Battery stack

Abstract

A battery stack is provided. The battery stack includes a plurality of batteries stacked and a bus bar electrically connecting the plurality of batteries. The bus bar includes a main body extending in a stacking direction (X) of the batteries and a plurality of connection portions protruding from the main body in a direction intersecting the stacking direction and electrically connected to terminals of the batteries. The plurality of batteries are grouped into a plurality of battery units each including at least two of the batteries, the batteries in each battery unit are connected in parallel to each other by the bus bar, and the battery units are connected in series to each other by the bus bar.

Description

[0001] This application is a divisional application of the invention patent application filed on December 7, 2018, with application number 201880053596.8 and invention title "Busbar and Battery Laminate". Technical Field

[0002] This invention relates to busbars and battery stacks. Background Technology

[0003] For example, batteries used as power sources requiring high output voltage, such as those for vehicles, are known to be battery stacks consisting of multiple batteries electrically connected together. Conventionally, in such battery stacks, the output terminals of adjacent batteries are connected to each other via busbars. For example, Patent Document 1 discloses a battery stack having a structure in which multiple batteries are connected in parallel via busbars to form multiple battery cells, and the battery cells are connected in series with each other via the same busbars. By adopting such a structure, compared to the case where all batteries in a battery stack connected in series via busbars are connected in parallel, the number of components such as voltage detection lines can be reduced, and the cost of the battery device can be reduced.

[0004] Prior art literature

[0005] Patent documents

[0006] Patent Document 1: Japanese Patent Application Publication No. 2016-27578 Summary of the Invention

[0007] The inventors conducted in-depth research on the structure of parallel and series connections of batteries integrated within a battery stack, and as a result recognized the following issues: The increased current flowing through the busbars due to the parallel connection of the batteries leads to increased heat generation in the busbars. In particular, in recent years, there has been a trend towards even larger current flows through the busbars to meet demands for high output and fast charging. Therefore, the heat generation in the busbars also tends to increase. If the heat generation in the busbars increases, heat is transferred from the busbars to the batteries, causing the battery temperature to rise and potentially reducing the battery's power generation performance.

[0008] The present invention was made in view of the following situation, and its object is to provide a technique for reducing the impact of heat generated by the busbar on the battery.

[0009] One aspect of the present invention is a battery stack. The battery stack comprises a plurality of stacked batteries and a busbar electrically connecting the plurality of batteries. The busbar has a main body extending in the stacking direction of the batteries and a plurality of connecting portions protruding from the main body in a direction intersecting the stacking direction and electrically connected to the terminals of each battery. The plurality of batteries are grouped into a plurality of battery cells consisting of at least two batteries, in which the batteries are connected in parallel to each other via the busbar, and the battery cells are connected in series to each other via the busbar.

[0010] Another aspect of the present invention is a busbar. This busbar is a busbar that electrically connects multiple stacked batteries, and has a main body extending in the stacking direction of the batteries and multiple connecting portions protruding from the main body in a direction intersecting the stacking direction and electrically connected to the terminals of each battery.

[0011] Furthermore, any combination of the above structural elements, as well as variations in the presentation of the invention across methods, apparatuses, systems, etc., are also valid ways of presenting the invention.

[0012] According to the present invention, the impact of heat generated by the busbar on the battery can be reduced. Attached Figure Description

[0013] Figure 1 This is a perspective view showing the schematic structure of the battery stack according to Embodiment 1.

[0014] Figure 2 It is a magnified three-dimensional view of the vicinity of the busbar in the battery stack.

[0015] Figure 3 This is a perspective view showing an enlarged view of the vicinity of the busbar in the battery stack according to Embodiment 2.

[0016] Figure 4 This is a perspective view showing the schematic structure of the busbars in the battery stack involved in the modified example.

[0017] Figure 5 This is a plan view showing the vicinity of the busbar in the battery stack according to Embodiment 3.

[0018] Figure 6 This is a magnified plan view of the vicinity of the busbar in the battery stack according to Embodiment 4.

[0019] Figure 7 This is a perspective view showing an enlarged view of the vicinity of the busbar in the battery stack according to Embodiment 5.

[0020] Symbol Explanation

[0021] 1 Battery stack

[0022] 2. Busbar

[0023] 4 batteries

[0024] 4a Battery 1

[0025] 4b Second Battery

[0026] 16 Main body

[0027] 18 Connecting parts

[0028] 18a First connecting part

[0029] 18b Second connecting part

[0030] 20 battery cells

[0031] 20a First Battery Cell

[0032] 20b Second Battery Unit

[0033] 28 Displacement Absorption Section Detailed Implementation

[0034] The present invention will now be described with reference to the accompanying drawings, based on preferred embodiments. These embodiments are not intended to limit the invention but are illustrative; all features and combinations thereof described in the embodiments may not necessarily be the essential content of the invention. For the same or equivalent structural elements, components, and processes shown in the various drawings, repeated descriptions are appropriately omitted. Furthermore, the scales and shapes of the parts shown in the figures are appropriately set for ease of explanation and are not to be interpreted as limiting unless specifically mentioned. Moreover, even for the same components, there may be slight differences in scales and other parameters between the various drawings. Furthermore, the use of terms such as "first," "second," etc., in this specification or claims does not indicate any order or importance unless specifically mentioned, but is used to distinguish one structure from others.

[0035] (Implementation Method 1)

[0036] Figure 1 This is a perspective view showing the schematic structure of the battery stack according to Embodiment 1. The battery stack 1 (1A) includes a plurality of busbars 2 and a plurality of batteries 4 electrically connected to each other through the busbars 2.

[0037] Each battery 4 is, for example, a rechargeable secondary battery such as a lithium-ion battery, a nickel-metal hydride battery, or a nickel-cadmium battery. Battery 4 is a so-called square battery, having a flat, rectangular outer casing. A roughly rectangular opening (not shown) is provided on one side of the outer casing, through which electrodes, electrolyte, etc., are stored. A sealing plate 6 is provided at the opening of the outer casing to seal it. A positive output terminal 8 is provided at one end of the sealing plate 6 along its length, and a negative output terminal 8 is provided at the other end. Hereinafter, the positive output terminal 8 will be appropriately referred to as the positive terminal 8a, and the negative output terminal 8 as the negative terminal 8b. Furthermore, when it is not necessary to distinguish the polarity of the output terminals 8, the positive terminal 8a and the negative terminal 8b will be collectively referred to as output terminals 8.

[0038] Output terminal 8 protrudes from the opening of sealing plate 6. A gasket, serving as a sealing member, is provided between the periphery of output terminal 8 and the opening of sealing plate 6. The gasket airtightly seals the boundary between sealing plate 6 and output terminal 8. Furthermore, it prevents short circuits between sealing plate 6 and output terminal 8. The outer can, sealing plate 6, and output terminal 8 are conductive, for example, made of metal. The gasket is an insulator, for example, made of resin. Additionally, a safety valve (not shown) is provided on sealing plate 6 between a pair of output terminals 8. The safety valve is configured to open when the internal pressure of the outer can rises above a predetermined value, releasing internal gas.

[0039] In this embodiment, the side where the sealing plate 6 is provided is designated as the upper surface of the battery 4, and the opposite side is designated as the bottom surface of the battery 4. Furthermore, the battery 4 has two main surfaces connecting the upper surface and the bottom surface. These main surfaces are the largest of the six surfaces of the battery 4. The remaining two surfaces besides the upper surface, bottom surface, and two main surfaces are designated as the side surfaces of the battery 4. Additionally, the upper surface of the battery 4 is designated as the upper surface of the battery stack 1, the bottom surface of the battery 4 is designated as the bottom surface of the battery stack 1, and the side surfaces of the battery 4 are designated as the side surfaces of the battery stack 1. Furthermore, for convenience, the upper surface of the battery stack 1 is positioned vertically upwards, and the bottom surface of the battery stack 1 is positioned vertically downwards.

[0040] Multiple batteries 4 are stacked at predetermined intervals, such that the main surfaces of adjacent batteries 4 face each other. Furthermore, "stacked" refers to arranging multiple components in any one direction. Therefore, the stacking of batteries 4 also includes cases where multiple batteries 4 are arranged horizontally. In addition, each battery 4 is configured such that its output terminal 8 faces the same direction. Here, for convenience, the output terminal 8 faces the vertical direction Z (in...). Figure 1 Above (in the direction indicated by the middle arrow Z).

[0041] Busbar 2 is a long, strip-shaped metal component that electrically connects multiple stacked batteries 4. Examples of metals constituting busbar 2 include copper and aluminum. Busbar 2 is joined to the output terminals 8 of each battery 4, for example, by welding. The construction of busbar 2 and the connection of the batteries 4 using busbar 2 will be described in detail later.

[0042] The battery stack 1 has multiple separators (not shown). These separators, also referred to as insulating spacers, are made of, for example, an insulating resin. Examples of resins constituting the separators include thermoplastic resins such as polypropylene (PP), polybutylene terephthalate (PBT), polycarbonate (PC), and Noryl resin (modified PPE). The separators are disposed between each battery 4 and between the battery 4 and the end plate 10 (described later). Thus, the outer casings of adjacent batteries 4 are insulated from each other. Furthermore, the outer casings of the battery 4 are insulated from the end plate 10.

[0043] Furthermore, the battery stack 1 has a pair of end plates 10. The end plates 10 are, for example, made of metal plates. Multiple stacked batteries 4 and multiple spacers are held by the pair of end plates 10. The pair of end plates 10 are aligned along the stacking direction X of the batteries 4. Figure 1 Arranged in the direction indicated by the middle arrow X, it is adjacent to the outermost battery 4 through the separator. In addition, the outermost busbar 2 in the stacking direction X also functions as an external connection terminal.

[0044] Furthermore, the battery stack 1 has a pair of constraint members 12. The stacked batteries 4, separators, and end plates 10 are constrained by the pair of constraint members 12. The pair of constraint members 12 are also referred to as binding strips. The pair of constraint members 12 are aligned along a horizontal direction Y (orthogonal to the stacking direction X of the plurality of batteries 4) Figure 1 (As indicated by the arrow Y) Arranged. The horizontal direction Y is the direction in which the output terminals 8 in each battery 4 are arranged. Each constraint member 12 has a rectangular planar portion 12a parallel to the side of the battery 4, and an eave portion 12b protruding from the ends of each side of the planar portion 12a toward the battery 4. The constraint member 12 can be formed, for example, by bending each side of a rectangular metal plate.

[0045] Two opposing eaves 12b and a pair of end plates 10 in the stacking direction X of the batteries 4 are fixed by screws or the like. Thus, multiple batteries 4 and multiple spacers are fastened by the pair of end plates 10 and the pair of constraint members 12. The multiple batteries 4 are tightened by the constraint members 12 in the stacking direction X, thereby achieving positioning in the stacking direction X. Furthermore, regarding the multiple batteries 4, the bottom surface abuts against the lower eaves 12b of the constraint member 12 through the spacers, and the upper surface abuts against the upper eaves 12b of the constraint member 12 through the spacers, thereby achieving vertical positioning. In this state, the busbar 2 is electrically connected to the output terminals 8 of each battery 4, resulting in the battery stack 1.

[0046] Next, the structure of the busbar 2 and the electrical connection of the battery 4 using the busbar 2 will be described in detail. Figure 2 This is a magnified perspective view of the vicinity of the busbar in the battery stack. The busbar 2 has a main body 16 and a plurality of connecting portions 18. The main body 16 is a strip-shaped portion extending in the stacking direction X of the batteries 4. The plurality of connecting portions 18 are portions electrically connected to the output terminals 8 of each battery 4. Each connecting portion 18 is arranged at predetermined intervals along the extending direction (stacking direction X) of the main body 16 and protrudes from the main body 16 in a direction intersecting the stacking direction X (horizontal direction Y). Therefore, the busbar 2 is comb-shaped.

[0047] In this embodiment, the busbar 2 is configured such that the main body 16 is located on the central side of the battery 4 in the horizontal Y direction, which is further away from the output terminal 8, and the connecting portion 18 protrudes outward toward the outside of the battery 4. That is, the main body 16 is separate from the output terminal 8 of each battery 4. Alternatively, the main body 16 may also be configured in the horizontal Y direction, which is further away from the outside of the battery 4 than the output terminal 8.

[0048] Multiple batteries 4 are grouped into multiple battery cells 20, each consisting of at least two batteries 4. Furthermore, within each battery cell 20, the batteries 4 are connected in parallel to each other via busbars 2. Additionally, the battery cells 20 are connected in series to each other via busbars 2. Figure 2 In the example shown, the first battery 4a and the second battery 4b are stacked with their output terminals 8 of the same polarity adjacent to each other to form the first battery cell 20a. Similarly, the first battery 4a and the second battery 4b are stacked with their output terminals 8 of the same polarity adjacent to each other to form the second battery cell 20b.

[0049] The first battery unit 20a and the second battery unit 20b are stacked such that the positive terminal 8a of the first battery unit 20a is adjacent to the negative terminal 8b of the second battery unit 20b. The second battery 4b in each battery unit 20 is positioned closer to the other battery unit 20 than the first battery 4a. Furthermore, the connecting portion 18 of the busbar 2 engages with each output terminal 8. Thus, the first battery 4a and the second battery 4b in each battery unit 20 are connected in parallel, and the first battery unit 20a and the second battery unit 20b are connected in series.

[0050] The plurality of connecting portions 18 include a first connecting portion 18a and a second connecting portion 18b. Considering the first battery cell 20a, the first connecting portion 18a is connected to the first battery 4a, which is farther from the second battery cell 20b. The second connecting portion 18b is connected to the second battery 4b, which is closer to the second battery cell 20b. When the contact point between the first connecting portion 18a and the first battery 4a is designated as the first contact point A1, the contact point between the second connecting portion 18b and the second battery 4b is designated as the second contact point A2, and the contact point between the second connecting portion 18b and the main body portion 16 is designated as the third contact point B, the first connecting portion 18a and the second connecting portion 18b have a shape such that the difference between the resistance from the first contact point A1 to the third contact point B and the resistance from the second contact point A2 to the third contact point B is smaller than when the first connecting portion 18a and the second connecting portion 18b have the same shape. The connection structure between battery 4 and busbar 2 in the second battery unit 20b is the same.

[0051] In this embodiment, the cross-sectional areas of the first connecting portion 18a and the second connecting portion 18b are different. Specifically, the width of the second connecting portion 18b is thinner than that of the first connecting portion 18a (the dimension in the stacking direction X). The thicknesses of the first connecting portion 18a and the second connecting portion 18b (the dimension in the vertical direction Z) are the same. Therefore, the cross-sectional area C2 of the second connecting portion 18b in the stacking direction X is smaller than the cross-sectional area C1 of the first connecting portion 18a in the stacking direction X.

[0052] Furthermore, the cross-sectional areas C1 and C2 of each connecting portion 18 in the stacking direction X are smaller than the cross-sectional area C3 of the main body portion 16 in the direction intersecting the stacking direction X (horizontal direction Y). Additionally, the busbar 2 has a shape in which the resistance in the region where the battery cells 20 are connected in series (hereinafter appropriately referred to as the series connection region) is smaller than the resistance in the region where the batteries 4 are connected in parallel (hereinafter appropriately referred to as the parallel connection region).

[0053] The series connection region is the area between the two second connection portions 18b in the main body 16. More specifically, it is the area between one second connection portion 18b and the third contact B of the main body 16, and the area between the other second connection portion 18b and the third contact B of the main body 16. Furthermore, the parallel connection region includes the first connection portion 18a and the second connection portion 18b corresponding to each battery cell 20, and the portion of the main body 16 excluding the area between the third contact B. The main body 16 has a uniform width and thickness throughout the entire region. Furthermore, the cross-sectional area C1 of the first connection portion 18a and the cross-sectional area C2 of the second connection portion 18b are smaller than the cross-sectional area C3 of the main body 16. Moreover, each connection portion 18 is included in the parallel connection region but not in the series connection region. Therefore, the resistance in the series connection region of the busbar 2 is less than the resistance in the parallel connection region.

[0054] As explained above, the battery stack 1 according to this embodiment includes a plurality of batteries 4 and a busbar 2 electrically connecting the plurality of batteries 4. The busbar 2 has a main body portion 16 extending in the stacking direction X of the batteries 4 and a plurality of connecting portions 18 electrically connected to the output terminals 8 of each battery 4. Each connecting portion 18 protrudes from the main body portion 16 in a direction intersecting the stacking direction X and in the XY plane direction. Furthermore, the front end of each connecting portion 18 is connected to the output terminal 8. As a result, the main body portion 16 can be positioned offset from directly above the output terminal 8.

[0055] Furthermore, the multiple batteries 4 are grouped into multiple battery cells 20, each consisting of at least two batteries 4. Moreover, within each battery cell 20, the batteries 4 are connected in parallel to each other via busbars 2, and the battery cells 20 are connected in series to each other via busbars 2. Therefore, a combined current flows through a portion of the main body 16 through the parallel-connected batteries 4. The heat generated J by the busbar 2 is a value obtained by multiplying the resistance R of the busbar 2 by the square of the current I flowing through the busbar 2 (J = I). 2 R). The heat generated relative to the area through which the output current of each of the battery cells 4 in each connection portion 18 and the main body portion 16 flows (I) 2 R), the heat generated in the area through which the synthetic current flows in the main body 16 is the square of the number of batteries 4 connected in parallel. In this embodiment, there are two batteries 4 connected in parallel, therefore the heat generated in the area through which the synthetic current flows in the main body 16 is 4 × I. 2 R. Therefore, the main body 16 becomes significantly hot, which may affect each battery 4.

[0056] In this regard, the busbar 2 has a main body portion 16 parallel to the stacking direction X of the battery 4 and a connecting portion 18 parallel to the horizontal direction Y. Furthermore, by connecting the connecting portion 18 to the output terminal 8, the main body portion 16, which generates significant heat, is moved away from the output terminal 8. This reduces the impact of heat generated by the busbar 2 on the battery 4. As a result, it is possible to suppress the temperature rise of the battery 4 due to the heat from the busbar 2, thus preventing a decrease in power generation performance. Moreover, since the temperature rise of the battery 4 can be suppressed, a larger current can flow through the busbar 2.

[0057] In particular, the gasket disposed between the output terminal 8 and the sealing plate 6 has weak heat resistance, so it is important to suppress the temperature rise of the output terminal 8 caused by the heat of the busbar 2. Therefore, the busbar 2 according to this embodiment can suppress the temperature rise of the output terminal 8 and suppress the melting of the gasket. Thus, it is possible to prevent a decrease in the airtightness between the output terminal 8 and the sealing plate 6.

[0058] Furthermore, the plurality of connecting portions 18 include a first connecting portion 18a and a second connecting portion 18b. The plurality of battery cells 20 include a first battery cell 20a and a second battery cell 20b connected in series via a busbar 2. The first battery cell 20a includes a first battery 4a connected to the first connecting portion 18a, and a second battery 4b that is closer to the second battery cell 20b than the first battery 4a and connected to the second connecting portion 18b. Since the second battery 4b is closer to the second battery cell 20b than the first battery 4a, the conductive path from the second battery 4b to the second battery cell 20b is shorter than the conductive path from the first battery 4a to the second battery cell 20b. Therefore, when the first connecting portion 18a and the second connecting portion 18b have the same shape, a difference in resistance occurs between the two conductive paths. As a result, a difference in the degree of consumption occurs between the first battery 4a and the second battery 4b.

[0059] In response, the first connecting portion 18a and the second connecting portion 18b have shapes such that the resistance difference from the contacts A1 and A2 between each connecting portion 18 and each battery 4 to the third contact B between the second connecting portion 18b and the main body portion 16 decreases. In this embodiment, by making the cross-sectional areas of the first connecting portion 18a and the second connecting portion 18b different, the resistance difference in each conductive path is reduced. More specifically, the cross-sectional area of ​​the second connecting portion 18b is smaller than that of the first connecting portion 18a. As a result, the resistance of the second connecting portion 18b, which is included in a shorter conductive path, increases, and the resistance difference in the two conductive paths decreases. Therefore, deviations in the consumption of each battery 4 can be suppressed.

[0060] Furthermore, the cross-sectional areas C1 and C2 of each connecting portion 18 in the stacking direction X are smaller than the cross-sectional area C3 of the main body 16 in the direction intersecting the stacking direction X. This suppresses the transfer of heat generated in the main body 16 to the battery 4 via the connecting portions 18. Additionally, in the busbar 2, the resistance in the region where the battery cells 20 are connected in series is smaller than the resistance in the region where the batteries 4 are connected in parallel. This suppresses heat generation in the series connection region.

[0061] (Implementation Method 2)

[0062] The battery stack according to Embodiment 2 has the same structure as that according to Embodiment 1, except for the different construction of the busbar. Hereinafter, the battery stack according to this embodiment will be described with a focus on the structure that is different from that of Embodiment 1, and the common structure will be briefly described or omitted.

[0063] Figure 3This is a perspective view showing an enlarged view of the vicinity of the busbar in the battery stack according to Embodiment 2. The busbar 2 of the battery stack 1 (1B) of this embodiment has a main body 16 and a plurality of connecting parts 18. The main body 16 extends in the stacking direction X of the batteries 4. The plurality of connecting parts 18 are electrically connected to the output terminals 8 of each battery 4. Each connecting part 18 is arranged at predetermined intervals along the extending direction (stacking direction X) of the main body 16 and protrudes from the main body 16 in a direction intersecting the stacking direction X (horizontal direction Y).

[0064] The battery stack 1 has a first battery unit 20a and a second battery unit 20b, which are stacked with a first battery 4a and a second battery 4b. The first battery 4a and the second battery 4b in each battery unit 20 are connected in parallel through a busbar 2, and the first battery unit 20a and the second battery unit 20b are connected in series.

[0065] The plurality of connecting portions 18 include a first connecting portion 18a and a second connecting portion 18b. Considering the first battery cell 20a, the first connecting portion 18a is connected to the first battery 4a, which is located away from the second battery cell 20b. The second connecting portion 18b is connected to the second battery 4b, which is located closer to the second battery cell 20b. The first connecting portion 18a and the second connecting portion 18b have shapes such that the difference between the resistance from the first contact A1 to the third contact B and the resistance from the second contact A2 to the third contact B is smaller than if the first connecting portion 18a and the second connecting portion 18b had the same shape. The same configuration applies to the connection between the battery 4 in the second battery cell 20b and the busbar 2.

[0066] In this embodiment, the cross-sectional areas of the first connecting portion 18a and the second connecting portion 18b are different. Specifically, the thickness (dimension in the vertical direction Z) of the second connecting portion 18b is thinner than that of the first connecting portion 18a. Therefore, the cross-sectional area of ​​the second connecting portion 18b is smaller than that of the first connecting portion 18a. Furthermore, the main body 16 includes a thick-walled portion 16a connected to the first connecting portion 18a and having the same thickness as the first connecting portion 18a, and a thin-walled portion 16b connected to the second connecting portion 18b and having the same thickness as the second connecting portion 18b.

[0067] The busbar 2 provided in the battery stack 1 of this embodiment can also reduce the impact of heat generated by the busbar 2 on the battery 4. Furthermore, the difference in resistance can be reduced through the conductive paths from the first battery 4a to the second battery cell 20b and from the second battery 4b to the second battery cell 20b. Therefore, deviations in the consumption of each battery 4 can be suppressed.

[0068] In the battery stack 1 according to Embodiment 2, the following variations can be listed. Figure 4This is a perspective view showing the schematic structure of the busbar provided in the battery stack according to the modified example. In the modified example, the busbar 2 provided in the battery stack 1 has, in plan view, a second plate 24, corresponding to the shape of the thick-walled portion 16a and the first connecting portion 18a, stacked on a first plate 22 whose shape corresponds to the entire body portion 16 and the entire connecting portion 18. This achieves the difference in thickness between the first connecting portion 18a and the second connecting portion 18b, and the difference in thickness between the thick-walled portion 16a and the thin-walled portion 16b. According to this modified example, the same effect as in embodiment 3 can be achieved. Furthermore, since the thickness difference is generated by the stacking of plates, the busbar 2 can be manufactured more easily.

[0069] (Implementation Method 3)

[0070] The battery stack according to Embodiment 3 has the same structure as that of Embodiment 1, except for the different construction of the busbar. Hereinafter, the battery stack according to this embodiment will be described with a focus on the structure that is different from that of Embodiment 1, and the common structures will be briefly described or omitted.

[0071] Figure 5 This is a magnified plan view of the vicinity of the busbar in the battery stack according to Embodiment 3. The busbar 2 of the battery stack 1 (1C) of this embodiment has a main body 16 and a plurality of connecting portions 18. The main body 16 extends in the stacking direction X of the batteries 4. The plurality of connecting portions 18 are electrically connected to the output terminals 8 of each battery 4. Each connecting portion 18 is arranged at predetermined intervals along the extending direction (stacking direction X) of the main body 16 and protrudes from the main body 16 in a direction intersecting the stacking direction X (horizontal direction Y).

[0072] The battery stack 1 has a first battery unit 20a and a second battery unit 20b, which are stacked with a first battery 4a and a second battery 4b. The first battery 4a and the second battery 4b in each battery unit 20 are connected in parallel through a busbar 2, and the first battery unit 20a and the second battery unit 20b are connected in series.

[0073] The plurality of connecting portions 18 include a first connecting portion 18a and a second connecting portion 18b. Considering the first battery cell 20a, the first connecting portion 18a is connected to the first battery 4a, which is located away from the second battery cell 20b. The second connecting portion 18b is connected to the second battery 4b, which is located closer to the second battery cell 20b. The first connecting portion 18a and the second connecting portion 18b have shapes such that the difference between the resistance from the first contact A1 to the third contact B and the resistance from the second contact A2 to the third contact B is smaller than if the first connecting portion 18a and the second connecting portion 18b had the same shape. The same configuration applies to the connection between the battery 4 in the second battery cell 20b and the busbar 2.

[0074] In this embodiment, the first connecting portion 18a and the second connecting portion 18b each have a crank shape with two bends. The first connecting portion 18a extends temporarily along the horizontal direction Y from the front end connected to the output terminal 8, then bends 90°, extends towards the second battery 4b, and then extends again along the horizontal direction Y to connect with the main body 16. The second connecting portion 18b extends temporarily along the horizontal direction Y from the front end connected to the output terminal 8, then bends 90°, extends towards the first battery 4a, and then extends again along the horizontal direction Y to connect with the main body 16. That is, the first connecting portion 18a and the second connecting portion 18b have a shape that is linearly symmetrical about a line M that passes through the third contact point B and is parallel to the horizontal direction Y as the axis of symmetry. In other words, the first connecting portion 18a and the second connecting portion 18b meet before their ends on the main body 16 side reach the main body 16.

[0075] Therefore, the length from the first contact A1 to the third contact B is equal to the length from the second contact A2 to the third contact B. Furthermore, the first connecting portion 18a and the second connecting portion 18b have the same cross-sectional area. Therefore, the resistance of the first connecting portion 18a and the second connecting portion 18b from contacts A1 and A2 to the third contact B is equal.

[0076] The busbar 2 provided in the battery stack 1 of this embodiment can also reduce the impact of heat generated by the busbar 2 on the battery 4. Furthermore, the difference in resistance can be reduced through the conductive paths from the first battery 4a to the second battery cell 20b and from the second battery 4b to the second battery cell 20b. Therefore, deviations in the consumption of each battery 4 can be suppressed.

[0077] (Implementation Method 4)

[0078] The battery stack according to Embodiment 4 has the same structure as Embodiment 1 or 3, except that it has a busbar that combines the busbars of Embodiment 1 and Embodiment 3. Hereinafter, the battery stack according to this embodiment will be described with a focus on the structure that is different from that of Embodiment 1, and the common structures will be briefly described or omitted.

[0079] Figure 6 This is a magnified plan view of the vicinity of the busbar in the battery stack according to Embodiment 4. The busbar 2 of the battery stack 1 (1D) of this embodiment has a main body 16 and a plurality of connecting portions 18. The main body 16 extends in the stacking direction X of the batteries 4. The plurality of connecting portions 18 are electrically connected to the output terminals 8 of each battery 4. Each connecting portion 18 is arranged at predetermined intervals along the extending direction (stacking direction X) of the main body 16 and protrudes from the main body 16 in a direction intersecting the stacking direction X (horizontal direction Y).

[0080] The battery stack 1 has a first battery unit 20a and a second battery unit 20b, which are stacked with a first battery 4a, a second battery 4b, a third battery 4c, and a fourth battery 4d. The first battery 4a to the fourth battery 4d in each battery unit 20 are connected in parallel through a busbar 2, and the first battery unit 20a and the second battery unit 20b are connected in series.

[0081] The plurality of connection portions 18 include a first connection portion 18a, a second connection portion 18b, a third connection portion 18c, and a fourth connection portion 18d. Focusing on the first battery cell 20a, the first connection portion 18a is connected to the first battery 4a, which is furthest from the second battery cell 20b. The second connection portion 18b is connected to the second battery 4b, which is adjacent to the first battery 4a. The third connection portion 18c is connected to the third battery 4c, which is adjacent to the second battery 4b. The fourth connection portion 18d is connected to the fourth battery 4d, which is closest to the second battery cell 20b. The first to fourth connection portions 18a have shapes such that the resistance difference from each connection portion to the contact points A1 to A4 of the output terminal 8 to the third contact point B is smaller than when the first to fourth connection portions 18a have the same shape. The connection structure between the battery 4 in the second battery cell 20b and the busbar 2 is also the same.

[0082] In this embodiment, the cross-sectional areas of the first connecting portion 18a to the third connecting portion 18c are different. Specifically, the width of the second connecting portion 18b is thinner than that of the first connecting portion 18a, and the width of the third connecting portion 18c is thinner than that of the second connecting portion 18b. Furthermore, the fourth connecting portion 18d has a crank shape that bends twice with the same width as the third connecting portion 18c. Therefore, the fourth connecting portion 18d is longer than the third connecting portion 18c.

[0083] In other words, regarding the conductive path from the first contact A1 to the third contact B of the first battery 4a and the first connection 18a, the conductive path from the second contact A2 to the third contact B of the second battery 4b and the second connection 18b, and the conductive path from the third contact A3 to the third contact B of the third battery 4c and the third connection 18c, the cross-sectional area decreases in the order of the first connection 18a, the second connection 18b, and the third connection 18c, thereby reducing the difference in resistance in each conductive path. Furthermore, regarding the conductive path from the fourth contact A4 to the third contact B of the fourth battery 4d and the fourth connection 18d, the fourth connection 18d is longer than the third connection 18c, thereby reducing the difference in resistance in each conductive path from the first contact A1 to the third contact A3 to the third contact B.

[0084] The busbar 2 provided in the battery stack 1 of this embodiment can also reduce the impact of heat generated by the busbar 2 on the battery 4. In addition, the resistance difference in the conductive path from the first battery 4a to the fourth battery 4d to the second battery cell 20b can be reduced. As a result, the consumption deviation of each battery 4 can be suppressed.

[0085] (Implementation Method 5)

[0086] The battery stack according to Embodiment 5 has the same structure as that of Embodiment 1, except for the different construction of the busbar. Hereinafter, the battery stack according to this embodiment will be described with a focus on the structure that is different from that of Embodiment 1, and the common structures will be briefly described or omitted.

[0087] Figure 7 This is a perspective view showing an enlarged view of the vicinity of the busbar in the battery stack according to Embodiment 5. The busbar 2 of the battery stack 1 (1E) of this embodiment has a main body 16 and a plurality of connecting portions 18. The main body 16 extends in the stacking direction X of the batteries 4. The plurality of connecting portions 18 are electrically connected to the output terminals 8 of each battery 4. Each connecting portion 18 is arranged at predetermined intervals along the extending direction (stacking direction X) of the main body 16 and protrudes from the main body 16 in a direction intersecting the stacking direction X (horizontal direction Y).

[0088] The battery stack 1 has a first battery unit 20a and a second battery unit 20b, which are stacked with a first battery 4a and a second battery 4b. The first battery 4a and the second battery 4b in each battery unit 20 are connected in parallel through a busbar 2, and the first battery unit 20a and the second battery unit 20b are connected in series.

[0089] The busbar 2 has a displacement absorbing portion 28 that absorbs the relative displacement between the batteries 4 electrically connected through the busbar 2. The displacement absorbing portion 28 has a portion extending in a direction that is close to separation relative to the batteries 4. In this embodiment, the base end of each connecting portion 18, i.e., the portion connected to the main body 16, is provided with a displacement absorbing portion 28 extending in a direction intersecting the XY plane. The displacement absorbing portion 28 can be formed by bending the base end of each connecting portion 18. In this embodiment, the width of the displacement absorbing portion 28 is equal to the width of the connecting portion 18, but it is not limited to this. Furthermore, the front ends of the main body 16 and each connecting portion 18 are offset in the vertical direction Z and have different heights. Through this displacement absorbing portion 28, the horizontal displacement and dimensional deviation of each battery 4 can be mainly absorbed.

[0090] Furthermore, a displacement absorbing portion 28 extending in a direction intersecting the XY plane is also provided in the main body 16. This displacement absorbing portion 28 is disposed between each connecting portion 18 in the stacking direction X of the batteries 4. The main body 16 of this embodiment has a U-shaped form protruding in the vertical direction Z. The displacement absorbing portion 28 can be formed by bending the main body 16. In this embodiment, the width (dimension in the horizontal direction Y) of the displacement absorbing portion 28 is equal to the width of the main body 16, but it is not limited to this. Through this displacement absorbing portion 28, displacement and dimensional deviations in the stacking direction X of each battery 4 can be mainly absorbed. In addition, displacement and dimensional deviations in the vertical direction Z of each battery 4 are mainly absorbed by changes in the inclination of the connecting portion 18, but can also be absorbed by the displacement absorbing portion 28.

[0091] The busbar 2 provided in the battery stack 1 of this embodiment can also reduce the impact of heat generated by the busbar 2 on the battery 4. Furthermore, the connection between the busbar 2 and each battery 4 can be made more reliable. As a result, the connection reliability between multiple batteries 4 can be improved. Additionally, in this embodiment, by making the cross-sectional area and length of each connection portion 18 different, the resistance difference in the conductive path of each battery 4 can also be reduced.

[0092] This invention is not limited to the embodiments described above. Further modifications, such as combining the embodiments or applying various design changes based on the knowledge of those skilled in the art, are also included within the scope of this invention. New embodiments resulting from combining the above embodiments with each other and adding modifications to the above embodiments combine the effects of both the combined embodiments and the modifications themselves.

[0093] In the above embodiment, the battery 4 is a square battery, but the shape of the battery 4 is not particularly limited, and it can also be cylindrical or the like. Furthermore, the total number of batteries 4 and battery cells 20 included in the battery stack 1, and the number of batteries 4 in each battery cell 20, are not particularly limited. Additionally, the outer casing of the battery 4 can be covered by an insulating sheet such as a shrink tubing.

Claims

1. A battery laminate, comprising: Multiple stacked batteries; and The busbar electrically connects the multiple batteries. The bus bar has: The main body extends in the stacking direction of the battery; and The connecting portion protrudes from the main body in a direction intersecting the stacking direction and is electrically connected to the terminals of each battery. The connecting portion protrudes from the main body portion, such that the main body portion is positioned offset from directly above the terminal. The plurality of batteries are grouped into a plurality of battery cells, each battery cell consisting of at least two batteries. Within each battery cell, the batteries are connected in parallel to each other via the busbar, and the battery cells are connected in series to each other via the busbar. On the upper surface of the main body, the area where batteries from one of the plurality of battery cells are connected in parallel includes a first region and a second region, the first region and the second region being arranged in the stacking direction of the batteries. The first region and the connection portion to the corresponding battery are arranged in the direction in which the connection portion protrudes; the second region and the connection portion to the corresponding battery are also arranged in the direction in which the connection portion protrudes. In the arrangement direction in which the battery and the busbar are arranged, the first region is located closer to the battery than the second region, and the second region is located closer to the end side of the main body than the first region in the stacking direction.

2. The battery laminate according to claim 1, wherein, The cross-sectional area of ​​each connecting portion in the stacking direction is smaller than the cross-sectional area of ​​the main body portion in the direction intersecting the stacking direction.

3. The battery laminate according to claim 1 or 2, wherein, The connecting portion includes a first connecting portion and a second connecting portion. The plurality of battery cells includes a first battery cell and a second battery cell connected in series via the busbar. The first battery unit includes a first battery connected to the first connecting portion, and a second battery that is closer to the second battery unit than the first battery and connected to the second connecting portion. The first connecting portion and the second connecting portion have a shape in which the difference in resistance from the contact point between each connecting portion and each battery to the contact point between the second connecting portion and the main body is smaller than the case where the first connecting portion and the second connecting portion have the same shape.

4. The battery laminate according to claim 3, wherein, The cross-sectional areas of the first connecting part and the second connecting part are different.

5. The battery stack according to claim 1 or 2, wherein, The busbar has a displacement absorbing section that absorbs the relative displacement between batteries electrically connected through the busbar.

6. The battery stack according to claim 5, wherein, The displacement absorbing portion has a portion that extends in a direction relative to the approach separation of the battery.

7. The battery laminate according to claim 1 or 2, wherein, The busbar has a shape in which the resistance in the region where the battery cells are connected in series with each other is smaller than the resistance in the region where the batteries are connected in parallel with each other.

8. The battery laminate according to claim 1, wherein, In the main body portion, the portion constituting the second region has lower resistance compared to the portion constituting the first region.

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