Busbars and Energy Storage Units

Abstract

To relieve stress applied to a joint between a bus bar and a terminal.SOLUTION: A bus bar 1 disclosed herein includes a first bonding region 10 bonded to a terminal portion 144 of a first power storage device 100A, a second bonding region 20 bonded to a terminal portion 144 of a second power storage device 100B different from the first power storage device 100A, and a bridging region 30 connecting the first bonding region 10 and the second bonding region 20. At least one of the first bonding region 10 and the second bonding region 20 is provided with buffer portions 12, 22 that absorb stress S caused by fluctuations in the gap G between the first bonding region 10 and the second bonding region 20. The bus bar 1 configured in this manner can reduce stress on bonding portions W1, W2 between the bus bar 1 and the terminal portion 144.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present disclosure relates to a busbar and an energy storage unit. [Background technology]

[0002] Energy storage devices such as lithium-ion secondary batteries are used as power sources for a variety of electrical appliances. In such cases, a power storage unit may be constructed by connecting multiple energy storage devices via a bus bar. An example of such a bus bar is disclosed in Patent Document 1 (JP 2020-021628 A). The bus bar described in Patent Document 1 is a conductive member that connects multiple terminals. This bus bar is made up of multiple stacked conductive plates, and has curved portions that curve in the stacking direction of the conductive plates between multiple connection portions that are connected to multiple terminals. A bus bar with such a configuration has curved portions that deform when stress is applied, allowing it to follow fluctuations in the distance between terminals due to expansion and contraction of the cells (energy storage devices). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2020-021628 Summary of the Invention [Problem to be solved by the invention]

[0004] Generally, busbars are joined to the terminals of an electric storage device by laser welding, resistance welding, or the like. When the distance between the terminals fluctuates due to expansion and contraction of the electric storage device, stress may be applied not only to the busbar itself but also to the joints between the busbar and the terminals. As described above, the busbar described in Patent Document 1 can alleviate stress applied to the busbar itself by using the curved portion between the two joints. However, with a busbar configured in this way, it is difficult to alleviate stress applied to the joints between the busbar and the terminals. [Means for solving the problem]

[0005] To address the above-mentioned problems, a bus bar having the following configuration is provided.

[0006] The busbar disclosed herein has a first joint region joined to a terminal portion of a first power storage device, a second joint region joined to a terminal portion of a second power storage device different from the first power storage device, and a bridging region connecting the first and second joint regions. In this busbar, at least one of the first and second joint regions is provided with a buffer portion that absorbs stress caused by variations in the distance between the first and second joint regions.

[0007] In the busbar having the above configuration, at least one of the first and second joint regions is provided with a buffer portion that absorbs stress caused by variations in the distance between the first and second joint regions, thereby preventing stress caused by variations in the distance between the two joint regions from being applied to the joint between the busbar and the terminal portion. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a perspective view schematically illustrating a bus bar according to a first embodiment. [Figure 2] FIG. 2 is a cross-sectional view schematically illustrating the connection between the bus bar shown in FIG. 1 and the terminal portion of the electricity storage device. [Figure 3] FIG. 3 is a perspective view schematically showing the power storage unit according to the first embodiment. [Figure 4] FIG. 4 is a perspective view schematically showing the electricity storage device in FIG. [Figure 5] FIG. 5 is an enlarged cross-sectional view schematically showing the structure in the vicinity of the terminal mounting hole of the electricity storage device shown in FIG. [Figure 6] FIG. 6 is an enlarged cross-sectional view illustrating a procedure for producing the insulating material in FIG. [Figure 7] FIG. 7 is an enlarged cross-sectional view schematically showing the connection structure of the power storage unit shown in FIG. [Figure 8] FIG. 8 is a cross-sectional view schematically showing the joining of a bus bar and a terminal portion of an electricity storage device according to another embodiment. [Figure 9] FIG. 9 is a plan view of a bus bar according to another embodiment. [Figure 10] FIG. 10 is a plan view of a bus bar according to another embodiment. [Figure 11] FIG. 11 is a plan view of a bus bar according to another embodiment. [Figure 12] FIG. 12 is an enlarged cross-sectional view schematically showing the structure in the vicinity of a terminal mounting hole of an electricity storage device of an electricity storage unit according to another embodiment. [Figure 13] FIG. 13 is an enlarged cross-sectional view schematically showing the structure in the vicinity of a terminal mounting hole of an electricity storage device of an electricity storage unit according to another embodiment. [Figure 14] FIG. 14 is an enlarged cross-sectional view schematically showing the structure in the vicinity of a terminal mounting hole of an electricity storage device of an electricity storage unit according to another embodiment. [Figure 15] FIG. 15 is an enlarged cross-sectional view schematically showing a connection structure of an electricity storage unit according to another embodiment. [Figure 16] FIG. 16 is an enlarged cross-sectional view schematically showing a connection structure of an electricity storage unit according to another embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, embodiments of the technology disclosed herein will be described with reference to the drawings. It should be noted that matters other than those specifically mentioned in this specification that are necessary for implementing the technology disclosed herein (e.g., the detailed configuration of the electrode body) can be understood as design matters for a person skilled in the art based on the prior art in the relevant field. The technology disclosed herein can be implemented based on the content disclosed in this specification and common technical knowledge in the relevant field. Furthermore, the expression "A to B" indicating a range in this specification is intended to include the meaning of "greater than A" and "smaller than B" as well as the meaning of "greater than A" and "smaller than B."

[0010] In this specification, the term "electricity storage device" refers to a concept that encompasses devices in which charge and discharge reactions occur due to the movement of charge carriers between a pair of electrodes (positive and negative electrodes). That is, the electricity storage device in the technology disclosed herein encompasses secondary batteries such as lithium ion secondary batteries, nickel-metal hydride batteries, and nickel-cadmium batteries, as well as capacitors such as lithium ion capacitors and electric double layer capacitors.

[0011] First Embodiment 1. Busbar configuration An embodiment of the busbar disclosed herein will be described below with reference to FIGS. 1 and 2. FIG. 1 is a perspective view schematically illustrating a busbar according to a first embodiment. FIG. 2 is a cross-sectional view schematically illustrating the connection between the busbar shown in FIG. 1 and the terminal portion of an electricity storage device. The symbols L, R, F, Rr, U, and D in the drawings represent left, right, front, rear, top, and bottom, respectively. The symbols X, Y, and Z in the drawings represent the width, depth, and height directions of the busbar, respectively. However, these directions are defined merely for the sake of convenience and do not limit the use of the busbar disclosed herein. For the sake of convenience, FIG. 2 shows only the terminal portions 144 of the first electricity storage device 100A and the second electricity storage device 100B, omitting other portions.

[0012] 1 and 2, the busbar 1 according to this embodiment includes a first joint region 10 joined to a terminal portion 144 of a first power storage device 100A, a second joint region 20 joined to a terminal portion 144 of a second power storage device 100B different from the first power storage device 100A, and a bridging region 30 connecting the first joint region 10 and the second joint region 20. The busbar 1 also includes buffer portions 12, 22 in the first and second joint regions 10, 20, which absorb stress S caused by fluctuations in the gap G between the first and second joint regions 10, 20. This reduces stress on joint regions W1, W2 between the busbar 1 and the terminal portion 144. A busbar 1 having such a configuration will now be described in detail.

[0013] (1) Overall structure As shown in FIG. 2 , the busbar 1 according to this embodiment is a conductive member that connects the terminal portions 144 of two power storage devices (a first power storage device 100A and a second power storage device 100B). The material of the busbar 1 only needs to have a certain level of conductivity, and any conventionally known conductive material can be used without any particular limitation. Examples of materials for the busbar 1 include metal materials such as aluminum, copper, iron, zinc, silver, and nickel. The busbar 1 may also be made of an alloy of these metals. The busbar 1 may also be a clad material in which multiple layers made of different metal materials are laminated. Note that, in consideration of the bondability with the terminal portions 144 of the power storage devices, the busbar 1 is preferably made of the same metal material as the terminal portions 144. For example, aluminum or an aluminum alloy is used for the positive electrode terminal portion 144 of the power storage devices. In this case, the busbar 1 is preferably made of aluminum or an aluminum alloy.

[0014] The busbar 1 according to this embodiment has a first joint region 10, a second joint region 20, and a bridging region 30. Specifically, the busbar 1 shown in FIG. 1 is a long, plate-like member extending along the width direction X. In this busbar 1, the first joint region 10, the bridging region 30, and the second joint region 20 are arranged in this order from the left L to the right R in the width direction X. Each region will be described below.

[0015] (2) First joining area 10 The first joint region 10 is a region that is joined to the terminal portion 144 of the first power storage device 100A. As shown in FIG. 1, the first joint region 10 is formed at one end (left side L) in the width direction X of the busbar 1. As shown in FIG. 2, a part of the first joint region 10 (a contact portion 14 described below) is joined to the terminal portion 144 of the first power storage device 100A. A conventionally known joining process (laser welding, resistance welding, ultrasonic joining, etc.) is used to join the first joint region 10 to the terminal portion 144. As a result, a joint W1 that straddles the first joint region 10 (contact portion 14) and the terminal portion 144 is formed. Although not shown in the drawings, the joint W1 is annular in plan view.

[0016] In the busbar 1 according to this embodiment, the first joint region 10 is provided with a buffer portion 12 that absorbs stress S caused by fluctuations in the gap G between the first joint region 10 and the second joint region 20. This makes it possible to suppress the stress S applied to the joint region W1. An example of the structure of the buffer portion 12 will be described below.

[0017] First, the first joint region 10 has a plate-shaped joint base portion. Hereinafter, the joint base portion in the first joint region 10 will be referred to as the "first base portion 11." Then, in this embodiment, the buffer portion 12 is configured as a step protruding from the first base portion 11. Specifically, the step-shaped buffer portion 12 protrudes from the first base portion 11 toward the terminal portion 144 of the first electricity storage device 100A (i.e., downward D in the height direction Z). This step-shaped buffer portion 12 deforms when a stress S is applied along the width direction X, and therefore, the stress S can be prevented from being directly applied to the joint W1.

[0018] More specifically, the stepped buffer 12 has a protruding portion 13 that protrudes downward D from the first base 11, and a contact portion 14 that is provided at a tip (lower end) 13a of the protruding portion 13 and that comes into contact with the terminal 144. The contact portion 14 is a plate-like member that extends along the planar direction (the width direction X and the depth direction Y). The bonded portion W1 on the first bonded region 10 side extends in the height direction Z so as to straddle the contact portion 14 and the terminal 144. The protruding portion 13 also extends in the height direction Z so as to connect the contact portion 14 and the first base 11. The buffer 12 configured as described above can particularly effectively relieve the stress S on the bonded portion W1. More specifically, this is as follows. First, when the first power storage device 100A or the second power storage device 100B expands or contracts, the distance G between the first bonded region 10 and the second bonded region 20 changes. As a result, stress S is applied to the first bonding region 10 in the planar direction (the width direction X and the depth direction Y). However, the buffer section 12 according to this embodiment includes a protrusion 13 extending in the height direction Z. This protrusion 13 deforms preferentially when stress S is applied in the planar direction, and can absorb the stress S. This makes it possible to prevent stress S in the width direction X from being applied to the bonding region W1 extending in the height direction Z.

[0019] It is preferable that the thickness t1 of the protrusion 13 (the dimension of the protrusion 13 in the width direction X) is thinner than the thickness t2 of the contact portion 14 (the dimension of the contact portion 14 in the height direction Z). This allows the protrusion 13 to deform more preferentially, thereby more suitably alleviating the stress S on the joint W1. Specifically, when the thickness t2 of the contact portion 14 is taken as 100%, the thickness t1 of the protrusion 13 is preferably 90% or less, more preferably 85% or less, even more preferably 80% or less, and particularly preferably 75% or less. This allows the protrusion 13 to deform more easily in response to the stress S along the width direction X. On the other hand, the ratio of the thickness t1 of the protrusion 13 to the thickness t2 of the contact portion 14 is preferably 45% or more, more preferably 50% or more, even more preferably 55% or more, and particularly preferably 60% or more. This allows the protrusion 13 to have sufficient strength.

[0020] Furthermore, the specific numerical value of the thickness t2 of the contact portion 14 is preferably 0.1 mm or more, more preferably 0.2 mm or more, even more preferably 0.3 mm or more, and particularly preferably 0.5 mm or more. This ensures sufficient strength of the contact portion 14. On the other hand, the thickness t2 of the contact portion 14 is preferably 3.5 mm or less, more preferably 3.0 mm or less, even more preferably 2.5 mm or less, and particularly preferably 2.0 mm or less. This makes it possible to easily form the joint W1 spanning the contact portion 14 and the terminal portion 144.

[0021] Furthermore, the height h1 of the protrusion 13 is preferably 1.0 mm or more, more preferably 1.5 mm or more, and particularly preferably 2.0 mm or more. This makes the protrusion 13 more susceptible to deformation in response to the stress S in the planar direction, thereby more preferably alleviating the stress S on the joint W1. On the other hand, from the viewpoint of reducing the total height of the energy storage unit 500 (see FIG. 3 ) when the bus bar 1 is attached, the height h1 of the protrusion 13 is preferably 3.0 mm or less, and more preferably 2.0 mm or less. This improves the loading efficiency when the energy storage unit is mounted on an electrical product (such as an electric vehicle).

[0022] 1, the buffer portion 12 in this embodiment is a recess having a substantially circular planar shape. Specifically, the buffer portion 12 shown in FIG. 1 has a cylindrical protrusion 13 that protrudes downward D from the first base portion 11. The contact portion 14 shown in FIG. 1 is a disk-shaped member that closes the opening of the cylindrical protrusion 13 at the lower portion D. The buffer portion 12 having such a substantially circular planar shape can deform the protrusion 13 in various directions in the planar direction, thereby more appropriately alleviating the stress S on the joint W1.

[0023] Furthermore, the inner diameter d1 of the cylindrical protrusion 13 is preferably 10 mm or more, more preferably 15 mm or more, and particularly preferably 20 mm or more. This ensures a sufficient welding area, thereby increasing the reliability of the joint W1. On the other hand, from the viewpoint of reducing the size of the busbar 1 and the weight of the electricity storage device, the inner diameter d1 of the protrusion 13 is preferably 25 mm or less, and more preferably 20 mm or less.

[0024] (2)Second bonding area 20 The second joint region 20 is a region that is joined to a terminal portion 144 of a second power storage device 100B that is different from the first power storage device 100A. The second joint region 20 is formed at the other end (right side R) in the width direction X of the busbar 1. Similarly to the first joint region 10, a joint portion W2 that straddles the second joint region 20 and the terminal portion 144 is formed in a part (contact portion 24) of the second joint region 20.

[0025] In the busbar 1 according to this embodiment, a buffer portion 22 is also provided in the second joint region 20. The buffer portion 22 in the second joint region 20 has substantially the same structure as the buffer portion 12 in the first joint region 10 described above. Specifically, the second joint region 20 has a plate-shaped joint base portion (second base portion 21). The buffer portion 22 in the second joint region 20 is also configured as a step that protrudes downward D from the second base portion 21. More specifically, the buffer portion 22 has a protruding portion 23 that protrudes downward D from the second base portion 21 and a contact portion 24 that is provided at a lower end 23a of the protruding portion 23 and comes into contact with the terminal portion 144. The buffer portion 22 configured as described above can effectively absorb stress S in the planar direction, thereby reducing stress S applied to the joint portion W2 in the second joint region 20.

[0026] As described above, the buffer section 22 of the second bonding region 20 has substantially the same structure as the buffer section 12 of the first bonding region 10. Therefore, the dimensions of each component constituting the buffer section 22 of the second bonding region 20 can be appropriately set from the same perspective as the buffer section 12 of the first bonding region 10 described above. Therefore, redundant explanations will be omitted in this specification. However, the dimensions of each of the buffer sections 12, 22 are changed appropriately depending on the shape of the terminal section 144 to be bonded, and do not need to be completely identical. In other words, the buffer section 22 of the second bonding region 20 may have dimensions different from those of the buffer section 12 of the first bonding region 10.

[0027] (3) Crosslinked region The bridging region 30 is a region that connects the first bonding region 10 and the second bonding region 20. The bridging region 30 bridges the first bonding region 10 and the second bonding region 20, thereby electrically connecting the first power storage device 100A and the second power storage device 100B.

[0028] Furthermore, the bridging region 30 in this embodiment has a fluctuation absorbing portion 32 that absorbs fluctuations in the gap G between the first bonding region 10 and the second bonding region 20. This reduces stress applied to the busbar 1 itself. Specifically, the bridging region 30 in this embodiment has a plate-shaped bridging base portion 31. The fluctuation absorbing portion 32 is configured as a step that protrudes from the bridging base portion 31. More specifically, the fluctuation absorbing portion 32 has a protruding portion 33 that protrudes upward U from the bridging base portion 31 and a flat-plate-shaped connecting portion 34 provided on an upper end 33a of the protruding portion 33. The fluctuation absorbing portion 32 configured as described above can preferentially deform the protruding portion 33 when the gap G between the first bonding region 10 and the second bonding region 20 varies, thereby reducing stress applied to the busbar 1 itself.

[0029] It is preferable that the thickness t3 (dimension in the width direction X) of the protruding portion 33 of the crosslinked region 30 is thinner than the thickness t4 (dimension in the height direction Z) of the connecting portion 34. This makes the protruding portion 33 of the crosslinked region 30 more easily deformable. Specifically, when the thickness t4 of the connecting portion 34 is taken as 100%, the thickness t3 of the protruding portion 33 is preferably 90% or less, more preferably 85% or less, even more preferably 80% or less, and particularly preferably 75% or less. On the other hand, the ratio of the thickness t3 of the protruding portion 33 to the thickness t4 of the connecting portion 34 is preferably 50% or more, more preferably 55% or more, and particularly preferably 60% or more. This ensures sufficient strength of the protruding portion 33.

[0030] Specifically, the thickness t4 of the connecting portion 34 is preferably 0.1 mm or more, more preferably 0.25 mm or more, and particularly preferably 0.5 mm or more. This ensures sufficient strength of the connecting portion 34. On the other hand, the upper limit of the thickness t4 of the connecting portion 34 is preferably 3.0 mm or less, more preferably 2.5 mm or less, and particularly preferably 2.0 mm or less. This makes the bridging region 30 (the protrusion 33, the connecting portion 34) more easily deformable, thereby reducing the stress S applied to the first bonding region 10 and the second bonding region 20.

[0031] Furthermore, the height h2 of the protruding portion 33 of the bridging region 30 is preferably 1.0 mm or more, more preferably 1.5 mm or more, even more preferably 2.0 mm or more, and particularly preferably 2.5 mm or more. This makes the protruding portion 33 of the bridging region 30 more likely to deform. On the other hand, the height h2 of the protruding portion 33 of the bridging region 30 is preferably 5.0 mm or less, more preferably 4.0 mm or less, and particularly preferably 3.0 mm or less. This allows the total height of the electricity storage unit 500 (see FIG. 3) to be reduced, thereby improving loading efficiency when the electricity storage unit 500 is mounted on an electrical product (such as an electric vehicle).

[0032] 1, the fluctuation absorbing portion 32 in this embodiment is a band-shaped step formed over the entire area of ​​the bridge region 30 in the depth direction Y. In other words, the fluctuation absorbing portion 32 has a pair of protruding portions 33 that protrude upward U from the entire area of ​​the bridge base portion 31 in the depth direction Y. The pair of protruding portions 33 face each other in the width direction X. A connecting portion 34, which is a substantially rectangular plate-shaped member, is provided to connect the upper ends 33a of the pair of protruding portions 33. The fluctuation absorbing portion 32 configured as described above can sufficiently absorb large stresses along the width direction X, and can therefore prevent the stress from affecting the first bonding region 10 and the second bonding region 20.

[0033] Furthermore, the width dimension W1 of the connecting portion 34 is not particularly limited and can be adjusted as appropriate taking into consideration the dimensions of the first electricity storage device 100A and the second electricity storage device 100B, their installation positions, etc. For example, the lower limit of the width dimension W1 of the connecting portion 34 may be 10 mm or more, 15 mm or more, or 20 mm or more. On the other hand, the upper limit of the width dimension w1 of the connecting portion 34 may be 70 mm or less, 60 mm or less, or 50 mm or less.

[0034] The structure of the busbar 1 according to this embodiment has been described above. As mentioned above, the busbar 1 having such a configuration includes buffer portions 12, 22 that absorb stress S caused by variations in the gap G between the first joint region 10 and the second joint region 20. This makes it possible to prevent stress S from being applied to joint portions W1, W2 between the busbar 1 and the terminal portion 144.

[0035] 2. Configuration of the energy storage unit Next, an energy storage unit 500 using the bus bar 1 having the above configuration will be described. Fig. 3 is a perspective view schematically showing an energy storage unit according to a first embodiment. Fig. 4 is a perspective view schematically showing an energy storage device in Fig. 3. Fig. 5 is an enlarged cross-sectional view schematically showing a structure in the vicinity of a terminal mounting hole of the energy storage device shown in Fig. 4. Fig. 6 is an enlarged cross-sectional view illustrating a procedure for producing the insulating material in Fig. 5. Fig. 7 is an enlarged cross-sectional view schematically showing a connection structure of the energy storage unit shown in Fig. 3.

[0036] (1) Electricity storage device 100 The power storage unit 500 shown in Fig. 3 includes a plurality of power storage devices 100. Specifically, flat, rectangular power storage devices 100 are used in this power storage unit 500. The plurality of power storage devices 100 are arranged along the width direction X with their flat surfaces facing each other. The number of power storage devices 100 included in the power storage unit 500 is not particularly specified, and may be changed as appropriate depending on the purpose of the power storage unit 500 (such as the required power and specifications of the electrical appliances to be used).

[0037] 4 and 5, the electricity storage device 100 includes an electrode assembly 110, a case 120, an insulating material 130, and a current collector 140. An example of the structure of the electricity storage device 100 will now be described.

[0038] (1-1) Electrode body 110 The electrode assembly 110 is a power generating element of the power storage device 100. The power storage device 100 shown in FIG. 5 includes one electrode assembly 110. However, the number of electrode assemblies is not particularly limited and may be multiple. Although detailed illustrations are omitted, the electrode assembly 110 includes a positive electrode plate, a negative electrode plate, and a separator. The positive electrode plate includes a positive electrode core that is a conductive metal foil (such as aluminum foil) and a positive electrode active material layer applied to the surface of the positive electrode core. On the other hand, the negative electrode plate includes a negative electrode core that is a conductive metal foil (such as copper foil) and a negative electrode active material layer applied to the surface of the negative electrode core. The separator is an insulating sheet interposed between the positive electrode plate and the negative electrode plate. Note that the materials of the components (positive electrode plate, negative electrode plate, separator, etc.) that make up the electrode assembly 110 can be materials that can be used in general power storage devices without particular limitations, and detailed description thereof will be omitted as they do not limit the technology disclosed herein.

[0039] The specific structure of the electrode assembly 110 is not particularly limited. For example, the electrode assembly 110 may be a wound electrode assembly formed by winding a laminate including a positive electrode plate, a negative electrode plate, and a separator. The electrode assembly 110 may also be a laminated electrode assembly formed by stacking multiple positive electrode plates, multiple negative electrode plates, and multiple separators. Regardless of the structure employed, connection tabs 112 are formed on both side edges of the electrode assembly 110 in the depth direction Y. One of the connection tabs 112 is a positive electrode tab electrically connected to the positive electrode plate. This positive electrode tab is formed, for example, by bundling positive electrode cores that are not coated with a positive electrode active material layer. The other connection tab 112 is a negative electrode tab electrically connected to the negative electrode plate. This negative electrode tab is formed by bundling negative electrode cores that are not coated with a negative electrode active material layer. As will be described in detail later, these connection tabs 112 are electrically connected to the current collector 140.

[0040] (1-2) Case 120 The case 120 is a container that houses the electrode assembly 110 and has a terminal mounting hole 125. Specifically, the case 120 is a flat, box-shaped container with an internal space. The electrode assembly 110 is housed in the internal space of the case 120. Although not shown in the drawings, an electrolyte is also housed inside the case 120. The electrolyte can be any electrolyte that can be used in general electricity storage devices without any particular restrictions, and as this does not limit the technology disclosed herein, a detailed description will be omitted.

[0041] The case 120 also includes a case main body 122 and a sealing plate 124. The case main body 122 is a box-shaped body with an upper opening. As shown in FIG. 4, the case main body 122 includes a bottom 122b that is a long rectangular plate-like member, a pair of first side walls 122c that extend upward D from long sides (sides along the depth direction Y) of the bottom 122b, and a pair of second side walls 122d that extend upward D from short sides (sides along the width direction X) of the bottom 122b. An upper opening is formed on the upper surface of the case main body 122, surrounded by the upper ends of the first side wall 122c and the second side wall 122d. Meanwhile, the sealing plate 124 is a rectangular plate-like member that closes the upper opening of the case main body 122. Specifically, as shown in FIG. 5, the sealing plate 124 is fitted into the upper opening of the case main body 122. The boundary between case body 122 and sealing plate 124 is joined by laser welding or the like. It is preferable that case 120 (case body 122 and sealing plate 124) is a metal member having a certain level of strength or more. Examples of materials for case 120 include metal materials such as aluminum and aluminum alloys.

[0042] As described above, the case 120 is formed with a terminal mounting hole 125. This terminal mounting hole 125 is a through-hole that penetrates the case 120. This terminal mounting hole 125 serves as an opening for forming a conductive path from the electrode assembly 110 inside the case 120 to the outside of the case 120. As shown in FIG. 4, the terminal mounting hole 125 is a circular opening in a plan view. However, the planar shape of the terminal mounting hole is not particularly limited and may be rectangular. In addition, in the power storage device 100 shown in FIG. 4, two terminal mounting holes 125 are formed in the sealing plate 124 of the case 120. Specifically, the terminal mounting holes 125 are formed at both ends of the sealing plate 124 in the depth direction Y. One of the terminal mounting holes 125 serves as a positive electrode terminal mounting hole 125P that forms a conductive path with the positive electrode of the electrode assembly 110. The other terminal mounting hole 125 serves as a negative electrode terminal mounting hole 125N that forms a conductive path with the negative electrode of the electrode body 110. The following describes the structure around the negative electrode terminal mounting hole 125N as an example.

[0043] (1-3) Insulation 130 The insulating material 130 continuously covers the peripheral wall 125a of the terminal mounting hole 125 and the peripheral edges 120a1 and 120b1 of the terminal mounting hole 125 in the circumferential direction and is joined to the peripheral edges 120a1 and 120b1 of the terminal mounting hole 125. The insulating material 130 is a member for preventing electrical continuity to the case 120. Specifically, a current collector 140 that forms a conductive path from the electrode assembly 110 to the outside of the case 120 is attached inside the case 120. As shown in FIG. 3 , a bus bar 1 is attached to the outside of the case 120. By interposing the insulating material 130 between these conductive members and the case 120, electrical continuity to the case 120 can be prevented. The insulating material 130 is made of an insulating resin such as polypropylene resin, polyphenylene sulfide resin, polyamide resin, polyacetal resin, or polyimide resin. Additionally, the insulating material 130 has an opening 138 penetrating the insulating material 130. The insulating material 130 is formed so that the opening 138 and the terminal mounting hole 125 overlap. In other words, the insulating material 130 is arranged so as not to block the terminal mounting hole 125 of the case 120.

[0044] The insulating material 130 shown in FIG. 5 is produced by insert molding. In this insert molding, first, as shown in FIG. 6, the current collector 140 and a mold M are attached to the sealing plate 124. At this time, the positional relationship of each component is adjusted so that a cavity S1 having a shape corresponding to the insulating material 130 to be produced is formed. Next, a resin material is filled into the cavity S1 through an injection hole M1 of the mold M. The resin material is then cured to produce the insulating material 130 having a shape corresponding to the cavity S1. When the insulating material 130 is produced by insert molding in this manner, the sealing plate 124 and the current collector 140 are integrated via the insulating material 130. As a result, the insulating material 130 continuously covers the peripheral wall 125a of the terminal mounting hole 125 and the peripheral edges 120a1 and 120b1 of the terminal mounting hole 125 in the circumferential direction and is bonded to the peripheral edges 120a1 and 120b1 of the terminal mounting hole 125. After insert molding, the insulating material 130 has an outer insulating portion 132, an inner insulating portion 134, and an in-hole insulating portion 136. The specific shape of each portion will be described below.

[0045] The insulating material 130 includes an external insulating portion 132 bonded to a peripheral portion 120a1 of the terminal mounting hole 125 on the outer surface 120a of the case 120. The external insulating portion 132 prevents electrical continuity between the bus bar 1 and the case 120. Specifically, the external insulating portion 132 is a plate-shaped portion disposed along the outer surface 120a of the case 120 (the upper surface 124a of the sealing plate 124). The lower surface 132a of the external insulating portion 132 is bonded to the outer surface 120a of the case 120 by insert molding. As shown in FIG. 7 , the provision of the external insulating portion 132 prevents the bus bar 1 from contacting the case 120 (the sealing plate 124). The thickness of the external insulating portion 132 is preferably 0.5 mm or more, more preferably 1.0 mm or more, and particularly preferably 2.0 mm or more. This more effectively prevents electrical continuity between the bus bar 1 and the case 120. On the other hand, the thickness of the outer insulating part 132 is preferably 4.0 mm or less, and more preferably 3.0 mm or less, which allows the height dimension of the electricity storage device 100 to be further reduced, thereby further improving the loading efficiency of the electricity storage device in an electrical product.

[0046] The insulating material 130 also includes an internal insulating portion 134 joined to a peripheral portion 120b1 of the terminal mounting hole 125 on the internal surface 120b of the case 120. The internal insulating portion 134 is a member that prevents electrical conduction between the case 120 and the current collector 140 (described later). Specifically, the internal insulating portion 134 is a plate-shaped portion interposed between the internal surface 120b of the case 120 (the lower surface 124b of the sealing plate 124) and the joint portion 142 of the current collector 140. The upper surface 134a of the internal insulating portion 134 is joined to the internal surface 120b of the case 120 by insert molding. The thickness of the internal insulating portion 134 is preferably 0.1 mm or more, more preferably 0.3 mm or more, and particularly preferably 0.5 mm or more. This more effectively prevents electrical conduction between the current collector 140 and the sealing plate 124. On the other hand, the thickness of the internal insulating portion 134 is preferably 2.0 mm or less, and more preferably 1.0 mm or less. This increases the space for accommodating the electrode assembly 110 within the case 120, which can contribute to improving the performance of the electricity storage device 100.

[0047] The insulating material 130 includes an in-hole insulating portion 136 that is joined to the peripheral wall 125a of the terminal mounting hole 125. As will be described in detail later, in this energy storage unit 500, the buffer portions 12, 22 of the bus bar 1 are inserted into the terminal mounting hole 125, and the contact portions 14, 24 of the bus bar 1 are joined to the terminal portion 144. The in-hole insulating portion 136 prevents the buffer portions 12, 22 inserted into the terminal mounting hole 125 from coming into direct contact with the case 120 (sealing plate 124). Specifically, the in-hole insulating portion 136 is a cylindrical portion that extends along the height direction Z. The in-hole insulating portion 136 is disposed inside the terminal mounting hole 125 of the case 120. An outer periphery 136a of the in-hole insulating portion 136 is joined to the peripheral wall 125a of the terminal mounting hole 125. Furthermore, in this insulating material 130, the external insulating portion 132 and the internal insulating portion 134 are continuous via the internal insulating portion 136. In other words, the external insulating portion 132, the internal insulating portion 134, and the internal insulating portion 136 are integrally molded. The thickness of the internal insulating portion 136 is preferably 0.5 mm or more, more preferably 1.0 mm or more, and particularly preferably 2.0 mm or more. This prevents the internal insulating portion 136 from being damaged by friction or heat when inserting the buffer portions 12, 22. Meanwhile, the thickness of the internal insulating portion 136 is preferably 4.0 mm or less, more preferably 3.0 mm or less. This ensures that the terminal mounting hole 125 is sufficiently large, facilitating the insertion of the buffer portions 12, 22.

[0048] The insulating material 130 also has a protruding portion 134c that protrudes downward D from a portion of the internal insulating portion 134 (the inner portion in the depth direction Y). This makes it possible to regulate the up and down movement of the electrode assembly 110 within the case 120. As a result, it is possible to prevent contact between the electrode assembly 110 and the sealing plate 124 and damage to the connection tab 112. The thickness (protruding amount) of the protruding portion 134c is preferably 2.0 mm or more, and more preferably 3.0 mm or more. This makes it possible to more suitably regulate the up and down movement of the electrode assembly 110. Meanwhile, the thickness of the protruding portion 134c is preferably 5.0 mm or less, and more preferably 4.0 mm or less. This makes it possible to ensure sufficient storage space for the electrode assembly 110 within the case 120.

[0049] Although not shown, it is preferable that the surfaces of the metal members (sealing plate 124, current collector 140) that come into contact with the insulating material 130 be roughened. Specifically, the roughened portions are the peripheral portion 120a1 of the terminal mounting hole 125 on the outer surface 120a of the case 120, the peripheral portion 120b1 of the terminal mounting hole 125 on the inner surface 120b of the case 120, the peripheral wall 125a of the terminal mounting hole 125, and the surface of the current collector 140 (upper surface 142a of the joint 142) that is joined to the insulating material 130. This allows the resin material to penetrate into the irregularities on the surfaces of each metal member during insert molding. This creates an anchor effect, allowing the insulating material 130 and the metal member to be more firmly joined. Note that the roughening need only be applied to at least one location on each of the above-mentioned surfaces. Even in this case, the joining strength between the insulating material 130 and the metal member can be suitably improved. Furthermore, this surface roughening does not limit the technology disclosed herein. That is, even if the surface roughening is not performed, the insulating material 130 and the metal member can be sufficiently integrated by insert molding.

[0050] (1-4) Current collector 140 The current collector 140 is a conductive member electrically connected to the electrode assembly 110 inside the case 120. Specifically, the current collector 140 has an internal current collecting portion 146 extending along the height direction Z. This internal current collecting portion 146 is a plate-shaped portion connected to the connection tab 112 of the electrode assembly 110. The internal current collecting portion 146 is preferably made of the same type of metal material as the connection tab 112 to be connected. For example, as described above, the negative electrode tab is made of a negative electrode core that is copper foil. In this case, the internal current collecting portion 146 is preferably made of a copper-based material (copper, copper alloy, etc.). This allows the current collector 140 and the electrode assembly 110 to be firmly connected with low resistance.

[0051] Current collector 140 is disposed so as to cover terminal mounting hole 125 via insulating material 130, and is joined to insulating material 130. Current collector 140 has terminal portion 144 that is exposed to the outside of case 120 through terminal mounting hole 125 and can be electrically connected to bus bar 1. A current collector having such a configuration will be specifically described below.

[0052] First, the current collector 140 has a joint portion 142, which is a plate-like member joined to the insulating material 130. This joint portion 142 is joined to the lower surface 134b of the internal insulating portion 134 so as to close the terminal mounting hole 125 inside the case 120. More specifically, the joint portion 142 is formed by bending the upper end of the internal current collecting portion 146 so as to face the sealing plate 124. As a result, the joint portion 142 faces the inner surface 120b of the case 120 with the internal insulating portion 134 sandwiched therebetween. The upper surface 142a of the joint portion 142 is joined to the lower surface 134b of the internal insulating portion 134 by insert molding. As a result, the lower end of the terminal mounting hole 125 is closed by the joint portion 142.

[0053] The terminal portion 144 is exposed to the outside of the case 120 through the terminal mounting hole 125. This allows electrical connection between the bus bar 1 and the terminal portion 144. Specifically, in the structure shown in FIG. 5, the upper end of the terminal mounting hole 125 is open. As a result, a part of the current collector 140 (the terminal portion 144) is exposed to the outside of the case 120. This allows the buffer portions 12, 22 of the bus bar 1 to be inserted into the terminal mounting hole 125 from the outside of the case 120 (see FIG. 7). Then, a joining process such as laser welding is performed with the contact portions 14, 24 of the bus bar 1 in contact with the terminal portion 144. This forms joints W1, W2 that straddle the contact portions 14, 24 and the terminal portion 144, allowing electrical connection between the bus bar 1 and the current collector 140.

[0054] Furthermore, the terminal portion 144 of the electricity storage device 100 shown in FIG. 5 is located inward of the outer surface 120a of the case 120. In other words, as shown in FIG. 5, the upper surface 144a of the terminal portion 144 is located on the lower D side of the outline L1 along the outer surface 120a of the case 120. This prevents a portion of the current collector 140 from protruding outside the case 120. Additionally, in this electricity storage device 100, the terminal mounting hole 125 is sealed by the insulating material 130 and the current collector 140 (the joint portion 142 and the terminal portion 144). This prevents the electrolyte from leaking out and foreign matter from entering. As described above, the electricity storage device 100 configured as shown in FIG. 5 can form a conductive path to the outside of the case 120 and seal the inside of the case 120 without providing an external connection portion. That is, the configuration shown in FIG. 5 eliminates the need for conductive members protruding outside the case 120, thereby reducing the height of the electricity storage device 100. As a result, the loading efficiency of the electricity storage device 100 in the electrical appliance can be improved.

[0055] The terminal portion 144 shown in FIG. 5 is a convex terminal portion inserted into the terminal mounting hole 125 from the inside of the case 120. This raises the position of the upper surface 144a of the terminal portion 144 inside the terminal mounting hole 125, facilitating connection between the terminal portion 144 and the bus bar 1 (i.e., insertion of the buffer portions 12, 22 from above U). Furthermore, inserting the convex terminal portion 144 from the lower portion D of the terminal mounting hole 125 restricts movement of the current collector 140 in the horizontal direction (depth direction Y and width direction X). This also prevents peeling at the bonding interface between the joint portion 142 and the internal insulating portion 134. Note that as the position of the upper surface 144a of the terminal portion 144 inside the terminal mounting hole 125 increases, connection between the terminal portion 144 and the bus bar 1 tends to become easier. From this perspective, distance H3 from outer surface 120a of case 120 to upper surface 144a of terminal portion 144 is preferably 2.0 mm or less, more preferably 1.0 mm or less, and even more preferably 0.5 mm or less. Upper surface 144a of terminal portion 144 may be at substantially the same height as outer surface 120a of case 120 (i.e., distance H3 is 0 mm). In this case, connection between terminal portion 144 and bus bar 1 becomes even easier.

[0056] As described above, the current collector 140 shown in FIG. 5 includes a joint 142, which is a plate-like member joined to the insulating material 130. In this case, the convex terminal 144 shown in FIG. 5 is a columnar member joined to the upper surface 142a of the joint 142. This ensures a sufficient thickness for the terminal 144. As a result, an appropriate welding depth can be ensured when forming the joints W1 and W2. Furthermore, when this configuration is adopted, the material of the terminal 144 can be freely selected without being affected by the materials of the other parts (the joint 142, the internal current collecting portion 146).

[0057] For example, as shown in FIG. 5 , a clad material including a first layer 147 and a second layer 145 can be used as the terminal portion 144. The first layer 147 of the terminal portion 144 is joined to the upper surface 142a of the joint portion 142 and is made of the same metal as the joint portion 142. This allows for a strong bond between the terminal portion 144 and the joint portion 142. Meanwhile, the second layer 145 is exposed to the outside of the case 120 through the terminal mounting hole 125 and is made of a different metal from the first layer 147. This allows for a metal that can be easily connected to the bus bar 1 to be disposed on the upper surface 144a of the terminal portion 144. For example, in the negative electrode side current collector 140, a copper-based material is used for the internal current collecting portion 146 and the joint portion 142 in consideration of connectivity with the negative electrode tab. On the other hand, in the positive electrode side current collector, an aluminum-based material is used in consideration of connectivity with the positive electrode tab. In this case, the busbar 1 connecting the positive electrode current collector and the negative electrode current collector is often made of an aluminum-based material in consideration of connectivity with the positive electrode terminal portion 144. In this case, it is preferable that the first layer 147 of the terminal portion 144 of the negative electrode current collector 140 is made of copper and the second layer 145 is made of aluminum. This makes it possible to form a copper-copper bonding interface between the terminal portion 144 and the joint portion 142, and also to form an aluminum-copper bonding interface between the terminal portion 144 and the busbar 1. As a result, a strong, low-resistance conductive path can be formed from the electrode body 110 to the busbar 1.

[0058] An example of the power storage device 100 used in the power storage unit 500 has been described above. As described above, the power storage device 100 configured as shown in FIG. 5 does not have a conductive member (terminal portion 144) protruding outside the case 120, and therefore has a reduced height. This improves the loading efficiency of the power storage device 100 in an electrical appliance. Note that in the power storage unit 500 according to this embodiment, it is not necessary for all of the multiple power storage devices 100 to have the above-described configuration. For example, when mounting the power storage unit in an electrical appliance, only some of the multiple power storage devices may interfere with other components, making it necessary to reduce the overall height of the power storage unit. In such cases, it is advisable to adopt the above-described configuration only in the power storage device that interferes with other components. This improves the loading efficiency of the power storage device.

[0059] (2) Restraining member Next, the energy storage unit 500 shown in FIG. 3 includes a restraining member that restrains a plurality of energy storage devices 100. Specifically, a pair of end plates 220 is arranged on both outer sides of the energy storage units 500 in the arrangement direction (width direction X). The pair of end plates 220 is bridged by a restraining beam member 230. This allows a restraining pressure to be applied to each of the energy storage devices 100 in the arrangement direction. Furthermore, a resin buffer member 250 is arranged between each of the arranged energy storage devices 100. This allows the restraining pressure applied to the energy storage devices 100 to be uniform.

[0060] (3) Busbar The energy storage unit 500 according to this embodiment uses the bus bar 1 configured as described above. This bus bar 1 electrically connects a plurality of energy storage devices 100. Specifically, in the energy storage unit 500 shown in FIG. 3, the plurality of energy storage devices 100 are arranged so that the positive electrode terminal mounting hole 125P of one energy storage device 100 and the negative electrode terminal mounting hole 125N of the other energy storage device 100 are adjacent to each other. The bus bar 1 is connected to the terminal portions 144 present inside each of a pair of adjacent terminal mounting holes 125.

[0061] Here, the bus bar 1 in this embodiment has stepped buffer portions 12, 22 that protrude downward D (see FIGS. 1 and 2). As described above, these buffer portions 12, 22 are inserted into the terminal mounting holes 125 from the outside of the case 120. Then, the contact portions 14, 24, which are the bottom surfaces of the buffer portions 12, 22, are joined to the terminal portion 144. This allows the terminal portion 144 to be easily connected to the bus bar 1 even when the terminal portion 144 is located inward (downward D) from the outer surface 120a of the case 120.

[0062] When inserting the buffer portions 12, 22 into the terminal mounting hole 125, it is preferable to set the inner dimensions of the terminal mounting hole 125 and the outer dimensions of the buffer portions 12, 22 to be approximately equal. This allows the outer peripheral walls of the protrusions 13, 23 to come into contact with the inner peripheral wall of the in-hole insulating portion 136, thereby restricting movement (vibration, etc.) of the contact portions 14, 24 in the planar direction. As a result, it is possible to more effectively prevent stress S from being applied in the planar direction to the joints W1, W2 between the contact portions 14, 24 and the terminal portion 144.

[0063] <Other embodiments> One embodiment of the technology disclosed herein has been described above. However, the technology disclosed herein is not limited to the above-described embodiment. Other embodiments of the technology disclosed herein will be described below.

[0064] 1. Buffer section with grooves As shown in FIG. 2, the buffer sections 12, 22 in the first embodiment include contact sections 14, 24 with flat upper surfaces. However, as shown in FIG. 8, grooves 14a, 24a may be formed on the upper surfaces of the contact sections 14, 24. These grooves 14a, 24a are annular in plan view. The portions where the grooves 14a, 24a are formed are thinner than other regions, making it easy to form the joints W1, W2 that penetrate the contact sections 14, 24. Furthermore, forming the grooves 14a, 24a makes it easy to form the joints W1, W2 even if other portions are thicker. This also contributes to improving the overall strength of the busbar 1.

[0065] 2. Planar shape of the buffer section As shown in FIG. 1 , in the first embodiment, the buffer portions 12, 22 are provided with a substantially circular planar shape. However, the planar shape of the buffer portions is not particularly limited, and various shapes can be adopted. For example, as shown in FIG. 9 , the busbar 1 may include the buffer portions 12, 22 with a substantially rectangular planar shape. Even in this case, stresses along both the width direction X and the depth direction Y can be appropriately alleviated. Furthermore, as shown in FIG. 10 , the busbar 1 may include the band-shaped buffer portions 12, 22 that extend across the entire depth direction Y in a plan view. Even in this case, stresses along the width direction X can be alleviated. As described above, the stress S due to the variation in the gap G between the first bonding region 10 and the second bonding region 20 is mainly stress along the width direction X. Therefore, the band-shaped buffer portions 12, 22 shown in FIG. 10 can be sufficiently alleviated.

[0066] 3. Buffer areas other than step shapes In addition, in all of the above-described embodiments, the buffer sections 12, 22 are formed as stepped buffer sections including the protrusions 13, 23 and the contact sections 14, 24 (see FIGS. 1, 9, and 10). However, the buffer sections are not limited to stepped buffer sections as long as they can absorb stress caused by variations in the distance between the first and second bonding regions. For example, the busbar 1 shown in FIG. 11 has a pair of openings 17, 27 extending in the depth direction Y. In this busbar 1, bonding sections W1, W2 are formed between the pair of openings 17, 27. In this busbar 1, when stress S occurs along the width direction X, the busbar 1 deforms so that the openings 17, 27 are crushed. This allows the busbar 1 to adequately absorb the stress S along the width direction X. In other words, the buffer sections in the busbars disclosed herein are not limited to the stepped buffer sections described above and may be formed as openings 17, 27 as shown in FIG. 11.

[0067] 4. Number of bonding areas with buffers As shown in FIGS. 1 and 2, the busbar 1 according to the first embodiment has buffering portions 12, 22 in both the first and second joining regions 10, 20. However, the buffering portions may be formed in only one of the first and second joining regions. Even in this case, it is possible to prevent a large stress from being applied to the joining region where the buffering portion is formed. In particular, as shown in FIG. 3, the terminal portions 144 of the power storage devices 100 arranged at both ends in the arrangement direction (width direction X) are not connected to the adjacent power storage device 100. These open terminal portions 144 are connected to an external device (such as a motor) as a total positive terminal (or total negative terminal). In the busbar used for this connection, it is sufficient to form a buffering portion only in the joining region that is joined to the total positive terminal (or total negative terminal). This prevents stress from being applied to the joining region between the terminal portion and the busbar.

[0068] 5.Structure of the cross-linked region Furthermore, the busbar 1 according to the first embodiment has a fluctuation absorbing portion 32 in the bridging region 30 (see FIGS. 1 and 2). However, the busbar disclosed herein does not necessarily have to have a fluctuation absorbing portion in the bridging region. As described above, providing buffer portions 12, 22 in at least one of the first and second joint regions 10, 20 can reduce stress on the joints W1, W2 between the terminal portion 144 and the busbar 1.

[0069] 6. Terminal structure of electricity storage device As described above, the energy storage unit disclosed herein is not limited to the configuration in which the energy storage device 100 shown in FIGS. 4 and 5 is used. In particular, even if the structure shown in FIGS. 4 and 5 is not adopted, the loading efficiency of the energy storage device can be improved by arranging the terminal portion inward from the case. For example, the terminal portion 144 of the energy storage device 100 having the structure shown in FIG. 5 is a columnar clad material including a first layer 147 and a second layer 145. However, the terminal portion 144 is not limited to a columnar clad material. For example, the terminal portion 144 may be a columnar member made of a single metal material (see FIG. 12). Even when such a configuration is adopted, the loading efficiency of the energy storage device 100 can be improved by arranging the upper surface 144a of the terminal portion 144 inward (downward D) from the outer surface 120a of the case 120.

[0070] Terminal portion 144 made of a single metal material can be particularly suitably used when joint portion 142 and bus bar 1 are made of the same material. For example, in the positive electrode side current collector 140, an aluminum-based material is used for internal current collecting portion 146 and joint portion 142 in consideration of connectivity with the positive electrode tab (aluminum foil). On the other hand, as described above, an aluminum-based material is also used for bus bar 1 when constructing power storage unit 500. In such a configuration, even if a clad material is not used for terminal portion 144, the conductive path from electrode body 110 to bus bar 1 can be constructed of an aluminum-based material, and therefore a strong, low-resistance conductive path can be formed.

[0071] In the first embodiment, the pillar-shaped terminal portion 144 is joined to the upper surface 142a of the joint portion 142 (see FIG. 5). However, the convex terminal portion 144 is not limited to this configuration. For example, if the joint portion 142 of the current collector 140 is a plate-shaped member, the convex terminal portion 144 can be formed by bending the joint portion 142 (see FIG. 13). This convex terminal portion 144 can be formed by pressing the plate-shaped joint portion 142. Even when the terminal portion 144 having such a configuration is inserted into the terminal mounting hole 125, the connection between the terminal portion 144 and the bus bar 1 is facilitated and movement of the current collector 140 in the horizontal direction can be restricted. Furthermore, according to the present embodiment, the number of parts of the current collector 140 can be reduced, which contributes to reducing material costs.

[0072] Furthermore, in the first embodiment, the convex terminal portion 144 is inserted into the terminal mounting hole 125. However, the current collector of the electricity storage device does not have to have a convex terminal portion. For example, as shown in FIG. 14 , the joint portion 142 and the terminal portion 144 may form a continuous flat surface. Even when such a configuration is adopted, the terminal mounting hole 125 can be sealed with the insulating material 130 and the terminal portion 144. Even when such a configuration is adopted, the terminal portion 144 is exposed to the outside of the case 120 through the terminal mounting hole 125, so that the bus bar 1 and the current collector 140 can be electrically connected. Also in this case, the terminal portion 144 is disposed inward (downward D) from the outer surface 120a of the case 120, so that the loading efficiency of the electricity storage device in the electrical product can be improved.

[0073] The energy storage unit 500 according to the first embodiment uses an energy storage device 100 in which a terminal portion 144 is disposed inside a case 120. In the first embodiment, the buffer portions 12, 22 of the bus bar 1 are inserted into the terminal mounting holes 125. However, the structure of the bus bar disclosed herein is not affected by the structure of the terminal portion of the energy storage device. In other words, the structure of the energy storage device 100 does not limit the technology disclosed herein. For example, as shown in FIG. 15 , even when an energy storage device 100 having a terminal portion 144 protruding outside the case 120 is used, the buffer portions 12, 22 of the bus bar 1 can be appropriately joined to the terminal portion 144. Even when such a configuration is adopted, the buffer portions 12, 22 of the bus bar 1 can absorb stress along the width direction X, thereby reducing stress on the joint portions W1, W2.

[0074] In the first embodiment, the outer walls of the protrusions 13, 23 of the busbar 1 contact the inner walls of the in-hole insulating portions 136 of the insulating material 130 (see FIG. 7 ). This restricts the movement of the contact portions 14, 24 in the planar direction, thereby more effectively suppressing stress from being applied to the joint portions W1, W2. However, the means for restricting the movement of the contact portions 14, 24 in the planar direction is not limited to the above-described structure. For example, as shown in FIG. 16 , when using an energy storage device 100 having a terminal portion 144 that protrudes outside the case 120, a movement restricting portion 144a that protrudes upward U may be provided on the outer periphery of the terminal portion 144. The busbar 1 and the terminal portion 144 are then joined together so that the outer walls of the protrusions 13, 23 of the busbar 1 contact the movement restricting portion 144a. This allows the movement of the contact portions 14, 24 in the planar direction to be appropriately restricted. That is, in order to restrict the movement of contact portions 14, 24 in the planar direction, the outer walls of protrusions 13, 23 of busbar 1 may be brought into contact with parts of electricity storage device 500.

[0075] The technology disclosed herein has been described in detail above. However, these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and alterations of the specific examples exemplified above. In other words, the technology disclosed herein encompasses the aspects described in items 1 to 9 below.

[0076] [Item 1] a first bonding region bonded to a terminal portion of the first electricity storage device; a second bonding region bonded to a terminal portion of a second power storage device different from the first power storage device; a bridging region connecting the first bonding region and the second bonding region; and The busbar has a buffer portion provided in at least one of the first and second joint regions, the buffer portion absorbing stress caused by variations in the distance between the first and second joint regions.

[0077] [Item 2] At least one of the first bonding region and the second bonding region has a plate-shaped bonding base portion, Item 2. The busbar according to item 1, wherein the buffer portion is configured as a step protruding from the joint base portion.

[0078] [Item 3] The buffer section is a protrusion protruding from the joint base; a contact portion provided at a tip of the protrusion and contacting the terminal portion; 3. The busbar according to item 2,

[0079] [Item 4] Item 4. The bus bar according to item 3, wherein the thickness of the protrusion is smaller than the thickness of the contact portion.

[0080] [Item 5] 5. The bus bar according to item 4, wherein the thickness of the protruding portion is 50% to 90% of the thickness of the contact portion, which is 100%.

[0081] [Item 6] 6. The bus bar according to any one of items 1 to 5, wherein the buffer portion is provided in both the first joint region and the second joint region.

[0082] [Item 7] 7. The busbar according to claim 1, wherein the bridging region has a fluctuation absorbing portion that absorbs fluctuations in the gap between the first joint region and the second joint region.

[0083] [Item 8] the bridging region has a plate-shaped base portion, 8. The busbar according to item 7, wherein the fluctuation absorbing portion is configured by a step.

[0084] [Item 9] A plurality of power storage devices; a plurality of bus bars that electrically connect the terminal portions of the plurality of power storage devices; Equipped with An electricity storage unit, wherein at least one of the plurality of bus bars is the bus bar according to any one of items 1 to 8.

[0085] [Item 10] At least one of the plurality of power storage devices is An electrode body; a case that houses the electrode body and has a terminal mounting hole; an insulating material that covers a peripheral wall and a peripheral edge portion of the terminal mounting hole continuously in a circumferential direction and is joined to the peripheral edge portion of the terminal mounting hole; a current collector electrically connected to the electrode body inside the case; Equipped with The current collector is The insulating material is disposed so as to close the terminal mounting hole, bonded to the insulating material; a terminal portion exposed to the outside of the case through the terminal mounting hole and electrically connectable to the bus bar; the terminal portion is located inward from an outer surface of the case, and the terminal mounting hole is sealed by the insulating material and the current collector; 10. The energy storage unit according to item 9, wherein the buffer portion of the bus bar is inserted into the terminal mounting hole from the outside of the case and connected to the terminal portion. [Explanation of symbols]

[0086] 1 busbar 10 1st joint area 11 First base part 12 Buffer section 13 Protrusion 14 Contact area 17 Opening 20 Second joint area 21 Second base part 22 Buffer section 23 Protrusion 24 Contact area 30 Crosslinked area 31 Bridge base part 32 Fluctuation absorber 33 Protrusion 34 Connecting part 100 Energy storage device 110 Electrode body 120 cases 122 Case body 124 Sealing plate 125 Terminal mounting hole 130 Insulation 140 Current collector 142 Joint 144 Terminal section 500 Energy Storage Unit

Claims

1. A plurality of power storage devices; a plurality of bus bars that electrically connect the terminal portions of the plurality of power storage devices; Equipped with At least one of the plurality of bus bars a first bonding region bonded to a terminal portion of the first electricity storage device; a second bonding region bonded to a terminal portion of a second power storage device different from the first power storage device; a bridging region connecting the first bonding region and the second bonding region; and a buffer portion is provided in at least one of the first bonding region and the second bonding region to absorb stress caused by a change in the distance between the first bonding region and the second bonding region; At least one of the plurality of power storage devices is An electrode body; a case that houses the electrode body and has a terminal mounting hole; an insulating material that covers a peripheral wall and a peripheral edge portion of the terminal mounting hole continuously in a circumferential direction and is joined to the peripheral edge portion of the terminal mounting hole; a current collector electrically connected to the electrode body inside the case; Equipped with The current collector is The insulating material is disposed so as to close the terminal mounting hole, bonded to the insulating material; a terminal portion exposed to the outside of the case through the terminal mounting hole and electrically connectable to the bus bar; the terminal portion is located inward from an outer surface of the case, and the terminal mounting hole is sealed by the insulating material and the current collector; The buffer portion of the bus bar is inserted into the terminal mounting hole from the outside of the case and joined to the terminal portion.

2. At least one of the first bonding region and the second bonding region has a plate-shaped bonding base portion, The energy storage unit according to claim 1 , wherein the buffer portion is formed by a step that protrudes from the joint base portion.

3. The buffer section is a protrusion protruding from the joint base; a contact portion provided at a tip of the protrusion and contacting the terminal portion; The power storage unit according to claim 2 ,

4. The power storage unit according to claim 3 , wherein the thickness of the protrusion is smaller than the thickness of the contact portion.

5. 5. The electricity storage unit according to claim 4, wherein the thickness of the protruding portion is 50% to 90% of the thickness of the contact portion, which is 100%.

6. The power storage unit according to claim 1 , wherein the buffer portion is provided in both the first bonding region and the second bonding region.

7. The electricity storage unit according to claim 1 , wherein the bridging region has a fluctuation absorbing portion that absorbs fluctuations in the gap between the first bonding region and the second bonding region.

8. The bridging region has a plate-shaped bridging base portion, The electricity storage unit according to claim 7 , wherein the fluctuation absorbing portion is configured as a step protruding from the bridge base portion.

Images