JP2007073437A - Secondary battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a secondary battery having an electrode terminal precisely led out of a predetermined position. <P>SOLUTION: The secondary battery 10 comprises an electrode laminate 108 formed by alternately laminating electrode plates 101 and 103, exterior packaging members 106 and 107 respectively having a first and second cup portions 1061 and 1071 formed into recess-shape, and electrode terminals 104 and 105 connected to the electrode plates 101 and 103. The electrode laminate 108 is held between the cup portions 1061 and 1071 facing each other, and peripheral edges of the exterior packaging members 106 and 107 are joined to each other so that the electrode terminals 104 and 105 are led out of the peripheral edges of the exterior packaging members 106 and 107, thus the electrode laminate 108 is sealed in the first and second cup portions 1061 and 1071, and a side on the side where the terminal is led out in a bottom face 1072 of the second cup portion 1071 is positioned on the interior side of the battery rather than a side on the side where the terminal is led out in a bottom 1062 of the first cup portion 1061. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  In the present invention, an electrode laminate formed by laminating electrode plates is housed and sealed in a sheet-like exterior member having a cup portion, and electrode terminals connected to the electrode plates are led out from the outer peripheral edge of the exterior member. The present invention relates to a secondary battery.

  A sheet-like exterior member is heat-sealed along its outer peripheral edge to accommodate and seal the electrode plate, and the electrode terminals connected to the electrode plate are thinly drawn from the outer peripheral edge of the exterior member. 2. Description of the Related Art Conventionally, a secondary battery that employs a so-called “both cup structure” in which upper and lower exterior members are both formed into a cup shape is known (see, for example, Patent Document 1).

  When thin battery packs are stacked on top of each other and their electrode terminals are electrically connected to form an assembled battery, the electrode terminals must be led out from a certain position in the thickness direction of the secondary battery. There is.

However, in the secondary battery adopting the both-cup structure as described above, the side surfaces of the cup portions of the exterior members on both sides are distorted due to the reduced pressure when the battery stack is accommodated in the exterior member, so that the lead-out positions of the electrode terminals are constant. In some cases, it was not possible to derive it accurately from the position of.
JP 2001-229888 A

An object of the present invention is to provide a secondary battery capable of accurately deriving an electrode terminal from a predetermined position.
In order to achieve the above object, according to the present invention, an electrode laminate in which electrode plates are alternately laminated via separators, and first and second cup-shaped sheets each having a first cup portion and a second cup portion formed in a concave shape are provided. 1 and a second exterior member and an electrode terminal connected to the electrode plate, the first and second cup portions are opposed to each other, and the electrode stack is accommodated therein, and the electrode terminal In the state where the outer peripheral edges of the first and second exterior members are led out from the outer peripheral edges of the first and second exterior members, the electrode stack is joined to the first and second exterior members by joining the outer peripheral edges of the first and second exterior members. A secondary battery sealed in a cup part, wherein a side on the terminal lead-out side of the bottom surface of the second cup part is located on the inner side of the battery than a side on the terminal lead-out side of the bottom surface of the first cup part. A secondary battery is provided.

  In the present invention, in the secondary battery having the double cup structure, the terminal lead-out side on the bottom surface of the second cup portion is positioned inside the battery from the terminal lead-out side on the bottom surface of the first cup portion.

  By positioning the terminal lead-out side of the bottom surface of the second cup portion on the inside of the battery, the space between the second cup portion and the electrode stack is narrowed. The generated distortion is reduced, and the accuracy of the lead-out position of the electrode terminal can be improved.

  On the other hand, by positioning the terminal lead-out side of the bottom surface of the first cup portion outside the battery, a space that allows expansion of the volume when gas is generated inside the battery is provided in the first cup portion and the electrode. Since it can be ensured between the stacked bodies, the life of the secondary battery can be extended.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  1 is a plan view showing a thin battery according to an embodiment of the present invention, FIG. 2 is a schematic cross-sectional view taken along the line II-II in FIG. 1, FIG. 3 is an enlarged cross-sectional view of a portion III in FIG. 4B is an enlarged cross-sectional view of the terminal lead-out portion, FIG. 4A is a diagram showing a state before decompression, and FIG. 4B is a diagram showing a state after decompression.

  1 and 2 show one thin battery 10 (unit battery), and an assembled battery having a desired voltage and capacity is formed by stacking a plurality of thin batteries 10.

  A thin battery 10 according to an embodiment of the present invention is a lithium-based thin secondary battery. As shown in FIGS. 1 and 2, the thin battery 10 includes a plurality of positive plates 101 and negative plates 103, a separator 102 interposed therebetween, a positive terminal 104, a negative terminal 105, and an upper portion. It is comprised from the exterior member 106 and the lower exterior member 107, and the electrolyte which is not specifically illustrated. In the present embodiment, a laminate configured by laminating the positive electrode plate 101 and the negative electrode plate 103 with the separator 102 interposed therebetween is referred to as an electrode laminate 108.

  As shown in FIG. 2, the positive electrode plate 101 includes a positive electrode current collector 101a extending to the positive electrode terminal 104, and positive electrode layers 101b formed on both main surfaces of part of the positive electrode current collector 101a, 101c.

  The positive electrode side current collector 101a is made of an electrochemically stable metal foil such as an aluminum foil, an aluminum alloy foil, a copper foil, or a nickel foil.

The positive electrode layers 101b and 101c are formed by mixing a positive electrode active material, a conductive agent such as carbon black, and an adhesive such as an aqueous dispersion of polytetrafluoroethylene with a positive electrode current collector 101a. It is formed by applying to both main surfaces of the part, drying and rolling. Examples of the positive electrode active material include lithium composite oxides such as lithium nickelate (LiNiO ₂ ), lithium manganate (LiMnO ₂ ), and lithium cobaltate (LiCoO ₂ ), and chalcogen (S, Se, Te) compounds. Etc.

  As shown in FIG. 2, the negative electrode plate 103 includes a negative electrode current collector 103a extending to the negative electrode terminal 105, and negative electrode layers 103b formed on both main surfaces of a part of the negative electrode current collector 103a, 103c.

  The negative electrode side current collector 103a is made of an electrochemically stable metal foil such as a nickel foil, a copper foil, a stainless steel foil, or an iron foil.

  The negative electrode layers 103b and 103c are pulverized after mixing and drying an aqueous dispersion of styrene butadiene rubber resin powder as a precursor of an organic fired body into the negative electrode active material that absorbs and releases lithium ions of the positive electrode active material. Thus, the main material is a carbon particle surface supporting carbonized styrene butadiene rubber, and a binder such as an acrylic resin emulsion is further mixed therewith, and this mixture is used as a part of the negative electrode side current collector 103a. It is formed by applying to both main surfaces, drying and rolling. Specific examples of the negative electrode active material include amorphous carbon, non-graphitizable carbon, graphitizable carbon, and graphite.

  The separator 102 prevents a short circuit between the positive electrode plate 101 and the negative electrode plate 103 and may have a function of holding an electrolyte. The separator 102 is a microporous film made of polyolefin such as polyethylene (PE) or polypropylene (PP), for example, and when an overcurrent flows, the pores of the layer are blocked by the heat generation, thereby blocking the current. It also has a function.

  The separator in the present invention is not limited to a single-layer film such as polyolefin, but may be a three-layer structure in which a polypropylene film is sandwiched with a polyethylene film, or a laminate of a polyolefin microporous film and an organic nonwoven fabric or the like. it can. Thus, by forming the separator in multiple layers, various functions such as an overcurrent prevention function, an electrolyte holding function, and a separator shape maintenance (stiffness improvement) function can be provided.

  The plurality of positive electrode plates 101 and negative electrode plates 103 are alternately stacked via separators 102 to form an electrode stack 108. Each positive electrode plate 101 is connected to the positive electrode terminal 104 via the positive electrode side current collector 101a, while each negative electrode plate 103 is connected to the negative electrode terminal 105 via the negative electrode side current collector 103a. ing.

  In addition, the number of positive electrode plates, separators, and negative electrode plates constituting the electrode laminate can be arbitrarily set as necessary. For example, one positive electrode plate, one separator, and one negative electrode An electrode laminated body can also be comprised with a board.

  The positive electrode terminal 104 is a plate-like member made of an electrochemically stable metal material. Although it does not specifically limit as a material which comprises this positive electrode terminal 104, Aluminum, aluminum alloy, copper, or nickel etc. can be mentioned similarly to the above-mentioned positive electrode side electrical power collector 101a, for example.

  The negative electrode terminal 105 is also a plate-like member made of an electrochemically stable metal material. Although it does not specifically limit as a material which comprises this negative electrode terminal 105, Nickel, copper, stainless steel, or iron can be mentioned similarly to the above-mentioned negative electrode side collector 103a, for example.

  In this embodiment, the electrode plates 101 and 103 and the electrode terminals 104 and 105 are connected by extending the metal foil itself constituting the current collectors 101a and 103a to the electrode terminals 104 and 105. The present invention is not particularly limited to this, and the electrode plates 101 and 103 and the electrode terminals 104 and 105 may be connected via a member different from the metal foil constituting the current collectors 101a and 103a.

  As shown in FIGS. 1 and 2, the upper exterior member 106 is formed of a resin-metal thin film laminate material in which a concave first cup portion 1061 is formed in advance. As shown in FIG. 3, the upper exterior member 106 includes three layers: an inner layer 106a, an intermediate layer 106b, and an outer layer 106c.

  The inner layer 106a is made of, for example, a resin film having excellent electrolytic solution resistance and heat fusion properties, such as polyethylene, modified polyethylene, polypropylene, modified polypropylene, or ionomer. The intermediate layer 106b is made of a metal foil such as aluminum. The outer layer 106c is made of, for example, a resin film excellent in electrical insulation, such as a polyamide resin or a polyester resin.

  As shown in FIGS. 1 and 2, the lower exterior member 107 is also formed of a resin-metal thin film laminate material in which a concave second cup portion 1071 is formed in advance. In the same manner as above, it has a three-layer structure including an inner layer, an intermediate layer, and an outer layer.

  In order to maintain the sealing performance inside the thin battery 10, a seal film made of, for example, polyethylene or polypropylene is interposed between the electrode terminals 104 and 105 and the exterior members 106 and 107. Also good. It is preferable from the viewpoint of heat-sealability that this seal film is made of the same system as the synthetic resin material constituting the inner layer of the exterior members 106 and 107 in both the positive electrode terminal 104 and the negative electrode terminal 105.

  In the present embodiment, as shown in FIG. 2, a direction in which the electrode terminals 104 and 105 are led out from the bottom surface 1062 of the first cup portion 1061 of the upper exterior member 106 (hereinafter, simply referred to as “terminal lead-out direction”). Is longer than the length L4 along the terminal lead-out direction on the bottom surface 1072 of the second cup portion 1071 of the lower exterior member 107 (L2> L4). The length L4 is slightly longer than the length L1 along the terminal lead-out direction in the electrode laminate 108 so that the electrode laminate 108 can be accommodated (L4> L1).

  Further, as shown in the figure, the length L3 along the terminal lead-out direction at the opening periphery of the first cup portion 1061 is longer than the length L5 along the terminal lead-out direction at the opening periphery of the second cup portion 1071. It is longer (L3> L5).

  In the present embodiment, the cup portions 1061 and 1071 are formed so as to satisfy the following conditional expression (1).

R1> R2 (1)
However, in the above conditional expression (1), R1 is the side of the side 1063 of the first cup portion 1061 from which the electrode terminal leads (hereinafter simply referred to as “terminal lead-out side”) and the first cup portion. This is the radius of the curved surface formed between the bottom surface 1062 of 1061 (see FIG. 3). R2 is a radius of a curved surface formed between the terminal lead-out side surface of the side surface 1073 of the second cup portion 1071 and the bottom surface 1072 of the second cup portion 1071 (not shown).

  By forming the cup portions 1061 and 1071 so as to satisfy the conditional expression (1), a cup portion having a large size (the first cup portion 1061 in the present embodiment) can be obtained at the time of decompression in the production process of the secondary battery. , It becomes easier to be crushed than a small cup part (second cup part 1071 in this embodiment).

  Furthermore, in this embodiment, each cup part 1061, 1071 is formed so that the following conditional expression (2) may be satisfy | filled.

θ1> θ2 (2)
However, in the conditional expression (2), θ1 is an angle formed by the terminal lead-out side surface of the side surface 1063 of the first cup portion 1061 with respect to the bottom surface 1062 of the first cup portion 1061 (see FIG. 3). ). On the other hand, θ2 is an angle formed by the terminal lead-out side surface of the side surface 1073 of the second cup portion 1071 with respect to the bottom surface 1072 of the second cup portion 1071 (not shown).

  By forming the cup portions 1061 and 1071 so as to satisfy the conditional expression (2), the first cup portion 1061 having a larger size is replaced with the second cup having a smaller size at the time of decompression in the production process of the secondary battery. It becomes easier to be crushed than the portion 1071.

  Note that the conditional expressions (1) and (2) can easily collapse the first cup portion 1061 by satisfying any one of the conditional expressions. Although not essential, satisfying both conditions makes the first cup portion 1061 more easily crushed.

  In the present embodiment, the first cup portion 1061 of the upper exterior member 106 is formed so as to satisfy the following conditional expression (3).

90 ° <θ1 <115 ° (3)
When the angle θ1 is 90 ° or less, when the first cup portion 1061 is crushed by decompression, the side surface 1063 does not fall down sufficiently and remains in a protruding shape. Further, when the angle θ1 is larger than 115 °, the inclination of the side face 1063 of the first cup portion 1061 becomes excessively large, and a space that allows expansion of the volume when gas is generated inside the battery becomes unnecessarily large. .

  The exterior members 106 and 107 configured as described above enclose the electrode laminate 108, a part of the positive terminal 104, and a part of the negative terminal 105.

  At this time, the respective cup portions 1061 and 1071 are opposed to each other, and the electrode stack 108 is accommodated in the opposed cup portions 1061 and 1071, but as shown in FIGS. 2 and 4A, the second cup portion The terminal lead-out side of the bottom surface 1072 of 1071 is positioned inside the battery with respect to the terminal lead-out side of the bottom surface 1062 of the first cup portion 1061. Further, as shown in the figure, the terminal lead-out side of the opening periphery of the second cup portion 1071 is positioned inside the battery with respect to the terminal lead-out side of the opening periphery of the first cup portion 1061.

  As described above, since the space between the second cup portion 1071 and the electrode stack 108 is narrowed by positioning the second cup portion 1071 on the battery inner side than the first cup portion 1061, The distortion generated in the second cup portion 1071 is reduced, and the accuracy of the lead-out positions of the electrode terminals 104 and 105 can be improved.

  On the other hand, by positioning the first cup portion 1061 on the outer side of the battery than the second cup portion 1071, as shown in FIG. 4B, a space that allows volume expansion when gas is generated inside the battery is provided. Since it can be ensured between the first cup portion 1061 and the electrode laminate 108, the life of the thin battery 10 can be extended.

  Then, a liquid electrolyte having a lithium salt such as lithium perchlorate, lithium borofluoride, and lithium hexafluorophosphate as a solute is injected into the organic liquid solvent into the space formed by the cup portions 1061 and 1071. Then, the outer peripheral edges of the exterior members 106 and 107 are heat-sealed by hot pressing. As a result, the electrode laminate 108 and part of the electrode terminals 104 and 105 are accommodated in the exterior members 106 and 107 and sealed.

  Examples of the organic liquid solvent include ester solvents such as propylene carbonate (PC), ethylene carbonate (EC), dimethyl carbonate (DMC), and methyl ethyl carbonate. The organic liquid solvent of the present invention is not limited to this, and an organic liquid solvent prepared by mixing and preparing an ether solvent such as γ-butylactone (γ-BL) or dietoshietane (DEE) in an ester solvent. It can also be used.

  The embodiment described above is described in order to facilitate understanding of the present invention, and is not described in order to limit the present invention. Therefore, each element disclosed in the above embodiment is intended to include all design changes and equivalents belonging to the technical scope of the present invention.

  Below, the effect of the present invention was confirmed by examples and comparative examples that further embody the present invention. The following examples and comparative examples are for confirming the effects of the thin battery according to the above-described embodiment.

Example 1
A powder obtained by mixing graphite and polyvinylidene fluoride (PVDF) with spinel type lithium manganese oxide is dispersed in N-methyl-2-pyrrolidone (NMP) to form a slurry. After coating and drying, a positive electrode plate was prepared by compression and cutting. In addition, it was set as the lead part for connecting a positive electrode plate to a positive electrode terminal, without apply | coating a slurry to a part of aluminum foil.

  Further, a powder obtained by mixing non-graphitizable carbon and polyvinylidene fluoride (PVDF) is dispersed in N-methyl-2-pyrrolidone (NMP) to form a slurry, and this slurry is used as both main parts of a copper foil having a thickness of 10 μm. After coating on the surface and drying, compression and cutting were performed to prepare a negative electrode plate. Note that the slurry was not applied to a part of the copper foil, and a lead portion for connecting the negative electrode plate to the negative electrode terminal was used.

  The positive electrode plate and the negative electrode plate thus produced were alternately laminated while sandwiching a separator between them to form an electrode laminate. A microporous polyethylene film having a thickness of 25 μm was used as the separator. The size of the electrode laminate was 200 mm in length (L1) × 120 mm in width × 6 mm in height.

  Each positive current collector extending from the electrode laminate was welded to the positive terminal, and each negative current collector extending from the laminate was welded to the negative terminal. An aluminum foil having a thickness of 100 μm was used as the positive electrode terminal. A nickel foil having a thickness of 100 μm was used as the negative electrode terminal.

  Next, the electrode laminated body connected to the electrode terminal is accommodated between the cup portions of the two exterior members, and a part of the electrode terminal is led out from the outer peripheral edge, and the short side of the exterior member After heat-sealing a total of three sides, the two sides and one side of the long side, and injecting both electrolytes through the opening, the remaining one side is heat-sealed in a state where the space formed by the exterior member is decompressed Thus, a battery sample of Example 1 was produced.

  The upper exterior member and the lower exterior member have a three-layer structure in which an inner layer is a nylon layer having a thickness of 15 μm, an intermediate layer is an aluminum alloy layer having a thickness of 40 μm, and an outer layer is a polypropylene layer having a thickness of 45 μm. A resin-metal thin film laminate was used.

  The length L2 along the terminal lead-out direction at the bottom surface of the first cup portion of the upper exterior member was formed to be 12 mm longer than the length L1 of the electrode laminate (L2 = L1 + 12 mm). In contrast, the length L4 along the terminal lead-out direction on the bottom surface of the second cup portion of the lower exterior member was formed to be 2 mm longer than the length L1 of the electrode stack (L4 = L1 + 2 mm).

  Further, the radius R1 of the curved surface formed on the peripheral edge of the bottom surface of the first cup portion of the upper exterior member was 1 mm. Furthermore, the angle θ1 formed by the side surface with respect to the bottom surface of the first cup portion was 110 °.

As the electrolytic solution, a solution obtained by dissolving lithium hexafluorophosphate (LiPF ₆ ) as a supporting electrolyte in a mixed solvent of propylene carbonate (PC), ethylene carbonate (EC) and diethyl carbonate (DEC) was used.

  The following terminal lead position accuracy was evaluated for 10 battery samples of Example 1.

  In the evaluation of the terminal lead-out position accuracy, the amount of deviation Δh of the electrode terminal with respect to the center in the thickness direction of the thin battery before and after decompression was determined by the following equation (4).

_{Δh = h a / 2-h} b -t / 2 ... (4)
However, in the above (1), as shown in FIG. 5, h _a is the total thickness of the thin battery, h _b is the height of the electrode terminal from the bottom surface of the thin battery, t is the electrode terminals thickness That's it.

  The ratio (Δh2 / Δh1) was calculated with Δh1 being the amount of deviation of the electrode terminals before decompression and Δh2 being the amount of deviation of the electrode terminals after decompression. As the ratio is closer to 1, the electrode terminal is led out from the same position before and after the decompression, so that the accuracy of the terminal lead-out position is evaluated as being excellent.

  In addition, the battery life of the five battery samples of Example 1 was evaluated as follows.

  In the evaluation of the battery life, the following charge / discharge cycle test was performed. In this charge / discharge cycle test, a charge / discharge cycle consisting of two steps of charge and discharge is repeated 1000 times in an environment of 50 ° C., and the capacity of the thin battery before and after the charge / discharge cycle is compared to maintain the capacity. The rate was calculated, and it was evaluated that the battery life was longer as the capacity maintenance rate was closer to 100%.

  In the charge step of the charge / discharge cycle, charging was performed at a current value of 1 CA, and the charging was stopped when the voltage value reached 4.2V. In contrast, in the discharging step of the charge / discharge cycle, discharging was performed at a current value of 1CA, and discharging was stopped when the voltage value reached 2.5V.

Table 1 shows the results of terminal lead position accuracy and battery life evaluation in Example 1.

Comparative Example 1
In Comparative Example 1, the length L4 along the terminal lead-out direction on the bottom surface of the second cup portion of the lower exterior member was formed to be 12 mm longer than the length of the electrode stack (L4 = L1 + 12 mm). That is, the first cup portion of the upper exterior member and the second cup portion of the lower exterior member have the same size. Otherwise, a battery sample was produced under the same conditions as in Example 1.

  The terminal lead position accuracy was evaluated for the 10 battery samples of Comparative Example 1 under the same conditions as in Example 1. Further, the battery life of the five battery samples of Comparative Example 1 was evaluated under the same conditions as in Example 1.

  Table 1 shows the results of the terminal lead position accuracy and battery life table of Comparative Example 1.

Comparative Example 2
In Comparative Example 2, the length L2 along the terminal lead-out direction on the bottom surface of the first cup portion of the upper exterior member was formed to be 2 mm longer than the length of the electrode stack (L2 = L1 + 2 mm). That is, the first cup portion of the upper exterior member and the second cup portion of the lower exterior member have the same size. Otherwise, a battery sample was produced under the same conditions as in Example 1.

Discussion As shown in Table 1, the battery sample of Example 1 was good in both terminal lead position accuracy and battery life.

  As shown in the table, the battery of Comparative Example 1 was inferior in terminal lead position accuracy as compared with Example 1 and Comparative Example 2. This is presumably because both cup parts of the exterior member were too large for the electrode laminate, and the cup part was distorted before and after decompression, and the lead-out position of the electrode terminal varied.

  As shown in the table, the battery of Comparative Example 2 was inferior in battery life as compared with Example 1 and Comparative Example 1. This is because both cup parts of the exterior member are approximately the same size as the electrode laminate, so that a sufficient space for volume expansion due to the gas generated inside the battery is not secured, and the gas causes the gap between the electrode plates. This is thought to be due to the occurrence of locations where the distances of the lines were not uniform and could not react locally.

FIG. 1 is a plan view showing a thin battery according to an embodiment of the present invention. FIG. 2 is a schematic cross-sectional view taken along the line II-II in FIG. FIG. 3 is an enlarged cross-sectional view of a portion III in FIG. FIG. 4A is an enlarged cross-sectional view of the terminal lead-out portion, showing a state before decompression. FIG. 4B is an enlarged cross-sectional view of the terminal lead-out portion, showing a state after decompression. FIG. 5 is an enlarged cross-sectional view of a terminal lead-out portion for explaining h _a , h _b and t in the embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Thin battery 101 ... Positive electrode plate 101a ... Positive electrode side collector 101b, 101c ... Positive electrode layer 102 ... Separator 103 ... Negative electrode plate 103a ... Negative electrode side collector 103b, 103c ... Negative electrode layer 104 ... Positive electrode terminal 105 ... Negative electrode terminal 106 ... Upper exterior member 106a ... Inner layer 106b ... Intermediate layer 106c ... Outer layer 1061 ... First cup portion 1062 ... Bottom surface 1063 ... Side surface 107 ... Lower exterior member 1071 ... Second cup portion 1072 ... Bottom surface 1073 ... Side surface 108 ... Electrode Laminated body

Claims (5)

An electrode laminate in which electrode plates are alternately laminated via separators;
Sheet-like first and second exterior members each having first and second cup portions formed in a concave shape;
An electrode terminal connected to the electrode plate,
The first and second cup portions are opposed to each other, the electrode stack is accommodated therein, and the electrode terminals are led out from outer peripheral edges of the first and second exterior members, and the first And a secondary battery in which the electrode laminate is sealed in the first and second cup portions by joining outer peripheral edges of the second exterior member,
A secondary battery in which a terminal lead-out side of the bottom surface of the second cup part is located on the inner side of the battery than a terminal lead-out side of the bottom surface of the first cup part.   2. The secondary battery according to claim 1, wherein a side on the terminal lead-out side in the opening periphery of the second cup portion is located on the inner side of the battery than a side on the terminal lead-out side in the opening periphery of the first cup portion. The secondary battery according to claim 1 or 2, wherein the following conditional expression (1) is satisfied.
R1> R2 (1)
However, in the conditional expression (1), R1 is a radius of a curved surface formed between the terminal lead-out side surface and the bottom surface of the first cup portion on the side surface of the first cup portion, and R2 Is the radius of the curved surface formed between the terminal lead-out side surface of the side surface of the second cup portion and the bottom surface of the first cup portion. The secondary battery according to any one of claims 1 to 3, wherein the following conditional expression (2) is satisfied.
θ1> θ2 (2)
However, in the conditional expression (2), θ1 is an angle formed by the terminal lead-out side surface of the side surface of the first cup portion with respect to the bottom surface of the first cup portion, and θ2 is the first The angle formed by the terminal lead-out side surface of the side surface of the second cup portion with respect to the bottom surface of the second cup portion. The secondary battery according to claim 1, wherein the following conditional expression (3) is satisfied.
90 ° <θ1 <115 ° (3)
However, in the conditional expression (3), θ1 is an angle formed by the terminal lead-out side surface of the side surface of the first cup portion with respect to the bottom surface of the first cup portion.

Images