Method for manufacturing power storage device, and power storage device

Abstract

A method for manufacturing a power storage device includes preparing an electrode group having a structure in which a plurality of exposed portions (12a) of a current collector (12) are arranged, bringing the plurality of arranged exposed portions (12a) into contact with a first surface (21a) of a current collector plate (20, 22), irradiating a second surface (21b) of the current collector plate (20, 22) with laser light (L), scanning a scanning region (58) of the current collector plate (20, 22) with the laser light (L), and bonding the plurality of exposed portions (12a) to the first surface (21a), on the first surface (21a), a plurality of molten marks (60) and non-molten portions (62) located between the molten marks (60) adjacent to each other are formed.

Description

Technical Field

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

[0002] Conventionally, a power storage device in which an electrode group is housed in an outer can has been known. In such a power storage device, a current collector plate is welded to an end portion of the electrode group (see, for example, Patent Document 1).

[0003] Prior Art Documents

[0004] Patent Documents

[0005] Patent Document 1: Japanese Unexamined Patent Application Publication No. 2008-166030 Summary of the Invention

[0006] The inventors of the present invention have repeatedly and intensively studied a power storage device in which an electrode group and a current collector plate are joined, and finally found that there is still room for improving the quality of existing power storage devices.

[0007] The present disclosure has been made in view of such circumstances, and one of its objects is to provide a technology for improving the quality of a power storage device.

[0008] Method for Solving Technical Problems

[0009] One aspect of the present disclosure is a method for manufacturing a power storage device. The manufacturing method includes: preparing an electrode group having a current collector in which electrode active material layers are laminated, the electrode group having a structure in which a plurality of exposed portions not covered with the electrode active material layer in the current collector are arranged, bringing the plurality of arranged exposed portions into contact with a first surface of a current collector plate, irradiating a second surface of the current collector plate opposite to the first surface with a laser, scanning a scanning region of the current collector plate that overlaps the plurality of arranged exposed portions and extends in the arrangement direction of the exposed portions with the laser, joining the plurality of exposed portions to the first surface, and in this joining, forming on the first surface: a plurality of melting marks having a size in the scanning direction of the laser larger than a size in a direction orthogonal to the scanning direction, and non-melting portions located between adjacent melting marks.

[0010] Another aspect of the present disclosure is a power storage device. The power storage device includes: an electrode group having a current collector in which electrode active material layers are laminated; and a current collector plate joined to the current collector. The electrode group has a structure in which a plurality of exposed portions not covered with the electrode active material layer in the current collector are arranged, and the plurality of arranged exposed portions are joined to a first surface of the current collector plate. The first surface has, in a region that overlaps the plurality of arranged exposed portions and extends in the arrangement direction of the exposed portions, a plurality of melting marks having a size in the arrangement direction larger than a size in a direction orthogonal to the arrangement direction, and non-melting portions located between adjacent melting marks.

[0011] Any combination of the above-described constituent elements, and a solution obtained by converting the expression of the present disclosure among methods, apparatuses, systems, etc. is also effective as a solution of the present disclosure.

[0012] Advantageous Effects of the Invention

[0013] According to the present disclosure, improvement in the quality of the power storage device can be achieved. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 is a cross-sectional view of the power storage device according to the embodiment.

[0015] Figure 2 (A) of is an exploded perspective view of the electrode group. Figure 2 (B) of is a top view of the electrode group joined with the first current collector plate.

[0016] Figure 3 (A) to Figure 3 (C) of is a diagram showing the joining process of the current collector and the current collector plate.

[0017] Figure 4 (A) to Figure 4 (L) of is a diagram for explaining the intensity adjustment of the laser. DETAILED DESCRIPTION OF THE INVENTION

[0018] Hereinafter, the present disclosure will be described with reference to the drawings based on preferred embodiments. The embodiments are illustrative and do not limit the present disclosure, and all features or combinations thereof described in the embodiments do not necessarily represent the essential content of the present disclosure. The same or equivalent constituent elements, components, and processes shown in the respective drawings are denoted by the same reference numerals, and repeated descriptions are appropriately omitted. In addition, the scales or shapes of the respective parts shown in the respective drawings are set for convenience of explanation, and are not to be construed in a limiting sense unless otherwise specified. Further, when terms such as "first" and "second" are used in the present specification or claims, they do not indicate any order or importance unless otherwise specified, but are used to distinguish one configuration from another. In addition, in the respective drawings, a part of the components that are not important in explaining the embodiments is omitted from being shown.

[0019] Figure 1 is a cross-sectional view of the power storage device 1 according to the embodiment. Figure 2 (A) of is an exploded perspective view of the electrode group 2. Figure 2 (B) of is a top view of the electrode group 2 joined with the first current collector plate 20. It should be noted that Figure 2 in (A) of, the division of the current collector 12 and the electrode active material layer 14 is omitted.

[0020] The power storage device 1 is, for example, a rechargeable secondary battery such as a lithium-ion battery, a nickel-metal hydride battery, or a nickel-cadmium battery, or a capacitor such as an electric double layer capacitor. The power storage device 1 has a structure in which an electrode group 2, an electrolyte (not shown), a first current collector plate 20, and a second current collector plate 22 are housed in an outer can 4. As an example, the electrode group 2 has a cylindrical shape and has a wound structure in which a strip-shaped first electrode plate 6 and a strip-shaped second electrode plate 8 are laminated with a strip-shaped spacer 10 interposed therebetween and wound in a spiral shape. In the present embodiment, the first electrode plate 6 is a positive electrode plate and the second electrode plate 8 is a negative electrode plate. Alternatively, the first electrode plate 6 may be a negative electrode plate and the second electrode plate 8 may be a positive electrode plate. The spacer 10 is, for example, made of a microporous membrane made of a polypropylene resin or the like.

[0021] The first electrode plate 6 and the second electrode plate 8 each have a current collector 12 and an electrode active material layer 14 laminated on the current collector 12. In a typical lithium-ion secondary battery, the current collector 12 of the positive electrode is made of aluminum foil or the like, and the current collector 12 of the negative electrode is made of copper foil or the like. The electrode active material layer 14 can also be formed by coating an electrode mixture on the surface of the current collector 12 using a known coating device and drying and rolling. The electrode mixture is obtained by kneading materials such as an electrode active material, a binder material, and a conductive material in a dispersion medium to uniformly disperse them. In a typical lithium-ion secondary battery, the electrode active material of the positive electrode is lithium cobaltate, lithium iron phosphate, or the like, and the electrode active material of the negative electrode is graphite or the like.

[0022] The first electrode plate 6 and the second electrode plate 8 each have an exposed portion 12a of the current collector 12 at an end in the width direction A. The width direction A is a direction intersecting the length direction of the strip. The exposed portion 12a of the first electrode plate 6 and the exposed portion 12a of the second electrode plate 8 protrude in opposite directions from each other in the width direction A. The exposed portion 12a is a portion of the current collector 12 that is not covered by the electrode active material layer 14.

[0023] As described above, the electrode group 2 has a structure in which the first electrode plate 6 and the second electrode plate 8 are wound. Therefore, a plurality of ends of the current collector 12 in the width direction A, that is, the exposed portions 12a, are arranged in the radial direction B of the electrode group 2. That is, the electrode group 2 has a laminated structure of the exposed portions 12a. Alternatively, the electrode group 2 may have a structure in which a plurality of single-piece first electrode plates 6 and single-piece second electrode plates 8 are laminated with a spacer 10 interposed therebetween.

[0024] As an example, the electrode group 2 has a first bonding region 46 and a second bonding region 48 where a plurality of exposed portions 12a arranged in the radial direction B are bent in the radial direction B. The first bonding region 46 and the second bonding region 48 are located on opposite sides in the width direction A. The plurality of exposed portions 12a included in the first bonding region 46 are the exposed portions 12a of the current collector 12 provided in the first electrode plate 6. The plurality of exposed portions 12a included in the second bonding region 48 are the exposed portions 12a of the current collector 12 provided in the second electrode plate 8.

[0025] For example, each exposed portion 12a is bent toward the winding center C of the electrode group 2, that is, toward the inside in the radial direction B. The winding center C is, for example, the geometric center of the outer shape of the electrode group 2 as viewed from the width direction A, in other words, the geometric center of the projected shape of the electrode group 2 in the width direction A. At the winding center C, a cylindrical space extending in the width direction A extends. Therefore, there is no current collector 12 at the winding center C. In addition, in the electrode group 2 as an example, the plurality of first bonding regions 46 and the plurality of second bonding regions 48 are respectively arranged at a predetermined interval in the circumferential direction of the electrode group 2. In the present embodiment, the four first bonding regions 46 are arranged at an interval of 90° in the circumferential direction. In addition, the four second bonding regions 48 are arranged at an interval of 90° in the circumferential direction.

[0026] The first current collector plate 20 and the second current collector plate 22 are arranged so as to sandwich the electrode group 2 in the width direction A. The first current collector plate 20 is arranged on the side of the first bonding region 46. The second current collector plate 22 is arranged on the side of the second bonding region 48. The thickness of the first current collector plate 20 and the second current collector plate 22, for example, the average value of the thickness at any 10 points, that is, the average thickness is, as an example, 0.1 mm or more and 0.8 mm or less.

[0027] The first current collector plate 20 is made of, for example, aluminum or the like. The plurality of exposed portions 12a bent at the first bonding region 46 are in surface contact with the first current collector plate 20. Each exposed portion 12a is bent so that the contact area between each exposed portion 12a and the first current collector plate 20 increases. Moreover, laser welding or the like is performed at the position where the first bonding region 46 and the first current collector plate 20 overlap. Thus, the exposed portions 12a of each winding layer and the first current collector plate 20 are joined to each other.

[0028] The second current collector plate 22 is made of, for example, iron with nickel plating or the like. The plurality of exposed portions 12a bent at the second bonding region 48 are in surface contact with the second current collector plate 22. Each exposed portion 12a is bent so that the contact area between each exposed portion 12a and the second current collector plate 22 increases. And, laser welding or the like is performed at the position where the second bonding region 48 and the second current collector plate 22 overlap. Thus, the exposed portions 12a of each winding layer and the second current collector plate 22 are joined to each other.

[0029] The electrode group 2 to which the first current collector plate 20 and the second current collector plate 22 are joined, together with the electrolyte, is housed in a bottomed cylindrical outer can 4. The outer can 4 is made of, for example, copper, nickel, iron, aluminum, or an alloy thereof. The second current collector plate 22 is joined to the inner bottom surface of the outer can 4 by welding or the like. The first current collector plate 20 is joined to a sealing plate 26 made of the same metal as the outer can 4 by welding or the like. The sealing plate 26 is inserted into the opening of the outer can 4 via an insulating gasket 24. Thus, the electrode group 2 and the electrolyte are sealed inside the outer can 4.

[0030] Next, a method for manufacturing the power storage device 1 will be described. Figure 3 of (A) to Figure 3 (C) of is a diagram showing the joining process of the current collector 12 and the current collector plate. First, as Figure 2 shown in (A) of, strip-shaped first electrode plates 6, second electrode plates 8, and spacers 10 are prepared respectively. Then, the spacers 10, the first electrode plates 6, the spacers 10, and the second electrode plates 8 are laminated in this order. The obtained laminate is wound in a spiral shape to form a wound-type electrode group 2.

[0031] Next, the electrode group 2 is set in a processing device (not shown). Then, by the processing device, the end portion of the current collector 12 provided in the first electrode plate 6 is bent in the radial direction B. Thus, a first joining region 46 including a plurality of exposed portions 12a bent in the radial direction B is formed. Thereafter, the first current collector plate 20 is pressed against the first joining region 46. And, by laser welding, the exposed portions 12a arranged in plurality in the first joining region 46 and the first current collector plate 20 are joined.

[0032] Specifically, as Figure 3 shown in (A) of, in a state where the plurality of exposed portions 12a are in contact with the first surface 21a of the first current collector plate 20, a laser L is irradiated to the second surface 21b of the first current collector plate 20 on the side opposite to the first surface 21a. The laser L is irradiated to one end of a scanning region 58 (refer to Figure 2 (B) of) in the first current collector plate 20. The scanning region 58 is a region that overlaps the first joining region 46 in the width direction A. Therefore, the scanning region 58 overlaps the plurality of exposed portions 12a arranged in plurality and extends along the arrangement direction of the exposed portions 12a, that is, along the radial direction B of the electrode group 2. In the present embodiment, four scanning regions 58 extend radially from the winding center C. Each scanning region 58 is arranged so as not to overlap the winding center C. Therefore, both ends of each scanning region 58 are offset in the same direction with respect to the winding center C in the radial direction of the electrode group 2.

[0033] By irradiating the first current collector plate 20 with the laser beam L, a molten portion 54 (molten pool) is formed. At positions where the current collector 12 is absent, the molten portion 54 is substantially composed only of the melt of the first current collector plate 20, and at positions where the current collector 12 is present, the molten portion 54 is composed of the melt of the first current collector plate 20 and the melt of the current collector 12. And, as shown in (B) of Figure 3 and Figure 3 (C) of, the scanning region 58 is scanned by the laser beam L in the arrangement direction of the exposed portions 12a. The traveling direction of the laser beam L may be a direction from the center side of the electrode group 2 toward the outside, or a direction from the outside of the electrode group 2 toward the center side. The scanning region 58 is scanned by the laser beam L, so that the molten portion 54 moves within the scanning region 58, and the joint portions 52 between the respective exposed portions 12a and the first current collector plate 20 are formed. As a result, the respective exposed portions 12a are joined to the first surface 21a of the first current collector plate 20.

[0034] After scanning the laser beam L over all the scanning regions 58, the joining of the first current collector plate 20 to the electrode group 2 is completed. Next, the end portions of the current collectors 12 provided on the second electrode plate 8 are bent by a processing device. Thereby, a second joint region 48 including a plurality of exposed portions 12a bent in the radial direction B is formed. Thereafter, the second current collector plate 22 is pressed against the second joint region 48. And, by the same processing as in the case of joining the first current collector plate 20 to the electrode group 2, the plurality of exposed portions 12a arranged in the second joint region 48 and the second current collector plate 22 are joined by laser welding. As a result, the respective exposed portions 12a are joined to the first surface 21a of the second current collector plate 22.

[0035] The electrode group 2 to which the first current collector plate 20 and the second current collector plate 22 are joined is housed together with the electrolytic solution in the exterior can 4. In addition, processes such as joining the second current collector plate 22 to the exterior can 4, joining the first current collector plate 20 to the sealing plate 26, and fitting the sealing plate 26 into the opening of the exterior can 4 are performed, and the power storage device 1 is obtained. In addition, the processing order of joining of each part, housing in the exterior can 4, fitting of the sealing plate 26, etc. can be appropriately changed. For example, in the case where a liquid injection port is provided in the sealing plate 26 or the like, the electrolytic solution may be injected into the exterior can 4 after the sealing plate 26 is fitted into the opening portion of the exterior can 4. In addition, it may be that the first joint region 46 and the second joint region 48 are first formed, then the first current collector plate 20 and the second current collector plate 22 are pressed against the electrode group 2, and thereafter, the laser beam L is irradiated to the first current collector plate 20 and the second current collector plate 22.

[0036] The inventors of the present invention have repeatedly and deeply studied the bonding process between the current collector 12 and the current collecting plate, and finally found that laser welding may cause a situation where the quality of the power storage device 1 is reduced. That is, the molten part 54 expands due to heat. In addition, in the area where the laser L has been irradiated before, the molten part 54 cools and shrinks. Therefore, fluctuations may occur in the first current collecting plate 20. In addition, due to the expansion of the molten part 54, the exposed part 12a in contact with the molten part 54 is pressed. The pressed exposed part 12a approaches the adjacent exposed part 12a. In this state, when the melt drops from the molten part 54 due to fluctuations in the first current collecting plate 20, as shown in Figure 3 (B) of, it is possible to form a bridge part 56 of the melt between two exposed parts 12a that are close to each other.

[0037] Then, when the irradiation position of the laser L moves and the molten part 54 cools, the exposed part 12a pressed by the molten part 54 is pulled back to the side of the first current collecting plate 20, and the two exposed parts 12a connected by the bridge part 56 are separated. As a result, as shown in Figure 3 (C) of, the bridge part 56 is cut off, and a part of the melt may remain on the surface of the exposed part 12a on the side farther from the first current collecting plate 20 as a metal foreign object 50. The metal foreign object 50 is composed of at least one metal of the metal constituting the current collector 12 and the metal constituting the current collecting plate. As an example, the metal foreign object 50 attached to the exposed part 12a on the side of the first electrode plate 6 is composed of at least one of aluminum and its alloys. The metal foreign object 50 attached to the exposed part 12a on the side of the second electrode plate 8 is composed of at least one of iron, nickel, copper, and their alloys.

[0038] The metal foreign object 50 may be peeled off from the exposed part 12a due to vibrations generated during the handling of the power storage device 1 or the flow of the electrolytic solution during liquid injection. The peeled metal foreign object 50 may dissolve in the electrolytic solution and enter the electrode group 2. And metal may be deposited on the electrode plate. When the deposited metal penetrates the spacer 10, a short circuit may occur. Therefore, it is desired to strongly suppress the attachment of the metal foreign object 50 to the exposed part 12a.

[0039] Therefore, in the present embodiment, in the bonding process between the current collector 12 and the current collecting plate, scanning with a laser L accompanied by a temporary reduction in strength is performed. Figure 4 (A) to Figure 4 (L) of are diagrams for explaining the intensity adjustment of the laser L. Figure 4 (A) of, Figure 4 (D) of, Figure 4 (G) of, and Figure 4 (J) of show the cross sections of the exposed part 12a and the current collecting plate. Figure 4 (B) of shows Figure 4 the second surface 21b of the current collecting plate shown in (A) of,Figure 4 The diagram (C) of Figure 4 shows the first surface 21a of the current collector plate shown in (A) of Figure 4 The diagram (E) of Figure 4 shows the second surface 21b of the current collector plate shown in (D) of Figure 4 The diagram (F) of Figure 4 shows the first surface 21a of the current collector plate shown in (D) of Figure 4 The diagram (H) of Figure 4 shows the second surface 21b of the current collector plate shown in (G) of Figure 4 The diagram (I) of Figure 4 shows the first surface 21a of the current collector plate shown in (G) of Figure 4 The diagram (K) of Figure 4 shows the second surface 21b of the current collector plate shown in (J) of Figure 4 The diagram (L) of Figure 4 shows the first surface 21a of the current collector plate shown in (J) of . In addition, in Figure 4 from (A) to Figure 4 in (L) of , the illustration of the joint portion 52 is omitted. In addition, only a part of the current collector plate is illustrated.

[0040] First, as shown in (A) to Figure 4 in (C) of Figure 4 , the laser L of the first intensity irradiates one end of the scanning region 58 of the second surface 21b and starts scanning in the arrangement direction of the exposed portion 12a. When the laser L of the first intensity is irradiated, a molten portion 54 is formed from the second surface 21b to the first surface 21a. Next, as shown in (D) to Figure 4 in (F) of Figure 4 , during the scanning of the laser L, the intensity of the laser L temporarily drops to a second intensity lower than the first intensity. For example, the output of a laser device (not shown) is temporarily reduced so that the laser L changes from the first intensity to the second intensity. When the laser L of the second intensity is irradiated, a molten portion 54 that does not reach the first surface 21a is formed. The first intensity and the second intensity of the laser L can be appropriately set based on the experiments or simulations of the designer according to the thickness of the current collector plate, the composition of the current collector plate or the current collector 12, the scanning speed of the laser L, etc.

[0041] Next, as shown in (G) to Figure 4 in (I) of Figure 4 , the intensity of the laser L is increased to the first intensity again. Therefore, a molten portion 54 is formed from the second surface 21b to the first surface 21a. And, as shown in (J) to Figure 4 in (L) of Figure 4As shown in (L), when the laser L of the first intensity reaches the other end of the scanning area 58, the irradiation of the laser L is stopped. In addition, the intensity of the laser L can be increased from the second intensity to an intensity different from the first intensity and capable of forming the molten part 54 with a depth reaching the first surface 21a.

[0042] When the laser L of the first intensity is irradiated, the molten part 54 with a depth reaching the first surface 21a is formed. Therefore, the molten marks 60 (flanges) are formed on both the second surface 21b and the first surface 21a. In addition, at the position where the exposed part 12a is in contact with the first surface 21a, the joint part 52 between the exposed part 12a and the current collector plate is formed together with the molten mark 60. On the other hand, when the laser L of the second intensity is irradiated, the molten part 54 with a depth not reaching the first surface 21a is formed. Therefore, the molten mark 60 is only formed on the second surface 21b, and the non-molten part 62 is formed on the second surface 21b.

[0043] Therefore, in the scanning area 58 of the second surface 21b, the continuous molten marks 60 are formed from one end to the other end. On the other hand, in the scanning area 58 of the first surface 21a, a plurality of molten marks 60 and the non-molten parts 62 located between the adjacent molten marks 60 are formed. That is, the molten marks 60 are formed intermittently. The plurality of molten marks 60 and the non-molten parts 62 are arranged in the scanning direction of the laser L or the arrangement direction of the current collector 12. The molten mark 60 formed on the first surface 21a is in a long strip shape in which the dimension (length) in the scanning direction of the laser L or the arrangement direction of the exposed part 12a is larger than the dimension (width) in the direction orthogonal to the scanning direction or the arrangement direction. For example, the length of the molten mark 60 is more than twice the width. In the first surface 21a, the molten mark 60 is segmented by the non-molten part 62, so the number of the molten marks 60 on the second surface 21b is less than the number of the molten marks 60 on the first surface 21a.

[0044] During the continuous irradiation of the laser L, the expansion amount of the molten part 54 gradually increases. When the expansion amount of the molten part 54 increases, the displacement amount of the exposed part 12a increases. As a result, the metal foreign matters 50 attached to the exposed part 12a increase, and each metal foreign matter 50 may become larger. In contrast, the manufacturing method of the energy storage device 1 of the present embodiment irradiates the laser L from the second surface 21b side in a state where a plurality of exposed parts 12a are in contact with the first surface 21a of the current collector plate, and by scanning with the laser L accompanied by a temporary reduction in intensity, the molten marks 60 and the non-molten parts 62 are alternately formed on the first surface 21a.

[0045] Thus, by forming the non-molten portion 62 within the scanning region 58 of the first surface 21a, the amount of expansion of the molten portion 54 can be reduced. Thereby, during the welding of the exposed portion 12a after the formation of the non-molten portion 62 to the current collector plate, it is possible to suppress the excessive expansion and contraction of the current collector plate. In addition, compared to the molten portion 54 when the molten mark 60 is formed, the depth of the molten portion 54 when the non-molten portion 62 is formed is shallower and the temperature is lower. Therefore, the expansion and contraction of this molten portion 54 are small. As a result, the attachment of the metal foreign matter 50 to the exposed portion 12a can be suppressed, and the occurrence of a short circuit caused by the metal foreign matter 50 can be suppressed. Therefore, the quality improvement of the power storage device 1 can be achieved.

[0046] Preferably, the laser L is a CW (Continuous Wave) laser. When the laser L is a pulsed laser, the irradiation of the laser L is repeatedly turned on and off. Therefore, when it is desired to form the molten portion 54 with the same depth at the same scanning speed using the pulsed laser and the CW laser respectively, the pulsed laser needs to have a higher power density than the CW laser. Therefore, compared to the case of the CW laser, when the pulsed laser is irradiated, the temperature of the molten portion 54 is more likely to rise, and thus the expansion and contraction of the molten portion 54 are also more likely to become larger. Therefore, the metal foreign matter 50 is likely to adhere to the exposed portion 12a. In contrast, by setting the laser L as the CW laser, the attachment of the metal foreign matter 50 to the exposed portion 12a can be suppressed, and the quality improvement of the power storage device 1 can be achieved.

[0047] In Figure 4 of (H) and Figure 4 In the second surface 21b shown in (K) of, the width of the molten mark 60 becomes thinner by the irradiation of the laser L with the second intensity. However, the shape of the molten mark 60 in the second surface 21b is not particularly limited, and a molten mark 60 with the same width as in the case of the first intensity can also be formed when the laser L has the second intensity. In addition, when the intensity of the laser L is set to the second intensity, a non-molten portion 62 can also be formed in the second surface 21b. That is, the second intensity can also be an intensity at which no molten mark 60 is formed in the second surface 21b. For example, the second intensity can also be 0, that is, the laser L is not irradiated.

[0048] Among them, preferably, a melting mark 60 continuous from one end to the other end of the scanning area 58 is formed on the second surface 21b. When the non-molten part 62 is formed on the second surface 21b side, compared with the case where the melting marks 60 are continuous on the second surface 21b side, the power of the laser L necessary for reforming the molten part 54 reaching the first surface 21a may be insufficient at the first intensity. At this time, the intensity of the laser is switched from the second intensity to a third intensity higher than the first intensity to form the molten part 54, and thereafter there is a need to switch from the third intensity to the first intensity. As a result, the control of the laser L may become complicated. In contrast, by making the melting marks 60 continuous on the second surface 21b, the complication of the control of the laser L can be suppressed.

[0049] In Figure 4 In the first surface 21a shown in (L) of, only one non-molten part 62 is formed within one scanning area 58. However, the number of non-molten parts 62 is not particularly limited and may be one or two or more. Among them, it is preferable to form a plurality of non-molten parts 62 within one scanning area 58. Thereby, the length of each melting mark 60 is shortened, and the growth of the molten part 54 can be further suppressed. Therefore, the attachment of the metal foreign matter 50 to the exposed part 12a can be further suppressed, and the quality improvement of the power storage device 1 can be achieved.

[0050] In addition, the timing of raising and lowering the intensity of the laser L can be appropriately set according to the experiments or simulations of the designer. The length or configuration of the melting marks 60 and the non-molten parts 62, the area ratio between the melting marks 60 and the non-molten parts 62, etc. are also appropriately adjusted in such a manner that the resistance of the power storage device 1 or the bonding strength between the electrode group 2 and the current collector plate can maintain a desired value when the non-molten part 62 is formed on the first surface 21a.

[0051] Through the bonding of the exposed part 12a and the current collector plate, it was finally discovered through in-depth research by the inventors that the metal foreign matter 50 may adhere to the exposed part 12a, the metal foreign matter 50 may peel off from the exposed part 12a during the manufacture or use of the power storage device 1, and the peeled metal foreign matter 50 may cause a short circuit. This cannot be understood as the common knowledge of those skilled in the art. Since those skilled in the art did not recognize these situations, it was common technical knowledge for those skilled in the art to give priority to reducing the resistance of the power storage device 1 or increasing the bonding strength between the electrode group 2 and the current collector plate and not to form the non-molten part 62 in the scanning area 58 of the first surface 21a.

[0052] In the present embodiment, by scanning with the laser L accompanied by a temporary reduction in strength, a non-molten portion 62 is formed within the scanning region 58 of the first surface 21a. However, the method for forming the non-molten portion 62 is not particularly limited. For example, the non-molten portion 62 can be formed even if the scanning speed of the laser L is temporarily increased. In addition, even if the laser head is temporarily moved away from or closer to the current collector plate to shift the focus of the laser L, the non-molten portion 62 can be formed. Further, even if the intensity of the laser L is set to be constant and only the thickness of the current collector plate is increased in the region where the non-molten portion 62 is to be formed, the non-molten portion 62 can be formed.

[0053] As described above, the embodiments of the present disclosure have been described in detail. The foregoing embodiments merely show specific examples when implementing the present disclosure. The content of the embodiments does not limit the technical scope of the present disclosure. Within the scope not departing from the idea of the invention defined in the claims, various design changes such as changes, additions, and deletions of components can be made. The new embodiments with design changes have the effects of both the combined embodiments and the variations. In the foregoing embodiments, for the content that allows such design changes, expressions such as "in the present embodiment" and "in this embodiment" are given for emphasis, and design changes are allowed even for the content without such expressions. In addition, any combination of the components included in each embodiment is also effective as a solution of the present disclosure. The hatching marked on the cross-section of the drawings does not limit the material of the object marked with hatching.

[0054] The embodiments can also be determined by the items described below.

[0055] [First item]

[0056] A method for manufacturing an electrical storage device (1), comprising:

[0057] Preparing an electrode group (2) which is an electrode group (2) having a current collector (12) with electrode active material layers (14) laminated thereon, and having a structure in which a plurality of exposed portions (12a) in the current collector (12) that are not covered by the electrode active material layers (14) are arranged,

[0058] Bringing the plurality of arranged exposed portions (12a) into contact with the first surface (21a) of the current collector plate (20, 22), and irradiating the laser (L) onto the second surface (21b) of the current collector plate (20, 22) opposite to the first surface (21a),

[0059] Scanning the scanning region (58) of the current collector plate (20, 22) that overlaps with the plurality of arranged exposed portions (12a) and extends in the arrangement direction of the exposed portions (12a) with the laser (L) in the arrangement direction, and joining the plurality of exposed portions (12a) to the first surface (21a),

[0060] In this joining, in the first surface (21a), a plurality of melting marks (60) are formed, where the dimension in the scanning direction of the laser (L) is larger than the dimension in the direction orthogonal to the scanning direction, and non-melting portions (62) are located between the adjacent melting marks (60).

[0061] [Second item]

[0062] The manufacturing method of the power storage device (1) as described in the first item,

[0063] The laser (L) is a CW laser.

[0064] [Third item]

[0065] The manufacturing method of the power storage device (1) as described in the first item or the second item includes:

[0066] Forming melting marks (60) that are continuous from one end to the other end of the scanning area (58) in the second surface (21b).

[0067] [Fourth item]

[0068] The manufacturing method of the power storage device (1) as described in any one of the first item to the third item includes:

[0069] Forming a plurality of non-melting portions (62).

[0070] [Fifth item]

[0071] A power storage device (1) includes:

[0072] An electrode group (2) having a current collector (12) with electrode active material layers (14) laminated thereon, and

[0073] Current collector plates (20, 22) joined to the current collector (12);

[0074] The electrode group (2) has a structure in which a plurality of exposed portions (12a) in the current collector (12) that are not covered by the electrode active material layers (14) are arranged, and the plurality of arranged exposed portions (12a) are joined to the first surface (21a) of the current collector plates (20, 22).

[0075] In the first surface (21a), in a region (58) that overlaps with the plurality of arranged exposed portions (12a) and extends in the arrangement direction of the exposed portions (12a), there are a plurality of melting marks (60) where the dimension in the arrangement direction is larger than the dimension in the direction orthogonal to the arrangement direction, and non-melting portions (62) located between the adjacent melting marks (60).

[0076] Industrial availability

[0077] The present disclosure can be used in a method for manufacturing an electrical energy storage device and an electrical energy storage device.

[0078] Description of reference numerals

[0079] 1 Electrical energy storage device, 2 Electrode group, 12 Current collector, 12a Exposed portion, 14 Electrode active material layer, 20 First current collector plate, 22 Second current collector plate, 21a First surface, 21b Second surface, 54 Fused portion, 58 Scanning area, 60 Fused mark, 62 Non-fused portion, L Laser.

Claims

1. A method for manufacturing an electric storage device, comprising: Preparing an electrode assembly, which is an electrode assembly having a current collector with electrode active material layers laminated thereon, and having a structure in which a plurality of exposed portions of the current collector that are not covered by the electrode active material layers are arranged; Bringing the plurality of arranged exposed portions into contact with a first surface of a current collector plate, and irradiating a second surface of the current collector plate opposite to the first surface with a laser; Scanning, with the laser, a scanning region of the current collector plate that overlaps the plurality of arranged exposed portions and extends in the arrangement direction of the exposed portions, and joining the plurality of exposed portions to the first surface; In this joining, a plurality of melting marks having a dimension in the scanning direction of the laser larger than a dimension in a direction orthogonal to the scanning direction, and non-melting portions located between adjacent ones of the melting marks are formed on the first surface.

2. The method for manufacturing an electric storage device according to claim 1, wherein the laser is a CW laser.

3. The method for manufacturing an electric storage device according to claim 1 or 2, comprising: Forming the melting marks that are continuous from one end to the other end of the scanning region on the second surface.

4. The method for manufacturing an electric storage device according to claim 1 or 2, comprising: Forming a plurality of the non-melting portions.

5. An electric storage device, comprising: an electrode assembly having a current collector with electrode active material layers laminated thereon, and a current collector plate joined to the current collector; the electrode assembly has a structure in which a plurality of exposed portions of the current collector that are not covered by the electrode active material layers are arranged, and the plurality of arranged exposed portions are joined to a first surface of the current collector plate, the first surface has, in a region that overlaps the plurality of arranged exposed portions and extends in the arrangement direction of the exposed portions, a plurality of melting marks having a dimension in the arrangement direction larger than a dimension in a direction orthogonal to the arrangement direction, and non-melting portions located between adjacent ones of the melting marks.

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