JP2016171020A - Battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a battery capable of suppressing damage to an electrode body when being dropped.SOLUTION: A battery (100) comprises an electrode body (2) and a battery case (1). The electrode body (2) includes a positive electrode (21), a negative electrode (22), and a separator (23). The separator (23) is arranged between the positive electrode (21) and the negative electrode (22). The battery case (1) houses the electrode body (2). The battery case (1) includes a flat cylindrical sidewall part (11), a bottom (12), and a salient (13). The bottom (12) blocks one end of the sidewall part (11) in an axial direction. The salient (13) protrudes from an inner surface (121) of the bottom (12), and supports the electrode body (2).SELECTED DRAWING: Figure 2

Description

  The present invention relates to a battery.

  In recent years, mobile devices with relatively large power consumption, such as large-screen smartphones and tablets, have been spreading. In connection with this, the request | requirement of the capacity increase and enlargement of a battery is increasing.

  A battery having a large capacity or a large size receives a large impact when dropped. Therefore, about such a battery, the response | compatibility to the problem which arises by the impact at the time of dropping is examined.

  For example, Patent Document 1 discloses a prismatic battery in which a cutout portion or a groove is provided in a side surface portion of an outer can. The battery outer can is deformed from the notch or the groove when the impact due to dropping is received at the corner. Thereby, the distortion part which arises in an armored can by the impact of a fall becomes small. As a result, the amount by which the distorted portion crushes the electrode body in the outer can is reduced, and an internal short circuit is less likely to occur.

JP 2014-127375 A

  In the battery of Patent Document 1, a distorted portion generated in the outer can by a drop impact can be reduced. However, in the battery, since the electrode body is disposed close to the inner surface of the outer can, interference between the distorted portion and the electrode body may occur even when the distorted portion is not large. Therefore, there is a high possibility that the electrode body is damaged by the fall of the battery.

  This invention makes it a subject to provide the battery which can suppress generation | occurrence | production of the damage of the electrode body at the time of fall.

  The battery according to the present disclosure includes an electrode body and a battery case. The electrode body includes a positive electrode, a negative electrode, and a separator. The separator is disposed between the positive electrode and the negative electrode. The battery case houses the electrode body. The battery case includes a flat cylindrical side wall portion, a bottom portion, and a convex portion. The bottom portion seals one end of the side wall portion in the axial direction. The convex portion protrudes from the inner surface of the bottom portion. The convex portion supports the electrode body (first configuration).

  According to the first configuration, since the electrode body is supported by the convex portion provided on the inner surface of the bottom portion of the battery case, the electrode body is disposed at a position away from the bottom portion in the battery case. For this reason, when a battery falls from the corner | angular part of a battery case which a bottom part and a side wall part make, and the corner | angular part of a battery case deform | transforms, it is hard to produce interference with a battery case and an electrode body. Therefore, it is possible to suppress the occurrence of damage to the electrode body when the battery is dropped.

  The said convex part may be arrange | positioned in the center of the inner surface of a bottom part (2nd structure).

  According to the 2nd structure, a convex part is arrange | positioned away from the corner | angular part of a battery case. For this reason, when the said corner | angular part deform | transforms by the fall of a battery, it can prevent that the deformed corner | angular part and a convex part interfere.

  The surface of the convex portion may have a curved surface shape (third configuration).

  According to the 3rd structure, since a convex part and an electrode body surface-contact, when a battery falls, the force which acts on an electrode body from a convex part can be disperse | distributed. Therefore, the positive electrode, the negative electrode, and the separator included in the electrode body are hardly displaced, and the occurrence of damage to the electrode body can be suppressed.

  The side wall portion may have an axial dimension larger than a dimension perpendicular to the axial direction (fourth configuration).

  According to the fourth configuration, the side wall portion of the battery case has a relatively large dimension in the axial direction. Therefore, when a battery falls from the corner | angular part of a battery case, the angle of the surface and side wall part which the battery collided becomes larger than 45 degrees, and bigger force than a bottom part acts on a side wall part. Thereby, a big deformation | transformation may arise in the part near a bottom part among side wall parts. Even in such a case, the convex portion provided at the bottom of the battery case exhibits a high effect. That is, the convex portion separates the electrode body from the bottom portion in the battery case. For this reason, even if it is a case where the part near a bottom part among a side wall part deform | transforms greatly, interference with a battery case and an electrode body does not arise easily, and generation | occurrence | production of an electrode body can be suppressed effectively.

  According to the battery according to the present disclosure, it is possible to suppress the occurrence of damage to the electrode body at the time of dropping.

FIG. 1 is a perspective view schematically showing a battery according to the embodiment. 2 is a cross-sectional view of the battery shown in FIG. 1 taken along the line II-II. 3 is a vertical partial cross-sectional view in the thickness direction of the battery shown in FIG. FIG. 4 is a plan view showing an intermediate body of the electrode body included in the battery shown in FIG. FIG. 5 is a perspective view schematically showing an electrode body included in the battery shown in FIG. FIG. 6 is a diagram illustrating a state when the battery illustrated in FIG. 1 is dropped.

[Embodiment]
Hereinafter, embodiments will be described with reference to the drawings. In the drawings, the same or corresponding components are denoted by the same reference numerals, and the same description is not repeated.

(Battery configuration)
FIG. 1 is a perspective view schematically showing a battery 100 according to the embodiment. The battery 100 is a so-called prismatic battery and has a substantially flat rectangular shape. Hereinafter, for convenience of explanation, the short side direction (x direction) of the side surface having the large area of the battery 100 is the width direction, and the direction perpendicular to the side surface having the large area (y direction) is the thickness direction, the width direction, and the thickness direction. The direction (z direction) is referred to as the height direction.

  As shown in FIG. 1, the battery 100 includes a battery case 1 and an electrode body 2. The battery case 1 accommodates the electrode body 2. An electrolytic solution (not shown) is also accommodated in the battery case 1.

  FIG. 2 is a cross-sectional view of battery 100 cut by a plane passing through the center in the thickness direction and along the height direction. FIG. 3 is a partial cross-sectional view of battery 100 cut by a plane passing through the center in the width direction and extending along the height direction.

  As shown in FIG. 2, the battery case 1 includes a side wall part 11, a bottom part 12, a convex part 13, and a lid 14. Although the side wall part 11, the bottom part 12, the convex part 13, and the lid | cover 14 are not specifically limited, For example, it is comprised with metals, such as an aluminum alloy. The side wall part 11, the bottom part 12, and the convex part 13 are integrally formed.

  The side wall portion 11 has a flat cylindrical shape. The side wall part 11 is formed in the cylinder shape whose dimension of the thickness direction is smaller than the dimension of the width direction. More specifically, the side wall portion 11 includes a pair of flat plate portions 111 and a pair of arc portions 112 that face each other. Each arc portion 112 is provided at both ends in the width direction of the pair of flat plate portions 111 and connects the flat plate portions 111 to each other. However, the shape of the side wall portion 11 is not limited to this, and may be, for example, a rectangular tube shape or an elliptic tube shape. Each outer surface of the flat plate portion 111 constitutes a side surface having a large area in the battery 100 having a substantially flat rectangular shape. Each outer surface of the arc portion 112 constitutes a side surface having a small area in the battery 100.

  The side wall part 11 has a larger dimension in the axial direction than a dimension in a direction orthogonal to the axial direction. In other words, the maximum length of the side wall part 11 in the height direction is larger than the maximum lengths of the side wall part 11 in the width direction and the thickness direction. Therefore, the battery case 1 has a vertically long, generally rectangular shape in a side view.

  The bottom part 12 seals one end of the side wall part 11 in the axial direction. The bottom part 12 constitutes the case body 10 together with the side wall part 11 and a convex part 13 described later. The case body 10 has an opening 101 at the end opposite to the bottom 12 in the height direction. The case body 10 can be formed, for example, by deep drawing a metal plate such as an aluminum alloy. Hereinafter, in the height direction, the direction in which the opening 101 is located may be referred to as “up” and the direction in which the bottom 12 is located may be referred to as “down”.

  The bottom portion 12 preferably has a thickness greater than the thickness of the side wall portion 11. For example, the thickness of the bottom 12 can be 0.5 mm. In this case, the wall thickness of the side wall part 11 can be 0.3 mm.

  As shown in FIGS. 2 and 3, the convex portion 13 projects inward of the battery case 1 from the inner surface 121 of the bottom portion 12. The convex portion 13 supports the electrode body 2 disposed in the battery case 1. The convex portion 13 is disposed at the center of the inner surface 121 of the bottom portion 12. The outer peripheral edge of the convex portion 13 is separated from the outer peripheral edge of the inner surface 121 of the bottom portion 12.

  The surface of the convex portion 13 is curved. That is, the convex part 13 does not have a corner | angular part on the surface. The height of the convex portion 13 gradually increases toward the center in the width direction and the center in the thickness direction. The maximum height of the convex portion 13 can be appropriately determined in consideration of the weight of the battery 100, the thickness of the side wall portion 11, and the like. For example, the maximum height of the convex portion 13 can be 0.1 mm.

  It is preferable that the convex portion 13 has a height that does not cause the electrode body 2 to substantially interfere with the portion where the battery case 1 is deformed when the battery 100 is dropped. The deformation of the battery case 1 when the battery 100 is dropped will be described in detail later.

  As shown in FIG. 2, the lid 14 seals the opening 101 of the case body 10. The lid 14 has a mounting hole 141 and a liquid injection hole 142. The attachment hole 141 and the liquid injection hole 142 respectively penetrate the lid 14 in the height direction.

  The insulating member 31 and the negative electrode terminal 32 are attached to the attachment hole 141. The insulating member 31 insulates the negative electrode terminal 32 from the lid 14. The insulating member 31 can be made of, for example, polypropylene. The negative electrode terminal 32 can be made of, for example, stainless steel.

  The insulating member 31 has a substantially cylindrical shape and is inserted into the mounting hole 141. The negative terminal 32 has a substantially columnar shape and is inserted into the insulating member 31. That is, the insulating member 31 is disposed between the negative electrode terminal 32 and the lid 14. A part of the insulating member 31 and the negative electrode terminal 32 is exposed from the lid 14 to the outside of the battery case 1.

  A lead plate 33 made of, for example, stainless steel is provided on the inner surface of the lid 14. The lead plate 33 is connected to the negative terminal 32. An insulating member 34 is disposed between the lead plate 33 and the lid 14.

  In the battery case 1, an insulating plate 35 is disposed between the negative electrode terminal 32 and the electrode body 2. The insulating plate 35 prevents a short circuit from occurring between the negative electrode terminal 22 and the electrode body 2.

  The liquid injection hole 142 is used when an electrolytic solution (not shown) is injected into the battery case 1. The liquid injection hole 142 is sealed by the sealing plug 4.

  The electrode body 2 includes a positive electrode 21, a negative electrode 22, and a separator 23. The separator 23 is disposed between the positive electrode 21 and the negative electrode 22. The electrode body 2 is a wound body formed by stacking and winding the positive electrode 21, the negative electrode 22, and the separator 23. However, the configuration of the electrode body 2 is not limited to this.

  A positive electrode lead 24 is connected to the positive electrode 21. The positive electrode lead 24 is also connected to the lid 14. That is, the positive electrode 21 is electrically connected to the battery case 1 via the positive electrode lead 24. Therefore, the battery case 1 functions as a positive electrode terminal of the battery 100.

  A negative electrode lead 25 is connected to the negative electrode 22. The negative electrode lead 25 is also connected to the lead plate 33. As described above, the lead plate 33 is connected to the negative terminal 32. Therefore, the negative electrode 22 is electrically connected to the negative electrode terminal 32 via the negative electrode lead 25 and the lead plate 33.

  Although not particularly illustrated, an insulating tape may be attached to a portion of the electrode body 2 that is close to the bottom 12 of the battery case 1 (a lower portion in FIGS. 2 and 3).

(Battery manufacturing method)
Hereinafter, an outline of a method for manufacturing the battery 100 will be described. However, the manufacturing method of the battery 100 is not limited to the example described in this embodiment.

  First, the electrode body 2 is formed. FIG. 4 is a plan view showing an outline of the intermediate body 2i produced when the electrode body 2 is formed. In order to produce the intermediate 2i, a positive electrode 21, a negative electrode 22, and a separator 23 each having a belt shape are prepared.

  The positive electrode 21 includes a positive electrode current collector 211 and a positive electrode mixture layer 212. The positive electrode current collector 211 is formed in a strip shape. The positive electrode current collector 211 is formed of, for example, a foil such as aluminum or titanium, a plain woven wire net, an expanded metal, a lath net, or a punching metal.

  The positive electrode mixture layer 212 is formed on both surfaces of the positive electrode current collector 211. The positive electrode mixture layer 212 is provided on the positive electrode current collector 211 so that a part of the positive electrode current collector 211 is exposed. For example, the positive electrode mixture layer 212 exposes one end of the positive electrode current collector 211 in the long side direction. A positive electrode lead 24 is connected to a portion of the positive electrode current collector 211 exposed from the positive electrode mixture layer 212.

  The positive electrode mixture layer 212 is formed by mixing a positive electrode active material, a conductive additive, and a binder. As the positive electrode active material, for example, lithium manganate, lithium nickel composite oxide, lithium cobalt composite oxide, lithium nickel cobalt composite oxide, vanadium oxide, molybdenum oxide, or the like can be used. As the conductive aid, for example, graphite, carbon black, acetylene black, or the like can be used. As the binder, for example, polyimide, polyamideimide, polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), or the like can be used alone or in combination.

  The negative electrode 22 includes a negative electrode current collector 221 and a negative electrode mixture layer 222. The negative electrode current collector 221 is formed in a strip shape. The negative electrode current collector 221 is formed of, for example, a foil such as copper, nickel, or stainless steel, a plain woven wire net, an expanded metal, a lath net, or a punching metal.

  The negative electrode mixture layer 222 is formed on both surfaces of the negative electrode current collector 221. The negative electrode mixture layer 222 is provided on the negative electrode current collector 221 so that a part of the positive electrode current collector 211 is exposed. For example, the negative electrode mixture layer 222 exposes one end of the negative electrode current collector 221 in the long side direction. A negative electrode lead 25 is connected to a portion of the negative electrode current collector 221 exposed from the negative electrode mixture layer 222.

  The negative electrode mixture layer 222 is formed by mixing a negative electrode active material and a binder. As the negative electrode active material, for example, natural graphite, mesophase carbon, amorphous carbon, or the like can be used. As the binder, for example, cellulose such as carboxymethyl cellulose (CMC) and hydroxypropyl cellulose (HPC), rubber binder such as styrene butadiene rubber (SBR) and acrylic rubber, PTFE, PVDF, etc. may be used alone or in combination. it can.

  The separator 23 can be formed of a porous film or a nonwoven fabric such as polypropylene (PP), polyethylene (PE), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), or polyphenyl sulfide (PPS). .

  The intermediate body 2i is produced by laminating | stacking the negative electrode 22, the separator 23, the positive electrode 21, and the separator 23 in this order. In the intermediate 2 i shown in FIG. 4, the illustration of the separator 23 on the positive electrode 21 is omitted. The separator 23 is disposed on both surfaces of the positive electrode 21. The positive electrode 21 is disposed between the two separators 23. In addition, the lamination | stacking form of the negative electrode 22, the positive electrode 21, and the separator 23 is not restricted to this. For example, the separator 23, the negative electrode 22, the separator 23, and the positive electrode 21 can be laminated in this order. The negative electrode lead 25 is disposed at the end opposite to the end where the positive electrode lead 24 is disposed in the long side direction of the intermediate body 2i. However, the negative electrode lead 25 can also be arranged at the end on the same side as the positive electrode lead 24 in the long side direction of the intermediate body 2i.

  The produced intermediate body 2i is wound and pressed to form a flat shape. Thereby, the spiral electrode body 2 shown in FIG. 5 is obtained. A positive electrode lead 24 and a negative electrode lead 25 protrude from one surface (upper surface) of the electrode body 2 in the winding axis direction. The side surface and / or the bottom surface of the wound intermediate body 2i may be covered with an insulating tape.

  The electrode body 2 is inserted into the case body 10 as shown in FIG. At this time, the electrode body 2 is inserted into the case body 10 such that the other surface (lower surface) in the winding axis direction faces the convex portion 13 in the case body 10. The electrode body 2 is placed on the convex portion 13.

  An insulating plate 35 is disposed on the electrode body 2 in the case body 10. The tip of the positive electrode lead 24 protruding from the upper surface of the electrode body 2 is connected to the lid 14. The tip of the negative electrode lead 25 protruding from the upper surface of the electrode body 2 is connected to the lead plate 33. The insulating member 31, the negative electrode terminal 32, the lead plate 33, and the insulating member 34 are assembled to the lid 14.

  Next, the lid 14 is joined to the outer peripheral edge of the opening 101 in the case body 10. The lid 14 can be joined to the case body 10 by welding or the like, for example. As a result, the opening 101 of the case body 10 is sealed by the lid 14.

Thereafter, an electrolytic solution (not shown) is injected into the battery case 1 from the liquid injection hole 142. The electrolytic solution is a solution in which a lithium salt is dissolved in an organic solvent. Examples of organic solvents include vinylene carbonate (VC), propylene carbonate (PC), ethylene carbonate (EC), butylene carbonate (BC), dimethyl carbonate (DMC), diethyl carbonate (DEC), methyl ethyl carbonate (MEC), or γ-butyrolactone or the like can be used alone or in admixture of two or more. As the lithium salt, for example, LiPF ₆ , LiBF ₄ , or LiN (CF ₃ SO ₂ ) ₂ can be used.

  After injecting an electrolytic solution (not shown) into the battery case 1, the liquid injection hole 142 is sealed with the sealing plug 4. The sealing plug 4 is joined to the outer peripheral edge portion of the liquid injection hole 142 in the lid 14 by welding or the like, for example. Thereby, the battery 100 can be obtained.

(Effect of embodiment)
According to the battery 100 according to the present embodiment, it is possible to prevent the electrode body 2 from being damaged when dropped. This will be specifically described below.

  FIG. 6 shows a state in which the battery 100 is dropped from the corner 15 formed by the arc 112 and the bottom 12 of the battery case 1. When the battery 100 falls and the corner 15 of the battery case 1 collides with the surface S, the corner 15 is deformed. More specifically, due to the collision force F received by the battery 100 from the surface S, the portion (lower end) 112a near the bottom of the arc portion 112 is mainly deformed.

As described above, the battery case 1 has a vertically long, generally rectangular shape in side view. For this reason, when the battery 100 falls from the corner 15 of the battery case 1, the battery 100 is more easily inclined in the direction of the bottom 12 than in the direction of the arc 112. Therefore, the angle θ formed by the surface S on which the battery 100 collides and the arc portion 112 is greater than 45 °. In this case, a force F ₂ larger than the force F ₁ acting on the bottom portion 12 acts on the arc portion 112, and a relatively large deformation can occur in the lower end portion 112a.

  However, in the present embodiment, the electrode body 2 in the battery case 1 is supported by the convex portion 13 and arranged away from the bottom portion 12 in the height direction. For this reason, when the lower end 112a of the arc portion 112 is deformed due to the fall of the battery 100, interference between the deformed lower end 112a and the electrode body 2 hardly occurs.

  In general, when the electrode body in the battery case is a wound body, the electrode body can be dislodged when the corners of the battery case are deformed due to the fall of the battery. For example, the separator of the electrode body is pushed up by the deformed corner, and an internal short circuit may occur in the electrode body. On the other hand, in this embodiment, the electrode body 2 and the bottom portion 12 of the battery case 1 are separated in advance by the convex portion 13. Therefore, a situation in which the positive electrode 21, the negative electrode 22, and / or the separator 23 are pushed up by the deformed corner portion 15 hardly occurs. As a result, the occurrence of wobbling of the electrode body 2 is suppressed, and an internal short circuit of the electrode body 2 can be prevented.

  Thus, according to the battery 100 which concerns on this embodiment, generation | occurrence | production of the damage of the electrode body 2 at the time of fall can be suppressed.

  In the battery 100 according to this embodiment, the convex portion 13 is disposed at the center of the inner surface 121 of the bottom portion 12. That is, the convex portion 13 is disposed away from the corner portion 15 of the battery case 1. Therefore, when the corner portion 15 is deformed due to the fall of the battery 100, it is possible to prevent the convex portion 13 and the deformed corner portion 15 from interfering with each other.

  In the battery 100 according to the present embodiment, since the surface of the convex portion 13 is curved, the convex portion 13 is in surface contact with the electrode body 2. Therefore, when the battery 100 falls, it can prevent that the force from the convex part 13 concentrates on a part of electrode body 2. FIG. That is, the convex portion 13 prevents the positive electrode 21, the negative electrode 22, and / or the separator 23 from being pushed up individually. As a result, it is difficult for the electrode body 2 to slip and the occurrence of damage to the electrode body 2 can be suppressed.

  The battery 100 according to the present embodiment is more effective when a large deformation is likely to occur in the side wall portion 11 when dropped. That is, in this embodiment, the side wall part 11 has a dimension in the axial direction larger than a dimension in a direction orthogonal to the axial direction. For this reason, the angle θ between the surface S on which the dropped battery 100 collides and the arc portion 112 becomes larger than 45 °, and the lower end portion 112a of the arc portion 112 may be greatly deformed. However, since the electrode body 2 is separated from the bottom portion 12 by the convex portion 13, even in such a case, interference between the electrode body 2 and the lower end portion 112a can be reduced.

  Even when the thickness of the side wall portion 11 is smaller than the thickness of the bottom portion 12, the lower end portion 112 a of the arc portion 112 is easily deformed. However, in the present embodiment, as described above, since the electrode body 2 is separated from the bottom portion 12 by the convex portion 13, the problem of interference between the deformed lower end portion 112a and the electrode body 2 hardly occurs. For this reason, the necessity to ensure the strength of the side wall portion 11 is reduced, and the side wall portion 11 can be thinned.

  For example, when the battery case 1 is formed by deep drawing a metal plate such as an aluminum alloy, the metal plate is greatly bent at the corner 15. For this reason, at the time of molding, the thickness of the corner portion 15 may be smaller than the thickness of the side wall portion 11 and the thickness of the bottom portion 12. In this case, the corner portion 15 is more easily deformed when the battery 10 is dropped than the side wall portion 11 and the bottom portion 12. However, in the present embodiment, the electrode body 2 is separated from the bottom portion 12 by the convex portion 13. For this reason, even if the corner portion 15 located between the side wall portion 11 and the bottom portion 12 is deformed, the deformed corner portion 15 is unlikely to interfere with the electrode body 2, and the occurrence of damage to the electrode body 2 is suppressed. can do.

[Modification]
Although the embodiments have been described above, the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the gist thereof.

  In the said embodiment, one convex part is arrange | positioned in the center of the inner surface of a bottom part. However, the number and position of the convex portions are not particularly limited. The convex portion may not be arranged at the center of the inner surface of the bottom portion, and a plurality of convex portions may be provided on the inner surface of the bottom portion.

  In the said embodiment, the convex part has a shape where the height becomes large gradually toward the center of the width direction and the center of the thickness direction. However, the shape of the convex portion is not particularly limited. For example, the shape of the convex portion may be such that the height changes in the width direction and / or the thickness direction so that the surface is wavy, or the height is constant in the width direction and / or the thickness direction. It may be. Further, the surface of the convex portion does not have to be curved.

  In the said embodiment, the side wall part of a battery case is comprised so that the dimension of an axial direction may become larger than the dimension of the direction orthogonal to an axial direction. However, the side wall portion may have an axial dimension smaller than a dimension perpendicular to the axial direction, or an axial dimension substantially equal to a dimension perpendicular to the axial direction.

  In the said embodiment, the battery case has the battery case main body which has opening in the surface opposite to a bottom part, and the lid | cover which seals the said opening. However, the configuration of the battery case is not limited to this. For example, an opening may be provided in the side wall portion of the battery case, and the opening may be sealed after the electrode body is accommodated in the battery case.

  100: battery, 1: battery case, 11: side wall, 12: bottom, 13: convex, 2: electrode body, 21: positive electrode, 22: negative electrode, 23: separator

Claims (4)

An electrode body including a positive electrode, a negative electrode, and a separator disposed between the positive electrode and the negative electrode;
A battery case containing the electrode body and including a flat cylindrical side wall part, a bottom part sealing one axial end of the side wall part, and a convex part projecting from the inner surface of the bottom part and supporting the electrode body When,
A battery comprising: The battery according to claim 1,
The said convex part is a battery arrange | positioned in the center of the inner surface of the said bottom part. The battery according to claim 1 or 2,
The surface of the convex part is a battery having a curved surface. The battery according to any one of claims 1 to 3,
The said side wall part is a battery whose dimension of an axial direction is larger than the dimension of the direction orthogonal to an axial direction.

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