Power storage cell and method for manufacturing same

Abstract

The invention relates to a power storage cell and a method for manufacturing the same. The power storage unit includes a case and an electrode laminate. The case accommodates the electrode laminate. The housing includes a housing body and a cover. The housing main body has an opening. The cover closes the opening. The cap is provided with an electrode terminal. The electrode laminate is formed by laminating a plurality of electrode sheets. Each of the plurality of electrode tabs has a collector tab. A tab bundle is formed by stacking a plurality of collector tabs. In at least a portion of the tab bundle, the lengths of the plurality of collector tabs are different from each other. The tab bundle is joined to the electrode terminal. In the case, the tab bundle is accommodated in a bent state.

Description

Technical Field

[0001] The present disclosure relates to a power storage unit and a method for manufacturing the same. Background Art

[0002] Japanese Patent Application Laid-Open No. 2001-283824 discloses that a plurality of rectangular collecting tabs are collectively connected to one location of a terminal.

[0003] The storage unit includes, for example, a housing and a power generation element. The housing houses the power generation element. The power generation element may be, for example, a stacked type. A stacked power generation element is also called an electrode stack. The electrode stack may be formed by stacking electrode sheets. Each electrode sheet has a collector tab at its end. Therefore, at the end of the electrode stack, a tab bundle is formed by stacking the collector tabs. The greater the number of stacked electrode sheets, the larger the volume of the tab bundle may be. The tab bundle does not contribute to the battery capacity. Since the space occupied by the tab bundle in the housing increases, the energy density of the storage unit may decrease. Summary of the Invention

[0004] The purpose of the present disclosure is to reduce the space occupied by the tab bundle.

[0005] The following describes the technical structure and effects of the present disclosure. However, the mechanism of action includes assumptions and does not limit the technical scope of the present disclosure.

[0006] 1. A storage cell includes a housing and an electrode stack. The housing accommodates the electrode stack. The housing includes a housing body and a cover. The housing body has an opening. The cover blocks the opening. The cover 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 collector tab. Stacking the plurality of collector tabs forms a tab bundle. In at least a portion of the tab bundle, the plurality of collector tabs have different lengths. The tab bundle is joined to the electrode terminal. The tab bundle is stored in a bent state within the housing.

[0007] In the battery cell described in "1" above, the length of the collector tabs is not constant. By varying the length of the collector tabs, the volume of the bent tab bundle (the collection of collector tabs) can be reduced. In other words, the space occupied by the tab bundle within the housing can be reduced.

[0008] 2. The electricity storage unit described in the above “1” may include, for example, the following structure: The collector tabs become shorter from the outer circumference of the bend toward the inner circumference of the bend of the tab bundle.

[0009] By shortening the collector tabs from the outer circumference of the bend toward the inner circumference of the bend, the tab bundle can be bent smaller. In other words, it is expected that the space occupied by the tab bundle can be reduced.

[0010] 3. The electricity storage unit described in "1" above may include, for example, the following configuration: A collector tab having the longest length among a plurality of collector tabs is disposed in the middle of the tab bundle in a direction from the curved outer circumference toward the curved inner circumference.

[0011] By lengthening the central collector tab in the tab bundle, it is expected that heat dissipation will be improved, which in turn can reduce temperature variations within the storage cell.

[0012] 4. The storage battery unit described in any of "1" to "3" above may include, for example, the following configuration. Each of the plurality of current collector tabs has a cut end surface at its tip on the electrode terminal side. When the tab bundle is released from the electrode terminal and the plurality of current collector tabs are stretched in their longitudinal directions, the cut end surfaces are misaligned.

[0013] 5. The storage battery unit described in any of "1" to "4" above may include, for example, the following configuration: A plurality of current collector tabs are bundled together to form a tab bundle. Each of the plurality of current collector tabs has a cut end surface at its tip on the electrode terminal side. When the tab bundle is bonded to the electrode terminal, the cut end surfaces are aligned at the tip of the tab bundle.

[0014] Since the lengths of the collector tabs vary, the cut end faces may not align as shown in the number "4" above. The collector tabs can be bundled together so that the cut end faces align, and then the collector tabs (tab bundle) can be joined to the electrode terminal.

[0015] 6. The storage battery unit described in any of "1" to "5" above may include, for example, the following structure. 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 plurality of collector tabs are mutually different. In at least a portion of the second tab bundle, the lengths of the plurality of collector tabs are mutually different. The first tab bundle and the second tab bundle are each connected to the same electrode terminal. Within the housing, the first tab bundle and the second tab bundle are each bent. A liquid injection port is provided in the cover. The axis of the liquid injection port passes between the first tab bundle and the second tab bundle.

[0016] The tab bundle of one electrode may be split into two. By arranging the injection port so that the electrolyte can pass between the two split tab bundles, it is expected that the permeation of the electrolyte into the electrode stack will be promoted.

[0017] 7. The power storage unit described in any one of "1" to "6" above may include, for example, the following structure: Each of the plurality of current collecting tabs has a convex tip portion when viewed in plan.

[0018] Since the collecting tab has a convex tip portion, the volume of the tab bundle can be reduced.

[0019] 8. The power storage unit described in any one of "1" to "7" above may include, for example, the following structure: The thickness of the cover is smaller than the shortest diameter of the opening.

[0020] By making the thickness of the cover smaller than the shortest diameter of the opening of the case body, for example, in the manufacturing method "14" described below, the cover, coupled to the electrode stack, can be inserted into the case body along with the electrode stack. By also inserting the cover into the case body, the tab bundle can be joined to the electrode terminal even if the tab bundle is short.

[0021] 9. A method for manufacturing a power storage unit including the following (a) to (e).

[0022] (a) Prepare an electrode sheet with collector tabs.

[0023] (b) Adjust the length of the collector tab by cutting off a portion of the collector tab.

[0024] (c) The electrode sheets are stacked to form an electrode stack having a tab bundle.

[0025] (d) Inserting the electrode stack into the case.

[0026] (e) Joining the tab bundle to the electrode terminal.

[0027] The tab bundle is formed by stacking collector tabs. The tab bundle is housed in a bent state in the housing. The above (b) includes cutting a portion of the collector tabs so that the lengths of the plurality of collector tabs differ from each other in at least a portion of the tab bundle.

[0028] By pre-cutting a portion of the current collector tab before forming the electrode stack, the volume of the tab bundle can be reduced. This means that the space occupied by the tab bundle can be reduced. Furthermore, the small size of the tab bundle makes it easier to position the tab bundle closer to the end within the housing, for example. Positioning the tab bundle closer to the end within the housing can effectively utilize space. Furthermore, positioning the tab bundle closer to the end allows for easier electrolyte injection without interference with the tab bundle.

[0029] Furthermore, when a portion of the collector tab is cut after forming the electrode stack, cutting debris may be mixed into the electrode stack. Furthermore, the larger the number of electrode stacks, the more difficult it is to adjust the length of each collector tab by cutting.

[0030] 10. The method for manufacturing a storage battery cell according to item 9 may include, for example, the following configuration: (b) includes cutting a portion of the collector tab so that the collector tab becomes shorter from the outer circumference of the bend toward the inner circumference of the bend of the tab bundle.

[0031] By the manufacturing method of the above-mentioned "10", for example, the power storage unit described in the above-mentioned "2" can be manufactured.

[0032] 11. The method for manufacturing a storage battery cell described in 9 above may include, for example, the following configuration: (b) above includes cutting a portion of the collector tab so that the longest collector tab among the plurality of collector tabs is positioned midway along the bent outer periphery toward the bent inner periphery of the tab bundle.

[0033] By the manufacturing method of the above-mentioned "11", for example, the power storage unit described in the above-mentioned "3" can be manufactured.

[0034] 12. The method for manufacturing a storage battery cell as described in any of items 9 to 11 above may include, for example, the following configuration: A portion of a collector tab is cut to form a cut end surface. (c) above includes forming a tab bundle by bundling a plurality of collector tabs together, with the collector tabs stacked such that the cut end surfaces are aligned.

[0035] By the manufacturing method of the above-mentioned “12”, for example, the power storage unit described in the above-mentioned “5” can be manufactured.

[0036] 13. The method for manufacturing a storage battery cell as described in any of items 9 to 12 above may, for example, include the following structure. The housing includes a cylindrical housing body, a first cover, and a second cover. The housing body has a first opening at one axial end and a second opening at the other axial end. The first cover is configured to block the first opening. The second cover is configured to block the second opening. A positive terminal is provided on the first cover. A negative terminal is provided on the second cover. The electrode stack includes a positive tab bundle and a negative tab bundle. The positive tab bundle and the negative tab bundle each protrude outward in a direction orthogonal to the stacking direction of the electrode sheets. In the orthogonal direction, the negative tab bundle protrudes in the opposite direction to the positive tab bundle. The electrode stack is inserted into the housing body with the orthogonal direction parallel to the axial direction. The positive terminal and the positive tab bundle are joined at a position where the positive tab bundle protrudes from the first opening in the axial direction to a greater extent than the negative tab bundle protrudes from the second opening.

[0037] By locating the electrode stack at a position offset from the center of the case body, the positive tab bundle can be joined to the positive electrode terminal even if the positive tab bundle is short. By shortening the positive tab bundle, the space occupied by the positive tab bundle can be reduced.

[0038] 14. The method for manufacturing a storage battery cell described in 13 above may include, for example, the following configuration. After the positive electrode tab bundle is joined to the positive electrode terminal, the electrode stack is slid in a direction opposite to the direction in which the electrode stack is inserted. The negative electrode terminal is joined to the negative electrode tab bundle at a position where the amount of axial protrusion of the negative electrode tab bundle from the second opening is greater than the amount of axial protrusion of the positive electrode tab bundle from the first opening.

[0039] The following describes an embodiment of the present disclosure (hereinafter referred to as "this embodiment"). However, this embodiment does not limit the technical scope of the present disclosure. This embodiment is illustrative in all respects. This embodiment is non-restrictive. The technical scope of the present disclosure includes all modifications within the meaning and scope equivalent to those described in the claims. For example, it is intended from the outset that any structures can be extracted from this embodiment and combined in any manner.

[0040] The foregoing and other objects, features, aspects and advantages of the present disclosure will become more apparent from the following detailed description of the present disclosure when read in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 This is a schematic diagram showing an example of a first power storage unit in this embodiment.

[0042] Figure 2 This is a schematic cross-sectional view showing an example of a first power storage unit in this embodiment.

[0043] Figure 3 This is a first schematic cross-sectional view showing an example of the electrode stack in this embodiment.

[0044] Figure 4 This is a second schematic cross-sectional view showing an example of the electrode stack in this embodiment.

[0045] Figure 5 This is a schematic diagram showing an example of a method for bundling a tab bundle in the present embodiment.

[0046] Figure 6 This is a schematic diagram showing an example of a method for bundling tab bundles in a reference embodiment.

[0047] Figure 7 This is a first schematic plan view showing an example of an electrode sheet.

[0048] Figure 8 This is a second schematic plan view showing an example of an electrode sheet.

[0049] Figure 9 This is a schematic diagram showing an example of the second power storage unit in this embodiment.

[0050] Figure 10 This is a schematic diagram showing an example of an electrode stack in this embodiment.

[0051] Figure 11 It is a schematic cross-sectional view showing an example of the second power storage unit in this embodiment.

[0052] Figure 12 This is a schematic flowchart of the method for manufacturing the power storage unit in this embodiment.

[0053] Figure 13 (b) This is a schematic plan view showing an example of cutting of the collector tab in this embodiment.

[0054] Figure 14 This is a first schematic cross-sectional view showing an example of (d) insertion into the housing and (e) joining of the tab bundle and the terminal in this embodiment.

[0055] Figure 15 This is a second schematic cross-sectional view showing an example of (d) insertion into the housing and (e) joining of the tab bundle and the terminal in this embodiment. DETAILED DESCRIPTION

[0056] -term-

[0057] "Having", "including", "having" and their variations are open-ended terms. In addition to the essential elements, open-ended terms may or may not include additional elements. A statement such as "consisting of..." is a closed-ended term. However, even a structure expressed in a closed-ended term may include impurities that are usually incidental or additional elements that are not related to the subject technology. A statement such as "substantially consisting of..." is a semi-closed term. In a semi-closed term, it is allowed to add elements that do not substantially affect the basic and new characteristics of the subject technology.

[0058] The expressions “may” and “might” are not used in a mandatory sense, that is, “must”, but in a permissive sense, that is, “with such possibility”.

[0059] Unless otherwise specified, the order in which the steps, actions, and operations included in various methods are performed is not limited to the order in which they are described. For example, multiple steps may be performed simultaneously. For example, multiple steps may be performed one after another.

[0060] Geometric terms should not be understood in a strict sense. Examples of geometric terms include "parallel," "perpendicular," and "orthogonal." For example, directions, angles, distances, and the like may be relatively displaced within the scope of achieving substantially the same or similar functions. Geometric terms may include, for example, tolerances and errors in design, operation, and manufacturing. The dimensional relationships in the drawings may not always match the actual dimensional relationships. To aid the reader's understanding, the dimensional relationships in the drawings may sometimes be changed. For example, length, width, thickness, and the like may sometimes be changed. Part of the structure may also sometimes be omitted.

[0061] Unless otherwise specified, elements described in the singular may also include the plural. For example, a collector tab may also refer to a plurality of collector tabs (a group of collector tabs).

[0062] "Planar observation" means observing the object with a line of sight parallel to the thickness direction of the object. The shape of the object when viewed in planar view is shown in a plan view.

[0063] The term "electricity storage unit" refers to a rechargeable battery. An electricity storage unit may be, for example, a lithium-ion battery. An electricity storage unit may contain, for example, a liquid electrolyte (electrolyte solution), a gel electrolyte, or a solid electrolyte.

[0064] "Electrode" is a general term for the positive electrode and the negative electrode. Similarly, for example, "electrode terminal" is a general term for the positive electrode terminal and the negative electrode terminal. "Collector tab" is a general term for the positive collector tab and the negative collector tab. "Tab bundle" is a general term for the positive tab bundle and the negative tab bundle. "Tab bundle" is also a general term for the first tab bundle and the second tab bundle.

[0065] "Bending" refers to all states of bending. Bending includes, for example, a buckling state. When an object is bent, the object may or may not include a curved surface.

[0066] -First Power Storage Unit-

[0067] Figure 1 This is a schematic diagram showing an example of a first power storage unit in this embodiment. Figure 2 1 is a schematic cross-sectional view showing an example of a first power storage unit in this embodiment. The first power storage unit 1 includes a case 80 and an electrode stack 50. The case 80 includes the electrode stack 50. The case 80 includes a case body 81 and a cover.

[0068] - Housing body -

[0069] The outer shape of the housing body 81 can be, for example, a rectangular parallelepiped. It can also be, for example, a long plate. The width of the housing body 81 represents the outer dimension in the X direction. For example, the width of the housing body 81 can be 500 mm or greater, 750 mm or greater, or 1000 mm or greater. For example, the width of the housing body 81 can be 2000 mm or less, 1500 mm or less, or 1250 mm or less. The height of the housing body 81 represents the outer dimension in the Z direction. For example, the height of the housing body 81 can be 50 mm or greater, 75 mm or greater, or 100 mm or greater. For example, the height of the housing body 81 can be 200 mm or less, 150 mm or less, 125 mm or less, or 100 mm or less. The thickness of the housing body 81 represents the outer dimension in the Y direction. For example, the thickness of the housing body 81 can be 5 mm or greater, 10 mm or greater, 15 mm or greater, or 20 mm or greater. The thickness of the housing body 81 can 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.

[0070] The housing body 81 has an opening. For example, the housing body 81 may have a first opening 81a and a second opening 81b. That is, the housing body 81 may be cylindrical. For example, the housing body 81 may be a square cylinder. 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.

[0071] -build-

[0072] The cover blocks the opening. There can be one or more covers. The number of covers corresponds to the number of openings in the housing body 81. The housing 80 may include, for example, a first cover 82 and a second cover 83. For example, the first cover 82 may block the first opening 81a. For example, the second cover 83 may block the second opening 81b. Electrode terminals are provided on the covers. For example, a positive terminal 82a may be provided on the first cover 82. For example, the positive terminal 82a may be electrically isolated from the first cover 82 by an insulating member (not shown). For example, a negative terminal 83a may be provided on the second cover 83. One cover may have one electrode terminal. One cover may also have multiple electrode terminals. When one cover has multiple electrode terminals, the multiple electrode terminals may have the same polarity or different polarities. For example, a liquid injection port 84 may be provided on the cover. For example, a liquid injection port 84 may be provided on the first cover 82.

[0073] For example, the thickness (d1) of the first cover 82 can be smaller than the shortest diameter (D1) of the first opening 81a. The thickness (d1) of the first cover 82 includes the thickness of the positive terminal 82a. The "shortest diameter" refers to the shortest inner diameter of the opening. For example, the following relationships can be satisfied: "d1 ≤ 0.9 × D1," "d1 ≤ 0.8 × D1," "d1 ≤ 0.7 × D1," "d1 ≤ 0.6 × D1," or "d1 ≤ 0.5 × D1." For example, the following relationships can also be satisfied: "0.1 D1 ≤ d1," "0.2 D1 ≤ d1," "0.3 D1 ≤ d1," "0.4 D1 ≤ d1," or "0.5 D1 ≤ d1."

[0074] For example, the thickness (d2) of the second cover 83 can be smaller than the shortest diameter (D2) of the second opening 81b. The thickness (d2) of the second cover 83 includes the thickness of the negative electrode terminal 83a. For example, the relationship "D1 = D2" can be satisfied. For example, the relationship "d1 = d2" can also be satisfied.

[0075] -Electrode stack-

[0076] The electrode stack 50 includes a tab bundle. For example, the electrode stack 50 may include a positive tab bundle 51 and a negative tab bundle 52. A "tab bundle" is a stack of collector tabs. The positive tab bundle 51 is formed by stacking the positive collector tabs 13. The negative tab bundle 52 is formed by stacking the negative collector tabs 23. The positive tab bundle 51 and the negative tab bundle 52 are housed in a curved state within the casing 80. The positive tab bundle 51 is bonded to the positive terminal 82a. The negative tab bundle 52 is bonded to the negative terminal 83a.

[0077] Figure 3 This is a first schematic cross-sectional view showing an example of an electrode stack in this embodiment. The electrode stack 50 includes a plurality of 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. In other words, the electrode stack 50 is formed by stacking a plurality of electrode sheets. A separator (not shown) may also be arranged between the positive electrode sheets 10 and the negative electrode sheets 20. Each of the plurality of positive electrode sheets 10 has a positive electrode collector tab 13. Each of the plurality of negative electrode sheets 20 has a negative electrode collector tab 23. In the X direction, the positive electrode collector tab 13 and the negative electrode collector tab 23 can be arranged to protrude outward. The X direction is a direction perpendicular to the stacking direction (Y direction). In the X direction, the negative electrode collector tab 23 can protrude to the side opposite to the positive electrode collector tab 13.

[0078] At least one of the positive tab bundle 51 and the negative tab bundle 52 has a portion where the collecting tab lengths differ. The portion where the collecting tab lengths differ may exist in either the positive tab bundle 51 or the negative tab bundle 52. The portion where the collecting tab lengths differ may also exist in both the positive tab bundle 51 and the negative tab bundle 52.

[0079] For example, the lengths of the plurality of positive collector tabs 13 may be different from each other in at least a portion of the positive tab bundle 51. For example, the lengths of all the positive collector tabs 13 may be different from each other. For example, the lengths of the positive collector tabs 13 may gradually become shorter. For example, the positive collector tabs 13 may become shorter as they move from the curved outer circumference of the positive tab bundle 51 toward the curved inner circumference. The length difference between adjacent positive collector tabs 13 may be, for example, 1 to 10 mm. Figure 3 and Figure 4 The positive electrode tab bundle 51 has a lower side on the paper as the curved outer peripheral side, and an upper side on the paper as the curved inner peripheral side.

[0080] For example, the lengths of the plurality of negative electrode collector tabs 23 may be different from each other in at least a portion of the negative electrode tab bundle 52. For example, the lengths of all the negative electrode collector tabs 23 may be different from each other. For example, the lengths of the negative electrode collector tabs 23 may gradually become shorter. For example, the negative electrode collector tabs 23 may become shorter as they move from the curved outer peripheral side of the negative electrode tab bundle 52 toward the curved inner peripheral side. The difference in length between adjacent negative electrode collector tabs 23 may be, for example, 1 to 10 mm. Figure 3 and Figure 4 The negative electrode tab bundle 52 has a lower side on the paper as the inner peripheral side of the bend and an upper side on the paper as the outer peripheral side of the bend.

[0081] Figure 4 This is a second schematic cross-sectional view showing an example of an electrode stack in this embodiment. For example, the lengths of some of the positive electrode collector tabs 13 may differ from one another. For example, the positive electrode collector tab 13 having the longest length among a plurality of positive electrode collector tabs 13 may be arranged in the middle of the positive electrode tab bundle 51 in the direction from the curved outer periphery toward the curved inner periphery. "Middle" means, for example, between the outermost and innermost peripheries. The middle can be the midpoint between the outermost and innermost peripheries. There can be one or more positive electrode collector tabs 13 having the longest length. The difference between the maximum and minimum lengths of the positive electrode collector tabs 13 can be, for example, 1 to 10 mm.

[0082] For example, some of the negative electrode current collector tabs 23 may have different lengths. For example, the negative electrode current collector tab 23 with the longest length among the plurality of 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 circumference toward the curved inner circumference. The number of negative electrode current collector tabs 23 with the longest length may be one or more. The difference between the maximum and minimum lengths of the negative electrode current collector tabs 23 may be, for example, 1 to 10 mm.

[0083] Figure 5 1 is a schematic diagram showing an example of a method for bundling the tab bundle in this embodiment. Each of the plurality of positive electrode collector tabs 13 may have a cut end surface 13b at the top end on the positive electrode terminal 82a side. The cut end surface 13b may be formed by cutting the top end of the positive electrode collector tab 13. Figure 5 In this state, the positive electrode tab bundle 51 is disconnected from the positive electrode terminal 82a, and the plurality of positive electrode current collector tabs 13 are each stretched in the longitudinal direction. In this state, the plurality of cut end faces 13b may be misaligned. For example, by cutting each positive electrode current collector tab 13 separately, the plurality of cut end faces 13b may be misaligned. This misalignment may occur for all or only for a portion of the plurality of cut end faces 13b.

[0084] The positive electrode tab bundle 51 can be formed by bundling multiple positive electrode collector tabs 13 into one. The bundling method is arbitrary. For example, multiple positive electrode collector tabs 13 can be bundled by ultrasonic bonding. For example, a stack can be formed by stacking multiple positive electrode collector tabs 13 at the top of the positive electrode tab bundle 51 in a manner such that multiple cut end faces 13b are aligned. The stack is clamped between the ultrasonic horn 201 and the anvil 202. By applying ultrasonic waves to the stack, multiple positive electrode collector tabs 13 can be bundled into one. That is, the positive electrode tab bundle 51 can be formed. The bundled positive electrode tab bundle 51 can be bonded to the positive terminal 82a. That is, the multiple cut end faces 13b can be aligned at the top of the positive electrode tab bundle 51 when the positive electrode tab bundle 51 is bonded to the positive terminal 82a. The negative electrode tab bundle 52 can also be formed in the same manner as the positive electrode tab bundle 51. Alternatively, a plurality of current collector tabs may be bundled into one while being bonded to the electrode terminal.

[0085] Figure 6 This is a schematic diagram showing an example of a method for bundling tab bundles in a reference manner. Figure 6In the process, the connection between the positive electrode tab bundle 51 and the positive terminal 82a is also released, and the multiple positive electrode collector tabs 13 are each stretched in the length direction. In this state, the multiple cut end faces 13b are aligned. This is because the multiple positive electrode collector tabs 13 used to have the same length. Or, it is because the multiple positive electrode collector tabs 13 are aggregated and cut. By bundling multiple positive electrode collector tabs 13 with aligned lengths into one, the volume of the positive electrode tab bundle 51 may be increased. For example, in the positive electrode tab bundle 51, the positive electrode collector tab 13 may sometimes bend. Due to the occurrence of deflection, the space occupied by the positive electrode collector tab 13 may also increase.

[0086] Figure 7 This 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 coating the surface of the positive electrode current collector 11 with, for example, a positive electrode active material. The positive electrode active material may include, for example, lithium iron phosphate or lithium nickel composite oxide.

[0087] The planar shape of the positive electrode sheet 10 can be, for example, a long rectangular strip. The planar shape of the positive electrode sheet 10 can be, for example, a strip. The positive electrode sheet 10 can have a positive electrode collector tab 13 at an end in the longitudinal direction (X direction). The positive electrode collector tab 13 can be, for example, a thin sheet-like member. For example, the thin sheet-like positive electrode collector tab 13 can be joined to the positive electrode current collector 11. The positive electrode collector tab 13 can be, for example, a portion of the positive electrode current collector 11. For example, the positive electrode collector tab 13 can be formed by cutting a portion of the positive electrode current collector 11.

[0088] The positive electrode current collector tab 13 may have a convex tip portion 13a when viewed in plan. The convex shape means that the widthwise (Z-direction) dimension is smaller at the tip. The tip portion 13a may be located, for example, at the center in the widthwise direction. Figure 8 2 is a schematic plan view showing an example of an electrode sheet. The tip portion 13a can be arranged at one end in the width direction, for example.

[0089] like Figure 7 and Figure 8As shown, the negative electrode sheet 20 can have the same structure as the positive electrode sheet 10. The negative electrode sheet 20 can include a negative electrode collector 21, a negative electrode active material layer 22, and a negative electrode collector tab 23. The negative electrode collector 21 can include, for example, copper foil. The negative electrode active material layer 22 can be formed by coating a negative electrode active material on the surface of the negative electrode collector 21. The negative electrode active material can include, for example, graphite, silicon oxide, silicon, etc. The negative electrode collector tab 23 can also have a convex top portion 23a. The negative electrode sheet 20 can have a larger area than the positive electrode sheet 10. For example, the negative electrode active material layer 22 can 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 can be, for example, 1.01 to 1.10.

[0090] -Second Power Storage Unit-

[0091] Figure 9 This is a schematic diagram showing an example of the second power storage unit in this embodiment. Figure 10 This is a schematic diagram showing an example of an electrode stack in this embodiment. Figure 11 This is a schematic cross-sectional view showing an example of a second storage cell in this embodiment. Here, the differences between the second storage cell 2 and the first storage cell 1 are mainly described. For example, the tab bundle can be separated into two. That is, the positive tab bundle 51 can 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 collector tabs 13 differ from each other. In at least a portion of the second tab bundle 51b, the lengths of the multiple positive collector tabs 13 also differ from each other. The first tab bundle 51a and the second tab bundle 51b are connected to the positive 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 can be separated into three or more. For example, the negative tab bundle 52 can similarly include a first tab bundle 52a and a second tab bundle 52b.

[0092] In the housing 80, the first tab bundle 51a and the second tab bundle 51b are bent. Figure 10 As shown, the first tab bundle 51a and the second tab bundle 51b may be bent in opposite directions. For example, the first tab bundle 51a and the second tab bundle 51b may be bent in the same direction.

[0093] exist Figure 11In the embodiment, a liquid injection port 84 is provided on the first cover 82. The axis 84a of the liquid injection port 84 passes between the first and second tab bundles 51a, 51b. The electrolyte can penetrate into the electrode stack 50 along the axis 84a. In other words, the electrolyte can penetrate into the electrode stack 50 without interfering with the first and second tab bundles 51a, 51b. For example, the first and second tab bundles 51a, 51b can be curved in a direction away from the axis 84a of the liquid injection port 84.

[0094] The second cover 83 may also be provided with a liquid injection port 84. Similar to the first cover 82, the axis 84a of the liquid injection port 84 of the second cover 83 may also pass between the first tab bundle 52a and the second tab bundle 52b. For example, the liquid injection port 84 may be arranged in the center of the cover in the Z direction. For example, in the Z direction, the positive terminal 82a and the negative terminal 83a may be different from each other. For example, in the first cover 82, the positive terminal 82a may be arranged below the liquid injection port 84 in the Z direction. For example, in the second cover 83, the negative terminal 83a may be arranged above the liquid injection port 84 in the Z direction. For example, the electrolyte may be injected from each of the two liquid injection ports 84. For example, the electrolyte may be injected from the liquid injection port 84 on one side and degassed from the liquid injection port 84 on the other side.

[0095] -Method for manufacturing power storage unit-

[0096] Figure 12 This is a schematic flow chart of the method for manufacturing a storage cell in this embodiment. Hereinafter, the "method for manufacturing a storage cell in this embodiment" may be referred to simply as the "present method." This method includes "(a) preparing an electrode sheet," "(b) cutting a collector tab," "(c) forming an electrode stack," "(d) inserting the electrode into a housing," and "(e) joining the tab bundle to the terminal." For example, this method may further include "(f) joining a lid," "(g) injecting liquid," and "(h) sealing."

[0097] - (a) Preparation of electrode sheets -

[0098] The method includes preparing an electrode sheet having a collector ear. For example, Figure 7 or Figure 8 The positive electrode sheet 10 and the negative electrode sheet 20 are shown. A plurality of positive electrode sheets 10 and negative electrode sheets 20 may be prepared.

[0099] - (b) Cutting off the collector ear -

[0100] Figure 13This is a schematic plan view showing an example of cutting the collector tab (b) in this embodiment. This manufacturing method includes adjusting the length of the collector tab by cutting a portion of the collector tab. The length of the collector tab represents the dimension in the X direction. For example, the length of the positive electrode collector tab 13 can be adjusted by cutting a portion of the top portion 13a. For example, the length of the negative electrode collector tab 23 can be adjusted by cutting a portion of the top portion 23a. The cutting method is arbitrary. For example, a cutting tool can be used. For example, a portion of the collector tab can also be cut using a laser.

[0101] -(c) Formation of Electrode Stack-

[0102] The present method includes forming an electrode stack 50 having a tab bundle by stacking electrode sheets. Figure 3 and Figure 4 As shown in FIG. 1 , the electrode stack 50 can be formed by alternately stacking the positive electrode sheets 10 and the negative electrode sheets 20. The electrode stack 50 includes a positive electrode tab bundle 51 and a negative electrode tab bundle 52. For example, Figure 5 As shown, the method may include forming a tab bundle by bundling a plurality of electrode tabs into one.

[0103] In the above step (b), the length of the collector tab is pre-adjusted. For example, in at least a portion of the positive tab bundle 51, a portion of the positive collector tabs 13 may be cut so that the lengths of the plurality of positive collector tabs 13 differ from one another. For example, in at least a portion of the negative tab bundle 52, a portion of the negative collector tabs 23 may be cut so that the lengths of the plurality of negative collector tabs 23 differ from one another.

[0104] For example, Figure 3 As shown in FIG, a portion of the collector tab may be cut off in such a manner that the collector tab gradually becomes shorter in the stacking direction (Y direction). Figure 4 As shown, a portion of the collector tab may be cut so that the collector tab having the longest length among the plurality of collector tabs is arranged in the middle in the stacking direction (Y direction).

[0105] - (d) Insertion into the housing -

[0106] Figure 14 This is a first schematic cross-sectional view illustrating an example of (d) insertion into the case and (e) joining of the tab bundle to the terminal in this embodiment. This manufacturing method includes inserting the electrode stack 50 into the case 80. For example, the electrode stack 50 is inserted into the cylindrical case body 81. The direction (X direction) perpendicular to the stacking direction of the electrode stack 50 can be parallel to the axial direction of the case body 81. The electrode stack 50 can be inserted through either the first opening 81a or the second opening 81b.

[0107] -(e) Joining of tab bundle and terminal-

[0108] This method includes joining the tab bundle to the electrode terminal. The electrode stack 50 can be slid, for example, to a first position. In this first position, a first protrusion p1 of the positive electrode tab bundle 51 from the first opening 81a in the X direction is greater than a second protrusion p2 of the negative electrode tab bundle 52 from the second opening 81b. In this first position, the positive electrode tab bundle 51 can be joined to the positive terminal 82a. Any joining method is available. For example, ultrasonic joining, laser joining, resistance welding, etc. can be employed.

[0109] Figure 15 This is a second schematic cross-sectional view illustrating an example of (d) insertion into the case and (e) joining of the tab bundle to the terminal in this embodiment. After the positive tab bundle 51 is joined to the positive terminal 82a, the electrode stack 50 can be slid in a direction opposite to the insertion direction of the electrode stack 50. For example, the electrode stack 50 can be slid to a second position. In the second position, the second protrusion p2 of the negative tab bundle 52 from the second opening 81b in the X direction is greater than the first protrusion p1 of the positive tab bundle 51 from the first opening 81a. For example, when the relationship "d1 < D1" is satisfied, the first cover 82 is inserted into the case body 81 together with the electrode stack 50 and can slide. In the second position, the negative tab bundle 52 can be joined to the negative terminal 83a. The order of joining is arbitrary. Joining can also be performed from the negative electrode side.

[0110] -(f) Engagement of cover-

[0111] The method may include, for example, joining the cover to the housing body 81. For example, Figure 2 As shown, the posture of the first cover 82 is adjusted so that the first cover 82 fits into the first opening 81a. For example, the first cover 82 and the case body 81 can be joined by irradiating the fitting portion thereof with laser.

[0112] The positive electrode tab bundle 51 is housed in the housing 80 in a bent state. For example, the positive electrode tab bundle 51 can be bent. The positive electrode tab bundle 51 can be bent in the Y direction, for example, into a U-shape. The positive electrode tab bundle 51 can also be bent in the Y direction, for example, into a V-shape. In this manufacturing method, a portion of the positive electrode collector tab 13 is cut off, resulting in a smaller volume of the positive electrode tab bundle 51. Therefore, the positive electrode tab bundle 51 can be folded smaller. In other words, an improvement in energy density can be expected.

[0113] Similarly, the negative electrode tab bundle 52 can be housed in the case. The second cover 83 can be joined to the case body 81 .

[0114] - (g) Liquid injection, (h) Sealing -

[0115] This manufacturing method may include, for example, injecting an electrolyte (not shown) into the housing 80. The first cover 82 and the second cover 83 are joined to the housing body 81 to form the housing 80. For example, a liquid injection port 84 may be provided in the first cover 82. The electrolyte can be injected into the housing 80 through the liquid injection port 84. After the electrolyte is injected, the liquid injection port 84 can be sealed with a sealing plug (not shown).

Claims

1. A power storage unit, wherein: The power storage unit includes a housing and an electrode stack. The housing accommodates the electrode stack. The housing comprises a housing body and a cover. The housing body has an opening. The cover blocks the opening, The cover 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 collector ear. A plurality of collector tabs are stacked to form a tab bundle. In at least a portion of the tab bundle, the lengths of the plurality of collector tabs are different from each other. The tab bundle is joined to the electrode terminal, and is housed in the housing in a bent state.

2. The power storage unit according to claim 1, wherein The collecting tabs become shorter from the curved outer peripheral side toward the curved inner peripheral side of the tab bundle.

3. The power storage unit according to claim 1, wherein The collector tab having the longest length among the plurality of collector tabs is arranged in the middle of the tab bundle in a direction from the curved outer peripheral side toward the curved inner peripheral side.

4. The power storage unit according to any one of claims 1 to 3, wherein Each of the plurality of collector tabs has a cut end surface at the tip end on the electrode terminal side, and when the tab bundle is released from the electrode terminal and the plurality of collector tabs are stretched in the longitudinal direction, the plurality of cut end surfaces are misaligned.

5. The power storage unit according to any one of claims 1 to 3, wherein The collector tab bundle is formed by bundling a plurality of the collector tabs into one. Each of the plurality of collecting tabs has a cut end surface at a tip end on the electrode terminal side, and the plurality of cut end surfaces are aligned at the tip end of the tab bundle when the tab bundle is joined to the electrode terminal.

6. The power storage unit according to any one of claims 1 to 3, wherein: 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 plurality of collector tabs are different from each other. In at least a portion of the second tab bundle, the lengths of the plurality of collector tabs are different from each other. The first tab bundle and the second tab bundle are each connected to the same electrode terminal. In the housing, the first tab bundle and the second tab bundle are bent respectively. The cover is provided with a liquid injection port, and an axis of the liquid injection port passes between the first electrode tab bundle and the second electrode tab bundle.

7. The power storage unit according to any one of claims 1 to 3, wherein: Each of the plurality of current collecting tabs has a convex tip portion when viewed in plan.

8. The power storage unit according to any one of claims 1 to 3, wherein The thickness of the cover is smaller than the shortest diameter of the opening.

9. A method for manufacturing a power storage unit, wherein: The method for manufacturing the power storage unit includes the following steps (a) to (e): (a) Preparing an electrode sheet with a collector tab; (b) adjusting the length of the collector tab by cutting off a portion of the collector tab; (c) forming an electrode stack having a tab bundle by stacking the electrode sheets; (d) inserting the electrode stack into a casing; and (e) joining the tab bundle to the electrode terminal, The tab bundle is formed by stacking the collector tabs. The tab bundle is housed in the housing in a bent state, and the step (b) includes cutting a portion of the collector tabs so that the lengths of the plurality of collector tabs differ from each other in at least a portion of the tab bundle.

10. The method for manufacturing a power storage unit according to claim 9, wherein: The step (b) includes cutting the portion of the collector tab so that the collector tab becomes shorter from the curved outer peripheral side toward the curved inner peripheral side of the tab bundle.

11. The method for manufacturing a power storage unit according to claim 9, wherein: The step (b) includes cutting the portion of the collecting tab so that the collecting tab having the longest length among the plurality of collecting tabs is arranged in the middle of the tab bundle in a direction from the curved outer peripheral side toward the curved inner peripheral side.

12. The method for manufacturing a power storage unit according to any one of claims 9 to 11, wherein: The portion of the collector tab is cut to form a cut end surface, and the (c) includes bundling a plurality of collector tabs into one bundle in a state where the collector tabs are stacked such that the plurality of cut end surfaces are aligned, thereby forming the tab bundle.

13. The method for manufacturing a power storage unit according to any one of claims 9 to 11, wherein: The housing includes a cylindrical housing body, a first cover, and a second cover. The housing 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 cover is configured to block the first opening. The second cover is configured to block the second opening. The first cover is provided with a positive terminal, The second cover is provided with a negative terminal, 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 orthogonal direction, the negative electrode tab bundle protrudes in the opposite direction of the positive electrode tab bundle, The electrode stack is inserted into the case body in such a manner that the orthogonal direction is parallel to the axial direction, and The positive electrode terminal and the positive electrode tab bundle are joined at a position in the axial direction where the amount by which the positive electrode tab bundle protrudes from the first opening is greater than the amount by which the negative electrode tab bundle protrudes from the second opening.

14. The method for manufacturing a power storage unit according to claim 13, wherein: After the positive electrode tab bundle is joined to the positive electrode terminal, 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 amount of protrusion of the negative electrode tab bundle from the second opening is greater than the amount of protrusion of the positive electrode tab bundle from the first opening.

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