Battery modules and battery units

Abstract

To provide a battery module capable of reducing a deviation in current between a plurality of battery cells.SOLUTION: In a battery module having a plurality of battery blocks in which a plurality of battery cells are connected in parallel, the plurality of battery blocks are arranged in a first direction. The plurality of battery cells are arranged in a second direction crossing the first direction in each of the plurality of battery blocks. Each of the plurality of battery cells are serially connected to each battery cell corresponding to the battery block adjacent thereto in the first direction. The battery module includes: a first surface on which a first portion into / out of which a current flows between an external part and the battery module is arranged, and a second surface on which two second portions which are surfaces facing the first surface and into / out of which the current flows between the external part and the battery module are arranged. In the second direction, the first portion is positioned between the two second portions.SELECTED DRAWING: Figure 1C

Description

[Technical Field]

[0001] The present invention relates to a battery module and a battery unit using the battery module. [Background technology]

[0002] A battery pack device (hereinafter referred to as a "battery module") using secondary batteries such as lithium-ion batteries is known (see Patent Document 1). The battery module includes a plurality of unit batteries connected in series and / or parallel. Such a battery module can be used, for example, as a storage battery module for power storage, automobiles, etc. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2020 / 026789 Summary of the Invention [Problem to be solved by the invention]

[0004] The battery module of Patent Document 1 has room for improvement in terms of minimizing the bias in current between the multiple unit batteries (hereinafter referred to as "battery cells") that make up the battery module. If there is bias in current, differences in power consumption occur between the battery cells, making some battery cells more susceptible to deterioration than others. As a result, it may be difficult to further extend the life of the battery module.

[0005] SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems and to provide a battery module that can further reduce bias in current among a plurality of battery cells. [Means for solving the problem]

[0006] In order to achieve the above-mentioned object, a battery module according to one embodiment of the present invention is a battery module having a plurality of battery blocks in which a plurality of battery cells are connected in parallel, the plurality of battery blocks being arranged in a first direction, and in each of the plurality of battery blocks, the plurality of battery cells being arranged in a second direction intersecting the first direction, and each of the plurality of battery cells being connected in series to a corresponding battery cell in an adjacent battery block in the first direction, the battery module having a first surface on which a first portion through which current flows in or out between the outside and the battery module is arranged, and a second surface opposite to the first surface on which two second portions through which the current flows in or out between the outside and the battery module are arranged, and in the second direction, the first portion is located between the two second portions.

[0007] In order to achieve the above object, a battery unit according to one embodiment of the present invention is a battery unit comprising a first battery module and a second battery module connected in series, wherein each of the first battery module and the second battery module is the battery module, and each of the two second portions of the first battery module is electrically connected to a corresponding one of the two second portions of the second battery module. [Effects of the Invention]

[0008] According to the present invention, it is possible to further reduce bias in current among a plurality of battery cells that constitute a battery module. [Brief explanation of the drawings]

[0009] [Figure 1A] 1 is a schematic perspective view of a battery module according to a first embodiment of the present invention, viewed obliquely from above. [Figure 1B] 1B is a schematic perspective view of the rear side of the battery module of FIG. 1A, viewed obliquely from above. [Figure 1C] FIG. 1B is a schematic top view of the battery module of FIG. 1A. [Figure 1D]FIG. 1B is a schematic bottom view of the battery module of FIG. 1A. [Figure 2] 1B is a schematic top view showing the arrangement of cells in the battery module of FIG. 1A. FIG. [Figure 3] FIG. 2 is a schematic bottom view showing an enlarged portion of the cell tab. [Figure 4] FIG. 10 is a schematic top view illustrating the arrangement of cells in a battery module of a reference example. [Figure 5] FIG. 10 is a diagram showing the results of a simulation of the current density distribution occurring at the cell terminal connection part during charging in the battery module of the reference example. [Figure 6] FIG. 4 is a diagram showing the results of a simulation of the current density distribution occurring at the cell terminal connection part during charging in the battery module of the first embodiment. [Figure 7] FIG. 4 is a diagram showing the results of a simulation of the current density distribution occurring at the cell terminal connection part during charging in the battery module of the first embodiment. [Figure 8] FIG. 10 is a schematic top view showing an example of the arrangement of cells in a battery module according to a modified example. [Figure 9] FIG. 10 is a schematic top view showing another example of the arrangement of cells in the battery module. [Figure 10] FIG. 10 is a schematic top view showing yet another example of the arrangement of cells in the battery module. [Figure 11] FIG. 5 is a schematic perspective view of a battery unit according to a second embodiment of the present invention. [Figure 12A] 12 is a schematic perspective view of the battery unit of FIG. 11 with the case and other components removed, viewed obliquely from above. [Figure 12B] 12B is a schematic perspective view of the rear side of the battery unit of FIG. 12A, seen obliquely from above. FIG. [Figure 13] 10A and 10B are schematic enlarged bottom views illustrating another method of connecting the tab and the bus bar. [Figure 14] FIG. 10 is a schematic perspective view of a battery unit according to a modified example. [Figure 15] FIG. 1 is a diagram illustrating a conventional circuit configuration of a battery module. DETAILED DESCRIPTION OF THE INVENTION

[0010] (Findings that form the basis of the present invention) The present inventors have conducted extensive research into ways to further reduce bias in current between battery cells that make up a battery module, and have come to the following findings.

[0011] FIG. 15 is a diagram illustrating a conventional circuit configuration of a battery module. The illustrated battery module 900 includes a battery block L1 having battery cells (hereinafter abbreviated as "cells") a1 to a5 connected in parallel with each other, and a battery block L2 having cells b1 to b5 connected in parallel with each other. The cells a1 to a5 of the battery block L1 are connected in series with the cells b1 to b5 of the battery block L2, respectively. These cells are typically connected in parallel and in series by multiple tabs (hereinafter collectively referred to as "cell terminal connections"). The cell terminal connections have a first portion 91 and a second portion 92 through which current flows in and out from the outside. In this example, the first portion 91 is located near the cell a5 at the right end of the battery block L1, and the second portion 92 is located near the cell b1 at the left end of the battery block L2. One of the first portion 91 and the second portion 92 serves as an inflow portion through which a current flows in, and the other serves as an outflow portion through which a current flows out.

[0012] For example, when charging the battery module 900, a current flows into the battery module 900 from the first portion 91 and then flows out from the second portion 92. At this time, it is preferable that the current flows evenly through all of the cells a1 to a5 and b1 to b5. However, because the current tends to flow between the first portion 91 and the second portion 92 through the shortest path, i.e., the path with the least resistance, there is a possibility that the current may be unevenly distributed among the cells. For example, in the battery block L1, the current supplied to the positive electrode of the cell a1, which is far from the first portion 91, may be smaller than the current supplied to the positive electrode of the cell a5, which is closer to the first portion 91. Furthermore, although it is preferable that the current flows between the cells connected in series (in the column direction), some of the current may flow in an undesired direction. For example, it is desirable for current Ir to flow from the negative electrodes of cells a1 to a5 in battery block L1 to the positive electrodes of corresponding cells (here, cells in the same column) in battery block L2. However, some current Iw may attempt to take the shortest path and flow to an uncorresponding cell (a cell in a different column) in battery block L2. If current imbalance occurs between cells, a large amount of current may flow into a specific cell, causing it to deteriorate faster than the other cells. This makes it difficult to improve the lifespan of the battery module.

[0013] The inventors have found that the above-mentioned current imbalance can be suppressed by arranging a first region on a first surface of a battery module, through which current flows in and out between the outside and the battery module, and two second regions on a second surface opposite the first surface, through which current flows in and out between the outside and the battery module, and by positioning the first region between the two second regions in the cell arrangement direction in each battery block. Based on this novel finding, the inventors have arrived at the present invention.

[0014] Hereinafter, embodiments of the present invention will be described with reference to the drawings. However, the present invention is not limited to these embodiments. In addition, substantially identical components in the drawings are designated by the same reference numerals. For illustrative purposes, the dimensions of each element in the drawings may be exaggerated and are not necessarily drawn to scale. For reference, the drawings schematically show mutually orthogonal X-, Y-, and Z-axes.

[0015] For ease of explanation, terms indicating directions such as "up," "down," "right," "left," "side," "front," and "back" are used below assuming a state during normal use, but are not intended to limit the state of use of the battery module or battery unit according to the present invention. Furthermore, in this specification, "perpendicular" or "substantially perpendicular" means within a range of 90°±10°. "Parallel" or "substantially parallel" means within a range of, for example, ±5°.

[0016] First Embodiment Fig. 1A is a schematic perspective view of a battery module according to a first embodiment of the present invention, viewed obliquely from above, and Fig. 1B is a schematic perspective view of the back side of the battery module of Fig. 1A, viewed obliquely from above. Fig. 1C is a schematic top view of the battery module of Fig. 1A, and Fig. 1D is a schematic bottom view of the battery module of Fig. 1A. Fig. 2 is a schematic top view showing the arrangement of cells in the battery module of Fig. 1A.

[0017] The battery module 100 is an assembled battery including a plurality of battery cells (cells) 10 connected in series and / or parallel. The cells 10 are, for example, cylindrical batteries. The plurality of cells 10 may be arranged standing in a substantially vertical direction (here, the Z direction) with their respective positive or negative terminals positioned at the top. The cells 10 may also be arranged on an imaginary plane parallel to the XY plane. The type, shape, structure, material, etc. of the cells 10 are not particularly limited. The cells 10 are preferably rechargeable secondary batteries, and may be, for example, lithium-ion batteries, nickel-metal hydride batteries, nickel-cadmium batteries, lithium polymer batteries, etc. Furthermore, the shape of the cells 10 is not limited to cylindrical, and may be other shapes such as rectangular.

[0018] The battery module 100 includes a plurality of battery blocks L1 to L8 (hereinafter sometimes collectively referred to as "battery blocks L"). Each of the plurality of battery blocks L has a plurality of cells 10 connected in parallel. The number of cells 10 in the plurality of battery blocks L may be the same.

[0019] A plurality of (eight here) battery blocks L are arranged in the Y direction. A plurality of (fifteen here) cells 10 in each battery block L are arranged in the X direction perpendicular to the Y direction. In this specification, the arrangement direction of the battery blocks L may be referred to as the "first direction," the arrangement direction of the cells 10 in each battery block L as the "second direction," and the direction perpendicular to the first and second directions (Z direction) as the "third direction." Here, an example will be described in which the first direction and the second direction are perpendicular (or approximately perpendicular) to each other, but it is sufficient that the first direction and the second direction intersect in a plan view seen from the third direction. The "second direction" may also be referred to as a direction intersecting the first direction and running along the end face of the cell 10 (which in this embodiment may also be referred to as the face on which the electrodes of the cylindrical cell 10 are provided).

[0020] Each cell 10 in each battery block L is connected in series to a corresponding cell 10 in another battery block L adjacent in the Y direction. Therefore, a plurality of (eight in this case) cells 10 arranged in the Y direction are connected in series. A string R consisting of a plurality of (eight in this case) cells 10 arranged in the Y direction and connected in series is called a "battery string." As schematically shown in FIG. 2, the battery module 100 has, for example, 15 battery strings R1 to R15. The number of battery strings R in the battery module 100 may be the same as the number of cells 10 in each battery block L. Furthermore, the number of cells 10 constituting each battery string R may be the same as the number of battery blocks L.

[0021] In this specification, when a plurality of battery blocks L (or cells 10) are "arranged in a first direction (Y direction)," it means that these battery blocks L (or cells 10) are arranged in the Y direction (first direction) as a whole, and may be arranged in a zigzag pattern, for example. The intervals between two adjacent battery blocks L (or two cells 10) may be the same or different. Similarly, when a plurality of cells 10 are "arranged in the X direction (second direction)," it means that these cells 10 are arranged along the X direction (second direction) as a whole, and may be arranged in a zigzag pattern. The intervals between two adjacent cells 10 may be the same or different.

[0022] 1A to 2, in a plan view from the Z direction, the battery blocks L1 to L8 may be arranged in the Y direction as a whole, with the battery blocks L1 to L8 alternately shifted in the +X direction and the -X direction by half the cell arrangement pitch. This allows the cells 10 to be arranged more densely. Corresponding cells in the multiple battery blocks L1 to L8 are connected in series to form a battery string R. Therefore, the battery string R may extend in a zigzag pattern in the Y direction in a plan view from the Z direction.

[0023] The battery module 100 has an upper surface 100a and a lower surface 100b that face each other in the Z direction, and two side surfaces 100c and 100d that face each other in the Y direction. The side surface 100c is the side surface that faces the battery block L1, and the side surface 100d is the side surface that faces the battery block L8. The cells 10 in each battery block L are arranged so that the same pole (positive or negative) is located on the upper surface 100a. The pole of the cells 10 located on the upper surface 100a of each battery block L is different from the pole located on the upper surface 100a of another battery block L adjacent in the Y direction. For example, the positive (or negative) pole of each cell 10 in the battery blocks L1, L3, L5, and L7 may be located on the upper surface 100a, and the negative (or positive) pole of each cell 10 in the battery blocks L2, L4, L6, and L8 may be located on the upper surface 100a. The state of use of the battery module 100 is not limited to the state shown in the drawing. The battery module 100 may be used with the surface 100a facing downward and the surface 100b facing upward.

[0024] The battery module 100 further includes a cell terminal connection portion 30 configured to connect the cells 10 of each battery block L in parallel and to connect the cells 10 of each battery string R in series. In this embodiment, the cell terminal connection portion 30 has a plurality of tabs 31 to 37, 41, 42. The specific structure of the cell terminal connection portion 30 will be described later.

[0025] The battery module 100 has a first portion S11 through which current flows in or out between the outside and the battery module 100, and two second portions 21 and 22 through which current flows in or out between the outside and the battery module 100. Current flows in from the outside through the first portion S11 and flows out to the outside through the second portion. Alternatively, current flows in from the outside through the second portions S21 and S22 and flows out to the outside through the first portion S11.

[0026] The first portion S11 is disposed on the first surface f1 of the battery module 100, and the second portions S21 and S22 are disposed on the second surface f2 opposite to the first surface f1. On the second surface f2, the second portions S21 and S22 are disposed at a distance in the X direction. The first portion S11 is disposed on the first surface f1 so as to be located between the two second portions S21 and S22 in the X direction. In this embodiment, for example, one of the side surface 100c on the battery block L1 side and the side surface 100d on the battery block L8 side (here, the side surface 100c) is the first surface f1, and the other (here, the side surface 100d) is the second surface f2.

[0027] The first region S11 and / or the second regions S21, S22 may be disposed on any tab of the cell terminal connection portion 30. For example, a tab including the first region S11 may be provided on the first surface f1. Similarly, tabs including the second regions S21, S22 may be provided on the second surface f2. Note that "the first region S11 is disposed on the first surface f1" may include the case where the first surface f1 is the side surface of the battery module 100 that is closest to the first region S11. Similarly, "the second regions S21, S22 are disposed on the second surface f2" may include the case where the second surface f2 is the side surface of the battery module 100 that is closest to the second regions S21, S22.

[0028] <Cell terminal connection part> The cell terminal connection portions include, for example, tabs 31 to 34 located on the upper surface 100a of the battery module 100, tabs 35 to 37 located on the lower surface 100b, and tabs 41 and 42 including extensions that extend from the upper surface 100a or the lower surface 100b to the side surfaces 100c and 100d of the battery module 100. In this specification, the tabs 31 to 37 located on the upper surface 100a or the lower surface 100b of the battery module are referred to as "cell tabs," and the tabs 41 and 42 that have extensions on the side surfaces 100c and 100d of the battery module 100 are referred to as "side tabs."

[0029] The cell tabs 31 to 34 are arranged at intervals from one another on the upper surface 100a of the battery module 100. The cell tabs 31 to 34 may extend in the X direction as a whole. The cell tab 31 electrically connects the positive electrode terminals of the 15 cells 10 in the battery block L1 to the negative electrode terminals of the 15 cells 10 in the battery block L2. Similarly, the cell tabs 32 to 34 electrically connect the positive electrode terminals of the cells 10 in the battery blocks L3, L5, and L7 to the negative electrode terminals of the cells 10 in the battery blocks located on the side surface 100d of those battery blocks. On the other hand, the cell tabs 35 to 37 are arranged at intervals from one another on the lower surface 100b of the battery module 100. The cell tabs 35 to 37 may extend in the X direction as a whole. The cell tab 35 electrically connects the positive electrode terminals of the 15 cells 10 in the battery block L2 to the negative electrode terminals of the 15 cells 10 in the battery block L3. Similarly, the cell tabs 36, 37 electrically connect the positive electrode terminals of the cells 10 in the battery blocks L4, L6 to the negative electrode terminals of the cells 10 on the side surface 100d of those battery blocks. In the illustrated example, each cell 10 in one battery block L is located between two adjacent cells 10 in an adjacent battery block L, and therefore the cell tabs 31 to 37 may extend in a zigzag pattern in the X direction, for example.

[0030] The side tab 41 has, for example, an L-shape extending from the lower surface of the battery block L1 to the side surface 100c. The side tab 41 electrically connects the negative electrode terminals of the 15 cells 10 in the battery block L1. Similarly, the side tab 42 has, for example, an L-shape extending from the lower surface of the battery block L8 to the side surface 100d. The side tab 42 electrically connects the positive electrode terminals of the 15 cells 10 in the battery block L8. Note that the poles of the cell terminals electrically connected to the side tabs 41, 42 may be different from those in the illustrated example.

[0031] The material of each tab constituting the cell terminal connection portion 30 is not particularly limited, but may be, for example, an electrically conductive material such as metal, such as copper, copper alloy, aluminum, or aluminum alloy. The cell tabs 31-37 and the side tabs 41, 42 may be made of the same or different materials. Furthermore, the structure, shape, and number of each tab constituting the cell terminal connection portion are not limited to the example shown in the drawings and may be selected appropriately. For example, the cells 10 of the battery blocks L1, L8 may be connected in parallel using cell tabs instead of side tabs.

[0032] In this embodiment, each cell tab 31-37 has a first region that electrically connects cells 10 in the same battery string R and a second region that electrically connects cells 10 in a different battery string R. FIG. 3 is a schematic bottom view showing an enlarged portion of a cell tab, illustrating cell tab 35. As shown in the figure, cell tab 35 has a first region 30a that connects two cells in the same battery string R (here, battery strings R8 and R9) and a second region 30b that connects two cells in a different battery string R. The other cell tabs 31-34, 36, and 37 have a similar configuration. As will be described later, in each battery string R, current preferably flows through the first region 30a of cell tabs 31-37 as indicated by arrow Ir. It is desirable to keep current Iw flowing through the second region 30b small. This allows current to flow more evenly through each battery string R.

[0033] <First and second parts> The first region S11 and / or the second regions S21, S22 are disposed in, for example, the cell terminal connection portion. The first region S11 and / or the second regions S21, S22 may be a portion of the cell terminal connection portion that is electrically connected to a bus bar. Alternatively, when the bus bar and the cell terminal connection portion are electrically connected by, for example, wire bonding, the first region S11 and / or the second regions S21, S22 may be a portion of the cell terminal connection portion to which a bonding wire is joined. Furthermore, when the battery module 100 and another battery module are connected in series via a tab connection portion, the first region S11 and / or the second regions S21, S22 may be a portion of the cell terminal connection portion that is electrically connected to the tab connection portion. In this specification, "electrically connected" means that two members (or regions) can be electrically connected to each other, and the two members (or regions) may be directly connected to each other or indirectly connected to each other via another conductive component.

[0034] The portions of the cell terminal connection portion (e.g., side tabs) that will become the first portion S11 and / or the second portions S21, S22 may be thicker or wider than the other portions to facilitate connection to bus bars, tab connection portions, etc., or to achieve lower resistance. Alternatively, the portions of the cell terminal connection portion (e.g., side tabs) that will become the first portion S11 and / or the second portions S21, S22 may have the same structure as the other portions. This allows for a high degree of freedom in selecting the position and number of each portion.

[0035] As described above, the first portion S11 is located between the two second portions S21 and S22 in the X direction. The first portion S11 may be located in the center or approximately the center of the two second portions S21 and S22 in the X direction. With reference to FIG. 1C , "the first portion S11 is located in the center (or approximately the center) of the second portions S21 and S22" may include not only the case where the first portion S11 is located on the center point Xc of the second portions S21 and S22 in the X direction on the first surface f1, but also the case where the first portion S11 is located near the center point Xc. Here, the central point Xc refers to the intersection of a perpendicular bisector α drawn between a point on the second region S21 closest to the second region S22 and a point on the second region S22 closest to the second region S21 in a plan view from the Z direction, and the perpendicular bisector α and the first surface f1. "Close to the central point Xc" includes the case where the distance (shortest distance) dx between the central point Xc and the first region S11 in the X direction is equal to or less than the width w of one cell 10 in the X direction (hereinafter referred to as "cell width w") (dx≦w). The distance dx may be less than the cell width w. Furthermore, "the first region S11 is located in the center (or approximately in the center) of the second regions S21 and S22" may include the case where the absolute value |d1-d2| of the difference in the X direction between the shortest distance d1 between the first region S11 and the second region S21 and the shortest distance d2 between the first region S11 and the second region S22 is equal to or less than the cell width w (|d1-d2|≦w). The absolute value |d1-d2| may be less than the cell width w.

[0036] In the illustrated example, the side surface 100c is the first surface f1, and the side surface 100d is the second surface f2. The first portion S11 is disposed on a first tab that connects in parallel the cells 10 included in the battery block L (here, battery block L1) closest to the first surface f1. The first tab is, for example, a side tab 41. The second portions S21 and S22 are disposed on a second tab that connects in parallel the cells 10 included in the battery block L (here, battery block L8) closest to the second surface f2. The second tab is, for example, a side tab 42. The second portion S21 may be disposed on one end of the second tab in the X direction, and the second portion S22 may be disposed on the other end of the second tab in the X direction. For example, the second portions S21 and S22 may be disposed on the second tab at positions corresponding to the battery rows R1 and R15 ( FIG. 2 ) on both ends, respectively. The first portion S11 may be located in the center (or approximately the center) of the first tab in the X direction.

[0037] The first tab and the second tab may be cell tabs, in which case the first portion and the second portion may be bonding portions of the cell tab that are connected to bonding wires (see FIG. 13).

[0038] <Effects> In this embodiment, the first region S11 is located between the two second regions S21 and S22 in the X direction. Therefore, as shown in FIG. 2 , the battery module 100 can be divided into a first portion (first block) 51 defined by the first region S11 and one of the second regions S21, and a second portion (second block) 52 defined by the first region S11 and the other of the second regions S22. In the first portion 51, current flows mainly between the first region S11 and the second region S21. In the second portion 52, current flows mainly between the first region S11 and the second region S22. In a plan view from the Z direction, lines p1 and p2 indicate the shortest current paths in the first portion 51 and the second portion 52. The shortest paths p1 and p2 are straight lines connecting the current inflow and outflow points and do not necessarily coincide with the current paths on the cell terminal connection portions (tabs). In plan view from the Z direction, the shortest paths p1 and p2 are, for example, V-shaped.

[0039] As described above, according to this embodiment, the battery module 100 can be divided into multiple sections 51 and 52 in the X direction to allow current to flow, thereby reducing the current density difference in the X direction. Furthermore, the shortest current paths p1 and p1 in each section 51 and 52 are shorter than the shortest paths when current flows without dividing the battery module 100 into multiple sections. This reduces current bias caused by the current passing through the shortest path, thereby making the current density distribution at the cell terminal connection section more uniform. As a result, the difference in current flowing through the cells 10 constituting the battery module 100 is reduced, preventing a particular cell from deteriorating faster than the other cells. In other words, the difference in the rate of deterioration among the cells 10 is reduced. This further improves the lifespan of the battery module 100.

[0040] Furthermore, when the first portion S11 is positioned approximately in the center of the two second portions S21 and S22 in the X direction, the difference in length between the shortest path p1 of the first portion 51 and the shortest path p2 of the second portion 52 becomes small (preferably the same), thereby further reducing the difference in current density between the first portion 51 and the second portion 52. In a plan view from the Z direction, the shortest path p1 of the first portion 51 and the shortest path p2 of the second portion 52 may be line-symmetric or approximately line-symmetric with respect to the perpendicular bisector α (see, for example, FIG. 8, which will be described later). This allows current to flow symmetrically from the first portion S11 to each of the second portions S21 and S22, thereby further reducing the difference in current density.

[0041] Furthermore, by arranging the first region S11 on the first tab and the second regions S21 and S22 on one end and the other end of the second tab in the X direction, respectively, the cell terminal connection portion can be divided into multiple portions to allow current to flow without complicating the structure of the battery module 100. Furthermore, the positions and numbers of the first region S11 and the second regions S21 and S22 in the X direction can be easily adjusted (set). Using side tabs 41 and 42, which have larger areas and thicknesses than the cell tabs, as the first and second tabs facilitates electrical connection between the bus bar or the like and the first region S11 and the second regions S21 and S22, and enables formation of a connection with lower resistance. Furthermore, using the side tabs 41 and 42 as the first and second tabs allows for serial connection of multiple battery modules by arranging tab connections on the side surfaces of the battery units when stacking the battery modules to form a battery unit. On the other hand, if a cell tab is used as the first tab and / or the second tab, it becomes easier to join bonding wires for connecting the battery modules in series when arranging multiple battery modules side by side to form a battery unit.

[0042] In the battery module 100 shown in FIGS. 1A to 2, the number of cells constituting one battery string R (=the number of battery blocks L) N R is 8, and the number of cells that make up one battery block L is N L is 15, but the number of these cells N R , N L is not limited to the example shown in the figure. R , N L The number of cells in the battery block L is N as long as it is 2 or more, and can be set appropriately depending on the application of the battery module. L may be 3 or more. L If the number of cells in the battery block L is 3 or more, the current imbalance can be reduced more reliably by dividing the battery module into multiple parts in the X direction and passing the current through them. L is the number of cells in the battery string R, N R may be more than (N L <N R) In such a battery module, the length is increased in the X direction, and therefore, by applying this embodiment, it is possible to more effectively reduce bias in the current in the X direction.

[0043] <Current density distribution at cell terminal connection> The current density distribution at the cell terminal connection parts of the battery module of this embodiment and the battery module of the reference example was investigated by computer simulation, and the results are described below. The battery module of the reference example has a structure in which one first region and one second region are arranged.

[0044] First, the structure of a battery module of a reference example will be described. FIG. 4 is a schematic top view illustrating the arrangement of cells in a battery module 800 of a reference example. The arrangement of the cells 10 in the battery module 800 is the same as that in the battery module 100 shown in FIG. 2. However, one first region S1 and one second region S2 are provided on the first surface f1 and the second surface f2, respectively. In FIG. 4, the first region S1 is located at the right end of the first surface f1, and the second region S2 is located at the left end of the second surface f2. The shortest path q between the first region S1 and the second region S2 substantially coincides with the diagonal of the rectangular top surface of the battery module 800.

[0045] FIG. 5 shows simulation results illustrating the current density distribution when a current flows from the external source into the second region S2 and flows out of the first region S1 during charging of the battery module 800 of the reference example. In FIG. 5 and the following FIGS. 6 and 7, arrows indicate the current at each point of the cell terminal connection (cell tabs 31-37). Cells are not shown. The direction of the arrow indicates the direction of current flow at that point, and the thickness of the arrow indicates the magnitude of the current density. Furthermore, solid arrows indicate current flowing in the desired direction (current flowing between cells in the same battery string R), while dashed arrows indicate current flowing in the wrong direction (current flowing between cells in different battery strings R). As described above with reference to FIG. 3, current Ir flows through the first region 30a of each cell tab, and current flowing in the wrong direction (hereinafter referred to as "wrong-direction current") Iw flows through the second region 30b of each cell tab.

[0046] As can be seen from FIG. 5, the current density distribution at the cell terminal connection portion of the battery module 800 is quite nonuniform. This is thought to be because the current flowing through the cell tab tends to take the shortest path q (FIG. 4) to minimize resistance, resulting in a tendency for the misdirection current Iw to occur. For example, in areas 801-803 of the cell terminal connection portion shown in FIG. 5, the misdirection current Iw may be equal to or greater than the current Ir flowing in the desired direction. As the proportion of the misdirection current Iw increases, the current bias becomes more pronounced. Furthermore, for example, in the cell tab 34, the current density differs significantly between the area near the second region S2, which is the inflow region, and the area 801, located to the right of the center. Therefore, in a battery block electrically connected to the cell tab 34, the current supplied to some cells may be, for example, about half the current supplied to the cell closest to the second region S2. Although not shown, a similar current bias can occur during discharge. In this way, if there is a difference in the current flowing through the cell depending on its position, the consumption within the cell will differ, and some cells (for example, cells that flow more current than other cells during charging and discharging) will be more likely to deteriorate.

[0047] Fig. 6 shows simulation results illustrating the current density distribution when a current flows into the first region S11 and flows out from the second regions S21 and S22 during discharge of the battery module of this embodiment. Fig. 7 shows the current density distribution when a current flows in the opposite direction to Fig. 6, i.e., when a current flows from the outside into the second regions S21 and S22 and flows out from the first region S11 during charge of the battery module of this embodiment.

[0048] As shown in FIGS. 6 and 7 , the current density distribution in this embodiment is more uniform than that in the reference example shown in FIG. 5 . For example, the misdirection current Iw is barely visible in the current density distributions in FIGS. 6 and 7 . That is, the density of the misdirection current Iw is so small that it is not even indicated by an arrow. Furthermore, in FIG. 6 , in the cell tab 31 adjacent to the first surface f1, the difference in current density between the central portion near the first region S11, which is the current inflow region, and both ends far from the first region S11 is kept small. Similarly, in FIG. 7 , for example, in the cell tab 34 adjacent to the second surface f2, the difference in current density between the both ends near the second regions S21 and S22, which are the current inflow regions, and the central portion far from the second regions S21 and S22 is kept small. This is thought to be because, in the battery module of this embodiment, current can flow through the battery module by dividing it into two portions in the X direction, as described with reference to FIG. 2 . As a result, the shortest paths p1 and p2 (see FIG. 2) between the inflow portion and outflow portion in each portion can be made shorter than the shortest path q in the reference example shown in FIG. 4. Although a current density difference may occur within each portion, the current density difference is smaller than the current density difference occurring in the battery module of the reference example.

[0049] <Modification> 1A to 2, an example has been described in which one first portion is provided on the first surface and two second portions are provided on the second surface, but the number of first portions and second portions is not particularly limited. At least two first portions may be provided on the first surface, and at least three second portions may be provided on the second surface.

[0050] 8 is a schematic top view showing the arrangement of battery modules of Modification 1. Battery module 101 of Modification 1 includes three battery blocks L1 to L3. Each of battery blocks L1 to L3 has nine cells 10 connected in parallel. Note that the number of battery blocks and the number of cells in each battery block are merely examples and are not limited to the example shown in FIG. 8.

[0051] In the battery module 101, two first regions S11 and S12 are arranged on the first surface f1, and three second regions S21 to S23 are arranged on the second surface f2. The second regions S21 to S23 are arranged at a distance in the X direction. In the X direction, the first region S11 is located between two adjacent second regions S21 and S22 among the second regions S21 to S23, and the first region S12 is located between two adjacent second regions S22 and S23. This allows current to flow through the battery module 101, divided into four portions, a first portion 51 to a fourth portion 54, in a plan view from the Z direction. Each of the first portion 51 to the fourth portion 54 is defined by one first region and a second region adjacent to that first region. For example, the first portion 51 is defined by the first region S11 and the second region S21. The shortest current paths p1 and p2 in the first portion 51 and the second portion 52 are, for example, V-shaped. Similarly, the shortest current paths p3 and p4 in the third portion 53 and the fourth portion 54 are also, for example, V-shaped.

[0052] The second regions S21 to S23 may be arranged on the second surface f2 at equal or approximately equal intervals in the X direction. Here, "arranged at equal (or approximately equal) intervals" refers not only to the case where the difference between the distances (shortest distances) d3 and d4 between two adjacent second regions in the X direction is equal (d3 = d4), but also to the case where, for example, the absolute value of the difference between these distances is equal to or less than the cell width w (|d3 - d4| ≦ w). The absolute value |d3 - d4| may be less than the cell width w. Alternatively, the second regions S21 to S23 may be arranged so that the number of cells located between two adjacent second regions is the same or approximately the same (for example, the difference in the number of cells is within one). Furthermore, the first regions S11 and S12 may be located in the center (or approximately the center) of the two adjacent second regions in the X direction.

[0053] Three or more first portions may be arranged on the first surface f1, and four or more second portions may be arranged on the second surface f2. Even in this case, the first portions and the second portions may be arranged such that one first portion is located between each pair of adjacent second portions in the X direction, as in the example shown in FIG.

[0054] According to this modification, the battery module 101 can be divided into more sections 51-54 in the X direction (four in the example shown in FIG. 8 ) to allow current to flow. For example, if the number of first sections arranged on the first surface f1 is n, the battery module 101 can be divided into 2×n sections in the X direction to allow current to flow. Increasing the number of sections and reducing the size of each section 51-54 can further shorten the shortest current paths p1-p4 in each section 51-54. This can more effectively reduce the difference in current density distribution that occurs at the cell terminal connection section of the battery module 101. For example, when the battery module 101 is long in the X direction (for example, three times or more the length in the Y direction) or when the number of battery strings m is large (for example, three times or more) relative to the number of battery blocks n, providing two or more second sections can provide a more significant effect.

[0055] Furthermore, when the second regions S21 to S23 are arranged at equal or approximately equal intervals in the X direction on the second surface f2, the difference in current density between the multiple portions 51 to 54 can be reduced, thereby making the current density distribution of the cell terminal connection portion more uniform.

[0056] The second regions S21 to S23 may be arranged at equal intervals in the X direction, and the first region S11 may be located in the center of two adjacent second regions. This causes the number of cells 10 arranged in the X direction to be the same in each of the first to fourth regions 51 to 54 (three in the illustrated example), making it possible to pass current more evenly through the four regions 51 to 54.

[0057] <Number of battery blocks, number of cells, number of first sections, and number of second sections> Hereinafter, the number of first sections n, the number of second sections m, the number of cells constituting each battery string R (= the number of battery blocks L) N in the battery module of this embodiment will be referred to as R , and the number of cells that make up each battery block L, N L This article explains:

[0058] (a) Number of first regions n, number of second regions m The number n of first portions arranged on the first surface f1 and the number m of second portions arranged on the second surface f2 are not particularly limited, and may vary depending on the application of the battery module, the shape of the cells 10, the number N of battery blocks L, etc. L , the number of battery strings R is N R The number N of battery strings R can be set appropriately depending on the arrangement pitch of the cells 10 or the battery block L. R is the same as the number of cells included in each battery block L, for example.

[0059] The number m of second portions arranged on the second surface f2 is preferably greater than the number n of first portions arranged on the first surface f1 (m>n). By intentionally making the number of current inflow portions and the number of current outflow portions different in this way, it is possible to divide the battery module into multiple portions to allow current to flow while reducing the total number of these portions (n+m), thereby shortening the shortest path for current. The n first portions and m second portions are preferably arranged so that each portion defined by these portions has a shortest path that extends diagonally across the multiple battery strings R (intersecting in the Y direction).

[0060] The number m of second regions may be one more than the number n of first regions (m=n+1). By arranging one first region between each pair of adjacent second regions in the X direction, the total number of these regions (n+m) can be reduced while dividing the battery module into 2×n sections. Reducing the total number of first regions and second regions can reduce manufacturing costs. Furthermore, it can also reduce the complexity of the connection structure with bus bars and the like. From the viewpoint of manufacturing costs, for example, n=1 and m=2 (see FIG. 2) or n=2 and m=3 (see FIG. 8) may be used.

[0061] When the number m of second regions is one more than the number n of first regions, the positions of the second regions and the first regions may be determined, for example, as follows: First, two second regions are arranged at both ends of the second surface f2 (or near both ends). The second regions may be arranged near cells at both ends of the battery block close to the second surface f2. Next, the remaining second regions are arranged between these second regions. The remaining second regions may be arranged at equal intervals (or approximately equal intervals) in the X direction, and / or the remaining second regions may be arranged so that the number of cells located between two adjacent second regions is the same or approximately the same (for example, the difference in the number of cells is within one). Next, first regions are arranged on the first surface f1. Each first region is arranged between two adjacent second regions in the X direction. Each first region may be arranged in the center (or approximately the center) of two adjacent second regions in the X direction. The positions of these parts are not limited to the positions exemplified here, and can be designed taking into consideration the structure of the battery module, the manufacturing process, manufacturing costs, etc.

[0062] (b) Number of cells N in battery block L L and the number of cells in the battery string R, N R The number of cells that make up one battery block L is N L is the number of cells N that make up one battery string R R may be more than (N L >N RIn a conventional battery module, the number of cells in a battery block is N. L When the battery block is long in the X direction, a current density distribution tends to occur in the X direction. When the present invention is applied to a battery module with such a structure, the current can be divided into multiple parts in the X direction and flowed through them, resulting in a more significant effect.

[0063] (c) The number of first portions n and the number of cells N in the battery block L L and the number of cells in the battery string R, N R Relationship with The number of first sections n, the number of second sections m, and the number of cells N in the battery block L L , the number of cells in the battery string R is N R , and the positions of the first and second portions may be set so as to divide the battery module into a plurality of square portions. A "square portion" is a portion defined by the first and second portions, and has a number N of cells arranged in the X direction. x and the number of cells arranged in the Y direction, N y The number of cells in the area is equal to or approximately equal to the number of cells in the area (the difference in the number of cells is 1 or less). x -N y |≦1). Number of cells in the Y direction N y is the number of battery blocks L, i.e., the number of cells N that make up each battery string R. R The number of cells in the X direction is N x is the same as the number of battery strings R located in that portion. The length in the X direction and the length in the Y direction of the square portion may be the same or approximately the same (the difference in length is equal to or less than the cell width w).

[0064] In each portion defined by the first portion and the second portion, the number of cells in the X direction is N x is the number of cells in the Y direction, N y If the number of cells in each part is too large compared to N, a difference in current density in the X direction is likely to occur within that part. xWhen trying to reduce the number of first and second parts, the total number (n+m) of the first and second parts increases. If the total number becomes too large, manufacturing costs may increase, and when a unit including a battery module is constructed, the unit structure may become complicated. In contrast, if each part defined by the first and second parts is a square part as described above, it is possible to reduce the total number of first and second parts, thereby suppressing increases in manufacturing costs, and to realize a battery module in which current imbalance is more effectively reduced.

[0065] Below, we will explain an example of a structure in which a battery module can be divided into multiple square parts, and the number of first parts n and the number of cells N in a battery block L to obtain such a structure. L and the number of cells in the battery string R, N R A preferred relationship between

[0066] ·1st structure Referring again to Figure 8, the number of first sections n, the number of second sections m, and the number of cells N of the battery module 101 are L , N R is as follows: n=2 m=n+1=3 N L =9 N R =3 The battery module 101 is divided into a first section 51 to a fourth section 54 by first sections S11 and S12 and second sections S21 to S23. Two adjacent sections among the first section 51 to the fourth section 54 share one battery row R3, R6, and R9 at the boundary between them. Each of the first section 51 to the fourth section 54 has a cell number N in the X direction. x and the number of cells in the Y direction, N y (=Number of cells in battery string R N R ) and the same number of square parts (here N x =N y =N R=3). A structure in which the number and arrangement of the first and second regions and cells are set to satisfy this relationship is called the "first structure." In the first structure, the total number of cells and the total number of regions are optimized so that current can be passed through the multiple square regions.

[0067] The battery module having the first structure is not limited to the example shown in Fig. 8. The number of first portions n, the number of second portions m, the number of cells N in the battery block L L and the number of cells in the battery string R, N R The first structure can be realized by setting the following relationship: m=n+1 N L ≧2, N R ≧2 N L =(2×N R -1)+2×(n-1)×(N R -1)

[0068] ·Second structure 9 is a schematic top view illustrating another arrangement of battery modules. The number of first sections n, the number of second sections m, and the number of cells N L , N R is as follows: n=1 m=n+1=2 N L =8 N R =4 In the battery module 102, the number of cells N L is an even number, and the first region S11 is disposed on the first surface between the two central battery strings R4 and R5 (in other words, corresponding to two cells). The first region S11 and the second regions S21 and S22 divide the first region 51 into a first portion 51 and a second portion 52. The first region 51 includes the battery string R4, and the second region 52 includes the battery string R5. Each of the first region 51 and the second region 52 has a cell number N in the X direction. x and the number of cells in the Y direction, N y and are the same number of square parts (here N x =Ny =N R =4). This structure is called the "second structure." According to the second structure, two adjacent portions 51 and 52 do not overlap, so that it is possible to prevent a part of the current from flowing to a different portion.

[0069] The battery module having the second structure is not limited to the example shown in Fig. 9. The number of first portions n, the number of second portions m, and the number of cells N in the battery block L are L and the number of cells in the battery string R, N R The second structure can be realized by setting it so that the following relationship is satisfied: m=n+1 N L ≧2, N R ≧2 N L =(2×N R )+2×(n-1)×(N R -1)

[0070] ·Third structure 10 is a schematic top view showing another battery module. The number of first sections n, the number of second sections m, and the number of cells N L , N R is as follows: n=1 m=n+1=2 N L =8 N R =5

[0071] In the battery module 103, as in the second structure, the number of cells N L is an even number, and the first region S11 is disposed between the two central battery strings R4 and R5. In the battery module 103, each of the divided portions 51 and 52 has a cell number N in the X direction. x is the number of cells in the Y direction, N y is one square less than (here N x =N y(-1=4). However, if the two battery strings R4 and R5 are divided into multiple sections 51a and 52a so as to share them, the number of cells in the X direction and the number of cells in the Y direction in each section 51a and 52a will be the same. This structure is called the "third structure." The third structure can further reduce the difference in current density in the X direction between each section 51 and 52.

[0072] The battery module having the third structure is not limited to the example shown in Fig. 10. The number of first portions n, the number of second portions m, and the number of cells N in the battery block L are L and the number of cells in the battery string R, N R The third structure can be realized by setting it so that the following relationship is satisfied: m=n+1 N L ≧2, N R ≧2 N L =2×(N R -1)×n

[0073] (d) Number of cells N in battery block L L and the number of cells in the battery string R, N R Range When n=1 When n=1 and m=2, the number of cells in battery block L is N L is the number of cells in the battery string R (here, the number of battery blocks L) N R It may be more than (N R ≦N L ) This ensures the benefits of dividing the battery into multiple parts. On the other hand, if the number of cells in the battery block L is N, L is 3×(N R -1) or less (N L ≦3×(N R -1)). 3×(N R -1) or less, the difference in current density occurring in the X direction can be made smaller in each of the divided parts. L , N R may be set to satisfy the following relationship: N R <N L <3×(NR -1) More preferably, the number of cells N L , N R is set to have any one of the first to third structures described above.

[0074] When n≧2 When n ≥ 2 and m = n + 1, the number of cells in battery block L is N L and the number of cells in the battery string R, N R (Here, the number of battery blocks L) may satisfy the following relationship when n=k+2 (k is an integer equal to or greater than 0). (2×N R -1)+(2×k+1)×(N R -1)≦N L This reduces the number of cells N R For the number of cells N L Therefore, the effect of dividing the current into two or more parts can be more reliably obtained. On the other hand, the number of cells N in the battery block L L may satisfy the following relationship: N L ≦(2×k+5)×(N R -1) This makes it possible to further reduce the difference in current density in the X direction in each of the divided portions. L , N R may be set to satisfy the following relationship: (2×N R -1)+(2×k+1)×(N R -1) <N L <(2×k+5)×(N R -1) More preferably, the number of cells N L , N R is set to have any one of the first to third structures described above.

[0075] When n=2 and m=3, k=0. Therefore, the number of cells in this case is N L , N R may be set to satisfy the following equation: 3×NR -2≦N L ≦5×(N R -1)

[0076] Second Embodiment 11 is a schematic perspective view of a battery unit according to a second embodiment of the present invention. The battery unit 200 includes a stack in which a plurality of battery units according to the above-described embodiments are connected in series, a case 80 that covers the stack, and a first external terminal 81 and a second external terminal 82. The case 80 has, for example, a rectangular parallelepiped shape that is elongated in the X direction. The first external terminal 81 and the second external terminal 82 are disposed, for example, on the front surface 200e of the case 80.

[0077] Figures 12A and 12B are diagrams showing the stack in the battery unit of Figure 11. Figure 12A is a schematic perspective view of the battery unit of Figure 11 with a protective structure such as a case removed, viewed obliquely from above, and Figure 12B is a schematic perspective view of the battery unit of Figure 12, viewed obliquely from above from the rear side.

[0078] 12A and 12B, the battery unit 200 includes two battery modules 100A and 100B connected in series, a first terminal t1, and a second terminal t2. The first terminal t1 and the second terminal t2 are electrically connected to a first external terminal 81 and a second external terminal 82, respectively. The battery unit 200 may further include bus bars 61 and 62 and tab connections (tab joints) 71 and 72.

[0079] The battery modules 100A and 100B have the same structure as the battery module 100 described in the first embodiment with reference to FIGS. 1A to 2. In the battery module 100A, the first portion S11 is arranged on the side tab 41 on the battery block L1 side, and the second portions S21 and S22 are arranged on the side tab 42 on the battery block L8 side. That is, the side surface on the battery block L1 side is the first surface f1, and the side surface on the battery block L8 side is the second surface f2. In the battery module 100B, the second portions S21 and S22 are arranged on the side tab 41, and the first portion S11 is arranged on the side tab 42. That is, the side surface on the battery block L1 side is the second surface f2, and the side surface on the battery block L8 side is the first surface f1.

[0080] The battery modules 100A and 100B are stacked in the Z direction. In the illustrated example, the battery module 100A is stacked on the battery module 100B via an insulator so that the surface 100b (see FIG. 1A, etc.) of the battery module 100A faces the surface 100b (see FIG. 1A, etc.) of the battery module 100B. The battery unit 200 has a first unit surface 200c and a second unit surface 200d facing the first unit surface 200c. The first surfaces f1 of the battery modules 100A and 100B are located on the first unit surface 200c side, and the second surfaces f2 are located on the second unit surface 200d side.

[0081] The first portion S11 of the battery module 100A is electrically connected to a first terminal portion (e.g., a negative terminal portion) t1. The first portion S11 of the battery module 100B is electrically connected to a second terminal portion (e.g., a positive terminal portion) t2. The second portions S21 and S22 of the battery module 100A are electrically connected to the second portions S21 and S22 of the battery module 100B, respectively.

[0082] The bus bars 61 and 62 are disposed, for example, on the first unit surface 200c. The bus bar (also referred to as the "first bus bar") 61 is electrically connected to the first portion S11 of the battery module 100A. In the illustrated example, the bus bar 61 is connected only to the first portion S11 of the side tab 41 of the battery module 100A. A space or an insulator may be interposed between the bus bar 61 and other portions of the side tab 41. The bus bar (also referred to as the "second bus bar") 62 is electrically connected to the first portion S11 of the battery module 100B. In the illustrated example, the bus bar 62 is connected only to the first portion S11 of the side tab 42 of the battery module 100B. A space or an insulator may be interposed between the bus bar 62 and other portions of the side tab 42. The use of the bus bars 61 and 62 facilitates electrical connection between desired portions of the cell terminal connection portion and the terminal portions t1 and t2. This electrical connection can prevent the structure of the battery unit 200 from becoming complicated and the size from increasing.

[0083] In the illustrated example, the bus bar 61 is disposed on the side tab 41 of the battery module 100A on the first unit surface 200c. The bus bar 61 extends in the X direction, and one end of the bus bar 61 is electrically connected to the first portion S11 of the battery module 100A, and the other end may function as the first terminal t1 of the battery unit 200. Similarly, the bus bar 62 is disposed on the side tab 42 of the battery module 100B on the first unit surface 200c. The bus bar 62 extends in the X direction, and one end of the bus bar 62 is electrically connected to the first portion S11 of the battery module 100B, and the other end may function as the second terminal t2 of the battery unit 200.

[0084] The method of connecting the side tabs 41, 42 and the bus bars 61, 62 is not limited to the illustrated example. In the illustrated example, when viewed from the Y direction, the bus bar 61 is arranged so as to overlap a portion of the side tab 41 of the battery module 100A, and the bus bar 61 is connected only to the first portion S11 of the side tab 41. Note that a pair of bus bars may be arranged to sandwich the side tab 41, and the pair of bus bars may be connected to the first portion S11 of the side tab 41 but not to other portions of the side tab 41. Similarly, a pair of bus bars may be arranged to sandwich the side tab 42 of the battery module 100B. Furthermore, as illustrated in FIG. 13 , each battery module 100A, 100B may have another cell tab 38 instead of the side tabs 41, 42 that connect the cells 10 in parallel in the battery blocks L1, L8. In this case, the cell tab 38 may be electrically connected to the corresponding bus bar (here, the bus bar 61) via a bonding wire 63.

[0085] The tab connection portions 71 and 72 are disposed, for example, on the second unit surface 200d. The tab connection portion (also referred to as the "first tab connection portion") 71 electrically connects the second portion S21 of the battery module 100A to the second portion S21 of the battery module 100B. The tab connection portion 72 electrically connects the second portion S22 of the battery module 100A to the second portion S22 of the battery module 100B. In the example shown in FIG. 12B , the tab connection portion 71 extends in the Z direction to connect the left end of the side tab 42 of the battery module 100A to the left end of the side tab 41 of the battery module 100B. The tab connection portion (also referred to as the "second tab connection portion") 72 extends in the Z direction to connect the right end of the side tab 42 of the battery module 100A to the right end of the side tab 41 of the battery module 100B. The use of the tab connections 71 and 72 facilitates electrical connection between desired locations of the cell terminal connections of the battery modules 100A and 100B, and prevents the structure of the battery unit 200 from becoming complicated or increasing in size due to this electrical connection.

[0086] The bus bars 61, 62 and the tab connection portions 71, 72 may be plate-shaped bodies made of an electrically conductive material such as a metal, for example, copper, a copper alloy, an aluminum alloy, etc. For example, tough pitch copper with a copper content of 99.9% or more may be used.

[0087] In the illustrated example, the first portion S11 of the battery modules 100A and 100B is electrically connected to the first terminal t1 and the second terminal t2, but the second portions S21 and S22 may be electrically connected to the first terminal t1 and the second terminal t2. For example, the first portions S11 of the battery modules 100A and 100B may be electrically connected to each other via a tab connection portion, and the second portions S21 and S22 may be electrically connected to the terminal portions via bus bars.

[0088] FIG. 12B shows the shortest current paths p11 to p14 in the battery unit 200. As an example, when the battery unit 200 is discharging, current flows from the outside into the first portion S11 of the battery module 100A via the first terminal (negative terminal) t1. In the battery module 100A, the current flows from the first portion S11 to the second portions S21 and S22. Then, the current flows from the second portions S21 and S22 of the battery module 100A via the tab connections 71 and 72 to the second portions S21 and S22 of the battery module 100B. In the battery module 100B, the current flows from the second portions S21 and S22 to the first portion S11 and then flows out from the first portion S11 to the outside via the second terminal (positive terminal) t2. In this way, in the battery module 100A, the first portion S11 is the portion into which current flows, whereas in the battery module 100B, the second portions S21 and S22 are the portions into which current flows.

[0089] The number of battery modules constituting the battery unit of this embodiment is not particularly limited, and the battery unit may have a structure in which three or more battery modules are stacked in the Z direction.

[0090] According to this embodiment, by connecting two battery modules 100A and 100B in series, the total number of battery blocks connected in series doubles, thereby increasing the output voltage. As an example, if the nominal voltage of the cell 10 is 3.2 V, the battery unit 200 can output 51.2 V (= 3.2 V × 16).

[0091] Furthermore, according to this embodiment, it is possible to reduce bias in the current flow in each of the battery modules 100A, 100B constituting the battery unit 200, thereby extending the life of the battery unit 200. Furthermore, by stacking the battery modules 100A, 100B in the Z direction perpendicular to the cell arrangement plane (XY plane), corresponding portions of the battery modules 100A, 100B can be electrically connected on one side (here, the second unit surface 200d) of the battery unit 200. Such a battery unit 200 can be suitably applied, for example, to applications where a battery unit with small widths in the X and Y directions is desired.

[0092] In the illustrated example, each of the second regions S21, S22 of the battery module 100A is connected to a corresponding one of the second regions S21, S22 of the battery module 100B, thereby enabling the battery modules 100A, 100B to be connected in series without complicating the structure of the battery unit 200. Specifically, the second regions S21, S22 of the battery modules 100A, 100B can be electrically connected to each other using the same number of tab connections 71, 72 as the number of second regions. In this embodiment, the number of first regions (here, one) of each battery module 100A, 100B is smaller than the number of second regions, allowing the first region S11 to be electrically connected to the corresponding terminals t1, t2 with a simpler structure and process.

[0093] The structures of the battery modules 100A and 100B that make up the battery unit of this embodiment are not limited to the structures shown in FIGS. 12A and 12B. The number n of the first parts and the number m of the second parts in the battery modules 100A and 100B can be set as appropriate. For example, as the battery modules 100A and 100B, other battery modules 101 to 103 illustrated in FIGS. 8 to 10 may be used.

[0094] It is preferable that the number n of the first parts is less than the number m of the second parts (n < m). On the spot, the first parts of each of the battery modules 100A and 100B may be electrically connected to the terminal part via a bus bar, and the second parts with a larger number may be used for the connection between the battery modules 100A and 100B. Thereby, without complicating the structure of the battery unit 200, the bias of the current in each of the battery modules 100A and 100B can be reduced. As an example, when arranging n first parts and m (n < m) second parts in each of the battery modules 100A and 100B, the n first parts of the battery module 100A may be electrically connected to the first terminal part t1 via, for example, a bus bar 61, and the n first parts of the battery module 100B may be electrically connected to the second terminal part t2 via, for example, a bus bar 62. On the second unit surface r200d, m tab connection parts may be arranged at intervals in the X direction. Each tab connection part electrically connects one of the second parts of the battery module 100A to a corresponding one of the second parts of the battery module 100B.

[0095] <Modification Example> FIG. 14 is a schematic perspective view of the battery unit of the modification example. In the battery unit 201 of the modification example, a plurality of (here, two) battery modules 100A and 100B are arranged adjacent to each other in a plan view from the Z direction. The battery modules 100A and 100B may be arranged parallel or substantially parallel to each other in a plan view from the Z direction.

[0096] In the battery unit 201 shown in FIG. 14, the battery modules 100A and 100B are arranged adjacent to each other so that the second surfaces f2 of the battery modules 100A and 100B face each other. The first portions S11 of the battery modules 100A and 100B are electrically connected to corresponding terminal portions, for example, via bus bars. Each second portion of the battery module 100A is electrically connected to a corresponding second portion of the battery module 100B by tab connections 71 and 72. The tab connections 71 and 72 may be bonding wires or plate-shaped connections.

[0097] The direction, orientation, and connection method of the battery modules 100AB, 100B adjacent to each other are not limited to the example shown in Fig. 14. Furthermore, the structure of the battery modules 100A, 100B, the number of battery modules connected in series, and the arrangement direction are not limited to the example shown in Fig. 14.

[0098] According to this modification, the height (length along the Z direction) can be made smaller than that of the battery unit 200 illustrated in Figures 12A and 12B. Therefore, the battery unit 201 of this modification can be suitably applied to applications where a battery unit that is small (thin) and wide is desired, for example.

[0099] Any of the various embodiments and modifications may be combined as appropriate to achieve the effects of each of them.

[0100] Although the present invention has been fully described in connection with the preferred embodiment with reference to the accompanying drawings, various changes and modifications will become apparent to those skilled in the art, and it is to be understood that such changes and modifications are included within the scope of the present invention as defined by the appended claims unless they depart therefrom.

[0101] The above description can also be expressed as follows.

[0102] The battery module of the first aspect comprises: A battery module including a plurality of battery blocks in which a plurality of battery cells are connected in parallel, The plurality of battery blocks are arranged in a first direction, In each of the plurality of battery blocks, the plurality of battery cells are arranged in a second direction that intersects with the first direction, each of the plurality of battery cells is connected in series to a corresponding battery cell in a battery block adjacent in the first direction; The battery module includes: a first surface on which a first portion through which a current flows in or out between the outside and the battery module is disposed; a second surface facing the first surface, on which two second portions through which the current flows in or out between the outside and the battery module are disposed; In the second direction, the first portion is located between the two second portions.

[0103] The battery module of the second aspect is In the battery module of the first aspect, a first tab that connects in parallel the plurality of battery cells included in a battery block that is closest to the first surface among the plurality of battery blocks; a second tab that connects in parallel the plurality of battery cells included in a battery block that is closest to the second surface among the plurality of battery blocks, the first portion is disposed on the first tab; one of the two second portions is disposed on one end side of the second tab in the second direction, The other of the two second portions is disposed on the other end side of the second tab in the second direction.

[0104] The battery module of the third aspect is In the battery module of the first or second aspect, In the second direction, the first portion is located in the center or approximately the center between the two second portions.

[0105] In a fourth aspect, the battery module includes: In the battery module according to any one of the first to third aspects, At least two of the first regions are disposed on the first surface; At least three of the second regions are arranged on the second surface; In the second direction, one of the at least two first regions is located between each of two adjacent second regions among the at least three second regions.

[0106] The battery module of the fifth aspect is In the battery module of the fourth aspect, At least three of the second regions are arranged at equal or approximately equal intervals in the second direction.

[0107] The battery module of the sixth aspect is In the battery module of any one of the first to fifth aspects, The number m of the second portions arranged on the second surface is greater than the number n of the first portions arranged on the first surface.

[0108] The battery module of the seventh aspect is In the battery module of the sixth aspect, n=1, m=2, The number of the plurality of battery blocks is N R , the number of battery cells in each of the plurality of battery blocks is N L Then, N R ≦N L ≦3×(N R -1) is.

[0109] The battery module of the eighth aspect is In the battery module of the sixth aspect, n=2, m=3, The number of the plurality of battery blocks is N R , the number of battery cells in each of the plurality of battery blocks is N L Then, 3×N R -2≦N L ≦5×(N R -1) is.

[0110] The battery unit of the ninth aspect is A battery unit including a first battery module and a second battery module connected in series, each of the first battery module and the second battery module is the battery module according to any one of the first to eighth aspects; Each of the two second portions of the first battery module is electrically connected to a corresponding one of the two second portions of the second battery module.

[0111] The battery unit of the tenth aspect is In the battery unit of the ninth aspect, The first battery module and the second battery module are stacked in a third direction perpendicular to the first direction and the second direction.

[0112] The battery unit of the eleventh aspect is In the battery unit of the ninth aspect, The first battery module and the second battery module are arranged adjacent to each other in a plan view from a third direction orthogonal to the first direction and the second direction.

[0113] The battery unit of the twelfth aspect is In the battery unit of the ninth or tenth aspect, The battery unit includes: a first tab connection portion that electrically connects one of the two second portions of the first battery module and one of the two second portions of the second battery module; a second tab connection portion that electrically connects the other of the two second portions of the first battery module and the other of the two second portions of the second battery module; a first bus bar electrically connected to the first portion of the first battery module; The battery module further includes a second bus bar electrically connected to the first portion of the second battery module. [Industrial Applicability]

[0114] The battery module according to the present invention can further reduce bias in current among a plurality of battery cells, and is therefore useful as a battery module for various applications such as power storage and automobiles. It can be applied to applications. [Explanation of symbols]

[0115] 10 Battery Cells 30 Cell terminal connection 30a 1st area 30b 2nd area 31~37 Cell tabs 41, 42 Side tabs 51 Part 1 52 Part 2 53 Part 3 54 Part 4 61, 62 Busbars 63 Bonding Wire 71, 72 Tab connection 100, 101-103, 100A, 100B battery modules 100a top surface 100b bottom side 100c, 100d side 200, 201 Battery Unit 200c 1st unit side 200d 2nd unit surface f1 First face f2 Second face Ir current (current flowing between cells in the same battery string R) Iw Wrong-direction current (current flowing between cells in different battery strings R) L, L1~L8 battery blocks p1~p4, p11~p14, q Shortest path of current R, R1~R15 battery row S1, S11, S12 First part S2, S21, S22, S23 Second region

Claims

1. A battery module including a plurality of battery blocks in which a plurality of battery cells are connected in parallel, The plurality of battery blocks are arranged in a first direction, In each of the plurality of battery blocks, the plurality of battery cells are arranged in a second direction that intersects with the first direction, each of the plurality of battery cells is connected in series to a corresponding battery cell in a battery block adjacent in the first direction; The battery module includes: a first surface on which a first portion through which a current flows in or out between the outside and the battery module is disposed; a second surface facing the first surface, on which two second portions through which the current flows in or out between the outside and the battery module are disposed; The battery module, wherein the first portion is located between the two second portions in the second direction.

2. a first tab that connects in parallel the plurality of battery cells included in a battery block that is closest to the first surface among the plurality of battery blocks; a second tab that connects in parallel the plurality of battery cells included in a battery block that is closest to the second surface among the plurality of battery blocks, the first portion is disposed on the first tab; one of the two second portions is disposed on one end side of the second tab in the second direction; The battery module according to claim 1 , wherein the other of the two second portions is disposed on the other end side of the second tab in the second direction.

3. The battery module according to claim 1 , wherein the first portion is located at a center or approximately a center between the two second portions in the second direction.

4. At least two of the first portions are arranged on the first surface, At least three of the second regions are arranged on the second surface; 3. The battery module according to claim 1, wherein one of the at least two first regions is located between each of two adjacent second regions among the at least three second regions in the second direction.

5. The battery module according to claim 4 , wherein at least three of the second portions are arranged at equal or approximately equal intervals in the second direction.

6. The battery module according to claim 1 , wherein the number m of the second portions arranged on the second surface is greater than the number n of the first portions arranged on the first surface.

7. n=1, m=2, The number of the plurality of battery blocks is N Ｒ , the number of battery cells in each of the plurality of battery blocks is N Ｌ Then, N Ｒ ≦N Ｌ ≦3×(N Ｒ -1) The battery module according to claim 6 ,

8. n=2, m=3, The number of the plurality of battery blocks is N Ｒ , the number of battery cells in each of the plurality of battery blocks is N Ｌ Then, 3×N Ｒ -2≦N Ｌ ≦5×(N Ｒ -1) The battery module according to claim 6 ,

9. A battery unit including a first battery module and a second battery module connected in series, each of the first battery module and the second battery module is the battery module according to claim 1 or 2; a battery unit, wherein each of the two second portions of the first battery module is electrically connected to a corresponding one of the two second portions of the second battery module;

10. The battery unit according to claim 9 , wherein the first battery module and the second battery module are stacked in a third direction perpendicular to the first direction and the second direction.

11. The battery unit according to claim 9 , wherein the first battery module and the second battery module are arranged adjacent to each other in a plan view from a third direction orthogonal to the first direction and the second direction.

12. The battery unit includes: a first tab connection portion that electrically connects one of the two second portions of the first battery module and one of the two second portions of the second battery module; a second tab connection portion electrically connecting the other of the two second portions of the first battery module and the other of the two second portions of the second battery module; a first bus bar electrically connected to the first portion of the first battery module; The battery unit according to claim 9 , further comprising: a second bus bar electrically connected to the first portion of the second battery module.

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