Energy Storage Devices

Abstract

To provide a power storage device capable of inhibiting occurrence of a minute short circuit in the vicinity of a reference position in a flat wound electrode body.SOLUTION: A power storage device 1 includes a flat wound electrode body 30, a case 10, and a positive electrode terminal 80 ultrasonically welded to a positive electrode current collecting part 62 of the electrode body 30. A surface-welded portion 71 of a welded portion 70 formed on a laminated current collecting part 63 of the positive current collecting part 62 has an outer periphery including an inner side 72, an outer side 73, a closer side 74 and a far side 75. An outside close endpoint 73a of the outer side 73 is positioned on one side EH1 toward a reference position SP in an electrode widthwise direction EH with respect to an inside close endpoint 72a of the inner side 72, and the closer side 74 forms a straight line or a line passing through a region farther from the reference position SP than the straight line.SELECTED DRAWING: Figure 5

Description

[Technical field]

[0001] The present invention relates to an electricity storage device including a flat wound electrode assembly, a case that houses the electrode assembly, and a positive electrode terminal that is fixed to the case and joined to the positive electrode current collecting portion of the electrode assembly by ultrasonic welding. [Background technology]

[0002] It has been found that in a battery having a flat wound electrode body, a micro-short circuit is likely to occur at a specific portion of the electrode body. The specific portion is a portion near the position (hereinafter also referred to as the "reference position") of the nearest virtual intersection point, which is the closest to the surface welded portion of the welded portion with the positive terminal, among four virtual intersection points where the outer surface of the electrode body, a first virtual boundary surface virtually provided at the boundary between the electrode body main body portion and the positive electrode current collecting portion of the electrode body, and a pair of second virtual boundary surfaces virtually provided at the boundaries between the electrode flat portion of the electrode body and a pair of electrode R portions intersect with each other. For example, Patent Document 1 can be cited as a conventional technique that discloses a battery having a flat wound electrode body (see Figures 1 to 3 of Patent Document 1, etc.). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2021-089856 Summary of the Invention [Problem to be solved by the invention]

[0004] In this battery, a laminated current collector is formed by overlapping a part of the exposed positive electrode foil that constitutes the positive current collector of the electrode body in the thickness direction of the electrode body, and a positive terminal is ultrasonically welded to this laminated current collector. Specifically, an anvil of an ultrasonic welding machine is placed on one side of the positive current collector in the thickness direction of the electrode body via a positive terminal, while a horn of the ultrasonic welding machine is placed on the other side of the positive current collector in the thickness direction of the electrode body. Then, ultrasonic vibration is applied while pressing the horn against the positive current collector from the other side in the thickness direction of the electrode body toward one side (the anvil side, the positive terminal side). As a result, a laminated current collector is formed on the positive current collector, and the positive terminal is ultrasonically welded to the laminated current collector. Note that a weld mark is left on the part of the laminated current collector where the horn was pressed.

[0005] During this ultrasonic welding, the positive electrode current collector foil of the exposed part of the positive electrode foil, which was wound in a spiral shape with a gap between them, moves and deforms significantly when the horn is pressed against the positive electrode current collector. Specifically, a V-groove-shaped recess is formed in the positive electrode current collector, which extends in a tapered V shape from the periphery of the welded part with the positive electrode terminal toward the reference position and is recessed inward in the thickness direction of the electrode body. The V-groove-shaped recess has a narrow groove width and a rapidly increasing depth near the tip close to the reference position. Therefore, near the tip of this V-groove-shaped recess, the positive electrode current collector foil located at the outermost periphery is bent significantly inward in the thickness direction of the electrode body, and a large stress is applied to the separator between this positive electrode current collector foil and the corner of the outer end of the axial direction of the negative electrode plate located immediately inside it.

[0006] When the vibrations caused by ultrasonic welding are added to this, holes are formed in the parts of the separator where this large stress is applied, and a micro-short circuit may occur between the outermost positive electrode current collector foil and the corner of the outer edge of the negative electrode plate just inside it. In addition, burrs may occur on the outer edge of the negative electrode plate, and the above-mentioned stress may cause the burrs to penetrate the separator near the reference position (near the tip of the V-shaped groove-shaped recess), causing the above-mentioned micro-short circuit. For these reasons, micro-short circuits are likely to occur near the reference position of the electrode body (near the tip of the V-shaped groove-shaped recess).

[0007] The present invention has been made in consideration of the current situation, and provides an electricity storage device having a flat wound type electrode body, which can suppress the occurrence of micro-short circuits in the electrode body near the aforementioned reference position. [Means for solving the problem]

[0008] (1) One aspect of the present invention for solving the above problem is a positive electrode plate having a positive electrode main body portion in which a band-shaped positive electrode active material layer extending in the longitudinal direction is formed on a band-shaped positive electrode current collector foil extending in the longitudinal direction, and a band-shaped positive electrode foil exposed portion extending in the longitudinal direction along one edge in the width direction of the positive electrode current collector foil, the positive electrode foil exposed without the positive electrode active material layer, and a band-shaped negative electrode plate, which are wound flat around a winding axis via a pair of band-shaped separators. the positive electrode foil exposed portion of the positive electrode current collecting portion of the electrode body is spirally protruded from the electrode body main portion on one side in the axial direction along the winding axis; a case for accommodating the electrode body; and a flat wound electrode body having a positive electrode foil exposed portion of the positive electrode current collecting portion of the electrode body fixed to the case, the positive electrode foil exposed portion of the positive electrode current collecting portion of the electrode body being overlapped in the electrode body thickness direction of the flat electrode body. and tied together The laminated current collector is From the thickness direction of the electrode body and a positive electrode terminal joined by ultrasonic welding, wherein among four virtual intersections at which an outer surface of the electrode body, a first virtual boundary surface perpendicular to the axial direction and imaginarily provided at a boundary between the electrode body main body portion and the positive electrode current collecting portion of the electrode body, and a pair of second virtual boundary surfaces parallel to the axial direction and the electrode body thickness direction and imaginarily provided at boundaries between an electrode flat portion of the electrode body, where the positive electrode plate, the negative electrode plate, and the separator are overlapped in a flat plate shape, and a pair of electrode R portions, where the positive electrode plate, the negative electrode plate, and the separator are overlapped while being bent in a semi-cylindrical shape, are mutually intersected, the first virtual boundary surface being perpendicular to the axial direction and imaginaryly provided at a boundary between the electrode flat portion of the electrode body, where the positive electrode plate, the negative electrode plate, and the separator are overlapped in a flat plate shape, and a pair of electrode R portions, where the positive electrode plate, the negative electrode plate, and the separator are overlapped while being bent in a semi-cylindrical shape, are formed on the laminated current collecting portion by the ultrasonic welding. , extending in the electrode body width direction perpendicular to the axial direction and the electrode body thickness direction, When the position of the virtual intersection closest to the surface weld that appears on the outer surface of the laminated current collector is taken as the reference position, the surface weld is Telegraphthe outer peripheral shape having an inner side extending parallel to the inner side in the electrode body width direction, an outer side extending parallel to the inner side and located on one side of the inner side in the axial direction, a near side side connecting an inner near end point of the inner side that is closer to the reference position and an outer near end point of the outer side that is closer to the reference position, and a far side side connecting an inner far end point of the two inner end points farther from the reference position and an outer far end point of the two outer end points that is farther from the reference position, the outer near end point of the outer side being located on one side of the inner near end point of the inner side toward the reference position in the electrode body width direction, and the near side side forms a straight line connecting the inner near end point and the outer near end point, or forms a line passing through a region farther from the reference position than the straight line.

[0009] In the above-mentioned electricity storage device, among the welds formed on the laminated current collecting part of the positive current collecting part of the electrode body, the surface welds appearing on the outer surface of the laminated current collecting part have an outer peripheral shape having an inner side, an outer side, a near side side, and a far side side, and the outer near end point of the outer side is located on one side of the electrode body width direction from the winding axis toward the reference position relative to the inner near end point of the inner side, and the near side side forms a straight line or a line passing through an area farther from the reference position than the straight line. In an electrode body in which a weld including such a surface weld is formed, the inner side of the above-mentioned surface weld extends beyond the inner near end point to one side in the electrode body width direction, and the near side side is perpendicular to the inner side and the outer side, respectively, and compared to a case (described later as a comparative example) in which a virtual surface weld is provided on the electrode body, the change in the depth of the recess is gentler near the reference position (near the tip of the V-shaped groove recess), and the bending inward in the electrode body thickness direction of the positive current collecting foil located on the outermost periphery is gentler. Therefore, the above-mentioned damage to the separator near the reference position is less likely to occur, and the occurrence of a micro-short circuit near the reference position can be suppressed.

[0010] In addition, examples of the shape of the line when "the near side edge is a line that passes through an area farther from the reference position than the straight line connecting the inner near end point of the inner side and the outer near end point of the outer side" include a curve, a broken line made up of multiple straight lines connected together, and a line made up of multiple connected straight lines and curves. Examples of the "electricity storage device" include secondary batteries such as lithium ion secondary batteries, capacitors such as lithium ion capacitors, and all-solid-state batteries.

[0011] (2) In the electricity storage device according to (1), the electrode body may have a dimension of 10 mm or more in a thickness direction.

[0012] The larger the dimension of the electrode body in the thickness direction of the electrode body, the greater the device capacity of the electricity storage device can be. However, if the dimension of the electrode body in the thickness direction of the electrode body is 10 mm or more, when ultrasonically welding the positive terminal with a part of the positive current collector of the electrode body as a laminated current collector, the positive current collector (positive current collector foil of the exposed part of the positive current collector foil) is significantly deformed, so that the depth of the recess increases rapidly near the reference position of the electrode body (near the tip of the V-shaped groove recess), and the bending of the positive current collector foil at the outermost periphery toward the inside becomes large. Then, the above-mentioned micro-short circuit is easily generated. Therefore, it is particularly preferable to apply the present invention to an electricity storage device having a dimension in the thickness direction of the electrode body of 10 mm or more, in which such a micro-short circuit is easily generated. [Brief description of the drawings]

[0013] [Figure 1] FIG. 1 is a perspective view of a battery according to an embodiment. [Diagram 2] 1 is a cross-sectional view of a battery according to an embodiment of the present invention taken along the battery height direction and the battery thickness direction. [Diagram 3] 3 is a cross-sectional view taken along the line AA in FIG. 2, taken along the battery height direction and battery width direction of the battery according to the embodiment. [Figure 4] 3 is a cross-sectional view taken along the arrow BB in FIG. 2, taken along the battery height direction and battery width direction of the battery according to the embodiment. [Diagram 5] 3 is a partially enlarged plan view of a portion of an electrode body of a battery according to an embodiment, the portion including a reference position and a surface welded portion, as viewed in the thickness direction of the electrode body. FIG. [Figure 6] 3 is a partially enlarged cross-sectional view along the axial direction and the electrode body thickness direction of a portion including a reference position of an electrode body of a battery according to an embodiment. FIG. [Figure 7] 6 is a partially enlarged plan view of a portion of an electrode body of a battery according to a modified embodiment, the portion including a reference position and a surface welded portion, corresponding to FIG. 5, as viewed in the thickness direction of the electrode body. [Figure 8] 7 is a partially enlarged cross-sectional view along the axial direction and the electrode body thickness direction of a portion including a reference position, corresponding to FIG. 6, of an electrode body of a battery according to a comparative embodiment. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] (Embodiment) Hereinafter, an embodiment of the present invention will be described with reference to the drawings. Fig. 1 shows a perspective view of a battery (electricity storage device) 1 according to this embodiment, and Figs. 2 to 4 show cross-sectional views of the battery 1. In the following description, the battery height direction AH, battery lateral direction BH, and battery thickness direction CH of the battery 1, as well as the axial direction DH, electrode body width direction EH, and electrode body thickness direction FH of the electrode body 30 will be defined as the directions shown in Figs. 1 to 4. The battery 1 is a square (rectangular parallelepiped) sealed lithium ion secondary battery that is mounted on vehicles such as hybrid cars, plug-in hybrid cars, and electric cars.

[0015] The battery 1 is composed of a case 10, a flat wound electrode assembly 30 housed in the case 10, a positive electrode terminal 80 and a negative electrode terminal 90 each supported on a case upper portion 11 of the case 10, and the like. Inside the case 10, the electrode assembly 30 is covered by a bag-shaped insulating holder 5 made of an insulating film and opening to an upper side AH1 in the battery height direction AH. An electrolyte 3 is also housed inside the case 10, a part of which is impregnated in the electrode assembly 30, and the remainder is pooled on the case bottom portion 12 of the case 10.

[0016] The case 10 is a rectangular box made of metal (aluminum in this embodiment), and has a rectangular case upper part 11 located on the upper side AH1 in the battery height direction AH, a rectangular case bottom part 12 facing the upper part 11 and located on the lower side AH2 in the battery height direction AH, and four rectangular case sides (a pair of case long sides 13, 14 and a pair of case short sides 15, 16) connecting the upper part 11 and the lower side AH2. The case 10 is composed of a bottomed square cylindrical main body member 21 having a rectangular annular opening 21c on the upper side AH1, and a lid member 22 laser-welded to the main body member 21 over its entire circumference in a manner that closes the opening 21c. The lid member 22 is provided with a safety valve 25 that breaks and opens when the internal pressure of the case 10 exceeds the valve opening pressure. The lid member 22 is also provided with a liquid injection hole 22k that communicates between the inside and outside of the case 10, and is airtightly sealed with a disk-shaped sealing member 26 made of aluminum.

[0017] A positive terminal 80 composed of an internal terminal member 81, an external terminal member 82, and a terminal bolt 83 made of aluminum is fixed to the case upper portion 11 (lid member 22) of the case 10 in a state insulated from the case 10 via an internal insulating member 85 and an external insulating member 86 made of resin. The positive terminal 80 is joined to the positive current collector 62 of the electrode body 30 in the case 10 and is electrically connected thereto, while penetrating the case upper portion 11 to the outside of the case 10. A negative terminal 90 composed of an internal terminal member 91, an external terminal member 92, and a terminal bolt 93 made of copper is fixed to the case upper portion 11 in a state insulated from the case 10 via an internal insulating member 95 and an external insulating member 96 made of resin. The negative terminal 90 is joined to the negative current collector 64 of the electrode body 30 in the case 10 and is electrically connected thereto, while penetrating the case upper portion 11 to the outside of the case 10.

[0018] The positive electrode terminal 80 and the negative electrode terminal 90 have the same configuration, and therefore will be described together below. The internal terminal members 81, 91 of the positive electrode terminal 80 and the negative electrode terminal 90 are mainly disposed inside the case 10 and joined to the positive electrode current collector 62 or the negative electrode current collector 64 of the electrode body 30, while passing through the case upper portion 11 and extending to the outside of the case 10 and crimping-connected to the external terminal members 82, 92. Meanwhile, the external terminal members 82, 92 are disposed outside the case 10 and are crank-shaped (Z-shaped). The terminal bolts 83, 93 are also disposed outside the case 10. The terminal bolts 83, 93 are inserted from the lower side AH2 of the external terminal members 82, 92 to the external terminal member 82 ,92 and protrudes above the external terminal members 82, 92 to the upper side AH1.

[0019] The internal insulating members 85, 95 are mainly disposed inside the case 10, and insulate the internal terminal members 81, 91 of the positive electrode terminal 80 or the negative electrode terminal 90 from the case upper portion 11. On the other hand, the external insulating members 86, 96 are disposed outside the case 10, and insulate the external terminal members 82, 92 and terminal bolts 83, 93 of the positive electrode terminal 80 or the negative electrode terminal 90 from the case upper portion 11.

[0020] Next, the electrode body 30 will be described (see Figs. 1 to 4, as well as Figs. 5 and 6). The electrode body 30 is formed by stacking a strip-shaped positive electrode plate 31 and a strip-shaped negative electrode plate 41 with a pair of separators 51 interposed between them, each of which is a strip-shaped resin porous film, winding the resulting plate into a cylindrical shape around a winding axis DX, and then compressing the resulting plate into a flat shape. The dimensions of the flat electrode body 30 are 117 mm in the axial direction DH along the winding axis DX, 58 mm in the electrode body width direction EH, and 20 mm in the electrode body thickness direction FH (see Fig. 2). The electrode body 30 is accommodated in the case 10 in such a manner that the axial direction DH coincides with the battery transverse direction BH, the electrode body width direction EH coincides with the battery height direction AH, and the electrode body thickness direction FH coincides with the battery thickness direction CH.

[0021] The positive electrode plate 31 has a positive electrode current collector foil 32 made of a strip-shaped aluminum foil extending in the longitudinal direction GH (see Figs. 3 and 4). On a part of the width direction HH and on an area extending in the longitudinal direction GH of both main surfaces of the positive electrode current collector foil 32, a strip-shaped positive electrode active material layer 33 (see Fig. 6) extending in the longitudinal direction GH is formed. The positive electrode active material layer 33 is composed of positive electrode active material particles capable of absorbing and releasing lithium ions, conductive particles, and a binder. In the positive electrode plate 31, a strip-shaped portion having the positive electrode active material layer 33 on the positive electrode current collector foil 32 is the above-mentioned positive electrode main body portion 35. On the other hand, a strip-shaped portion extending in the longitudinal direction GH along an edge 32f on one side HH1 of the width direction HH of the positive electrode current collector foil 32 is a positive electrode foil exposed portion 36 in which the positive electrode active material layer 33 is not present and the positive electrode current collector foil 32 is exposed.

[0022] The negative electrode plate 41 has a negative electrode current collector foil 42 made of a band-shaped copper foil extending in the longitudinal direction JH (see Figs. 3 and 4). On a part of the width direction KH and on an area of ​​both main surfaces of the negative electrode current collector foil 42 that extends in the longitudinal direction JH, a band-shaped negative electrode active material layer 43 (see Fig. 6) extending in the longitudinal direction JH is formed. The negative electrode active material layer 43 is composed of negative electrode active material particles capable of absorbing and releasing lithium ions, a binder, and a thickener. In the negative electrode plate 41, a band-shaped portion having the negative electrode active material layer 43 on the negative electrode current collector foil 42 is a negative electrode main body portion 45. On the other hand, a band-shaped portion extending in the longitudinal direction JH along an edge 42f of one side KH1 of the negative electrode current collector foil 42 in the width direction KH is a negative electrode foil exposed portion 46 that does not have the negative electrode active material layer 43 and where the negative electrode current collector foil 42 is exposed.

[0023] In the electrode body 30, the central portion in the axial direction DH is an electrode body main body 61 in which the entire positive electrode main body 35 of the positive electrode plate 31 and a part of the negative electrode main body 45 of the negative electrode plate 41 face each other via a separator 51. Note that since the negative electrode main body 45 is wider than the positive electrode main body 35, both outer end portions of the negative electrode main body 45 in the axial direction DH do not face the positive electrode main body 35 and are not included in the electrode body main body 61.

[0024] In addition, the electrode assembly 30 has a positive current collector 62 in the axial direction DH that is located on one side DH1 of the electrode assembly main body 61 and is formed by the positive foil exposed portion 36 of the positive plate 31 protruding from the electrode assembly main body 61 to the one side DH1 of the axial direction DH in a spiral shape. The dimension of the positive current collector 62 in the axial direction DH is 8.5 mm. The positive current collector 62 is mainly composed of the positive foil exposed portion 36, but also includes the outer end 45a (see FIG. 6) of the negative plate 41 on the one side DH1 of the axial direction DH that does not face the positive main body 35, and the outer end 51a of the separator 51 on the one side DH1 of the axial direction DH that does not face the positive main body 35, in addition to the positive foil exposed portion 36.

[0025] In a part of the positive current collecting portion 62, specifically, in a central portion near one side EH1 in the width direction EH of the electrode body, the spiral positive foil exposed portion 36 overlaps in the thickness direction FH of the electrode body to form a laminated current collecting portion 63. An internal terminal member 81 of a positive terminal 80 is joined to this laminated current collecting portion 63 by ultrasonic welding. Of the welds 70 formed in this laminated current collecting portion 63, the portion that appears on the outer surface 63m of the laminated current collecting portion 63 is the above-mentioned surface welds 71. This surface welds 71 ​​will be described in detail later.

[0026] In addition, the portion of the electrode body 30 on the other side DH2 in the axial direction DH from the electrode body main body 61 is a negative current collector 64 in which the outer end (not shown) of the negative electrode main body 45 and the negative foil exposed portion 46 of the negative electrode plate 41 protrude in a spiral shape from the electrode body main body 61 to the other side DH2 in the axial direction DH. The dimension of this negative current collector 64 in the axial direction DH is 8.5 mm, similar to that of the positive current collector 62. The negative current collector 64 also includes the outer end 51b of the separator 51 on the other side DH2 in the axial direction DH that does not face the positive electrode main body 35. In a part of the negative electrode current collecting portion 64, specifically, in a central portion near one side EH1 in the width direction EH of the electrode body, the spiral negative electrode foil exposed portion 46 overlaps in the thickness direction FH of the electrode body to form a laminated current collecting portion 65. An internal terminal member 91 of the negative electrode terminal 90 is joined to the laminated current collecting portion 65 by ultrasonic welding.

[0027] The electrode body 30 also has an electrode flat portion 67 and a pair of electrode R portions 68. That is, the electrode flat portion 67 is a portion where the positive electrode plate 31, the negative electrode plate 41, and the separator 51 overlap in a flat plate shape. On the other hand, the electrode R portion 68 is a portion where the positive electrode plate 31, the negative electrode plate 41, and the separator 51 overlap while being bent into a semi-cylindrical shape.

[0028] Here, the above-mentioned "four virtual intersections", "closest virtual intersections" and "reference position" in the electrode body 30 will be explained. First, a first virtual boundary surface IM1 (shown by a dashed line in Figs. 3 to 6) perpendicular to the axial direction DH is virtually provided at the boundary between the electrode body main body 61 and the positive electrode current collecting portion 62 of the electrode body 30, and a pair of second virtual boundary surfaces IM2 (shown by a dashed line in Figs. 2 to 5) parallel to the axial direction DH and the electrode body thickness direction FH (perpendicular to the electrode body width direction EH) are virtually provided at the boundary between the electrode flat portion 67 and a pair of electrode R portions 68 of the electrode body 30. The four intersections where the outer surface 30m of the electrode body 30, the first virtual boundary surface IM1 and the pair of second virtual boundary surfaces IM2 intersect with each other are virtual intersections IP1, IP2, IP3 and IP4. Among these virtual intersections IP1 to IP4, the virtual intersection IP1 closest to the surface welded portion 71 of the welded portion 70 formed on the laminated current collecting portion 63 is the nearest virtual intersection IP1 (see FIGS. 2, 4 to 6). The position of this nearest virtual intersection IP1 is the reference position SP.

[0029] Next, the surface weld 71 will be described (see FIGS. 5 and 4). The surface weld 71 has an outer circumferential shape including an inner side 72, an outer side 73, a near side 74, and a far side 75. Specifically, the inner side 72 forms a straight line (having a length of 7 mm in this embodiment) extending parallel to the electrode body width direction EH. The outer edge 73 is a straight line extending parallel to the inner edge 72 (extending parallel to the electrode body width direction EH) and is located on one side DH1 in the axial direction DH of the inner edge 72 (10 mm in length in this embodiment).

[0030] Of the two outer end points 73a, 73b of the outer side 73, the outer near end point 73a (located on one side EH1 in the electrode body width direction EH) which is closer to the reference position SP is located on one side EH1 in the electrode body width direction EH (the side toward the reference position SP from the winding axis DX) than the inner near end point 72a (located on one side EH1 in the electrode body width direction EH) which is closer to the reference position SP of the two inner end points 72a, 72b of the inner side 72. In this embodiment, the outer near end point 73a of the outer side 73 is located 3 mm away from the inner near end point 72a of the inner side 72 on one side EH1 in the electrode body width direction EH. On the other hand, of the two outer end points 73a, 73b of the outer edge 73, the outer far end point 73b which is farther from the reference position SP (located on the other side EH2 in the electrode body width direction EH) and the inner far end point 72b of the two inner end points 72a, 72b of the inner edge 72 which is farther from the reference position SP (located on the other side EH2 in the electrode body width direction EH) are located at the same position in the electrode body width direction EH.

[0031] The near side 74 is a side that connects the inner near end point 72a of the inner side 72 and the outer near end point 73a of the outer side 73, and in this embodiment, this near side 74 forms a straight line. The far side edge 75 is an edge that connects the inner far end point 72b of the inner side edge 72 and the outer far end point 73b of the outer side edge 73, and this far side edge 75 forms a straight line (extending parallel to the axial direction DH) that is perpendicular to the inner side edge 72 and the outer side edge 73 (in this embodiment, the length is 4 mm).

[0032] Next, a method for manufacturing the battery 1 will be described. First, a positive electrode plate 31, a negative electrode plate 41, and a pair of separators 51 each having a strip shape are prepared, and these are stacked in the order of separator 51, negative electrode plate 41, separator 51, and positive electrode plate 31, and wound cylindrically around a winding axis line DX to form a cylindrical electrode body (not shown). Then, this cylindrical electrode body is pressed to form a flat electrode body 30 having an electrode flat portion 67 and a pair of electrode R portions 68.

[0033] Separately, a lid member 22, internal terminal members 81, 91, external terminal members 82, 92, terminal bolts 83, 93, internal insulating members 85, 95, and external insulating members 86, 96 are prepared. Then, a positive electrode terminal 80 consisting of an internal terminal member 81, an external terminal member 82, and a terminal bolt 83 is fixed to the lid member 22 via the internal insulating member 85 and the external insulating member 86, and a negative electrode terminal 90 consisting of an internal terminal member 91, an external terminal member 92, and a terminal bolt 93 is fixed to the lid member 22 via the internal insulating member 95 and the external insulating member 96.

[0034] Next, the positive terminal 80 fixed to the lid member 22 is joined to the positive current collecting portion 62 of the electrode body 30, and the negative terminal 90 fixed to the lid member 22 is joined to the negative current collecting portion 64 of the electrode body 30 by ultrasonic welding. Specifically, parts of the positive foil exposed portions 36 that form the positive current collecting portion 62 and are spirally wound with gaps between them are overlapped in the thickness direction FH of the electrode body to form a laminated current collecting portion 63, and an internal terminal member 81 of the positive terminal 80 is ultrasonically welded to this laminated current collecting portion 63.

[0035] In detail, an anvil (not shown) of an ultrasonic welding machine is arranged on one side FH1 of the positive current collecting part 62 in the electrode body thickness direction FH via an internal terminal member 81 of a positive terminal 80, while a horn (not shown) of the ultrasonic welding machine is arranged on the other side FH2 of the positive current collecting part 62 in the electrode body thickness direction FH. The horn is pressed against the positive current collecting part 62 from the other side FH2 of the electrode body thickness direction FH toward one side FH1 (the anvil side, the internal terminal member 81 side of the positive terminal 80) and ultrasonic vibration is applied. As a result, a laminated current collecting part 63 is formed on the positive current collecting part 62, and the internal terminal member 81 of the positive terminal 80 is ultrasonically welded to the laminated current collecting part 63, and a welded part 70 having a surface welded part 71 of an outer circumferential shape including an inner side 72, an outer side 73, a near side side 74, and a far side side 75 is formed on the laminated current collecting part 63. Similarly, the internal terminal member 91 of the negative electrode terminal 90 is ultrasonically welded to the negative electrode current collecting portion 64 of the electrode body 30 .

[0036] Here, a comparative embodiment of this embodiment will be described. In this comparative embodiment, the shape of the welded portion 970 including the surface welded portion 971 is different. That is, as shown in FIG. 5, where a part of the surface welded portion 971 is shown by a broken line, the surface welded portion 971 of the comparative embodiment has an inner side 972 that extends beyond the inner near end point 72a of the inner side 72 of the surface welded portion 71 of this embodiment to one side EH1 in the electrode body width direction EH, and has a peripheral shape (rectangular shape) in which the near side side 974 is perpendicular to the inner side 972 and the outer side 73. The outer side 73 and the far side 75 are the same as those of the embodiment. The shapes of the surface welded portions 71, 971 of the embodiment and the comparative embodiment can be changed by changing the shape of the horn of the ultrasonic welding machine.

[0037] In this comparative example (see also FIG. 8), when an ultrasonic welding horn is pressed against the positive current collecting portion 62, the positive current collecting foil 32 of the positive foil exposed portion 36 moves and deforms significantly. Then, a V-shaped groove-shaped recess 962v is formed in the positive current collecting portion 62, which extends in a tapered V shape from the periphery of the welded portion 970 with the internal terminal member 81 of the positive terminal 80 toward the reference position SP and is recessed into the inner side FH3 in the thickness direction FH of the electrode body. The V-shaped groove-shaped recess 962v has a narrow groove width and a rapidly increasing depth near the tip end close to the reference position SP.

[0038] For this reason, the V-shaped groove recess 962 v In the vicinity of the tip of the positive current collector foil 32A (see FIG. 8), the outermost positive current collector foil 32A (see FIG. 8) is largely bent toward the inside FH3 (downward in FIG. 8) in the electrode body thickness direction FH. In particular, since the dimension FL of the electrode body 30 in the electrode body thickness direction FH is 10 mm or more, the positive current collector part 62 is largely deformed, and the depth of the V-groove-shaped recess 962v increases rapidly near the tip of the V-groove-shaped recess 962v, and the outermost positive current collector foil 32A is largely bent toward the inside FH3. A large stress is applied to the outer end 51a of the separator 51 between the positive current collector foil 32A and the corner 45at of the outer end 45a of the negative plate 41A located immediately inside the positive current collector foil 32A.

[0039] When vibrations during ultrasonic welding are applied to this, holes are formed in the portions of the outer end 51a of the separator 51 where this large stress is applied, and the outermost positive current collector foil 32A comes into contact with the corner 45at of the outer end 45a of the negative plate 41A immediately inside (position indicated by arrow TR in FIG. 8), which may cause a micro-short circuit between them. Also, burrs may be generated on the outer end 45a of the negative plate 41, and the burrs may penetrate the outer end 51a of the separator 51 due to the above-mentioned stress near the reference position SP (near the tip of the V-groove recess 962v), causing the above-mentioned micro-short circuit.

[0040] In contrast, in this embodiment (see FIG. 6), when the ultrasonic welding horn is pressed against the positive current collector 62, a V-shaped groove recess 62v having a shape generally the same as the V-shaped groove recess 962v of the comparative embodiment is formed in the positive current collector 62. However, in the V-shaped groove recess 62v formed in this embodiment, the change in the depth of the recess is gentler in the vicinity of the reference position SP (near the tip of the V-shaped groove recess 62v) than in the V-shaped groove recess 962v of the comparative embodiment, and the bending of the positive current collector foil 32A located at the outermost periphery toward the inner side FH3 (downward in FIG. 6) is gentler. Therefore, the outer end 51a of the separator 51 described above is less likely to be damaged in the vicinity of the reference position SP, and it is possible to suppress the contact between the outermost positive current collector foil 32A and the corner 45at of the outer end 45a of the negative plate 41A located immediately inside it in the vicinity of the reference position SP, which causes a micro-short circuit.

[0041] Next, the electrode body 30 is wrapped in a bag-shaped insulating holder 5. Then, the main body member 21 is prepared, the electrode body 30 covered with the insulating holder 5 is inserted into the main body member 21, and the opening 21c of the main body member 21 is closed with the lid member 22. Then, the opening 21c of the main body member 21 and the periphery of the lid member 22 are laser-welded over the entire circumference to form the case 10. Next, the electrolyte 3 is poured into the case 10 through the injection hole 22k, and the electrolyte 3 is impregnated into the electrode body 30. Then, the injection hole 22k is covered from the outside with a sealing member 26, and the sealing member 26 is welded to the lid member 22 over the entire circumference to hermetically seal the gap between the sealing member 26 and the lid member 22. Next, a charging device (not shown) is connected to the battery 1, and the battery 1 is initially charged. Then, the initially charged battery 1 is left stationary for a predetermined time to age the battery 1. In this manner, the battery 1 is completed.

[0042] (Variations) Next, a modified embodiment of the embodiment will be described. Note that the description of the same parts as those of the embodiment will be omitted or simplified. In the surface weld 71 of the weld 70 in the battery 1 of the embodiment, the near side 74 forms a straight line connecting the inner near end point 72a of the inner side 72 and the outer near end point 73a of the outer side 73. In contrast, in the surface weld 171 of the weld 170 in the battery 100 of this modified embodiment, the near side 174 forms a curve connecting the inner near end point 72a of the inner side 72 and the outer near end point 73a of the outer side 73 (see FIG. 7).

[0043] Specifically, the surface weld 171 according to this modified embodiment has an outer peripheral shape including an inner side 72, an outer side 73, a near side 174, and a far side 75. Far side 75 On the other hand, near side 174 passes through an area farther from the reference position SP than near side 74 of the embodiment (shown by a dashed line in FIG. 7), and forms a curved shape that moves away from near side 74 of the embodiment toward the center of near side 174 (a curve that is convex in the direction moving away from the reference position SP).

[0044] In the battery 100 of this modified embodiment, the V-shaped groove recess 162v formed in the positive electrode current collector 62 by ultrasonic welding in the manufacturing process has a more gradual change in recess depth near the reference position SP (near the tip of the V-shaped groove recess 162v) compared to the V-shaped groove recess 62v of the embodiment, and the bending of the positive electrode current collector foil 32A located at the outermost periphery toward the inner side FH3 is more gradual. Therefore, the outer end 51a of the separator 51 described above is less likely to be damaged near the reference position SP, and the occurrence of a micro-short circuit near the reference position SP can be more effectively suppressed. Other parts similar to those of the embodiment have the same functions and effects as those of the embodiment.

[0045] Although the present invention has been described above with reference to the embodiments and modified forms, it goes without saying that the present invention is not limited to the embodiments and modified forms, and can be appropriately modified and applied without departing from the spirit of the present invention. [Explanation of symbols]

[0046] 1,100 Batteries (energy storage devices) 10 Cases 30 Electrode body 30m (Outer surface of electrode body) 31 Positive electrode plate 32,32A positive electrode current collector foil 32f edge 33 Positive electrode active material layer 35 Positive electrode body 36 Positive electrode foil exposed part 41,41A negative electrode plate 51 Separator 61 Electrode body part 62 Positive electrode current collector 63 (Positive electrode current collector) laminated current collector 63m (Outer surface of laminated collector) 67 Electrode flat part 68 Electrode R section 70,170 Welding 71,171 Surface welds 72 Inner Edge 72a Inner near end point (inner end point) 72b Inner far end point (inner end point) 73 Outer Edge 73a Outer near end point (outer end point) 73b Outer far end point (outer end point) 74,174 near side 75 far side 80 Positive terminal 90 Negative terminal DX winding axis line DH Axial direction DH1 (Axial direction) One side EH Electrode body width direction EH1 (One side in the electrode body width direction) FH Electrode body thickness direction GH Longitudinal direction (of positive electrode current collector foil) HH (Positive electrode current collector foil) Width direction HH1 (widthwise) one side IM1 First virtual boundary surface IM2 Second virtual boundary surface IP1 Nearest virtual intersection (virtual intersection) IP2,IP3,IP4 Virtual intersection SP reference position FL (electrode body thickness direction) dimension

Claims

1. a positive electrode main body portion in which a band-shaped positive electrode active material layer extending in the longitudinal direction is formed on a band-shaped positive electrode current collector foil extending in the longitudinal direction, a positive electrode plate having a band-shaped positive electrode foil exposed portion extending in the longitudinal direction along one edge in the width direction of the positive electrode current collector foil, the positive electrode foil exposed portion not having the positive electrode active material layer, and the positive electrode current collector foil exposed; and a band-shaped negative electrode plate are wound flat around a winding axis via a pair of band-shaped separators, an electrode body portion in which the positive electrode body portion of the positive electrode plate and the negative electrode plate face each other via the separator; and a positive electrode current collecting portion in which the positive electrode foil exposed portion protrudes in a spiral shape from the electrode body main body portion on one side in the axial direction along the winding axis. A flat wound electrode body; A case for accommodating the electrode assembly; a positive terminal fixed to the case and joined by ultrasonic welding from the thickness direction of the electrode body to a laminated current collecting portion in which the positive electrode foil exposed portions of the flat electrode body are stacked and bundled together in the thickness direction of the electrode body, the positive electrode terminal being fixed to the case and joined from the thickness direction of the electrode body to the laminated current collecting portion in which the positive electrode foil exposed portions of the flat electrode body are stacked and bundled together in the thickness direction of the electrode body, An electricity storage device, The outer surface of the electrode body; a first imaginary boundary surface that is imaginarily provided at a boundary between the electrode body main body portion and the positive electrode current collecting portion of the electrode body and is perpendicular to the axial direction; and Among the four virtual intersections at which a pair of second virtual boundary surfaces parallel to the axial direction and the thickness direction of the electrode body intersect with each other, the second virtual boundary surfaces are virtually provided at the boundaries between an electrode flat portion in which the positive electrode plate, the negative electrode plate, and the separator are overlapped in a flat plate shape, and a pair of electrode R portions in which the positive electrode plate, the negative electrode plate, and the separator are overlapped while being bent into a semi-cylindrical shape, in the electrode body, The position of the nearest virtual intersection of the weld portion formed on the laminated current collecting portion by the ultrasonic welding and extending in the electrode body width direction perpendicular to the axial direction and the electrode body thickness direction and the axial direction, which is closest to the surface weld portion that appears on the outer surface of the laminated current collecting portion, is determined by When the reference position is The surface welded portion is An inner side extending parallel to the width direction of the electrode body; an outer side extending parallel to the inner side and positioned on the one side in the axial direction relative to the inner side; a near side that connects an inner near end point of the two inner end points of the inner side that is closer to the reference position and an outer near end point of the two outer end points of the outer side that is closer to the reference position; a peripheral shape having a far side connecting an inner far end point of the two inner end points that is far from the reference position and an outer far end point of the two outer end points that is far from the reference position, and the outer near end point of the outer side is located on one side toward the reference position from the winding axis in the electrode body width direction relative to the inner near end point of the inner side, The near side defines a straight line connecting the inner near end point and the outer near end point, or defines a line passing through an area farther from the reference position than the straight line. Energy storage device.

2. The energy storage device according to claim 1, The welded portion is The positive electrode current collecting portion of the electrode body is formed on the reference position side of the winding axis in the width direction of the electrode body. Energy storage device.

3. The energy storage device according to claim 2, The surface welded portion is The outer far end point of the outer side and the inner far end point of the inner side are disposed at the same position in the width direction of the electrode body, and the far side has an outer circumferential shape extending parallel to the axial direction. Energy storage device.

4. The electricity storage device according to any one of claims 1 to 3, The electrode body has a thickness dimension of 10 mm or more. Energy storage device.

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