Electric energy storage device

Abstract

A power storage device 10 comprises: a first electrode 21 having a first collector body; a second electrode 22 having a second collector body; and a separator 23. The first electrode 21, the second electrode 22, and the separator 23 constitute a columnar wound body 20. The power storage device 10 further comprises: tubular bodies 32, 61 that cover the outer circumference of the columnar wound body 20, and each have a first opening 31; a sealing body 40 that seals the first opening 31; and at least one first tab 21a, one end of which is connected to the first collector body, and the other end of which is connected to the sealing body 40. The sealing body 40 has: a first member 41 that includes a first surface 41a that faces the side opposite the columnar wound body 20; and a second member 42 that includes a second surface 42a that faces the columnar wound body 20 side. The other end of the first tab 21a is welded to the first surface 41a of the first member 41 to form a first welded section 43, the first welded section 43 being positioned between the first surface 41a and the second surface 42a. The internal resistance of the power storage device 10 can thereby be reduced.

Description

Technical Field

[0001] The present disclosure relates to a power storage device.

Background Art

[0002] Conventionally, a power storage device for storing electric power has been known (for example, Patent Document 1). The power storage device of Patent Document 1 is a battery including a wound electrode group in which a positive electrode plate and a negative electrode plate are wound with a separator interposed therebetween, a battery container for housing the wound electrode group, and a sealed battery lid group for sealing the battery container and serving as an external output terminal. In the power storage device of Patent Document 1, a large number of current collecting tabs led out from the wound electrode group are welded to a current collecting ring disposed above the wound electrode group. The current collecting ring and the sealed battery lid group are connected to each other by a lead plate.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, in the power storage device of Patent Document 1, a large number of current collecting tabs are connected to the sealed battery lid group via the current collecting ring and the lead plate. Therefore, particularly due to the presence of the lead plate, the internal resistance of the power storage device increases. In such a situation, one of the objects of the present disclosure is to reduce the internal resistance of the power storage device.

Means for Solving the Problems

[0005] One aspect of the present disclosure relates to a power storage device. The power storage device includes a first electrode having a strip-shaped first current collector and a first active material layer supported on the first current collector, a second electrode having a strip-shaped second current collector and a second active material layer supported on the second current collector, and a separator interposed between the first electrode and the second electrode. The first electrode, the second electrode, and the separator form a columnar wound body. The power storage device further includes a cylindrical body that covers the outer periphery of the columnar wound body and is electrically connected to the second current collector, and has a first opening, a sealing body that seals the first opening, and at least one first tab that electrically connects the first current collector and the sealing body. One end of the first tab is connected to the first current collector, and the other end of the first tab is connected to the sealing body. The sealing body includes a first member including a first surface facing away from the columnar wound body and a second member including a second surface facing the columnar wound body side. The other end of the first tab is welded to the first surface of the first member to form a first welded portion, and the first welded portion is located between the first surface and the second surface.

Advantages of the Invention

[0006] According to the present disclosure, the internal resistance of the power storage device can be reduced.

[0007] The novel features of the present invention are described in the appended claims. However, the present invention relates to both the configuration and the content, and will be better understood from the following detailed description in conjunction with the drawings and other objects and features of the present application.

Brief Description of the Drawings

[0008]

Figure 1

Figure 2

Figure 3

Figure 4

Modes for Carrying Out the Invention

[0009] Examples of embodiments of the power storage device according to the present disclosure will be described below. However, the present disclosure is not limited to the examples described below. In the following description, specific numerical values and materials may be exemplified, but other numerical values and materials may be applied as long as the effects of the present disclosure can be obtained.

[0010] The power storage device according to the present disclosure includes a strip-shaped first electrode, a strip-shaped second electrode, and a separator interposed between the first electrode and the second electrode. The first electrode, the second electrode, and the separator constitute a columnar wound body. That is, the first electrode and the second electrode are wound with the separator interposed therebetween.

[0011] The first electrode has a strip-shaped first current collector and a first active material layer supported by the first current collector. The second electrode has a strip-shaped second current collector and a second active material layer supported by the second current collector.

[0012] The power storage device further includes a cylindrical body having a first opening, a sealing body for sealing the first opening, and at least one first tab. The outer shape of the first opening and the outer shape of the sealing body correspond to each other and are usually circular. The first tab is, for example, ribbon-shaped or strip-shaped. An insulating material such as a gasket may be interposed between the cylindrical body and the sealing body.

[0013] The cylindrical body covers the outer periphery of the columnar wound body and is electrically connected to the second current collector. The cylindrical body may be made of a conductive material.

[0014] The sealing body has a first member including a first surface facing away from the columnar wound body and a second member including a second surface facing the columnar wound body side. That is, the sealing body is composed of a plurality of members and may further include another member. The first member and the second member are arranged so that they partially overlap in the axial direction of the cylindrical body. The first member and the second member may be electrically conductive. Thereby, a thick conductive path can be formed.

[0015] The first tab electrically connects the first current collector and the sealing body. One end of the first tab is connected to the first current collector, and the other end of the first tab is connected to the sealing body. The first tab may be integral with the first current collector or separate from the first current collector. In the former case, one end of the first tab becomes the base end of the first tab, and the other end of the first tab becomes the tip of the first tab. In the latter case, one end of the first tab is electrically connected to the first current collector by welding or the like.

[0016] The other end of the first tab is welded to the first surface of the first member to form a first welded portion. This first welded portion may be formed, for example, by laser welding or ultrasonic welding. The first welded portion is located between the first surface and the second surface.

[0017] As described above, according to the present disclosure, the first tab is directly connected to the sealing body. That is, there is no intermediate member such as a current collecting ring between the first tab and the sealing body. Therefore, the internal resistance of the power storage device can be reduced. Further, according to the present disclosure, since the first welded portion is located between the first surface and the second surface, the connection strength of the first welded portion can be strengthened. Furthermore, when the first tab is welded to the first surface of the first member facing away from the columnar wound body, the welding process is stabilized. This is because a robust first member (thickness is, for example, 500 μm or more) is interposed between the first welded portion and the columnar wound body, so that spatter during welding is less likely to scatter onto the columnar wound body. By stabilizing the welding process, it becomes easier to increase the strength of the first welded portion and reduce the connection resistance of the first welded portion.

[0018] The first welded portion may be sandwiched between the first surface and the second surface. With this configuration, the contact resistance between the second member and the first welded portion can be reduced. Further, the second surface may also be joined to the first tab. Specifically, the second member and the first tab may be joined by welding them from the back side of the second surface of the second member. With this configuration, the resistance between the first tab and the second member can be further reduced.

[0019] The first surface, the first tab, and the second surface may be joined by a common weld. With this configuration, the resistance can be reduced and the first tab can be more firmly fixed to the sealing plate. When the second member is accommodated in the recess of the first member, if the outer surface (top surface) of the second member also has a recess similar to the first member, when joining the second member and the first tab, the portion of the second member facing the first tab tends to be thin, facilitating welding.

[0020] The first member may be an annular member having a through-hole through which the first tab passes at the center. The second member may block the through-hole. The second member may be disc-shaped. The disc-shaped second member may have a central portion and a flange portion (outer peripheral portion) at its periphery.

[0021] The first member and the second member may be welded by a second weld portion radially outside the first weld portion. Thereby, a thicker conductive path can be formed.

[0022] The first member may have a recess formed in an annular shape with the first surface as the bottom surface. The second member may have a central portion that blocks the through-hole and an outer peripheral portion provided around the central portion. The outer peripheral portion may be the flange portion of the disc-shaped second member. The outer peripheral portion may be joined to the first member by a second weld portion over the entire circumference. In this case, the second weld portion can form a thick conductive path and seal the gap that may occur between the first member and the second member.

[0023] The first tab may be joined to the second surface and the first surface. With this configuration, a thick conductive path can be formed to reduce the internal resistance of the energy storage device.

[0024] The energy storage device may include a plurality of first tabs. The other ends of at least two first tabs may overlap each other and be welded to the first surface of the first member. According to this configuration, the number of welding points can be reduced compared to the case where the plurality of first tabs are welded to the first surface one by one. A recess for accommodating the end portion of the first tab may be formed in the region where the first tab is disposed on the first surface or in the region facing the first tab on the second surface.

[0025] The cylindrical body may be constituted by a part of the metal case. For example, the cylindrical body may be constituted by the side wall portion of a bottomed cylindrical metal case.

[0026] The cylindrical body may be constituted by a wound body of a metal sheet. The metal sheet may be integral with the second current collector or may be separate from the second current collector. The thickness TC of the metal sheet may be the same as the thickness T2 of the second current collector, or may satisfy, for example, the relationship of 0.5 ≦ TC / T2 ≦ 1.5. When the cylindrical body is constituted by a metal sheet, it is desirable to wind the metal sheet around the outer periphery of the columnar wound body, for example, two or more turns to increase the strength of the cylindrical body. With this configuration, it becomes possible to perform the step of creating the wound body and the step of accommodating the wound body in the metal case continuously. Further, since the metal case and the second electrode can be electrically connected without joining the bottom of the metal case and the second current collecting plate, the work required for connection can be simplified. Further, by electrically connecting the end of the second electrode in the winding direction and the metal case, the current collecting path between the metal case and the second electrode increases and the resistance can be further reduced. Note that the end of the metal sheet in the winding direction can be joined to the outer surface of another portion of the metal sheet to form a cylindrical body.

[0027] Hereinafter, an example of the power storage device according to the present disclosure will be specifically described with reference to the drawings. The above-described components can be applied to the components of the power storage device of the example described below. The components of the power storage device of the example described below can be changed based on the above description. Further, the matters described below may be applied to the above-described embodiment. Among the components of the power storage device of the example described below, components that are not essential to the power storage device according to the present disclosure may be omitted. Note that the drawings shown below are schematic and do not accurately reflect the actual shape and number of members.

[0028] <<Embodiment 1>> Embodiment 1 of the present disclosure will be described. The power storage device 10 of the present embodiment is a lithium-ion secondary battery, but is not limited thereto. As shown in FIG. 1, the power storage device 10 includes a columnar wound body 20, a case 30, and a sealing body 40.

[0029] The columnar wound body 20 is formed by winding a strip-shaped positive electrode 21, a strip-shaped negative electrode 22, and a separator 23 interposed between the positive electrode 21 and the negative electrode 22. The positive electrode 21 is an example of a first electrode. The negative electrode 22 is an example of a second electrode.

[0030] The positive electrode 21 has a strip-shaped positive electrode current collector and a positive electrode active material layer supported thereon. A plurality of positive electrode current collector tabs 21a are connected to the positive electrode current collector. The positive electrode current collector is an example of a first current collector. The positive electrode active material layer is an example of a first active material layer. The positive electrode current collector tab 21a is an example of a first tab.

[0031] A strip-shaped metal material is used for the positive electrode current collector. The strip-shaped metal material may be a metal foil, a metal porous body, or the like. As the metal material, aluminum, an aluminum alloy, nickel, titanium, or the like can be used. The thickness of the positive electrode current collector is, for example, 10 μm or more and 100 μm or less.

[0032] The positive electrode active material layer contains, for example, a positive electrode active material, a conductive agent, and a binder. The positive electrode active material layer is obtained, for example, by applying a positive electrode composite material slurry containing a positive electrode active material, a conductive agent, and a binder to both surfaces of the positive electrode current collector, drying the coating film, and then rolling it. The positive electrode active material is a material that occludes and releases lithium ions. Examples of the positive electrode active material include lithium-containing transition metal oxides, transition metal fluorides, polyanions, fluorinated polyanions, transition metal sulfides, and the like.

[0033] The plurality of positive electrode current collector tabs 21a are formed integrally with the positive electrode current collector. Each positive electrode current collector tab 21a extends from one end (the upper end in FIG. 1) along the longitudinal direction of the positive electrode current collector. A part of the plurality of positive electrode current collector tabs 21a has the same circumferential position in the state where the positive electrode 21 is wound. The remaining part of the plurality of positive electrode current collector tabs 21a has the same circumferential position in the state where the positive electrode 21 is wound.

[0034] The negative electrode 22 includes a strip-shaped negative electrode current collector, a negative electrode active material layer supported thereon, and a negative electrode current collector exposed portion 22a formed at one end in the width direction of the negative electrode current collector. The negative electrode current collector is an example of a second current collector. The negative electrode active material layer is an example of a second active material layer.

[0035] A strip-shaped metal material is used for the negative electrode current collector. The strip-shaped metal material may be a metal foil, a metal porous body, or the like. As the metal material, copper, a copper alloy, nickel, stainless steel, or the like can be used. The thickness of the negative electrode current collector is, for example, 10 μm or more and 100 μm or less.

[0036] The negative electrode active material layer contains, for example, a negative electrode active material, a conductive agent, and a binder. The negative electrode active material layer is obtained, for example, by applying a negative electrode composite material slurry containing a negative electrode active material, a conductive agent, and a binder to both surfaces of the negative electrode current collector except for the negative electrode current collector exposed portion 22a, drying the coating film, and then rolling. The negative electrode active material is a material that occludes and releases lithium ions. Examples of the negative electrode active material include carbon materials, metal compounds, alloys, and ceramic materials.

[0037] The negative electrode current collector exposed portion 22a is formed integrally with the negative electrode current collector. The negative electrode current collector exposed portion 22a protrudes from one end in the winding axis direction of the wound body and constitutes the end face of the wound body. The negative electrode current collector exposed portion 22a is welded and connected to a negative electrode current collecting plate 51 provided between the columnar wound body 20 and the bottom surface of the case 30. The negative electrode current collecting plate 51 is welded to the inner bottom surface of the case 30 by a welding member 52. Note that, similar to the positive electrode 21, a tab may be used in the negative electrode 22 to connect to the negative electrode current collecting plate 51 or the case 30.

[0038] The case 30 is formed in a bottomed cylindrical shape having a first opening 31 and houses the columnar wound body 20 and a non-aqueous electrolyte (not shown). The case 30 is made of metal and functions as an external negative electrode terminal. The side wall portion 32 of the case 30 covers the outer periphery of the columnar wound body 20 and is electrically connected to the negative electrode current collector. The side wall portion 32 of the case 30 is an example of a cylindrical body.

[0039] The sealing body 40 seals the first opening 31 of the case 30. The sealing body 40 is electrically connected to the positive electrode current collector through a plurality of positive electrode current collecting tabs 21a. The base end of the positive electrode current collecting tab 21a is connected to the first current collector, and the tip of the positive electrode current collecting tab 21a is connected to the sealing body 40. The sealing body 40 is made of metal and functions as an external positive electrode terminal. The sealing body 40 and the case 30 are insulated from each other by a gasket 70. The sealing body 40 may have an explosion-proof mechanism (not shown).

[0040] The sealing body 40 has a first member 41 including a first surface 41a facing the side opposite to the columnar wound body 20 (the upper side in FIG. 1), and a second member 42 including a second surface 42a facing the columnar wound body 20 side. The first member 41 is an annular member having a through hole 41b through which the positive electrode current collecting tab 21a passes at the center. The second member 42 is a plate-like member that closes the through hole 41b.

[0041] The tip of the positive electrode current collecting tab 21a is welded to the first surface 41a of the first member 41 to form a first welded portion 43. This first welded portion 43 is sandwiched between the first surface 41a and the second surface 42a, and pressure is applied from both the first surface 41a and the second surface 42a. At the first welded portion 43, the tips of the plurality of positive electrode current collecting tabs 21a overlap each other and are welded to the first surface 41a of the first member 41. The region of the first surface 41a where the first welded portion 43 is formed may have a recess deeper than the total thickness of the tips of the plurality of positive electrode current collecting tabs 21a.

[0042] The first member 41 has a recess 41c formed in an annular shape with the first surface 41a as the bottom surface. The second member 42 has a central portion 42b that closes the through hole 41b of the first member 41 and an outer peripheral portion 42c that is accommodated in the recess 41c. The peripheral edge portion of the outer peripheral portion 42c is welded and joined to the first member 41 by a second welded portion 44 radially outside the first welded portion 43 over the entire circumference. Thereby, even when a gap is formed between the first surface 41a of the first member 41 and the second surface 42a of the second member 42, sufficient sealing performance inside the case 30 can be ensured.

[0043] 《Embodiment 2》 Embodiment 2 of the present disclosure will be described. The power storage device 10 of this embodiment differs from that of the above Embodiment 1 in the configurations of the first member 41 and the second member 42. Hereinafter, the differences from the above Embodiment 1 will be mainly described.

[0044] As shown in FIG. 2, the first member 41 does not have a recess for accommodating the second member 42. Also, the outer peripheral edge of the first member 41 and the outer peripheral edge of the second member 42 overlap each other and are sandwiched by a gasket 70. The first member 41 and the second member 42 are welded and joined to each other by a second welding portion 44 at the outer peripheral edge. In this case, no pressure is applied to the first welding portion 43 from the second surface 42a, and there is a gap between the first surface 41a and the second surface 42a that is sufficiently larger than the thickness of the tip of the positive electrode current collector tab 21a. Therefore, the effect of reducing the contact resistance in the first welding portion 43 is gentler than that in Embodiment 1. However, since the arrangement of the second member 42 is not affected by the thickness of the tip of the positive electrode current collector tab 21a, the manufacturing process is likely to be stabilized.

[0045] 《Embodiment 3》 Embodiment 3 of the present disclosure will be described. The power storage device 10 of this embodiment differs from that of the above Embodiment 1 in that it does not include a metal case 30. Hereinafter, the differences from the above Embodiment 1 will be mainly described.

[0046] As shown in FIGS. 3 and 4, in this embodiment, a cylindrical body 61 formed of a wound body of a metal sheet assumes the function corresponding to the case 30 of Embodiment 1. The metal sheet is integrally formed with the negative electrode current collector, but is not limited thereto. The columnar wound body 20 is wound from left to right in FIG. 3. The cylindrical body 61 covers the outer periphery of the columnar wound body 20 and is electrically connected to the negative electrode current collector.

[0047] The first opening 31 of the cylindrical body 61 is sealed by the sealing body 40. The cylindrical body 61 and the sealing body 40 are insulated from each other by an insulating adhesive 80. The cylindrical body 61 has a second opening 61a on the side opposite to the first opening 31. This second opening 61a is sealed by a metal plate 62 (for example, a copper plate). The cylindrical body 61 and the metal plate 62 are welded and joined to each other over the entire circumference. At this time, a negative electrode current collector exposed portion may be formed on the negative electrode in the same manner as in Embodiment 1, and the negative electrode current collector exposed portion and the metal plate 62 may be welded and joined.

[0048] Although the present invention has been described with respect to the presently preferred embodiments, such disclosure should not be construed in a limiting sense. Various modifications and alterations will no doubt become apparent to those skilled in the art in the technical field to which this invention pertains upon reading the above disclosure. Accordingly, the appended claims are to be construed as including all modifications and alterations without departing from the true spirit and scope of this invention.

Industrial Applicability

[0049] This disclosure can be used in a power storage device.

Explanation of Reference Numerals

[0050] 10: Power storage device 20: Columnar wound body 21: Positive electrode (first electrode) 21a: Positive electrode current collector tab (first tab) 22: Negative electrode (second electrode) 22a: Negative electrode current collector exposed portion 23: Separator 30: Case 31: First opening 32: Side wall portion (cylindrical body) 40: Sealing body 41: First member 41a: First surface 41b: Through hole 41c: Recess 42: Second member 42a: Second surface 42b: Central portion 42c: Outer peripheral portion 43: First welding part 44: Second welding part 51: Negative current collector 52: Welding member 61: Cylindrical body 61a: Second opening 62: Metal plate 70: Gasket 80: Adhesive

Claims

1. A first electrode having a strip-shaped first current collector and a first active material layer supported on the first current collector, A second electrode having a strip-shaped second current collector and a second active material layer supported on the second current collector, A separator interposed between the first electrode and the second electrode, Comprising, The first electrode, the second electrode, and the separator constitute a columnar wound body, A cylindrical body that covers the outer periphery of the columnar wound body and is electrically connected to the second current collector and has a first opening, A sealing body that seals the first opening, At least one first tab that electrically connects the first current collector and the sealing body, Further comprising, One end of the first tab is connected to the first current collector, The other end of the first tab is connected to the sealing body, The sealing body has a first member including a first surface facing away from the columnar wound body and a second member including a second surface facing the columnar wound body side, The other end of the first tab is welded to the first surface of the first member to form a first welded portion, The first welded portion is a power storage device located between the first surface and the second surface.

2. The first member is an annular member having a through hole through which the first tab passes in the center, The second member closes the through hole, and the power storage device according to claim 1.

3. The first member and the second member are welded by a second welded portion radially outside the first welded portion, and the power storage device according to claim 2.

4. The first member is formed in an annular shape and has a concave portion having the first surface as a bottom surface, The second member has a central portion that closes the through hole and an outer peripheral portion provided around the central portion, The outer peripheral portion is joined to the first member by the second welded portion over the entire circumference, and the power storage device according to claim 3.

5. The first tab is joined to the second surface and the first surface, and the power storage device according to any one of claims 1 to 4.

6. Comprising a plurality of the first tabs, The other ends of at least two of the first tabs overlap each other and are welded to the first surface of the first member, and the power storage device according to any one of claims 1 to 5.

7. The cylindrical body is constituted by a part of a metal case, and the power storage device according to any one of claims 1 to 6.

8. The cylindrical body is constituted by a wound body of a metal sheet, and the power storage device according to any one of claims 1 to 6.

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