Method for manufacturing electric power storage device, and electric power storage device

Abstract

This method for manufacturing an electric power storage device comprises: a preparation step for preparing a first electrode, a second electrode, a first tab 51, and a bottomed cylindrical case 30; a connection step for connecting the first tab 51 to the first electrode; a formation step for forming an electrode group using the second electrode and the first electrode to which the first tab 51 is connected; an accommodation step for accommodating the electrode group in the case 30; and a welding step for forming a primary light beam and a high-order light beam using a diffraction optical element, and welding the first tab 51 and the case 30 by means of the primary light beam at weld portions W. In the welding step, molten marks M are formed on both sides of the weld portions W in the case 30 by means of the high-order light beam. This makes it possible to provide an electric power storage device having exceptional welding quality.

Description

Electricity storage device manufacturing method and electricity storage device

[0001] The present disclosure relates to a method for manufacturing an electricity storage device and an electricity storage device.

[0002] Conventionally, cylindrical electricity storage devices including a wound electrode group have been known (for example, see Patent Document 1). The electricity storage device (specifically, a nonaqueous electrolyte secondary battery) in Patent Document 1 includes an electrode group having a positive electrode and a negative electrode, a cylindrical case with a bottom that houses the electrode group, and a negative electrode tab connected to the negative electrode of the electrode group and the bottom of the case, and the bottom of the case and the negative electrode tab are connected by welding.

[0003] Japanese Patent Application Laid-Open No. 2019-153388

[0004] However, high-quality welding of the case bottom and the negative electrode tab has become increasingly difficult due to the recent trend toward thinner cases. In this situation, one of the objects of the present disclosure is to provide an electricity storage device with excellent welding quality.

[0005] One aspect of the present disclosure relates to a method for manufacturing an energy storage device, the method including: a preparation step of preparing first and second electrodes, a first tab, and a bottomed cylindrical case; a connection step of connecting the first tab to the first electrode; a formation step of forming an electrode group using the first electrode connected to the first tab and the second electrode; an accommodation step of accommodating the electrode group in the case; and a welding step of shaping a primary light beam and a higher-order light beam using a diffractive optical element and welding the first tab and the case at a welded portion with the primary light beam, wherein in the welding step, the higher-order light beam forms a melting mark on both sides of the welded portion in the case.

[0006] Another aspect of the present disclosure relates to an electric storage device including an electrode group having first and second electrodes, a first tab connected to the first electrodes, and a bottomed cylindrical case that houses the electrode group and is connected to the first tab by a weld, with melting marks formed on both sides of the weld on the case.

[0007] According to the present disclosure, it is possible to provide an electricity storage device with excellent welding quality.

[0008] The novel features of the present invention are set forth in the appended claims, but the present invention, both in terms of structure and content, together with other objects and features of the present application, will be better understood from the following detailed description taken in conjunction with the drawings.

[0009] 1 is a vertical cross-sectional view schematically illustrating an example of an electric storage device according to the present disclosure, and FIG. 2 is a bottom view of the electric storage device, showing welded portions and melting marks.

[0010] Examples of embodiments of a manufacturing method for a power storage device and a power storage device according to the present disclosure will be described below. However, the present disclosure is not limited to the examples described below. While specific numerical values ​​and materials may be used in the following description, other numerical values ​​and materials may be used as long as the effects of the present disclosure are obtained.

[0011] (Method for manufacturing an electricity storage device) A method for manufacturing an electricity storage device according to the present disclosure includes a preparation step, a connection step, a formation step, a housing step, and a welding step. The electricity storage device may be a battery or a capacitor.

[0012] In the preparation step, a first electrode, a second electrode, a first tab, and a bottomed cylindrical case are prepared, one of the first electrode and the second electrode being a positive electrode and the other of the first electrode and the second electrode being a negative electrode.

[0013] The first electrode may have a long sheet-like (or strip-like) first current collector and a first active material layer formed on the surface of the first current collector. When the first electrode is the negative electrode of a lithium-ion secondary battery, the first current collector may be made of copper foil or copper alloy foil. When the first electrode is the negative electrode of a lithium-ion secondary battery, the first active material layer may include a negative electrode active material (such as a carbonaceous material or a silicon-containing material), a conductive agent, and a binder. The first active material layer may not be provided.

[0014] The second electrode may have a second current collector in the form of a long sheet (or a strip) and a second active material layer formed on the surface of the second current collector. When the second electrode is a positive electrode of a lithium-ion secondary battery, the second current collector may be made of aluminum foil or aluminum alloy foil. When the second electrode is a positive electrode of a lithium-ion secondary battery, the second active material layer may include a positive electrode active material (e.g., a lithium-containing transition metal oxide), a conductive agent, a binder, etc.

[0015] The first tab may be made of a metal (e.g., aluminum, an aluminum alloy, nickel, or a nickel alloy). The first tab may be formed in a band shape.

[0016] The case may have an opening at one end. The case may be made of, for example, a metal containing iron as a main component. The shape of the tubular portion of the case may be, for example, a cylindrical or rectangular tube.

[0017] In the connecting step, the first tab is connected to the first electrode of the electrode group. Examples of the connection method include a method of fixing the first tab to the first electrode by crimping, or a method of joining the first electrode and the first tab by ultrasonic waves. One end of the first tab may be connected to the first electrode.

[0018] In the forming step, an electrode group is formed using a first electrode and a second electrode connected by a first tab. The electrode group may be a wound type electrode group in which the first electrode and the second electrode are wound with a separator interposed therebetween. The outer shape of the electrode group may be, for example, a cylindrical or prismatic shape.

[0019] The separator may be made of a porous sheet having ion permeability and insulating properties, such as a thin film, woven fabric, or nonwoven fabric having micropores.

[0020] In the housing step, the electrode group is housed in a case. At this time, the electrode group may be housed in the case so that the end of the electrode group from which the first tab extends faces the bottom of the case.

[0021] In the welding process, a diffractive optical element is used to shape a first-order light beam and a higher-order light beam, and the first tab and the case are welded at a welded portion by the first-order light beam. The other end of the first tab may be welded to the bottom of the case. The first-order light beam and the higher-order light beam may each be a spot-shaped laser beam. In the welding process, a linear welded portion may be formed by linearly moving the case while irradiating the case with the spot-shaped first-order light beam. The number of primary light beams is not particularly limited, and may be, for example, two or more and five or less. The higher-order light beams may be shaped on both sides of the primary light beam. For example, it is conceivable to shape one or more high-order light beams on one side of three primary light beams and shape another one or more high-order light beams on the other side of the three primary light beams.

[0022] In the welding process, a melting mark is formed on both sides of the welded portion of the case by a high-order light beam. The melting mark does not have to reach the first tab. The distance between the melting mark on one side and the welded portion may be substantially equal to the distance between the melting mark on the other side and the welded portion. In this specification, "the two distances are substantially equal" means that, assuming one distance to be 100, the other distance is 95 or more and 105 or less. By forming the melting mark on both sides of the welded portion by a high-order light beam, the thermal effect between the welded portion and the melting mark can be stabilized, thereby improving the quality of the welded portion.

[0023] The manufacturing method for an energy storage device may further include an evaluation step of alternatively evaluating the state of the weld by evaluating the state of the melting mark. The state of the melting mark may include the thickness of the melting mark and the presence or absence of the melting mark. The state of the weld may include the joint strength, the presence or absence of defects, or the presence or absence of the weld. The melting mark by the higher-order light beam is formed simultaneously with the weld by the primary light beam, and both are derived from the same laser beam. Therefore, by evaluating the state of the melting mark, the state of the weld can be alternatively (or indirectly) evaluated. For example, if the melting mark is too thin, it can be evaluated that the joint strength of the weld is insufficient due to insufficient laser output.

[0024] In the evaluation step, the condition of the weld may alternatively be evaluated by comparing the condition of the fusion mark on one side of the weld with the condition of the fusion mark on the other side of the weld. For example, if the fusion mark on one side of the weld is thinner (or thicker) than the fusion mark on the other side of the weld, it can be assumed that the case was tilted during the welding process, and therefore that the weld was not properly formed.

[0025] (Electricity storage device) The electric energy storage device according to the present disclosure may be a battery or a capacitor. Examples of the battery include a primary battery such as a lithium primary battery, and a secondary battery such as an alkaline storage battery (nickel-metal hydride battery, nickel-cadmium battery, etc.), a lithium-ion secondary battery, or a lithium metal secondary battery. The electric energy storage device according to the present disclosure includes an electrode group, a first tab, and a case.

[0026] The electrode group includes a first electrode and a second electrode. The electrode group may be a wound electrode group in which the first electrode and the second electrode are wound with a separator interposed therebetween. The outer shape of the electrode group may be, for example, a cylindrical or prismatic shape.

[0027] The first tab may be made of metal (e.g., aluminum, aluminum alloy, nickel, or nickel alloy). The first tab may be formed in a band shape.

[0028] The case is a cylindrical case with a bottom that houses the electrode group and is connected to the first tab by a weld. The case may house an electrolyte in addition to the electrode group. The shape of the cylindrical part of the case may be, for example, a cylindrical or rectangular tube.

[0029] A melting mark is formed on both sides of the welded portion of the case. The melting mark does not have to reach the first tab. It is conceivable to form the welded portion with the primary light beam while forming the melting mark with the higher-order light beam, and particularly in this case, the thermal influence between the welded portion and the melting mark can be stabilized, thereby improving the quality of the welded portion.

[0030] The entire weld and fusion mark may be positioned to overlap the first tab when viewed in the axial direction of the case. In this case, the weld securely connects the case to the first tab. Furthermore, the influence of heat input when forming the fusion mark on the weld is symmetrical between both fusion marks, which stabilizes the quality of the weld.

[0031] As described above, according to the present disclosure, by forming fusion marks on both sides of the weld, it is possible to provide an energy storage device with excellent welding quality. Furthermore, according to the present disclosure, it is possible to alternatively evaluate the condition of the weld based on the condition of the fusion marks.

[0032] An example of a method for manufacturing a power storage device and a power storage device according to the present disclosure will be described in detail below with reference to the drawings. The above-described steps and components can be applied to the steps and components of the example method for manufacturing a power storage device and the example of the power storage device described below. The steps and components of the example method for manufacturing a power storage device and the example of the power storage device described below can be modified based on the above description. Furthermore, the matters described below may be applied to the above-described embodiment. Among the steps and components of the example method for manufacturing a power storage device and the example of the power storage device described below, steps and components that are not essential to the method for manufacturing a power storage device and the power storage device according to the present disclosure may be omitted. Note that the diagrams shown below are schematic and do not accurately reflect the shapes and numbers of actual components.

[0033] In the following, first, the electricity storage device 10 of this embodiment will be described, and then a method for manufacturing the electricity storage device of this embodiment will be described.

[0034] 1 and 2 , the power storage device 10 includes an electrode group 20, a case 30, and a sealing plate 40. The case 30 is a lithium-ion secondary battery.

[0035] The electrode group 20 is formed by winding a strip-shaped first electrode 21 and a strip-shaped second electrode 22 with a strip-shaped separator 23 interposed therebetween. In this embodiment, the first electrode 21 is a negative electrode and the second electrode 22 is a positive electrode, but this is not limited thereto. The first electrode 21 is exposed over the entire periphery at the outermost periphery of the electrode group 20, but this is not limited thereto. At the outermost periphery of the electrode group 20, the core of the first electrode 21 is in contact with the inner surface of the case 30.

[0036] The case 30 accommodates the electrode group 20 and a nonaqueous electrolyte (not shown). The case 30 is made of metal and is formed into a cylindrical shape with a bottom and an opening at one end (the upper end in FIG. 1 ). A first tab 51 connected to the first electrode 21 is connected to the inner bottom surface of the case 30 at a welded portion W. Thus, the case 30 of this embodiment functions as an external negative electrode terminal. A ring-shaped first insulating plate 54 is provided between the inner bottom surface of the case 30 and the electrode group 20.

[0037] Weld marks M are formed on both sides of the welded portion W on the case 30 (on both the left and right sides in FIG. 1 ). The welded portion W straddles the case 30 and the first tab 51, while the welded portion M remains within the case 30 and does not reach the first tab 51. As shown in FIG. 2 , the welded portion W and the welded portion M are arranged so that they overlap the first tab 51 (shown by the two-dot chain line in FIG. 2 ) as a whole when viewed in the axial direction of the case 30. The welded portions W are formed in three straight lines parallel to each other, and the welded portion M is formed in a straight line parallel to the outermost welded portion W near the outermost welded portion W. The distance between the left welded portion W and the left welded portion M is equal to the distance between the right welded portion W and the right welded portion M. In other words, the two welded portions M are arranged symmetrically with respect to the three welded portions W.

[0038] The sealing plate 40 seals the opening of the case 30. A gasket 53 is disposed around the periphery of the sealing plate 40, and the inside of the case 30 is sealed by crimping the open edge of the case 30 together with the gasket 53. The sealing plate 40 is electrically connected to the second electrode 22 via a second tab 52. Thus, the sealing plate 40 of this embodiment functions as an external positive electrode terminal. A ring-shaped second insulating plate 55 is provided between the sealing plate 40 and the electrode group 20.

[0039] (Method for manufacturing the energy storage device) Next, a method for manufacturing the energy storage device of this embodiment will be described. The method for manufacturing the energy storage device of this embodiment can not only manufacture the energy storage device 10 of this embodiment described above, but can also manufacture other types of energy storage devices. The method for manufacturing the energy storage device includes a preparation step, a connection step, a formation step, a housing step, a welding step, and an evaluation step.

[0040] In the preparation step, the first electrode 21, the second electrode 22, the separator 23, the first tab 51, the second tab 52, the bottomed cylindrical case 30, and the sealing plate 40 are prepared.

[0041] In the connecting step, the first tab 51 is connected to the first electrode 21 of the electrode group 20. In this embodiment, the first tab 51 is connected to the first electrode 21 by ultrasonic bonding, but the method is not limited to this. In the connecting step of this embodiment, the second tab 52 is further connected to the second electrode 22 of the electrode group 20, but the method is not limited to this. For example, a so-called end face current collecting structure may be adopted in which the second electrode 22 is connected to a current collecting plate (not shown).

[0042] In the forming process, a wound electrode group 20 is formed using a first electrode 21 connected to a first tab 51, a second electrode 22 connected to a second tab 52, and a separator 23. In the electrode group 20, the separator 23 is disposed so as to be interposed between the first electrode 21 and the second electrode 22.

[0043] In the accommodation step, the electrode group 20 is accommodated in the case 30. At this time, the first tab 51 is positioned on the inner bottom surface side of the case 30 (the lower side in FIG. 1 ), and the second tab 52 is positioned on the opposite side (the upper side in FIG. 1 ).

[0044] In the welding process, a diffractive optical element (not shown) is used to form a primary light beam and a higher-order light beam, and the primary light beam is used to weld the first tab 51 to the inner bottom surface of the case 30 at a weld W. Three linear welds W may be formed by moving the case 30 linearly while irradiating the case with three spot-like primary light beams.

[0045] In the welding process, a high-order light beam is used to form melt marks M on both sides of the welded portions W in the case 30. In this embodiment, one linear melt mark M is formed on one side of the three welded portions W, and one linear melt mark M is formed on the other side of the three welded portions W, but this is not limited to this. Also, two melt marks M are formed symmetrically for the three welded portions W.

[0046] In the evaluation process, the state of the welded portion W is alternatively evaluated by evaluating the state of the fusion mark M. In this embodiment, the quality of the welded portion W is alternatively evaluated by evaluating the thickness of the fusion mark M. Furthermore, in the evaluation process, the state of the welded portion W is alternatively evaluated by comparing the state (e.g., thickness) of the fusion mark M on one side (left side in FIG. 1 ) of the welded portion W with the state of the fusion mark M on the other side (right side in FIG. 1 ) of the welded portion W.

[0047] <<Appendix>> The above embodiments disclose the following techniques. (Technology 1) A method for manufacturing an electric storage device, comprising: a preparation step of preparing first and second electrodes, a first tab, and a bottomed cylindrical case; a connection step of connecting the first tab to the first electrode; a formation step of forming an electrode group using the first electrode connected to the first tab and the second electrode; a housing step of housing the electrode group in the case; and a welding step of shaping a primary light beam and a higher-order light beam using a diffractive optical element and welding the first tab and the case at a welded portion with the primary light beam, wherein in the welding step, the higher-order light beam forms a melting mark on both sides of the welded portion on the case. (Technology 2) The method for manufacturing an electric storage device according to Technology 1, further comprising an evaluation step of alternatively evaluating the state of the welded portion by evaluating the state of the melting mark. (Technology 3) The method for manufacturing an electric storage device according to Technology 2, wherein in the evaluation step, the state of the welded portion is alternatively evaluated by comparing the state of the melting mark on one side of the welded portion with the state of the melting mark on the other side of the welded portion. (Technology 4) An electric storage device comprising: an electrode group having first and second electrodes; a first tab connected to the first electrode; and a bottomed cylindrical case that houses the electrode group and is connected to the first tab by a welded portion, wherein melting marks are formed on both sides of the welded portion in the case. (Technology 5) The electric storage device according to Technology 4, wherein the welded portion and the melting mark are entirely arranged to overlap with the first tab when viewed in the axial direction of the case.

[0048] While the present invention has been described in terms of presently preferred embodiments, such disclosure is not to be interpreted as limiting. Various changes and modifications will no doubt become apparent to those skilled in the art to which the present invention pertains upon reading the above disclosure. It is therefore intended that the appended claims be interpreted to cover all changes and modifications that do not depart from the true spirit and scope of the invention.

[0049] The present disclosure can be used for a manufacturing method of an electricity storage device and for an electricity storage device.

[0050] 10: Power storage device 20: Electrode group 21: First electrode 22: Second electrode 23: Separator 30: Case 40: Sealing plate 51: First tab 52: Second tab 53: Gasket 54: First insulating plate 55: Second insulating plate W: Welded portion M: Melting mark

Claims

1. A method for manufacturing an energy storage device, comprising: a preparation step of preparing a first electrode, a second electrode, a first tab, and a bottomed cylindrical case; a connection step of connecting the first tab to the first electrode; a formation step of forming an electrode group using the first electrode to which the first tab is connected and the second electrode; a accommodating step of accommodating the electrode group in the case; and a welding step of shaping a primary light beam and a higher-order light beam using a diffractive optical element and welding the first tab and the case at a welded portion using the primary light beam, wherein in the welding step, a molten mark is formed on both sides of the welded portion on the case by the higher-order light beam.

2. The method for manufacturing an energy storage device according to claim 1, further comprising an evaluation step of alternatively evaluating the state of the welded portion by evaluating the state of the molten trace.

3. A method for manufacturing an energy storage device as described in claim 2, wherein in the evaluation process, the condition of the weld is alternatively evaluated by comparing the condition of the molten mark on one side of the weld with the condition of the molten mark on the other side of the weld.

4. An energy storage device comprising: an electrode group having a first electrode and a second electrode; a first tab connected to the first electrode; and a bottomed cylindrical case that houses the electrode group and is connected to the first tab by a welded portion, wherein melting marks are formed on both sides of the welded portion on the case.

5. The electricity storage device according to claim 4, wherein the welded portion and the entire fusion mark are positioned so as to overlap the first tab when viewed in the axial direction of the case.

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