JP2024131678A - Secondary battery - Google Patents

Abstract

To provide a secondary battery having high capacity despite a compact structure.SOLUTION: A secondary battery in one embodiment of the present disclosure includes a battery element that has a first electrode and a second electrode, and an exterior member that accommodates the battery element. The exterior member includes a tubular wall part including a first open end and a second open end that face each other in a first direction, and having a multilayer structure of a metal foil and a resin film, a first electrode terminal plate bonded to the first open end of the tubular wall part and a second electrode terminal plate bonded to the second open end of the tubular wall part.SELECTED DRAWING: Figure 1B

Description

This disclosure relates to secondary batteries.

As various electronic devices such as mobile phones become widespread, secondary batteries are being developed as power sources that are small and lightweight and can provide high energy density. These secondary batteries have a positive electrode, a negative electrode, and an electrolyte housed inside an exterior member, and various studies have been conducted on the configuration of these secondary batteries (see, for example, Patent Document 1).

For example, Patent Document 1 describes a sealed electricity storage device that includes an electrode body in which a positive electrode body and a negative electrode body are stacked or wound with a separator interposed therebetween, and an exterior case that houses the electrode body.

JP 2019-46639 A

Various studies have been conducted to improve the performance of secondary batteries. However, there is still room for improvement in the performance of secondary batteries.

Therefore, it is desirable to provide a secondary battery that has a compact configuration yet a high capacity.

A secondary battery according to an embodiment of the present disclosure includes a battery element having a first electrode and a second electrode, and an exterior member that houses the battery element. The exterior member includes a first open end and a second open end that face each other in a first direction, and has a cylindrical wall portion having a laminated structure of a metal foil and a resin film, a first electrode terminal plate joined to the first open end of the cylindrical wall portion, and a second electrode terminal plate joined to the second open end of the cylindrical wall portion.

In the secondary battery of one embodiment of the present disclosure, the exterior member includes a cylindrical wall portion having a laminated structure of metal foil and resin film, so that the battery element has a configuration suitable for miniaturization and weight reduction while maintaining its size. Thus, the secondary battery of one embodiment of the present disclosure has a high capacity despite its compact configuration.

Note that the effects of the present disclosure are not necessarily limited to the effects described herein, but may be any of a series of effects related to the present technology described below.

FIG. 1A is a perspective view illustrating a configuration of a secondary battery according to an embodiment of the present disclosure. FIG. 1B is an exploded perspective view of the secondary battery shown in FIG. 1A. FIG. 2 is a vertical sectional view showing a sectional configuration of the secondary battery shown in FIG. 1A. FIG. 3 is an enlarged cross-sectional view showing a cross-sectional configuration of a portion of the secondary battery shown in FIG. FIG. 4 is a partial cross-sectional view showing the configuration of the battery element shown in FIG. FIG. 5 is an enlarged cross-sectional view showing a cross-sectional configuration of a portion of the secondary battery of the first modified example. FIG. 6 is an enlarged cross-sectional view showing a cross-sectional configuration of a portion of a secondary battery according to a second modified example. FIG. 7 is an enlarged cross-sectional view showing a cross-sectional configuration of a portion of a secondary battery according to a third modified example. FIG. 8 is an enlarged cross-sectional view showing a cross-sectional configuration of a portion of a secondary battery according to a fourth modified example.

Hereinafter, an embodiment of the present disclosure will be described in detail with reference to the drawings. The description will be given in the following order.

1. One embodiment 1-1. Configuration 1-2. Operation 1-3. Manufacturing method 1-4. Actions and effects 2. Modifications of one embodiment 2-1. First modification 2-2. Second modification 2-3. Third modification 2-4. Fourth modification

1. One embodiment
First, a secondary battery according to an embodiment of the present disclosure will be described.

The secondary battery described here has a flat, columnar, three-dimensional appearance, and is referred to as a coin type or button type. As described below, this secondary battery has a pair of bottoms facing each other, and a side wall portion located between the pair of bottoms. In this secondary battery, the height is smaller than the outer diameter. The "outer diameter" here refers to the maximum diameter (maximum outer diameter) of the bottoms. In this secondary battery, the maximum diameters of the pair of opposing bottoms are substantially equal to each other. Also, the "height" here refers to the maximum distance from the upper surface of one bottom to the lower surface of the other bottom. In this embodiment, the direction in which the pair of bottoms face each other is defined as the height direction Z.

The charge and discharge principle of the secondary battery is not particularly limited, but the following describes a case where battery capacity is obtained by utilizing the absorption and release of electrode reactants. This secondary battery has a positive electrode, a negative electrode, and an electrolyte. In this secondary battery, the charge capacity of the negative electrode is larger than the discharge capacity of the positive electrode in order to prevent the electrode reactants from being deposited on the surface of the negative electrode during charging. In other words, the electrochemical capacity per unit area of the negative electrode is set to be larger than the electrochemical capacity per unit area of the positive electrode. The secondary battery of this embodiment is a high-charge voltage secondary battery that can exhibit good cycle characteristics without reducing the energy density even when charging at a high voltage of 4.38 V or more.

The type of electrode reactant is not particularly limited, but specifically, it is a light metal such as an alkali metal or an alkaline earth metal. Alkaline metals include lithium, sodium, and potassium, while alkaline earth metals include beryllium, magnesium, and calcium.

In the following, we will use an example where the electrode reactant is lithium. A secondary battery that obtains battery capacity by utilizing the absorption and release of lithium is known as a lithium-ion secondary battery. In this lithium-ion secondary battery, lithium is absorbed and released in an ionic state.

(1-1. Configuration)
Fig. 1A shows a perspective configuration of a secondary battery according to the present embodiment. Fig. 1B shows an exploded view of the configuration of the secondary battery shown in Fig. 1A. Fig. 2 shows a vertical cross-sectional configuration along the height direction of the secondary battery shown in Fig. 1A. Fig. 3 shows an enlarged vertical cross-section of a portion of the secondary battery shown in Fig. 2. However, Fig. 3 shows only some of the components.

For the sake of convenience, in the following, the upper side of the paper in each of Figures 1 and 2 will be described as the upper side of the secondary battery, and the lower side of the paper in each of Figures 1 and 2 will be described as the lower side of the secondary battery.

The secondary battery described here has a three-dimensional shape with a height H smaller than the outer diameter D, i.e., a flat and columnar three-dimensional shape, as shown in FIG. 1A. The three-dimensional shape of the secondary battery shown in FIG. 1A is flat and cylindrical. In this embodiment, the vertical direction of the paper in each of FIG. 1A, FIG. 1B, and FIG. 2 is defined as the height direction Z. Therefore, the height H means the dimension in the height direction Z of the secondary battery of this embodiment. In addition, the outer diameter D means the dimension in the direction perpendicular to the height direction Z of the secondary battery of this embodiment.

The dimensions of the secondary battery are not particularly limited, but as an example, the outer diameter D is 3 mm to 30 mm and the height H is 0.5 mm to 70 mm. However, the ratio of the outer diameter D to the height H (D/H) is greater than 1. In other words, the outer diameter D is greater than the height H. The upper limit of this ratio (D/H) is not particularly limited, but it is preferably 25 or less.

As shown in Figures 1A, 1B, and 2, this secondary battery includes an exterior member 10, a battery element 40, a positive electrode lead 51, a negative electrode lead 52, and insulating films 62 and 63.

[Exterior materials]
As shown in FIGS. 1A, 1B and 2, the exterior member 10 is a hollow structure having an internal space V for housing the battery element 40 and the like.

In the configuration example shown in FIG. 1, the exterior member 10 has a flat and approximately cylindrical outer shape in accordance with the three-dimensional shape of the secondary battery, which is flat and cylindrical. Specifically, the exterior member 10 has a pair of bottoms M1 and M2 facing each other, and a side wall M3 located between the bottoms M1 and M2. That is, the side wall M3 connects the bottoms M1 and M2 and surrounds the battery element 40. The upper end of the side wall M3 is connected to the bottom M1. The lower end of the side wall M3 is connected to the bottom M2. The planar shape of each of the bottoms M1 and M2 is circular. The side wall M3 is a cylindrical member having a circular planar shape.

The exterior member 10 also has a positive electrode terminal plate 11, a negative electrode terminal plate 12, and a cylindrical wall portion 13. The positive electrode terminal plate 11, the negative electrode terminal plate 12, and the cylindrical wall portion 13 are joined to each other, and the internal space of the exterior member 10 is sealed. The positive electrode terminal plate 11 forms the bottom portion M1, the negative electrode terminal plate 12 forms the bottom portion M2, and the cylindrical wall portion 13 forms the side wall portion M3.

The cylindrical wall portion 13 has an internal space that penetrates in the height direction Z. That is, the cylindrical wall portion 13 includes an upper open end 13K1 and a lower open end 13K2 that face each other in the height direction Z. The upper open end 13K1 forms an upper opening as an insertion port through which the battery element 40 can be inserted in the height direction Z. Similarly, the lower open end 13K2 may form a lower opening as an insertion port through which the battery element 40 can be inserted in the height direction Z. The cylindrical wall portion 13 is made of a metal laminate film member having a laminated structure in which, for example, a metal foil 131 and a resin film 132 are bonded together.

As shown in Figs. 1A and 1B, the positive terminal plate 11 is a substantially disc-shaped member that closes the upper opening of the cylindrical wall portion 13. The positive terminal plate 11 is joined to the upper open end 13K1 of the cylindrical wall portion 13 without any gaps. The positive terminal plate 11 includes an outer surface 11S1 extending along a horizontal plane perpendicular to the height direction Z, and an end face 11TS that goes around the outer edge of the outer surface 11S1. As shown in Figs. 1A and 1B, the negative terminal plate 12 is a substantially disc-shaped member that closes the lower opening of the cylindrical wall portion 13. The negative terminal plate 12 is joined to the lower open end 13K2 of the cylindrical wall portion 13 without any gaps. The negative terminal plate 12 includes an outer surface 12S1 extending along a horizontal plane perpendicular to the height direction Z, and an end face 12TS that goes around the outer edge of the outer surface 12S1. In the secondary battery of this embodiment, the positive terminal plate 11, the cylindrical wall portion 13, and the negative terminal plate 12 are integrated to form the exterior member 10. Therefore, the secondary battery of this embodiment has a structure in which the battery element 40 is sealed in the internal space V of the exterior member 10.

The positive electrode terminal plate 11 and the negative electrode terminal plate 12 are external connection terminals for connecting to the outside. The positive electrode terminal plate 11 is connected to the positive electrode 41 (described later) of the battery element 40 via the positive electrode lead 51. The negative electrode terminal plate 12 is connected to the negative electrode 42 (described later) of the battery element 40 via the negative electrode lead 52. The positive electrode terminal plate 11 and the negative electrode terminal plate 12 are each a conductive plate-shaped member made of, for example, a metal material. When using the secondary battery of this embodiment, the positive electrode 41 and the negative electrode 42 are connected to an electronic device via the positive electrode terminal plate 11 and the negative electrode terminal plate 12, respectively. Therefore, the electronic device can operate using the secondary battery as a power source.

The positive electrode terminal plate 11 includes at least one of a plurality of conductive materials such as metal materials and alloy materials. The conductive material is, for example, aluminum or an aluminum alloy. The positive electrode terminal plate 11 may also be a clad material formed by rolling and bonding an aluminum layer to a metal layer made of at least one of Fe (iron), Cu (copper), Ni (nickel), stainless steel, iron alloy, copper alloy, and nickel alloy. More specifically, the positive electrode terminal plate 11 may be a composite member having a three-layer structure of, for example, an Al (aluminum) layer, a stainless steel layer, and a nickel layer. This composite member is arranged so that the Al layer is located inside the exterior member 10 (the inner space V side) and is bonded to the positive electrode lead 51, and the nickel layer is exposed to the outer surface 11S1 of the positive electrode terminal plate 11. The type of stainless steel is not particularly limited, but specifically, SUS304 and SUS316 are examples.

The negative electrode terminal plate 12 contains one or more of a plurality of conductive materials, such as metal materials and alloy materials. The conductive materials are, for example, Fe (iron), Cu (copper), Ni (nickel), stainless steel, iron alloys, copper alloys, and nickel alloys. The type of stainless steel is not particularly limited, but specific examples include SUS304 and SUS316.

The exterior member 10 may further have an adhesive resin layer 133. The positive electrode terminal plate 11 is bonded to the upper open end 13K1 of the cylindrical wall portion 13 via the adhesive resin layer 133. The negative electrode terminal plate 12 is bonded to the lower open end 13K2 of the cylindrical wall portion 13 via the adhesive resin layer 133. More specifically, as shown in FIG. 2 and FIG. 3, the cylindrical wall portion 13 has an inner wall surface 13S facing the battery element 40. The inner wall surface 13S is covered with the adhesive resin layer 133. Here, the end surface 11TS of the positive electrode terminal plate 11 is bonded to the inner wall surface 13S via the adhesive resin layer 133. Similarly, the end surface 12TS of the negative electrode terminal plate 12 is bonded to the inner wall surface 13S near the lower open end 13K2 via the adhesive resin layer 133. This structure electrically insulates the positive electrode terminal plate 11 from the metal foil 131 of the cylindrical wall portion 13, and electrically insulates the negative electrode terminal plate 12 from the metal foil 131 of the cylindrical wall portion 13. Therefore, a short circuit between the positive electrode terminal plate 11 and the negative electrode terminal plate 12 is prevented.

The adhesive resin layer 133 may be made of a thermoplastic resin such as polypropylene or polyethylene. More specifically, a non-oriented polypropylene (CPP) film is preferred. The thickness W133 of the adhesive resin layer 133 (see FIG. 3) may be 10 μm or more and 100 μm or less. The thickness W133 of the adhesive resin layer 133 is preferably 20 μm or more and 50 μm or less. However, the thickness W133U of the portion of the adhesive resin layer 133 sandwiched between the positive electrode terminal plate 11 and the metal foil 131 and the thickness W133L of the portion of the adhesive resin layer 133 sandwiched between the negative electrode terminal plate 12 and the metal foil 131 are both thinner than the thickness W133 of the portion excluding both the gap between the positive electrode terminal plate 11 and the metal foil 131 and the gap between the negative electrode terminal plate 12 and the metal foil 131.

The metal foil 131 constituting the cylindrical wall portion 13 is made of, for example, aluminum or stainless steel. The type of stainless steel is not particularly limited, but specific examples include SUS304 and SUS316. Further examples of the material constituting the metal foil 131 include iron, copper, nickel, iron alloys, aluminum alloys, copper alloys, and nickel alloys. The thickness of the positive electrode terminal plate 11 and the thickness of the negative electrode terminal plate 12 are both preferably thicker than the thickness of the metal foil 131. In addition, the rigidity of the positive electrode terminal plate 11 and the rigidity of the negative electrode terminal plate 12 are both preferably higher than the rigidity of the metal foil 131.

The resin film 132 can be made of polyamide resin or polyethylene terephthalate. It is preferable to use a resin that has higher heat resistance than the resin material used for the adhesive resin layer 133.

[Battery element]
The battery element 40 is a power generating element that causes charge/discharge reactions to proceed, and is housed in the internal space V of the exterior member 10 as shown in Fig. 1B and Fig. 2. The battery element 40 includes a positive electrode 41 and a negative electrode 42. Here, the battery element 40 further includes a separator 43 and an electrolytic solution (not shown) that is a liquid electrolyte.

The center line PC shown in FIG. 2 is a line segment that corresponds to the center of the battery element 40 in the direction along the outer diameter D of the secondary battery (exterior member 10). In other words, the position P0 of the center line PC corresponds to the position of the center of the battery element 40.

The battery element 40 is a so-called electrode winding body. That is, in the battery element 40, for example, as shown in FIG. 2 and FIG. 4, the positive electrode 41 and the negative electrode 42 are stacked in the radial direction R with the separator 43 interposed therebetween. The positive electrode 41, the negative electrode 42, and the separator 43 extend along both the winding direction θ and the height direction Z. The radial direction R is a radial direction perpendicular to the height direction Z of the cylindrical wall portion 13 of the exterior member 10. As shown in FIG. 2, the battery element 40 is wound with the stacked positive electrode 41, the negative electrode 42, and the separator 43 wound around the center line PC as the winding axis. The positive electrode 41 and the negative electrode 42 are wound while maintaining a state in which they face each other with the separator 43 interposed therebetween. Therefore, a winding center space 40K is formed in the center of the battery element 40. Note that FIG. 4 shows a cross-sectional configuration of a portion of the battery element 40.

Here, the positive electrode 41, the negative electrode 42, and the separator 43 are wound so that the separator 43 is disposed at the outermost circumference and the innermost circumference of the wound electrode body. The number of windings of the positive electrode 41, the negative electrode 42, and the separator 43 is not particularly limited and can be set arbitrarily. In addition, the negative electrode 42 is disposed outside the positive electrode 41 at the outermost circumference of the battery element 40. That is, the outermost positive electrode portion located at the outermost circumference of the positive electrode 41 included in the battery element 40 is located inside the outermost negative electrode portion located at the outermost circumference of the negative electrode 42 included in the battery element 40. Here, the outermost positive electrode portion is the outermost portion of the positive electrode 41 in the battery element 40. The outermost negative electrode portion is the outermost portion of the negative electrode 42 in the battery element 40. On the other hand, it is preferable that the negative electrode 42 is disposed inside the positive electrode 41 at the innermost circumference of the battery element 40. That is, the negative electrode innermost circumferential portion located at the innermost periphery of the negative electrode 42 included in the battery element 40 may be located inside the positive electrode innermost circumferential portion located at the innermost periphery of the positive electrode 41 included in the battery element 40. Here, the positive electrode innermost circumferential portion is the innermost part of the positive electrode 41 in the battery element 40. The negative electrode innermost circumferential portion is the innermost part of the negative electrode 42 in the battery element 40.

The battery element 40 has a three-dimensional shape similar to that of the exterior member 10. Specifically, the battery element 40 has a flat, approximately cylindrical three-dimensional shape. Compared to a case in which the battery element 40 has a three-dimensional shape different from that of the exterior member 10, when the battery element 40 is stored inside the exterior member 10, so-called dead space, specifically, a gap between the exterior member 10 and the battery element 40, is less likely to occur. Therefore, the internal space of the exterior member 10 is effectively utilized. As a result, the element space volume increases, and the energy density per unit volume of the secondary battery increases.

(Positive electrode)
The positive electrode 41 is a first electrode used for promoting charge/discharge reactions, and includes a positive electrode current collector 41A and a positive electrode active material layer 41B, as shown in FIG.

The positive electrode current collector 41A has a pair of surfaces on which the positive electrode active material layer 41B is provided. The positive electrode current collector 41A contains a conductive material such as a metal material, and the metal material is aluminum, for example.

The positive electrode active material layer 41B is provided on both sides of the positive electrode collector 41A and contains one or more types of positive electrode active materials capable of absorbing and releasing lithium. However, the positive electrode active material layer 41B may be provided on only one side of the positive electrode collector 41A. The positive electrode active material layer 41B may further contain a positive electrode binder and a positive electrode conductive agent. The method of forming the positive electrode active material layer 41B is not particularly limited, but specifically includes a coating method.

The positive electrode active material contains a lithium compound. This lithium compound is a general term for compounds containing lithium as a constituent element, and more specifically, it is a compound containing one or more transition metal elements as constituent elements together with lithium. This is because a high energy density can be obtained. However, the lithium compound may further contain any one or more of other elements (excluding lithium and transition metal elements). The type of lithium compound is not particularly limited, but specifically includes oxides, phosphate compounds, silicate compounds, and borate compounds. Specific examples of oxides include LiNiO ₂ , LiCoO _{2 ,} and LiMn ₂ O ₄ , and specific examples of phosphate compounds include LiFePO ₄ and LiMnPO ₄ .

The positive electrode binder contains one or more of synthetic rubber and polymer compounds. The synthetic rubber is styrene butadiene rubber, and the polymer compound is polyvinylidene fluoride. The positive electrode conductive agent contains one or more of conductive materials such as carbon materials, and the carbon materials are graphite, carbon black, acetylene black, and ketjen black. However, the conductive material may also be a metal material, a polymer compound, or the like.

(Negative electrode)
The negative electrode 42 is a second electrode used for promoting charge/discharge reactions, and includes a negative electrode current collector 42A and a negative electrode active material layer 42B, as shown in FIG.

The negative electrode current collector 42A has a pair of surfaces on which the negative electrode active material layer 42B is provided. The negative electrode current collector 42A contains a conductive material such as a metal material, and the metal material is, for example, copper.

The negative electrode active material layer 42B is provided on both sides of the negative electrode collector 42A and contains one or more types of negative electrode active materials capable of absorbing and releasing lithium. However, the negative electrode active material layer 42B may be provided on only one side of the negative electrode collector 42A. The negative electrode active material layer 42B may further contain a negative electrode binder and a negative electrode conductor. Details regarding the negative electrode binder and the negative electrode conductor are the same as those regarding the positive electrode binder and the positive electrode conductor. The method of forming the negative electrode active material layer 42B is not particularly limited, but specifically, it is one or more types of a coating method, a gas phase method, a liquid phase method, a thermal spraying method, and a sintering method (sintering method).

The negative electrode active material contains one or both of a carbon material and a metal-based material. This is because a high energy density can be obtained. The carbon material is graphitizable carbon, non-graphitizable carbon, graphite (natural graphite and artificial graphite), etc. The metal-based material is a material containing one or more of metal elements and metalloid elements that can form an alloy with lithium as constituent elements, and the metal elements and metalloid elements are one or both of silicon and tin, etc. However, the metal-based material may be a single element, an alloy, a compound, a mixture of two or more of them, or a material containing two or more phases of them. Specific examples of metal-based materials are TiSi ₂ and SiO _x (0<x≦2, or 0.2<x<1.4), etc.

Here, the height of the negative electrode 42 is greater than the height of the positive electrode 41. That is, as shown in FIG. 4, the upper edge 42UT of the negative electrode 42 protrudes upward from the upper edge 41UT of the positive electrode 41, and the lower edge 42BT of the negative electrode 42 protrudes downward from the lower edge 41BT of the positive electrode 41. This is to prevent the lithium released from the positive electrode 41 from being precipitated. This "height" is the dimension corresponding to the height H of the secondary battery described above, that is, the dimension in the vertical direction (height direction Z) in each of FIG. 1 and FIG. 2. The definition of height described here will be the same hereinafter.

(Separator)
2 and 4, the separator 43 is an insulating porous film disposed between the positive electrode 41 and the negative electrode 42. The separator 43 allows lithium ions to pass through while preventing a short circuit between the positive electrode 41 and the negative electrode 42. The separator 43 contains a polymer compound such as polyethylene.

Here, as shown in FIG. 2, the height of the separator 43 is greater than the height of the negative electrode 42. In other words, the separator 43 preferably protrudes upward from the negative electrode 42 and downward from the negative electrode 42.

(Electrolyte)
The electrolyte is impregnated into each of the positive electrode 41, the negative electrode 42, and the separator 43, and contains a solvent and an electrolyte salt. The solvent contains one or more of non-aqueous solvents (organic solvents) such as carbonate ester compounds, carboxylate ester compounds, and lactone compounds, and the electrolyte containing the non-aqueous solvent is a so-called non-aqueous electrolyte. The electrolyte salt contains one or more of light metal salts such as lithium salt.

[Positive lead]
As shown in Fig. 2, the positive electrode lead 51 is housed in the internal space V of the exterior member 10. The positive electrode lead 51 is a connection wire electrically connected to each of the positive electrode 41 and the positive electrode terminal plate 11. Therefore, the positive electrode terminal plate 11 (bottom part M1) is electrically connected to the positive electrode 41 via the positive electrode lead 51. The secondary battery shown in Fig. 2 includes one positive electrode lead 51. However, the secondary battery may include two or more positive electrode leads 51.

The positive electrode lead 51 is connected to the positive electrode collector 41A so as to protrude upward from the upper edge 41UT of the positive electrode 41. As shown in FIG. 2, the horizontal portion 511 of the positive electrode lead 51 extending along a horizontal plane perpendicular to the height direction Z is connected to the inner surface 11S2 of the positive electrode terminal plate 11. The connection method of the positive electrode lead 51 is not particularly limited, but specifically, it is one or more types of welding methods such as resistance welding and laser welding. The details of the welding method described here are the same hereinafter. The positive electrode lead 51 is electrically insulated from each of the negative electrode terminal plate 12 and the negative electrode 42 of the battery element 40. The horizontal portion 511 of the positive electrode lead 51 is sandwiched between the positive electrode terminal plate 11 and the battery element 40 in the height direction Z.

In this way, the horizontal portion 511 of the positive electrode lead 51 extends along the inner surface 11S2, which is the lower surface of the positive electrode terminal plate 11, and the upper surface of the battery element 40, and is sandwiched between the positive electrode terminal plate 11 and the battery element 40. As a result, the horizontal portion 511 of the positive electrode lead 51 is held by the positive electrode terminal plate 11 and the battery element 40. Therefore, the positive electrode lead 51 is less likely to move inside the exterior member 10. Even if the secondary battery is subjected to external forces such as vibration and impact, the positive electrode lead 51 is less likely to move, and therefore the positive electrode lead 51 is less likely to be damaged. Damage to the positive electrode lead 51 here refers to the occurrence of cracks in the positive electrode lead 51, the positive electrode lead 51 being cut, the positive electrode lead 51 falling off from the positive electrode 41, etc.

The fact that the positive electrode lead 51 is in a state where it is difficult to move inside the exterior member 10 means that the battery element 40 is also in a state where it is difficult to move inside the exterior member 10. Therefore, when the secondary battery is subjected to vibration or impact, it is possible to avoid problems such as the battery element 40, which is an electrode winding body, becoming unwound.

2, an insulating film 62 is disposed between the horizontal portion 511 of the positive electrode lead 51 and the upper surface of the battery element 40. As a result, the positive electrode lead 51 is insulated from the negative electrode 42 of the battery element 40 via the insulating film 62, and a short circuit between the positive electrode lead 51 and the negative electrode 42 is prevented. Alternatively, the horizontal portion 511 of the positive electrode lead 51 may be covered with an insulating sealant. This is because the positive electrode lead 51 is insulated from the negative electrode 42 via the sealant, and a short circuit between the positive electrode lead 51 and the negative electrode 42 is prevented. The sealant is, for example, an insulating member that covers the periphery of the positive electrode lead 51, and is formed by attaching two pieces of insulating tape to the front and back surfaces of the positive electrode lead 51, respectively. The sealant contains one or more types of insulating materials such as insulating polymer compounds, and the insulating material is, for example, polyimide.

The details regarding the material for the positive electrode lead 51 are similar to the details regarding the material for the positive electrode collector 41A. However, the material for the positive electrode lead 51 and the material for the positive electrode collector 41A may be the same as or different from each other.

The connection position of the positive electrode lead 51 to the positive electrode 41 is not particularly limited and can be set arbitrarily. The positive electrode lead 51 is provided separately from the positive electrode current collector 41A. However, since the positive electrode lead 51 is physically continuous with the positive electrode current collector 41A, it may be integrated with the positive electrode current collector 41A.

[Negative lead]
As shown in Fig. 2, the negative electrode lead 52 is housed in the internal space V of the exterior member 10. The negative electrode lead 52 is a connection wire electrically connected to each of the negative electrode 42 and the negative electrode terminal plate 12. Therefore, the negative electrode terminal plate 12 (bottom part M2) is electrically connected to the negative electrode 42 via the negative electrode lead 52. The secondary battery shown in Fig. 2 includes one negative electrode lead 52. However, the secondary battery may include two or more negative electrode leads 52.

As described above, the negative electrode lead 52 is connected to the negative electrode current collector 42A so as to protrude downward from the lower edge 42BT of the negative electrode 42. Furthermore, as shown in FIG. 2, the horizontal portion 521 of the negative electrode lead 52 extending along a horizontal plane perpendicular to the height direction Z is connected to the inner surface 12S2 of the negative electrode terminal plate 12. The method of connecting the negative electrode lead 52 is not particularly limited, but specifically, it is any one or more of welding methods such as resistance welding and laser welding.

The negative electrode lead 52 is electrically insulated from both the positive electrode terminal plate 11 and the positive electrode 41 of the battery element 40. The horizontal portion 521 of the negative electrode lead 52 is sandwiched between the negative electrode terminal plate 12 and the battery element 40 in the height direction Z.

In this way, the horizontal portion 521 of the negative electrode lead 52 extends along the inner surface 12S2, which is the upper surface of the negative electrode terminal plate 12, and the lower surface of the battery element 40, and is sandwiched between the negative electrode terminal plate 12 and the battery element 40. As a result, the horizontal portion 521 of the negative electrode lead 52 is held by the negative electrode terminal plate 12 and the battery element 40. Therefore, the negative electrode lead 52 is less likely to move inside the exterior member 10. Even if the secondary battery is subjected to external forces such as vibration and impact, the negative electrode lead 52 is less likely to move, and therefore the negative electrode lead 52 is less likely to be damaged. Damage to the negative electrode lead 52 here refers to the generation of cracks in the negative electrode lead 52, the negative electrode lead 52 being cut, the negative electrode lead 52 falling off the negative electrode 42, etc.

The fact that the negative electrode lead 52 is in a state where it is difficult to move inside the exterior member 10 means that the battery element 40 is also in a state where it is difficult to move inside the exterior member 10. Therefore, when the secondary battery is subjected to vibration or impact, it is possible to avoid problems such as the battery element 40, which is an electrode winding body, becoming unwound.

2, an insulating film 63 is disposed between the horizontal portion 521 of the negative electrode lead 52 and the lower surface of the battery element 40. This insulates the negative electrode lead 52 from the positive electrode 41 of the battery element 40 via the insulating film 63, preventing a short circuit between the negative electrode lead 52 and the positive electrode 41. Alternatively, the horizontal portion 521 of the negative electrode lead 52 may be covered with an insulating sealant. This is because the negative electrode lead 52 is insulated from the positive electrode 41 via the sealant, preventing a short circuit between the negative electrode lead 52 and the positive electrode 41.

The details regarding the material for the negative electrode lead 52 are the same as those regarding the material for the negative electrode collector 42A. However, the material for the negative electrode lead 52 and the material for the negative electrode collector 42A may be the same or different. An example of the material for the negative electrode lead 52 is nickel.

The connection position of the negative electrode lead 52 to the negative electrode 42 is not particularly limited and can be set arbitrarily. Here, the negative electrode lead 52 is connected to the outermost peripheral portion of the negative electrode 42 that constitutes the battery element 40, which is an electrode winding body.

The negative electrode lead 52 is provided separately from the negative electrode current collector 42A. However, since the negative electrode lead 52 is physically continuous with the negative electrode current collector 42A, it may be integrated with the negative electrode current collector 42A.

[Insulating film]
As shown in Fig. 2, the insulating film 62 is an insulating member disposed between the positive electrode lead 51 and the battery element 40 in the height direction Z. Here, the insulating film 62 has a ring-shaped planar shape having an opening at a position corresponding to the winding center space 40K in the height direction Z. The insulating film 62 may contain one or more types of insulating materials such as insulating polymer compounds. The insulating material contained in the insulating film 62 is polyimide or the like.

As shown in FIG. 2, the insulating film 63 is an insulating member disposed between the negative electrode lead 52 and the battery element 40 in the height direction Z. Here, the insulating film 63 has a ring-shaped planar shape with an opening at a location corresponding to the winding center space 40K in the height direction Z. Details regarding the material for forming the insulating film 63 are similar to those regarding the material for forming the insulating film 62. However, the material for forming the insulating film 63 and the material for forming the insulating film 62 may be the same as each other or different from each other.

[others]
The secondary battery may further include one or more other components. Specifically, the secondary battery includes a safety valve mechanism. This safety valve mechanism is configured to cut off the electrical connection between the exterior member 10 and the battery element 40 when the internal pressure of the exterior member 10 reaches a certain level or higher. The internal pressure of the exterior member 10 reaches a certain level or higher due to a short circuit occurring inside the secondary battery, the secondary battery being heated from the outside, and the like. The location of the safety valve mechanism is not particularly limited, but it is preferable that the safety valve mechanism is provided on either the bottom portion M1 or M2.

The secondary battery may also have an insulator other than the insulating films 62, 63 between the exterior member 10 and the battery element 40. This insulator includes one or more types of insulating film and insulating sheet, etc., and prevents short-circuiting between the exterior member 10 and the battery element 40. The installation range of the insulator is not particularly limited and can be set arbitrarily.

The exterior member 10 is provided with an open-arrangement valve. This open-arrangement valve breaks when the internal pressure of the exterior member 10 reaches a certain level or higher, thereby releasing the internal pressure. There are no particular limitations on the location where the open-arrangement valve is installed, but in particular, either of the bottoms M1 and M2 is preferable, as with the location of the safety valve mechanism described above, and bottom M2 is particularly preferable.

(1-2. Operation)
When the secondary battery is charged, in the battery element 40, lithium is released from the positive electrode 41 and the lithium is absorbed in the negative electrode 42 via the electrolyte. On the other hand, when the secondary battery is discharged, in the battery element 40, lithium is released from the negative electrode 42 and the lithium is absorbed in the positive electrode 41 via the electrolyte. During these charge and discharge operations, lithium is absorbed and released in an ionic state.

(1-3. Manufacturing method)
Next, a method for manufacturing a secondary battery according to the present embodiment will be described with reference to FIGS.

To form the exterior member 10, the positive electrode terminal plate 11, the cylindrical wall portion 13, and the negative electrode terminal plate 12, which are physically separated from one another, are prepared as shown in FIG. 1B. Next, for example, the end face 12TS of the negative electrode terminal plate 12 is brought into contact with the lower open end 13K2 of the cylindrical wall portion 13, and the contact point is heated and pressurized to bond the end face 12TS to the lower open end 13K2.

[Preparation of Positive Electrode]
First, a positive electrode mixture is prepared by mixing a positive electrode active material, a positive electrode binder, a positive electrode conductive agent, and the like. Next, the prepared positive electrode mixture is put into an organic solvent or the like to prepare a paste-like positive electrode mixture slurry. Next, the positive electrode mixture slurry is applied to both sides of the positive electrode current collector 41A to form a positive electrode active material layer 41B. Finally, the positive electrode active material layer 41B is compression molded using a roll press or the like. In this case, the positive electrode active material layer 41B may be heated, or the compression molding may be repeated multiple times. In this way, the positive electrode 41 is prepared.

[Preparation of negative electrode]
The negative electrode 42 is produced by the same procedure as that of the positive electrode 41. Specifically, a negative electrode mixture obtained by mixing a negative electrode active material, a negative electrode binder, a negative electrode conductive agent, and the like is poured into an organic solvent to prepare a paste-like negative electrode mixture slurry, and then the negative electrode mixture slurry is applied to both sides of the negative electrode current collector 42A to form the negative electrode active material layer 42B. Then, the negative electrode active material layer 42B is compression molded using a roll press machine or the like. In this way, the negative electrode 42 is produced.

[Preparation of electrolyte solution]
An electrolyte salt is added to a solvent, whereby the electrolyte salt is dispersed or dissolved in the solvent, and an electrolyte solution is prepared.

[Assembly of secondary battery]
First, the positive electrode lead 51 is connected to the positive electrode 41 (positive electrode current collector 41A) and the negative electrode lead 52 is connected to the negative electrode 42 (negative electrode current collector 42A) using a welding method such as resistance welding.

Then, the positive electrode 41 and the negative electrode 42 are stacked with the separator 43 interposed therebetween, and the stack including the positive electrode 41, the negative electrode 42, and the separator 43 is wound to produce a wound body. This wound body has a similar configuration to that of the battery element 40, except that the positive electrode 41, the negative electrode 42, and the separator 43 are not impregnated with the electrolyte.

Then, the insulating film 63 and the wound body to which the positive electrode lead 51 and the negative electrode lead 52 are respectively connected are housed inside the cylindrical wall portion 13 through the upper opening of the cylindrical wall portion 13. At this time, the negative electrode lead 52 is connected to the negative electrode terminal plate 12 using a welding method such as resistance welding. Next, the insulating film 62 is placed on top of the wound body.

Then, the positive electrode lead 51 is connected to the positive electrode terminal plate 11 using a welding method such as resistance welding.

Next, the electrolyte is injected into the inside of the cylindrical wall portion 13 from the upper opening. This causes the electrolyte to be impregnated into the wound body including the positive electrode 41, the negative electrode 42, and the separator 43, and the battery element 40, which is the wound electrode body, is produced.

Then, the upper opening is closed with the positive terminal plate 11, and the end face 11TS of the positive terminal plate 11 is brought into contact with the upper open end 13K1 of the cylindrical wall portion 13, and the contact point is heated and pressurized to bond the end face 11TS to the upper open end 13K1. This forms the exterior member 10, and the battery element 40 and other components are housed in the internal space V of the exterior member 10, completing the assembly of the secondary battery.

[Stabilization of secondary battery]
The assembled secondary battery is charged and discharged. Various conditions such as the environmental temperature, the number of charge/discharge cycles (number of cycles), and the charge/discharge conditions can be set arbitrarily. As a result, a coating is formed on the surface of the negative electrode 42, etc., and the state of the secondary battery is electrochemically stabilized. Thus, the secondary battery is completed.

(1-4. Actions and Effects)
In this manner, in the secondary battery of the present embodiment, the exterior member 10 housing the battery element 40 has a cylindrical wall portion 13 having a laminated structure of a metal foil 131 and a resin film 132, a positive electrode terminal plate 11 joined to the upper open end 13K1 of the cylindrical wall portion 13, and a negative electrode terminal plate 12 joined to the lower open end 13K2 of the cylindrical wall portion 13. Therefore, compared to the case where an exterior member made of a metal can is used, the dimensions of the exterior member 10 can be reduced without reducing the size of the battery element 40. Specifically, for example, by forming the cylindrical wall portion 13, which has a shape having a higher mechanical strength than the positive electrode terminal plate 11 and the negative electrode terminal plate 12, from a metal laminate film member, it is possible to achieve a thinner, lighter, and smaller-sized exterior member. On the other hand, by forming the positive electrode terminal plate 11 and the negative electrode terminal plate 12 from a metal plate member with high rigidity, the mechanical strength of the entire exterior member 10 is improved, and the shape of the cylindrical wall portion 13 and the shape of the exterior member 10 can be maintained even when an external force is applied.

Therefore, according to the secondary battery of this embodiment, the exterior member 10 can be made thinner, lighter, and smaller while maintaining the size of the battery element 40. Therefore, the secondary battery of this embodiment can achieve a high capacity while having a compact configuration. In addition, the secondary battery of this embodiment has the above-mentioned configuration, and while having a simple configuration, it has excellent sealing properties and can prevent electrolyte leakage. In addition, it is possible to avoid defects such as damage to the positive electrode lead 51, damage to the negative electrode lead 52, and short circuit between the positive electrode 41 and the negative electrode 42. Therefore, the secondary battery of this embodiment also has high reliability. In contrast, for example, in the case of a secondary battery in which all of the exterior members are made of metal laminate film members, the mechanical strength is low and the reliability is poor. In addition, it is necessary to take out the positive electrode terminal and the negative electrode terminal to the outside through the gap at the bonding point of the metal laminate film member, which results in a decrease in volume efficiency.

In particular, in the secondary battery of this embodiment, the outer surface 11S1 and the inner surface 11S2 are flat surfaces perpendicular to the height direction Z, so that the ratio of the volume of the battery element 40 to the volume of the exterior member 10 can be increased, and higher capacity efficiency can be obtained. Also, in the secondary battery of this embodiment, the inner surface 11S2 and the inner surface 12S2 are flat surfaces perpendicular to the height direction Z, so that the battery element 40 can occupy the internal space V of the exterior member 10 without waste. Therefore, higher capacity efficiency can be obtained.

In addition, in the secondary battery of this embodiment, since the exterior member 10 has a cylindrical outer shape, it can have higher mechanical strength compared to, for example, an exterior member having a prismatic or elliptical cylindrical outer shape. However, the secondary battery of the present disclosure also includes cases in which the exterior member has a prismatic or elliptical cylindrical outer shape.

In addition, if the secondary battery is a lithium-ion secondary battery, sufficient battery capacity can be stably obtained by utilizing the absorption and release of lithium.

2. Modifications of the embodiment
(First Modification)
Next, an exterior member 10A as a first modified example of an embodiment of the present disclosure will be described with reference to FIG. 5. FIG. 5 is a cross-sectional view of an enlarged portion of the exterior member 10A as a first modified example, and corresponds to FIG. 3 which shows an enlarged portion of the exterior member 10 of the embodiment. In the exterior member 10 of the embodiment, the entire inner wall surface 13S of the cylindrical wall portion 13 is covered with an adhesive resin layer 133. In contrast, in the exterior member 10A of the first modified example, instead of the adhesive resin layer 133, an adhesive resin layer 14 is provided in the gap between the end surface 11TS of the positive electrode terminal plate 11 and the inner wall surface 13S and in the gap between the end surface 12TS of the negative electrode terminal plate 12 and the inner wall surface 13S. Except for this point, the configuration of the exterior member 10A of the first modified example is substantially the same as the configuration of the exterior member 10 of the embodiment. Note that the adhesive resin layer 14 can be made of a material having the same components as the adhesive resin layer 133. The secondary battery including the exterior member 10A of the first modified example is expected to have the same effects as the secondary battery including the exterior member 10 of the above-described embodiment.

(Second Modification)
Next, an exterior member 10B as a second modified example of an embodiment of the present disclosure will be described with reference to FIG. 6. FIG. 6 is a cross-sectional view of an enlarged portion of the exterior member 10B as a second modified example, and corresponds to FIG. 3 which shows an enlarged portion of the exterior member 10 of the above-mentioned embodiment. In the exterior member 10B of the second modified example, a protrusion 111 protruding toward the negative terminal plate 12 is provided on the outer edge of the positive terminal plate 11, and a protrusion 121 protruding toward the positive terminal plate 11 is provided on the outer edge of the negative terminal plate 12. In addition, in the exterior member 10B, an adhesive resin layer 14 is provided in the gap between the upper end surface 13US of the cylindrical wall portion 13 and the positive terminal plate 11, and in the gap between the lower end surface 13LS of the cylindrical wall portion 13 and the negative terminal plate 12. Except for these points, the configuration of the exterior member 10B of the second modified example is substantially the same as the configuration of the exterior member 10 of the above-mentioned embodiment. In a secondary battery equipped with the exterior member 10B of the second modified example, the same effect as that of the secondary battery equipped with the exterior member 10 of the above-mentioned embodiment can be expected.

(Third Modification)
Next, an exterior member 10C as a third modified example of an embodiment of the present disclosure will be described with reference to FIG. 7. FIG. 7 is a cross-sectional view of an enlarged portion of the exterior member 10C as the third modified example, and corresponds to FIG. 3 which shows an enlarged portion of the exterior member 10 of the above-mentioned embodiment. In the exterior member 10C of the third modified example, a protrusion 111 protruding toward the negative terminal plate 12 is provided on the outer edge of the positive terminal plate 11, and a protrusion 121 protruding toward the positive terminal plate 11 is provided on the outer edge of the negative terminal plate 12. Except for these points, the configuration of the exterior member 10C of the third modified example is substantially the same as the configuration of the exterior member 10 of the above-mentioned embodiment. A secondary battery including the exterior member 10C of the third modified example has a higher mechanical strength than a secondary battery including the exterior member 10 of the above-mentioned embodiment.

(Fourth Modification)
Next, an exterior member 10D as a fourth modified example of an embodiment of the present disclosure will be described with reference to FIG. 8. FIG. 8 is a cross-sectional view showing a schematic configuration of the exterior member 10D as the fourth modified example, and corresponds to FIG. 2 showing the exterior member 10 of the above-mentioned embodiment. In the exterior member 10D of the fourth modified example, each of the inner surface 11S2 of the positive electrode terminal plate 11 and the inner surface 12S2 of the negative electrode terminal plate 12 is a convex curved surface toward the outside of the exterior member 10D. Except for these points, the configuration of the exterior member 10D of the fourth modified example is substantially the same as the configuration of the exterior member 10 of the above-mentioned embodiment. A secondary battery equipped with the exterior member 10D of the fourth modified example has a higher mechanical strength than a secondary battery equipped with the exterior member 10 of the above-mentioned embodiment.

The present technology has been described above using one embodiment and several modified examples, but the configuration of the present technology is not limited to the configuration described in the one embodiment and several modified examples, and can be modified in various ways.

Specifically, the exterior member has a cylindrical outer shape, but the present disclosure is not limited to this. For example, the secondary battery may have an exterior member having a prismatic or elliptical outer shape. In the case of a prismatic exterior member, the corners may be rounded.

In addition, in the above embodiment of the secondary battery, the outer surface of the first electrode terminal plate and the outer surface of the second electrode terminal plate of the exterior member are both flat surfaces, but the present disclosure is not limited to this. For example, at least one of the outer surfaces of the first electrode terminal plate and the second electrode terminal plate may include a recess or a protrusion.

Furthermore, although the electrode reactant has been described as being lithium, the electrode reactant is not particularly limited. Therefore, as described above, the electrode reactant may be other alkali metals such as sodium and potassium, or alkaline earth metals such as beryllium, magnesium, and calcium. In addition, the electrode reactant may be other light metals such as aluminum.

The effects described in this specification are merely examples, and the effects of the present disclosure are not limited to the effects described in this specification. Therefore, other effects may be obtained with respect to the present disclosure.

Furthermore, the present disclosure may take the following aspects.
＜1＞
a battery element having a first electrode and a second electrode;
and an exterior member that houses the battery element,
The exterior member is
a cylindrical wall portion including a first open end and a second open end facing each other in a first direction and having a laminated structure of a metal foil and a resin film;
a first electrode terminal plate joined to the first open end of the cylindrical wall portion;
a second electrode terminal plate joined to the second open end of the cylindrical wall portion.
＜2＞
The exterior member further has an adhesive resin layer,
the first electrode terminal plate is joined to the first open end of the cylindrical wall portion via the adhesive resin layer,
The secondary battery according to <1> above, wherein the second electrode terminal plate is joined to the second open end of the cylindrical wall portion via the adhesive resin layer.
＜3＞
the cylindrical wall portion has an inner wall surface facing the battery element,
The inner wall surface is covered with an adhesive resin layer,
the first electrode terminal plate extends along a first plane perpendicular to the first direction and includes a first end surface;
the second electrode terminal plate extends along the first surface and includes a second end surface,
the first end surface is joined to the inner wall surface via the adhesive resin layer,
The secondary battery according to <1> or <2>, wherein the second end surface is joined to the inner wall surface via the adhesive resin layer.
＜4＞
The secondary battery according to any one of <1> to <3>, wherein each of the first electrode terminal plate and the second electrode terminal plate is made of a metal material.
＜5＞
The secondary battery according to any one of <1> to <4>, wherein a thickness of the first electrode terminal plate and a thickness of the second electrode terminal plate are both greater than a thickness of the metal foil.
＜6＞
The secondary battery according to any one of <1> to <5>, wherein the rigidity of the first electrode terminal plate and the rigidity of the second electrode terminal plate are both higher than the rigidity of the metal foil.

DESCRIPTION OF SYMBOLS 10...Exterior member, M1, M2...Bottom, M3...Side wall part, 11...Positive electrode terminal plate, 11S1...Outer surface, 11S2...Inner surface, 11TS...End surface, 12...Negative electrode terminal plate, 12S1...Outer surface, 12S2...Inner side Surface, 12TS... End surface, 13... Cylindrical wall portion, 13K1... Upper open end, 13K2... Lower open end, 13S... Inner wall surface, 131... Metal foil, 132... Resin film, 133... Adhesive resin layer, 40... Battery element , 41...Positive electrode, 41A...Positive electrode current collector, 41B...Positive electrode active material layer, 42...Negative electrode, 42A...Negative electrode current collector, 42B...Negative electrode active material layer, 51...Positive electrode lead, 52...Negative electrode lead, 62, 63 ...Insulating film, PC...center line, V...internal space.

Claims (6)

a battery element having a first electrode and a second electrode;
and an exterior member that houses the battery element,
The exterior member is
a cylindrical wall portion including a first open end and a second open end facing each other in a first direction and having a laminated structure of a metal foil and a resin film;
a first electrode terminal plate joined to the first open end of the cylindrical wall portion;
a second electrode terminal plate joined to the second open end of the cylindrical wall portion. The exterior member further has an adhesive resin layer,
the first electrode terminal plate is joined to the first open end of the cylindrical wall portion via the adhesive resin layer,
The secondary battery according to claim 1 , wherein the second electrode terminal plate is joined to the second open end of the cylindrical wall portion via the adhesive resin layer. the cylindrical wall portion has an inner wall surface facing the battery element,
The inner wall surface is covered with an adhesive resin layer,
the first electrode terminal plate extends along a first plane perpendicular to the first direction and includes a first end surface;
the second electrode terminal plate extends along the first surface and includes a second end surface,
the first end surface is joined to the inner wall surface via the adhesive resin layer,
The secondary battery according to claim 1 , wherein the second end surface is joined to the inner wall surface via the adhesive resin layer. The secondary battery according to claim 1 , wherein each of the first electrode terminal plate and the second electrode terminal plate is made of a metallic material. The secondary battery according to claim 1 , wherein the thickness of the first electrode terminal plate and the thickness of the second electrode terminal plate are both greater than the thickness of the metal foil. The secondary battery according to claim 1 , wherein the rigidity of the first electrode terminal plate and the rigidity of the second electrode terminal plate are both higher than the rigidity of the metal foil.

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