Electrode package, lamination electrode body, and battery

Abstract

To provide an electrode package in a lamination type battery, capable of increasing a battery capacity in a laminate type battery.SOLUTION: An electrode package 50 is formed by: a positive electrode 20; and a bag-like separator 40 that houses the positive electrode 20. The positive electrode 20 is a shape in which four corners of a substantially rectangular shape are chamfered in a circular arc in a plan view. That is, it includes: circular arc parts of the four corners chamfered in a circular arc; and a straight line part positioned between the circular arc parts of the four corners. In addition, a side end of an expansion part 40aB is fixed with a side end of an expansion part 40bB with a side end of an electrode lead 20a in a state where a part of the positive electrode 20 side in the 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 2

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 Unexamined Patent Application Publication 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 accommodating 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. Further, non-adhesive portions for discharging the air in the internal space of the separator are dispersedly provided 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 both surfaces of the positive electrode, and a part of the peripheral edge of both separators is welded by heat pressing to form a joint portion at a part of the peripheral edge of the two separators, thereby integrating the positive electrode and the separator.

[0005] JP-A-2023-46538 (Patent Document 3) discloses an electrode and a separator that houses the electrode. In plan view, the electrode has a shape chamfered on the arcs at the four corners of a substantially rectangular shape, and has arc-shaped chamfered portions at the four corners and straight portions located between each of the arc-shaped chamfered portions at the four corners. The bag-shaped separator includes a fixing portion that is fixed radially outward 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] Further, as shown in FIG. 6, in the electrode and the bag-shaped separator of Patent Document 3, 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, for example, when a relatively strong impact is received during the assembly of the flat battery or during the transportation of the flat battery, although the separator 400 is fixed at the fixing portion 410, it can be assumed 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 side end of the first overhanging portion is fixed to the side end of the second overhanging portion together with the side end of the electrode lead in a state where a part of the electrode side of the electrode lead is housed.

Effect 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

Embodiments for Carrying Out the Invention

[0013] (Configuration 1) An electrode package according to an embodiment of the present disclosure is an electrode package housed in an 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 a 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 side end of the first overhanging portion is fixed to the side end of the second overhanging portion together with the side end of the electrode lead in a state where a part of the electrode side of the electrode lead is housed.

[0014] By fixing the electrode lead together with the first overhanging portion and the second overhanging 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 improvement in the high capacity of the battery can be achieved.

[0015] (Configuration 2) In the electrode package of Configuration 1, the side end of the first overhanging portion may be fixed to the side end of the second overhanging portion together with the side end of the electrode lead by welding. Thereby, displacement of the electrode housed in the bag-shaped separator can be suppressed, and the cycle characteristics of the battery can be improved.

[0016] (Configuration 3) In the electrode package of Configuration 1 or 2, the side edge of the first protruding portion may be fixed to the side edge of the second protruding portion at the tip of the first protruding portion and the second protruding portion together with the side edge of the electrode lead. Thereby, a short circuit that may occur when the electrode lead is bent can be suppressed.

[0017] (Configuration 4) The electrode laminate according to the embodiment of the present disclosure is formed by alternately laminating any one of the electrode packages of Configurations 1 to 3 and the other electrode of the positive electrode and the negative electrode. Thereby, it is possible to further increase the capacity of the battery.

[0018] (Configuration 5) The battery according to the embodiment of the present disclosure is formed by housing the laminated electrode body of Configuration 4 in the internal space of the case. Thereby, it is possible to further increase the capacity of the battery.

[0019] 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 5. 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 housed in the case.

[0020] 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.

[0021] The sealing 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 sealing can 3 faces the opening of the outer can 2. The sealing can 3 is formed of a metal material such as stainless steel.

[0022] The gasket 4 is formed of a moisture-low-permeability resin such as polypropylene resin, polyphenylene sulfide resin, and 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 fluorine resins such as tetrafluoroethylene-perfluoroalkoxyethylene copolymer (PFA). In particular, in addition to PP, from the viewpoints of moisture permeability and heat resistance, fluorine resins such as PPS resin or PFA resin are preferably used.

[0023] After the outer can 2 and the sealed can 3 accommodate the laminated electrode body 10 and a non-aqueous electrolyte (not shown), they are caulked via the gasket 4 between the peripheral wall portion 2b of the outer can 2 and the peripheral wall portion 3b of the sealed can 3. That is, the outer can 2 and the sealed can 3 are caulked via the gasket 4 between the peripheral wall portion 2b and the peripheral wall portion 3b after opposing the openings of the outer can 2 and the sealed can 3 to each other and inserting the peripheral wall portion 3b of the sealed can 3 inside the peripheral wall portion 2b of the outer can 2. In this way, the internal space of the battery 1 for accommodating the laminated electrode body 10 is formed.

[0024] 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 housed 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 houses 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 those shown in the figure. Among the plurality of negative electrodes 30, the negative electrode 30 closest to the inner surface of the bottom 2a of the outer 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. 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 2a of the outer can 2 and the bottom 2a of the outer can 2. The insulating sheet 60 insulates the negative electrode 30 closest to the inner surface of the bottom 2a of the outer can 2 and the bottom 2a of the outer can 2.

[0025] In the internal space of the battery 1, a positive electrode lead 20a and a negative electrode lead 30a are further housed. The positive electrode lead 20a extends continuously from the peripheral end portion of the positive electrode current collector 21 of each positive electrode 20 shown in FIG. 2 described later. Each positive electrode lead 20a electrically connects the corresponding positive electrode 20 and the bottom 2a of the outer can 2. The negative electrode lead 30a extends continuously from the peripheral end portion of the negative electrode current collector 31 of each 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 outer can 2 functions as a positive electrode can, and the sealing can 3 functions as a negative electrode can. Note that, as will be described later, a part of the positive electrode 20 side of the positive electrode lead 20a is housed between the protruding portions 40aB and 40bB of the bag-shaped separator 40.

[0026] 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 sides of the positive electrode current collector 21. The positive electrode current collector 21 is, for example, a metal foil such as an aluminum foil. The positive electrode active material layer 22 is, for example, a layer obtained by compression molding a positive electrode active material such as lithium cobaltate, a binder, a conductive auxiliary agent, and the like.

[0027] Each negative electrode 30 has a negative electrode current collector 31 and a negative electrode active material layer 32 disposed on both sides or one side of the negative electrode current collector 31. The negative electrode current collector 31 is, for example, a metal foil such as a copper foil. The negative electrode active material layer 32 is, for example, a layer obtained by compression molding a negative electrode active material such as graphite, a binder, a conductive auxiliary agent, and the like.

[0028] The positive electrode current collector 21 is electrically connected to the exterior can 2 via a positive electrode lead 20a. The end of the positive electrode lead 20a close to the positive electrode current collector 21, that is, a part on 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 2a of the exterior can 2 at the portion covered between the protruding portions 40aB and 40bB of the separator 40. Each end of the plurality of positive electrode leads 20a close to the exterior can 2 is bundled together and connected to the exterior can 2.

[0029] Each bag-shaped separator 40 is, for example, a microporous film made of polyethylene having excellent insulation properties. Thereby, the separator 40 can transmit lithium ions. Details of the separator 40 (film 40a and film 40b) will be described later.

[0030] As shown in FIG. 3, 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 in a plan view, 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 diameter smaller 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 of the diagonal lines of the above-described 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.

[0031] 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 have a higher capacity.

[0032] 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 sizes of the film 40a and the film 40b in plan view are slightly larger than the side end portions 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.

[0033] 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 a non-fixed portion 42 that is not fixed. In other words, the separator 40 has the fixed portion 41 and the non-fixed 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 non-fixed 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 also formed 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 non-fixed portion 42 to cause a short circuit. Further, the non-fixed 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.

[0034] Here, in the fixed portion 41 formed along both side portions of the positive electrode lead 20a, the side end of the protruding portion 40aB of the film 40a is fixed together with the side end of the positive electrode lead 20a to the side end of the protruding portion 40bB of the film 40b in a state of accommodating a part of the positive electrode 20 side in the positive electrode lead 20a. That is, the fixed portion 41 formed along both side portions of the positive electrode lead 20a is fixed by heat pressing in a state including the side ends of the positive electrode lead 20a together with the protruding portion 40aB and the protruding portion 40bB. Thereby, the movement of the positive electrode lead 20a and the positive electrode 20 with respect to the bag-shaped separator 40 can be stopped, and it is possible to further suppress the positive electrode 20 from being exposed from the non-fixed portion 42 due to the displacement of the position of the positive electrode 20 and causing a short circuit. As a result, to the extent that the displacement of the position 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.

[0035] Also, as shown in FIG. 4, the side end of the protruding portion 40aB is fixed to the side end of the protruding portion 40bB at the tip of the protruding portion 40aB and the protruding portion 40bB together with the side end of the positive electrode lead 20a. That is, the side end of the protruding portion 40aB is fixed to the side end of the protruding portion 40bB without passing through the side end of the positive electrode lead 20a in the vicinity of the boundary with the main body portion 40aA (the location positioned between the tip of the protruding portion 40aB and the main body portion 40aA). In other words, in the vicinity of this boundary with the main body portion 40aA, the side ends of the protruding portion 40aB and the protruding portion 40bB are not fixed to the side end of the positive electrode lead 20a. If the side end of the protruding portion 40aB is fixed to the side end of the protruding portion 40bB together with the positive electrode lead 20a even in the vicinity of this boundary with the main body portion 40aA, as shown in FIG. 1, when trying to bend the positive electrode lead 20a, it is conceivable that the protruding portion 40bB fixed to the positive electrode lead 20a is damaged and the positive electrode lead 20a is exposed. Therefore, if the protruding portion 40aB is fixed to the protruding portion 40bB in the vicinity of the boundary with the main body portion 40aA which is near the negative electrode 30, the exposed positive electrode lead 20a and the negative electrode 30 may come into contact and a short circuit may occur. Therefore, by fixing the positive electrode lead 20a at the tips of the protruding portion 40aB and the protruding portion 40bB, a short circuit that may occur when bending the positive electrode lead 20a can be further suppressed. In particular, when fixing the protruding portion 40aB and the protruding portion 40bB by welding, since damage accumulates in the protruding portion 40bB by thermal pressing, it is preferable to fix them at the tips of the protruding portion 40aB and the protruding portion 40bB.

[0036] 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 described 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 respectively formed between the laminated electrode body 10 shown in Fig. 1 and the peripheral wall portion 3b of the sealed can 3. 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.

[0037] The relationship between the ratio of the above-mentioned lengths L1 and L2 can also be explained from the following viewpoints. 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 becomes larger, but 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, but 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 viewpoint, 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, 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, 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.

[0038] Further, 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.

[0039] As described above, 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, but also by fixing the positive electrode lead 20a together with the overhanging portion 40aB of the film 40a and the overhanging portion 40bB of the film 40b, 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.

[0040] 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.

[0041] Also, in the bag-shaped separator 40 shown in FIG. 4, in the fixing portions 41 formed along both side portions of the positive electrode lead 20a, each fixing portion 41 along both side portions is fixed together with the positive electrode lead 20a. However, as shown in FIG. 5, it may be fixed together with the positive electrode lead 20a only in one fixing portion 41 (the upper fixing portion 41 in the drawing) on one side along both side portions of the positive electrode lead 20a.

[0042] Although the embodiments have been described above, the present disclosure is not limited to the above embodiments, and various modifications can be made without departing from the spirit thereof.

Description of Reference Numerals

[0043] 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, 30 Negative electrode, 31 Negative electrode current collector, 32 Negative electrode active material layer, 40 Separator, 40a Film, 40aA Main body portion, 40aB Overhanging portion, 40b Film, 40bA Main body portion, 40bB Overhanging portion, 41 Fixing portion, 42 Non-fixing portion, 50 Electrode package, 60 Insulating sheet, α Short side, β Long side

Claims

1. An electrode package housed in the internal space of a battery, comprising: an electrode consisting of either the positive electrode or the negative electrode; an electrode lead extending outward from the peripheral edge of the electrode; a bag-shaped separator that houses a part of the electrode side of the electrode and the electrode lead; and the electrode has a shape in which the four corners of a substantially rectangular shape are chamfered into an arc shape in a plan view, and has arc portions at the four corners chamfered into 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 outside the radial direction of the straight portion of the electrode in a state where the electrode is housed in the bag-shaped separator; an electrode package, wherein a side end of the first overhanging portion is fixed to a side end of the second overhanging portion together with a side end of the electrode lead in a state where a part of the electrode side of the electrode lead is housed.

2. The electrode package according to claim 1, wherein a side end of the first overhanging portion is fixed to a side end of the second overhanging portion together with a side end of the electrode lead by welding.

3. The electrode package according to claim 1, wherein a side end of the first overhanging portion is fixed to a side end of the second overhanging portion at the tip of the first overhanging portion and the second overhanging portion together with a side end of the electrode lead.

4. A laminated electrode body formed by alternately laminating the electrode package according to any one of claims 1 to 3 and the other electrode of the positive electrode and the negative electrode.

5. A battery formed by housing the laminated electrode body according to claim 4 in the internal space of a case.

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