Secondary battery and battery pack

Abstract

To provide a secondary battery in which a problem in the conventional art is solved.SOLUTION: A secondary battery according to the present disclosure includes: a flat electrode body including a first electrode plate, a second electrode plate having a polarity different from that of the first electrode plate, and a separator disposed between the first electrode plate and the second electrode plate; and a case that accommodates the electrode body. The electrode body has a first main surface and a second main surface disposed to face each other. The first main surface has a pair of first end sides disposed to face each other. The secondary battery according to the present disclosure includes a first spacer part disposed along one of the pair of first end sides, and a second spacer part disposed along the other of the pair of first end sides. An area where the first spacer part and the second spacer part are not disposed exists between the first spacer part and the second spacer part.SELECTED DRAWING: Figure 6

Description

[Technical Field]

[0001] The present disclosure relates to a secondary battery and also to a battery pack using a plurality of such secondary batteries. [Background technology]

[0002] One known configuration of a secondary battery is one in which a flat electrode body is housed in a battery case (see, for example, Patent Document 1). Patent Document 1 describes the construction of a battery pack using a plurality of such secondary batteries. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 4537353 Summary of the Invention [Problem to be solved by the invention]

[0004] When constructing a battery pack using secondary batteries having flat-shaped electrode assemblies, one method involves arranging and restraining multiple secondary batteries with inter-cell separators between adjacent secondary batteries. This restraint allows pressure to be applied to the battery cases of the secondary batteries via the inter-cell separators. When the battery case is pressurized, the center of the battery case is more likely to deform than the edges, so the pressure load is greater at the center of the electrode assembly than at the edges. This creates a difference in resistance between the edges and the center of the electrode assembly, resulting in the problem of lithium precipitation being more likely at the edges of the electrode assembly where the pressure load is smaller.

[0005] Therefore, the present disclosure provides a secondary battery that solves the problems of the conventional technology. [Means for solving the problem]

[0006] The secondary battery of the present disclosure includes a flat electrode assembly including a first electrode plate, a second electrode plate having a polarity opposite to that of the first electrode plate, and a separator disposed between the first and second electrode plates, and a case that houses the electrode assembly. The electrode assembly has a first main surface and a second main surface that are disposed opposite each other. The first main surface has a pair of first end sides that are disposed opposite each other. The secondary battery of the present disclosure includes a first spacer portion that is disposed along one of the pair of first end sides, and a second spacer portion that is disposed along the other of the pair of first end sides. Between the first spacer portion and the second spacer portion, there is a region where the first spacer portion and the second spacer portion are not disposed.

[0007] According to this configuration, it is possible to provide a secondary battery that solves the problems of the conventional technology, that is, according to this configuration, it is possible to provide a secondary battery in which lithium deposition is suppressed when assembled into a battery pack. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a perspective view schematically illustrating a secondary battery according to an embodiment of an example of a secondary battery of the present disclosure. [Figure 2] FIG. 2 is a perspective view of the secondary battery of FIG. 1 turned upside down. [Figure 3] FIG. 3 is a schematic diagram of the internal structure of the secondary battery of FIG. [Figure 4] FIG. 4 is a perspective view of the secondary battery of FIG. 1, showing a schematic perspective view of the case body. [Figure 5] FIG. 5 is a cross-sectional view that schematically shows a secondary battery according to the prior art to which a restraining load is applied. [Figure 6] FIG. 6 is a cross-sectional view schematically showing the secondary battery of FIG. 1 to which a restraining load is applied. [Figure 7] FIG. 7 is a schematic diagram for explaining a case where the first spacer portion and the second spacer portion are formed by a separator of the electrode assembly. [Figure 8]FIG. 8 is a schematic diagram of the internal structure of a secondary battery which is a modification of the secondary battery of FIG. 1 and further includes a third spacer portion and a fourth spacer portion. [Figure 9] FIG. 9 is a schematic cross-sectional view showing the state of each secondary battery in a battery pack using the secondary battery of FIG. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. Matters not mentioned in this specification but necessary for implementing the present disclosure can be understood as design matters for a person skilled in the art based on the prior art in the relevant field. The present disclosure can be implemented based on the contents disclosed in this specification and the common general technical knowledge in the relevant field. In the following drawings, components and parts that perform the same function are denoted by the same reference numerals. Dimensional relationships (length, width, thickness, etc.) in each drawing do not reflect actual dimensional relationships. In this specification, a numerical range expressed as "A to B" includes A and B.

[0010] In this specification, the term "secondary battery" refers to an electricity storage device that can be repeatedly charged and discharged. In addition, in this specification, the term "lithium ion secondary battery" refers to a secondary battery that uses lithium ions as charge carriers and achieves charging and discharging by the transfer of charge associated with the lithium ions between the positive and negative electrodes.

[0011] FIG. 1 is a perspective view of a secondary battery 100 according to this embodiment, which is an example of a secondary battery according to the present disclosure. FIG. 2 is a perspective view of the secondary battery 100 of FIG. 1 turned upside down. FIG. 3 is a schematic view of the internal structure of the secondary battery 100 of FIG. 1, specifically, a state in which the long side surfaces of the battery case and the insulating film have been removed. In the following description, the symbols L, R, F, Rr, U, and D in the drawings represent left, right, front, rear, top, and bottom, and the symbols X, Y, and Z in the drawings represent the short side direction of the secondary battery 100, the long side direction perpendicular to the short side direction, and the up-down direction perpendicular to the short side direction and the long side direction, respectively.

[0012] It should be noted that U (top) and D (bottom) in the drawings correspond to the top and bottom of the secondary battery 100 in a normal usage state (particularly when installed in an automotive battery), but the usage state of the secondary battery 100 is not limited to this. For example, in other embodiments, the secondary battery 100 may be installed upside down.

[0013] The secondary battery 100 according to this embodiment is a lithium-ion secondary battery. This allows the secondary battery 100 to have excellent battery characteristics such as high energy density and high capacity. However, in other embodiments, the secondary battery may be a secondary battery other than a lithium-ion secondary battery (e.g., a sodium-ion secondary battery, etc.).

[0014] 1 to 3, the secondary battery 100 includes a battery case 10, an electrode assembly 20, and an electrolyte (not shown). The secondary battery 100 also includes a positive electrode terminal 30, a negative electrode terminal 40, and an insulating sheet 50.

[0015] <Battery case> The battery case 10 is a housing that houses the electrode assembly 20 and an electrolyte. In this embodiment, the electrode assembly 20 has a flat shape. Therefore, as shown in FIGS. 1 and 2, the battery case 10 has a flat, bottomed, rectangular parallelepiped outer shape corresponding to the flat shape of the electrode assembly 20. Therefore, the battery case 10 is rectangular (particularly flat rectangular). Therefore, the secondary battery 100 in the illustrated example is a rectangular lithium-ion secondary battery. The rectangular shape of the battery case 10 improves space efficiency when a battery pack is constructed using multiple secondary batteries 100.

[0016] The material of the battery case 10 is not particularly limited and may be the same as those conventionally used (e.g., metal, resin, etc.). From the viewpoints of strength, thermal conductivity, etc., the material of the battery case 10 is preferably metal, more preferably aluminum, an aluminum alloy, iron, or an iron alloy, and even more preferably aluminum or an aluminum alloy.

[0017] As shown in FIGS. 1 to 3, the battery case 10 includes a case body 12, a first sealing plate 14, and a second sealing plate 16. The case body 12 is rectangular tubular. As shown in FIG. 3, the case body 12 has a first opening 12e at one end and a second opening 12f at the other end. The first sealing plate 14 seals the first opening 12e, and the second sealing plate 16 seals the second opening 12f. The battery case 10 is integrated by joining (e.g., welding) the first sealing plate 14 and the second sealing plate 16 to the case body 12 at the first opening 12e and the second opening 12f, respectively. The battery case 10 is hermetically sealed. Therefore, the secondary battery 100 is a sealed battery.

[0018] As shown in FIG. 1 , the case body 12 includes a substantially rectangular bottom surface 12a, a pair of opposing long side surfaces 12b extending from the long sides of the bottom surface 12a, and a top surface 12c connecting the upper ends of the pair of long side surfaces 12b. The top surface 12c is substantially rectangular. The top surface 12c faces the bottom surface 12a. The area of the long side surface 12b is preferably larger than the area of the bottom surface 12a and larger than the area of the top surface 12c. For example, the bottom surface 12a and the top surface 12c can form a pair of short side surfaces. The case body 12 is formed, for example, by bending a single metal plate into a cylindrical shape and joining the seams (e.g., welding). In the illustrated example, a welded joint 12d is located on the top surface 12c. The welded joint 12d may be located on either the bottom surface 12a or the long side surface 12b.

[0019] As shown in FIG. 2 , a gas release valve 13 is provided on the bottom surface 12a of the case body 12. The gas release valve 13 is configured to break when the pressure inside the battery case 10 reaches a predetermined value or higher, thereby releasing gas inside the battery case 10 to the outside. While the present embodiment includes one gas release valve 13, the number of gas release valves 13 may be two or more. Although the present embodiment includes the gas release valve 13 on the bottom surface 12a, the present embodiment is not limited to this. In other embodiments, the gas release valve 13 may be provided on a surface other than the bottom surface 12a, such as the long side surface 12b, the top surface 12c, or the sealing plate 14. Alternatively, in other embodiments, the secondary battery 100 may be installed upside down relative to the drawing, with the bottom surface 12a replaced by the top surface 12c, and the gas release valve facing upward. The area of the gas release valve 13 is optional.

[0020] In this embodiment, the gas release valve 13 is a cross-shaped notch, but the shape of the gas release valve 13 is not particularly limited. In other embodiments, the gas release valve 13 may be, for example, a linear notch (only vertical or horizontal lines), or may be a conventionally known oval valve (with an internal notch) or circular valve (with an internal notch). The dimensions of the notch (e.g., length, depth, etc.) are arbitrary and can be determined appropriately taking into consideration, for example, the pressure resistance of the battery case 10.

[0021] The first sealing plate 14 and the second sealing plate 16 are plate-like members that seal the first opening 12e and the second opening 12f of the case body 12. The first sealing plate 14 and the second sealing plate 16 are substantially rectangular in plan view.

[0022] A liquid inlet 17 is provided in the first sealing plate 14. The liquid inlet 17 is used to inject an electrolyte into the battery case 10 after the first sealing plate 14 and the second sealing plate 16 are assembled to the case body 12. The liquid inlet 17 is provided below the positive electrode terminal 30, but the position at which the liquid inlet 17 is provided in the first sealing plate 14 is not limited to this. The liquid inlet 17 is sealed with a sealing member 18 after the electrolyte is injected. Note that, although the liquid inlet 17 is provided in the first sealing plate 14 in this embodiment, the liquid inlet 17 may be provided in the second sealing plate 16 or the case body 12. Furthermore, although the liquid inlet 17 is provided on a different surface from the gas release valve 13 in this embodiment, the liquid inlet 17 may be provided on the same surface as the gas release valve 13.

[0023] <Electrode terminal> The positive electrode terminal 30 and the negative electrode terminal 40 are each fixed to the battery case 10. Here, the positive electrode terminal 30 and the negative electrode terminal 40 are each fixed to opposing surfaces of the battery case 10. More specifically, the positive electrode terminal 30 is attached to the first sealing plate 14, and the negative electrode terminal 40 is attached to the second sealing plate 16.

[0024] Specifically, the first sealing plate 14 and the second sealing plate 16 have through holes, and insulating members 63, 64 (see FIG. 4 ) are attached to the through holes, respectively. The positive electrode terminal 30 is attached to the first sealing plate 14 via the insulating member 63, and is insulated from the first sealing plate 14. The negative electrode terminal 40 is attached to the second sealing plate 16 via the insulating member 64, and is insulated from the second sealing plate 16. The insulating member 63 also insulates the first sealing plate 14 from the electrode assembly 20 inside the battery case 10. The insulating member 64 also insulates the second sealing plate 16 from the electrode assembly 20 inside the battery case 10.

[0025] In the present embodiment, the positive electrode terminal 30 and the negative electrode terminal 40 are provided on the first sealing plate 14 and the second sealing plate 16, respectively; however, the arrangement of the positive electrode terminal 30 and the negative electrode terminal 40 is not limited to this. In other embodiments, both the positive electrode terminal 30 and the negative electrode terminal 40 may be provided on one of the first sealing plate 14 or the second sealing plate 16. The first sealing plate 14 and the second sealing plate 16 may be provided on the case body 12. In the present embodiment, the positive electrode terminal 30 and the negative electrode terminal 40 are provided on a different surface from the gas release valve 13; however, the positive electrode terminal 30 and the negative electrode terminal 40 may be provided on the same surface as the gas release valve 13.

[0026] However, when the positive electrode terminal 30 and the negative electrode terminal 40 are provided on the first sealing plate 14 and the second sealing plate 16, respectively, as in the present embodiment, the height of the secondary battery 100 (i.e., the dimension in the Z direction in the drawing) can be reduced, making it easier to obtain a battery with a high volumetric energy density. In this case, it is also easier to construct a battery module with a high volumetric energy density, particularly for in-vehicle applications.

[0027] The positive electrode terminal 30 and the negative electrode terminal 40 are exposed on the outer surfaces of the first sealing plate 14 and the second sealing plate 16, respectively. Here, the positive electrode terminal 30 and the negative electrode terminal 40 are arranged on an axis that extends in the long side direction Y and passes through the center of the first sealing plate 14 and the second sealing plate 16. However, in other embodiments, the axis may be offset from the center of the first sealing plate 14 and the second sealing plate 16, for example, in the short side direction X. Furthermore, the positive electrode terminal 30 and the negative electrode terminal 40 do not have to be arranged on the axis. For example, one of the positive electrode terminal 30 and the negative electrode terminal 40 may be offset to one side in the short side direction X, and the other may be offset to the other side in the short side direction X.

[0028] The positive electrode terminal 30 is preferably made of a metal, more preferably aluminum or an aluminum alloy, and the negative electrode terminal 40 is preferably made of a metal, more preferably copper or a copper alloy.

[0029] The electrode body 20 has, at one end, a positive electrode current collecting tab electrically connected to the positive electrode 23, and the positive electrode current collecting tabs are gathered and attached to a positive electrode current collecting member 32. The electrode body 20 has, at the other end, a negative electrode current collecting tab electrically connected to the negative electrode 24, and the negative electrode current collecting tabs are gathered and attached to a negative electrode current collecting member 42. Inside the battery case 10, the positive electrode current collecting member 32 is attached to the first sealing plate 14 and electrically connected to the positive electrode terminal 30. Inside the battery case 10, the negative electrode current collecting member 42 is attached to the second sealing plate 16 and electrically connected to the negative electrode terminal 40.

[0030] In this way, the positive electrode terminal 30 is electrically connected to the positive electrode 23 of the electrode assembly 20 inside the battery case 10 via the positive electrode current collecting tab and the positive electrode current collecting member 32. The negative electrode terminal 40 is electrically connected to the negative electrode 24 of the electrode assembly 20 inside the battery case 10 via the negative electrode current collecting tab and the negative electrode current collecting member 42. Note that the structure for electrically connecting the positive electrode terminal 30 and the negative electrode terminal 40 to the positive electrode 23 and the negative electrode 24 of the electrode assembly 20, respectively, is not limited to that shown in the figure.

[0031] <Electrode body> The electrode body 20 is housed inside the battery case 10. Fig. 3 schematically shows the state in which the long side surface of the battery case 10 and the insulating film 50 have been removed to facilitate understanding of the configuration of the electrode body 20. Fig. 4 is a perspective view of the secondary battery 100, showing a schematic view through the case body 12.

[0032] As shown in FIG. 4, the electrode body 20 is placed inside the battery case 10 while being covered with an insulating sheet 50, which will be described later. In this embodiment, a plurality of electrode bodies 20 are housed inside one battery case 10. In the example shown in FIG. 4, two electrode bodies 20 are housed inside one battery case 10. When there are a plurality of electrode bodies 20 in this manner, a flow path for the electrolyte solution and generated gas can be formed between an electrode body 20 and an adjacent electrode body 20. The number of electrode bodies 20 housed inside one battery case 10 is not particularly limited. In other embodiments, the number of electrode bodies 20 housed inside one battery case 10 may be three or more, or may be one.

[0033] The electrode assembly 20 includes a positive electrode 23 (positive electrode plate 23) as a first electrode plate, a negative electrode 24 (negative electrode plate 24) as a second electrode plate having a polarity different from that of the first electrode plate, and a separator 25 disposed therebetween. The separator 25 (see FIG. 7) is disposed between the positive electrode 23 and the negative electrode 24, thereby insulating the positive electrode 23 from the negative electrode 24. In another embodiment, the first electrode plate may be configured as the negative electrode 24, and the second electrode plate may be configured as the positive electrode 23.

[0034] In this embodiment, the electrode body 20 has a flat shape. The electrode body 20 may have the same configuration as a known electrode body having a flat shape. The electrode body 20 may be a wound electrode body or a stacked electrode body. When the electrode body 20 is a wound electrode body, for example, a long positive electrode 23 and a long negative electrode 24 are stacked with two separators 25 interposed therebetween and wound in the electrode body 20. When the electrode body 20 is a stacked electrode body, for example, a plurality of positive electrodes 23, a plurality of electrodes 24, and a plurality of separators 25 are stacked in the electrode body 20 such that each separator 25 is interposed between each positive electrode 23 and each negative electrode 24. Alternatively, when the electrode body 20 is a laminated electrode body, for example, in the electrode body 20, a plurality of positive electrodes 23, a plurality of electrodes 24, and one long separator 25 are laminated while the separator 25 is folded zigzag so that the separator 25 is interposed between each positive electrode 23 and each negative electrode 24. In this case, the manufacturing efficiency of the laminated electrode body is improved.

[0035] In the electrode body 20, in the electrode laminate structure of the positive electrode 23 and the negative electrode 24, it is preferable that both outermost layers are the negative electrode 24. In this case, lithium contained in the positive electrode active material of the positive electrode 23 can be fully utilized, and deposition of lithium in the negative electrode 24 can be highly prevented.

[0036] The electrode body 20 has a flat shape and therefore has a pair of flat surfaces. The flat surfaces are the largest surfaces (i.e., main surfaces) of the electrode body 20. Therefore, the electrode body 20 has a pair of main surfaces (i.e., a first main surface 20a and a second main surface 20b) that face each other.

[0037] When the electrode body 20 is a wound electrode body, the wound electrode body has a flat portion and a pair of rounded portions at both ends of the flat portion. The first main surface 20a and the second main surface 20b are the outermost surfaces of the flat portion. When the electrode body 20 is a stacked electrode body, the first main surface 20a and the second main surface 20b are the outermost surfaces in the stacking direction of the positive electrode 23 and the negative electrode 24.

[0038] In this embodiment, the first main surface 20a faces the battery case 10. Specifically, the first main surface 20a faces one of the long side surfaces 12b of the case body 12 of the battery case 10. As shown in FIG. 3, the first main surface 20a has a pair of first end sides 20c arranged opposite to each other and a pair of second end sides 20d arranged opposite to each other. The second end sides 20d are approximately perpendicular to the first end sides 20c. In the illustrated example, the first main surface 20a is approximately rectangular having a pair of long sides and a pair of short sides. However, the first main surface 20a may also be approximately square.

[0039] The ratio of the length of the first end side 20c to the length of the second end side 20d (i.e., the aspect ratio of the first main surface 20a) is not particularly limited. If the height of the secondary battery 100 (i.e., the dimension in the Z direction in the drawing) is small, it becomes easier to obtain a battery with a high volumetric energy density, so the ratio is preferably 2 or more.

[0040] In this embodiment, the first end edge 20c is a long side of the first main surface 20a, and the second end edge 20d is a short side of the first main surface 20a. Note that in other embodiments, the first end edge 20c may be a short side of the first main surface 20a, and the second end edge 20d may be a long side of the first main surface 20a. Because the area pressed by the first spacer portion 71 and the second spacer portion 72 described below is larger, it is preferable that the first end edge 20c be a long side of the first main surface 20a, as in this embodiment.

[0041] <Spacer part> 3 and 4, the secondary battery 100 according to this embodiment includes a first spacer portion 71 and a second spacer portion 72. The first spacer portion 71 is disposed along one of the pair of first end sides 20c (here, the side on the top surface 12c side of the battery case 10). The second spacer portion 72 is disposed along the other of the pair of first end sides 20c (here, the side on the bottom surface 12a side of the battery case 10). Thus, the first spacer portion 71 and the second spacer portion 72 are disposed so as to face each other at both ends in the extension direction of the second end side 20d of the first main surface 20a of the electrode body 20 (i.e., the extension direction of the short side, the Z direction in the drawings).

[0042] In this embodiment, the first spacer portion 71 and the second spacer portion 72 are arranged apart from each other. Therefore, there is a region between the first spacer portion 71 and the second spacer portion 72 where the first spacer portion 71 and the second spacer portion 72 are not arranged. This region is the center of the first main surface 20a of the electrode body 20 in the extension direction of the second end side 20d.

[0043] The first spacer portion 71 and the second spacer portion 72 function as pressure propagation portions when the secondary battery 100 according to this embodiment is used as a battery pack and a constraint load is applied. This will be explained in detail using the drawings. FIG. 5 is a cross-sectional view schematically showing a secondary battery 700 according to the related art to which a constraint load is applied. FIG. 6 is a cross-sectional view schematically showing the secondary battery 100 according to this embodiment to which a constraint load is applied.

[0044] As shown in FIG. 5 , in a conventional case where a secondary battery 700 is used as a battery pack, an inter-cell separator 780 is disposed on the outer surface of a battery case 710. When a restraining load is applied to the secondary battery 700, the inter-cell separator 780 presses the battery case 710. At this time, the central portion of the battery case 710 is more likely to deform than the ends, and a recess having a trapezoidal cross section is formed in the battery case 710. As a result, a gap is generated between the end of the electrode assembly 720 and the battery case 710, and a load is no longer applied to the end of the electrode assembly 720. As a result, a difference in resistance occurs between the end of the electrode assembly 720 and the central portion of the electrode assembly, and lithium is more likely to precipitate at the end of the electrode assembly 720, where the pressure load is smaller.

[0045] Therefore, in this embodiment, unlike the prior art, the secondary battery 100 has a first spacer portion 71 and a second spacer portion 72, as shown in Figures 3, 4, and 6. The first spacer portion 71 and the second spacer portion 72 are arranged on the first main surface 20a of the electrode body 20, and therefore, as shown in Figure 6, the first spacer portion 71 and the second spacer portion 72 protrude from the first main surface 20a toward the battery case 10.

[0046] Therefore, when a restraint load is applied to the secondary battery 100, the inter-cell separator 180 is pressed against the battery case 10, and a recess having a trapezoidal cross section is formed in the battery case 10. In this case, the first spacer portion 71 and the second spacer portion 72 can fill the gap between the end of the electrode assembly 20 and the battery case 10. Furthermore, the first spacer portion 71 and the second spacer portion 72 can transmit the load received from the battery case 10 to the end of the electrode assembly 20.

[0047] This reduces the difference in load between the end and center of the electrode body 20. As a result, the difference in resistance between the end and center of the electrode body 20 can be reduced, thereby suppressing lithium deposition when the electrode body 20 is assembled into a battery.

[0048] In the illustrated example, the first spacer portion 71 and the second spacer portion 72 are configured as separate members from the electrode body 20. However, the first spacer portion 71 and the second spacer portion 72 may be configured as components of the electrode body 20. In other words, the first spacer portion 71 and the second spacer portion 72 may be formed by components of the electrode body 20.

[0049] First, a case will be described in which the first spacer portion 71 and the second spacer portion 72 are configured as separate members from the electrode body 20. The constituent material of the first spacer portion 71 and the second spacer portion 72 is preferably resin. As the resin, a resin having a suitable elasticity such as polyethylene or polypropylene is preferable. The first spacer portion 71 and the second spacer portion 72 may be a resin tape or a cut resin sheet.

[0050] The first spacer portion 71 and the second spacer portion 72 are disposed between the electrode assembly 20 and the battery case 10. The first spacer portion 71 and the second spacer portion 72 are preferably fixed within the secondary battery 100, and the manner of fixing is not particularly limited. As one example, the first spacer portion 71 and the second spacer portion 72 are fixed to the electrode assembly 20. As another example, the first spacer portion 71 and the second spacer portion 72 are fixed to the inner surface of the battery case 10. As yet another example, the first spacer portion 71 and the second spacer portion 72 are fixed to the insulating film 50. As yet another example, a resin member is disposed on the end of the electrode assembly 20 in the direction in which the first end side 10c extends. The first spacer portion 71 and the second spacer portion 72 are fixed to the resin member. The resin member is, for example, a resin member for insulating the electrode assembly 20 from the first sealing plate 14 and the second sealing plate 16. The resin member is, for example, a resin spacer, an electrode body holder, the above-mentioned insulating member 63 and insulating member 64, etc., and is preferably a resin spacer. In this further example, it is easy to stably arrange the first spacer portion 71 and the second spacer portion 72 in predetermined positions, and the effects of the present disclosure can be further enhanced.

[0051] The first spacer portion 71 and the second spacer portion 72 can be fixed by, for example, attaching with tape, bonding with an adhesive, welding (for example, heat welding, ultrasonic welding), or the like.

[0052] Next, a description will be given of a case where the first spacer portion 71 and the second spacer portion 72 are configured as components of the electrode assembly 20. In this case, as an example, the first spacer portion 71 and the second spacer portion 72 are formed by the separator 25 that configures the electrode assembly 20. This is shown schematically in FIG.

[0053] In the example shown in Fig. 7, the electrode assembly 20 is a laminated electrode assembly, in which negative electrodes 24 and positive electrodes 23 are alternately laminated. A single long separator 25 is alternately folded back at the end of the negative electrode 24 and the end of the positive electrode 23 (i.e., folded zigzag). Note that, because Fig. 7 is a schematic diagram, the main surface of the positive electrode 23 and the separator 25 are depicted as being separated, and the main surface of the negative electrode 24 and the separator 25 are depicted as being separated. This is for ease of visual recognition of each component; in reality, the main surface of the positive electrode 23 and the separator 25 are in contact, and the main surface of the negative electrode 24 and the separator 25 are in contact.

[0054] The long separator 25 has a portion that is not laminated with the positive electrode 23 and the negative electrode 24 (in other words, an excess portion that is not used to insulate the positive electrode 23 and the negative electrode 24). This portion is folded at a pair of first end sides 20c of the first main surface 20a of the electrode body 20 to form a first spacer portion 71 and a second spacer portion 72. Therefore, the first spacer portion 71 and the second spacer portion 72 are each part of the separator 25. With this configuration, the first spacer portion 71 and the second spacer portion 72 can be stably disposed at predetermined positions on the first main surface 20a.

[0055] In particular, when the electrode body 20 is configured as a laminated electrode body and a single long separator 25 is used by folding it zigzag, it is easy to form the first spacer portion 71 and the second spacer portion 72 using a part of the separator 25.

[0056] In this embodiment, the shapes of the first spacer portion 71 and the second spacer portion 72 are not particularly limited. In the example shown in FIG. 6 , the cross-sectional shapes of the first spacer portion 71 and the second spacer portion 72 are triangular. Therefore, the first spacer portion 71 and the second spacer portion 72 are inclined so that their thickness decreases toward the center of the electrode assembly 20. In other embodiments, the cross-sectional shapes of the first spacer portion 71 and the second spacer portion 72 may be rectangular. Even if the cross-sectional shapes of the first spacer portion 71 and the second spacer portion 72 are other than triangular, as long as a portion of the first spacer portion 71 and the second spacer portion 72 contacts the battery case 10, the restraint load when the secondary battery 100 is assembled into a battery pack can be transmitted to the end of the electrode assembly 20. Furthermore, by deforming the first spacer portion 71 and the second spacer portion 72, the gap between the battery case 10 and the electrode assembly 20 can be efficiently filled, thereby efficiently transmitting pressure. However, it is advantageous for the first spacer portion 71 and the second spacer portion 72 to have a portion that is inclined so that the thickness decreases toward the center of the electrode body 20 in order to transmit the restraint load when the secondary battery 100 is assembled into a battery to the ends of the electrode body 20. Therefore, it is advantageous for the cross-sectional shape of the first spacer portion 71 and the second spacer portion 72 to be triangular or trapezoidal.

[0057] In this embodiment, the dimensions of the first spacer portion 71 and the second spacer portion 72 are not particularly limited, and it is preferable to select dimensions that fill the gap between the battery case 10 and the end of the electrode body 20 that occurs when the secondary battery 100 is assembled into a battery pack. In this case, the dimensions may be selected taking into consideration deformation of the first spacer portion 71 and the second spacer portion 72.

[0058] The maximum thickness of the first spacer portion 71 and the second spacer portion 72 is preferably 0.5 mm or more. The maximum thickness of the first spacer portion 71 and the second spacer portion 72 is preferably 2.5 mm or less, and more preferably 1.5 mm or less. The thickness of the first spacer portion 71 and the second spacer portion 72 refers to the dimension in the stacking direction of the electrode body 20 (i.e., the direction perpendicular to the first main surface 20a of the electrode body 20, the X direction in the drawing).

[0059] When the first spacer portion 71 and the second spacer portion 72 are inclined toward the center of the electrode body 20 (for example, when the cross-sectional shape of the first spacer portion 71 and the second spacer portion 72 is triangular), the thickness of the first spacer portion 71 and the second spacer portion 72 at the end portion toward the center of the electrode body 20 is preferably 0.5 mm or less, and more preferably 0.1 mm or less.

[0060] The dimension of the first main surface 20a in the direction perpendicular to the first end side 20c (i.e., the length of the second end side 20d of the first main surface 20a) is defined as L1. The width of the first spacer portions 71 and the second spacer portions 72 (i.e., the length in the direction perpendicular to the first end side 20c) is defined as L2. The width L2 of the first spacer portions 71 and the second spacer portions 72 is preferably 1 / 10 or more, and more preferably 1 / 8 or more, of the dimension L1. On the other hand, the width L2 of the first spacer portions 71 and the second spacer portions 72 is preferably 1 / 4 or less of the dimension L1.

[0061] The distance from the bottom surface 12a to the top surface 12c of the battery case 10 in a direction perpendicular to the first edge 20c is defined as L3. The distance from the end of the first spacer portion 71 on the side closer to the center of the electrode assembly 20 to the top surface 12c and the distance from the end of the second spacer portion 72 on the side closer to the center of the electrode assembly 20 to the bottom surface 12a are defined as L4. Therefore, L4 is the distance from the end of the spacer portion on the side closer to the center of the electrode assembly 20 to the nearest inner surface of the battery case 10 in a direction perpendicular to the first edge 20c. This distance L4 is preferably at least 1 / 10 of the distance L3, and more preferably at least 1 / 8 of the distance L3. The distance L4 is preferably at most 1 / 4 of the distance L3.

[0062] In this embodiment, the first main surface 20a of the electrode body 20 has a pair of first end sides 20c and a pair of second end sides 20d. First spacer portions 71 and second spacer portions 72 are provided on the pair of first end sides 20c, but no spacer portions are provided on the pair of second end sides 20d.

[0063] Therefore, a modified example of the secondary battery according to this embodiment is shown in FIG. 8 . In the example shown in FIG. 8 , the secondary battery 200 further includes a third spacer portion 73 and a fourth spacer portion 74 in addition to a first spacer portion 71 and a second spacer portion 72. Specifically, the secondary battery 200 includes a third spacer portion 73 arranged along one of the pair of second end sides 20d and a fourth spacer portion 74 arranged along the other of the pair of second end sides 20d. The third spacer portion 73 and the fourth spacer portion 74 are spaced apart in the direction in which the first end side 20c extends. Therefore, between the third spacer portion 73 and the fourth spacer portion 74, there is a region in which the first spacer portion 71, the second spacer portion 72, the third spacer portion 73, and the fourth spacer portion 74 are not arranged. In this case, the difference in resistance between the end portion of the electrode body 20 and the center portion of the electrode body 20 can be further reduced, thereby further suppressing lithium deposition.

[0064] 8, the first spacer 71, the second spacer 72, the third spacer 73, and the fourth spacer 74 are connected to each other to form a rectangular frame. However, the first spacer 71, the second spacer 72, the third spacer 73, and the fourth spacer 74 do not have to be connected to each other.

[0065] In the secondary battery 100 according to this embodiment, the first spacer portions 71 and the second spacer portions 72 are provided only on the first main surface 20a of the electrode assembly 20. However, the first spacer portions 71 and the second spacer portions 72 may also be provided on the second main surface 20b. In particular, when the secondary battery 100 has only one electrode assembly 20, it is advantageous to provide the first spacer portions 71 and the second spacer portions 72 on both the first main surface 20a and the second main surface 20b in order to further suppress lithium deposition when assembled into a battery pack. Furthermore, when the secondary battery 100 has a plurality of electrode assemblies 20, it is preferable that the above-described first spacer portions 71 and second spacer portions be provided on each of the main surfaces of the electrode assembly 20 that face the battery case 10.

[0066] Next, the materials constituting the positive electrode 23, negative electrode 24, and separator 25 will be described. The positive electrode 23 typically has a positive electrode current collector and a positive electrode active material layer fixed to at least one surface of the positive electrode current collector. The positive electrode current collector is made of a conductive metal such as aluminum, an aluminum alloy, nickel, or stainless steel. Here, the positive electrode current collector is a metal foil, specifically an aluminum foil. In this embodiment, the positive electrode 23 has an exposed portion of the positive electrode current collector without forming a positive electrode active material layer, and this exposed portion constitutes a current collecting tab. However, the method of forming the current collecting tab is not limited to this.

[0067] The positive electrode active material layer contains a positive electrode active material capable of reversibly absorbing and releasing charge carriers. The positive electrode active material is preferably an oxide containing at least one of Ni, Co, and Mn, and examples thereof include lithium transition metal composite oxides such as lithium cobalt oxide, lithium manganese oxide, lithium nickel oxide, lithium nickel manganese composite oxide, and lithium nickel cobalt manganese composite oxide. The positive electrode active material is more preferably a lithium composite oxide containing Ni (in other words, a Ni-containing lithium composite oxide). In the Ni-containing lithium composite oxide, the Ni content is preferably in the range of 70 to 100 mol% relative to the total number of moles of metals other than Li. In the lithium transition metal composite oxide, a portion of Ni, Co, and Mn may be substituted with Al, Ti, Zr, P, B, Si, Nb, C, or the like. Furthermore, the positive electrode active material may be a lithium transition metal composite oxide whose particle surfaces are coated with a compound containing Al, Ti, Zr, W, P, B, Si, Nb, C, or the like. The total amount of substitution and addition is about 0.1 to 7 mass %. Alternatively, a lithium transition metal phosphate compound such as lithium iron phosphate can also be used as the positive electrode active material. The positive electrode active material layer may contain a conductive material, a binder, and the like. The conductive material is preferably a carbon material such as carbon black or carbon nanotubes. The binder is preferably a resin binder such as polyvinylidene fluoride.

[0068] The negative electrode 24 typically includes a negative electrode current collector and a negative electrode active material layer fixed to at least one surface of the negative electrode current collector. The negative electrode current collector is made of a conductive metal such as copper, a copper alloy, nickel, or stainless steel. The negative electrode current collector is a metal foil, specifically a copper foil. In this embodiment, the negative electrode 24 has an exposed portion of the negative electrode current collector without forming a negative electrode active material layer, and this exposed portion constitutes a current collecting tab. However, the method for forming the current collecting tab is not limited to this.

[0069] The negative electrode active material layer contains a negative electrode active material capable of reversibly absorbing and releasing charge carriers. Examples of the negative electrode active material include carbon-based negative electrode active materials such as graphite, hard carbon, and soft carbon; Si-based negative electrode active materials such as silicon and silicon oxide; silicon-carbon composite negative electrode active materials; and Sn-based negative electrode active materials such as Sn. The negative electrode active material layer may contain a conductive material, a thickener, a binder, and the like. Preferably, the binder contains styrene butadiene rubber, carboxymethyl cellulose, or the like.

[0070] The area of the main surface of the negative electrode active material layer is preferably larger than the area of the main surface of the positive electrode active material layer, which makes it possible to highly effectively prevent deposition of lithium in the negative electrode 24.

[0071] The separator 25 is a member that insulates the positive electrode active material layer from the negative electrode active material layer. A porous resin sheet made of a polyolefin resin such as polyethylene (PE) or polypropylene (PP) is suitable as the separator 25. The porous resin sheet may have a single-layer structure or a multi-layer structure (e.g., a three-layer structure of PP / PE / PP).

[0072] An adhesive layer is preferably provided on the surface of the separator 25. The adhesive layer contains an adhesive resin such as an acrylic resin or polyvinylidene fluoride. When the separator 25 has an adhesive layer, it is easy to prevent the separator 25 and the electrodes from being misaligned when stacked. The adhesive layer may be provided on the entire surface of the separator 25, or may be coated in a pattern.

[0073] A heat-resistant layer (HRL) containing ceramic particles may be provided on the surface of the separator 25. Examples of materials for the ceramic particles include alumina, boehmite, aluminum hydroxide, and titania. The heat-resistant layer preferably further contains a resin binder. The resin binder may be an adhesive resin such as an acrylic resin or polyvinylidene fluoride. By adding an appropriate amount of resin binder to the heat-resistant layer, the heat-resistant layer can also function as an adhesive layer.

[0074] In one embodiment of separator 25, separator 25 comprises a porous resin sheet substrate and adhesive layers on both sides of the substrate. In another embodiment of separator 25, separator 25 comprises a porous resin sheet substrate, an adhesive layer on one side of the substrate, and a heat-resistant layer on the other side of the substrate. In this embodiment, the heat-resistant layer may also function as an adhesive layer. In yet another embodiment of separator 25, separator 25 comprises a porous resin sheet substrate, an adhesive layer on one side of the substrate, and a heat-resistant layer on the other side of the substrate, with an adhesive layer further provided on the heat-resistant layer.

[0075] <Insulation sheet> As shown in Fig. 4, the insulating sheet 50 is housed inside the battery case 10 together with the electrode assembly 20. The insulating sheet 50 is disposed between the battery case 10 and the electrode assembly 20. The insulating sheet 50 covers the periphery of the electrode assembly 20. It is preferable that the insulating sheet 50 covers at least the first main surface 20a, the second main surface 20b, the side surface facing the bottom surface 12a of the battery case 10, and the side surface facing the top surface 12c of the battery case 10 of the electrode assembly 20.

[0076] The insulating sheet 50 is made of an insulating material, preferably a resin. Examples of resins include olefin-based resins such as polyethylene (PE), polypropylene (PP), and polymethylpentene (PMP / TPX™); polyester-based resins such as polyethylene terephthalate (PET) and polyethylene naphthalate (PEN); acrylic resin (PMMA); polyimide (PI); polyphenylene ether (PPE); triacetate (TAC); polyphenylene sulfide resin (PPS); polycarbonate (PC); nylon; and fluororesins such as polytetrafluoroethylene (PTFE). Of these, PE and PP are preferred. The insulating sheet 50 may be porous or non-porous.

[0077] In this embodiment, the insulating sheet 50 is made of a single sheet-like member. The insulating sheet 50 is formed by folding this sheet-like member into a rectangular tube shape to match the shape of the electrode assembly 20. However, the configuration of the insulating sheet 50 is not limited to this, and it may be box-shaped, bag-shaped, or the like. The insulating sheet 50 preferably has an area through which the electrolyte and gas can pass. This area through which the electrolyte and gas can pass is preferably located on the side of the bottom surface 12a of the case body 12 of the battery case 10. In this case, the electrolyte can easily permeate the electrode assembly 20. This area through which the electrolyte and gas can pass is preferably located opposite the bottom surface 12a of the case body 12, which has the gas release valve 13. In this case, gas generated in the electrode assembly 20 can easily be released by the gas release valve 13.

[0078] <Electrolyte> The electrolyte solution is accommodated inside the battery case 10 together with the electrode assembly 20. The electrolyte solution may be the same as that used in general secondary batteries and is not particularly limited. The electrolyte solution is typically a non-aqueous liquid electrolyte (i.e., non-aqueous electrolyte solution) containing a non-aqueous solvent and a supporting salt. The non-aqueous solvent contains, for example, carbonates such as ethylene carbonate (EC), ethyl methyl carbonate (EMC), and dimethyl carbonate (DMC). The non-aqueous solvent is preferably a mixture of EC, EMC, and DMC in a range of 1 to 99% by volume, with the total ratio being 100% by volume. The non-aqueous solvent may further contain a carboxylic acid ester such as methyl acetate. The supporting salt is also called an electrolyte salt and is, for example, a fluorine-containing lithium salt. Examples of fluorine-containing lithium salts include LiPF6, LiBF4, and lithium bis(fluorosulfonyl)imide (LiFSI). The supporting salt preferably contains LiPF6. The concentration of the supporting electrolyte is not particularly limited, but is preferably 0.6 to 1.8 mol / L, and more preferably 0.7 mol / L to 1.3 mol / L. The electrolyte may further contain additives, specifically, for example, film-forming agents such as vinylene carbonate (VC) and oxalate complexes; gas generating agents; thickeners; etc.

[0079] The secondary battery 100 according to this embodiment can be used for various purposes. Suitable applications include in-vehicle applications, specifically as a driving power source mounted on vehicles such as electric vehicles (BEVs), hybrid electric vehicles (HEVs), and plug-in hybrid electric vehicles (PHEVs). The secondary battery 100 can also be used as a storage battery for small-sized power storage devices.

[0080] The secondary battery 100 according to this embodiment can suppress lithium deposition when used in a battery pack. Hereinafter, a battery pack using the secondary battery 100 according to this embodiment will be described.

[0081] <Battery pack> The battery pack according to this embodiment includes a plurality of secondary batteries 100. The plurality of secondary batteries 100 are arranged in a predetermined direction with inter-cell separators disposed between adjacent secondary batteries 100. A restraining load is applied to the plurality of secondary batteries 100 by a restraining member. The plurality of secondary batteries 100 are electrically connected in series and / or parallel.

[0082] The state of each secondary battery 100 in the battery pack according to this embodiment is shown in Fig. 9. Fig. 9 is a schematic cross-sectional view showing the state of each secondary battery 100 in a battery pack 300 that uses the secondary batteries 100. Note that five lined up black squares in Fig. 9 indicate that the illustrated structure is repeated. Therefore, although two secondary batteries 100 are shown in Fig. 9, two or more (for example, 10 to 100) secondary batteries are used in the battery pack 300.

[0083] The case 10 of the secondary battery 100 has a first wall portion 10a facing the first main surface 20a of the electrode body 20. The first wall portion 10a is a wall portion of the battery case 10 having a long side surface 12b (see FIGS. 1 and 2).

[0084] Because the center of the battery case 10a is more susceptible to deformation than the ends, the area of the portion of the inter-cell separator 180 that presses against the first wall portion 10a is smaller than the area of the first wall portion 10a. This makes it possible to suppress deformation and fatigue failure due to excessive pressure on the battery case 10. Therefore, the area of the surface of the inter-cell separator 180 that faces the first wall portion 10a may be smaller than the area of the first wall portion 10a.

[0085] In the inter-cell separator 180, the area of the region where its thickness is greatest is preferably smaller than the area of the electrode assembly 20 (specifically, the area of the first main surface 20a of the electrode assembly 20). This enhances the effects of the first spacer portions 71 and second spacer portions 72, improving the space efficiency of the secondary battery 100. As described above, the portion of the first wall portion 10a of the battery case 10 that faces the outer periphery of the first main surface 20a of the electrode assembly 20 is less likely to deform, and the first wall portion 10a has a recess whose cross section is trapezoidal when pressurized. In this case, the cross section of the inter-cell separator 180 can be made trapezoidal, and the shape of the inter-cell separator 180 can be adapted to the shape of the trapezoidal recess of the first wall portion 10a of the battery case 10.

[0086] In the direction perpendicular to the first main surface 20a of the electrode body 20, the distance between the center of the first main surface 20a and the first wall 10a during the above-described pressurization is smaller than the distance between the outer periphery of the first main surface 20a and the first wall 10a. As described above, the first spacer 71 and the second spacer 72 are arranged so as to fill the outer periphery between the first main surface 20a and the first wall 10a of the electrode body 20. This forms a recessed shape due to the first main surface 20a, the first spacer 71, and the second spacer 72, which can fit into the trapezoidal recessed shape of the first wall 10a of the battery case 10. In other words, the first wall 10a of the battery case 10 presses the electrode body 20, the first spacer 71, and the second spacer 72.

[0087] In this embodiment, the inter-cell separator 180 has an elastic layer 182 and a heat-resistant layer 184. The elastic layer 182 is formed on both sides of the heat-resistant layer 184. When the inter-cell separator 180 has the elastic layer 182, the elastic layer 182 can easily follow the deformation of the first wall portion 10a of the battery case 10 due to the restraining load, which is advantageous from the viewpoint of applying the load evenly to the electrode assembly 20. In addition, even if expansion and contraction occur due to the charge and discharge of the secondary battery 100, the secondary battery 100 can be more firmly fixed, which is advantageous.

[0088] The elastic layer 182 is preferably a layer containing an elastomer. Examples of elastomers include rubber and thermoplastic elastomers. The rubber may be natural rubber or synthetic rubber. The thickness of the elastic layer 182 is not particularly limited, but is preferably 0.5 mm or more, more preferably 0.8 mm or more, and even more preferably 1.0 mm or more. The heat-resistant layer 184 contains, for example, a ceramic material.

[0089] Inter-cell separator 180 is not limited to the above and may have any known configuration, and may therefore be a single member made of an elastic material (especially an elastomer).

[0090] In the illustrated example, the secondary battery 100 has a second wall 10b facing the first wall 10a of the battery case 10, which has the same configuration as the first wall 10a. Therefore, the secondary battery 100 has spacers facing the first spacer 71 and the second spacer 72 on the second wall 10b side. This configuration is advantageous in that it allows the electrode body to be firmly fixed.

[0091] In a battery pack having the above configuration, lithium deposition is suppressed, and each secondary battery can be firmly fixed, resulting in a highly reliable battery pack.

[0092] Although specific examples of the present disclosure have been described in detail above, these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and alterations of the specific examples exemplified above.

[0093] That is, the secondary battery and the battery pack of the present disclosure are as follows: [1] to [7]. [1] A flat electrode assembly including a first electrode plate, a second electrode plate having a polarity different from that of the first electrode plate, and a separator disposed between the first electrode plate and the second electrode plate; a case for accommodating the electrode assembly; A secondary battery comprising: the electrode body has a first main surface and a second main surface arranged to face each other, the first main surface has a pair of first end sides arranged to face each other, a first spacer portion disposed along one of the pair of first end sides, and a second spacer portion disposed along the other of the pair of first end sides, a region where the first spacer portion and the second spacer portion are not disposed exists between the first spacer portion and the second spacer portion; Secondary battery. [2] The first main surface has a pair of second end sides arranged to face each other, The secondary battery described in item [1] includes a third spacer portion arranged along one of the pair of second end sides, and a fourth spacer portion arranged along the other of the pair of second end sides. [3] A resin member is disposed on an end of the electrode body in a direction in which the first end side extends, The secondary battery according to item [1] or [2], wherein the first spacer portion and the second spacer portion are fixed to the resin member. [4] The secondary battery according to item [1] or [2], wherein the first spacer portion and the second spacer portion are each a part of the separator. [5] A battery pack including a plurality of secondary batteries according to any one of items [1] to [4], the case has a first wall portion facing the first main surface of the electrode body, In a direction perpendicular to the first main surface, a distance between a central portion of the first main surface and the first wall portion is smaller than a distance between an outer periphery of the first main surface and the first wall portion; an inter-cell separator is disposed between the secondary batteries; In the battery pack, the area of the portion of the inter-cell separator that presses against the first wall portion is smaller than the area of the first wall portion. [6] The battery pack according to item [5], wherein the inter-cell separator includes an elastic layer. [7] The battery pack according to item [5] or [6], wherein the area of the inter-cell separator where the thickness is greatest is smaller than the area of the electrode assembly. [Explanation of symbols]

[0094] 10 Battery case 12 Case body 12a Bottom 13 Gas exhaust valve 14 1st sealing plate 16 Second sealing plate 20 Electrode body 23 Positive electrode 24 Negative electrode 25 Separator 50 Insulation Sheet 71 First spacer part 72 Second spacer part 100 Secondary battery

Claims

1. a flat electrode assembly including a first electrode plate, a second electrode plate having a polarity different from that of the first electrode plate, and a separator disposed between the first electrode plate and the second electrode plate; a case for accommodating the electrode assembly; A secondary battery comprising: the electrode body has a first main surface and a second main surface arranged to face each other, the first main surface has a pair of first end sides arranged to face each other, a first spacer portion disposed along one of the pair of first end sides, and a second spacer portion disposed along the other of the pair of first end sides, a region where the first spacer portion and the second spacer portion are not disposed exists between the first spacer portion and the second spacer portion; Secondary battery.

2. the first main surface has a pair of second end sides arranged to face each other, The secondary battery according to claim 1 , further comprising: a third spacer portion disposed along one of the pair of second end sides; and a fourth spacer portion disposed along the other of the pair of second end sides.

3. a resin member is disposed on an end of the electrode body in a direction in which the first end side extends; The secondary battery according to claim 1 , wherein the first spacer portion and the second spacer portion are fixed to the resin member.

4. The secondary battery according to claim 1 , wherein the first spacer portion and the second spacer portion are each a part of the separator.

5. A battery pack including a plurality of secondary batteries according to claim 1, the case has a first wall portion facing the first main surface of the electrode body, In a direction perpendicular to the first main surface, a distance between a central portion of the first main surface and the first wall portion is smaller than a distance between an outer periphery of the first main surface and the first wall portion, an inter-cell separator is disposed between the secondary batteries; an area of the portion of the inter-cell separator that presses against the first wall portion is smaller than an area of the first wall portion.

6. The battery pack of claim 5 , wherein the inter-cell separator includes an elastic layer.

7. 6. The battery pack according to claim 5, wherein the area of the inter-cell separator where the thickness is greatest is smaller than the area of the electrode assembly.

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