JP2005310577A - Coin type secondary battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a coin type secondary battery which comprises an electrode group adopting a laminate structure, suppresses the occurrence of a minute short circuit at the final stage of charge and discharge, exhibits high reliability even in a use for a long period of time, is superior in charge and discharge cycle characteristics, and also superior in reliability. <P>SOLUTION: The coin type secondary battery comprises an electrode group in which a plurality of positive electrode plates and negative electrode plates are laminated alternately through a separator, and the electrode group is housed together with an non-aqueous electrolytic solution in a battery container which is caulked and sealed by a shallow bottomed case serving also as a positive electrode terminal and a sealing case serving as a negative electrode terminal through an insulating gasket. The electrode group is structured by locating the negative electrode plate at the lamination lower end and the lamination upper end. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a coin-type secondary battery that includes an electrode group adopting a winding structure for the purpose of improving high-load discharge characteristics and is housed in a flat battery case.

  Coin-type batteries, also called button-type batteries and flat-type batteries, are small and thin, so if you need to make them smaller, such as wristwatches or hearing aids, or thin like IC cards. Widely used in In addition, by crimping the periphery of the flat battery container, the inside of the container can be securely sealed so that the battery productivity is increased and at the same time it has high reliability and has a huge production scale. Yes.

  The internal structure of the coin-type battery is such that a positive electrode pellet and a negative electrode pellet face each other at 1: 1. In this structure, the continuous discharge current is at most about 10 mA due to factors such as a small reaction area between the positive electrode and the negative electrode, and there is a problem that it can be applied only to a device with a small load current. In order to increase the discharge current, it is necessary to increase the counter electrode area between the positive electrode plate and the negative electrode plate. In a cylindrical battery or a square battery housed in a bottomed cylindrical battery case, a laminated structure in which a plurality of positive electrode plates and negative electrode plates are stacked via a separator, or a belt-like positive electrode plate and negative electrode plate A structure for increasing the reaction area is widely used by adopting a winding structure in which a separator is wound between the two in a spiral shape.

In such a technical background, the present inventors propose to improve the discharge characteristics of a coin-type battery by accommodating a wound electrode group in a flat battery container in order to solve the above problems. (Patent Document 1). This coin-type battery is made of a strip-shaped electrode plate in which laminated parts and connecting pieces are alternately formed, and constitutes an electrode group having a structure in which these electrode plates are wound to improve the discharge characteristics at a large current. Battery. In addition, by adopting a flat battery container, the thickness of the battery can be reduced, and the battery can be made thinner than the conventional rectangular battery. In addition, the use of a caulking seal increases battery productivity and at the same time realizes high reliability.
International Publication No. 02/013305 Pamphlet

The present inventors have studied for mass production of the coin-type battery proposed in Patent Document 1. For example, when a coin-type non-aqueous electrolyte secondary battery using a lithium transition metal oxide as a positive electrode and a carbon material as a negative electrode was produced, it was confirmed that a micro short circuit is likely to occur at the end of a cycle where charge and discharge are repeated. Furthermore, as a result of earnest verification of the mechanism of occurrence of the micro short circuit by the present inventors, it was confirmed that the micro short circuit was caused by precipitation of lithium released from the positive electrode during charging. This lithium deposition occurs remarkably on the negative electrode surface arranged on the most bottomed case side, and a micro short circuit occurs between the deposited lithium and the bottomed case and the positive electrode facing the deposition site. And as a result of carrying out the detailed examination about the generation | occurrence | production effect | action of lithium precipitation, the following knowledge was acquired. That is, the positive electrode capacity exceeds the negative electrode capacity in the vicinity of the electrode group facing the bottomed case, and excessive lithium ions that cannot be occluded on the negative electrode side during charging are deposited. In particular, in a coin-type battery that employs a flat battery container, the battery volume is small and the amount of electrolyte is small, so the tendency to inhibit lithium ion migration is prominent and lithium precipitation is likely to occur. It becomes a situation. The present inventors have also confirmed the same lithium deposition in nonaqueous electrolyte secondary batteries using other electrode materials, and this lithium deposition is peculiar to the configuration in which the electrode group is housed in a flat battery container. I found out that this is a problem.

  The micro short circuit due to lithium deposition as described above is particularly likely to occur at the end of cycle use of a battery in which a charge / discharge cycle is repeated, and causes a sharp deterioration in discharge characteristics, thus greatly reducing the long-term reliability of the battery. It becomes a factor. In particular, coin-type batteries mainly used for device memory backup and the main power source of small portable devices are required to have higher reliability than the device side, and deterioration of discharge characteristics at the end of use may have a significant impact on the device. There is.

  On the other hand, in the coin-type battery adopting the structure proposed in Patent Document 1, the number of steps for winding the belt-like positive and negative electrode plates increases, so that the productivity is higher than that of the conventional battery using the electrode plate on the pellet. It will cause a decline. Furthermore, in the electrode group in which the number of windings of the electrode plate is increased for the purpose of increasing the battery capacity and improving the discharge characteristics, the electrode plate is liable to be displaced as the number of windings increases. There was a problem that the positional accuracy of the lowering. Therefore, in order to suppress the occurrence of winding misalignment during the winding process, the present inventors have taken measures to ensure that no winding misalignment occurs after placing a separator between the positive and negative electrode plates. I came. However, it is difficult to avoid a decrease in the winding speed, and there is a possibility that the productivity is further deteriorated in the electrode group in which the number of windings is increased. In view of the above situation, the present inventors have studied from both aspects of discharge characteristics and battery capacity characteristics and productivity required for the battery, and formed an electrode group in which a plurality of positive and negative electrode plates are laminated into a flat battery container. The conclusion that the case where the structure accommodated in the case is preferable is also assumed.

  The present invention relates to a coin-type secondary battery in which an electrode group in which a plurality of electrode plates are alternately stacked is housed in a flat battery container, and a coin with improved reliability by suppressing lithium deposition at the end of cycle use A secondary battery is provided.

  In order to achieve the above object, a coin-type secondary battery of the present invention includes an electrode group in which a plurality of positive electrode plates and negative electrode plates are alternately stacked via separators, and the electrode group is used together with a non-aqueous electrolyte. It has a structure that is housed in a battery case that is caulked and sealed through an insulating gasket by a shallow bottom case that also serves as a positive electrode terminal and a sealing case that also serves as a negative electrode terminal. The electrode plate is positioned.

  That is, the electrode group of the coin-type secondary battery according to the present invention has n positive electrode plates and n + 1 negative electrode plates alternately stacked via separators, and is the electrode group located on the most bottomed case side. The negative electrode plate is used for the electrode plate arranged at the lower end of the laminate and the electrode plate arranged at the upper end of the laminate of the electrode group arranged closest to the sealing case. The electrode group made into the form which inserts | pinches is comprised. And this electrode group is accommodated in the inside of the battery container formed by crimping with an insulating gasket by the shallow bottom case which also serves as a positive electrode terminal and the sealing case which also serves as a negative electrode terminal with a nonaqueous electrolyte.

  In the description of the present specification including the detailed description of the present invention, a coin-type secondary battery is combined with a half-shell bottomed case, and a flat battery container sealed by caulking through a gasket is used. This means a secondary battery containing an electrode group comprising a combination of positive and negative electrodes capable of discharging, and the bottom shape of the case may be circular, elliptical, or rectangular.

  According to the configuration of the present invention, any positive electrode plate is in a state where both surfaces thereof face the negative electrode plate, and in particular, there is no positive electrode plate between the bottomed case that also serves as the positive electrode terminal and the negative electrode plate. Become. For this reason, active material does not precipitate between the positive electrode case and the negative electrode plate even at the end of the cycle life of the battery with repeated charge / discharge cycles, and the occurrence of minute short-circuiting due to the precipitation is greatly increased. Therefore, the reliability of the battery is greatly increased.

  Further, in the coin-type battery of the present invention, the positive electrode plate and the negative electrode plate are provided with a positive electrode metal lead and a negative electrode metal lead led out from each end, and each of the metal leads is drawn out in the same direction as the positive electrode and the negative electrode. Are connected to each other. According to this configuration, by connecting the metal leads drawn out from the positive and negative electrode plates, electrical connection is made between the positive and negative electrode plates. Furthermore, by connecting each of these positive and negative metal leads to each of the positive and negative electrode connecting pieces, or directly connecting these metal leads to a bottomed case and a sealing case that also serve as positive and negative electrode terminals, an electrode group Are connected to the battery case. By pulling out the metal leads of these positive and negative electrodes in directions opposite to each other, a physical distance between the metal leads can be secured, and contact between the metal leads can be reliably prevented.

  Further, each connecting piece for connecting each metal lead of the positive and negative electrodes and the battery container, or each metal lead of the positive and negative electrodes is housed in the battery container in a state of being folded back in the direction opposite to the drawing direction of the metal leads. If it is this structure, the lead | read | reed or connection piece used as the form pulled out from the electrode group can be connected to a battery container by welding, and since electrical connection is made | formed reliably, the reliability of a battery is improved greatly. In addition, it is preferable to replace the metal leads drawn from the electrode group with positive and negative metal leads. Specifically, in each of the positive and negative electrodes, one metal lead (hereinafter referred to as a “connecting metal lead”) is set long to the other metal lead, the other metal lead is connected to this connecting metal lead, and the connecting metal lead The electrode group and the battery container are electrically connected by connecting the end part to the battery container. According to this configuration, the connection piece is not required, and the configuration of the electrode group can be simplified.

  Further, in the coin-type battery of the present invention, the negative electrode plate has a double-sided electrode plate in which the electrode material is applied to both surfaces of the metal foil core material, and the electrode material is applied only to one surface of the metal foil core material. It has two types of electrode plates, a single-side coated electrode plate formed by exposing a metal foil core material on the surface, and the single-side coated electrode plate is positioned at the upper end of the stack of electrodes, and the lower end of the stack. The other surface where the foil core material is exposed is arranged to face the sealing case and the bottomed case.

  By forming this single-side coated electrode plate and placing it on the upper and lower ends of the electrode group, the contribution rate to the discharge reaction occupying the volume of the electrode group by optimizing the electrode material coating site The ratio of the active material having a high value can be increased, and the discharge capacity per unit volume of the electrode group is increased.

  Furthermore, the coin-type battery of the present invention has an insulating sheet disposed between the electrode group and a bottomed case that also serves as a positive electrode terminal. According to this configuration, the insulation between the negative electrode plate disposed at the lower end of the stacked electrode group and the bottomed case that also serves as the positive electrode terminal is ensured, and an insulating member that covers the outer peripheral surface of the electrode group, for example, Even if the outer covering of the electrode group by the separator is damaged, the insulation between the negative electrode plate and the bottomed case can be reliably maintained. This configuration is an important factor for enhancing the reliability of various safety mechanisms, for example, a coin-type secondary battery in which a blocking mechanism in a sealing plate and a PTC element cannot be practically arranged.

  As described above, according to the present invention, the cycle characteristics of the battery are greatly improved by suppressing the occurrence of minute short-circuits due to the precipitation of the active material in the coin-type battery and maintaining the charge / discharge characteristics over a long period of time. Thus, a coin-type battery with improved battery reliability can be obtained.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings for understanding of the present invention. The following embodiment is an example embodying the present invention, and does not limit the technical scope of the present invention.

  The coin-type battery according to the present embodiment shows an example configured as a lithium ion secondary battery, and the coin-type battery A according to the first embodiment has a shallow bottom as shown in a sectional view in FIG. A cylindrical (half-shell) battery can 2 (bottomed case) and a battery container 2 having a laminated structure in which the opening is sealed by a sealing plate 4 (sealing case) via a gasket 3. A battery that accommodates the electrode group 1 and has a coin-shaped appearance is configured.

  As shown in a plan view in FIG. 2, the electrode group 1 is formed in a substantially circular plane shape with little useless space in a circular space formed by the battery can 2 and the sealing plate 4. Therefore, a battery having a large volumetric energy density with a large discharge capacity per battery volume can be formed. The electrode group 1 is formed by alternately stacking positive electrode plates 5 shown in FIG. 3A and negative electrode plates 6 shown in FIG. 3B through separators 7 as shown in FIG. It is formed. In FIG. 1, the positive electrode plate 5 is sandwiched between the negative electrode plates 6, and the upper end portion of the electrode group 1 located on the sealing plate 4 side and the electrode group 1 located on the battery can 2 side. A negative electrode plate 6 is disposed at the lower end of the stack. The electrode group 1 formed by laminating positive and negative electrode plates is connected to the battery can 2 and the sealing plate 4 by metal leads (not shown) derived from the respective electrodes.

  The positive electrode plate 5 constituting the electrode group 1 is coated with a positive electrode material on both surfaces of a current collector formed of aluminum foil, and an arc is formed in the width direction as shown in FIG. It has a positive electrode plate surface 5a formed and a positive electrode metal lead 5b made of an aluminum foil extended from the electrode plate surface. Further, the negative electrode plate 6 is formed by applying a negative electrode material to a current collector formed of a copper foil, and, as shown in FIG. It has the negative electrode metal lead 6b which consists of copper foil extended from the plate surface.

  As shown in FIG. 3, the width of the electrode plate surfaces of the negative electrode plate 6 and the positive electrode plate 5 is Wb> Wa, and the length of the electrode plate surface is Lb> La. Thus, by forming the width and length of the negative electrode plate 6 larger than that of the positive electrode plate 5, even when a positional deviation occurs between the opposing positions of the positive electrode plate 5a and the negative electrode plate surface 6a. The positive electrode plate surely faces the negative electrode plate.

  The positive electrode plate 5 and the negative electrode plate 6 are laminated such that the positive electrode plate surface 5 a and the negative electrode plate surface 6 a face each other with a separator 7 as shown in a schematic diagram in FIG. 4. Further, the positive metal lead 5b is drawn leftward in FIG. 3, and the negative metal lead 6b is drawn rightward. These metal leads are integrated by welding at a position facing the side surface of the electrode group, and are connected to the battery container by a method described later.

  Moreover, you may form a single-sided coated electrode plate by making one surface of a negative electrode plate uncoated in FIG.3 (b). This single-side coated electrode plate is disposed at the upper end of the stack of the electrode group 1 and the lower end of the stack, and the uncoated portion is disposed on the outer peripheral side of the electrode group 1 so as to face the inner surface of the battery container. The main surface of the electrode group 1 can be in a state where the negative electrode current collector is exposed. In this state, the negative electrode region that does not face the positive electrode plate 5 and contributes little to the electromotive reaction is uncoated, thereby increasing the volumetric efficiency by improving the volume efficiency. Is.

Further, the separator 7 is obtained by punching a microporous polyethylene film into positive and negative electrode plates. Specifically, the negative electrode plate 6 is previously punched into a rectangular shape having a width and a length dimension on each side, laminated together with the positive electrode plate 5 and the negative electrode plate 6, and then cut off unnecessary portions, thereby forming a disk shape. Electrode group 1 is formed. Further, the separator 7 also covers the outer periphery of the electrode group 1 to prevent the metal lead and the electrode plate from coming into direct contact. More preferably, by disposing a resin material between the negative electrode plate 6 and the positive electrode metal lead 5b located at the lower end of the stack of the electrode group 1 in FIG. 4, the negative electrode plate 6 and the positive electrode metal lead 5b having a positive electrode potential. By increasing the insulation, it is possible to reliably insulate even if protrusions such as burrs occur on the positive electrode metal lead 5b, thereby greatly increasing the reliability of the battery.

  In order to integrate each metal lead extended from each of the positive electrode plate 5 and the negative electrode plate 6, the length of each metal lead needs to be longer as the electrode plate is farther from the place where welding is performed. is there. Specifically, the positive electrode plate 5 has a larger metal lead length as the electrode plate is laminated on the upper portion, and the negative electrode plate 6 has a larger metal lead length as the electrode plate is laminated on the lower portion. These metal leads are integrated by welding at a position facing the peripheral surface of the electrode group 1, and each integrated metal lead is connected to the battery can 2 and the sealing plate 4 through a connection piece. Furthermore, it is good also as a structure connected to the battery can 2 and the sealing board 4 with the metal lead for connection extended from one electrode plate instead of the said connection piece. In this configuration, as shown in FIG. 4, the negative electrode metal lead 6b extended from the other negative electrode plate 6 is connected to the negative electrode connecting metal lead 6c extended from the negative electrode plate 6 located at the uppermost end. The negative electrode connecting metal lead 6c is directly connected to the sealing plate 4 serving also as the negative electrode terminal. On the other hand, for the positive electrode, the positive electrode metal lead 5b extended from the other positive electrode plate 5 is connected to the positive electrode connection metal lead 5c extended from the positive electrode plate 5 located at the lowest end, and for positive electrode connection. The metal lead 5c is directly connected to the battery can 2 that also serves as a positive electrode terminal. These direct connection methods are as follows.

  In the electrode group 1 having the configuration shown in FIG. 4, the tip of the positive electrode connecting metal lead 5 c is welded to the inner surface of the battery can 2, and the tip of the negative electrode connecting metal lead 6 c is welded to the inner surface of the sealing plate 4. . The metal lead 5c for positive electrode connection welds aluminum to the battery can 2 since an aluminum foil is applied as a positive electrode current collector when lithium cobaltate or the like is used as a positive electrode active material. However, since the battery can 2 is generally made of stainless steel, it is not easy to weld aluminum to stainless steel. Therefore, the battery can 2 in the present embodiment is formed of a clad material whose inner surface side is aluminum and whose outer surface side is stainless steel. With the configuration of the battery can 2, the positive electrode connecting metal lead 5 c is welded between aluminum, and ultrasonic welding is applied to ensure the welding of the aluminum foil. On the other hand, since the copper lead is applied to the negative electrode connecting metal lead 6c as the negative electrode current collector, the lead 6c can be joined to the stainless sealing plate 4 by resistance welding.

  In the electrode group 1 having the above-described configuration, the negative electrode connecting metal lead 6 c is welded to the sealing plate 4, and the positive electrode connecting metal lead 5 c is welded to the battery can 2. 2 is accommodated. A coin-shaped battery is formed by injecting an electrolyte solution and sealing the opening of the battery can 2 with a sealing plate 4 via a gasket 3. The battery can 2 has a positive terminal and the sealing plate 4 has Insulated with gasket 3 so as to be a negative electrode terminal.

  Next, the battery A having the coin-shaped appearance described in the present embodiment, and the positive electrode plate 5 and the negative electrode plate 6 as the same number as a comparative example, and an electrode group in which these electrode plates are alternately stacked are provided. The comparative example of the comparative battery B is shown below. Here, the configuration of the battery A and the comparative battery B is a comparison in the case of forming a coin-type battery having a diameter of 30 mm and a thickness of 3.2 mm.

(1) Production of Battery A In Battery A, the positive electrode plate 5 was produced as follows. That is, 3 parts by weight of polyvinylidene fluoride was dissolved in 38 parts by weight of N-methylpyrrolidone on both sides of an aluminum foil having a thickness of 20 μm, and 50 parts by weight of LiCoO ₂ as an active material and 9 parts by weight of graphite as a conductive agent were added thereto. The positive electrode material mixed and dispersed under an inert atmosphere was applied to the uniform thickness in the air, dried at 120 ° C. for 1 hour, and then rolled to a thickness of 180 μm. It was punched into the shape shown in FIG.

The negative electrode plate 6 is inert by dissolving 3 parts by weight of polyvinylidene fluoride in 38 parts by weight of N-methylpyrrolidone on both sides of a copper foil having a thickness of 15 μm, and adding 59 parts by weight of a 2500 ° C. baked product of coke. The negative electrode material mixed and dispersed in the atmosphere was applied to the uniform thickness in the air, dried at 120 ° C. for 1 hour, and then rolled to a thickness of 165 μm. Punched into the shape shown in b).

The positive electrode plate 5 and the negative electrode plate 6 having the above-described configuration are laminated as shown in FIG. 4 through a microporous polyethylene film having a thickness of 25 μm to form an electrode group 1 having a thickness of about 2.4 mm. The tip of the positive electrode metal lead 5 b was ultrasonically welded to the inner surface of the battery can 2, and the tip of the negative electrode metal lead 6 b was resistance welded to the inner surface of the sealing plate 4. This electrode group 1 was accommodated in a battery can 2, 400 μl of LiPF ₆ / EC-EMC electrolyte was injected, and the opening of the battery can 2 was sealed with a sealing plate 4 via a gasket 3.

(2) Production of Comparative Battery B In the comparative battery B, the same positive and negative electrode materials as the same battery A were used for the positive electrode plate 5 and the negative electrode plate 6. The positive electrode plate 5 is applied to both surfaces of an aluminum foil having a thickness of 20 μm with a positive electrode material having an even thickness in the air, dried at 120 ° C. for 1 hour, and then rolled to a thickness of 135 μm. The electrode plate material was punched into the shape shown in FIG. On the other hand, the same negative electrode plate 6 as that of the battery A was used. In Comparative Battery B, the number of positive and negative electrodes stacked was the same, and in Comparative Battery B, 6 sheets were used each. The positive electrode plate 5 and the negative electrode plate 6 are alternately laminated through a microporous polyethylene film having a thickness of 25 μm, and the negative electrode plate 6 is disposed at the upper end and the positive electrode plate 5 is disposed at the lower end. Formed in Group 1. The other structure, that is, the connection method of the metal lead or the like is the same as that of the battery A, the electrode group 1 is accommodated in the battery can 2, 400 μl of the electrolytic solution is injected, and the gasket 3 Was sealed with a sealing plate 4.

(3) Battery evaluation About the said battery A and the comparison battery B, after repeating a charging / discharging cycle, the battery was decomposed | disassembled and the deposition condition of the lithium metal on the negative electrode plate or the separator was confirmed.

  As said charging / discharging cycle conditions, charging / discharging was repeated 500 times by 4.2 to 3.0V with the constant current of discharge current 25mA and charge current 10mA in each battery. In all of the batteries A according to the present invention, no lithium metal was deposited on the negative electrode plate or the separator. However, in the comparative battery B, the positive electrode plate located at the lowermost end and the negative electrode plate facing this electrode plate Lithium metal was deposited on the separator sandwiched between the electrodes, and a short circuit occurred between these plates.

  In addition, the present inventors fabricated coin-type batteries using other electrode materials with the same configuration as in this example, and verified the influence of the charge / discharge cycle. As a result, in any coin-type battery using any of the electrode materials, when the same number of electrode plates were used for the positive electrode and the negative electrode, it was confirmed that the active material was deposited on the negative electrode surface, and a micro short circuit occurred. However, in the configuration according to the present invention, no short-circuit and no active material causing the short-circuit occurred, and the effect of the present invention was confirmed.

  As described above, according to the present invention, in a coin-type secondary battery having an electrode group adopting a laminated structure, the deposition of an active material on the negative electrode surface is suppressed, and the occurrence of a micro short circuit due to this deposition is suppressed. Thus, safety, charge / discharge cycle characteristics, charge / discharge characteristics, and reliability can be maintained even during long-term use in which charge / discharge cycles are repeated. For this reason, it can be used as a power source for applications that require high reliability such as memory backup applications in addition to applications that require miniaturization, thinning, and weight reduction of portable devices. It ’s great.

The schematic diagram which shows the cross-sectional structure of the coin-type battery of this invention Schematic diagram showing the internal plan configuration of the battery (A) Schematic diagram showing the configuration of the positive electrode plate of the battery (b) Schematic diagram showing the configuration of the negative electrode plate of the battery Schematic diagram showing the configuration of the electrode group of the battery

Explanation of symbols

1 Electrode Group 2 Battery Can 3 Gasket 4 Sealing Plate 5 Positive Electrode Plate 6 Negative Electrode Plate 7 Separator

Claims (4)

Provided with an electrode group in which a plurality of positive electrode plates and negative electrode plates are alternately stacked via separators, the electrode group together with a non-aqueous electrolyte is insulated by a shallow bottom case that also serves as a positive electrode terminal and a sealing case that also serves as a negative electrode terminal A coin-type secondary battery housed in a battery container that is caulked and sealed through a gasket, wherein the electrode group has a negative electrode plate positioned at the lower end and the upper end of the stack. Type secondary battery. Each of the positive electrode plate and the negative electrode plate includes a positive electrode metal lead and a negative electrode metal lead led out from each end, and the metal leads are drawn out in the same direction by the positive and negative electrodes and connected to each other. The coin-type secondary battery according to claim 1. The negative electrode plate is a double-sided coated electrode plate in which the electrode material is applied to both sides of the metal foil core material and the electrode material is applied to only one surface of the metal foil core material, and the metal foil core material is exposed on the other surface. The single-side coated electrode plate is positioned at the upper end of the electrode group and the lower end of the layer, and the metal foil core material is exposed. The coin-type secondary battery according to claim 1, wherein the coin-type secondary battery is disposed so that the surface faces the sealing case and the bottomed case. The coin-type secondary battery according to claim 1, wherein an insulating sheet is disposed between the electrode group and a bottomed case that also serves as a positive electrode terminal.

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