Power storage cell and method for manufacturing the same

Abstract

To reduce an occupied space of a tab bundle.SOLUTION: A power storage cell includes a case and an electrode stack. The case stores the electrode stack therein. The case includes a case main body and a lid. The case main body includes an opening. The lid closes the opening. An electrode terminal is provided in the lid. The electrode stack is formed by laminating a plurality of electrode sheets. Each of the plurality of electrode sheets includes a collector tab. A tab bundle is formed by laminating a plurality of collector tabs. In at least a part of the tab bundle, lengths of a plurality of collector tabs are different from each other. The tab bundle is joined to the electrode terminal. Within the case, the tab bundle is stored in a bent state.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present disclosure relates to an energy storage cell and a method for manufacturing the same. [Background technology]

[0002] Japanese Patent Application Laid-Open No. 2001-283824 discloses that a plurality of strip-shaped current collecting tabs are connected together at one location on a terminal. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2001-283824 Summary of the Invention [Problem to be solved by the invention]

[0004] The energy storage cell includes, for example, a case and a power generating element. The case houses the power generating element. The power generating element may be, for example, a stacked type. A stacked type power generating element is also called an electrode stack. The electrode stack may be formed by stacking electrode sheets. Each electrode sheet has a current collecting tab at its end. Therefore, a tab bundle is formed at the end of the electrode stack by stacking the current collecting tabs. The volume of the tab bundle may increase as the number of stacked electrode sheets increases. The tab bundle does not contribute to the battery capacity. The energy density of the energy storage cell may decrease as the tab bundle occupies a larger space inside the case.

[0005] An object of the present disclosure is to reduce the space occupied by a tab bundle. [Means for solving the problem]

[0006] The technical configuration and effects of the present disclosure will be described below. However, the mechanism of action includes speculation. The mechanism of action does not limit the technical scope of the present disclosure.

[0007] 1. The energy storage cell includes a case and an electrode stack. The case houses the electrode stack. The case includes a case body and a lid. The case body has an opening. The lid closes the opening. An electrode terminal is provided on the lid. The electrode stack is formed by stacking a plurality of electrode sheets. Each of the plurality of electrode sheets has a current collecting tab. A tab bundle is formed by stacking the plurality of current collecting tabs. In at least a portion of the tab bundle, the lengths of the plurality of current collecting tabs are different from one another. The tab bundle is joined to the electrode terminal. The tab bundle is stored in a curved state within the case.

[0008] In the energy storage cell described in "1" above, the length of the current collecting tabs is not constant. The different lengths of the current collecting tabs can reduce the volume of the bent tab bundle (aggregate of current collecting tabs). In other words, the space occupied by the tab bundle within the case can be reduced.

[0009] 2. The energy storage cell described in "1" above may include, for example, the following configuration: The current collecting tabs become shorter from the outer circumferential side of the curve of the tab bundle toward the inner circumferential side of the curve.

[0010] The current collecting tabs become shorter from the outer circumferential side toward the inner circumferential side of the curve, so that the tab bundle can be bent more narrowly, which is expected to reduce the space occupied by the tab bundle.

[0011] 3. The energy storage cell described in "1" above may include, for example, the following configuration: Among the multiple current collecting tabs, the current collecting tab having the longest length is disposed midway in the direction from the curved outer periphery side to the curved inner periphery side of the tab bundle.

[0012] The longer current collecting tab in the middle of the tab bundle is expected to improve heat dissipation, which is expected to reduce temperature variations inside the energy storage cell.

[0013] 4. The energy storage cell according to any one of the above items "1" to "3" may include, for example, the following configuration: Each of the current collecting tabs has a cut end surface at the tip on the electrode terminal side. When the tab bundle and the electrode terminal are released from the connection and each of the current collecting tabs is stretched in the length direction, the cut end surfaces are irregular.

[0014] 5. The energy storage cell according to any one of the above items "1" to "4" may include, for example, the following configuration: A tab bundle is formed by bundling a plurality of current collecting tabs together. Each of the plurality of current collecting tabs has a cut end surface at a tip on the electrode terminal side. When the tab bundle is joined to the electrode terminal, the plurality of cut end surfaces are aligned at the tip of the tab bundle.

[0015] Since the lengths of the current collecting tabs are different from one another, the cut end surfaces may be uneven as in the above "4." The current collecting tabs may be grouped together so that the cut end surfaces are uniform, and then the current collecting tabs (tab bundle) may be joined to the electrode terminal.

[0016] 6. The energy storage cell according to any one of the above paragraphs "1" to "5" may include, for example, the following configuration: The tab bundle includes a first tab bundle and a second tab bundle. In at least a portion of the first tab bundle, the lengths of the multiple current collecting tabs are different from one another. In at least a portion of the second tab bundle, the lengths of the multiple current collecting tabs are different from one another. The first tab bundle and the second tab bundle are each connected to the same electrode terminal. Within the case, the first tab bundle and the second tab bundle are each curved. A liquid filling port is provided in the lid. The axis of the liquid filling port passes between the first tab bundle and the second tab bundle.

[0017] The tab bundle of one electrode may be separated into two. By arranging a liquid injection port so that the electrolyte can pass between the two separated tab bundles, it is expected that the penetration of the electrolyte into the electrode laminate will be promoted.

[0018] 7. The energy storage cell according to any one of the above items "1" to "6" may include, for example, the following configuration: In plan view, each of the plurality of current collecting tabs has a protruding tip portion.

[0019] The volume of the tab bundle can be reduced by the current collecting tab having a convex tip.

[0020] 8. The energy storage cell according to any one of the above items "1" to "7" may include, for example, the following configuration: The thickness of the lid is smaller than the shortest diameter of the opening.

[0021] Because the thickness of the lid is smaller than the shortest diameter of the opening of the case body, for example, in the manufacturing method "14" below, the lid joined to the electrode stack can be inserted into the case body together with the electrode stack. By inserting the lid into the case body, even if the tab bundle is short, the tab bundle and the electrode terminal can be joined.

[0022] 9. A method for manufacturing a storage cell includes the following steps (a) to (e): (a) Prepare an electrode sheet with a current collecting tab. (b) The length of the current collecting tab is adjusted by cutting a part of the current collecting tab. (c) Stacking electrode sheets to form an electrode stack having a tab bundle. (d) The electrode stack is inserted into the case. (e) The tab bundle is joined to the electrode terminal. The tab bundle is formed by stacking current collecting tabs. The tab bundle is stored in a curved state in the case. (b) above includes cutting some of the current collecting tabs so that the lengths of the current collecting tabs in at least a part of the tab bundle are different from one another.

[0023] By cutting off a portion of the current collecting tabs before forming the electrode stack, the volume of the tab bundle can be reduced. That is, the space occupied by the tab bundle can be reduced. Furthermore, because the volume of the tab bundle is small, it may be easier to move the tab bundle to an edge inside the case, for example. By moving the tab bundle to an edge inside the case, it is expected that the space can be used more effectively. Furthermore, by moving the tab bundle to an edge, it is expected that the electrolyte can be injected without being interfered with by the tab bundle, for example.

[0024] If a part of the current collecting tab is cut off after the electrode stack is formed, cutting debris may be mixed into the electrode stack. Furthermore, the greater the number of layers in the electrode stack, the more difficult it may be to adjust the length of each current collecting tab by cutting.

[0025] 10. The method for manufacturing an energy storage cell described in "9" above may include, for example, the following configuration: (b) above includes cutting a portion of the current collecting tab so that the current collecting tab becomes shorter from the curved outer periphery side toward the curved inner periphery side of the tab bundle.

[0026] By the manufacturing method of the above "10", for example, the storage cell described in the above "2" can be manufactured.

[0027] 11. The method for manufacturing an energy storage cell described in "9" above may include, for example, the following configuration: (b) above includes cutting a portion of the current collecting tabs so that the current collecting tab having the longest length among the multiple current collecting tabs is positioned midway in the direction from the curved outer periphery side to the curved inner periphery side of the tab bundle.

[0028] By the manufacturing method of the above "11", for example, the storage cell described in the above "3" can be manufactured.

[0029] 12. The method for manufacturing a storage cell according to any one of the above items "9" to "11" may include, for example, the following configuration: A cut end surface is formed by cutting a part of a current collecting tab. The above (c) includes forming a tab bundle by bundling a plurality of current collecting tabs together in a state where the current collecting tabs are stacked so that the plurality of cut end surfaces are aligned.

[0030] By the manufacturing method of the above "12", for example, the storage cell described in the above "5" can be manufactured.

[0031] 13. The method for manufacturing a storage cell according to any one of items "9" to "12" above may include, for example, the following configuration. The case includes a cylindrical case body, a first lid, and a second lid. The case body has a first opening at one axial end and a second opening at the other axial end. The first lid is configured to close the first opening. The second lid is configured to close the second opening. A positive electrode terminal is provided on the first lid. A negative electrode terminal is provided on the second lid. The electrode stack includes a positive electrode tab bundle and a negative electrode tab bundle. In a direction perpendicular to the stacking direction of the electrode sheets, the positive electrode tab bundle and the negative electrode tab bundle each protrude outward. In the perpendicular direction, the negative electrode tab bundle protrudes in the opposite direction from the positive electrode tab bundle. The electrode stack is inserted into the case body so that the perpendicular direction is parallel to the axial direction. The positive electrode terminal is joined to the positive electrode tab bundle at a position in the axial direction where the amount of the positive electrode tab bundle protruding from the first opening is greater than the amount of the negative electrode tab bundle protruding from the second opening.

[0032] By displacing the electrode stack from the center of the case body, for example, the positive electrode tab bundle can be joined to the positive electrode terminal even if the positive electrode tab bundle is short. By shortening the positive electrode tab bundle, the space occupied by the positive electrode tab bundle can be reduced.

[0033] 14. The method for manufacturing a storage cell described in "13" above may include, for example, the following configuration: After the positive electrode tab bundle and the positive electrode terminal are joined, the electrode stack is slid in the direction opposite to the insertion direction of the electrode stack. The negative electrode terminal is joined to the negative electrode tab bundle at a position in the axial direction where the extension of the negative electrode tab bundle from the second opening is larger than the extension of the positive electrode tab bundle from the first opening.

[0034] Hereinafter, an embodiment of the present disclosure (hereinafter may be abbreviated as "the present embodiment") will be described. However, the present embodiment does not limit the technical scope of the present disclosure. The present embodiment is illustrative in all respects. The present embodiment is non-restrictive. The technical scope of the present disclosure encompasses all modifications within the meaning and scope equivalent to the claims. For example, it is also intended from the beginning that any configuration may be extracted from the present embodiment and arbitrarily combined. [Brief explanation of the drawings]

[0035] [Figure 1] FIG. 2 is a schematic diagram illustrating an example of a first storage cell in the present embodiment. [Figure 2] 3 is a schematic cross-sectional view showing an example of a first storage cell in the present embodiment. FIG. [Figure 3] 1 is a first schematic cross-sectional view showing an example of an electrode stack according to the present embodiment. [Figure 4] FIG. 2 is a second schematic cross-sectional view showing an example of an electrode stack according to the present embodiment. [Figure 5] 5A to 5C are schematic diagrams illustrating an example of a method for bundling a tab bundle in the present embodiment. [Figure 6] 10A and 10B are schematic diagrams showing an example of a method for bundling a tab bundle in a reference embodiment. [Figure 7] FIG. 1 is a first schematic plan view showing an example of an electrode sheet. [Figure 8] FIG. 2 is a second schematic plan view showing an example of an electrode sheet. [Figure 9] FIG. 3 is a schematic diagram illustrating an example of a second storage cell in the present embodiment. [Figure 10] FIG. 2 is a schematic diagram illustrating an example of an electrode stack according to the present embodiment. [Figure 11] 3 is a schematic cross-sectional view showing an example of a second storage cell in the present embodiment. FIG. [Figure 12] 3 is a schematic flowchart of a method for manufacturing a storage cell according to the present embodiment. [Figure 13] 1B is a schematic plan view showing an example of cutting of a current collecting tab in this embodiment. FIG. [Figure 14] 10 is a first schematic cross-sectional view showing an example of (d) insertion into a case and (e) joining of a tab bundle and a terminal in this embodiment. FIG. [Figure 15] 10(d) is a second schematic cross-sectional view showing an example of insertion into a case and (e) joining of a tab bundle and a terminal in this embodiment. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0036] -term- "Comprise," "include," "have," and variations thereof are open-ended terms. Open-ended terms may or may not include additional elements in addition to the required elements. "Consisting of" is a closed term. However, even a structure expressed in closed terminology may include additional elements that are normally associated with the technology or that are unrelated to the technology in question. "Consisting essentially of..." is a semi-closed term. Semi-closed terminology allows for the addition of elements that do not substantially affect the basic and novel characteristics of the technology in question.

[0037] Expressions such as "may" and "may" are used in the permissive sense, meaning "to have the possibility," rather than in the obligatory sense, meaning "to have to."

[0038] Unless otherwise specified, the order of execution of multiple steps, actions, operations, etc. included in various methods is not limited to the order described. For example, multiple steps may proceed simultaneously. For example, multiple steps may occur one after the other.

[0039] Geometric terms should not be interpreted in a strict sense. Examples of geometric terms include "parallel," "perpendicular," and the like. For example, directions, angles, distances, and the like may be displaced relative to one another as long as substantially the same or similar functions are obtained. Geometric terms may include, for example, tolerances, errors, and the like in design, work, manufacturing, and the like. The dimensional relationships in each figure may not match the actual dimensional relationships. The dimensional relationships in each figure may be changed to aid the reader's understanding. For example, length, width, thickness, and the like may be changed. Some components may be omitted.

[0040] Elements described in the singular may also include the plural unless otherwise specified. For example, a current collecting tab may refer to a plurality of current collecting tabs (or current collecting tabs).

[0041] "Planar view" refers to viewing an object from a line of sight parallel to the thickness direction of the object. The shape of the object in plan view is shown in a plan view.

[0042] "Storage cell" refers to a rechargeable battery. The storage cell may be, for example, a lithium-ion battery. The storage cell may contain, for example, a liquid electrolyte, a gel electrolyte, or a solid electrolyte.

[0043] "Electrode" is a general term for positive and negative electrodes. Similarly, for example, "electrode terminal" is a general term for positive and negative terminals. "Current collector tab" is a general term for positive and negative current collector tabs. "Tab bundle" is a general term for positive and negative tab bundles. "Tab bundle" is also a general term for first and second tab bundles.

[0044] "Curved" refers to a curved state in general. Curved includes, for example, a bent state. When an object is curved, the object may or may not include a curved surface.

[0045] -First storage cell- Fig. 1 is a schematic diagram showing an example of a first storage cell in this embodiment. Fig. 2 is a schematic cross-sectional view showing an example of a first storage cell in this embodiment. The first storage cell 1 includes a case 80 and an electrode stack 50. The case 80 includes the electrode stack 50. The case 80 includes a case main body 81 and a lid.

[0046] -Case body- The outer shape of the case body 81 may be, for example, a rectangular parallelepiped. The outer shape of the case body 81 may be, for example, a long plate. The width of the case body 81 indicates the outer dimension in the X direction. The width of the case body 81 may be, for example, 500 mm or more, 750 mm or more, or 1000 mm or more. The width of the case body 81 may be, for example, 2000 mm or less, 1500 mm or less, or 1250 mm or less. The height of the case body 81 indicates the outer dimension in the Z direction. The height of the case body 81 may be, for example, 50 mm or more, 75 mm or more, or 100 mm or more. The height of the case body 81 may be, for example, 200 mm or less, 150 mm or less, 125 mm or less, or 100 mm or less. The thickness of the case body 81 indicates the outer dimension in the Y direction. The thickness of the case body 81 may be, for example, 5 mm or more, 10 mm or more, 15 mm or more, or 20 mm or more. The thickness of the case body 81 may be 30 mm or less, 25 mm or less, 20 mm or less, 15 mm or less, or 10 mm or less. The ratio of width to height may be, for example, 5 to 20. The ratio of width to thickness may be, for example, 50 to 200.

[0047] The case body 81 has an opening. The case body 81 may have, for example, a first opening 81a and a second opening 81b. That is, the case body 81 may be cylindrical. The case body 81 may be rectangular cylindrical, for example. The first opening 81a may be located at one end in the axial direction (X direction). The second opening 81b may be located at the other end in the axial direction.

[0048] -lid- The lid closes the opening. There may be one or more lids. The number of lids corresponds to the number of openings in the case body 81. The case 80 may include, for example, a first lid 82 and a second lid 83. For example, the first lid 82 may close the first opening 81a. For example, the second lid 83 may close the second opening 81b. The lids are provided with electrode terminals. For example, a positive electrode terminal 82a may be provided on the first lid 82. For example, the positive electrode terminal 82a may be electrically isolated from the first lid 82 by an insulating member (not shown). For example, a negative electrode terminal 83a may be provided on the second lid 83. One lid may have one electrode terminal. One lid may have multiple electrode terminals. When one lid has multiple electrode terminals, the multiple electrode terminals may have the same polarity or opposite polarities. For example, a liquid injection port 84 may be provided on the lid. For example, the liquid pouring port 84 may be provided in the first lid 82.

[0049] For example, the thickness (d1) of the first lid 82 may be smaller than the shortest diameter (D1) of the first opening 81a. The thickness (d1) of the first lid 82 includes the thickness of the positive terminal 82a. The "shortest diameter" refers to the shortest inner diameter of the openings. For example, a relationship such as "d1≦0.9×D1," "d1≦0.8×D1," "d1≦0.7×D1," "d1≦0.6×D1," or "d1≦0.5×D1" may be satisfied. For example, a relationship such as "0.1D1≦d1," "0.2D1≦d1," "0.3D1≦d1," "0.4D1≦d1," or "0.5D1≦d1" may be satisfied.

[0050] For example, the thickness (d2) of the second lid 83 may be smaller than the shortest diameter (D2) of the second opening 81b. The thickness (d2) of the second lid 83 includes the thickness of the negative electrode terminal 83a. For example, the relationship "D1 = D2" may be satisfied. For example, the relationship "d1 = d2" may be satisfied.

[0051] -Electrode laminate- The electrode laminate 50 has a tab bundle. For example, the electrode laminate 50 may have a positive electrode tab bundle 51 and a negative electrode tab bundle 52. The "tab bundle" is a stack of current collector tabs. The positive electrode tab bundle 51 is formed by stacking positive electrode current collector tabs 13. The negative electrode tab bundle 52 is formed by stacking negative electrode current collector tabs 23. The positive electrode tab bundle 51 and the negative electrode tab bundle 52 are stored in a curved state inside the case 80. The positive electrode tab bundle 51 is joined to a positive electrode terminal 82a. The negative electrode tab bundle 52 is joined to a negative electrode terminal 83a.

[0052] FIG. 3 is a first schematic cross-sectional view showing an example of an electrode stack according to this embodiment. The electrode stack 50 includes multiple electrode sheets. The electrode stack 50 may include, for example, 3 to 100 electrode sheets. The electrode stack 50 is formed by alternately stacking positive electrode sheets 10 and negative electrode sheets 20. That is, the electrode stack 50 is formed by stacking multiple electrode sheets. A separator (not shown) may be disposed between the positive electrode sheets 10 and the negative electrode sheets 20. Each of the multiple positive electrode sheets 10 has a positive electrode current collector tab 13. Each of the multiple negative electrode sheets 20 has a negative electrode current collector tab 23. The positive electrode current collector tab 13 and the negative electrode current collector tab 23 may be disposed so as to protrude outward in the X direction. The X direction is perpendicular to the stacking direction (Y direction). In the X direction, the negative electrode current collector tab 23 may protrude on the opposite side from the positive electrode current collector tab 13.

[0053] At least one of the positive electrode tab bundle 51 and the negative electrode tab bundle 52 has a portion where the current collecting tabs are different in length. Either the positive electrode tab bundle 51 or the negative electrode tab bundle 52 may have a portion where the current collecting tabs are different in length. Both the positive electrode tab bundle 51 and the negative electrode tab bundle 52 may have a portion where the current collecting tabs are different in length.

[0054] For example, the lengths of the multiple positive electrode current collector tabs 13 may be different from one another in at least a portion of the positive electrode tab bundle 51. For example, all of the positive electrode current collector tabs 13 may have different lengths. For example, the lengths of the positive electrode current collector tabs 13 may gradually decrease. For example, the positive electrode current collector tabs 13 may become shorter as they move from the curved outer periphery side to the curved inner periphery side of the positive electrode tab bundle 51. The difference in length between adjacent positive electrode current collector tabs 13 may be, for example, 1 to 10 mm. In the positive electrode tab bundle 51 of FIGS. 3 and 4, the lower side of the paper surface is the curved outer periphery side, and the upper side of the paper surface is the curved inner periphery side.

[0055] For example, in at least a portion of the negative electrode tab bundle 52, the lengths of the multiple negative electrode current collector tabs 23 may be different from one another. For example, all of the negative electrode current collector tabs 23 may have different lengths. For example, the lengths of the negative electrode current collector tabs 23 may gradually decrease. For example, the negative electrode current collector tabs 23 may become shorter as they move from the curved outer periphery side toward the curved inner periphery side of the negative electrode tab bundle 52. The difference in length between adjacent negative electrode current collector tabs 23 may be, for example, 1 to 10 mm. In the negative electrode tab bundle 52 of FIGS. 3 and 4, the lower side of the paper surface is the curved inner periphery side, and the upper side of the paper surface is the curved outer periphery side.

[0056] FIG. 4 is a second schematic cross-sectional view showing an example of an electrode stack according to this embodiment. For example, some of the positive electrode current collector tabs 13 may have different lengths. For example, the positive electrode current collector tab 13 having the longest length among the multiple positive electrode current collector tabs 13 may be located at the middle of the positive electrode tab bundle 51 in the direction from the curved outer periphery to the curved inner periphery. "Middle" refers to, for example, between the outermost and innermost peripheries. The middle may also be the midpoint between the outermost and innermost peripheries. There may be one or more positive electrode current collector tabs 13 having the longest length. The difference between the maximum length and the minimum length of the positive electrode current collector tab 13 may be, for example, 1 to 10 mm.

[0057] For example, some of the negative electrode current collector tabs 23 may have different lengths. For example, the negative electrode current collector tab 23 having the longest length among the multiple negative electrode current collector tabs 23 may be arranged in the middle of the negative electrode tab bundle 52 in the direction from the curved outer periphery to the curved inner periphery. There may be one or more negative electrode current collector tabs 23 having the longest length. The difference between the maximum length and the minimum length of the negative electrode current collector tabs 23 may be, for example, 1 to 10 mm.

[0058] FIG. 5 is a schematic diagram showing an example of a method for bundling a tab bundle in this embodiment. Each of the multiple positive electrode current collector tabs 13 may have a cut end surface 13b at the tip on the positive electrode terminal 82a side. The cut end surface 13b can be formed by cutting the tip of the positive electrode current collector tab 13. In FIG. 5, the connection between the positive electrode tab bundle 51 and the positive electrode terminal 82a is released, and each of the multiple positive electrode current collector tabs 13 is stretched in the length direction. In this state, the multiple cut end surfaces 13b may be uneven. For example, the multiple cut end surfaces 13b may be uneven by cutting each individual positive electrode current collector tab 13 separately. Of the multiple cut end surfaces 13b, all of the cut end surfaces 13b may be uneven. Of the multiple cut end surfaces 13b, some of the cut end surfaces 13b may be uneven.

[0059] The positive electrode tab bundle 51 may be formed by bundling multiple positive electrode current collector tabs 13 together. Any bundling method is possible. For example, multiple positive electrode current collector tabs 13 may be bundled together by ultrasonic bonding. For example, multiple positive electrode current collector tabs 13 may be stacked together to form a laminate at the tip of the positive electrode tab bundle 51 so that multiple cut end surfaces 13b are aligned. The laminate is clamped between the ultrasonic horn 201 and the anvil 202. Multiple positive electrode current collector tabs 13 can be bundled together by applying ultrasonic waves to the laminate. In other words, the positive electrode tab bundle 51 can be formed. The bundled positive electrode tab bundle 51 may be joined to the positive electrode terminal 82a. In other words, when the positive electrode tab bundle 51 is joined to the positive electrode terminal 82a, multiple cut end surfaces 13b may be aligned at the tip of the positive electrode tab bundle 51. The negative electrode tab bundle 52 may be formed in the same manner as the positive electrode tab bundle 51. The current collecting tabs may be bound together at the same time as they are joined to the electrode terminals.

[0060] FIG. 6 is a schematic diagram showing an example of a method for bundling a tab bundle in a reference embodiment. In FIG. 6 , the connection between the positive electrode tab bundle 51 and the positive electrode terminal 82a is also released, and each of the multiple positive electrode current collector tabs 13 is stretched in the length direction. In this state, the multiple cut end surfaces 13b are aligned. This is because, conventionally, the multiple positive electrode current collector tabs 13 have the same length. Alternatively, this is because the multiple positive electrode current collector tabs 13 are cut together. Bundling multiple positive electrode current collector tabs 13 of the same length into one may increase the volume of the positive electrode tab bundle 51. For example, the positive electrode current collector tabs 13 may bend in the positive electrode tab bundle 51. This bending may increase the space occupied by the positive electrode current collector tabs 13.

[0061] 7 is a first schematic plan view showing an example of an electrode sheet. The positive electrode sheet 10 may include a positive electrode current collector 11 and a positive electrode active material layer 12. The positive electrode current collector 11 may include, for example, aluminum foil. The positive electrode active material layer 12 may be formed by applying a positive electrode active material or the like to the surface of the positive electrode current collector 11. The positive electrode active material may include, for example, lithium iron phosphate, lithium nickel composite oxide, or the like.

[0062] The planar shape of the positive electrode sheet 10 may be, for example, a long rectangular shape. The planar shape of the positive electrode sheet 10 may be, for example, a strip shape. The positive electrode sheet 10 may have, for example, a positive electrode current collector tab 13 at an end in the longitudinal direction (X direction). The positive electrode current collector tab 13 may be, for example, a thin plate-like member. For example, the thin plate-like positive electrode current collector tab 13 may be joined to the positive electrode current collector 11. The positive electrode current collector tab 13 may be, for example, a part of the positive electrode current collector 11. For example, the positive electrode current collector tab 13 may be formed by cutting a part of the positive electrode current collector 11.

[0063] In plan view, the positive electrode current collector tab 13 may have a convex tip 13a. The convex shape indicates a shape in which the dimension in the width direction (Z direction) is small at the tip. The tip 13a may be located, for example, in the center in the width direction. FIG. 8 is a second schematic plan view showing an example of an electrode sheet. The tip 13a may be located, for example, at one end in the width direction.

[0064] As shown in FIGS. 7 and 8 , the negative electrode sheet 20 may have a structure similar to that of the positive electrode sheet 10. The negative electrode sheet 20 may include a negative electrode current collector 21, a negative electrode active material layer 22, and a negative electrode current collector tab 23. The negative electrode current collector 21 may include, for example, copper foil. The negative electrode active material layer 22 may be formed by applying a negative electrode active material to the surface of the negative electrode current collector 21. The negative electrode active material may include, for example, graphite, silicon oxide, silicon, etc. The negative electrode current collector tab 23 may also have a convex tip portion 23a. The negative electrode sheet 20 may have a larger area than the positive electrode sheet 10. For example, the negative electrode active material layer 22 may have a larger area than the positive electrode active material layer 12. The area ratio of the negative electrode active material layer 22 to the positive electrode active material layer 12 may be, for example, 1.01 to 1.10.

[0065] -Second storage cell- FIG. 9 is a schematic diagram showing an example of a second energy storage cell in this embodiment. FIG. 10 is a schematic diagram showing an example of an electrode stack in this embodiment. FIG. 11 is a schematic cross-sectional view showing an example of a second energy storage cell in this embodiment. Here, differences between the second energy storage cell 2 and the first energy storage cell 1 will be mainly described. For example, the tab bundle may be separated into two. That is, the positive electrode tab bundle 51 may include a first tab bundle 51a and a second tab bundle 51b. In at least a portion of the first tab bundle 51a, the lengths of the multiple positive electrode current collector tabs 13 are different from each other. In at least a portion of the second tab bundle 51b, the lengths of the multiple positive electrode current collector tabs 13 are also different from each other. The first tab bundle 51a and the second tab bundle 51b are connected to the positive electrode terminal 82a. That is, the first tab bundle 51a and the second tab bundle 51b are each connected to the same electrode terminal. For example, the tab bundle may be separated into three or more. For example, the negative electrode tab bundle 52 may similarly include a first tab bundle 52a and a second tab bundle 52b.

[0066] Within the case 80, the first tab bundle 51a and the second tab bundle 51b are each curved. For example, as shown in Fig. 10, the first tab bundle 51a and the second tab bundle 51b may be curved in opposite directions. For example, the first tab bundle 51a and the second tab bundle 51b may be curved in the same direction.

[0067] In FIG. 11 , a liquid inlet 84 is provided in a first lid 82. An axis 84a of the liquid inlet 84 passes between the first tab bundle 51a and the second tab bundle 51b. The electrolyte can permeate the electrode stack 50 along the axis 84a. That is, the electrolyte can permeate the electrode stack 50 without being interfered with by the first tab bundle 51a and the second tab bundle 51b. For example, the first tab bundle 51a and the second tab bundle 51b may be curved in a direction away from the axis 84a of the liquid inlet 84.

[0068] The second lid 83 may also be provided with a liquid filling port 84. As with the first lid 82, the axis 84a of the liquid filling port 84 of the second lid 83 may also pass between the first tab bundle 52a and the second tab bundle 52b. For example, the liquid filling port 84 may be disposed at the center of the lid in the Z direction. For example, the positive electrode terminal 82a and the negative electrode terminal 83a may be staggered in the Z direction. For example, in the first lid 82, the positive electrode terminal 82a may be disposed below the liquid filling port 84 in the Z direction. For example, in the second lid 83, the negative electrode terminal 83a may be disposed above the liquid filling port 84 in the Z direction. For example, the electrolyte may be poured through each of the two liquid filling ports 84. For example, the electrolyte may be poured through one liquid filling port 84, and degassing may be performed through the other liquid filling port 84.

[0069] -Method of manufacturing energy storage cells- 12 is a schematic flowchart of a method for manufacturing a storage cell according to this embodiment. Hereinafter, the "method for manufacturing a storage cell according to this embodiment" may be abbreviated as "this manufacturing method." This manufacturing method includes "(a) preparing an electrode sheet," "(b) cutting off current collecting tabs," "(c) forming an electrode stack," "(d) inserting into a case," and "(e) joining the tab bundle and terminals." This manufacturing method may further include, for example, "(f) joining a lid," "(g) injecting liquid," and "(h) sealing."

[0070] -(a) Preparation of electrode sheet- This manufacturing method includes preparing electrode sheets having current collecting tabs. For example, the positive electrode sheet 10 and the negative electrode sheet 20 shown in Fig. 7 or 8 may be prepared. A plurality of the positive electrode sheets 10 and the negative electrode sheets 20 may be prepared.

[0071] -(b) Cutting the current collecting tab- FIG. 13 is a schematic plan view showing an example of cutting the current collecting tab (b) in this embodiment. This manufacturing method involves adjusting the length of the current collecting tab by cutting a portion of the current collecting tab. The length of the current collecting tab indicates the dimension in the X direction. For example, the length of the positive electrode current collecting tab 13 may be adjusted by cutting a portion of the tip portion 13a. For example, the length of the negative electrode current collecting tab 23 may be adjusted by cutting a portion of the tip portion 23a. Any cutting method may be used. For example, a cutting tool may be used. For example, the current collecting tab may be cut off in part by a laser.

[0072] -(c) Formation of electrode stack- This manufacturing method includes forming an electrode laminate 50 having a tab bundle by stacking electrode sheets. For example, as shown in FIGS. 3 and 4, the electrode laminate 50 may be formed by alternately stacking positive electrode sheets 10 and negative electrode sheets 20. The electrode laminate 50 has a positive electrode tab bundle 51 and a negative electrode tab bundle 52. For example, as shown in FIG. 5, this manufacturing method may include bundling a plurality of electrode tabs together to form a tab bundle.

[0073] In the above (b), the lengths of the current collecting tabs are adjusted in advance. For example, in at least a portion of the positive electrode tab bundle 51, some of the positive electrode current collecting tabs 13 may be cut so that the lengths of the multiple positive electrode current collecting tabs 13 differ from one another. For example, in at least a portion of the negative electrode tab bundle 52, some of the negative electrode current collecting tabs 23 may be cut so that the lengths of the multiple negative electrode current collecting tabs 23 differ from one another.

[0074] For example, as shown in Fig. 3, parts of the current collecting tabs may be cut so that they become gradually shorter in the stacking direction (Y direction). For example, as shown in Fig. 4, parts of the current collecting tabs may be cut so that the current collecting tab with the longest length among the multiple current collecting tabs is positioned midway in the stacking direction (Y direction).

[0075] -(d) Insertion into the case- FIG. 14 is a first schematic cross-sectional view showing an example of insertion into case (d) and joining of tab bundle and terminal in the present embodiment. This manufacturing method includes inserting the electrode laminate 50 into the case 80. For example, the electrode laminate 50 is inserted into the cylindrical case body 81. The direction orthogonal to the stacking direction of the electrode laminate 50 (X direction) may be parallel to the axial direction of the case body 81. The electrode laminate 50 may be inserted through the first opening 81a or through the second opening 81b.

[0076] -(e) Joining of tab bundle and terminal- This manufacturing method includes joining the tab bundle to the electrode terminal. The electrode laminate 50 may be slid, for example, to the first position. At the first position, the first protrusion p1 of the positive tab bundle 51 from the first opening 81a in the X direction is larger than the second protrusion p2 of the negative tab bundle 52 from the second opening 81b. At the first position, the positive tab bundle 51 may be joined to the positive terminal 82a. The joining method is arbitrary. For example, ultrasonic joining, laser joining, resistance welding, etc. may be performed.

[0077] FIG. 15 is a second schematic cross-sectional view showing an example of insertion into case (d) and joining of tab bundle and terminal in the present embodiment. After joining the positive tab bundle 51 and the positive terminal 82a, the electrode laminate 50 may be slid in the direction opposite to the insertion direction of the electrode laminate 50. The electrode laminate 50 may be slid, for example, to the second position. At the second position, the second protrusion p2 of the negative tab bundle 52 from the second opening 81b in the X direction is larger than the first protrusion p1 of the positive tab bundle 51 from the first opening 81a. For example, when the relationship of "d1 < D1" is satisfied, the first lid 82 can be inserted and slid into the case body 81 together with the electrode laminate 50. At the second position, the negative tab bundle 52 may be joined to the negative terminal 83a. Note that the order of joining is arbitrary. Joining may be performed from the negative side.

[0078] -(f) Joining of lid- This manufacturing method may include, for example, joining a lid to case body 81. For example, as shown in Fig. 2, the orientation of first lid 82 is adjusted so that first lid 82 fits into first opening 81a. For example, first lid 82 may be joined to case body 81 by irradiating a laser onto the fitting portion between first lid 82 and case body 81.

[0079] The positive electrode tab bundle 51 is stored in the case 80 in a curved state. For example, the positive electrode tab bundle 51 may be folded. The positive electrode tab bundle 51 may be folded in the Y direction, for example, into a U-shape. The positive electrode tab bundle 51 may be folded in the Y direction, for example, into a V-shape. In this manufacturing method, a portion of the positive electrode current collector tab 13 is cut off, so the volume of the positive electrode tab bundle 51 is small. Therefore, the positive electrode tab bundle 51 can be folded into a small size. That is, an improvement in energy density is expected.

[0080] Similarly, the negative electrode tab bundle 52 can be housed in the case. A second lid 83 can be joined to the case body 81.

[0081] -(g) Liquid injection, (h) Sealing- This manufacturing method may include, for example, injecting an electrolyte solution (not shown) into case 80. Case 80 is formed by joining first lid 82 and second lid 83 to case body 81. For example, first lid 82 may be provided with a liquid inlet 84. The electrolyte solution may be injected into case 80 through liquid inlet 84. After the electrolyte solution is injected, liquid inlet 84 may be closed with a sealing plug (not shown). [Explanation of symbols]

[0082] 1 first storage cell, 2 second storage cell, 10 positive electrode sheet, 11 positive electrode current collector, 12 positive electrode active material layer, 13 positive electrode current collector tab, 13a, 23a tip portion, 13b cut end surface, 20 negative electrode sheet, 21 negative electrode current collector, 22 negative electrode active material layer, 23 negative electrode current collector tab, 50 electrode laminate, 51 positive electrode tab bundle, 51a, 52a first tab bundle, 51b, 52b second tab bundle, 52 negative electrode tab bundle, 80 case, 81 case body, 81a first opening, 81b second opening, 82 first lid, 82a positive electrode terminal, 83 second lid, 83a negative electrode terminal, 84 injection port, 84a axis, 201 ultrasonic horn, 202 anvil, p1 first outlet, p2 second outlet.

Claims

1. a case and an electrode stack, the case accommodates the electrode stack, The case includes a case body and a lid, The case body has an opening, The lid closes the opening, The lid is provided with an electrode terminal, the electrode stack is formed by stacking a plurality of electrode sheets, Each of the plurality of electrode sheets has a current collecting tab, A plurality of the current collecting tabs are stacked to form a tab bundle, In at least a portion of the tab bundle, the lengths of the current collecting tabs are different from one another, The tab bundle is joined to the electrode terminal, and The tab bundle is stored in a curved state within the case. Energy storage cell.

2. The current collecting tabs become shorter from the curved outer periphery side to the curved inner periphery side of the tab bundle. The energy storage cell according to claim 1 .

3. the current collecting tab having the longest length among the plurality of current collecting tabs is disposed at the middle of the tab bundle in a direction from the curved outer circumferential side to the curved inner circumferential side; The energy storage cell according to claim 1 .

4. Each of the current collecting tabs has a cut end surface at a tip thereof on the electrode terminal side, and When the tab bundle and the electrode terminal are released from each other and each of the current collecting tabs is stretched in the length direction, the cut end surfaces are irregular. The energy storage cell according to any one of claims 1 to 3.

5. The plurality of current collecting tabs are bundled together to form the tab bundle, Each of the current collecting tabs has a cut end surface at a tip thereof on the electrode terminal side, and In a state where the tab bundle is joined to the electrode terminal, At the tip of the tab bundle, the plurality of cut end surfaces are aligned. The energy storage cell according to any one of claims 1 to 3.

6. the tab bundle includes a first tab bundle and a second tab bundle; In at least a portion of the first tab bundle, the lengths of the current collecting tabs are different from one another, In at least a portion of the second tab bundle, the lengths of the plurality of current collecting tabs are different from one another, each of the first tab bundle and the second tab bundle is connected to the same electrode terminal; Within the case, each of the first tab bundle and the second tab bundle is curved, The lid is provided with a liquid inlet, and an axis of the liquid inlet passing between the first tab bundle and the second tab bundle; The energy storage cell according to any one of claims 1 to 3.

7. In a plan view, each of the current collecting tabs has a convex tip portion. The energy storage cell according to any one of claims 1 to 3.

8. The thickness of the lid is smaller than the shortest diameter of the opening. The energy storage cell according to any one of claims 1 to 3.

9. (a) providing an electrode sheet having a current collecting tab; (b) adjusting the length of the current collecting tab by cutting a portion of the current collecting tab; (c) stacking the electrode sheets to form an electrode stack having a tab bundle; (d) inserting the electrode stack into a case; and (e) joining the tab bundle to an electrode terminal; Including, the tab bundle is formed by stacking the current collecting tabs, The tab bundle is accommodated in the case in a curved state, and The (b) is cutting some of the current collecting tabs so that the lengths of the plurality of current collecting tabs differ from one another in at least a portion of the tab bundle; Including, A method for manufacturing a storage cell.

10. The (b) is The current collecting tabs become shorter from the outer circumferential side of the curve of the tab bundle toward the inner circumferential side of the curve, cutting the portion of the current collecting tab; Including, The method for manufacturing the storage cell according to claim 9 .

11. The (b) is the current collecting tab having the longest length among the plurality of current collecting tabs is disposed at the middle of the tab bundle in the direction from the curved outer circumferential side to the curved inner circumferential side, cutting the portion of the current collecting tab; Including, The method for manufacturing the storage cell according to claim 9 .

12. The part of the current collecting tab is cut to form a cut end surface, and The (c) is forming the tab bundle by bundling the current collecting tabs together in a state in which the current collecting tabs are stacked so that the cut end surfaces are aligned; Including, The method for manufacturing the energy storage cell according to any one of claims 9 to 11.

13. The case includes a cylindrical case body, a first lid, and a second lid, the case body has a first opening at one end in the axial direction and a second opening at the other end in the axial direction; the first lid is configured to close the first opening, the second lid is configured to close the second opening, A positive electrode terminal is provided on the first lid, A negative electrode terminal is provided on the second lid, the electrode stack includes a positive electrode tab bundle and a negative electrode tab bundle, each of the positive electrode tab bundle and the negative electrode tab bundle protrudes outward in a direction perpendicular to the stacking direction of the electrode sheets; In the orthogonal direction, the negative electrode tab bundle protrudes in an opposite direction to the positive electrode tab bundle, The electrode stack is inserted into the case body so that the orthogonal direction is parallel to the axial direction, and the positive electrode terminal is joined to the positive electrode tab bundle at a position in the axial direction where a protrusion amount of the positive electrode tab bundle from the first opening is larger than a protrusion amount of the negative electrode tab bundle from the second opening. The method for manufacturing the energy storage cell according to any one of claims 9 to 11.

14. After the positive electrode tab bundle and the positive electrode terminal are joined, the electrode stack is slid in a direction opposite to the insertion direction of the electrode stack, and the negative electrode terminal is joined to the negative electrode tab bundle at a position in the axial direction where the protrusion margin of the negative electrode tab bundle from the second opening is larger than the protrusion margin of the positive electrode tab bundle from the first opening. The method for producing the storage cell according to claim 13 .

Images