approximately circular" is a term that includes not only a perfect circle (true circle) but also circular shapes where the curvature of the arc differs locally (e.g., an ellipse), and other shapes derived from a true circle or circle.

[0048] In this embodiment, the hollow portion 220h is provided off-center to one side from the center C of the cylindrical projection 220 in a plan view. In this case, the hollow portion 220h is provided off-center to the upper side in the height direction Z from the center C of the cylindrical projection 220. In some embodiments, as shown in Figure 6, when the cylindrical projection 220 is viewed from the tip side in a plan view, and the cylindrical projection 220 is divided into two regions by an axis CL passing through the center C of the cylindrical projection 220, it is preferable that the hollow portion 220h is off-center to one of the regions. In other words, it is preferable that the cylindrical projection 220 has an axis CL that passes through the center C of the cylindrical projection 220 and divides the cylindrical projection 220 into two equal parts, such that the hollow portion 220h is off-center to one of the two regions divided by the axis CL. In this case, the hollow portion 220h is located in the upper region when the cylindrical projection 220 is divided into two equal parts vertically in the height direction Z by the axis CL passing through the center C.

[0049] With this configuration, when a predetermined load is applied to the spacer 200 from the alignment direction X, the first portion 221 of the peripheral wall portion 220w is compressed, while the second portion 222 is buckled. Figure 7 shows the simulation results when the cylindrical projection 220 in Figure 5 is compressed. Figure 8 shows the simulation results when the cylindrical projection 220 in Figure 6 is compressed. Figure 9 is a schematic longitudinal cross-sectional view along the line IV-IV in Figure 8. Figures 7 to 9 show the simulation results when the cylindrical projection 220 is compressed to 50%.

[0050] As shown in Figures 7 to 9, when a load is applied to the cylindrical projection 220 from the alignment direction X, and the cylindrical projection 220 is compressed until its length in the alignment direction X (projection height Da) is reduced to 50% (compression ratio of 50%), the first part 221 is crushed in the alignment direction X, and its cross-section expands compared to the state before compression shown in Figures 5 and 6. In contrast, the second part 222 bends in an arc shape in the alignment direction X, as shown in Figure 9 in particular, and its cross-section becomes approximately C-shaped. In this embodiment, the load from the alignment direction X generates a force in the R part that spreads in the direction of the YZ plane. At this time, by making the thickness of the first part 221 as seen in the YZ plane thinner than that of the second part 222, this bending can be suitably generated. In the technology disclosed herein, the compression of the first part 221 and the second part 222 allows the energy storage device 100 to be stably pressed with a predetermined restraining load even when the energy storage device 100 expands, and the load necessary to maintain performance can be stably applied to the energy storage device 100. This will be explained in detail below.

[0051] In other words, as described in Patent Document 1, etc., energy storage devices can expand due to repeated charging and discharging. In particular, recent high-capacity energy storage devices tend to expand more significantly. As a result, the compression ratio of the spacer's protrusions tends to increase. When the compression ratio of the protrusions increases, as shown in Figure 10(A), the conventional "compression deformation" of the protrusions alone is insufficient to absorb the expansion of the energy storage device, and the reaction force on the energy storage device increases exponentially and rapidly. Furthermore, if the reaction force is made too small, there is a concern that the energy storage device will be more susceptible to damage from vibration and shock.

[0052] Therefore, the inventors devised a new method to absorb the expansion of the energy storage device and reduce the reaction force by "buckling" the protrusion. In other words, "buckling" is the phenomenon in which a material bends and folds when a buckling load is applied. Therefore, as shown in Figure 10(B), the inventors thought that the reaction force could be effectively reduced by "buckling" the protrusion when its compressibility increased. However, according to the inventors' investigation, "buckling" alone would, conversely, make the reaction force too small, causing the constraining load to decrease too much.

[0053] Therefore, in the technology disclosed herein, a cylindrical projection 220 is provided on the spacer 200, and when a predetermined load (buckling load) is applied from the alignment direction X, the second portion 222 of the cylindrical projection 220 is partially buckled. In other words, a portion that undergoes compression deformation and a portion that buckles are provided within a single cylindrical projection 220, combining the absorption of expansion by "compression deformation" and the absorption of expansion by "buckling".

[0054] As a result, as shown in the simulation results in Figure 11, in the embodiment of the technology disclosed herein (with partial buckling), when the energy storage device 100 expands after a charge-discharge cycle and the compressive force of the cylindrical projection 220 increases, the relative increase in reaction force compared to the comparative example (compressive deformation only) can be suppressed. As a result, the expansion of the energy storage device 100 can be absorbed without significantly reducing the restraining load (initial load), and the reaction force can be reduced. Therefore, the energy storage device 100 can be stably pressed with a predetermined restraining load, and the load necessary to maintain performance can be stably applied to the energy storage device 100. Furthermore, since the first part 221 does not buckle, the minimum necessary load can be secured even when the second part 222 buckles. In addition, since there is no need to enlarge the restraining mechanism in anticipation of an increase in reaction force, the energy density of the energy storage module 500 can be improved.

[0055] In some embodiments, it is preferable that each of the multiple cylindrical projections 220 does not have rotational symmetry (less than 360°) with respect to the center C of the cylindrical projection 220 as the center of symmetry when viewed from the tip side of the cylindrical projection 220 in a plan view. This makes it easier for the load to concentrate on the second portion 222 when a constraining load is applied from the alignment direction X, making the second portion 222 more prone to buckling.

[0056] In some embodiments, in a plan view of the cylindrical projection 220 from the tip side, the hollow portion 220h is approximately circular or polygonal in shape, and as shown in Figure 6, the center Ch of the hollow portion 220h is offset from the center C of the cylindrical projection 220. In Figure 6, the center Ch of the hollow portion 220h is offset upward from the center C of the cylindrical projection 220. In other words, when viewed in the YZ plane, there are parts that are thicker and parts that are thinner. As a result, when a constraint load is applied from the alignment direction X, the force generated in the YZ direction makes the second portion 222, which is thinner when viewed in the YZ plane, more prone to bending, and buckling is more likely to occur in the second portion 222.

[0057] Furthermore, as shown in Figure 4, the multiple cylindrical protrusions 220 are aligned in the width direction Y (first direction) and height direction Z (second direction), which intersect with the arrangement direction X. Specifically, they are aligned vertically and horizontally with a certain interval between them, so that there are multiple columns L1 to L4 in the width direction Y and multiple rows in the height direction Z. In each column L1 to L4 in the width direction Y, the multiple cylindrical protrusions 220 are arranged so that the hollow portion 220h is biased to the same side. Specifically, in the odd-numbered columns L1 and L3 in the width direction Y, the multiple cylindrical protrusions 220 are arranged so that the hollow portion 220h is biased to the upper side (one side) of the height direction Z. On the other hand, in the even-numbered columns L2 and L4 in the width direction Y, the multiple cylindrical protrusions 220 are arranged so that the hollow portion 220h is biased to the lower side (the other side) of the height direction Z. Multiple cylindrical protrusions 220 are arranged alternately in rows L1 to L4, rotated by 180°.

[0058] In some embodiments, it is preferable that, of two adjacent cylindrical protrusions 220 in the width direction Y (first direction) intersecting the array direction X, the first cylindrical protrusion 220 (for example, the cylindrical protrusions 220 of odd-numbered rows L1 and L3) has its hollow portion 220h biased toward the upper side (one side) of the height direction Z (second direction intersecting the first direction), and the second cylindrical protrusion 220 (for example, the cylindrical protrusions 220 of even-numbered rows L2 and L4) has its hollow portion 220h biased toward the lower side (the other side) of the height direction Z (second direction). By reversing the orientation of multiple cylindrical protrusions 220 with two adjacent cylindrical protrusions 220 in this way, it becomes easier to apply a load to the energy storage device 100 in a balanced manner in the planar direction even when the second portion 222 buckles.

[0059] The energy storage module 500 can be used for various applications, but it is particularly suitable for use as a power source (driving power supply) for motors mounted on vehicles such as passenger cars and trucks. The type of vehicle is not particularly limited, but examples include plug-in hybrid electric vehicles (PHEVs), hybrid electric vehicles (HEVs), and battery electric vehicles (BEVs).

[0060] Although preferred embodiments of the present invention have been described above, these embodiments are merely examples. The present invention can be implemented in various other forms. The present invention can be implemented based on the contents disclosed herein and common technical knowledge in the art. The technologies described in the claims include various modifications and changes to the embodiments illustrated above.

[0061] For example, in the embodiments shown in Figures 5 and 6 above, the outer shape of the cylindrical projection 220 was approximately prismatic. Also, the outer shape of the hollow portion 220h was approximately prismatic. The outer shape of the hollow portion 220h was the same as the outer shape of the cylindrical projection 220. The hollow portion 220h was approximately square in plan view. However, it is not limited to this. Figures 12(A) to (C) are diagrams corresponding to Figure 6 of a modified cylindrical projection.

[0062] <First Modified Example> As shown in Figure 12(A), the cylindrical projection 520 of the first modified example has a peripheral wall portion 520w and a hollow portion 520h surrounded by the peripheral wall portion 520w. Although not shown in the illustration, the cylindrical projection 520 has an outer shape that is approximately prismatic. Unlike the embodiment described above, the hollow portion 520h here has an outer shape that is approximately triangular. The outer shape of the hollow portion 520h is different from the outer shape of the cylindrical projection 520. The hollow portion 520h is approximately triangular in plan view. The hollow portion 520h is located off-center to the upper left from the center C of the cylindrical projection 520. The center Ch of the hollow portion 520h is shifted to the upper left from the center C of the cylindrical projection 520.

[0063] The peripheral wall portion 520w has a first portion 521 which is relatively thick and a second portion 522 which is relatively thin. The first portion 521 is substantially triangular in plan view. The first portion 521 is provided in a block shape on the lower right side of the hollow portion 520h. The second portion 522 is substantially L-shaped in plan view. The second portion 522 has a left portion provided in a strip shape with substantially uniform thickness along the height direction Z on the left side of the hollow portion 520h, and an upper portion provided in a strip shape with substantially uniform thickness along the width direction Y on the upper side of the hollow portion 520h. In this modified example, as shown in light gray in Figure 12(A), only the second portion 522 buckles when a predetermined load is applied from the arrangement direction X.

[0064] In some embodiments, when the cylindrical projection 520 is divided into two regions (equalized) by an axis CL passing through the center C of the cylindrical projection 520 in a plan view from the tip side of the cylindrical projection 220, it is preferable that the hollow portion 520h is provided in only one of the regions. In this case, the hollow portion 520h is provided only in the upper left region when the cylindrical projection 520 is diagonally divided into two equal parts by the axis CL. As a result, when a constraining load is applied from the alignment direction X, the second portion 522, which is formed thinly when viewed from the YZ plane, becomes more susceptible to bending in response to a force in the YZ direction generated in the R portion, similar to the embodiment in Figure 9, and buckling is more likely to occur in the second portion 522.

[0065] <Second Modified Example> As shown in Figure 12(B), the cylindrical projection 620 of the second modified example has a peripheral wall portion 620w and a hollow portion 620h surrounded by the peripheral wall portion 620w. Although not shown in the illustration, the cylindrical projection 620 has a cylindrical outer shape, unlike the embodiment described above. The hollow portion 620h has a semi-cylindrical outer shape, unlike the embodiment described above. The outer shape of the hollow portion 620h is different from the outer shape of the cylindrical projection 620. The hollow portion 620h is semi-circular in plan view. The hollow portion 520h is provided off-center above the center C of the cylindrical projection 520. More specifically, when the cylindrical projection 620 is divided into two equal parts vertically along the axis CL in the height direction Z, the hollow portion 520 is provided in the upper half of the region.

[0066] The peripheral wall portion 620w has a first portion 621 which is relatively thicker and a second portion 622 which is relatively thinner. The first portion 621 is substantially semicircular in plan view. The first portion 621 is provided in a block shape on the lower side of the hollow portion 620h. The first portion 621 is provided in the lower half of the area of ​​the cylindrical projection portion 620. The second portion 622 is substantially C-shaped in plan view. The second portion 622 is provided on the upper side of the hollow portion 620h, along the arc of the hollow portion 620h. In this modified example, as shown in light gray in Figure 12(B), only the second portion 622 buckles when a predetermined load is applied from the alignment direction X.

[0067] <Third Modification> As shown in Figure 12(C), the cylindrical projection 720 of the third modification has a peripheral wall portion 720w and a hollow portion 720h surrounded by the peripheral wall portion 720w. Unlike the second modification shown in Figure 12(B) above, the hollow portion 720h has a cylindrical outer shape. The hollow portion 720h is approximately circular in plan view. The hollow portion 720h is positioned off-center upward from the center C of the cylindrical projection 720. The center Ch of the hollow portion 720h is offset upward from the center C of the cylindrical projection 720.

[0068] The peripheral wall portion 720w has a first portion 721 which is relatively thicker and a second portion 722 which is relatively thinner. The thickness of the second portion 722 gradually increases as it approaches the first portion 721. In this modified example, as shown in light gray in Figure 12(C), when a predetermined load is applied from the alignment direction X, only the second portion 722 buckles.

[0069] As described above, specific embodiments of the technology disclosed herein include those described in the following sections. Item 1: An energy storage module comprising: a first energy storage device and a second energy storage device arranged along the direction of arrangement; a spacer disposed between the first energy storage device and the second energy storage device; and a restraining member that restrains the first energy storage device, the second energy storage device and the spacer in the direction of arrangement, wherein the spacer comprises a flat base portion and a plurality of cylindrical projections protruding from the base portion toward the first energy storage device, each of the plurality of cylindrical projections having a peripheral wall portion extending toward the first energy storage device and a hollow portion surrounded by the peripheral wall portion, the peripheral wall portion having a first portion with a relatively thicker thickness and a second portion with a relatively thinner thickness, the hollow portion being provided offset to one side from the center of the cylindrical projections in a plan view, and configured such that when a predetermined load is applied from the direction of arrangement, the first portion of the peripheral wall portion is compressed and deformed, while the second portion is buckled. Item 2: The energy storage module according to Item 1, wherein each of the plurality of cylindrical protrusions does not have rotational symmetry with respect to the center of the cylindrical protrusion as the center of symmetry in a plan view. Item 3: The energy storage module according to item 1 or 2, wherein, in a plan view, the hollow portion is substantially circular or substantially polygonal in shape, and the center of the hollow portion is offset from the center of the cylindrical projection. Item 4: The energy storage module according to any one of items 1 to 3, wherein, in a plan view, when the cylindrical projection is divided into two regions by an axis passing through the center of the cylindrical projection, the hollow portion is provided in only one of the regions. Item 5: The energy storage module according to any one of items 1 to 4, wherein, of two adjacent cylindrical projections in a first direction intersecting the above-mentioned arrangement direction, the first cylindrical projection has its hollow portion biased toward one side of the second direction intersecting the above-mentioned first direction, and the second cylindrical projection has its hollow portion biased toward the other side of the second direction. Item 6: A spacer for an energy storage module, which is disposed between a first energy storage device and a second energy storage device arranged along the direction of arrangement, comprising a flat base portion and a plurality of cylindrical projections protruding from the base portion toward the first energy storage device, wherein each of the plurality of cylindrical projections has a peripheral wall portion extending toward the first energy storage device and a hollow portion surrounded by the peripheral wall portion, the peripheral wall portion has a first portion that is relatively thick and a second portion that is relatively thin, the hollow portion is provided offset to one side from the center of the cylindrical projection portion in a plan view, and is configured such that when a predetermined load is applied from the direction of arrangement, the first portion of the peripheral wall portion is compressed and deformed, while the second portion is buckled. [Explanation of Symbols]

[0070] 10 Battery Case 20 Electrode body 100 Energy Storage Devices 200 Spacer 210 Base section 220 Cylindrical projection 220h hollow part 220w peripheral wall part 221 Part 1 222 Part 2 300 Restraint mechanism 500 Energy Storage Modules X Thickness direction (arrangement direction) Y width direction (first direction) Z: Height direction (second direction)

Claims

1. A first energy storage device and a second energy storage device arranged along the direction of the arrangement, A spacer is placed between the first energy storage device and the second energy storage device, A restraining mechanism that restrains the first energy storage device, the second energy storage device, and the spacer in the direction of arrangement, Equipped with, The spacer comprises a flat base portion and a plurality of cylindrical protrusions projecting from the base portion toward the first energy storage device. Each of the multiple cylindrical protrusions has a peripheral wall portion extending toward the first energy storage device and a hollow portion surrounded by the peripheral wall portion. The peripheral wall portion has a first portion that is relatively thick and a second portion that is relatively thin. The aforementioned hollow portion is provided off-center to one side of the center of the cylindrical projection when viewed from above. When a predetermined load is applied from the aforementioned direction of arrangement, the first portion of the peripheral wall is compressed and deformed, while the second portion is buckled. Energy storage module.

2. Each of the aforementioned cylindrical protrusions does not have rotational symmetry with respect to the center of the cylindrical protrusion as the center of symmetry in a plan view. The energy storage module according to claim 1.

3. In a plan view, the hollow portion is approximately circular or polygonal in shape, and the center of the hollow portion is offset from the center of the cylindrical projection. The energy storage module according to claim 1.

4. In a plan view, when the cylindrical projection is divided into two regions by an axis passing through the center of the cylindrical projection, the hollow portion is provided in only one of the regions. The energy storage module according to claim 1.

5. Of the two adjacent cylindrical protrusions in the first direction intersecting the aforementioned arrangement direction, The first cylindrical projection is provided biased toward one side of the second direction in which the hollow portion intersects the first direction. The second cylindrical projection is provided such that the hollow portion is biased toward the other side in the second direction. The energy storage module according to claim 1.

6. A spacer for an energy storage module, which is positioned between a first energy storage device and a second energy storage device arranged along the direction of arrangement, It comprises a flat base portion and a plurality of cylindrical protrusions that project from the base portion toward the first energy storage device, Each of the multiple cylindrical protrusions has a peripheral wall portion extending toward the first energy storage device and a hollow portion surrounded by the peripheral wall portion. The peripheral wall portion has a first portion that is relatively thick and a second portion that is relatively thin. The aforementioned hollow portion is provided off-center to one side of the center of the cylindrical projection when viewed from above. When a predetermined load is applied from the aforementioned direction of arrangement, the first portion of the peripheral wall is compressed and deformed, while the second portion is buckled. Spacers for energy storage modules.

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