JP7084239B2 - Secondary battery - Google Patents

Description

The present invention relates to a secondary battery.

Power supply for driving electric vehicles (EV) and hybrid electric vehicles (HEV, PHEV), applications for suppressing output fluctuations such as solar power generation and wind power generation, and grid power for storing power at night and using it in the daytime. Alkaline secondary batteries and non-aqueous electrolyte secondary batteries are used in stationary storage battery systems and the like for peak shift applications.

In a battery used for such an application, for example, as shown in Patent Document 1 below, not only a gas discharge valve that releases the internal pressure when the pressure inside the battery exterior increases, but also an external terminal is provided. A current cutoff mechanism for breaking the electrical connection with the electrode body inside the outer body is provided.

Japanese Unexamined Patent Publication No. 2018-41678

In the current cutoff mechanism, for example, as in the technique disclosed in Patent Document 1, a structure in which a groove-shaped notch portion is provided in a current collector welded to a deformable plate is adopted. In this structure, when the pressure inside the battery case increases and the deformed plate is deformed, the notch portion is broken and the electrical connection between the external terminal and the electrode body is cut off.

The current cutoff mechanism operates as described above, but it is important that the current cutoff mechanism operates stably when a predetermined pressure value is reached in the battery case of any of the batteries when manufacturing a large number of batteries. Is. As a result of studies for reducing the variation in the operating pressure of the current cutoff mechanism, the inventor of the present application has found that the variation in the operating pressure of the current cutoff mechanism can be reduced by devising the shape of the notch portion.

The present invention has been made in view of this point, and an object thereof is a secondary battery in which the current cutoff mechanism operates stably in any battery by reducing the variation in the operating pressure of the current cutoff mechanism. Is to provide.

The secondary battery of the present invention includes a battery case having an opening, an electrode body including a positive electrode and a negative electrode housed in the battery case, a current collector electrically connected to the positive electrode or the negative electrode, and the opening. It is located between the sealing plate, the external terminal attached to the sealing plate, and the sealing plate and the electrode body, is electrically connected to the external terminal, and has an opening portion on the electrode body side. It is provided with a conductive member, a deformable plate that seals the opening portion, is connected to the current collector, and deforms when the pressure in the battery case exceeds a predetermined value, and the current collector is concave. A thin-walled portion that has a shape and breaks when the deformed plate is deformed is provided, and the thin-walled portion is a bottom surface that is the bottom of the concave shape in a cross section cut along the thickness direction of the current collector. A portion, a first side surface portion connecting one end of the bottom surface portion and one outer edge of the thin-walled portion, and a second side surface portion connecting the other end portion and the other outer edge of the thin-walled portion. The thickness a of the bottom surface portion at the one end portion is smaller than the thickness b of the bottom surface portion at the other end portion, and the other end portion is larger than the one end portion. It has a configuration provided near the connection portion with the deformable plate.

The thin-walled portion preferably has a groove shape that surrounds the portion to which the deformed plate and the current collector are connected.

The distance c between the one end portion and the other end portion may be larger than the thickness a of the bottom surface portion at the one end portion.

The thickness a of the bottom surface portion at the one end portion may be ½ or more and 9/10 or less of the thickness b of the bottom surface portion at the other end portion.

At the thickness a of the bottom surface portion at the one end portion, the thickness b of the bottom surface portion at the other end portion, and the distance c between the one end portion and the other end portion, (ba) / c. The value of may be 0.17 or more and 0.58 or less.

In the secondary battery of the present invention, the thin-walled portion that breaks due to the deformation of the deformed plate has a bottom surface portion and two side surface portions, and the thickness of the bottom surface portion is different at the boundary portion between the two side surface portions, so that current is cut off. It is possible to suppress the variation in the operating pressure of the mechanism.

It is a schematic front view which shows the inside of the battery which removed the battery case front part and the insulation sheet front part of the battery which concerns on embodiment. It is a schematic top view of the battery which concerns on embodiment. It is a schematic side view which shows the inside of the battery of the positive electrode side which removed the battery case side surface (positive electrode side) portion and the insulating sheet side surface (positive electrode side) portion of the battery which concerns on embodiment. It is a schematic side view which shows the inside of the battery of the negative electrode side which removed the battery case side surface (negative electrode side) portion and the insulating sheet side surface (negative electrode side) portion of the battery which concerns on embodiment. It is a schematic enlarged sectional view near the positive electrode terminal which cut the battery which concerns on embodiment along the center line of the upper surface parallel to the front. It is a schematic enlarged sectional view in the vicinity of a positive electrode terminal which cut the battery which concerns on embodiment along the center line of a positive electrode terminal parallel to the side surface. It is an enlarged sectional view of the part shown by A of FIG. It is an enlarged sectional view in the circle of FIG. 7. It is a schematic cross-sectional view which shows an example of the shape of the conventional thin-walled part. It is an enlarged sectional view in the circle of FIG. It is a schematic cross-sectional view which shows another example of the shape of the conventional thin-walled part. It is a schematic cross-sectional view which shows an example of the shape of the thin-walled portion of another embodiment. It is an enlarged sectional view in the circle of FIG.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The following description of preferred embodiments is merely exemplary and is not intended to limit the invention, its applications or its uses. In the following drawings, for the sake of brevity, components having substantially the same function are indicated by the same reference numerals.

(Embodiment 1)
First, the secondary battery of the first embodiment will be described with reference to FIGS. 1 to 4. The secondary battery of the present embodiment has a flat electrode body 110 in which a positive electrode plate and a negative electrode plate are wound by a separator (both not shown). The positive electrode plate constituting the positive electrode is formed by applying a positive electrode active material mixture to both sides of a positive electrode core made of aluminum foil, drying and rolling, and then the aluminum foil is formed into a strip along the longitudinal direction at one end. It is made by slitting it so that it is exposed. Further, in the negative electrode plate constituting the negative electrode, a negative electrode active material mixture is applied to both sides of a negative electrode core made of copper foil, dried and rolled, and then the copper foil is attached to one end along the longitudinal direction. It is produced by slitting so as to be exposed in a band shape.

The positive electrode plate and the negative electrode plate obtained as described above have a region in which the exposed portion of the positive electrode core of the positive electrode plate and the exposed portion of the negative electrode core of the negative electrode plate do not overlap with the facing electrodes. The electrode body 110 is manufactured by laminating and winding the electrode body 110 via a microporous separator made of polypropylene and polyethylene. A positive electrode core body exposed portion 141 is formed at one end of the electrode body 110 in the winding axis direction, and a negative electrode core body exposed portion 140 is formed at the other end portion.

The positive electrode core body exposed portion 141 is electrically connected to the positive electrode terminal 130, which is an external terminal, via the positive electrode current collector 10. The lead portion 14 of the positive electrode current collector 10 is welded and connected to one outer surface of the positive electrode core body exposed portion 141. A receiving member 143 of the positive electrode current collector 10 is welded and connected to the other outer surface of the positive electrode core body exposed portion 141. An insulating film having an opening is arranged between one outer surface of the positive electrode core body exposed portion 141 and the lead portion 14 of the positive electrode current collector 10, and the positive electrode core body exposed portion 141 and the positive electrode current collector are arranged through the opening of the insulating film. The lead portion 14 of the body 10 is welded and connected. An insulating film 147 having an opening is arranged between the other outer surface of the positive electrode core body exposed portion 141 and the receiving member 143 of the positive electrode current collector 10, and the positive electrode core body exposed portion 141 and the positive electrode are formed through the opening of the insulating film 147. The receiving member 143 of the current collector 10 is welded and connected. The insulating film arranged between the outer surface of the receiving member 143 of the positive electrode current collector 10, the insulating film 147, and the exposed portion 141 of the positive electrode core and the lead portion 14 of the positive electrode current collector 10 is indispensable. Instead, it can be omitted.

Further, the positive electrode current collector 10 is electrically insulated from the sealing plate 120 by the first insulating member 50 and the second insulating member 150.

The negative electrode core body exposed portion 140 is electrically connected to the negative electrode terminal 132, which is an external terminal, via the negative electrode current collector 20. The lead portion 114 of the negative electrode current collector 20 is welded and connected to one outer surface of the negative electrode core body exposed portion 140. A receiving member 142 of the negative electrode current collector 20 is welded and connected to the other outer surface of the negative electrode core body exposed portion 140. An insulating film having an opening is arranged between one outer surface of the negative electrode core body exposed portion 140 and the lead portion 114 of the negative electrode current collector 20, and the negative electrode core body exposed portion 140 and the negative electrode collection are provided through the opening of the insulating film. The lead portion 114 of the electric body 20 is welded and connected. An insulating film 146 having an opening is arranged between the other outer surface of the negative electrode core body exposed portion 140 and the receiving member 142 of the negative electrode current collector 20, and the negative electrode core body exposed portion 140 and the negative electrode core body exposed portion 140 are arranged through the opening of the insulating film 146. The receiving member 142 of the negative electrode current collector 20 is welded and connected. The insulating film arranged between the outer surface of the receiving member 142 of the negative electrode current collector 20, the insulating film 146, and the exposed portion 140 of the negative electrode core and the lead portion 114 of the negative electrode current collector 20 is indispensable. Instead, it can be omitted.

Further, the negative electrode current collector 20 is electrically insulated from the sealing plate 120 by the negative electrode side insulating member 52a.

The positive electrode terminal 130 and the negative electrode terminal 132 are fixed to the sealing plate 120 via the terminal portion insulating member 152 and the terminal portion insulating member 154, respectively. In the secondary battery of the present embodiment, a pressure-sensitive current cutoff mechanism 200 is provided between the positive electrode and the positive electrode terminal 130.

The electrode body 110 is housed in a bottomed cylindrical battery case 100 in a state where the periphery excluding the sealing plate 120 side is covered with a resin insulating sheet 161. The opening of the battery case 100 is sealed by the sealing plate 120. The sealing plate 120 is provided with an electrolytic solution injection hole 163. The electrolytic solution injection hole 163 is sealed with a sealing plug after injection. Further, the sealing plate 120 is provided with a gas discharge valve 162 that is opened when a gas pressure higher than the operating pressure of the current cutoff mechanism 200 is applied.

Next, the current cutoff mechanism 200 will be described. The current cutoff mechanism 200 may be provided on either the positive electrode side or the negative electrode side. Hereinafter, it will be described as being provided only on the positive electrode side. In the current cutoff mechanism 200, the fragile portion provided in a part of the energization path was broken by the member in the vicinity of the fragile portion being deformed as the pressure in the battery case 100 increased, and the energization was cut off. It works by the mechanism of being used.

As shown in FIGS. 5 and 6, the positive electrode terminal 130 has a through hole formed inside. The positive electrode terminal 130 is inserted into through holes formed in each of the terminal portion insulating member 152, the sealing plate 120, the second insulating member 150, and the conductive member 30, and the tip portion of the positive electrode terminal 130 on the battery internal side is inserted. It is crimped so as to be pressure-welded to the conductive member 30 and is integrally fixed to each other. As a result, the positive electrode terminal 130 is electrically insulated from the sealing plate 120 by the terminal portion insulating member 152 and the second insulating member 150, and is electrically connected to the conductive member 30. Although not shown in the figure, in FIGS. 5 and 6, the electrode body is present on the opposite side of the sealing plate 120 with respect to the second insulating member 150 of all the illustrated components. It is preferable that the tip of the positive electrode terminal 130 on the inner side of the battery and the connection portion of the conductive member 30 are welded and connected by laser welding or the like. Further, the through hole formed in the positive electrode terminal 130 is sealed by a rubber terminal plug 158 provided with a metal plate 159 at the upper end.

The second insulating member 150 is arranged between the sealing plate 120 and the conductive member 30, and insulates the sealing plate 120 and the conductive member 30. The conductive member 30 has a cylindrical portion 32 having a substantially rectangular cross section on the electrode body 110 side, and a connecting portion arranged parallel to the sealing plate 120 is formed on the sealing plate 120 side. There is. The positive electrode terminal 130 is inserted into the through hole provided in the conductive member 30.

The opening portion of the tubular portion 32 of the conductive member 30 on the electrode body 110 side is sealed by the deforming plate 40. The tip portion of the tubular portion 32 of the conductive member 30 and the periphery of the deformable plate 40 are welded. The deformable plate 40 is made of a conductive material such as aluminum. When the pressure inside the battery case 100 increases to a predetermined value or more, the deformable plate 40 is deformed so that the central portion of the deformable plate 40 approaches the sealing plate 120 side (outside the battery side). A positive electrode current collector 10 is connected to the surface of the deformed plate 40 on the electrode body 110 side. The positive electrode current collector 10 is preferably made of metal, and preferably made of aluminum or an aluminum alloy. As the positive electrode current collector 10, for example, a metal plate made of aluminum or the like by punching can be used. From the above, the energization path is formed in the order of the positive electrode body 110, the positive electrode current collector 10, the deformed plate 40, the conductive member 30, and the positive electrode terminal 130.

The first insulating member 50 is arranged between the positive electrode current collector 10 and the portion other than the central portion of the deformable plate 40. The first insulating member 50 is provided with a through hole in a portion corresponding to the central portion of the deformable plate to which the deformable plate 40 and the positive electrode current collector 10 are connected. The first insulating member 50 and the second insulating member 150 are connected and fixed by engagement. The fixing method is not particularly limited, but here, the fixing is performed by latch fixing using the claw portion 55 formed on the first insulating member 50. This fixed portion is formed on the outer peripheral edge portion of the first insulating member 50.

A through hole is formed in the central portion of the positive electrode current collector 10. As shown in FIG. 5, two through holes on both sides are also formed on both sides of the through hole in the central portion of the positive electrode current collector 10. Further, the first insulating member 50 is provided with a through hole facing the through hole provided in the center of the positive electrode current collector 10, and on both sides thereof, two sides provided on the positive electrode current collector 10. Protrusions are formed at positions corresponding to the through holes on the side.

The protrusions of the first insulating member 50 are inserted into through holes on both sides of the positive electrode current collector 10, and the tips of the protrusions are heated to expand the diameter, whereby the first insulating member 50 and the positive electrode current collector are collected. The body 10 and the body 10 are fixed.

A peripheral region 18 having a thickness thinner than the other portions is provided in the peripheral portion of the through hole in the central portion of the positive electrode current collector 10, and surrounds the through hole in the vicinity of the outer periphery of the peripheral region 18. As described above, the annular thin-walled portion 15 is formed. The thin portion 15 is provided in a groove shape so that the thickness is thinner than the peripheral region 18. Further, an inner peripheral rib portion 19 is provided on the inner peripheral edge of the peripheral region 18, and the deformed plate 40 is laser-welded at the inner peripheral rib portion 19 to electrically connect the deformed plate 40 and the positive electrode current collector 10. There is. The inner peripheral rib portion 19 is not an essential configuration, and the inner peripheral rib portion 19 can be omitted.

The operation of the current cutoff mechanism 200 in this embodiment is as follows. When the pressure in the battery case 100 increases and becomes a predetermined value or more, the deformable plate 40 is deformed so that the central portion of the deformable plate 40 approaches the sealing plate 120. The positive electrode current collector 10 is welded to the deformed plate 40 at the inner peripheral rib portion 19. The thin portion 15 surrounds the welded portion between the positive electrode current collector 10 and the deformed plate 40. Therefore, due to the above-mentioned deformation of the deformed plate 40, the thin-walled portion 15 is broken all around, the electrical connection between the deformed plate 40 and the positive electrode current collector 10 is cut off, and the current is cut off.

Next, the shape of the thin-walled portion 15 of the present embodiment will be described. As shown in FIGS. 7 and 8, in the cross section cut along the thickness direction of the positive electrode current collector 10, the thin-walled portion 15 has a concave shape, and the bottom surface portion 81 and the bottom surface portion 81, which are the bottoms of the concave shape, are formed. It has a first side surface portion 82 that connects one end portion 91 and one outer edge of the thin wall portion 15, and a second side surface portion 83 that connects the other end portion 92 and the other outer edge of the thin wall portion 15. ing. The thickness a of the bottom surface portion 81 at one end portion 91 is smaller than the thickness b of the bottom surface portion 81 at the other end portion 92. That is, the bottom surface portion 81 of the thin-walled portion 15 is not parallel to the surface 80 on the sealing plate 120 side of the thin-walled region 18, but is inclined.

The thin-walled portion 15 is recessed from the peripheral region 18 to become thinner, but the outer edge of the thin-walled portion 15 is a boundary portion where the recessing begins.

On the other hand, the conventional thin-walled portion will be described with reference to one example shown in FIGS. 9 and 10 and another example shown in FIG. In the example of the conventional thin-walled portion 115 shown in FIGS. 9 and 10, the bottom surface portion 84 is parallel to the surface 80 on the sealing plate 120 side of the thin-walled region 18, and one end of the bottom surface portion 84 and the other end thereof. The thickness d of the bottom surface portion 84 at the end portion is the same for both. Further, in the example of the conventional thin-walled portion 215 shown in FIG. 11, the cross-sectional shape is V-shaped and the bottom surface portion is not flat.

The inventor of the present application examined the easiness of breaking of the thin-walled portion as follows.

With respect to the thin-walled portion 15 of the present embodiment and the conventional thin-walled portions 115 and 215, the state of breakage when the deformed plate 40 is deformed is predicted by using the finite element method. An aluminum alloy Al100-O was used as the material of the positive electrode current collector 10. When a load is applied to the deformable plate 40 and the load is gradually increased to deform the deformable plate 40, the thin-walled portion 15 of the present embodiment having the bottom surface portion and the conventional thin-walled portion 115 have a bottom surface portion. As a result, stress is concentrated on the end portion 91 located on the side (left side in FIG. 8) far from the connection portion between the positive electrode current collector 10 and the deformable plate 40 among the bottom surface portions 81 and 84. When the deformation of the deformed plate 40 exceeds a certain threshold value, the portion of one end 91 is broken. On the other hand, in the V-shaped thin-walled portion 215, stress was concentrated on the V-shaped tip portion, which resulted in fracture.

The thickness a of the bottom surface portion 81 at one end 91 of the thin wall portion 15 of the present embodiment, the thickness d of the bottom surface portion 84 of the conventional thin wall portion 115, and the thickness of the V-shaped tip portion of the conventional thin wall portion 215. According to the simulation, the magnitude of the load that causes deformation leading to breakage is in the order of V-shaped thin-walled portion 215> flat bottom thin-walled portion 115> the thin-walled portion 15 of the present embodiment. rice field. As described above, the thin-walled portion 115 having a flat bottom surface breaks with a smaller load than the V-shaped thin-walled portion 215. This is because the thin-walled portion 115 has a flat bottom surface, so that the thin-walled portion 115 is easily deformed so that the angle formed by the bottom surface and the side surface portion becomes large as the deformable plate 40 is deformed. On the other hand, in the V-shaped thin-walled portion 215, the thin-walled portion 215 is difficult to change so that the angle formed by the pair of side surface portions is large, so that the load required for breaking is large in the V-shaped thin-walled portion 215. Further, the reason why the thin-walled portion 15 of the present embodiment breaks with a smaller load than the thin-walled portion 115 having a flat bottom surface is that the inclined bottom surface is distorted by the end portion on the breaking side rather than the flat bottom surface. It is thought that this is due to the concentration.

As described above, the thin-walled portion 15 of the present embodiment breaks with a smaller load than the conventional two types of thin-walled portions 115 and 215, even if the thickness is the same. And / or even if an impact or a large force is applied during assembly of the battery, the final breaking load does not change unless the thickness a of the bottom surface portion 81 of one end portion 91 changes. It is possible to avoid variations in breaking load in each battery.

In the thin-walled portion 15 of the present embodiment, the distance c between one end portion 91 and the other end portion 92 (the distance along the surface of the bottom surface portion 81 on the electrode body 110 side, and the width of the bottom surface portion 81) is It is preferable that the thickness a of the bottom surface portion 81 at one end portion 91 is larger than the thickness a. With such a relationship, when a large number of thin-walled portions 15 are manufactured, the variation in the breaking load becomes small.

Further, a / b is preferably 1/2 or more and 9/10 or less. If a / b is smaller than 1/2, the difference from the conventional V-shaped thin-walled portion 215 becomes considerably small. Further, if a / b is larger than 9/10, the difference from the conventional thin-walled portion 115 having a flat bottom surface becomes considerably small.

Further, in the thin-walled portion 15 of the present embodiment, the value of (ba) / c is preferably 0.17 or more and 0.58 or less. If it is smaller than 0.17, the difference from the conventional thin-walled portion 115 having a flat bottom surface becomes considerably small. Further, if it is larger than 0.58, the difference from the conventional V-shaped thin-walled portion 215 becomes small.

When actually forming a thin-walled portion, the corner portion is rounded (the corner has R). Even if there is a rounded part like this, unless the entire cross section of the thin-walled part is an arc or a part of an ellipse that is entirely curved and the corners cannot be recognized, that is, the corners If it can be determined, it can be determined whether or not it corresponds to the thin-walled portion of the present embodiment.

(Embodiment 2)
The secondary battery according to the second embodiment is different from the secondary battery according to the first embodiment because the shape of the thin-walled portion is different from that of the first embodiment, but the other parts are the same as those of the first embodiment. The part that is used is explained below.

As shown in FIGS. 12 and 13, in the thin-walled portion 315 of the present embodiment, the first side surface portions 86 and 87 extending from one end to one outer edge of the thin-walled portion 315 are bent in the middle. Is different from the first embodiment. The second side surface portion 88 is the same as that of the first embodiment. Of the bent first side surface portions, the bottom surface side side surface portion 86 on the side closer to the bottom surface portion 85 has the same angle as the first side surface portion 82 of the first embodiment (the surface of the thin-walled region 18 on the sealing plate 120 side). The angle with respect to 80, about 60 degrees). The side surface portion 87 on the opening side has an angle perpendicular to the surface 80 on the sealing plate 120 side of the thin-walled region 18.

Even if the first side surface portion of the thin-walled portion 315 is bent in this way, the bottom surface portion 85 is present, and the thickness of the bottom surface portion 85 is different between one end portion and the other end portion. If the larger end is located on the side closer to the welded portion between the positive electrode current collector 10 and the deformed plate (in FIG. 12, the side closer to the inner peripheral rib portion 19 which is the connection portion with the deformed plate), the implementation is performed. It produces the effects described in Form 1. Further, c1> a1 is preferable, a1 / b1 is preferably 1/2 or more and 9/10 or less, and the value of (b1-a1) / c1 is 0.17 or more and 0.58 or less. Is preferable.

(Other embodiments)
The above-described embodiment is an example of the present invention, and the present invention is not limited to these examples, and well-known techniques, conventional techniques, and known techniques may be combined or partially replaced with these examples. The invention of the present application also includes modified inventions that can be easily conceived by those skilled in the art.

The secondary battery of the present invention is applicable to both non-aqueous electrolyte secondary batteries and alkaline secondary batteries such as nickel-hydrogen secondary batteries. Further, the deformed plate has a predetermined effect as long as it is connected to either one of the positive electrode current collector and the negative electrode current collector, but it may be connected to both of them.

The battery case is not limited to a rectangular parallelepiped shape (square shape), and may have a bottomed cylindrical shape. Further, the tubular portion of the conductive member is not limited to a rectangular cross section, and may be circular, elliptical, or polygonal.

The side surface may be a vertical wall.

Further, in the first embodiment, an example in which the external terminal and the conductive member are made of separate parts is shown, but the external terminal and the conductive member can be made into one part.

10 Positive electrode current collector 15 Thin-walled portion 20 Negative electrode current collector 30 Conductive member 40 Deformation plate 50 First insulating member 70 Second insulating member 81,85 Bottom surface portion 82,86,87 First side surface portion 83,88 Second Side surface 91 One end 92 The other end 100 Battery case 110 Electrode body 120 Seal plate 130 Positive electrode terminal (external terminal)
132 Negative electrode terminal (external terminal)
200 Current cutoff mechanism 315 Thin wall part

Claims (5)

A battery case with an opening and
An electrode body including a positive electrode and a negative electrode housed in the battery case,
With a current collector electrically connected to the positive electrode or the negative electrode,
A sealing plate that seals the opening and
With the external terminal attached to the sealing plate,
A conductive member located between the sealing plate and the electrode body, electrically connected to the external terminal, and having an opening portion on the electrode body side.
It is provided with a deformable plate that seals the opening portion, is formed of a conductive material , is connected to the current collector and the conductive member , and is deformed when the pressure in the battery case becomes a predetermined value or more. ,
The energization path is formed in the order of the electrode body, the current collector, the deformed plate, the conductive member, and the external terminal.
The current collector has a concave shape, and is provided with a thin-walled portion that breaks when the deformed plate is deformed to break the electrical connection between the deformed plate and the current collector .
In a cross section cut along the thickness direction of the current collector, the thin-walled portion connects the bottom surface portion, which is the bottom of the concave shape, one end portion of the bottom surface portion, and one outer edge of the thin-walled portion. It has a side surface portion of 1 and a second side surface portion connecting the other end portion and the other outer edge of the thin-walled portion.
The thickness a of the bottom surface portion at the one end portion is smaller than the thickness b of the bottom surface portion at the other end portion.
The other end is a secondary battery provided at a position closer to the connection portion with the deformable plate than the one end. The secondary battery according to claim 1, wherein the thin-walled portion has a groove shape surrounding a portion to which the deformable plate and the current collector are connected. The secondary battery according to claim 1 or 2, wherein the distance c between the one end portion and the other end portion is larger than the thickness a of the bottom surface portion at the one end portion. The one according to any one of claims 1 to 3, wherein the thickness a of the bottom surface portion at the one end portion is ½ or more and 9/10 or less of the thickness b of the bottom surface portion at the other end portion. Secondary battery. At the thickness a of the bottom surface portion at the one end portion, the thickness b of the bottom surface portion at the other end portion, and the distance c between the one end portion and the other end portion, (ba) / c. The secondary battery according to claim 4, wherein the value of is 0.17 or more and 0.58 or less.

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