JP6859752B2 - Power storage device - Google Patents

Description

The present invention relates to a power storage device.

A power storage device such as a secondary battery or a capacitor includes a metal case and an electrode assembly housed in the case. The electrode assembly includes a positive electrode, a negative electrode, and a separator that insulates the positive electrode and the negative electrode. If the electrode assembly comes into contact with the case due to vibration or impact applied to the power storage device, it may cause a short circuit. The power storage device described in Patent Document 1 includes an insulating sheet interposed between the case and the electrode assembly. By electrically insulating the case and the electrode assembly with an insulating sheet, a short circuit between the case and the electrode assembly is suppressed.

Japanese Unexamined Patent Publication No. 2011-198663

By the way, when an electrode assembly in which a plurality of positive electrode electrodes and a plurality of negative electrode electrodes are alternately laminated is used, an insulating sheet is sandwiched between the corners of each electrode and the bottom wall and side wall of the case. If vibration or impact is applied to the power storage device in this state, the insulating sheet is damaged by the load applied to the insulating sheet from the corners of each electrode, which causes a short circuit.

An object of the present invention is to provide a power storage device capable of suppressing a short circuit between a case and an electrode assembly.

The power storage device that solves the above problems includes an electrode assembly in which a plurality of positive electrode electrodes and a plurality of negative electrode electrodes are alternately laminated in a state of being insulated by a separator arranged between the positive electrode electrode and the negative electrode electrode, and the electrode. A case containing the assembly and an insulating sheet interposed between the electrode assembly and the case and insulating the electrode assembly and the case are provided, and the case is provided with a bottom wall. The negative electrode is composed of a negative electrode body provided with a negative electrode active material layer on a negative electrode metal foil and the negative electrode metal foil, and comprises a side wall and a case corner portion connecting the bottom wall and the side wall. The negative electrode main body includes a negative electrode tab extending from the main body, and the negative electrode main body has a first negative electrode surface facing the bottom wall via the insulating sheet, a second negative electrode surface facing the side wall via the insulating sheet, and the first negative electrode surface. A negative electrode chamfered portion that is located between the 1 negative electrode surface and the 2nd negative electrode surface, connects the 1st negative electrode surface and the 2nd negative electrode surface, and faces the corner corner of the case via the insulating sheet. The separator comprises a first separator surface facing the bottom wall via the insulating sheet, and a second separator surface facing the side wall via the insulating sheet and connecting to the first separator surface. When viewed from the stacking direction of the positive electrode and the negative electrode, the outer shape of the negative electrode body fits within the outer shape of the separator, and the angle at which the first separator surface and the second separator surface are connected is described above. It is located between the negative electrode chamfered portion and the insulating sheet when viewed from the stacking direction.

According to this, by providing the negative electrode chamfered portion, a right angle or an acute angle is not formed between the first negative electrode surface and the second negative electrode surface. Further, by locating the corners of the separator between the negative electrode chamfered portion and the insulating sheet when viewed from the stacking direction of the positive electrode and the negative electrode, a part of the separator can be formed between the negative electrode chamfered portion and the insulating sheet. Intervene in between. When the negative electrode chamfered portion tries to come into contact with the insulating sheet, it comes into contact with the insulating sheet via the separator. As a result, a short circuit between the case and the electrode assembly can be suppressed.

Regarding the power storage device, the positive electrode includes a positive electrode body provided with a positive electrode active material layer on a positive electrode metal foil, and a positive electrode tab composed of the positive electrode metal foil and extending from the positive electrode body. The first positive electrode surface facing the bottom wall via the insulating sheet, the second positive electrode surface facing the side wall via the insulating sheet, and the position between the first positive electrode surface and the second positive electrode surface. A positive electrode chamfering portion that connects the first positive electrode surface and the second positive electrode surface and faces the corner portion of the case via the insulating sheet may be provided.

According to this, by providing the positive electrode with the positive electrode chamfered portion, it is possible to prevent the insulating sheet from being damaged by the contact between the positive electrode and the insulating sheet.
Regarding the power storage device, the inner surface of the corner of the case has a rounded shape, the chamfered negative electrode has a rounded shape that bulges toward the inner surface of the corner view of the case, and the radius of the inner surface of the corner of the case is , The dimension may be smaller than the radius of the negative electrode chamfered portion plus the thickness of the insulating sheet.

According to this, the gap between the negative electrode chamfered portion and the insulating sheet is easily maintained. The negative electrode chamfered portion is less likely to come into contact with the insulating sheet, and damage to the insulating sheet is further suppressed.

According to the present invention, a short circuit between the case and the electrode assembly can be suppressed.

An exploded perspective view of the secondary battery. FIG. 5 is an enlarged sectional view showing a part of a secondary battery. An exploded perspective view of the electrode assembly. Front view of positive electrode, negative electrode, and separator. The perspective view which shows a part of the electrode assembly enlarged. FIG. 5 is a sectional view taken along line 6-6 of FIG. 5 showing an electrode assembly. FIG. 2 is a sectional view taken along line 7-7 of FIG. 2 showing a secondary battery. The figure which shows the deformation example of the chamfer part.

Hereinafter, an embodiment of the power storage device will be described.
As shown in FIG. 1, the secondary battery 10 as a power storage device includes a box-shaped case 20 and an electrode assembly 40 housed 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.

As shown in FIGS. 1 and 2, the main body 22 includes a rectangular bottom wall 23, a square tubular side wall 25, and a case corner 24 connecting 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 portion 24 has a rounded shape (arc shape) that is convex 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 press working. 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 housed in the main body 22. The lid member 21 closes the opening 28 surrounded by the side wall 25 by accommodating the electrode assembly 40 in the main body 22 and then welding it to the main body 22.

The secondary battery 10 includes an electrode assembly 40 housed in the case 20 and an insulating sheet 30 that electrically insulates the case 20. The insulating sheet 30 is interposed between the inner surface of the main body 22 and the electrode assembly 40. The insulating sheet 30 is made of, for example, polypropylene. The thickness T of the insulating sheet 30 is, for example, 150 μm or more. The insulating sheet 30 is along the inner surface of the main body 22.

As shown in FIG. 3, the electrode assembly 40 includes a plurality of negative electrode electrodes 41, a plurality of positive electrode electrodes 51, and a plurality of bag-shaped separators 81. The positive electrode 51 is housed in the bag-shaped separator 81.

The negative electrode electrode 41 includes a negative electrode body 42 and a negative electrode tab 43. The negative electrode body 42 includes a negative electrode metal foil (copper foil in this embodiment) 44 and negative electrode active material layers 45 provided on both sides of the negative electrode metal foil 44. The negative electrode active material layer 45 contains an active material for the negative electrode, a binder, a conductive auxiliary agent, and the like. The negative electrode tab 43 is a portion in which a part of the negative electrode metal foil 44 is extended so as to protrude from the negative electrode main body 42.

The positive electrode electrode 51 includes a positive electrode main body 52 and a positive electrode tab 53. The positive electrode body 52 includes a positive electrode metal foil (aluminum foil in this embodiment) 54 and a positive electrode active material layer 55 provided on both sides of the positive electrode metal foil 54. The positive electrode active material layer 55 contains an active material for the positive electrode, a binder, a conductive auxiliary agent, and the like. The positive electrode tab 53 is a portion in which a part of the positive electrode metal foil 54 is extended so as to protrude from the positive electrode main body 52.

In the lithium ion battery, the capacity of the negative electrode 41 is made larger than the capacity of the positive electrode 51 in order to suppress the precipitation of lithium on the negative electrode 41. Therefore, the area when the negative electrode body 42 is viewed from the front is larger than the area when the positive electrode body 52 is viewed from the front, and the external dimensions of the negative electrode body 42 excluding the thickness are larger than the external dimensions of the positive electrode body 52. First, the negative electrode body 42 will be described.

As shown in FIGS. 3 and 4, the negative electrode main body 42 has a substantially rectangular shape having a short side and a long side when viewed from the front. The negative electrode body 42 includes a negative electrode upper end surface 62 and a negative electrode lower end surface 63, which are surfaces extending in parallel with each other, on the peripheral edge. The negative electrode upper end surface 62 and the negative electrode lower end surface 63 have a rectangular shape. The negative electrode upper end surface 62 and the negative electrode lower end surface 63 are surfaces forming long sides when the negative electrode body 42 is viewed from the front. The negative electrode body 42 includes a pair of negative electrode side end faces 64, 65, which are surfaces extending in parallel with each other, on the peripheral edge. The negative electrode side end faces 64 and 65 are surfaces forming a short side when the negative electrode body 42 is viewed from the front. The negative electrode tab 43 is integrally provided on the upper end surface 62 of the negative electrode.

The negative electrode body 42 includes a negative electrode chamfering portion 66 located between the negative electrode lower end surface 63 and the negative electrode side end surfaces 64, 65 and connecting the negative electrode lower end surface 63 and the negative electrode side end surfaces 64, 65. Two negative electrode chamfered portions 66 are provided. The negative electrode chamfered portion 66 is a surface that diagonally intersects the negative electrode lower end surface 63 with respect to the negative electrode side end surfaces 64 and 65. The peripheral edge of the negative electrode body 42 is composed of the negative electrode upper end surface 62, the negative electrode lower end surface 63, and the negative electrode side end surfaces 64 and 65. The negative electrode chamfered portion 66 of this embodiment has a C-plane shape.

The "negative electrode chamfered portion" is a right angle if there is no negative electrode chamfered portion 66, or is perpendicular to a portion of the electrode assembly 40 facing the bottom wall 23 and the side wall 25 by connecting surfaces that intersect at an acute angle. , It is a surface that prevents acute angles from occurring. The "negative electrode chamfered portion" does not indicate only the surface generated by the actual chamfering, but it is assumed that the negative electrode body 42 having a right angle or an acute angle facing the bottom wall 23 is chamfered. Also includes faces. For example, the negative electrode body 42 in which the negative electrode upper end surface 62, the negative electrode lower end surface 63, the negative electrode side end surfaces 64 and 65, and the negative electrode chamfered portion 66 are simultaneously manufactured by cutting, and the negative electrode body 42 is not actually chamfered. The surface that diagonally intersects the negative electrode lower end surface 63 and the negative electrode side end surfaces 64 and 65 corresponds to the negative electrode chamfered portion 66.

The positive electrode body 52 has a substantially rectangular shape having a short side and a long side when viewed from the front. The positive electrode body 52 includes a positive electrode upper end surface 72 and a positive electrode lower end surface 73, which are surfaces extending in parallel with each other, on the peripheral edge. The positive electrode upper end surface 72 and the positive electrode lower end surface 73 have a rectangular shape. The positive electrode upper end surface 72 and the positive electrode lower end surface 73 are surfaces forming long sides when the positive electrode body 52 is viewed from the front. The positive electrode body 52 is provided with a pair of positive electrode side end faces 74 and 75, which are surfaces extending in parallel with each other, on the peripheral edge. The positive electrode side end faces 74 and 75 are surfaces forming a short side when the positive electrode body 52 is viewed from the front. The positive electrode tab 53 is integrally provided on the upper end surface 72 of the positive electrode.

The positive electrode body 52 includes a positive electrode chamfered portion 76 that is located between the lower end surface 73 of the positive electrode and the end faces 74 and 75 on the positive electrode side and connects the lower end surface 73 of the positive electrode and the end faces 74 and 75 on the positive electrode side. Two positive electrode chamfered portions 76 are provided. The positive electrode chamfered portion 76 is a surface that diagonally intersects the lower end surface 73 of the positive electrode with respect to the end surfaces 74 and 75 on the positive electrode side. The peripheral edge of the positive electrode body 52 is composed of the positive electrode upper end surface 72, the positive electrode lower end surface 73, and the positive electrode chamfered portion 76. The positive electrode chamfered portion 76 of this embodiment has a C-plane shape.

The "positive electrode chamfered portion" is a right angle if there is no positive electrode chamfered portion 76, or is perpendicular to a portion of the electrode assembly 40 facing the bottom wall 23 and the side wall 25 by connecting surfaces that intersect at an acute angle. , It is a surface that prevents acute angles from occurring. The "positive electrode chamfered portion" does not indicate only the surface generated by actually chamfering, but it is assumed that the positive electrode main body 52 having a right angle or an acute angle facing the bottom wall 23 is chamfered. Also includes faces. For example, the positive electrode main body 52 in which the positive electrode upper end surface 72, the positive electrode lower end surface 73, the positive electrode side end surfaces 74 and 75, and the positive electrode chamfered portion 76 are simultaneously manufactured by cutting, and are not actually chamfered. The surface that diagonally intersects the positive electrode lower end surface 73 and the positive electrode side end surfaces 74 and 75 corresponds to the positive electrode chamfered portion 76.

As shown in FIG. 4, the dimension L21 in the longitudinal direction of the positive electrode upper end surface 72 (the direction in which the positive electrode side end faces 74 and 75 face each other) is the longitudinal direction of the negative electrode upper end surface 62 (the directions in which the negative electrode side end faces 64 and 65 face each other). It is shorter than the dimension L11 of. The dimension L22 in the longitudinal direction of the positive electrode lower end surface 73 (the direction in which the positive electrode side end faces 74 and 75 face each other) is shorter than the dimension L12 in the longitudinal direction of the negative electrode lower end surface 63 (the direction in which the negative electrode side end faces 64 and 65 face each other). .. The dimensions L23 and L24 in the longitudinal direction of the positive electrode side end faces 74 and 75 (the direction in which the positive electrode upper end surface 72 and the positive electrode lower end surface 73 face each other) are the longitudinal directions of the negative electrode side end faces 64 and 65 (negative electrode upper end surface 62 and below the negative electrode). It is shorter than the dimensions L13 and L14 (in the direction in which the end face 63 faces each other).

As shown in FIG. 3, the bag-shaped separator 81 includes two separator pieces 82 as separators. Each separator piece 82 has the same shape. The separator piece 82 has a rectangular shape. The peripheral edges of the two separator pieces 82 are joined by welding or the like. As a result, the storage space is partitioned inside the joined portion of the two separator pieces 82. The positive electrode 51 is housed in the bag-shaped separator 81. A part of the positive electrode tab 53 protrudes from the bag-shaped separator 81.

As shown in FIG. 4, the bag-shaped separator 81 includes a separator upper end surface 83 and a separator lower end surface 84 that are parallel to each other, and a pair of separator side end surfaces 85 that are parallel to each other. The dimension L31 in the longitudinal direction of the separator upper end surface 83 (the direction in which the separator side end faces 85 face each other) and the dimension L32 in the longitudinal direction of the separator lower end surface 84 (the direction in which the separator side end faces 85 face each other) are the same. The dimensions L33 of each separator side end surface 85 in the longitudinal direction (direction in which the separator upper end surface 83 and the separator lower end surface 84 face each other) are the same. The angle C1 connecting the upper end surface 83 of the separator and the end surface 85 on the separator side and the angle C2 connecting the lower end surface 84 of the separator and the end surface 85 on the separator side are right angles.

Since the bag-shaped separator 81 is formed by welding separator pieces 82 having the same shape, the upper end surface 83 of the separator, the lower end surface 84 of the separator, and the end surface 85 on each separator side are the end surfaces of the separator pieces 82. It is composed of being continuous with. That is, each of the separator pieces 82 has a separator upper end surface, a separator lower end surface, and each separator side end surface, and by connecting these, the separator upper end surface 83, the separator lower end surface 84, and each of the bag-shaped separator 81. The separator side end face 85 can also be regarded as forming each separator piece 82.

The external dimensions of the bag-shaped separator 81 excluding the thickness are equal to or larger than the external dimensions of the negative electrode electrode 41 when it is assumed that the negative electrode chamfered portion 66 is not provided, and are the same in the present embodiment. The longitudinal dimension L31 of the separator upper end surface 83 and the longitudinal dimension L32 of the separator lower end surface 84 are the same as the longitudinal dimension L11 of the negative electrode upper end surface 62. The dimension L33 in the longitudinal direction of the separator side end surface 85 is the same as the distance L15 between the negative electrode upper end surface 62 and the negative electrode lower end surface 63.

As shown in FIG. 3, the positive electrode electrode 51 is formed on the bag-shaped separator 81 in a state where the upper end surface 83 of the separator and the upper end surface 72 of the positive electrode face the same direction, and the lower end surface 84 of the separator and the lower end surface 73 of the positive electrode face the same direction. It is stored.

As shown in FIGS. 5 and 6, the electrode assembly 40 is configured by alternately stacking the negative electrode 41 and the positive electrode 51 housed in the bag-shaped separator 81. In the following description, the "stacking direction" means the stacking direction of the negative electrode 41 and the positive electrode 51.

The negative electrode 41 and the positive electrode 51 are insulated from each other by the bag-shaped separator 81. The lower end surface 63 of the negative electrode, the lower end surface 73 of the positive electrode, and the lower end surface 84 of the separator face in the same direction. The negative electrode upper end surface 62, the positive electrode upper end surface 72, and the separator upper end surface 83 face in the same direction. When viewed from the stacking direction of the positive electrode 51 and the negative electrode 41, the corner C2 of the bag-shaped separator 81 projects outward from the negative electrode chamfered portion 66.

Since the external dimensions of the negative electrode body 42 and the external dimensions of the bag-shaped separator 81 are the same except for the thickness, the negative electrode body 42 and the bag-shaped separator 81 face each other as a whole when viewed from the stacking direction. It can be said that the outer shape of the negative electrode body 42 is contained within the outer shape of the bag-shaped separator 81 when viewed from the stacking direction. In other words, the negative electrode body 42 is projected into the region of the bag-shaped separator 81 when viewed from the stacking direction.

The outer surface of the electrode assembly 40 is formed by connecting a negative electrode 41 and a bag-shaped separator 81. By providing the negative electrode chamfered portion 66 on the negative electrode electrode 41, the electrode assembly 40 is provided with a chamfered portion in which the negative electrode chamfered portions 66 are connected as a whole. The negative electrode upper end surface 62 and the separator upper end surface 83 are arranged in the stacking direction, and the negative electrode lower end surface 63 and the separator lower end surface 84 are arranged in the stacking direction. The negative electrode side end faces 64 and 65 and the separator side end faces 85 are aligned in the stacking direction.

As shown in FIGS. 1 and 2, the electrode assembly 40 is housed in the case 20 so that the negative electrode lower end surface 63, the positive electrode lower end surface 73, and the separator lower end surface 84 face the bottom wall 23 via the insulating sheet 30. Has been done. The lower end surface 63 of the negative electrode serves as the first negative electrode surface, and the lower end surface 84 of the separator serves as the first separator surface. The lower end surface 73 of the positive electrode is the first positive electrode surface.

The negative electrode side end faces 64 and 65 and the separator side end face 85 face the first side portion 26 via the insulating sheet 30. The positive electrode side end faces 74 and 75 face the first side portion 26 via the bag-shaped separator 81 and the insulating sheet 30. The negative electrode side end faces 64 and 65, the separator side end face 85, and the positive electrode side end faces 74 and 75 extend in the stacking direction. The negative electrode side end faces 64 and 65 serve as the second negative electrode surface, and the separator side end face 85 serves as the second separator face. The positive electrode side end faces 74 and 75 are the second positive electrode faces.

The negative electrode chamfered portion 66 faces the corner portion 24 of the case. The corner C2 of the bag-shaped separator 81 is located on the inner surface side of the case 20 (case corner portion 24) with respect to the negative electrode chamfered portion 66. When viewed from the stacking direction, the corner C2 of the bag-shaped separator 81 is located between the negative electrode chamfered portion 66 and the insulating sheet 30 covering the case corner portion 24. Here, the radius R1 of the inner surface of the case corner portion 24 is smaller than the dimension obtained by adding the thickness T of the insulating sheet 30 to the chamfering dimension L41 of the negative electrode chamfered portion 66. The chamfer dimension L41 of the negative electrode chamfered portion 66 is from the angle C11 where the extension line of the negative electrode lower end surface 63 and the extension line of the negative electrode side end faces 64, 65 intersect to the negative electrode lower end surface 63 (or the negative electrode side end faces 64, 65). It is the dimension of. By setting the chamfer dimension L41 of the negative electrode chamfered portion 66 as described above, a gap is easily maintained between the negative electrode chamfered portion 66 and the insulating sheet 30.

Next, the operation of the secondary battery 10 will be described.
When an impact or vibration is applied to the secondary battery 10, a load is applied to the insulating sheet 30 from the lower end surface 63 of the negative electrode. At this time, when a right-angled or acute-angled corner is formed by the negative electrode lower end surface 63 and the negative electrode side end surfaces 64 and 65, the insulating sheet 30 is sandwiched between the corner and the bottom wall 23 and comes into contact with the corner of the insulating sheet 30. The load tends to concentrate on the part.

In the present embodiment, since the negative electrode chamfered portion 66 connecting the negative electrode lower end surface 63 and the negative electrode side end surfaces 64 and 65 is provided, the negative electrode lower end surface 63 and the negative electrode side end surfaces 64 and 65 have a right angle or an acute angle. No corners are formed. As a result, the insulating sheet 30 is prevented from being sandwiched between the right-angled or acute-angled portion and the case 20.

As shown in FIG. 7, when viewed from the stacking direction, the corner C2 of the bag-shaped separator 81 projects toward the inner surface side of the case 20 with respect to the negative electrode chamfered portion 66. The portion of the bag-shaped separator 81 that protrudes toward the inner surface side of the case 20 from the negative electrode chamfered portion 66 bends in the stacking direction and covers the negative electrode chamfered portion 66 of the adjacent negative electrode electrode 41. By interposing the bag-shaped separator 81 between the negative electrode chamfered portion 66 and the insulating sheet 30, when a force is applied to the insulating sheet 30 from the negative electrode chamfered portion 66, the insulating sheet 30 is interposed via the bag-shaped separator 81. Will be added to the force. The bag-shaped separator 81 is softer than the negative electrode electrode 41, and the bag-shaped separator 81 functions as a cushion.

Although the operation of the secondary battery 10 when an impact or vibration is applied to the secondary battery 10 has been described, a load is applied from the negative electrode electrode 41 to the insulating sheet 30 due to the expansion of the negative electrode electrode 41 due to the charging and discharging of the secondary battery 10. The same effect occurs when is added.

Therefore, according to the above embodiment, the following effects can be obtained.
(1) The negative electrode electrode 41 includes a negative electrode chamfered portion 66. Even if the negative electrode chamfered portion 66 comes into contact with the insulating sheet 30 due to the movement of the electrode assembly 40 in the case 20, the load concentration is less than when the right-angled or acute-angled portion comes into contact with the insulating sheet 30. Therefore, damage to the insulating sheet 30 is suppressed.

Further, a part of the bag-shaped separator 81 is interposed between the negative electrode chamfered portion 66 and the insulating sheet 30. Since the force applied to the insulating sheet 30 from the negative electrode chamfered portion 66 is reduced by the separator piece 82, damage to the insulating sheet 30 is further suppressed. Therefore, the insulation between the case 20 and the electrode assembly 40 is easily maintained, and the short circuit between the case 20 and the electrode assembly 40 is suppressed.

(2) The positive electrode electrode 51 includes a positive electrode chamfered portion 76. Similar to the case of the negative electrode 41, damage to the insulating sheet 30 is suppressed by the corners of the positive electrode 51 as the electrode assembly 40 moves in the case 20. Further, by providing the positive electrode chamfered portion 76, the volume ratio between the negative electrode electrode 41 and the positive electrode electrode 51 can be easily maintained.

(3) The gap between the insulating sheet 30 and the negative electrode chamfered portion 66 is easily maintained. Therefore, it is possible to prevent the negative electrode chamfered portion 66 from coming into contact with the insulating sheet 30, and it is possible to further suppress damage to the insulating sheet 30.

The embodiment may be changed as follows.
The radius R1 of the inner surface of the corner portion 24 of the case may be equal to or larger than the chamfer dimension L41 of the negative electrode chamfered portion 66 plus the thickness T of the insulating sheet 30. Even in this case, the insulating sheet 30 is less likely to be damaged as compared with the case where a right-angled or acute-angled portion is in contact with the insulating sheet 30.

○ The positive electrode electrode 51 does not have to include the positive electrode chamfered portion 76. That is, the lower end surface 73 of the positive electrode and the end surfaces 74 and 75 on the positive electrode side may intersect at right angles. In the lithium ion battery, the external dimensions of the positive electrode 51 are smaller than the external dimensions of the negative electrode 41. Since the positive electrode 51 is less likely to come into contact with the insulating sheet 30 than the negative electrode 41, damage to the insulating sheet 30 can be suppressed even if the positive electrode 51 does not include the positive electrode chamfered portion 76.

○ As shown in FIG. 8, the negative electrode chamfered portion 66 may have a rounded shape that bulges toward the inner surface of the case corner portion 24. In this case, the chamfered dimension is the radius R2 of the negative electrode chamfered portion 66. The radius of the inner surface of the case corner 24 may be smaller than the radius of the negative electrode chamfered portion 66 plus the thickness T of the insulating sheet 30.

The negative electrode electrode 41 may be provided with a chamfered portion located between the negative electrode upper end surface 62 and the negative electrode side end surfaces 64, 65 and connecting the negative electrode upper end surface 62 and the negative electrode side end surfaces 64, 65. Further, the positive electrode electrode 51 may be provided with a chamfered portion located between the positive electrode upper end surface 72 and the positive electrode side end surfaces 74 and 75 and connecting the positive electrode upper end surface 72 and the positive electrode side end surfaces 74 and 75.

○ A part of the plurality of negative electrode electrodes 41 may not be provided with the negative electrode chamfered portion 66. Even in this case, damage to the insulating sheet 30 can be suppressed as compared with the case where all the negative electrode electrodes 41 do not have the negative electrode chamfered portion 66.

The shape of the case 20 may be any shape as long as it can accommodate the electrode assembly 40.
○ The inner surface of the corner 24 of the case is not limited to a rounded shape, but may be a right angle shape or the like.

○ The negative electrode active material layer 45 may be provided only on one surface of the negative electrode metal foil 44. The positive electrode active material layer 55 may be provided only on one surface of the positive electrode metal foil 54.
○ The external dimensions of the negative electrode body 42 and the positive electrode body 52 may be the same.

○ Separator pieces 82 may not be welded to each other.
○ The power storage device may be a capacitor.

C2 ... corner, 10 ... secondary battery (power storage device), 20 ... case, 23 ... bottom wall, 24 ... case corner, 25 ... side wall, 30 ... insulating sheet, 40 ... electrode assembly, 41 ... negative electrode electrode, 42 ... Negative electrode body, 43 ... Negative electrode tab, 44 ... Negative electrode metal foil, 45 ... Negative electrode active material layer, 51 ... Positive electrode, 52 ... Positive electrode body, 53 ... Positive electrode tab, 54 ... Positive electrode metal foil, 55 ... Positive electrode active material layer, 63 ... Negative electrode lower end surface (first negative electrode surface), 64, 65 ... Negative electrode side end surface (second negative electrode surface), 66 ... Negative electrode chamfered portion, 73 ... Positive electrode lower end surface (first positive electrode surface), 74, 75 ... Positive electrode Side end surface (second positive electrode surface), 76 ... positive electrode chamfered portion, 82 ... separator piece (separator), 84 ... separator lower end surface (first separator surface), 85 ... separator side end surface (second separator surface).

Claims (5)

An electrode assembly in which a plurality of positive electrodes and a plurality of negative electrodes are alternately laminated in a state of being insulated by a separator arranged between the positive electrode and the negative electrode.
A case containing the electrode assembly and
An insulating sheet that is interposed between the electrode assembly and the case and that insulates the electrode assembly and the case is provided.
The case includes a bottom wall, a side wall, and a case corner connecting the bottom wall and the side wall.
The negative electrode includes a negative electrode body provided with a negative electrode active material layer on the negative electrode metal foil, and a negative electrode tab composed of the negative electrode metal foil and extending from the negative electrode body.
The negative electrode body includes a first negative electrode surface facing the bottom wall via the insulating sheet, a second negative electrode surface facing the side wall via the insulating sheet, the first negative electrode surface, and the second negative electrode surface. A negative electrode chamfering portion that connects the first negative electrode surface and the second negative electrode surface and faces the corner of the case via the insulating sheet is provided between the two.
The separator includes a first separator surface facing the bottom wall via the insulating sheet, and a second separator surface facing the side wall via the insulating sheet and connecting to the first separator surface.
The outer shape of the negative electrode body fits within the outer shape of the separator when viewed from the stacking direction of the positive electrode and the negative electrode.
There is a gap between the insulating sheet and the negative electrode chamfered portion,
A power storage device in which the angle at which the first separator surface and the second separator surface are connected is located in the gap and covers the negative electrode chamfered portion. The positive electrode includes a positive electrode body provided with a positive electrode active material layer on the positive electrode metal foil, and a positive electrode tab composed of the positive electrode metal foil and extending from the positive electrode body.
The positive electrode body includes a first positive electrode surface facing the bottom wall via the insulating sheet, a second positive electrode surface facing the side wall via the insulating sheet, and a first positive electrode surface and the second positive electrode surface. The power storage device according to claim 1, further comprising a positive electrode chamfering portion that connects the first positive electrode surface and the second positive electrode surface and faces the corner of the case via the insulating sheet. The inner surface of the corner of the case is rounded and has a rounded shape.
The negative electrode chamfered portion has a rounded shape that bulges toward the inner surface of the corner of the case.
The power storage device according to claim 1 or 2, wherein the radius of the inner surface of the corner of the case is smaller than the radius of the negative electrode chamfered portion plus the thickness of the insulating sheet. Of the angles connecting the first separator surface and the second separator surface, a portion protruding toward the inner surface side of the case from the negative electrode chamfered portion is bent in the stacking direction, and the adjacent negative electrode electrode is said to have the same angle. The power storage device according to any one of claims 1 to 3, which covers the negative electrode chamfered portion. The case has a body comprising the bottom wall, the side walls, and the corners of the case.
The power storage device according to any one of claims 1 to 4, wherein the insulating sheet is along the inner surface of the main body.

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