JP2018142513A - Power storage device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent an active material layer from falling, and to suppress interference between a case and an electrode assembly.SOLUTION: A cathode electrode 41 comprises a cathode body 42 and a cathode tab 43. In a view in a lamination direction of the cathode electrode 41 and an anode electrode, the cathode body 42 includes a cathode upper side 62, a cathode lower side 63, cathode lateral sides 64 and 65, cathode tab-side cornering sides 66 and 67, and cathode bottom-side cornering sides 68 and 69. An extension of the cathode upper side 62 is defined as a first cathode virtual line 62A, an extension of the cathode lower side 63 is defined as a second cathode virtual line 63A, and extensions of the cathode lateral sides 64 and 65 are defined as third cathode virtual lines 64A ad 65A. An area of tab-side virtual surfaces A1 and A2 enclosed by the first cathode virtual line 62A, the third cathode virtual lines 64A and 65A and the cathode tab-side cornering sides 66 and 67 is smaller than an area of bottom-side virtual surfaces A3 and A4 enclosed by the second cathode virtual line 63A, the third cathode virtual lines 64A and 65A and the cathode bottom-side cornering sides 68 and 69.SELECTED DRAWING: Figure 4

Description

  The present invention relates to a power storage device.

  2. Description of the Related Art A power storage device such as a secondary battery or a capacitor includes a case and an electrode assembly housed in the case (see, for example, Patent Document 1). The case includes a case main body having an opening and a lid member that closes the opening of the case main body. The case body includes a bottom wall, a side wall, and a case corner that connects the bottom wall and the side wall. The electrode assembly includes positive and negative electrodes and a separator that insulates the electrodes from each other. The electrode includes a metal foil and an active material layer provided on at least one surface of the metal foil.

Japanese Patent Laid-Open No. 2006-171239

  By the way, when a part of the active material layer falls off from the metal foil, a part of the dropped active material layer becomes a foreign substance, which causes a short circuit. Further, when the electrode assembly is accommodated in a case having a rounded corner, the electrode assembly may ride on the corner of the case. As a result, the electrode assembly cannot be accommodated in the case, or the electrode assembly becomes difficult to accommodate in the case.

  An object of the present invention is to provide a power storage device that can suppress the falling off of an active material layer and can suppress interference between a case and an electrode assembly.

  A power storage device that solves the above problems includes an electrode assembly in which positive and negative electrodes are alternately stacked with a separator insulated, and a case in which the electrode assembly is accommodated, each of the electrodes being a metal foil. An electrode body provided with an active material layer on at least one side thereof, and a tab made of the metal foil and extending from the electrode body.The case includes a bottom wall, a side wall, the bottom wall, and the side wall. A rounded corner of the case, and when viewed from the stacking direction of the electrodes, the electrode main body is a first side provided with the tab, and a side opposite to the first side, and is formed on the bottom wall. The first side is located between the second side facing each other, the pair of third sides extending in the direction in which the first side and the second side face each other and facing each other, and the first side and the third side. A first chamfered edge connecting the side and the third side; and A second chamfer that is located between two sides and the third side and connects the second side and the third side, and an extension line of the first side is defined as a first imaginary line. If the extension line of the second side is the second virtual line and the extension line of the third side is the third virtual line, the first virtual line, the third virtual line, and the first corner edge The area of the first imaginary plane surrounded by is smaller than the area of the second imaginary plane surrounded by the second imaginary line, the third imaginary line, and the second chamfer.

  The active material layer provided on the metal foil is more likely to drop off as the portion is provided at the corner, and the active material layer is more likely to drop off as the angle of the corner is smaller. By providing the first chamfered edge and the second chamfered edge, the angle of the electrode body can be made obtuse. For this reason, it can suppress that an active material layer falls off.

  Moreover, the location which can interfere with the case corner part in an electrode main body can be spaced apart from a case corner part by providing a 2nd corner edge. Furthermore, by making the area of the second imaginary surface larger than the area of the first imaginary surface, a portion that can interfere with the case corner in the electrode body can be further separated from the case corner. Therefore, interference between the case and the electrode assembly can be suppressed.

About the said electrical storage apparatus, the area of a said 1st virtual surface and the area of a said 2nd virtual surface may be so large that the distance from the said tab is long.
In the power storage device, current flows in a current path from the tab of one polarity electrode to the tab of the other polarity electrode. At this time, the path length of the current path changes according to the distance from the tab. The current path extends from the tab in a wave shape. In the electrode assembly, a resistance distribution is generated according to the path length of the current path, and the resistance becomes lower as the current path has a shorter path length. In accordance with this resistance distribution, a current distribution is generated in the electrode. Since the current flowing through the electrode increases as the distance from the tab increases, the portion of the active material layer that is away from the tab does not contribute to the discharge. By setting the area of each virtual surface to be larger as the distance from the tab is longer, it is possible to suppress the drop of the active material layer by increasing the area of each virtual surface while suppressing the decrease in the capacity of the power storage device. .

  In the power storage device, a pair of the first chamfer is provided so as to connect the first side and each third side, and the second chamfer is composed of the second side and each third side. A pair is provided to connect the two.

  According to this, compared with the case where the 1st chamfering edge and the 2nd chamfering edge are provided one by one, the falling off of the active material layer can be suppressed.

  According to the present invention, falling off of the active material layer can be suppressed, and interference between the case and the electrode assembly can be suppressed.

The perspective view which fractures | ruptures and shows a part of secondary battery. Sectional drawing which expands and shows a part of secondary battery. The exploded perspective view of an electrode assembly. The front view of a positive electrode. The front view of a negative electrode. The figure which shows the electric current path | route of an electrode assembly typically.

Hereinafter, an embodiment of the power storage device will be described.
As shown in FIGS. 1 and 2, the secondary battery 10 as a power storage device includes a box-shaped case 20 and an electrode assembly 40 accommodated in the case 20. The secondary battery 10 of the present embodiment is a square battery and is a lithium ion battery. The case 20 includes a main body 22 and a lid member 21.

  The main body 22 includes a rectangular bottom wall 23, a square cylindrical side wall 25, and a case corner 24 that connects the bottom wall 23 and the side wall 25. The side wall 25 is erected from the bottom wall 23 via the case corner 24. The case corner 24 has a round shape (arc shape) that protrudes outward from the case 20 from the bottom wall 23 toward the side wall 25. The case 20 is manufactured by plastically deforming a metal plate by plastic working such as deep drawing or impact pressing. The case corner 24 is generated during plastic working.

  The side wall 25 includes a pair of first side portions 26 facing each other and a pair of second side portions 27 facing each other. The first side portion 26 is erected from the short side of the bottom wall 23 via the case corner portion 24. The second side portion 27 is erected from the long side of the bottom wall 23 via the case corner portion 24.

  The electrode assembly 40 is accommodated in the main body 22. The lid member 21 closes the opening 28 surrounded by the side wall 25 by being welded to the main body 22 after the electrode assembly 40 is accommodated in the main body 22.

  As shown in FIG. 3, the electrode assembly 40 includes a positive electrode 41 and a negative electrode 51 as positive and negative electrodes, and a separator 81. The electrode assembly 40 is configured by alternately laminating a plurality of positive electrodes 41 and a plurality of negative electrodes 51 in a state of being insulated by separators 81. The separator 81 has a rectangular shape. The separator 81 is made of, for example, polypropylene. In the following description, the “stacking direction” is a direction in which the positive electrode 41 and the negative electrode 51 are stacked.

  As shown in FIGS. 3 and 4, the positive electrode 41 includes a positive electrode main body 42 as an electrode main body and a positive electrode tab 43 as a tab protruding from the positive electrode main body 42. The positive electrode main body 42 includes a positive electrode metal foil (aluminum foil in this embodiment) 44 as a metal foil and a positive electrode active material layer 45 as an active material layer provided on both surfaces of the positive electrode metal foil 44. The positive electrode active material layer 45 contains a positive electrode active material, a binder, a conductive additive, and the like. The positive electrode tab 43 is a portion obtained by extending a part of the positive electrode metal foil 44 so as to protrude from the positive electrode main body 42.

  As shown in FIGS. 3 and 5, the negative electrode 51 includes a negative electrode main body 52 as an electrode main body and a negative electrode tab 53 as a tab protruding from the negative electrode main body 52. The negative electrode main body 52 includes a negative electrode metal foil (copper foil in this embodiment) 54 as a metal foil, and a negative electrode active material layer 55 as an active material layer provided on both surfaces of the negative electrode metal foil 54. The negative electrode active material layer 55 contains an active material for a negative electrode, a binder, a conductive additive, and the like. The negative electrode tab 53 is a portion obtained by extending a part of the negative electrode metal foil 54 so as to protrude from the negative electrode main body 52.

  In the lithium ion battery, the capacity of the negative electrode 51 is increased compared to the capacity of the positive electrode 41 in order to suppress lithium deposition at the negative electrode 51. Therefore, the area of the negative electrode body 52 is larger than the area of the positive electrode body 42, and the outer dimensions of the negative electrode body 52 are larger than the outer dimensions of the positive electrode body 42 except for the thickness. First, the positive electrode main body 42 will be described.

  As shown in FIG. 4, the positive electrode main body 42 has a substantially rectangular shape, and has four corners chamfered. The positive electrode main body 42 includes positive electrode chamfered portions 46, 47, 48 and 49 at four corners. The shapes of both sides in the thickness direction of the positive electrode main body 42 are the same. Therefore, when the positive electrode main body 42 is viewed from the front, the same shape is obtained when viewed from any direction in the thickness direction. The shape of the positive electrode main body 42 viewed from the front is the same as the shape of the positive electrode main body 42 viewed from the stacking direction.

  The positive electrode main body 42 includes a positive electrode upper side 62 and a positive electrode lower side 63 which are parallel to each other and a pair of positive electrode side sides 64 and 65 which are parallel to each other when viewed from the front. The positive electrode tab 43 is integrally provided on the positive electrode upper side 62. Therefore, the positive electrode upper side 62 becomes the first side where the positive electrode tab 43 is provided, and the positive electrode lower side 63 becomes the second side which is the opposite side of the first side. The positive electrode side edges 64 and 65 extend in a direction in which the positive electrode upper edge 62 and the positive electrode lower edge 63 face each other, and face each other. Accordingly, the positive side 64, 65 is the third side.

  The positive electrode tab 43 is provided close to one of the positive electrode side sides 64 and 65. In the present embodiment, of the positive electrode side edges 64 and 65, the positive electrode side edge 64 closer to the positive electrode tab 43 is the first positive electrode side edge 64, and the positive electrode side edge 65 far from the positive electrode tab 43 is the second positive electrode side. Let it be side 65.

  The positive electrode main body 42 includes two positive electrode tab side corners 66 and 67 that connect the end of the positive electrode upper side 62 and the ends of the positive electrode side sides 64 and 65 when viewed from the front. The positive electrode tab side chamfered edges 66 and 67 are the first positive electrode chamfered part 46 and the second positive electrode chamfered part 47 located at both ends of the positive electrode upper edge 62 among the positive electrode chamfered parts 46, 47, 48 and 49. Is configured. The positive tab side corner edges 66 and 67 are located between the positive electrode upper side 62 and the positive electrode side edges 64 and 65 and are connected to the positive electrode upper edge 62 and the positive electrode side edges 64 and 65. Become.

  Of the pair of positive tab side corners 66 and 67, the positive tab side corner 66 connecting the upper side 62 and the first positive side 64 is defined as a first positive tab side corner 66, A positive electrode tab side cornering edge 67 connecting the second positive electrode side edge 65 is defined as a second positive electrode tab side cornering edge 67. The positive electrode tab side corner edges 66 and 67 are sides that obliquely intersect the positive electrode upper side 62 and the positive electrode side sides 64 and 65. The angle formed by the positive electrode upper side 62 and the first positive electrode tab side cornering edge 66 is an obtuse angle. The angle formed by the first positive electrode side 64 and the first positive electrode tab side chamfer 66 is an obtuse angle. The angle formed by the positive electrode upper side 62 and the second positive electrode tab side cornering edge 67 is an obtuse angle. The angle formed between the second positive electrode side 65 and the second positive electrode tab side corner edge 67 is an obtuse angle. In other words, the positive tab side corner edges 66 and 67 are sides where the angles formed between the positive electrode upper side 62 and the positive electrode side sides 64 and 65 are obtuse angles.

  A line segment S1 connecting the intersection point P1 of the first positive electrode tab side corner edge 66 and the positive electrode upper side 62, the intersection point P2 of the first positive electrode tab side corner edge 66 and the first positive electrode side edge 64, and the positive electrode upper side 62 The angle formed is an obtuse angle. The angle formed by the line segment S1 and the first positive electrode side 64 is an obtuse angle. In the present embodiment, the line segment S1 and the first positive electrode tab side corner edge 66 are the same line segment.

  A line segment S2 connecting the intersection point P3 of the second positive electrode tab side corner edge 67 and the positive electrode upper side 62, the intersection point P4 of the second positive electrode tab side corner edge 67 and the second positive electrode side edge 65, and the positive electrode upper side 62 The angle formed is an obtuse angle. The angle formed by the line segment S2 and the second positive electrode side 65 is an obtuse angle. In the present embodiment, the line segment S2 and the second positive electrode tab side corner edge 67 are the same line segment.

  The positive electrode main body 42 includes two positive electrode bottom side corners 68 and 69 that connect the end of the positive electrode lower side 63 and the ends of the positive electrode side sides 64 and 65 when viewed from the front. The positive bottom chamfers 68 and 69 are the third positive chamfer 48 and the fourth positive chamfer 49 located at both ends of the lower positive side 63 of the positive chamfers 46, 47, 48, and 49. Is configured. The positive bottom side corner edges 68 and 69 are located between the positive electrode lower side 63 and the positive electrode side edges 64 and 65 and are connected to the positive electrode lower side 63 and the positive electrode side edges 64 and 65. Become.

  Of the pair of positive electrode bottom side corner edges 68 and 69, a positive electrode bottom side corner edge 68 that connects the positive electrode lower edge 63 and the first positive electrode side edge 64 is defined as a first positive electrode bottom edge corner edge 68. The positive electrode bottom side cornering edge 69 connecting the second positive electrode side edge 65 is defined as a second positive electrode bottom side cornering edge 69. The positive electrode bottom side corners 68 and 69 are sides that obliquely intersect the positive electrode lower side 63 and the positive electrode side sides 64 and 65. The angle formed by the positive electrode lower side 63 and the first positive electrode bottom side cornering edge 68 is an obtuse angle. The angle formed by the first positive electrode side 64 and the first positive electrode bottom side corner 68 is an obtuse angle. The angle formed by the positive electrode lower side 63 and the second positive electrode bottom side cornering edge 69 is an obtuse angle. The angle formed between the second positive electrode side 65 and the second positive electrode bottom side corner 69 is an obtuse angle. That is, the positive electrode bottom side corners 68 and 69 are sides where the angle between the positive electrode lower side 63 and the positive electrode side sides 64 and 65 is an obtuse angle.

  A line segment S3 connecting the intersection point P5 of the first positive electrode bottom side corner edge 68 and the positive electrode lower edge 63, the intersection point P6 of the first positive electrode bottom edge corner edge 68 and the first positive electrode side edge 64, and the positive electrode lower edge 63 The angle formed is an obtuse angle. The angle formed by the line segment S3 and the first positive electrode side 64 is an obtuse angle. In the present embodiment, the line segment S3 and the first positive electrode bottom side corner edge 68 are the same line segment.

  A line segment S4 connecting the intersection point P7 of the second positive electrode bottom side corner edge 69 and the positive electrode lower edge 63, the intersection point P8 of the second positive electrode bottom edge corner edge 69 and the second positive electrode side edge 65, and the positive electrode lower edge 63 The angle formed is an obtuse angle. The angle formed by the line segment S4 and the second positive electrode side 65 is an obtuse angle. In the present embodiment, the line segment S4 and the second positive electrode bottom side corner edge 69 are the same line segment.

  The peripheral edge of the positive electrode main body 42 is constituted by the positive electrode upper side 62, the positive electrode lower side 63, the positive electrode side sides 64 and 65, and the chamfered sides 66, 67, 68 and 69. In addition, each chamfer 46, 47, 48, 49 of this embodiment is a C surface shape.

  “Chamfered portion” is a surface that prevents surfaces from intersecting at right angles by connecting surfaces that intersect at right angles or acute angles without chamfered portions 46, 47, 48, and 49. . Note that the “chamfered portion” does not indicate only a surface generated by chamfering the four corners after the rectangular positive electrode body 42 is manufactured. For example, the positive electrode upper side 62, the positive electrode lower side 63, the positive electrode side sides 64 and 65, and the chamfered sides 66, 67, 68, and 69 are simultaneously manufactured by cutting, and the positive electrode main body 42 that is not chamfered is also used. The surfaces formed by the chamfered edges 66, 67, 68, 69 are chamfered portions 46, 47, 48, 49.

  Here, the extension line of the positive electrode upper side 62 is a first positive electrode virtual line 62A as a first virtual line, the extension line of the positive electrode lower side 63 is a second positive electrode virtual line 63A as a second virtual line, and each positive side 64 , 65 are taken as third positive virtual lines 64A, 65A as third virtual lines. A quadrilateral connecting the intersecting points of the respective positive electrode virtual lines 62A, 63A, 64A, 65A is the outer shape of the positive electrode main body 42 when it is assumed that there are no respective corners 66, 67, 68, 69.

  The surfaces surrounded by the first positive electrode virtual line 62A, the third positive electrode virtual lines 64A and 65A, and the positive electrode tab side corner edges 66 and 67 are defined as positive electrode tab side virtual surfaces A1 and A2 as first virtual surfaces. There are the same number of the positive electrode tab side virtual surfaces A1 and A2 as the number of the positive electrode tab side corners 66 and 67, and two exist in the present embodiment. Of the two positive electrode tab side virtual surfaces A1 and A2, the first positive electrode virtual line A1 surrounded by the first positive electrode virtual line 62A, the third positive electrode virtual line 64A, and the first positive electrode tab side corner 66 is the first. The positive electrode tab side virtual surface A <b> 1 is defined as the positive electrode tab side virtual surface A <b> 2 surrounded by the first positive electrode virtual line 62 </ b> A, the third positive electrode virtual line 65 </ b> A, and the second positive electrode tab side square edge 67. Let A2.

  Surfaces surrounded by the second positive electrode virtual line 63A, the third positive electrode virtual lines 64A and 65A, and the positive electrode bottom side corners 68 and 69 are defined as positive electrode bottom virtual surfaces A3 and A4 as second virtual surfaces. There are the same number of the positive electrode bottom side virtual surfaces A3 and A4 as the number of the positive electrode bottom side corners 68 and 69, and two exist in the present embodiment. Of the two positive bottom virtual surfaces A3 and A4, the first positive virtual surface A3 surrounded by the second positive virtual line 63A, the third positive virtual line 64A, and the first positive bottom corner 68 is a first. The positive electrode bottom-side virtual surface A3 is defined as a positive electrode bottom-side virtual surface A4 surrounded by the second positive electrode virtual line 63A, the third positive electrode virtual line 65A, and the second positive electrode bottom-side corner 69. A4.

  The area of the first positive electrode tab side virtual surface A1 is smaller than the area of the first positive electrode bottom side virtual surface A3, and the area of the second positive electrode tab side virtual surface A2 is smaller than the area of the second positive electrode bottom side virtual surface A4. When the virtual surfaces A1, A2, A3, and A4 are present at the four corners as in the present embodiment, the above-described relationship is applied to the virtual surfaces A1, A2, A3, and A4 facing the opposing direction of the positive electrode upper side 62 and the positive electrode lower side 63. Holds.

  The area of each virtual plane A1, A2, A3, A4 corresponds to the distance from the positive electrode tab 43. The area of each of the virtual surfaces A 1, A 2, A 3, A 4 of this embodiment is larger as the distance from the positive electrode tab 43 increases. As indicated by the arrow Y4, the area of the second positive electrode bottom side virtual surface A4 that is farthest from the positive electrode tab 43 is the largest, and as indicated by the arrow Y2, the area of the second positive electrode tab side virtual surface A2 is the second. large. The area of the first positive electrode tab side virtual surface A1 closest to the positive electrode tab 43 is the smallest as shown by the arrow Y1, and the area of the first positive electrode bottom side virtual surface A3 is the second smallest as shown by the arrow Y3.

  The area of the virtual surfaces A1, A2, A3, and A4 described above is the chamfering when chamfering is performed at each of the chamfered edges 66, 67, 68, and 69 assuming that the positive electrode main body 42 has a square shape. Chamfered area.

Next, the negative electrode body 52 will be described.
As shown in FIG. 5, in the present embodiment, the positive electrode main body 42 and the negative electrode main body 52 have a similar relationship in which the external dimensions of the negative electrode body 52 are larger than the external dimensions of the positive electrode body 42. The peripheral edge of the negative electrode body 52 has a shape that is larger than the peripheral edge of the positive electrode body 42 by a certain dimension L10. The constant dimension L10 is set so that the area ratio (capacity ratio) between the negative electrode 51 and the positive electrode 41 is an area ratio necessary for suppressing lithium deposition on the negative electrode 51. When designing the negative electrode main body 52, the positive electrode main body 42 is designed, and then the outer periphery of the positive electrode 41 is designed to have an outer edge with a certain dimension L <b> 10.

  Since the negative electrode main body 52 is similar to the positive electrode main body 42, the description will be simplified. The negative electrode main body 52 includes a negative electrode upper side 72 corresponding to the positive electrode upper side 62, a negative electrode lower side 73 corresponding to the positive electrode lower side 63, and negative electrode side sides 74 and 75 corresponding to the positive electrode side sides 64 and 65.

  The negative electrode tab 53 is integrally provided on the negative electrode upper side 72. In the present embodiment, of the negative electrode side sides 74 and 75, the negative electrode side region 74 closer to the negative electrode tab 53 is defined as the first negative electrode side region 74, and the negative electrode side region 75 far from the negative electrode tab 53 is defined as the second negative electrode side. Let it be side 75. The negative electrode upper side 72 is a first side where the negative electrode tab 53 is provided, and the negative electrode lower side 73 is a second side which is the opposite side of the first side. The negative electrode side sides 74 and 75 extend in a direction in which the negative electrode upper side 72 and the negative electrode lower side 73 face each other, and face each other. Therefore, the negative electrode side sides 74 and 75 become the third side.

  As shown in FIGS. 4 and 5, the dimension L11 of the negative electrode upper side 72 is longer than the dimension L1 of the positive electrode upper side 62. The dimension L12 of the negative electrode lower side 73 is longer than the dimension L2 of the positive electrode lower side 63. The dimension L13 of the first negative electrode side 74 is longer than the dimension L3 of the first positive electrode side 64. The dimension L14 of the second negative electrode side 75 is longer than the dimension L4 of the second positive electrode side 65.

  As shown in FIG. 5, the negative electrode main body 52 includes negative electrode chamfered portions 56, 57, 58, and 59 corresponding to the positive electrode chamfered portions 46, 47, 48, and 49. The negative electrode body 52 includes negative electrode tab side corners 76 and 77 corresponding to the positive electrode tab side corners 66 and 67, and negative electrode bottom side corners 78 and 79 corresponding to the positive electrode bottom side corners 68 and 69. Is provided.

  The negative electrode tab side chamfers 76 and 77 are the first negative electrode chamfered portion 56 and the second negative electrode chamfered portion 57 located at both ends of the negative electrode upper side 72 among the negative electrode chamfered portions 56, 57, 58 and 59. Is configured. The negative electrode tab side chamfers 76 and 77 are located between the negative electrode upper side 72 and the negative electrode side sides 74 and 75 and are connected to the negative electrode upper side 72 and the negative electrode side sides 74 and 75. Become.

  The negative electrode bottom side chamfers 78 and 79 are the third negative electrode chamfer 58 and the fourth negative electrode chamfer 59 located at both ends of the negative electrode lower side 73 among the negative electrode chamfers 56, 57, 58 and 59. Is configured. The negative electrode bottom side corners 78 and 79 are located between the negative electrode lower side 73 and the negative electrode side sides 74 and 75, and are connected to the negative electrode lower side 73 and the negative electrode side sides 74 and 75. Become.

  Of the two negative electrode tab side corner edges 76 and 77, the negative electrode tab side corner edge 76 connecting the negative electrode upper side 72 and the first negative electrode side edge 74 is defined as a first negative electrode tab side corner edge 76, The negative electrode tab side cornering edge 77 connecting the second negative electrode side edge 75 is defined as a second negative electrode tab side cornering edge 77. The negative electrode tab side corners 76 and 77 are sides that obliquely intersect the negative electrode upper side 72 and the negative electrode side sides 74 and 75. The angle formed by the negative electrode upper side 72 and the first negative electrode tab side cornering side 76 is an obtuse angle. The angle formed between the first negative electrode side 74 and the first negative electrode tab side chamfer 76 is an obtuse angle. The angle formed by the negative electrode upper side 72 and the second negative electrode tab side cornering edge 77 is an obtuse angle. The angle formed between the second negative electrode side 75 and the second negative electrode tab side corner 77 is an obtuse angle. That is, the negative electrode tab side corners 76 and 77 are sides where the angle between the negative electrode upper side 72 and the negative electrode side sides 74 and 75 is an obtuse angle.

  A line segment S11 connecting the intersection point P11 of the first negative electrode tab side chamfer 76 and the negative electrode upper side 72, the intersection point P12 of the first negative electrode tab side chamfer 76 and the first negative electrode side 74, and the negative electrode upper side 72 The angle formed is an obtuse angle. The angle formed by the line segment S11 and the first negative electrode side 74 is an obtuse angle. In the present embodiment, the line segment S11 and the first negative electrode tab side corner edge 76 are the same line segment.

  A line segment S12 connecting the intersection point P13 of the second negative electrode tab side corner 77 and the negative electrode upper side 72, the intersection point P14 of the second negative electrode tab side corner 77 and the second negative electrode side 75, and the negative electrode upper side 72 The angle formed is an obtuse angle. The angle formed by the line segment S12 and the second negative electrode side 75 is an obtuse angle. In the present embodiment, the line segment S12 and the second negative electrode tab side corner edge 77 are the same line segment.

  Of the two negative electrode bottom side corners 78 and 79, the negative electrode bottom side corner edge 78 connecting the negative electrode lower side 73 and the first negative electrode side edge 74 is referred to as a first negative electrode bottom side corner edge 78. A negative electrode bottom side chamfer 79 that connects the second negative electrode side 75 is defined as a second negative electrode bottom chamfer 79. The negative electrode bottom side corners 78 and 79 are sides that obliquely intersect the negative electrode lower side 73 and the negative electrode side sides 74 and 75. The angle formed by the negative electrode lower side 73 and the first negative electrode bottom side cornering edge 78 is an obtuse angle. The angle formed between the first negative electrode side 74 and the first negative electrode bottom side chamfer 78 is an obtuse angle. The angle formed by the negative electrode lower side 73 and the second negative electrode bottom side cornering edge 79 is an obtuse angle. The angle formed between the second negative electrode side 75 and the second negative electrode bottom side corner 79 is an obtuse angle. That is, the negative electrode bottom side corners 78 and 79 are sides where the angle between the negative electrode lower side 73 and the negative electrode side sides 74 and 75 is an obtuse angle.

  A line segment S13 connecting the intersection point P15 of the first negative electrode bottom side corner edge 78 and the negative electrode lower edge 73, the intersection point P16 of the first negative electrode bottom edge corner edge 78 and the first negative electrode side edge 74, and the negative electrode lower edge 73 The angle formed is an obtuse angle. The angle formed by the line segment S13 and the first negative electrode side 74 is an obtuse angle. In the present embodiment, the line segment S13 and the first negative electrode bottom side corner edge 78 are the same line segment.

  A line segment S14 connecting the intersection P17 of the second negative electrode bottom side corner 79 and the negative electrode lower side 73, the intersection point P18 of the second negative electrode bottom side corner 79 and the second negative electrode side 75, and the negative electrode lower side 73 The angle formed is an obtuse angle. The angle formed by the line segment S14 and the second negative electrode side 75 is an obtuse angle. In the present embodiment, the line segment S14 and the second negative electrode bottom side corner edge 79 are the same line segment.

  An extension line of the negative electrode upper side 72 is a first negative electrode virtual line 72A as a first virtual line, an extension line of the negative electrode lower side 73 is a second negative electrode virtual line 73A as a second virtual line, and The extension lines are defined as third negative virtual lines 74A and 75A as third virtual lines. A quadrilateral connecting the intersecting points of the virtual lines 72A, 73A, 74A, and 75A is the outer shape of the negative electrode main body 52 when it is assumed that there are no corners 76, 77, 78, and 79.

  The surfaces surrounded by the first negative electrode imaginary line 72A, the third negative electrode imaginary lines 74A and 75A, and the negative electrode tab side corners 76 and 77 are defined as negative electrode tab side virtual surfaces A11 and A12 as first virtual surfaces. The number of negative electrode tab side virtual surfaces A11 and A12 is the same as the number of negative electrode tab side corners 76 and 77, and there are two in this embodiment. Of the two negative tab-side virtual surfaces A11 and A12, the first negative electrode-side virtual surface A11 surrounded by the first negative-electrode virtual line 72A, the third negative-electrode virtual line 74A, and the first negative-electrode tab-side corner 76 is the first. It is assumed that the negative electrode tab side virtual surface A11. Further, the negative electrode tab side virtual surface A12 surrounded by the first negative electrode virtual line 72A, the third negative electrode virtual line 75A, and the second negative electrode tab side corner 77 is defined as a second negative electrode tab side virtual surface A12.

  Surfaces surrounded by the second negative electrode virtual line 73A, the third negative electrode virtual lines 74A and 75A, and the negative electrode bottom side corner edges 78 and 79 are defined as negative electrode bottom virtual surfaces A13 and A14 as second virtual surfaces. There are the same number of negative electrode bottom side virtual surfaces A13 and A14 as the number of negative electrode bottom side corners 78 and 79, and there are two in this embodiment. Of the two negative electrode bottom side virtual surfaces A13 and A14, the first negative electrode virtual side A13 surrounded by the second negative electrode virtual line 73A, the third negative electrode virtual line 74A, and the first negative electrode bottom side chamfer 78 is the first. The negative electrode bottom side virtual surface A13 is defined as a second negative electrode bottom side virtual surface A14 surrounded by the second negative electrode virtual line 73A, the third negative electrode virtual line 75A, and the second negative electrode bottom side corner 79. A14.

  The area of the first negative electrode tab side virtual surface A11 is smaller than the area of the first negative electrode bottom side virtual surface A13, and the area of the second negative electrode tab side virtual surface A12 is smaller than the area of the second negative electrode bottom side virtual surface A14. When the virtual surfaces A11, A12, A13, and A14 exist at the four corners as in the present embodiment, the relationship described above is applied to the virtual surfaces A11, A12, A13, and A14 facing the opposing direction of the negative electrode upper side 72 and the negative electrode lower side 73. Holds.

  The area of each virtual plane A11, A12, A13, A14 corresponds to the distance from the negative electrode tab 53. The area of each virtual plane A <b> 11, A <b> 12, A <b> 13, A <b> 14 of this embodiment is larger as it is farther from the negative electrode tab 53. As indicated by the arrow Y14, the area of the second negative electrode bottom side virtual surface A14 that is farthest from the negative electrode tab 53 is the largest, and as indicated by the arrow Y12, the area of the second negative electrode tab side virtual surface A12 is the second. large. The area of the first negative electrode tab side virtual surface A11 closest to the negative electrode tab 53 is the smallest as shown by the arrow Y11, and the area of the first negative electrode bottom side virtual surface A13 is the second smallest as shown by the arrow Y13.

  The area of the virtual surfaces A11, A12, A13, and A14 described above is the chamfering when chamfering is performed at each of the chamfered edges 76, 77, 78, and 79, assuming that the negative electrode body 52 has a rectangular shape. Chamfered area.

  As shown in FIG. 3, in the positive electrode 41 and the negative electrode 51, the positive electrode upper side 62 and the negative electrode upper side 72 face the same direction, and the first positive electrode side 64 and the second negative electrode side 75 have the same direction. They are stacked in a facing manner.

  Thus, as shown in FIG. 6, when the electrode assembly 40 is viewed from the stacking direction, the positive electrode tab 43 and the negative electrode tab 53 sandwich the center position C in the direction along the positive electrode upper side 62 and the negative electrode upper side 72. Is located. That is, the tabs 43 and 53 are arranged at positions deviated from the center position C.

  As shown in FIGS. 1 and 2, the electrode assembly 40 is accommodated in the case 20 so that the positive electrode lower side 63 and the negative electrode lower side 73 face the bottom wall 23. The negative electrode lower side 73 faces the bottom wall 23 via an insulating sheet (not shown) while being accommodated in the case 20.

  The positive electrode side 64 and the negative electrode side 74 face the first side portion 26 via an insulating sheet (not shown). The positive electrode side 65 and the negative electrode side 75 face the first side portion 26 via an insulating sheet (not shown). The positive electrode chamfered portion 48 and the negative electrode chamfered portion 58 face the case corner 24. The positive electrode chamfered portion 49 and the negative electrode chamfered portion 59 face the case corner 24.

Next, the operation of the secondary battery 10 will be described.
Each active material layer 45, 55 provided on each metal foil 44, 54 may fall off from each metal foil 44, 54. At this time, the active material layers 45 and 55 provided at the corners of the metal foils 44 and 54 are more likely to drop off, and the active material layers 45 and 55 are more likely to drop off as the corner angle is smaller.

  If the positive electrode main body 42 and the negative electrode main body 52 have right angles at the four corners, the active material layers 45 and 55 are likely to fall off. On the other hand, the positive electrode main body 42 and the negative electrode main body 52 of the present embodiment are chamfered so that each corner is an obtuse angle.

  In addition, the case corner 24 is rounded in manufacturing. In this case, as shown by a two-dot chain line in FIG. 2, when the positive electrode main body 42 and the negative electrode main body 52 are rectangular, two of the four corners of the positive electrode main body 42 and the negative electrode main body 52 are on the bottom wall 23 side. One corner may interfere with the case corner 24, and the electrode assembly 40 may ride on the case corner 24. It is also conceivable to shorten the interval between the positive electrode side sides 64 and 65 and the interval between the negative electrode side sides 74 and 75 so that the positive electrode main body 42 and the negative electrode main body 52 do not interfere with the case corner 24. However, in this case, the capacity of the secondary battery 10 is reduced.

  By providing the chamfered portions 48, 49, 58, 59 as in the present embodiment, a surface where the chamfered portions 48, 49, 58, 59 are connected is formed on the outer surface of the electrode assembly 40. Since this surface faces the case corner 24, a portion that can interfere with the case corner 24 can be separated from the case corner 24. Further, since the area of the bottom virtual surfaces A3, A4, A13, A14 is larger than the area of the tab virtual surfaces A1, A2, A11, A12, interference between the electrode assembly 40 and the case corner 24 is prevented. Further suppression is being sought. In the present embodiment, since the separator 81 is rectangular, the corners of the separator 81 may come into contact with the case corner 24. The separator 81 is softer than the positive electrode 41 and the negative electrode 51 and deforms following the case corner 24. Therefore, it is not necessary for the separator 81 to consider interference with the case corner 24.

  As shown in FIG. 6, when the secondary battery 10 is discharged, current flows through the positive electrode 41 and the negative electrode 51 through a current path from the positive electrode tab 43 to the negative electrode tab 53. At this time, the path length of the current path changes according to the distance from the positive electrode tab 43. The current path extends in a wave shape from the positive electrode tab 43. In the electrode assembly 40, a resistance distribution is generated according to the path length of the current path, and the resistance becomes lower as the current path has a shorter path length. Then, according to this resistance distribution, current distribution occurs in the positive electrode 41 and the negative electrode 51. The closer to the positive electrode tab 43, the larger the current.

  Further, when the secondary battery 10 is charged, a current flows through the positive electrode 41 and the negative electrode 51 through a current path from the negative electrode tab 53 to the positive electrode tab 43. In this case, the closer to the negative electrode tab 53, the larger the current.

  In the positive electrode 41 and the negative electrode 51, the current becomes weaker as the distance from the tabs 43 and 53 increases. Therefore, the portion of the active material layers 45 and 55 that are farther from the tabs 43 and 53 are charged in the secondary battery 10. It will not contribute to the discharge. The area of each of the virtual surfaces A1, A2, A3, A4, A11, A12, A13, A14 increases as the distance from the tabs 43, 53 increases. That is, it can be said that the area of the virtual planes A1, A2, A3, A4, A11, A12, A13, and A14 is larger in a portion that does not contribute to charging / discharging of the secondary battery 10.

Therefore, according to the above embodiment, the following effects can be obtained.
(1) Omission of the active material layers 45 and 55 is suppressed by making each corner of the positive electrode main body 42 and the negative electrode main body 52 obtuse. Thereby, generation | occurrence | production of the foreign material by a part of active material layers 45 and 55 dropping off can be suppressed, and it can suppress that the electrode assembly 40 is short-circuited by a foreign material. Further, the interference between the electrode assembly 40 and the case 20 is suppressed by making the area of the bottom virtual surfaces A3, A4, A13, A14 larger than the areas of the tab virtual surfaces A1, A2, A11, A12. Can do.

  Since the chamfered portions 46, 47, 48, 49, 56, 57, 58, 59 are provided at the four corners that contribute little to the charge / discharge of the secondary battery 10, the interval between the positive electrode side sides 64, 65, the negative electrode Compared with the case where interference between the electrode assembly 40 and the case 20 is suppressed by shortening the distance between the side edges 74 and 75, the capacity of the secondary battery 10 is reduced.

  (2) The area of the virtual planes A1, A2, A3, A4, A11, A12, A13, and A14 is increased as the portion does not contribute to charging / discharging of the secondary battery 10. For this reason, dropping of the active material layers 45 and 55 is suppressed by increasing the area of the virtual surfaces A1, A2, A3, A4, A11, A12, A13, and A14 while suppressing a decrease in the capacity of the secondary battery 10. be able to.

In addition, you may change embodiment as follows.
If the area of the bottom side virtual surfaces A3, A4, A13, A14 is larger than the area of the tab side virtual surfaces A1, A2, A11, A12, each virtual surface A1, A2, A3, A4, A11, A12, A13, The area of A14 may not correspond to the distance from the tabs 43 and 53. Even in this case, by providing the chamfered portions 46, 47, 48, 49, 56, 57, 58, 59, it is possible to suppress the falling off of the active material layers 45, 55, and the bottom virtual surfaces A3, A4, A13. , A14 can be prevented from interfering with the electrode assembly 40 and the case 20 by making the area of A14 larger than the areas of the tab-side virtual surfaces A1, A2, A11, A12.

  The positive electrode 41 may not include the positive chamfered portions 46, 47, 48, and 49. That is, the positive electrode upper side 62 and the positive electrode lower side 63 and the positive electrode side sides 64 and 65 may intersect at right angles. In the lithium ion battery, the outer dimensions of the positive electrode 41 are smaller than the outer dimensions of the negative electrode 51. For this reason, when the outer shape of the positive electrode 41 is within the outer shape of the negative electrode 51 when viewed from the stacking direction, the positive electrode 41 may not include the positive chamfered portions 46, 47, 48, and 49.

  O Each chamfer 46, 47, 48, 49, 56, 57, 58, 59 may be round. In this case, the corner edges 66, 67, 68, 69, 76, 77, 78, 79 are also rounded. When each of the corner edges 66, 67, 68, 69, 76, 77, 78, 79 is rounded, each of the line segments S1, S2, S3, S4, S11, S12, S13, and S14 includes the corner edges 66. , 67, 68, 69, 76, 77, 78, 79 are different line segments. Further, the rounded chamfered portion and the C-shaped chamfered portion may be mixed.

  A part of the negative electrode 51 may not include the negative chamfers 56, 57, 58, and 59. Even in this case, a part of the negative electrode active material layer 55 is not easily dropped from the negative electrode 51 provided with the negative electrode chamfers 56, 57, 58, and 59. Compared with the case where all the negative electrode 51 does not include the negative chamfered portions 56, 57, 58, 59, the generation of foreign matters can be suppressed. Further, the interference between the electrode assembly 40 and the case 20 can be suppressed as compared with the case where all the negative electrodes 51 do not include the negative electrode chamfered portions 56, 57, 58, and 59. Similarly, a part of the positive electrode 41 may not include the positive chamfered portions 46, 47, 48, and 49.

  The area of each virtual surface A11, A12, A13, A14 of the negative electrode 51 may be larger as the distance from the positive electrode tab 43 is longer. That is, “the area of the virtual surface corresponds to the distance from the tab” includes a configuration in which the area of the virtual surface of the electrode increases in proportion to the distance from the tab of the electrode of different polarity. Similarly, the area of each virtual plane A1, A2, A3, A4 of the positive electrode 41 may be increased as the distance from the negative electrode tab 53 increases.

The outer dimension of the negative electrode 51 and the outer dimension of the positive electrode 41 may be the same.
The positive electrode 41 may include one of the positive chamfered portions 46 and 47. The positive electrode 41 may include one of the positive chamfered portions 48 and 49. The negative electrode 51 may include one of the negative electrode chamfered portions 56 and 57. The negative electrode 51 may include one of the negative electrode chamfered portions 58 and 59.

The negative electrode active material layer 55 may be provided only on one surface of the negative electrode metal foil 54. The positive electrode active material layer 45 may be provided only on one surface of the positive electrode metal foil 44.
○ The power storage device may be a capacitor.

  A1, A2, A11, A12 ... Tab side virtual surface (first virtual surface), A3, A4, A13, A14 ... Bottom side virtual surface (second virtual surface), 10 ... Secondary battery (power storage device), 20 ... Case: 23 ... Bottom wall, 24 ... Case corner, 25 ... Side wall, 40 ... Electrode assembly, 41 ... Positive electrode (electrode), 42 ... Positive electrode body (electrode body), 43 ... Positive electrode tab (tab), 44 ... Positive electrode metal foil (metal foil), 45 ... Positive electrode active material layer (active material layer), 46, 47, 48, 49 ... Positive electrode chamfered portion (first chamfered portion and second chamfered portion), 51 ... Negative electrode (Electrode), 52 ... negative electrode body (electrode body), 53 ... negative electrode tab (tab), 54 ... negative electrode metal foil (metal foil), 55 ... negative electrode active material layer (active material layer), 56, 57, 58, 59 ... negative electrode chamfered portion (first chamfered portion and second chamfered portion), 62 ... positive electrode upper side (first side), 62A ... first positive electrode virtual line (first Imaginary line), 63 ... positive electrode lower side (second side), 63A ... second positive electrode imaginary line (second imaginary line), 64, 65 ... positive electrode side (third side), 64A, 65A ... third positive electrode imaginary line (Third imaginary line), 66, 67 ... positive electrode tab side chamfer (first chamfer), 68, 69 ... positive electrode bottom chamfer (second chamfer), 72 ... negative electrode upper side (first Side), 72A ... first negative electrode virtual line (first virtual line), 73 ... negative electrode lower side (second side), 73A ... second negative electrode virtual line (second virtual line), 74, 75 ... negative electrode side side (first) 3 sides), 74A, 75A ... third negative electrode virtual line (third virtual line), 76, 77 ... negative electrode tab side corner edge (first corner edge), 78, 79 ... negative electrode bottom side edge edge (first edge). Diagonal edge), 81 ... separator.

Claims (3)

An electrode assembly in which positive and negative electrodes are alternately laminated with a separator insulated;
A case in which the electrode assembly is accommodated,
Each of the electrodes comprises an electrode body provided with an active material layer on at least one surface of a metal foil, and a tab made of the metal foil and extending from the electrode body,
The case includes a bottom wall, a side wall, and a rounded case corner connecting the bottom wall and the side wall,
When viewed from the stacking direction of the electrodes, the electrode main body is a first side provided with the tab, a second side opposite to the first side, the second side facing the bottom wall, the first side, and the first side. A pair of third sides extending in a direction facing the second side and facing each other, and a first side located between the first side and the third side and connecting the first side and the third side A chamfered edge, and a second chamfered edge that is located between the second edge and the third edge and connects the second edge and the third edge;
If the extension line of the first side is a first virtual line, the extension line of the second side is a second virtual line, and the extension line of the third side is a third virtual line,
The area of the first imaginary plane surrounded by the first imaginary line, the third imaginary line, and the first chamfer is the second imaginary line, the third imaginary line, and the second chamfer. A power storage device smaller than the area of the second virtual plane surrounded by the side.   The power storage device according to claim 1, wherein an area of the first virtual surface and an area of the second virtual surface are larger as a distance from the tab is longer. A pair of the first chamfer edges are provided so as to connect the first edge and each third edge,
3. The power storage device according to claim 1, wherein a pair of the second chamfer edges are provided so as to connect the second edge and the third edges.

Images