power storage device

Abstract

An electricity storage device (10) includes a first electrode (21) having a first current collector, a second electrode (22) having a second current collector, and a separator (23). The first electrode (21), the second electrode (22), and the separator (23) constitute a cylindrical winding body (20). The electricity storage device (10) further includes a cylindrical body (32, 61) covering an outer periphery of the cylindrical winding body (20) and having a first opening (31), a sealing body (40) sealing the first opening (31), and at least one first tab (21a) having one end connected to the first current collector and the other end connected to the sealing body (40). The sealing body (40) includes a first member (41) having a first surface (41a) facing a side opposite to the cylindrical winding body (20), and a second member (42) having a second surface (42a) facing the side of the cylindrical winding body (20). 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 portion (43), and the first welded portion (43) is located between the first surface (41a) and the second surface (42a). Thus, the internal resistance of the electricity storage device (10) can be reduced.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to an electrical storage device. BACKGROUND

[0002] Conventionally, an electrical storage device (for example, Patent Literature 1) that stores electric power is known. The electrical storage device of Patent Literature 1 is a battery that includes a wound electrode group in which positive electrode plates and negative electrode plates are wound with a separator interposed therebetween, a battery container that houses the wound electrode group, and a sealing battery lid group that seals the battery container and becomes an external output terminal. In the electrical storage device of Patent Literature 1, a plurality of current collecting tabs that are led out from the wound electrode group are welded to a current collecting ring that is disposed at an upper portion of the wound electrode group. The current collecting ring and the sealing battery lid group are connected to each other by a lead plate.

[0003] PRIOR ART DOCUMENTS

[0004] PATENT LITERATURE

[0005] Patent Literature 1: JP Patent No. 4356209 SUMMARY

[0006] PROBLEMS TO BE SOLVED BY THE INVENTION

[0007] However, most of the current collecting tabs of the electrical storage device of Patent Literature 1 are connected to the sealing battery lid group via the current collecting ring and the lead plate. Therefore, particularly because of the presence of the lead plate, the internal resistance of the electrical storage device becomes large. Under such circumstances, one of the objects of the present disclosure is to reduce the internal resistance of the electrical storage device.

[0008] MEANS FOR SOLVING THE PROBLEMS

[0009] One aspect of the present disclosure relates to an electricity storage device. The electricity storage device includes a first electrode including a first current collector in a band shape and a first active material layer carried on the first current collector, a second electrode including a second current collector in a band shape and a second active material layer carried 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 constituting a columnar wound body. The electricity storage device further includes a cylindrical body covering an outer periphery of the columnar wound body and electrically connected to the second current collector, and having a first opening, a sealing body sealing the first opening, and at least one first tab electrically connecting 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 a side opposite to 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, thereby forming a first welded portion. The first welded portion is located between the first surface and the second surface.

[0010] -Effects of Invention-

[0011] According to the present disclosure, it is possible to reduce internal resistance of an electricity storage device.

[0012] The novel features of the application are set forth with particularity in the appended claims. A better understanding of the features and advantages of the present application will be obtained by reference to the following detailed description that sets forth illustrative BRIEF DESCRIPTION OF DRAWINGS

[0013] Figure 1 is a cross-sectional view schematically showing an electricity storage device of Embodiment 1.

[0014] Figure 2 is a cross-sectional view schematically showing an electricity storage device of Embodiment 2.

[0015] Figure 3 is an unfolded view of a columnar wound body of Embodiment 3.

[0016] Figure 4 is a cross-sectional view schematically showing an electricity storage device of Embodiment 3. DETAILED DESCRIPTION

[0017] Embodiments of the electricity 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 can be exemplified, but other numerical values and materials can also be used as long as the effects of the present disclosure are obtained.

[0018] The power storage device according to the present disclosure includes a first electrode, a second electrode, and a separator. The first electrode, the second electrode, and the separator form a columnar winding body. That is, the first electrode and the second electrode are wound with the separator interposed therebetween.

[0019] The first electrode includes a first current collector and a first active material layer. The second electrode includes a second current collector and a second active material layer.

[0020] The power storage device includes a cylindrical body having a first opening, a sealing body that seals the first opening, and at least one first tab. The first opening has a shape corresponding to a shape of the sealing body, and is generally circular. The first tab is, for example, ribbon-like or strip-like. An insulating material such as a gasket can be present between the cylindrical body and the sealing body.

[0021] The cylindrical body covers an outer periphery of the columnar winding body and is electrically connected to the second current collector. The cylindrical body can include an electrically conductive material.

[0022] The sealing body includes a first member having a first surface facing a side opposite to the columnar winding body and a second member having a second surface facing the side of the columnar winding body. That is, the sealing body can be composed of a plurality of members, and further include other members. The first member and the second member are respectively arranged to partially coincide in an axial direction of the cylindrical body. The first member and the second member can be electrically connected. Thus, a thick electrically conductive path can be formed.

[0023] 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. The other end of the first tab is connected to the sealing body. The first tab can be integral with the first current collector, or can be independent of the first current collector. In the former case, the one end of the first tab is a base end of the first tab, and the other end of the first tab is a front end of the first tab. In the latter case, the one end of the first tab is electrically connected to the first current collector by welding or the like.

[0024] The other end of the first tab is welded to the first surface of the first member and forms a first welded portion. The first welded portion can be formed by laser welding or ultrasonic welding, for example. The first welded portion is located between the first surface and a second surface.

[0025] As above, according to the present disclosure, the first tab is directly connected to the seal body. In other words, there is no intermediate member such as a current collector ring between the first tab and the seal body. Therefore, it is possible to reduce the internal resistance of the power storage device. Further, according to the present disclosure, the first welding portion is located between the first face and the second face, and thus it is possible to make the connection strength of the first welding portion firm. Further, in the case where the first tab is welded to the first face of the first member on the side opposite to the columnar wound body, the welding process is stabilized. This is because there is a firm first member (for example, 500 μm or more in thickness) between the first welding portion and the columnar wound body, and thus spatter at the time of welding is less likely to scatter to the columnar wound body. By stabilizing the welding process, it is easy to increase the strength of the first welding portion and to reduce the connection resistance of the first welding portion.

[0026] The first welding portion can also be sandwiched by the first face and the second face. With this structure, it is possible to reduce the contact resistance between the second member and the first welding portion. Further, the second face can also be joined to the first tab. Specifically, the second member and the first tab can be joined by welding the second member to the first tab from the back side of the second face of the second member. With this structure, it is possible to further reduce the resistance between the first tab and the second member.

[0027] The first face, the first tab, and the second face can also be joined by a common welding portion. With this structure, it is possible to reduce the resistance and to more firmly fix the first tab to the seal plate. In the case where the second member is housed in the recess of the first member, if the outer surface (top face) of the second member has a recess as well as the first member, when the second member and the first tab are joined, the opposing portion of the second member to the first tab is easily thinned, and welding becomes easy.

[0028] The first member can also be a ring-shaped member having a through-hole through which the first tab passes in the center. The second member can also plug the through-hole. The second member can also be disc-shaped. The disc-shaped second member can have a central portion and a flange portion (outer peripheral portion) around the periphery thereof.

[0029] The first member and the second member can also be welded by a second welding portion that is more radially outward than the first welding portion. Thereby, it is possible to further form a thick conductive path.

[0030] The first member can also have a recess that is formed in a ring shape and has the first face as a bottom face. The second member can have a central portion that plugs the through-hole, and an outer peripheral portion that is provided around the central portion. The outer peripheral portion can also be a flange portion of the disc-shaped second member. The outer peripheral portion can also be joined to the first member by the second welding portion all around. In this case, it is possible to form a thick conductive path by the second welding portion, and to seal a gap that can occur between the first member and the second member.

[0031] The first tab can also be joined to the second face and the first face. With this structure, a thick conductive path can be formed and the internal resistance of the power storage device can be reduced.

[0032] The power storage device can also have a plurality of first tabs. The other ends of at least two first tabs can also overlap each other and be welded to the first face of the first member. With this structure, the number of welding locations can be reduced compared to the case where the plurality of first tabs are welded to the first face one by one. A recess that accommodates the end of the first tab can also be formed in the region of the first face where the first tab is arranged, or in the region of the second face that opposes the first tab.

[0033] The cylindrical body can also be formed from a portion of the metal case. For example, the cylindrical body can be formed from the side wall portion of a bottomed cylindrical metal case.

[0034] The cylindrical body can also be formed from a wound body of a metal sheet. The metal sheet can be integral with the second current collector, or can be independent of the second current collector. The thickness TC of the metal sheet can be the same as the thickness T2 of the second current collector, for example, can satisfy the relationship 0.5 ≤ TC / T2 ≤ 1.5. In the case where the cylindrical body is formed from 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 times, to increase the strength of the cylindrical body. With this structure, the process of accommodating the wound body in the metal case can be performed continuously with the process of manufacturing the wound body. Furthermore, since the metal case and the second electrode can be electrically connected even if the bottom of the metal case is not joined to the second current collector, the work required for the connection can be simplified. Furthermore, by electrically connecting the terminal of the wound direction of the second electrode and the metal case, the current collecting path between the metal case and the second electrode can be increased, and thus the resistance can be further reduced. In addition, the terminal of the wound direction of the metal sheet and the outer surface of another position of the metal sheet can be joined to form the cylindrical body.

[0035] Hereinafter, one example of a power storage device according to the present disclosure will be described with reference to the drawings. The structural elements of the power storage device of the one example described below can be applied to the above-described structural elements. The structural elements of the power storage device of the one example described below can be changed based on the above-described description. Furthermore, the matters described below can be applied to the above-described embodiments. Among the structural elements of the power storage device of the one example described below, structural elements that are not necessarily required for the power storage device according to the present disclosure can be omitted. In addition, the drawings shown below are schematic and do not accurately reflect the shape, number, and the like of the actual members.

[0036] Embodiment 1

[0037] 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 of the present embodiment includes a first member 11, a second member 12, and a cylindrical body 13. Figure 1As shown, the power storage device 10 includes a cylindrical winding body 20, a case 30, and a sealing body 40.

[0038] The cylindrical winding body 20 is configured 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.

[0039] The positive electrode 21 has a strip-shaped positive electrode current collector and a positive electrode active material layer carried on the positive electrode current collector. 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 the first current collector. The positive electrode active material layer is an example of the first active material layer. The positive electrode current collector tab 21a is an example of the first tab.

[0040] A strip-shaped metal material is used for the positive electrode current collector. The strip-shaped metal material can 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.

[0041] 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 coating positive electrode mixture slurry containing a positive electrode active material, a conductive agent, and a binder on both surfaces of the positive electrode current collector, drying the coated film, and then calendering. The positive electrode active material is a material that occludes and releases lithium ions. As the positive electrode active material, for example, a lithium-containing transition metal oxide, a transition metal fluoride, a polyanion, a fluorinated polyanion, a transition metal sulfide, or the like is exemplified.

[0042] 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 and protrudes from one end (the upper end in the drawing) of the positive electrode current collector in the longitudinal direction of the positive electrode current collector. Figure 1 A part of the plurality of positive electrode current collector tabs 21a coincide with each other in the circumferential direction in the state in which the positive electrode 21 is wound. The remaining part of the plurality of positive electrode current collector tabs 21a coincide with each other in the circumferential direction in the state in which the positive electrode 21 is wound.

[0043] The negative electrode 22 has a strip-shaped negative electrode current collector, a negative electrode active material layer carried on the negative electrode current collector, 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 the second current collector. The negative electrode active material layer is an example of the second active material layer.

[0044] A strip-shaped metal material is used for the negative electrode current collector. The strip-shaped metal material can 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.

[0045] 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 mixture 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 coated film, and then calendering. The negative electrode active material is a material that occludes and releases lithium ions. As the negative electrode active material, for example, a carbon material, a metal compound, an alloy, a ceramic material, or the like is used.

[0046] 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 of the winding axis of the wound body and constitutes an end surface of the wound body. The negative electrode current collector exposed portion 22a is welded to the negative electrode current collecting plate 51 provided between the cylindrical 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 the welding member 52. In addition, the negative electrode 22 can be connected to the negative electrode current collecting plate 51 or the case 30 using a tab as with the positive electrode 21.

[0047] The case 30 is formed in a bottomed cylindrical shape having the first opening 31 and accommodates the cylindrical 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 cylindrical wound body 20 and is electrically connected to the negative electrode current collector. The side wall portion 32 of the case 30 is one example of a cylindrical body.

[0048] The closure body 40 seals the first opening 31 of the case 30. The closure body 40 is electrically connected to the positive electrode current collector via 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 front end of the positive electrode current collecting tab 21a is connected to the closure body 40. The closure body 40 is made of metal and functions as an external positive electrode terminal. The closure body 40 and the case 30 are insulated from each other by a gasket 70. The closure body 40 can have an explosion-proof mechanism not shown.

[0049] The closure body 40 has a first member 41 including a first surface 41a facing a side opposite to the cylindrical wound body 20 (an upper side in FIG. 1) and a second member 42 including a second surface 42a facing the side of the cylindrical wound body 20. Figure 1 The first member 41 is a ring-shaped member having a through-hole 41b through which the positive electrode current collecting tab 21a passes in the center. The second member 42 is a plate-shaped member that plugs the through-hole 41b.

[0050] The front end of the positive current collector 21a is welded to the first surface 41a of the first member 41 to form a first weld portion 43. This first weld portion 43 is sandwiched between the first surface 41a and the second surface 42a, with pressure applied from both sides. In the first weld portion 43, the front ends of multiple positive current collectors 21a overlap each other and are welded to the first surface 41a of the first member 41. The area of ​​the first surface 41a forming the first weld portion 43 may also have a recess deeper than the combined thickness of the front ends of the multiple positive current collectors 21a.

[0051] The first member 41 has a recess 41c formed in an annular shape with a first surface 41a as its bottom surface. The second member 42 has a central portion 42b that blocks 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 of the outer peripheral portion 42c extends all the way around the circumference and is welded to the first member 41 by a second weld portion 44 that is radially outward than the first weld portion 43. Thus, even if 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 within the housing 30 can be ensured.

[0052] Implementation Method 2

[0053] Embodiment 2 of this disclosure will be described. The structures of the first component 41 and the second component 42 of the energy storage device 10 in this embodiment differ from those in Embodiment 1 described above. Hereinafter, the aspects that differ from Embodiment 1 will be mainly described.

[0054] like Figure 2 As shown, the first component 41 does not have a recess to accommodate the second component 42. Furthermore, the outer peripheral edges of the first component 41 and the second component 42 overlap and are held by a sealing gasket 70. The first component 41 and the second component 42 are welded together at their outer peripheral edges via a second weld portion 44. In this case, the first weld portion 43 is not subjected to pressure from the second surface 42a, and a gap exists between the first surface 41a and the second surface 42a that is sufficiently large than the thickness of the front end of the positive current collector 21a. Therefore, the reduction effect of contact resistance in the first weld portion 43 is slower than in Embodiment 1. However, since the configuration of the second component 42 is not affected by the thickness of the front end of the positive current collector 21a, the manufacturing process is easily stabilized.

[0055] Implementation Method 3

[0056] Embodiment 3 of this disclosure will be described. The energy storage device 10 of this embodiment differs from Embodiment 1 in that it does not have a metal casing 30. Hereinafter, the differences from Embodiment 1 will be mainly described.

[0057] like Figure 3and Figure 4 In the present embodiment, a cylindrical body 61 composed of a winding body of a metal sheet assumes the function of the case 30 of Embodiment 1. The metal sheet is integrally formed with the negative current collector, but is not limited thereto. The columnar winding body 20 is wound from the left to the right. Figure 3 The cylindrical body 61 covers the outer periphery of the columnar winding body 20 and is electrically connected with the negative current collector.

[0058] 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. The second opening 61a is sealed by a metal plate 62 (e.g., a copper plate). The cylindrical body 61 and the metal plate 62 are joined to each other by welding over the entire periphery. At this time, the negative current collector exposed portion can be formed as in Embodiment 1, and the negative current collector exposed portion can be joined to the metal plate 62 by welding.

[0059] With regard to the presently preferred embodiments, the present application has been described, but the disclosure is not to be construed as limiting. Various modifications and changes are apparent to those skilled in the art which fall within the true spirit and scope of the present application. Accordingly, the appended claims should be construed to cover all such modifications and changes.

[0060] Industrial Applicability

[0061] The present disclosure can be utilized in an electrical storage device.

[0062] -Explanation of Symbols-

[0063] 10: Electrical storage device

[0064] 20: Columnar winding body

[0065] 21: Positive electrode (first electrode)

[0066] 21a: Positive current collector tab (first tab)

[0067] 22: Negative electrode (second electrode)

[0068] 22a: Negative current collector exposed portion

[0069] 23: Spacer

[0070] 30: Case

[0071] 31: First opening

[0072] 32: Side wall portion (cylindrical body)

[0073] 40: Sealing body

[0074] 41: first member

[0075] 41a: first surface

[0076] 41b: through-hole

[0077] 41c: recess

[0078] 42: second member

[0079] 42a: second surface

[0080] 42b: central portion

[0081] 42c: outer peripheral portion

[0082] 43: first welding portion

[0083] 44: second welding portion

[0084] 51: negative electrode current collector

[0085] 52: welding member

[0086] 61: cylindrical body

[0087] 61a: second opening

[0088] 62: metal plate

[0089] 70: gasket

[0090] 80: adhesive

Claims

1. An electricity storage device comprising: a first electrode having a first current collector in a band shape and a first active material layer supported on the first current collector; and a second electrode having a second current collector in a band shape and a second active material layer supported on the second current collector, the first electrode, the second electrode, and a separator interposed between the first electrode and the second electrode constituting a columnar wound body, the electricity storage device further comprising: a cylindrical body covering an outer periphery of the columnar wound body and electrically connected to the second current collector, and having a first opening; a sealing body sealing the first opening; and at least one first tab electrically connecting the first current collector and the sealing body, one end of the first tab being connected to the first current collector, the other end of the first tab being connected to the sealing body, the sealing body having a first member including a first surface facing a side opposite to the columnar wound body, and a second member including a second surface facing the columnar wound body side, the first member being a ring-shaped member having a through-hole through which the first tab passes in a center thereof, the other end of the first tab being welded to the first surface of the first member to form a first welded portion, the first welded portion being located between the first surface and the second surface.

2. The electricity storage device according to claim 1, wherein the second member plugs the through-hole. The second electrode has a second current collector in a band shape and a second active material layer supported on the second current collector.

3. The electricity storage device according to claim 2, wherein the first member and the second member are welded by a second welded portion located more radially outward than the first welded portion.

4. The electricity storage device according to claim 3, wherein the first member has a recess formed in a ring shape and having the first surface as a bottom surface, the second member has a central portion plugging the through-hole, and an outer peripheral portion provided around the central portion, the outer peripheral portion is engaged with the first member by the second welded portion throughout the entire periphery.

5. The electricity storage device according to any one of claims 1 to 4, wherein the first tab is engaged with the second surface and the first surface.

6. The electricity storage device according to any one of claims 1 to 4, wherein the electricity storage device comprises 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.

7. The electricity storage device according to any one of claims 1 to 4, wherein the cylindrical body is constituted by a part of a metal case.

8. The electricity storage device according to any one of claims 1 to 4, wherein the cylindrical body is constituted by a wound body of a metal sheet. ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​

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