Method for manufacturing energy storage device, and energy storage device

Abstract

This method for manufacturing an energy storage device comprises: a preparation step for preparing a case 11 having an opening and a sealing plate 12; a disposing step for disposing the sealing plate 12 so as to close the opening of the case 11; and a welding step for forming an annular primary light beam and an annular high-order light beam by means of an optical branching means, and welding the case 11 and the sealing plate 12 together using the primary light beam in an annular welding part W. In the welding step, at least one annular melting mark AM having a shape conforming to the annular welding part W is formed on the case 11 and / or the sealing plate 12 by the high-order light beam. Thus, it is possible to provide an energy storage device having excellent 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, a sealed type power storage device including a case and a sealing plate has been known (for example, see Patent Document 1). The power storage device (specifically, a sealed battery) in Patent Document 1 includes a case having an opening and accommodating an electrode group, and a sealing plate disposed in the opening of the case, and the fitting portion between the case and the sealing plate is welded with a laser beam, thereby sealing the inside of the case.

[0003] JP 2011-212711 A

[0004] However, in the method for manufacturing an electric storage device disclosed in Patent Document 1, the welding is performed by scanning a laser beam along the fitting portion between the case and the sealing plate. This method of scanning a laser beam may not ensure sufficient welding quality when welding curved portions, etc. In light of this situation, one of the objects of the present disclosure is to provide an electric storage device with excellent welding quality.

[0005] One aspect of the present disclosure relates to a method for manufacturing an electricity storage device, the method including: a preparation step of preparing a case and a sealing plate having an opening, a positioning step of positioning the sealing plate so as to close the opening of the case, and a welding step of shaping annular primary and higher-order light beams using a light branching unit and welding the case and the sealing plate at an annular weld with the primary light beams, wherein the higher-order light beam forms at least one annular fusion mark in the case and / or the sealing plate, the fusion mark having a shape that conforms to the annular weld.

[0006] Another aspect of the present disclosure relates to an electric storage device including a case having an opening, and a sealing plate connected to the case by an annular weld and sealing the opening, wherein the case and / or the sealing plate have at least one annular fusion mark shaped along the annular weld.

[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] 1A is a perspective view schematically illustrating an example of an electric storage device according to the present disclosure; FIG. 1B is a top view conceptually illustrating a case and a sealing plate; and FIG. 1C is a diagram conceptually illustrating four corners of an annular melting mark, where FIG. 1A shows an example of a case where the annular melting mark is normally formed, and FIG. 1C and FIG. 1C show examples of cases where the annular melting mark is not normally formed.

[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, an arrangement step, and a welding step. The electricity storage device may be a battery or a capacitor.

[0012] In the preparation step, a case having an opening and a sealing plate are prepared. The case may be made of, for example, a metal containing iron as a main component. The case may be formed in a bottomed tubular shape (for example, a bottomed rectangular tubular shape or a bottomed cylindrical shape). The sealing plate may be made of, for example, a metal containing iron as a main component. The sealing plate may have a shape corresponding to the opening of the case. The constituent materials of the case and the constituent materials of the sealing plate may be the same or different.

[0013] In the placement step, the sealing plate is placed so as to close the opening of the case. Hereinafter, the boundary formed between the edge of the opening of the case and the outer edge of the sealing plate may be referred to as the "boundary portion."

[0014] In the welding process, an annular primary light beam and a higher-order light beam are formed by a light branching means, and the primary light beams are used to weld the case and the sealing plate at an annular weld. The light branching means may be a diffractive optical element or LCOS (liquid crystal on silicon). The annular primary light beam may be irradiated onto the boundary or its vicinity, thereby forming an annular weld at the boundary. In this way, in the welding process, the case and the sealing plate are welded together using the annular primary light beam, thereby ensuring sufficiently high welding quality regardless of the shape of the annular weld. Furthermore, because the welding is performed in one go, the time required for the welding is extremely short, thereby reducing the manufacturing cost of the energy storage device.

[0015] Furthermore, in the welding step, the high-order light beam forms at least one annular fusion mark in the case and / or the sealing plate, the fusion mark having a shape that conforms to the annular weld. The heat applied in forming the annular fusion mark is transferred to the boundary to promote and stabilize the welding of the annular weld. Therefore, compared to when a high-order light beam is not present, the manufacturing cost can be further reduced by lowering the output of the primary light beam, and the annular weld can be stably formed by utilizing the heat input of the high-order light beam.

[0016] In the welding process, an annular melting mark may be formed within the heat-affected zone of the annular weld. The number of annular melting marks formed within the heat-affected zone is not particularly limited. If multiple annular melting marks are formed, at least one of them may be formed within the heat-affected zone. With this configuration, an annular melting mark is formed within the heat-affected zone, i.e., immediately adjacent to the annular weld, so that the heat input of the high-order light beam corresponding to the annular melting mark can be effectively used to promote the formation of the annular weld. Therefore, a power storage device with even better welding quality can be provided.

[0017] The manufacturing method for an energy storage device may further include a first evaluation step of alternatively evaluating the state of the annular weld by evaluating the state of the annular weld. The state of the annular weld may include the thickness of the annular weld. The state of the annular weld may include its joint strength or the presence or absence of defects. The annular weld by the higher-order light beam is formed simultaneously with the annular weld by the primary light beam, and both are derived from the same laser beam. Therefore, by evaluating the state of the annular weld, the state of the annular weld can be alternatively (or indirectly) evaluated. For example, if the annular weld is too thin, it can be evaluated that the joint strength of the annular weld is insufficient due to insufficient laser output.

[0018] In the welding step, a spot melting mark may be formed on the sealing plate using a zero-order light beam generated by the light branching means. The manufacturing method for an energy storage device may further include a second evaluation step of alternatively evaluating the state of the spot melting mark by evaluating the state of the spot melting mark. The state of the spot melting mark may include the diameter of the spot melting mark if it is circular, the shape of the spot melting mark, or the presence or absence of the spot melting mark. The spot melting mark is formed simultaneously with the annular weld, and both are caused by the same laser beam. Therefore, by evaluating the state of the spot melting mark, the state of the annular weld can be alternatively (or indirectly) evaluated. For example, if the diameter of the spot melting mark is too small, it can be determined that the joining strength of the annular weld is insufficient due to insufficient laser output.

[0019] (Power Storage Device) The power storage device according to the present disclosure may be a battery or a capacitor. Examples of the battery include primary batteries such as lithium primary batteries, and secondary batteries such as alkaline storage batteries (nickel-metal hydride batteries, nickel-cadmium batteries, etc.), lithium-ion secondary batteries, and lithium metal secondary batteries. The power storage device according to the present disclosure includes a case and a sealing plate.

[0020] The case has an opening. The case may be made of, for example, a metal containing iron as a main component. The case may be formed in a bottomed tubular shape (for example, a bottomed rectangular tubular shape or a bottomed cylindrical shape). The case may house an electrode group including a positive electrode and a negative electrode, and an electrolyte.

[0021] The electrode group may be a wound type electrode group in which a positive electrode and a negative electrode are wound with a separator interposed therebetween. The outer shape of the electrode group may be, for example, a prismatic or cylindrical shape.

[0022] The positive electrode may have a long sheet-like (or strip-like) positive electrode current collector and a positive electrode active material layer formed on the surface of the positive electrode current collector. When the power storage device is a lithium-ion secondary battery, the positive electrode current collector may be made of aluminum foil or aluminum alloy foil, and the positive electrode active material layer may include a positive electrode active material (e.g., a lithium-containing transition metal oxide), a conductive agent, a binder, etc.

[0023] The negative electrode may have a long sheet-like (or strip-like) negative electrode current collector and a negative electrode active material layer formed on the surface of the negative electrode current collector. When the power storage device is a lithium ion secondary battery, the negative electrode current collector may be made of copper foil or copper alloy foil, and the negative electrode active material layer may contain a negative electrode active material (such as a carbonaceous material or a silicon-containing material), a conductive agent, and a binder. The negative electrode active material layer may not be provided.

[0024] 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.

[0025] The sealing plate is connected to the case by an annular weld and seals the opening of the case. The sealing plate may be made of, for example, a metal whose main component is iron. The sealing plate may have a shape corresponding to the opening of the case. The material of the sealing plate may be the same as or different from the material of the case.

[0026] The case and / or the sealing plate have at least one annular fusion mark having a shape that follows the annular weld. When the annular weld and the annular fusion mark are simultaneously formed by using the light branching means, it is possible to provide an electricity storage device with high welding quality and reduce the manufacturing cost of the electricity storage device, as described above.

[0027] The annular weld mark may be formed within the heat-affected zone of the annular weld. With this configuration, the heat input corresponding to the annular weld mark can be effectively used to promote the formation of the annular weld, thereby further improving the welding quality of the energy storage device.

[0028] As described above, according to the present disclosure, by forming the annular welded portion all at once, it is possible to provide an energy storage device with excellent welding quality. Furthermore, according to the present disclosure, it is possible to reduce the manufacturing cost of the energy storage device.

[0029] 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.

[0030] 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.

[0031] 1 and 2 , the power storage device 10 includes a case 11 and a sealing plate 12. The case 11 is a lithium-ion secondary battery.

[0032] The case 11 is formed in a rectangular cylindrical shape with an opening at one end and a bottom. The case 11 accommodates an electrode group and a non-aqueous electrolyte (not shown). The case 11 is made of metal. The electrode group is a wound type electrode group in which a positive electrode and a negative electrode are wound with a separator interposed therebetween.

[0033] The sealing plate 12 is connected to the case 11 by an annular weld W and seals the opening of the case 11. The sealing plate 12 is made of metal and is formed in the shape of a square plate that fits into the opening of the case 11. The annular weld W is formed along the outer edge of the sealing plate 12. A positive electrode terminal 13 that is electrically connected to the positive electrode of the electrode group, and a negative electrode terminal 14 that is electrically connected to the negative electrode of the electrode group are each fixed to the sealing plate 12 via an insulating member.

[0034] The case 11 and the sealing plate 12 have a plurality of (four in this example) annular melt marks AM (shown by dashed lines in FIG. 2 ) that have a shape that follows the annular weld W. These annular melt marks AM are preferably formed within the heat-affected zone (not shown) of the annular weld W. The sealing plate 12 has a spot melt mark SM in its center, but the position of the spot melt mark SM is not particularly limited.

[0035] (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 be used to manufacture other types of energy storage devices. The method for manufacturing the energy storage device includes a preparation step, an arrangement step, a welding step, a first evaluation step, and a second evaluation step.

[0036] In the preparation step, the case 11 having an opening and the sealing plate 12 having a shape corresponding to the opening are prepared. In this embodiment, the case 11 is formed in the shape of a rectangular cylinder with a bottom, and the sealing plate 12 is formed in the shape of a rectangular plate.

[0037] In the placement step, the sealing plate 12 is placed so as to close the opening of the case 11. At this time, a boundary is formed between the edge of the opening of the case 11 and the outer edge of the sealing plate 12.

[0038] In the welding process, an annular first-order light beam and a higher-order light beam are formed by a light branching means (e.g., a diffractive optical element) (not shown), and the case 11 and the sealing plate 12 are welded at the annular weld W by the first-order light beam. The annular first-order light beam has a shape that follows the boundary and is irradiated onto the boundary. In addition, in the welding process, the higher-order light beam forms a plurality of (four in this example) annular fusion marks AM, each having a shape that follows the annular weld W, on the case 11 and the sealing plate 12. At this time, it is preferable that the annular fusion marks AM be formed within a heat-affected zone (not shown) of the annular weld W. Furthermore, in the welding process, a spot fusion mark SM is formed in the center of the sealing plate 12 by a zero-order light beam generated by the light branching means.

[0039] In the first evaluation step, the condition of the annular weld W is alternatively evaluated by evaluating the condition of the annular fusion mark AM. Several specific examples of this evaluation are shown with reference to FIG. 3 . FIG. 3 is a schematic diagram illustrating four corners C of one annular fusion mark AM, and in the first evaluation step, the condition of the four corners C is evaluated to alternatively evaluate the condition of the annular weld W. As shown in FIG. 3 , the corners C may be curved so as to be convex outward. Note that in the first evaluation step, instead of or in addition to this, the condition of the four straight lines connecting the four corners C may be evaluated to alternatively evaluate the condition of the annular weld W.

[0040] FIG. 3( a ) shows a case where the four corners C are formed normally, all of which are symmetrically formed with a thickness within a predetermined tolerance range. FIG. 3( b ) shows an example where the four corners C are not formed normally, in which the two corners C on the right side of the figure are formed excessively thick, and the two corners C on the left side of the figure are formed excessively thin. From the state shown in FIG. 3( b ), it can be inferred that the case 11 and the sealing plate 12 were tilted when the annular fusion mark AM was formed (specifically, the left side of FIG. 3( b ) was located farther from the beam source than the beam focus, and the right side of FIG. 3( b ) was located closer to the beam source than the beam focus). This indicates that the annular weld W formed simultaneously with the annular fusion mark AM was also not formed normally. FIG. 3( c ) shows another example where the four corners C are not formed normally, all of which are formed excessively thin. From the state shown in Figure 3(c), it can be inferred that the laser output for forming the annular fusion mark AM was insufficient, and it can be determined that the annular weld W formed at the same time as the annular fusion mark AM was also not formed normally.

[0041] In the second evaluation step, the condition of the spot melting mark SM is evaluated to alternatively evaluate the condition of the annular weld W. Several specific examples of this evaluation are shown below. First, if the diameter of the spot melting mark SM is within a predetermined tolerance, it can be determined that the annular weld W was formed properly. Next, if the diameter of the spot melting mark SM exceeds the tolerance, it can be determined that the annular weld W was not formed properly due to excessive laser power or a misaligned focus position. On the other hand, if the diameter of the spot melting mark SM is below the tolerance, it can be determined that the annular weld W was not formed properly due to insufficient laser power. Alternatively, if the shape of the spot melting mark SM is abnormal, for example, if a portion of an originally circular shape is missing, it can be determined that the annular weld W was not formed properly due to an abnormal laser profile. Finally, if the spot melting mark SM is not present, it can be determined that the annular weld W was not formed properly due to a lack of laser irradiation.

[0042] <<Appendix>> The above embodiments disclose the following techniques. (Technology 1) A method for manufacturing an electric storage device, comprising: a preparation step of preparing a case and a sealing plate having an opening; an arrangement step of arranging the sealing plate so as to close the opening of the case; and a welding step of shaping annular primary and higher-order light beams, respectively, using a light branching means, and welding the case and the sealing plate at an annular welded portion using the primary light beams, wherein in the welding step, the higher-order light beam forms at least one annular fusion mark in the case and / or the sealing plate, the annular fusion mark having a shape that conforms to the annular welded portion. (Technology 2) The method for manufacturing an electric storage device according to Technology 1, wherein in the welding step, the annular fusion mark is formed within a heat-affected zone of the annular welded portion. (Technology 3) The method for manufacturing an electric storage device according to Technology 1 or 2, further comprising a first evaluation step of alternatively evaluating the state of the annular welded portion by evaluating the state of the annular fusion mark. (Technology 4) The method for manufacturing an electricity storage device according to any one of Technologies 1 to 3, wherein the welding step further comprises a second evaluation step of forming a spot melt mark on the sealing plate by a zero-order light beam generated by the light branching means, and evaluating the state of the spot melt mark to alternatively evaluate the state of the annular weld. (Technology 5) An electricity storage device comprising: a case having an opening; and a sealing plate connected to the case by an annular weld and sealing the opening, wherein the case and / or the sealing plate have at least one annular melt mark having a shape that follows the annular weld. (Technology 6) The electricity storage device according to Technology 5, wherein the annular melt mark is formed within a heat-affected zone of the annular weld.

[0043] 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.

[0044] The present disclosure can be used for a manufacturing method of an electricity storage device and for an electricity storage device.

[0045] 10: Power storage device 11: Case 12: Sealing plate 13: Positive electrode terminal 14: Negative electrode terminal AM: Circular melting mark C: Corner SM: Spot melting mark W: Circular weld

Claims

1. A method for manufacturing an electricity storage device, comprising: a preparation step of preparing a case and a sealing plate having an opening; a positioning step of positioning the sealing plate so as to cover the opening of the case; and a welding step of shaping annular primary light beams and higher-order light beams, respectively, using a light branching means, and welding the case and the sealing plate at an annular welded portion using the primary light beams, wherein in the welding step, the higher-order light beam forms at least one annular molten mark in the case and / or the sealing plate, the molten mark having a shape that follows the annular welded portion.

2. The method for manufacturing an electric storage device according to claim 1, wherein in the welding step, the annular molten mark is formed within a heat-affected zone of the annular welded portion.

3. The method for manufacturing an energy storage device according to claim 1 or 2, further comprising a first evaluation step of alternatively evaluating the condition of the annular welded portion by evaluating the condition of the annular molten mark.

4. A method for manufacturing an energy storage device as described in claim 1 or 2, wherein the welding process further comprises a second evaluation process in which a spot melting mark is formed on the sealing plate by a zero-order light beam generated by the light branching means, and the state of the spot melting mark is evaluated to alternatively evaluate the state of the annular weld.

5. An electricity storage device comprising: a case having an opening; and a sealing plate connected to the case by an annular weld and sealing the opening, wherein the case and / or the sealing plate have at least one annular fusion mark having a shape that follows the annular weld.

6. The electric storage device according to claim 5, wherein the annular melting mark is formed within a heat-affected zone of the annular welded portion.

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