JP7699574B2 - Method for manufacturing an electricity storage device and an electricity storage device - Google Patents

Description

This disclosure relates to a method for manufacturing an electricity storage device and an electricity storage device.

In recent years, power storage devices such as lithium ion secondary batteries have been suitably used as portable power sources for personal computers, mobile terminals, and the like, and as power sources for driving vehicles such as electric vehicles (BEVs), hybrid vehicles (HEVs), and plug-in hybrid vehicles (PHEVs). Conventionally, a power storage device has been known that has an exterior body having a rectangular bottom, an opening facing the bottom, a pair of long side walls extending from the long side of the bottom and facing each other, and a pair of short side walls extending from the short side of the bottom and facing each other, and a sealing plate that seals the opening, and has a melted and solidified portion at the fitting portion between the exterior body and the sealing plate. For example, Patent Document 1 discloses a laser welding method that includes a first laser irradiation step of irradiating a laser beam to the boundary between the battery case and the lid member when laser welding a battery case (exterior body) and a lid member (sealing plate) with a laser, and a second laser irradiation step of irradiating the battery case and the lid member with a laser beam on the front side in the direction of travel of the laser welding, compared to the irradiation position of the laser beam in the first laser irradiation step.

JP 2016-2562 A

However, in conventional electricity storage devices, the molten solidified portion protrudes outward from the short side wall, causing fluctuations in the dimensions of the electricity storage device. As electricity storage devices become more widespread, stable dimensional accuracy is required, as well as stable welding quality and high reliability, including high energy. Therefore, the inventor believes that it is desirable to suppress the molten solidified portion of the electricity storage device from protruding outward from the short side wall.

The technology disclosed here has been developed in light of the above circumstances, and its purpose is to provide a manufacturing method for an electricity storage device and an electricity storage device that have reliable dimensional accuracy by suppressing the molten solidified portion from protruding outward from the short side wall.

The technology disclosed herein is a method for manufacturing an electric storage device comprising: an electrode body having an electrode; a rectangular bottom; a pair of short side walls extending from a short side of the bottom and facing each other; a pair of long side walls extending from a long side of the bottom and facing each other; an opening facing the bottom; a pair of opening long side portions corresponding to the ends of the long side walls and a pair of opening short side portions corresponding to the ends of the short side walls, among the periphery of the opening; an outer casing that houses the electrode body; a substantially rectangular sealing plate that has a pair of sealing plate long side portions and a pair of sealing plate short side portions and seals the opening of the outer casing; and a terminal that is attached to the sealing plate and is electrically connected to the electrode body, the method comprising: a sealing plate fitting process for housing the electrode body in the outer casing and fitting the sealing plate into the opening of the outer casing; and a laser welding process for laser welding the sealing plate and the outer casing by scanning laser light L around the entire circumference of the sealing plate and the opening. Here, in the laser welding process, the laser light L is a multi-point laser light including a first laser light L1 consisting of at least one beam that irradiates the sealing plate long side portion and the sealing plate short side portion, and a second laser light L2 consisting of at least one beam that irradiates the opening long side portion and the opening short side portion. When the region consisting of the opening long side portion and the sealing plate long side portion is defined as the long side region, and the region consisting of the opening short side portion and the sealing plate short side portion is defined as the short side region, the energy of the laser light L irradiating the short side region is smaller than the energy of the laser light L irradiating the long side region, and the energy of the second laser light L2 irradiating the short side region is smaller than the energy of the first laser light L1 irradiating the short side region.

With this configuration, when the molten solidified portion is formed by the laser light L, the molten portion in the short side region is smaller than the molten portion in the long side region, and the molten portion in the short side region of the opening is smaller than the molten portion in the sealing plate short side region. This suppresses melting of the opening short side portion (short side wall) in the short side region compared to the sealing plate short side portion, and prevents the molten solidified portion from being formed outside the short side wall of the exterior body. Therefore, it is possible to manufacture an electricity storage device with reliable dimensional accuracy.

FIG. 1 is a perspective view that illustrates a power storage device according to an embodiment. FIG. 2 is a schematic vertical cross-sectional view taken along line II-II in FIG. FIG. 3 is a plan view that illustrates a schematic view of an exterior body and a sealing plate. FIG. 4 is a flow diagram showing a method for manufacturing an electricity storage device according to one embodiment. FIG. 5 is a plan view showing a schematic diagram of a long side region irradiated laser light according to an embodiment. FIG. 6 is a plan view showing a schematic diagram of a laser beam irradiated onto a short side region according to an embodiment. FIG. 7 is a plan view that illustrates a state in which a long side region irradiation laser is irradiated onto the long side region according to an embodiment. FIG. 8 is a plan view that illustrates a state in which a long side region irradiation laser is irradiated onto the long side region according to an embodiment. FIG. 9 is a plan view that illustrates a state in which a short side area irradiation laser is irradiated onto a short side area according to an embodiment. FIG. 10 is a plan view that illustrates a state in which a short side area irradiation laser is irradiated onto a short side area according to an embodiment. FIG. 11 is a vertical cross-sectional view that illustrates a state in which a long side region irradiation laser is irradiated onto the long side region according to an embodiment. FIG. 12 is a vertical cross-sectional view that illustrates a state in which a short side area irradiation laser is irradiated onto a short side area according to an embodiment. FIG. 13 is a vertical cross-sectional view illustrating the formation of a molten solidified portion in a short side region according to one embodiment. FIG. 14 is a schematic diagram showing a laser welding device used in a laser welding process according to an embodiment. FIG. 15 is a schematic diagram showing a diffractive optical element according to an embodiment. FIG. 16 is a schematic diagram showing the configuration of a diffractive optical element portion and movement of a diffractive region according to an embodiment. FIG. 17 is a plan view that illustrates a pattern of a laser beam irradiated onto a short side region according to a modified example. FIG. 18 is a vertical cross-sectional view showing a schematic view of a state in which a short side region irradiation laser light according to a modified example is irradiated. FIG. 19 is a vertical cross-sectional view showing the vicinity of the molten solidified portion according to a conventional example.

Below, the embodiments of the technology disclosed herein are described with reference to the drawings. Matters not mentioned in this specification but necessary for implementing the technology disclosed herein can be understood as design matters for a person skilled in the art based on the conventional technology in the field. The technology disclosed herein can be implemented based on the contents disclosed in this specification and the technical common sense in the field. In the following drawings, the same reference numerals are used to describe members and parts that perform the same function. The dimensional relationships (length, width, thickness, etc.) in each figure do not reflect the actual dimensional relationships. In this specification, the numerical range expressed as "A to B" includes A and B, and also includes the meanings of "preferably larger than A" and "preferably smaller than B."

In this specification, the term "energy storage device" refers to a device that can be charged and discharged. Energy storage devices include batteries generally referred to as lithium ion batteries and lithium secondary batteries, as well as lithium polymer batteries and lithium ion capacitors. A secondary battery generally refers to a battery that can be repeatedly charged and discharged by the movement of charge carriers between the positive and negative electrodes. Here, a lithium ion secondary battery is given as an example of one form of energy storage device.

<Electricity storage device 100>
FIG. 1 is a perspective view showing a schematic diagram of the electric storage device 100. FIG. 2 is a schematic vertical cross-sectional view taken along line II-II in FIG. 1. FIG. 3 is a plan view showing a schematic diagram of the exterior body 12 and the sealing plate 18. In FIG. 2 and FIG. 3, the exterior body 12 and the sealing plate 18 are before being welded (before the molten solidified portion 50 is formed). In the following description, the symbols L, R, F, Rr, U, and D in the drawings represent left, right, front, rear, top, and bottom. In addition, the symbol X in the drawings indicates the short side direction of the electric storage device 100, the symbol Y indicates the long side direction of the electric storage device 100, and the symbol Z indicates the vertical direction. However, these are merely directions for convenience of description, and do not limit the installation form of the electric storage device 100 in any way.

As shown in Figures 1 and 2, the electricity storage device 100 includes a case 1, an electrode body 20, a positive electrode terminal 6, a negative electrode terminal 8, a positive electrode current collector 35, and a negative electrode current collector 45. Although not shown, the electricity storage device 100 further includes an electrolyte. The configuration of the electricity storage device 100 may be the same as that of a conventional device. The electricity storage device 100 is preferably a non-aqueous electrolyte secondary battery such as a lithium ion secondary battery.

The case 1 is a housing that houses the electrode body 20. As shown in Figs. 1 and 2, the case 1 includes an exterior body 12 having an opening 15, and a sealing plate 18 that seals the opening 15. The exterior body 12 and the sealing plate 18 have sizes according to the number of electrode bodies 20 (one or more) that are housed, their sizes, etc. The case 1 is preferably made of metal, and more preferably made of aluminum or an aluminum alloy mainly composed of aluminum. Here, the case 1 is made of aluminum. As shown in Fig. 1, the case 1 has a flat, bottomed, and generally rectangular parallelepiped shape (square).

As shown in Figs. 1 and 2, the exterior body 12 is a container with a bottom and a substantially rectangular parallelepiped shape with an opening 15 on one side (here, the top side). As shown in Fig. 1, the exterior body 12 has a substantially rectangular bottom 12d having a pair of short sides and a pair of long sides, a pair of short side walls 12a, 12b that extend upward from the short sides of the bottom 12d and face each other, and a pair of long side walls 12e, 12f that extend upward from the long sides of the bottom 12d and face each other. In this specification, the term "substantially rectangular" includes not only a perfect rectangular shape (rectangular shape), but also a shape in which the corners connecting the long and short sides of the rectangle are rounded or a shape with a notch at the corner.

An opening 15 is formed on one side of the exterior body 12 and is surrounded by a pair of short side walls 12a, 12b and a pair of long side walls 12e, 12f. As shown in FIG. 2, the bottom 12d faces the opening 15. The opening 15 includes a pair of opening long side portions 15e, 15f that correspond to the ends of the long side walls 12e, 12f, and a pair of opening short side portions 15a, 15b that correspond to the ends of the short side walls 12a, 12b (upper side in FIG. 2) on the periphery of the opening 15.

As shown in Figs. 1 and 2, the sealing plate 18 is a member that seals the opening 15 of the exterior body 12. Here, the sealing plate 18 is a plate-shaped member that is substantially rectangular in plan view. As shown in Fig. 3, the sealing plate 18 has a pair of sealing plate short sides 18a, 18b and a pair of sealing plate long sides 18e, 18f. As shown in Fig. 2, the sealing plate 18 is provided with a liquid injection hole 71, a gas exhaust valve 73, and terminal withdrawal holes 74, 75. The sealing plate 18 faces the bottom 12d of the exterior body 12.

As shown in FIG. 3, the outer peripheral surface of the sealing plate 18 and the inner surface (opening 15) of the exterior body 12 are arranged (engaged) to face each other, thereby forming the fitting portion 11. More specifically, the sealing plate short side portion 18a faces the opening short side portion 15a, the sealing plate short side portion 18b faces the opening short side portion 15b, the sealing plate long side portion 18e faces the opening long side portion 15e, and the sealing plate long side portion 18f faces the opening long side portion 15f. Here, the upper ends of the sealing plate 18 and the exterior body 12 (the upper end portion in FIG. 2) are flush in plan view. As shown in FIG. 3, the fitting portion 11 has short side regions 11a, 11b and long side regions 11e, 11f. The short side region 11a is an area consisting of the opening short side portion 15a and the sealing plate short side portion 18a, and the short side region 11b is an area consisting of the opening short side portion 15b and the sealing plate short side portion 18b. The long side region 11e is an area consisting of the opening long side portion 15e and the sealing plate long side portion 18e, and the long side region 11f is an area consisting of the opening long side portion 15f and the sealing plate long side portion 18f. As shown in FIG. 3, the fitting portion 11 has R portions 11g, 11h, 11i, and 11j provided between the short side regions 11a and 11b and the long side regions 11e and 11f. However, the R portions 11g, 11h, 11i, and 11j are not essential.

The liquid injection hole 71 is a through hole for injecting electrolyte into the case 1 after the sealing plate 18 is attached to the exterior body 12. Here, the liquid injection hole 71 is sealed by a sealing member 72 after the electrolyte is injected. The gas exhaust valve 73 is a thin-walled portion configured to break when the pressure inside the case 1 reaches or exceeds a predetermined value, thereby discharging gas inside the case 1 to the outside.

As the electrolyte, any electrolyte that has been publicly known and is used can be used without any particular limitation. As an example, a non-aqueous electrolyte in which a supporting salt (electrolyte salt) is dissolved in a non-aqueous solvent (organic solvent) is preferably used. As an example of the non-aqueous solvent, a carbonate-based solvent such as ethylene carbonate, dimethyl carbonate, ethyl methyl carbonate, etc. can be mentioned. As an example of the supporting salt, a fluorine-containing lithium salt such as _LiPF6 can be mentioned. The electrolyte may contain an additive as necessary.

The positive terminal 6 is attached to one end of the sealing plate 18 in the long side direction Y (the left end in FIG. 2). The negative terminal 8 is attached to the other end of the sealing plate 18 in the long side direction Y (the right end in FIG. 2). As shown in FIG. 2, the positive terminal 6 and the negative terminal 8 are inserted through the terminal pull-out holes 74, 75 and exposed on the outer surface of the sealing plate 18. As shown in FIG. 2, the positive terminal 6 is electrically connected to the positive electrode 3 of the electrode body 20 through the positive electrode current collector 35 inside the outer casing 12. The negative terminal 8 is electrically connected to the negative electrode 4 of the electrode body 20 through the negative electrode current collector 45 inside the outer casing 12. The positive terminal 6 and the negative terminal 8 are insulated from the sealing plate 18 by the gasket 76 and the insulator 78. A current interruption device (CID) may also be installed between the positive terminal 6 and the positive current collector 35 or between the negative terminal 8 and the negative current collector 45.

The positive electrode terminal 6 is preferably made of a metal, and more preferably made of, for example, aluminum or an aluminum alloy. The negative electrode terminal 8 is preferably made of a metal, and more preferably made of, for example, copper or a copper alloy. The negative electrode terminal 8 may be formed by joining two conductive members together. For example, the portion connected to the negative electrode current collecting member 45 may be made of copper or a copper alloy, and the portion exposed on the outer surface of the sealing plate 18 may be made of aluminum or an aluminum alloy.

The gasket 76 and the insulator 78 may be made of a material with excellent chemical resistance and weather resistance. The gasket 76 and the insulator 78 may be made of a resin material that is electrically insulating and elastically deformable, such as a fluorinated resin such as perfluoroalkoxy fluorine resin (PFA), polyphenylene sulfide resin (PPS), or aliphatic polyamide.

Here, the positive electrode terminal 6 is electrically connected to a plate-shaped positive electrode external conductive member 36 on the outside of the case 1. Similarly, the negative electrode terminal 8 is electrically connected to a plate-shaped negative electrode external conductive member 46 on the outside of the case 1. The positive electrode external conductive member 36 and the negative electrode external conductive member 46 are connected to other electricity storage devices and external equipment via external connection members such as bus bars. The positive electrode external conductive member 36 and the negative electrode external conductive member 46 are preferably made of a metal with excellent conductivity such as aluminum, an aluminum alloy, copper, or a copper alloy. However, the positive electrode external conductive member 36 and the negative electrode external conductive member 46 are not essential and may be omitted in other embodiments.

The electrode body 20 may be the same as in the past, and is not particularly limited. As shown in FIG. 2, the electrode body 20 has a positive electrode 3 and a negative electrode 4. Here, the electrode body 20 is a flat wound electrode body in which a strip-shaped positive electrode 3 and a strip-shaped negative electrode 4 are stacked in an insulated state via a strip-shaped separator 7, and wound around a winding axis. However, the electrode body 20 may be a laminated electrode body in which a square-shaped (typically rectangular) positive electrode 3 and a square-shaped (typically rectangular) negative electrode 4 are stacked in an insulated state. In addition, the number of electrode bodies 20 arranged inside one exterior body 12 is not particularly limited, and may be two or more (multiple). The positive electrode 3 and the negative electrode 4 are an example of an "electrode" in the technology disclosed herein.

As shown in FIG. 2, the positive electrode 3 has a positive electrode current collector 30 and a positive electrode active material layer 31 fixed onto the positive electrode current collector 30. The positive electrode current collector 30 is made of a conductive metal such as aluminum, an aluminum alloy, nickel, or stainless steel. The positive electrode active material layer 31 is a layer containing a positive electrode active material (e.g., a lithium transition metal composite oxide such as a lithium nickel cobalt manganese composite oxide) that can reversibly store and release charge carriers.

The negative electrode 4 has a negative electrode current collector 40 and a negative electrode active material layer 41 fixed onto the negative electrode current collector 40. The negative electrode current collector 40 is made of a conductive metal such as copper, a copper alloy, nickel, or stainless steel. The negative electrode active material layer 41 is a layer containing a negative electrode active material (e.g., a carbon material such as graphite) that can reversibly store and release charge carriers.

The separator 7 is a member that insulates the positive electrode active material layer 31 of the positive electrode 3 from the negative electrode active material layer 41 of the negative electrode 4. As the separator 7, for example, a porous resin sheet made of a polyolefin resin such as polyethylene (PE) or polypropylene (PP) is suitable. In addition, a heat resistance layer (HRL) containing an inorganic filler may be provided on the surface of the separator 7.

2, at the left end of the long side direction Y of the electrode body 20, a part of the positive electrode collector 30 (positive electrode collector exposed part) on which the positive electrode active material layer 31 is not formed protrudes from the laminated part. A positive electrode collector member 35 is attached to the positive electrode collector exposed part. The positive electrode collector member 35 may be made of the same metal material as the positive electrode collector 30, for example, a conductive metal such as aluminum, an aluminum alloy, nickel, or stainless steel. In addition, at the right end of the long side direction Y of the electrode body 20, a part of the negative electrode collector 40 (negative electrode collector exposed part) on which the negative electrode active material layer 41 is not formed protrudes from the laminated part. A negative electrode collector member 45 is attached to the negative electrode collector exposed part. The material (metal type) of the negative electrode collector member 45 may be different from that of the positive electrode collector member 35. The negative electrode current collector 45 may be made of the same metal as the negative electrode current collector 40, such as a conductive metal such as copper, a copper alloy, nickel, or stainless steel.

<Method of Manufacturing Electricity Storage Device 100>
4 is a flow diagram showing a method for manufacturing an electricity storage device 100 according to one embodiment. The electricity storage device 100 disclosed herein can be manufactured by a manufacturing method including a sealing plate fitting step S10 and a laser welding step S20, and is characterized by performing the laser welding step S20. In addition to the above steps, the manufacturing method for the electricity storage device 100 disclosed herein may further include other steps at any stage, and the other manufacturing processes may be similar to conventional methods.

(Sealing plate fitting process S10)
In the sealing plate fitting step S10, the electrode body 20 is accommodated in the exterior body 12, and the sealing plate 18 is fitted into the opening 15 of the exterior body 12. First, as shown in FIG. 2, the positive electrode terminal 6 and the negative electrode terminal 8 are inserted into the terminal drawing holes 74, 75 via a gasket 76 and an insulator 78, and are attached so that one end is exposed on the outer surface of the sealing plate 18. The other end of the positive electrode terminal 6 is electrically connected to the positive electrode 3 of the electrode body 20 via a positive electrode current collector 35. Meanwhile, the other end of the negative electrode terminal 8 is electrically connected to the negative electrode 4 of the electrode body 20 via a negative electrode current collector 45. Then, the electrode body 20 is accommodated in the exterior body 12, and the sealing plate 18 is fitted into the opening 15 of the exterior body 12. As a result, the upper end of the exterior body 12 and the sealing plate 18 are flush with each other. Additionally, the outer peripheral surface of sealing plate 18 faces the inner surface of exterior body 12 (opening 15).

(Laser welding step S20)
In the laser welding step S20, after the sealing plate fitting step S10, the sealing plate 18 and the opening 15 of the case 1 are scanned with the laser light L over the entire circumference, thereby laser welding the sealing plate 18 and the exterior body 12. In this embodiment, as shown by the arrow in FIG. 3, the laser light L is scanned from the start point LS in the short side region 11a along the fitting portion 11 through the short side region 11a, the R portion 11g, the long side region 11e, the R portion 11h, the short side region 11b, the R portion 11i, the long side region 11f, and the R portion 11j in this order, passing through the start point LS in the short side region 11a, and to the end point LE in the short side region 11a. As a result, a molten solidified portion 50 (see FIG. 13) is formed, and the sealing plate 18 and the exterior body 12 are joined. The case 1 is hermetically sealed (sealed) by the laser welding step S20.

Figure 19 is a vertical cross-sectional view showing the vicinity of the molten solidified portion 50 according to the conventional example. Conventionally, in the laser welding as described above, a part of the sealing plate 18 and the exterior body 12 (shown by imaginary lines) melts by irradiation with laser light, and the molten part solidifies to form the molten solidified portion 50. The shape of the molten solidified portion 50 is determined, for example, by the flow of the molten metal and the influence of the surface tension. In detail, the molten solidified portion 50 is formed by solidifying in a raised shape due to the surface tension of the molten metal. Therefore, as shown in Figure 19, there is a risk that a part of the molten solidified portion 50 protrudes (projects) outward from the short side walls 12a, 12b of the exterior body 12. Due to the protrusion of the molten solidified portion 50, the size of the electric storage device 100 (case 1) varies in the long side direction Y. Therefore, the present inventor wants to suppress the protrusion of the molten solidified portion 50 outward from the short side walls 12a, 12b of the exterior body 12. In this specification, "formed outside the exterior body (protruding)" means that at least a part of the molten solidified portion 50 protrudes from the exterior body 12 in the long side direction Y. Protruding of at least a part of the molten solidified portion 50 in the short side direction X and the vertical direction Z is not included in "protruding outward."

The technology disclosed herein has been created in view of the above-mentioned problems. The technology disclosed herein is characterized by the laser light L used in the laser welding process S20. The laser light L includes a long side region irradiating laser light La that irradiates the long side regions 11e and 11f, and a short side region irradiating laser light Lb that irradiates the short side regions 11a and 11b (see Figures 5 and 6). The laser light L (long side region irradiating laser light La and short side region irradiating laser light Lb) includes a first laser light L1 consisting of at least one beam that irradiates the sealing plate 18 (sealing plate long side portions 18e, 18f and sealing plate short side portions 18a, 18b), and a second laser light L2 consisting of at least one beam that irradiates the opening 15 (opening long side portions 15e, 15f and opening short side portions 15a, 15b). The energy of the laser light L (short side region irradiating laser light Lb) irradiating the short side regions 11a and 11b is smaller than the energy of the laser light L (long side region irradiating laser light La) irradiating the long side regions 11e and 11f, and the energy of the second laser light L2 irradiating the short side regions 11a and 11b (opening short side portions 15a and 15b) is smaller than the energy of the first laser light L1 irradiating the short side regions 11a and 11b (sealing plate short side portion 18b). The long side region irradiating laser light La is an example of the "laser light L irradiating the long side region" in the technology disclosed herein, and the short side region irradiating laser light Lb is an example of the "laser light L irradiating the short side region" in the technology disclosed herein.

The technology disclosed herein will be described below with reference to examples, but the present invention is not limited to such examples. FIG. 5 is a plan view that shows a schematic diagram of a long side region irradiating laser light La according to an example. FIG. 6 is a plan view that shows a schematic diagram of a short side region irradiating laser light Lb according to an example. In addition, in FIGS. 5 and 6, the traveling directions of the long side region irradiating laser light La and the short side region irradiating laser light Lb are indicated by white arrows. As shown in FIGS. 5 and 6, here, the laser light L (long side region irradiating laser light La and short side region irradiating laser light Lb) has a first laser light L1 and a second laser light L2, and further a central beam 90 that irradiates the boundary between the opening 15 and the sealing plate 18. In addition, the central beam 90 may be a beam consisting of one point, or may be a multi-point beam consisting of multiple points close to each other. Here, the central beam 90 is one point. Here, the first laser light L1 and the second laser light L2 are arranged around the central beam 90. Note that the energy per point of the peripheral beams 91 to 98 is the same for the short side region irradiating laser light Lb and the long side region irradiating laser light La. The energy per point of the central beam 90 is also the same for the short side region irradiating laser light Lb and the long side region irradiating laser light La.

As shown in FIG. 5, the long side region irradiating laser light La has a central beam 90, a first laser light L1 consisting of four peripheral beams 91-94, and a second laser light L2 consisting of four peripheral beams 95-98. As shown in FIG. 5, the long side region irradiating laser light La is arranged in a substantially X-shape in a plan view. On the other hand, as shown in FIG. 6, the short side region irradiating laser light Lb has a pattern in which the peripheral beams 91-94 of the first laser light L1 are arranged in the same pattern as the long side region irradiating laser light La, but the peripheral beams 95 and 98 of the second laser light L2 are missing. That is, the energy of the short side region irradiating laser light Lb (here, the sum of the energies of the central beam 90 and the peripheral beams 91-98) is smaller than the energy of the long side region irradiating laser light La (the sum of the energies of the central beam 90 and the peripheral beams 91-98). 6, in the short side region irradiating laser light Lb, the number of beam points (2 points) of the second laser light L2 is smaller than the number of beam points (4 points) of the first laser light L1. In other words, in the short side region irradiating laser light Lb, the energy of the second laser light L2 irradiating the short side regions 11a, 11b (opening short side portions 15a, 15b) is smaller than the energy of the first laser light L1 irradiating the short side regions 11a, 11b (sealing plate short side portions 18a, 18b).

Figure 7 is a plan view showing a schematic diagram of the long side region 11e being irradiated with a long side region irradiation laser light La according to one embodiment. Figure 8 is a plan view showing a schematic diagram of the long side region 11f being irradiated with a long side region irradiation laser light La according to one embodiment. Figure 9 is a plan view showing a schematic diagram of the short side region 11a being irradiated with a short side region irradiation laser light Lb according to one embodiment. Figure 10 is a plan view showing a schematic diagram of the short side region 11b being irradiated with a short side region irradiation laser light Lb according to one embodiment. In Figures 7 to 10, the directions of travel of the long side region irradiation laser light La and the short side region irradiation laser light Lb are indicated by white arrows. Figure 11 is a vertical cross-sectional view showing a schematic diagram of the long side region irradiation laser light La being irradiated with a long side region 11e according to one embodiment. FIG. 12 is a vertical cross-sectional view showing the state in which the short side region 11a according to one embodiment is irradiated with the short side region irradiation laser light Lb. FIG. 13 is a vertical cross-sectional view showing the formation of the molten solidified portion 50 in the short side region 11a according to one embodiment.

As shown in FIG. 7, of the long side region irradiation laser light La arranged in the long side region 11e, the center beam 90 is irradiated to the boundary between the opening long side portion 15e and the sealing plate long side portion 18e. The surrounding beams 91 to 94 arranged at one end in the short side direction X (the front side in FIG. 7) are irradiated to the sealing plate long side portion 18e as the first laser beam L1. The surrounding beams 95 to 98 arranged at the other end in the short side direction X (the rear side in FIG. 7) are irradiated to the opening long side portion 15e as the second laser beam L2. Similarly, as shown in FIG. 8, of the long side region irradiation laser light La arranged in the long side region 11f, the center beam 90 is irradiated to the boundary between the opening long side portion 15f and the sealing plate long side portion 18f. The surrounding beams 91 to 94 arranged at one end in the short side direction X (the rear side in FIG. 8) are irradiated to the sealing plate long side portion 18f as the first laser beam L1. The peripheral beams 95-98 arranged at the other end in the short side direction X (the front side in FIG. 8) are irradiated onto the opening long side portion 15f as the second laser light L2.

As shown in FIG. 9, of the short side region irradiation laser light Lb arranged in the short side region 11a, the center beam 90 is irradiated to the boundary between the opening short side portion 15a and the sealing plate short side portion 18a. The surrounding beams 91 to 94 arranged at one end in the long side direction Y (right side in FIG. 9) are irradiated to the sealing plate short side portion 18a as the first laser light L1. On the other hand, the surrounding beams 96 and 97 arranged at the other end in the long side direction Y (left side in FIG. 9) are irradiated to the opening short side portion 15a as the second laser light L2. As shown in FIG. 10, of the short side region irradiation laser light Lb arranged in the short side region 11b, the center beam 90 is irradiated to the boundary between the opening short side portion 15b and the sealing plate short side portion 18b. The surrounding beams 91 to 94 arranged at one end in the long side direction Y (left side in FIG. 10) are irradiated to the sealing plate short side portion 18b as the first laser light L1. On the other hand, the surrounding beams 96 and 97 arranged at the other end in the long side direction Y (the right side in FIG. 10) are irradiated to the opening short side portion 15b as the second laser light L2.

At this time, as shown in Figures 11 and 12, the energy of the short side region irradiating laser light Lb irradiating the short side region 11a is smaller than the long side region irradiating laser light La irradiating the long side region 11e. Furthermore, as shown in Figure 12, among the short side region irradiating laser light Lb, the energy of the second laser light L2 irradiating the opening short side portion 15a is smaller than the energy of the first laser light L1 irradiating the sealing plate short side portion 18a. Therefore, the melted portion 51 of the short side region 11a is smaller than the melted portion 51 of the long side region 11e. Also, for the short side region 11a, the melted portion 51 of the opening short side portion 15a is smaller than the melted portion 51 of the sealing plate short side portion 18a. As a result, as shown in FIG. 13, the melting of the opening short side portion 15a (short side wall 12a) is suppressed in the short side region 11a compared to the sealing plate short side portion 18a, and the melt solidification portion 50 can be suppressed from being formed outside the short side wall 12a of the exterior body 12. Here, the short side region 11a and the long side region 11e are described as an example, but the short side region 11b and the long side region 11f also have the same effect as the short side region 11a and the long side region 11e. Therefore, for the short side region 11b as well, by irradiating the first laser light L1 of the short side region irradiation laser light Lb to the sealing plate short side portion 18b and the second laser light L2 to the opening short side portion 15b, the melting of the opening short side portion 15b (short side wall 12b) is suppressed, and the melt solidification portion 50 can be suppressed from being formed outside the short side wall 12b of the exterior body 12. This makes it possible to prevent the melt-solidified portion 50 from protruding outward from the short side walls 12a, 12b of the exterior body 12. Therefore, it is possible to provide an electric storage device 100 with improved dimensional accuracy of the case 1 in the long side direction Y.

In addition, in some preferred embodiments, as shown in Figures 5 and 6, the number of beam points (4 points) of the first laser light L1 in the short side region irradiating laser light Lb is the same as the number of beam points (4 points) of the first laser light L1 in the long side region irradiating laser light La, and the number of beam points (2 points) of the second laser light L2 in the short side region irradiating laser light Lb is less than the number of beam points (4 points) of the second laser light L2 in the long side region irradiating laser light La. This makes it possible to more preferably suppress the protrusion of the molten solidification portion 50 outward from the short side walls 12a, 12b of the exterior body 12.

In the short side regions 11a and 11b, the energy of the laser light L (short side region irradiated laser light Lb) (total of the energies of the first laser light L1 and the second laser light. Furthermore, if the central beam 90 is included, total of the energies of the first laser light L1, the second laser light, and the central beam 90) is preferably 1000 W or more, more preferably 1500 W or more. On the other hand, from the viewpoint of suppressing the protrusion of the molten solidified portion 50 outwardly of the short side walls 12a and 12b, it is preferably 4000 W or less, more preferably 3000 W or less. In addition, in the short side regions 11a and 11b, the ratio of the energy of the first laser light L1 to the energy of the second laser light L2 is preferably 5:1 to 1.25:1, more preferably 5:1 to 2:1. If the energy ratio is made smaller than the above range, the protrusion suppression of the molten solidified portion cannot be suitably obtained, and if the energy ratio is made larger than the above range, poor welding may occur due to insufficient welding energy of the opening 15, which is not preferable.

As shown in FIG. 3, the scanning path of the laser light L is counterclockwise from the start point LS to the end point LE here, but is not limited to this. As long as it is possible to form an annular molten solidification portion 50 and seal the case 1, the start point LS and the end point LE of the scanning path of the laser light L may be changed. In addition, the scanning path of the laser light L may be either clockwise or counterclockwise.

The method of generating the laser light L used in the laser welding process S20 may be a bundle of multiple laser sources irradiated from multiple laser devices, pattern formation using a dynamic beam laser, or branching of a single laser source using a diffractive optical element (DOE) or the like. Among these, the laser light L according to this embodiment can be easily generated by transmission diffraction using a diffractive optical element. For this reason, generation of the laser light L by transmission diffraction using a diffractive optical element (DOE) can be more preferably adopted. In addition, the angle between the laser irradiation direction and the exterior body 12 and the sealing plate 18 (horizontal plane) is typically about 90±10°, for example about 90±5°.

Below, an embodiment of the laser welding process S20 will be described using laser welding using an optical diffraction element as an example. However, the present invention is not limited to this. FIG. 14 is a schematic diagram showing a laser welding device 120 used in the laser welding process S20 according to one embodiment. As shown in FIG. 14, the laser welding device 120 here includes a control unit 122, a laser oscillator 124, a comeriter (comerit lens) 130, a diffractive optical element 140, a Z lens 160, a galvano scanner 170, a condenser lens 180, and a protective glass 190.

The control unit 122 is a mechanism that controls the operation of the laser welding device 120. As shown in FIG. 14, here, the control unit 122 is connected to the laser oscillator 124, the diffractive optical element 140 (moving unit 146), and the galvanometer scanner 170 (first reflector 171, second reflector 172). This allows the control unit 122 to control the operation of the laser oscillator 124, the diffractive optical element 140, and the galvanometer scanner 170 (first reflector 171, second reflector 172).

The laser oscillator 124 is a laser light source that generates laser light under the control of the control unit 122. Here, a fiber laser is used as the laser oscillator 124. The laser oscillator 124 is connected to an emission port 123 made of an optical fiber. The laser generated from the laser oscillator 124 is emitted from the emission port 123 as emitted laser light 197 and enters the comet 130.

The comelitator 130 is a lens that converts (adjusts) the emitted laser light 197 to a parallel state. The comelitator 130 is disposed downstream (output side) of the exit port 123. As shown in FIG. 14, the comelitator 130 converts the emitted laser light 197 incident from the exit port 123 into a parallel laser light 198 and emits it.

The diffractive optical element 140 is an element that converts the parallel laser beam 198 incident from the cometer 130 into a diffracted multi-laser beam 199 and emits it. The diffractive optical element 140 is disposed downstream (output side) of the cometer 130. FIG. 15 is a schematic diagram showing the diffractive optical element 140 according to one embodiment. FIG. 16 is a schematic diagram showing the configuration of the diffractive optical element section 142 according to one embodiment and the movement of the diffraction region 143. In FIG. 15, for convenience of explanation, the movement of the diffractive optical element 140 by the moving unit 146 is shown by virtual lines. As shown in FIG. 15, the diffractive optical element 140 here includes the diffractive optical element section 142, a holding section 144 that holds the diffractive optical element section 142, and a moving unit 146 that moves the diffractive optical element section 142.

The diffractive optical element part 142 is a member that defines the irradiation pattern PT of the diffracted multi-laser light 199. As shown in FIG. 15, the diffractive optical element part 142 is a circular flat plate here. Here, as shown in FIGS. 15 and 16, the diffractive optical element part 142 has four areas, a first pattern area 151, a second pattern area 152, a third pattern area 153, and a fourth pattern area 154. In the first pattern area 151, a diffractive optical pattern that generates the first irradiation pattern PT1 is formed. In the second pattern area 152, a diffractive optical pattern that generates the second irradiation pattern PT2 is formed. In the third pattern area 153, a diffractive optical pattern that generates the third irradiation pattern PT3 is formed. In the fourth pattern area 154, a diffractive optical pattern that generates the fourth irradiation pattern PT4 is formed. As shown in FIG. 9, the first irradiation pattern PT1 corresponds to the short side area irradiation laser light Lb that irradiates the short side area 11a. As shown in Fig. 7, the second irradiation pattern PT2 corresponds to the long side region irradiation laser light La that irradiates the long side region 11e. As shown in Fig. 10, the third irradiation pattern PT3 corresponds to the short side region irradiation laser light Lb that irradiates the short side region 11b. As shown in Fig. 8, the fourth irradiation pattern PT4 corresponds to the long side region irradiation laser light La that irradiates the long side region 11f.

The moving unit 146 is a mechanism for moving the diffractive optical element section 142 in the X and Y directions in FIG. 15. The moving unit 146 is connected to the control section 122 and is coupled to the holding section 144. Under the control of the control section 122, the diffractive optical element 140 (diffractive optical element section 142) can be moved relative to the parallel laser light 198 incident from the cometer 130 (as shown by the virtual line in FIG. 15). Details will be described later, but by moving the diffraction region 143 using the moving unit 146 by the control section 122 (see FIG. 16), the diffraction region 143 into which the parallel laser light 198 is incident and which emits the diffracted multi-laser light 199 can be moved. Therefore, the irradiation pattern PT (first to fourth irradiation patterns PT1 to PT4) of the diffracted multi-laser light 199 can be changed. Note that in this case, the diffraction region 143 moves due to the movement of the diffractive optical element 140, and the parallel laser light 198 itself does not move.

The Z lens 160 is a lens that adjusts the focal position SP of the diffracted multi-laser light 199. By moving the Z lens 160 in the optical axis direction (in FIG. 14, the up and down Z direction) under the control of the control unit 122, the focal position SP of the diffracted multi-laser light 199 can be moved (adjusted) in the optical axis direction.

The galvano scanner 170 is a device that controls the irradiation position of the laser light L. As shown in FIG. 14, the galvano scanner 170 includes a first reflecting mirror 171 and a second reflecting mirror 172, which are each controlled by the control unit 122. The first reflecting mirror 171 can deflect the diffracted multi-laser light 199 that has passed through the Z lens 160 and is incident thereon in the Y direction by changing the deflection angle under the control of the control unit 122. The second reflecting mirror 172 can deflect the diffracted multi-laser light 199 that has been deflected and reflected by the first reflecting mirror 171 in the X direction by changing the deflection angle under the control of the control unit 122.

The condenser lens 180 and protective glass 190 are disposed downstream (output side) of the galvano scanner 170. The diffracted multi-laser light 199 reflected and deflected by the second reflector 172 passes through the condenser lens 180 and protective glass 190, is focused at the focal position SP adjusted by the Z lens 160, and is scanned (irradiated) onto the case 1 as laser light L.

Here, the control unit 122 drives the moving unit 146 in conjunction with the deflection of the galvano scanner 170 (i.e., in conjunction with the movement of the laser light L) to move the diffractive optical member 140 (diffractive optical element unit 142) so that the diffraction region 143 follows the movement path 148. As shown in FIG. 16, in detail, the diffraction region 143 is moved from a start point 148S in the first pattern region 151 to the second pattern region 152, the third pattern region 153, and the fourth pattern region 154 in that order (illustrated by a hollow arrow), and after passing through the start point 148S in the first pattern region 151, to an end point 148E in the first pattern region 151. As a result, a beam light L having an irradiation pattern PT (first to fourth irradiation patterns PT1 to PT4) corresponding to the first to fourth pattern regions 151 to 154 is obtained.

Although the manufacturing method of the electric storage device 100 according to the present embodiment has been described above, the manufacturing method of the electric storage device 100 disclosed herein is not limited to the above-mentioned embodiment. For example, in the above-mentioned embodiment, the pattern of the short side region irradiation laser light Lb (FIG. 6) had a line-symmetric pattern in which the peripheral beams 95 and 98 of the second laser light L2 were missing compared to the long side region irradiation laser light La. However, the present invention is not limited to this. FIG. 17 is a plan view that shows a pattern of the short side region irradiation laser light Lb according to the modified example. FIG. 18 is a vertical cross-sectional view that shows a state in which the short side region irradiation laser light Lb according to the modified example is irradiated. For example, as shown in FIG. 17, here, the short side region irradiation laser light Lb has a pattern in which the pattern of the first laser light L1 is similar, but the peripheral beams 95 and 96 of the second laser light L2 are missing. Here, the short side region irradiation laser light Lb is non-line-symmetric. As shown in FIG. 18, even in this modified example, the melting of the opening short side portion 15a (short side wall 12a) is suppressed compared to the sealing plate short side portion 18a in the short side region 11a, so that the molten solidified portion 50 can be suppressed from being formed outside the short side wall 12a of the exterior body 12. Therefore, the protrusion of the molten solidified portion 50 from the short side walls 12a and 12b can be suitably suppressed. In addition, the laser light L may be generated having a different irradiation pattern without being limited to the above-mentioned pattern configuration, and the intensity of the peripheral beams 91 to 98 of the laser light L may be made different. The arrangement or presence or absence of the peripheral beams 91 to 98 of the laser light L, and the strength of each of the peripheral beams 91 to 98 can be adjusted, for example, by changing the configuration of the diffractive optical element unit 142. In addition, the shape of the pattern of the laser light L is not limited to this, and may be, for example, a five-point beam (a five-point dice shape) or a ring beam.

In addition, as another aspect of the technology disclosed herein, an electric storage device 100 is provided. The electric storage device 100 disclosed herein includes an electrode body 20, an exterior body 12 (short side walls 12a, 12b and long side walls 12e, 12f), a sealing plate 18, a positive electrode terminal 6, a negative electrode terminal 8, and an annular molten solidified portion 50. The electric storage device 100 is characterized by the molten solidified portion 50, and other configurations may be the same as those of the conventional device. The molten solidified portion 50 does not protrude outward from the short side walls 12a and 12b, and at least a part of the molten solidified portion 50 faces the positive electrode terminal 6 or the negative electrode terminal 8 and protrudes outward from the long side walls 12e or 12f. This provides an electric storage device 100 with improved reliability in dimensional accuracy in the long side direction Y.

The power storage device 100 can be used for various purposes, but typically can be used as a power source (driving power source) for motors mounted on various vehicles, such as passenger cars and trucks. The type of vehicle is not particularly limited, but examples include plug-in hybrid vehicles (PHEVs), hybrid electric vehicles (HEVs), and battery electric vehicles (BEVs).

Although several embodiments of the technology disclosed herein have been described above, the above embodiments are merely examples. The technology disclosed herein can be implemented in various other forms. The technology disclosed herein can be implemented based on the contents disclosed in this specification and the technical common sense in the relevant field. The technology described in the claims includes various modifications and variations of the above-exemplified embodiments. For example, it is possible to replace part of the above-mentioned embodiments with other modified forms, and it is also possible to add other modified forms to the above-mentioned embodiments. Furthermore, if a technical feature is not described as essential, it can also be deleted as appropriate.

As described above, specific aspects of the technology disclosed herein include those described in the following sections.
Item 1: A method for manufacturing an electricity storage device comprising: an electrode body having an electrode; a rectangular bottom portion, a pair of short side walls extending from a short side of the bottom and facing each other, a pair of long side walls extending from a long side of the bottom and facing each other, an opening facing the bottom, and a pair of opening long side portions corresponding to ends of the long side walls and a pair of opening short side portions corresponding to ends of the short side walls among the periphery of the opening, and containing the electrode body; a substantially rectangular sealing plate having a pair of sealing plate long side portions and a pair of sealing plate short side portions and sealing the opening of the exterior body; and a terminal attached to the sealing plate and electrically connected to the electrode body, the method comprising the steps of: containing the electrode body in the exterior body, and a sealing plate fitting step of fitting the sealing plate into the opening of the exterior body; and scanning a laser beam L over the entire periphery of the sealing plate and the opening to form a sealing plate and a sealing plate fitting step of fitting the sealing plate into the opening of the exterior body to form a sealing plate and a sealing plate fitting step of fitting the sealing plate into the opening of the exterior body to form a sealing plate and a sealing plate fitting step of fitting the sealing plate and the sealing plate together. and a laser welding step of laser-welding an outer casing to an insulating body, wherein in the laser welding step, the laser light L is a multi-point laser light including a first laser light L1 consisting of at least one point beam irradiating the long side portion and the short side portion of the sealing plate, and a second laser light L2 consisting of at least one point beam irradiating the long side portion and the short side portion of the opening, wherein when a region consisting of the long side portion of the opening and the long side portion of the sealing plate is defined as a long side region, and a region consisting of the short side portion of the opening and the short side portion of the sealing plate is defined as a short side region, an energy of the laser light L irradiating the short side region is smaller than an energy of the laser light L irradiating the long side region, and an energy of the second laser light L2 irradiating the short side region is smaller than an energy of the first laser light L1 irradiating the short side region.
Item 2: The method for producing an electricity storage device according to item 1, wherein the laser light L is generated by transmission and diffraction using a diffractive optical element.
Item 3: A method for manufacturing an electricity storage device described in Item 1 or 2, wherein the number of beam points of the first laser light L1 irradiating the short side region is the same as the number of beam points of the first laser light L1 irradiating the long side region, and the number of beam points of the second laser light L2 irradiating the short side region is less than the number of beam points of the second laser light L2 irradiating the long side region.
Item 4: An electricity storage device comprising: an electrode body having an electrode; a rectangular bottom; a pair of short side walls extending from short sides of the bottom and facing each other; a pair of long side walls extending from long sides of the bottom and facing each other; and an opening facing the bottom, the device comprising: an exterior body that houses the electrode body; a substantially rectangular sealing plate that seals the opening of the exterior body; a terminal that is attached to the sealing plate and is electrically connected to the electrode body; and an annular molten solidified portion formed at a fitting portion between the opening of the exterior body and the sealing plate, the molten solidified portion does not protrude outward from the short side walls, and at least a portion of the molten solidified portion faces the terminal and protrudes outward from the long side walls.

1 Case 3 Positive electrode 4 Negative electrode 6 Positive electrode terminal 7 Separator 8 Negative electrode terminal 11 Fitting portion 11a, 11b Short side region 11e, 11f Long side region 11g, 11h, 11i, 11j R portion 12 Exterior body 12d Bottom 12a, 12b Short side wall 12e, 12f Long side wall 15 Opening 15a, 15b Opening short side portion 15e, 15f Opening long side portion 18 Sealing plate 18a, 18b Sealing plate short side portion 18e, 18f Sealing plate long side portion 20 Electrode body 30 Positive electrode current collector 31 Positive electrode active material layer 35 Positive electrode current collector member 36 Positive electrode external conductive member 40 Negative electrode current collector 41 Negative electrode active material layer 45 Negative electrode current collector member 46 Negative electrode external conductive member 50 Melted and solidified portion 71 Liquid inlet holes 74, 75 Terminal outlet hole 76 Gasket 78 Insulator 90 Central beams 91 to 98 Surrounding beams 100 Electricity storage device 120 Laser welding apparatus 122 Control unit 124 Laser oscillator 130 Cometer 140 Diffractive optical member 142 Diffractive optical element unit 143 Diffractive region 144 Holding unit 146 Moving unit 151 First pattern region 152 Second pattern region 153 Third pattern region 154 Fourth pattern region 160 Z lens 170 Galvano scanner 180 Condenser lens 190 Protective glass 197 Emitted laser light 198 Parallel laser light 199 Diffracted multi-laser light L Laser light La Long side region irradiating laser light Lb Short side region irradiating laser light L1 First laser light L2 Second laser light S10 Sealing plate fitting process S20 Laser welding process

Claims (3)

An electrode body having an electrode;
an exterior body for housing the electrode assembly, the exterior body comprising: a rectangular bottom portion; a pair of short side walls extending from short sides of the bottom portion and facing each other; a pair of long side walls extending from long sides of the bottom portion and facing each other; an opening portion facing the bottom portion; and a pair of opening long side portions corresponding to ends of the long side walls and a pair of opening short side portions corresponding to ends of the short side walls, among the periphery of the opening portion;
a substantially rectangular sealing plate having a pair of sealing plate long side portions and a pair of sealing plate short side portions and sealing the opening of the exterior body;
a terminal attached to the sealing plate and electrically connected to the electrode body;
A method for manufacturing an electricity storage device comprising:
a sealing plate fitting step of housing the electrode assembly in the exterior body and fitting the sealing plate into the opening of the exterior body;
a laser welding process of laser-welding the sealing plate and the exterior body by scanning a laser beam L over the entire circumference of the sealing plate and the opening;
Equipped with
In the laser welding step,
The laser light L is
a first laser light L1 consisting of at least one beam point irradiating the long side portion and the short side portion of the sealing plate;
a second laser light L2 consisting of at least one point beam irradiating the opening long side portion and the opening short side portion;
When a region consisting of the long side portion of the opening and the long side portion of the sealing plate is defined as a long side region, and a region consisting of the short side portion of the opening and the short side portion of the sealing plate is defined as a short side region,
The energy of the laser light L irradiating the short side region is smaller than the energy of the laser light L irradiating the long side region,
The energy of the second laser light L2 irradiating the short side region is smaller than the energy of the first laser light L1 irradiating the short side region.
A method for manufacturing an electricity storage device. The laser light L is generated by transmitting and diffracting the light using a diffractive optical element.
A method for producing the electricity storage device according to claim 1 . The number of beam points of the first laser light L1 irradiating the short side region is the same as the number of beam points of the first laser light L1 irradiating the long side region,
the number of beam points of the second laser light L2 irradiating the short side region is smaller than the number of beam points of the second laser light L2 irradiating the long side region;
A method for producing the electricity storage device according to claim 1 or 2.

Images