Electrode package, lamination electrode body, and battery

Abstract

To provide an electrode package capable of achieving increased battery capacity in a lamination type battery.SOLUTION: An electrode package 50 is formed by: a positive electrode 20; and a bag-like separator housing the positive electrode 20. The positive electrode 20 has a shape of which rectangle-shaped four corners are beveled in a circular arc shape in a plan view. That is, the electrode package includes: a circular arc part of the four corners to be beveled in the circular arc shape; and a liner part that is positioned to between the circular arc part of each of the four corners. In addition, a positive electrode lead 20a includes a missing part 20aA. An expansion part 40aB is fixed to the expansion part 40aB via the missing part 20aA in a state where one part on the positive electrode 20 side in the positive electrode lead 20a is housed. Thus, a position deviation of the positive electrode 20 can be suppressed, and an area of the positive electrode 20 in the plan view in a limited internal space of a battery can be increased.SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] The present disclosure relates to an electrode package body accommodated in the internal space of a battery, a laminated electrode body, and a battery accommodating the laminated electrode body, in a laminated battery formed by alternately laminating a plurality of positive electrodes and negative electrodes.

Background Art

[0002] Generally, a flat battery has a structure in which an electrode body having a negative electrode, a positive electrode, and a separator disposed between the positive electrode and the negative electrode, and a non-aqueous electrolyte are accommodated inside a case composed of an outer can and a sealing can. Among such flat batteries, a laminated flat battery in which a plurality of negative electrodes and positive electrodes are alternately laminated is known. Some laminated flat batteries have a positive electrode accommodated in a bag-shaped separator.

[0003] Japanese Patent Application Laid-Open No. 2011-9118 (Patent Document 1) discloses a coin-shaped secondary battery that can reliably discharge the air remaining in a bag-shaped separator and suppress peeling between the upper and lower films forming the separator. The coin-shaped secondary battery includes a positive electrode accommodated in a circular bag-shaped separator. The positive electrode has a substantially circular shape in plan view and is shaped such that the position where the positive electrode lead is connected and the opposing position are linearly cut off. The separator that accommodates the positive electrode is formed in a bag shape by adhering the peripheral edges of two films along the outer periphery of the positive electrode to each other. Further, non-adhesive portions for discharging the air in the internal space of the separator are provided in a dispersed manner at the peripheral edge of the bag-shaped separator.

[0004] International Publication No. 2018 / 124152 (Patent Document 2) discloses a coin-shaped battery in which a positive electrode and a separator are integrated. The coin-shaped battery has a separator disposed on each of the two sides of the positive electrode, and a part of the peripheral edges of both separators is welded by heat pressing to form a joint portion at a part of the peripheral edges of the two separators, thereby integrating the positive electrode and the separator.

[0005] Japanese Patent Application Laid-Open No. 2023-46538 (Patent Document 3) discloses an electrode and a separator that houses the electrode. In plan view, the electrode has a chamfered shape on the arcs at the four corners of a substantially rectangular shape, and has arc portions chamfered in an arc shape and straight portions located between each of the arc portions at the four corners. The bag-shaped separator includes a fixing portion that is fixed outside the radial direction of the straight portion of the electrode in a state where the electrode is housed. Thereby, the area of the electrode is increased, and the electrode is prevented from protruding from the inside of the bag-shaped separator.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0007] With the improvement in performance of electronic devices and the like that use a flat battery as a power source, there is a demand to increase the battery capacity of the flat battery. However, there is still room to further increase the battery capacity in the coin-shaped secondary battery of Patent Document 1 and the coin-shaped battery of Patent Document 2.

[0008] In addition, as shown in FIG. 7, for the electrode and the bag-shaped separator of Patent Document 3, when a relatively strong impact is received, for example, during the assembly of the flat battery or during the transportation of the flat battery, in a state where the electrode 200 and a part of the electrode lead 200a extending from the straight portion of the electrode 200 are accommodated in the bag-shaped separator 400, although the separator 400 is fixed at the fixing portion 410, it is conceivable that the electrode 200 may protrude from the non-fixing portion 420. Therefore, in order to further prevent the electrode 200 from protruding from the non-fixing portion 420, reduce the clearance between the edge of the bag-shaped separator 400 and the edge of the electrode 200, and increase the area of the electrode 200 in plan view to further increase the battery capacity, there is room for further consideration.

[0009] Therefore, an object of the present disclosure is to provide an electrode package body including an electrode and a bag-shaped separator that houses the electrode and can further increase the battery capacity.

Means for Solving the Problems

[0010] In order to solve the above problems, the present disclosure is configured as follows. That is, the electrode package according to the present disclosure is an electrode package housed in the internal space of a battery, and includes an electrode composed of either a positive electrode or a negative electrode, an electrode lead extending outward from the peripheral edge of the electrode, and a bag-shaped separator that houses a part of the electrode side of the electrode and the electrode lead. The electrode has a shape in which the four corners of a substantially rectangular shape are chamfered in an arc shape in a plan view, and has arc portions at the four corners chamfered in an arc shape and straight portions located between each of the arc portions at the four corners. The electrode lead extends outward from the straight portion. The bag-shaped separator has a first film having a first main body portion disposed on one main surface of the electrode and a first overhanging portion extending from the first main body portion and disposed on one main surface of the electrode lead, and a second film having a second main body portion disposed on the other main surface of the electrode and a second overhanging portion extending from the second main body portion and disposed on the other main surface of the electrode lead. The peripheral edge of the first main body portion is fixed to the peripheral edge of the second main body portion radially outside the straight portion of the electrode in a state where the electrode is housed in the bag-shaped separator. The electrode lead has a missing portion that penetrates so that the first overhanging portion and the second overhanging portion face each other. The first overhanging portion is fixed to the second overhanging portion via the missing portion in a state where a part of the electrode side of the electrode lead is housed.

Effects of the Invention

[0011] According to the electrode package, the laminated electrode body, and the battery according to the present disclosure, the battery capacity of the battery can be further increased.

Brief Description of the Drawings

[0012]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Embodiments for Carrying Out the Invention

[0013] (Configuration 1) The electrode package according to an embodiment of the present disclosure is an electrode package housed in the internal space of a battery, and includes an electrode composed of either a positive electrode or a negative electrode, an electrode lead extending outward from the peripheral edge of the electrode, and a bag-shaped separator that houses a part of the electrode side of the electrode and the electrode lead. The electrode has a shape in which the four corners of a substantially rectangular shape are chamfered in an arc shape in a plan view, and has arc portions at the four corners chamfered in an arc shape and straight portions located between each of the arc portions at the four corners. The electrode lead extends outward from the straight portion. The bag-shaped separator has a first film having a first main body portion disposed on one main surface of the electrode and a first overhanging portion extending from the first main body portion and disposed on one main surface of the electrode lead, and a second film having a second main body portion disposed on the other main surface of the electrode and a second overhanging portion extending from the second main body portion and disposed on the other main surface of the electrode lead. The peripheral edge of the first main body portion is fixed to the peripheral edge of the second main body portion outside the radial direction of the straight portion of the electrode in a state where the electrode is housed in the bag-shaped separator. The electrode lead has a missing portion that penetrates so that the first overhanging portion and the second overhanging portion face each other. The first overhanging portion is fixed to the second overhanging portion via the missing portion in a state where a part of the electrode side of the electrode lead is housed.

[0014] By fixing the first overhanging portion to the second overhanging portion via the missing portion in this way, displacement of the electrode can be suppressed, and further prevention of the electrode from protruding from the inside of the bag-shaped separator can be achieved. Therefore, the area of the electrode in a plan view can be increased, and further increase in the capacity of the battery can be achieved.

[0015] (Configuration 2) In the electrode package of Configuration 1, the missing portion may be a notch provided at the side end of the electrode lead. As a result, similar to the electrode package of Configuration 1, displacement of the electrode can be suppressed, and further prevention of the electrode from protruding from inside the bag-shaped separator can be achieved. Therefore, the area of the electrode in plan view can be increased, and further enhancement of the high capacity of the battery can be achieved.

[0016] (Configuration 3) In the electrode package of Configuration 1, the missing portion may be a through hole provided in the electrode lead. As a result, similar to the electrode package of Configuration 1 or 2, displacement of the electrode can be suppressed, and further prevention of the electrode from protruding from inside the bag-shaped separator can be achieved. Therefore, the area of the electrode in plan view can be increased, and further enhancement of the high capacity of the battery can be achieved.

[0017] (Configuration 4) In any one of the electrode packages of Configurations 1 to 3, the first protruding portion may be fixed to the second protruding portion by welding via the missing portion. Thereby, displacement of the electrode accommodated in the bag-shaped separator can be suppressed, and the cycle characteristics of the battery can be improved.

[0018] (Configuration 5) The laminated electrode body according to the embodiment of the present disclosure is formed by alternately laminating any one of the electrode packages of Configurations 1 to 4 and either the positive electrode or the other negative electrode. Thereby, further enhancement of the high capacity of the battery can be achieved.

[0019] (Configuration 5) The battery according to the embodiment of the present disclosure is formed by accommodating the laminated electrode body of Configuration 5 in the internal space of the case. Thereby, further enhancement of the high capacity of the battery can be achieved.

[0020] Hereinafter, the battery 1 and the laminated electrode body 10 according to the present disclosure will be specifically described with reference to FIGS. 1 to 6. First, as shown in FIG. 1, the battery 1 includes an outer can 2, a sealing can 3, a gasket 4, and a laminated electrode body 10. The outer can 2, the sealing can 3, and the gasket 4 are the case of the battery 1. The laminated electrode body 10 is accommodated in the case.

[0021] The outer can 2 includes a bottom portion 2a having a circular shape in plan view and a cylindrical peripheral wall portion 2b formed continuously from the outer periphery of the bottom portion 2a. The peripheral wall portion 2b is provided so as to extend substantially perpendicular to the bottom portion 2a in a longitudinal sectional view. The outer can 2 is formed of a metal material such as stainless steel, nickel, or iron.

[0022] The sealed can 3 includes a circular planar portion 3a and a cylindrical peripheral wall portion 3b formed continuously from the outer periphery of the planar portion 3a. The opening of the sealed can 3 faces the opening of the outer can 2. The sealed can 3 is formed of a metal material such as stainless steel.

[0023] The gasket 4 is formed of a moisture-low-permeability resin such as polypropylene resin, polyphenylene sulfide resin, or tetrafluoroethylene-perfluoroalkoxyethylene copolymer resin. The gasket 4 is formed in a cylindrical shape along the inner peripheral surface of the peripheral wall portion 2b of the outer can 2 and is disposed between the peripheral wall portion 2b of the outer can 2 and the peripheral wall portion 3b of the sealed can 3. The gasket 4 is not particularly limited as long as it can insulate the outer can 2 and the sealed can 3. For example, in addition to polyolefin resins such as polypropylene (PP), it can be composed of resins such as polyphenylene ether (PPE), polysulfone (PSF), polyarylate (PAR), polyethersulfone (PES), polyphenylene sulfide (PPS), polyetheretherketone (PEEK), or fluororesins such as tetrafluoroethylene-perfluoroalkoxyethylene copolymer (PFA). In particular, in addition to PP, PPS resin or fluororesins such as PFA resin are preferably used from the viewpoints of moisture permeability and heat resistance.

[0024] After the exterior can 2 and the sealing can 3 accommodate the laminated electrode body 10 and a non-aqueous electrolyte (not shown), they are caulked via a gasket 4 between the peripheral wall portion 2b of the exterior can 2 and the peripheral wall portion 3b of the sealing can 3. That is, the exterior can 2 and the sealing can 3 are caulked via a gasket 4 after opposing the openings of the exterior can 2 and the sealing can 3 to each other and inserting the peripheral wall portion 3b of the sealing can 3 inside the peripheral wall portion 2b of the exterior can 2. In this way, an internal space of the battery 1 for accommodating the laminated electrode body 10 is formed.

[0025] The laminated electrode body 10 is an electrode body in which a plurality of positive electrodes (electrodes) 20 and negative electrodes 30 are alternately laminated. The positive electrode 20 is accommodated in a bag-shaped separator 40 to form an electrode package 50. That is, the electrode package 50 is composed of the positive electrode 20, a positive electrode lead 20a described later, and a bag-shaped separator 40 that accommodates a part of the positive electrode 20 side of the positive electrode 20 and the positive electrode lead 20a. The number of laminations of the electrode package 50 and the negative electrode 30 is determined by the desired battery capacity. Therefore, the number of these laminations is not limited to the illustrated one. Among the plurality of negative electrodes 30, the negative electrode 30 closest to the inner surface of the bottom portion 2a of the exterior can 2 and the negative electrode 30 closest to the inner surface of the flat portion 3a of the sealing can 3 each have a negative electrode active material layer 32 provided only on one surface of the negative electrode current collector 31, and the negative electrode 30 closest to the inner surface of the flat portion 3a of the sealing can 3 has its negative electrode current collector 31 in contact with the flat portion 3a. Also, an insulating sheet 60 is provided between the negative electrode 30 closest to the inner surface of the bottom portion 2a of the exterior can 2 and the bottom portion 2a of the exterior can 2. The insulating sheet 60 insulates the negative electrode 30 closest to the inner surface of the bottom portion 2a of the exterior can 2 and the bottom portion 2a of the exterior can 2.

[0026] In the internal space of the battery 1, a positive electrode lead 20a and a negative electrode lead 30a are further accommodated. The positive electrode lead 20a continuously extends from the peripheral end portion of each positive electrode current collector 21 of the positive electrode 20 shown in FIG. 2 described later. Each positive electrode lead 20a electrically connects the corresponding positive electrode 20 and the bottom portion 2a of the exterior can 2. The negative electrode lead 30a continuously extends from the peripheral end portion of each negative electrode current collector 31 of the negative electrode 30 shown in FIG. 2 described later. Each negative electrode lead 30a connects the corresponding negative electrode 30 and the flat portion 3a of the sealing can 3. Therefore, the exterior can 2 functions as a positive electrode can, and the sealing can 3 functions as a negative electrode can. As will be described later, a part of the positive electrode 20 side of the positive electrode lead 20a is accommodated between the protruding portions 40aB and 40bB of the bag-shaped separator 40.

[0027] As shown in FIG. 2, each positive electrode 20 has a positive electrode current collector 21 and a positive electrode active material layer 22 disposed on both surfaces of the positive electrode current collector 21. The positive electrode current collector 21 is, for example, a metal foil such as aluminum foil. The positive electrode active material layer 22 is, for example, a layer formed by compression molding a positive electrode active material such as lithium cobaltate, a binder, a conductive assistant, and the like.

[0028] Each negative electrode 30 has a negative electrode current collector 31 and a negative electrode active material layer 32 disposed on both surfaces or one surface of the negative electrode current collector 31. The negative electrode current collector 31 is, for example, a metal foil such as copper foil. The negative electrode active material layer 32 is, for example, a layer formed by compression molding a negative electrode active material such as graphite, a binder, a conductive assistant, and the like.

[0029] The positive electrode current collector 21 is electrically connected to the exterior can 2 via the positive electrode lead 20a. An end portion of the positive electrode lead 20a close to the positive electrode current collector 21, that is, a part of the positive electrode 20 side, is covered between the protruding portions 40aB and 40bB of the bag-shaped separator 40. The positive electrode lead 20a is bent toward the bottom portion 2a of the exterior can 2 at a location covered between the protruding portions 40aB and 40bB of the separator 40. Each end portion of the plurality of positive electrode leads 20a close to the exterior can 2 is bundled together and connected to the exterior can 2.

[0030] Each of the bag-shaped separators 40 is, for example, a microporous film made of polyethylene with excellent insulating properties. Thus, the separator 40 can allow lithium ions to permeate. Details of the separator 40 (film 40a and film 40b) will be described later.

[0031] As shown in FIG. 3, in plan view, the positive electrode 20 has a shape in which the four corners of a substantially rectangular shape indicated by a one-dot chain line in the figure are chamfered in an arc shape, and has arc portions 23a, 23b, 23c, and 23d, and straight portions 24a, 24b, 24c, and 24d. The arc portions 23a, 23b, 23c, and 23d are formed along the circumference of a circle having a center C, that is, along the circumference of the same circle. The straight portion 24a is formed between the arc portions 23a and 23b. The straight portion 24b is formed between the arc portion 23b and the arc portion 23c. The straight portion 24c is formed between the arc portion 23c and the arc portion 23d. The straight portion 24d is formed between the arc portion 23a and the arc portion 23d. That is, each of the straight portions is formed between adjacent arc portions. The circle having the center C is a concentric circle having a smaller diameter than the circle drawn by the outer peripheral end of the flat portion 3a of the circular sealed can 3 described above. That is, the center C is positioned on the cylinder axis of the cylindrical battery 1. Thereby, the positive electrode 20 is appropriately accommodated in the internal space of the battery 1. Further, the center C is positioned closer to the straight portion 24d side (the left side in the figure) where the positive electrode lead 20a is arranged than the intersection point of the diagonal lines of the substantially rectangular shape (not shown). That is, the straight portion 24d where the positive electrode lead 20a is arranged is longer than the opposing straight portion 24b. Thereby, as shown in FIG. 1 or 2, when the positive electrode 20 accommodated in the separator 40 is accommodated in the internal space of the battery 1, a space for accommodating the positive electrode lead 20a can be secured.

[0032] The approximate rectangle in the figure has a short side α and a long side β. The positive electrode lead 20a is connected to the positive electrode current collector 21 of the straight portion 24d formed on the long side β. The short side α has a length L1. The long side β has a length L2. When the ratio of the length L1 to the length L2 is set with L1 being 1, it is preferable that L2 be 1.05 to 1.25. More preferably, when L1 is 1, L2 is preferably 1.08 to 1.21. Thereby, in the limited internal space of the battery 1, while securing a space for accommodating the positive electrode lead 20a and the negative electrode lead 30a and a space for providing the fixing portion 41 of the separator 40 described later, the area of the positive electrode 20 in plan view, which has a shape with the four corners of the approximate rectangle chamfered in an arc shape, can be maximized. As a result, the battery 1 can be made to have a higher capacity.

[0033] As shown in FIG. 4, the positive electrode 20 is housed in a bag-shaped separator 40. As shown in FIG. 2, the separator 40 has a film 40a and a film 40b. The film 40a has a main body portion 40aA disposed on one main surface (the upper side in the drawing) of the positive electrode 20 and an overhanging portion 40aB extending from the main body portion 40aA and disposed on one main surface of the positive electrode lead 20a. The film 40b has a main body portion 40bA disposed on the other main surface (the lower side in the drawing) of the positive electrode 20 and an overhanging portion 40bB extending from the main body portion 40bA and disposed on the other main surface of the positive electrode lead 20a. The size of each of the film 40a and the film 40b in plan view is slightly larger than the side end portion on the positive electrode 20 side of the positive electrode 20 and the positive electrode lead 20a connected to the positive electrode 20. The film 40a and the film 40b are, for example, a polyethylene microporous film or the like. The method of housing the positive electrode 20 in the separator 40 is as follows. First, the film 40a and the film 40b are prepared. A part of the positive electrode 20 and the positive electrode 20 side of the positive electrode lead 20a are disposed between the film 40a and the film 40b. Finally, a part of the peripheral edge of the film 40a and the peripheral edge of the film 40b facing the part of the peripheral edge of the film 40a are fixed by heat pressing. In this way, the separator 40 is formed in a bag shape and houses a part of the positive electrode 20 and the positive electrode 20 side of the positive electrode lead 20a.

[0034] As shown in FIG. 4, the peripheral portion of the film 40a includes a fixed portion 41 fixed to a part of the peripheral portion of the opposing film 40b and an unfixed portion 42 that is not fixed. In other words, the separator 40 has a fixed portion 41 and an unfixed portion 42 at its peripheral portion. More specifically, the fixed portion 41 is formed to be positioned radially outward of the straight portions 24a, 24b, 24c, and 24d shown in FIG. 3, and the unfixed portion 42 is formed to be positioned radially outward of the arc portions 23a, 23b, 23c, and 23d. Further, the fixed portion 41 positioned radially outward of the straight portion 24d is formed to also extend along both side portions of the positive electrode lead 20a. The outer peripheral ends of the fixed portion 41 positioned radially outward of the straight portions 24a and 24c are formed by an arc along the periphery of the flat portion 3a of the sealed can 3 and a straight line along the straight portions 24a and 24c. Therefore, the planar shape of the fixed portion 41 positioned radially outward of the straight portions 24a and 24c is a sector. In this way, the fixed portion 41 suppresses the positive electrode 20 from being displaced and exposed from the unfixed portion 42 to cause a short circuit. Further, the unfixed portion 42 enables the discharge of air or the like remaining inside the bag-shaped separator 40. Note that the method of fixing the peripheral portion of the separator 40 is not limited to welding by heat pressing, and it may be adhered with an adhesive or the like, and is not particularly limited.

[0035] Also, as shown in FIG. 4, missing portions 20aA are provided at both side ends of the positive electrode lead 20a so that the overhanging portion 40aB of the film 40a and the overhanging portion 40bB of the film 40b face each other. That is, the overhanging portion 40aB and the overhanging portion 40bB can contact each other through the missing portion 20aA.

[0036] Here, in the present embodiment, the fixing portion 41 formed along both side portions of the positive electrode lead 20a is formed to protrude toward the positive electrode lead 20a at a location corresponding to the missing portion 20aA in a state where a part of the positive electrode 20 side in the positive electrode lead 20a is accommodated. That is, the protruding portion 40aB of the film 40a is also fixed to the protruding portion 40bB even at a portion passing through the missing portion 20aA of the positive electrode lead 20a. Further, as shown in FIG. 4, a part of the fixing portion 41 formed to protrude is formed in a shape that fits into the missing portion 20aA. Therefore, a part of the fixing portion 41 formed to protrude, that is, a portion fixed via the missing portion 20aA in the fixing portion 41 may hereinafter be referred to as the fitting and fixing portion 41a. In this way, since a part of the fixing portion 41 is formed so as to fit into the missing portion 20aA, the movement of the positive electrode lead 20a and the positive electrode 20 with respect to the bag-shaped separator 40 is restricted, and it is possible to further suppress the positive electrode 20 from being exposed from the non-fixing portion 42 and short-circuited due to the positional deviation of the positive electrode 20. As a result, to the extent that the positional deviation of the positive electrode 20 can be suppressed, the area of the positive electrode 20 in plan view can be increased to increase the capacity of the battery 1. The fitting and fixing portion 41a may extend from the fixing portion 41 or may be spaced apart from the fixing portion 41.

[0037] From the viewpoint of effectively suppressing the positional deviation of the positive electrode 20, the shape of the fitting and fixing portion 41a in plan view is preferably a shape along the shape of the missing portion 20aA in plan view. In the present embodiment, as shown in FIG. 4, the shape of the fitting and fixing portion 41a in plan view is a trapezoidal shape, and the shape of the missing portion 20aA in plan view is a trapezoidal shape slightly smaller than the fitting and fixing portion 41a. The shape of each of the fitting and fixing portion 41a and the missing portion 20aA in plan view is not limited to a trapezoidal shape, and may be a semi-circular shape, a semi-elliptical shape, or a polygonal shape, as long as the outer edge shape of the fitting and fixing portion 41a in plan view and the inner edge shape of the missing portion 20aA in plan view are similar.

[0038] The two-dot chain line in Fig. 4 indicates the outer peripheral end portion on the inner surface of the flat portion 3a of the sealed can 3. In plan view, the radius of the arc portion of the peripheral edge of the separator 40 is smaller than or equal to the radius of the circle drawn by the outer peripheral end portion on the inner surface of the flat portion 3a of the sealed can 3. Thereby, the positive electrode 20 accommodated in the separator 40 can be appropriately accommodated in the internal space of the battery 1. Further, by providing the straight portions 24b and 24d, predetermined spaces are formed between the laminated electrode body 10 shown in Fig. 1 and the peripheral wall portion 3b of the sealed can 3, respectively. The negative electrode lead 30a is accommodated in the space facing the straight portion 24b. The positive electrode lead 20a bent toward the bottom portion 2a of the exterior can 2 is accommodated in the space facing the straight portion 24d.

[0039] The relationship between the ratio of the lengths L1 and L2 described above can also be explained from the following perspective. With reference to FIGS. 3 and 4, when the length L3 of the straight portions 24a or 24c formed on the short side α is shortened, that is, when the length L2 of the long side β becomes longer with respect to the length L1 of the short side α while keeping the radius of the circle including the arc portions 23a, 23b, 23c, and 23d constant, the area of the positive electrode 20 in plan view increases. However, the radial width (the vertical width shown in FIG. 4) of the fixing portions 41, 41 located radially outward of the straight portions 24a and 24c becomes smaller, and the fixing of the peripheral portion of the separator 40 may become insufficient. As a result, due to poor fixing, the positive electrode 20 may be exposed outward from the separator 40 and cause a short circuit. On the other hand, when the length L3 of the straight portions 24a or 24c formed on the short side α becomes longer, that is, as the ratio of the length L1 of the short side α to the length L2 of the long side β approaches 1:1 while keeping the radius of the circle including the arc portions 23a, 23b, 23c, and 23d constant, the area of the positive electrode 20 in plan view becomes smaller. However, the radial width of the fixing portions 41, 41 located radially outward of the straight portions 24a and 24c becomes larger, and the peripheral portion of the separator 40 can be sufficiently fixed. From such a perspective, the length L3 of the straight portions 24a or 24c formed on the short side α is preferably 15% or more, more preferably 20% or more, and still more preferably 25% or more of the length L1 of the short side α. Also, the length L3 of the straight portions 24a or 24c formed on the short side α is preferably 50% or less, more preferably 45% or less, and still more preferably 40% or less of the length L1 of the short side α. Alternatively, when the length L1 is set to 1, the ratio of the length L1 to the length L2 is preferably 1.05 to 1.25. More preferably, when the length L1 is set to 1, the length L2 is preferably 1.08 to 1.21.

[0040] Also, from the perspective of accommodating the positive electrode lead 20a and the negative electrode lead 30a in the internal space of the battery 1, the lengths of the straight portions 24b and 24d formed on the long side β may be made longer than the widths of the negative electrode lead 30a and the positive electrode lead 20a, respectively. However, as long as the positive electrode lead 20a and the negative electrode lead 30a can be accommodated in the internal space of the battery 1, it is desirable that the space in which the negative electrode lead 30a and the positive electrode lead 20a are accommodated be as small as possible. Therefore, the lengths of the straight portions 24b and 24d formed on the long side β are preferably made as short as possible with respect to the length L2 of the long side β.

[0041] Thus, according to the electrode package 50 according to the present disclosure, by making the planar shape of the substantially rectangular four corners chamfered in an arc shape, not only can the area of the positive electrode 20 in plan view be maximized and the battery capacity of the battery 1 be increased as much as possible, but also by fixing the overhanging portions 40aB and 40bB of the film 40a via the missing portion 20aA of the positive electrode lead 20a, the positional deviation of the positive electrode 20 can be suppressed and the battery capacity of the battery 1 can be further increased. Furthermore, by accommodating the laminated electrode body 10 including this electrode package 50 in the battery 1, the battery capacity of the battery 1 can be further increased.

[0042] In the above-described embodiment, the positive electrode 20 is accommodated in the separator 40, but the negative electrode (electrode) 30 may be accommodated in the separator 40 to form the electrode package 50. At this time, the separator 40 accommodates a part of the negative electrode 30 side of the negative electrode lead 30a.

[0043] Also, in the bag-shaped separator 40 shown in FIG. 4, fitting and fixing portions 41a are formed on the fixing portions 41 formed along both side portions of the positive electrode lead 20a, and missing portions 20aA are formed on both side portions of the positive electrode lead 20a, respectively. However, as shown in FIG. 5, a missing portion 20aA may be provided on one of the two side portions of the positive electrode lead 20a, and the overhanging portion 40aB and the overhanging portion 40bB may be fixed via the missing portion 20aA.

[0044] (Modification 2) Further, as shown in FIG. 6, the protruding portion 40aB and the protruding portion 40bB may be fixed via a missing portion 20aA which is a through hole provided in the positive electrode lead 20a. In the second modification, the planar shape of the fitting and fixing portion 41a is circular, and the planar shape of the missing portion 20aA is a circular shape slightly larger than that of the fitting and fixing portion 41a. The planar shapes of the fitting and fixing portion 41a and the missing portion 20aA are not limited to circular shapes, and may be elliptical or polygonal shapes, as long as the outer edge shape of the fitting and fixing portion 41a in plan view and the inner edge shape of the missing portion 20aA in plan view are similar.

[0045] As described above, the embodiments have been described. However, the present disclosure is not limited to the above embodiments, and various modifications are possible without departing from the spirit thereof.

Explanation of Reference Numerals

[0046] 1 Battery, 2 Outer can, 3 Sealed can, 4 Gasket, 10 Stacked electrode body, 20 Positive electrode, 21 Positive electrode current collector, 22 Positive electrode active material layer, 23a to 23d Arc portions, 24a to 24d Straight portions, 20a Positive electrode lead, 20aA Missing portion, 30 Negative electrode, 31 Negative electrode current collector, 32 Negative electrode active material layer, 40 Separator, 40a Film, 40aA Main body portion, 40aB Protruding portion, 40b Film, 40bA Main body portion, 40bB Protruding portion, 41 Fixing portion, 41a Fitting and fixing portion, 42 Non-fixing portion, 50 Electrode package, 60 Insulating sheet, α Short side, β Long side

Claims

1. An electrode package accommodated in the internal space of a battery, comprising: an electrode composed of either a positive electrode or a negative electrode; an electrode lead extending outward from the peripheral edge of the electrode; a bag-shaped separator that houses the electrode and a part of the electrode side of the electrode lead, wherein the electrode has a shape in which the four corners of a substantially rectangular shape are chamfered in an arc shape in a plan view, and has arc portions at the four corners chamfered in an arc shape and straight portions located between each of the arc portions at the four corners; the electrode lead extends outward from the straight portion; the bag-shaped separator includes a first film having a first main body portion disposed on one main surface of the electrode and a first overhanging portion extending from the first main body portion and disposed on one main surface of the electrode lead, and a second film having a second main body portion disposed on the other main surface of the electrode and a second overhanging portion extending from the second main body portion and disposed on the other main surface of the electrode lead; the peripheral edge of the first main body portion is fixed to the peripheral edge of the second main body portion radially outward of the straight portion of the electrode in a state where the electrode is housed in the bag-shaped separator; the electrode lead has a missing portion that penetrates so that the first overhanging portion and the second overhanging portion face each other; the first overhanging portion is fixed to the second overhanging portion through the missing portion in a state where a part of the electrode side of the electrode lead is housed, the electrode package.

2. The electrode package according to claim 1, wherein the missing portion is a notch provided at the side end of the electrode lead, the electrode package.

3. The electrode package according to claim 1, wherein the missing portion is a through hole provided in the electrode lead, the electrode package.

4. The electrode package according to claim 1, wherein the first overhanging portion is fixed to the second overhanging portion by welding through the missing portion, the electrode package.

5. A laminated electrode body formed by alternately laminating the electrode package according to any one of claims 1 to 4 and either the positive electrode or the negative electrode of the other electrode.

6. A battery formed by housing the laminated electrode body according to claim 5 in the internal space of a case.

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