Energy storage element

Abstract

To provide a power storage element which can prevent short circuiting in an active material non-formation part.SOLUTION: A power storage element comprises: a first electrode sheet; and a second electrode sheet having a polarity different from that of the first electrode sheet. The first electrode sheet comprises: metal foil which has an edge extending in a first direction and a first tab protruding from the edge in a second direction intersecting the first direction; an active material layer formed on a surface of the metal foil; and an insulating layer formed on the surface of the metal foil. A portion, of the metal foil, along the edge and the first tab are provided as an active material non-formation part where the active material layer is not formed. The insulating layer is provided in a region including a portion, of the active material non-formation part, along the edge and a base of the first tab. The insulating layer provided in the portion along the edge and in the base is aligned with the active material layer in the second direction, and is continuous with it in an integral manner. The first tab is bent at the base where the insulating layer is provided. A tip-side portion of the first tab extends along a direction perpendicular to the first direction and the second direction.SELECTED DRAWING: Figure 5

Description

[Technical field]

[0001] The present invention relates to an electric storage element having a positive electrode sheet and a negative electrode sheet stacked with a separator interposed therebetween. [Background technology]

[0002] In a storage element such as a lithium ion battery, an electrode assembly having positive and negative electrode sheets alternately stacked with a separator interposed therebetween may be used. In general, the positive and negative electrode sheets are formed by coating active material layers on both sides of a metal foil.

[0003] As disclosed in Patent Document 1, the positive electrode sheet and the negative electrode sheet of the energy storage element may be provided with a tab that protrudes outward in the width direction from a linear edge on one side of the sheet in the width direction. At least a part of the tab is an active material non-forming part where no active material layer is formed, and the active material non-forming part is electrically connected to an external terminal via a current collector.

[0004] In this type of energy storage element, the positive electrode sheet may have an active material non-forming portion formed not only on the tab but also along the edge of the tab side. Furthermore, the active material non-forming portion formed along the edge of the positive electrode sheet in this manner may be disposed opposite the active material layer of the negative electrode sheet via a separator. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 5354042 Summary of the Invention [Problem to be solved by the invention]

[0006] However, in an energy storage element in which the active material non-forming portion formed along the tab side edge of the positive electrode sheet as described above is disposed opposite the negative electrode active material layer via a separator, if the positive electrode active material non-forming portion and the negative electrode active material layer come to face each other directly due to some cause such as misalignment, shrinkage, or breakage of the separator, a short circuit may occur between them.

[0007] Therefore, an object of the present invention is to suppress the occurrence of short circuits in an active material non-forming portion in an energy storage element in which an active material non-forming portion is provided along the edge portion on the tab side of an electrode sheet. [Means for solving the problem]

[0008] The present invention provides an energy storage element comprising a first electrode sheet and a second electrode sheet laminated on the first electrode sheet via a separator and having a polarity different from that of the first electrode sheet, the first electrode sheet comprising a metal foil having an edge portion extending in a first direction and a first tab protruding from the edge portion in a second direction intersecting the first direction, an active material layer formed on a surface of the metal foil, and an insulating layer formed on the surface of the metal foil, and the portion of the metal foil along the edge portion and the first tab are formed on the active material layer. the insulating layer is provided in a region including a portion along the edge of the active material non-forming portion and a base of the first tab, the insulating layer provided on the portion along the edge and on the base is arranged side by side with the active material layer in the second direction and is connected to the active material layer as a single unit, the first tab is bent at the base on which the insulating layer is provided, and a tip portion of the first tab extends along a direction perpendicular to the first direction and the second direction. Alternatively, the present invention provides an energy storage element including an electrode body, the electrode body including a first electrode sheet and a second electrode sheet having a polarity different from that of the first electrode sheet, the first electrode sheet including a metal foil, an active material layer provided on the metal foil, and an insulating layer provided on the metal foil, the metal foil including an active material non-forming portion where the active material layer is not provided, the active material non-forming portion including a first active material non-forming portion extending along an edge of the metal foil in a predetermined direction, and an insulating layer protruding from the first active material non-forming portion. the insulating layer is provided in a region including a portion along the edge of the active material non-forming portion and a base of the first tab, the insulating layer provided on the portion along the edge and on the base is arranged side by side with the active material layer in the specified direction and is integrally connected to the active material layer, the first tab is bent at the base on which the insulating layer is provided, and a tip portion of the first tab extends in a direction along the edge and in a direction perpendicular to the specified direction.

[0009] As a result, even if the first electrode sheet comes directly opposite the second electrode sheet due to misalignment, shrinkage, or damage of the separator, the occurrence of a short circuit in the active material non-forming portion of the first electrode sheet can be suppressed by interposing an insulating layer between the active material non-forming portion of the first electrode sheet and the second electrode sheet.

[0010] In the present invention, the insulating layer is preferably provided in a region of the active material non-forming portion including the base of the first tab, thereby making it possible to suppress the occurrence of a short circuit at the base of the first tab and to reinforce the base with the insulating layer.

[0011] In the present invention, it is preferable that the first tab has a radius at the base, which can disperse stress on the base of the first tab and improve the strength of the first tab.

[0012] When the energy storage element according to the present invention further includes a current collector that electrically connects the first electrode sheet to an external terminal, the first tab may be connected to the current collector in a folded state. In this case, the base of the first tab, where stress is concentrated due to bending, is reinforced by an insulating layer, thereby improving the rigidity and durability of the first tab.

[0013] In the present invention, it is preferable that the portion of the insulating layer formed on the surface of the first tab protrudes beyond the edge of the separator in the second direction. With this, even if the first tab faces the second electrode sheet without a separator therebetween due to misalignment, shrinkage, breakage, or the like of the separator, the insulating layer is interposed between the metal foil of the first tab and the second electrode sheet, thereby making it possible to suppress the occurrence of a short circuit in the first tab.

[0014] In the present invention, it is preferable that the insulating layer is also formed on the end face of the metal foil in the active material non-forming portion. This makes it possible to more effectively suppress the occurrence of a short circuit in the active material non-forming portion of the first electrode sheet. In addition, since the end face of the edge of the first electrode sheet is covered with the insulating layer, it is easy to arrange the edge of the first electrode sheet close to the edge of the separator located outside the edge of the first electrode sheet in the second direction while suppressing a short circuit at the end face of the edge. Therefore, the first electrode sheet can be expanded in the second direction, and the battery capacity can be increased.

[0015] In the present invention, when the second electrode sheet has an edge portion extending linearly in the first direction and a second tab extending from the edge portion in the second direction, the first tab and the second tab may protrude to the same side in the second direction and be spaced apart in the first direction. In this case, the above-mentioned effects can be obtained in this type of energy storage element.

[0016] In the present invention, when the first electrode sheet includes a plurality of the first tabs arranged at intervals in the first direction, and the first electrode sheet and the second electrode sheet are stacked on each other with the separator interposed therebetween and wound around an axis parallel to the second direction to form a wound body, the wound body may include a first tab bundle formed by stacking the plurality of first tabs. In this case, the rigidity of the base of the first tab is increased by the insulating layer, so that when the first electrode sheet is wound, the first tab is prevented from bending in the thickness direction of the first electrode sheet. Therefore, when the first electrode sheet is wound to stack the plurality of first tabs, the first tabs are less likely to get caught on each other, and thus bending of each first tab is prevented.

[0017] In the present invention, when the wound body includes a pair of flat portions extending linearly parallel to each other when viewed from the direction in which the axis extends, and a pair of curved portions connecting the pair of flat portions, the first tab bundle may be provided on the flat portions. In this case, the above-mentioned effect can be obtained in this type of energy storage element.

[0018] When the energy storage device according to the present invention includes a laminate in which a plurality of the first electrode sheets and a plurality of the second electrode sheets are alternately laminated with the separators interposed therebetween, the laminate may include a first tab bundle in which the first tabs provided on the plurality of first electrode sheets are laminated together. In this case, the above-mentioned effects can be obtained in this type of energy storage device. Effect of the Invention

[0019] According to the present invention, even if the first electrode sheet comes directly opposite the second electrode sheet due to misalignment, shrinkage, or damage of the separator, the occurrence of a short circuit in the active material non-forming portion of the first electrode sheet can be suppressed by interposing an insulating layer between the active material non-forming portion of the first electrode sheet and the second electrode sheet. [Brief description of the drawings]

[0020] [Figure 1] 1 is a perspective view showing an energy storage element according to an embodiment of the present invention; [Diagram 2] 2 is a partially cutaway perspective view taken along line AA in FIG. 1 and showing the inside of the energy storage element. [Diagram 3] 2 is a perspective view of an electrode body of the energy storage element shown in FIG. 1. [Figure 4] FIG. 4 is a development view of the electrode body shown in FIG. [Diagram 5] 5 is an enlarged view of FIG. 4 showing the positive electrode tab of the positive electrode sheet and its surrounding area. [Figure 6] 6 is a cross-sectional view taken along line BB in FIG. 5, showing a first insulating portion of an insulating layer of the positive electrode sheet and its peripheral portion, viewed from the longitudinal direction of the positive electrode sheet. [Figure 7] 6 is a cross-sectional view taken along line CC in FIG. 5, showing a second insulating portion of the insulating layer of the positive electrode sheet and its peripheral portion, viewed from the longitudinal direction of the positive electrode sheet. [Figure 8] 6 is a cross-sectional view taken along line DD in FIG. 5, showing a second insulating portion of the insulating layer of the positive electrode sheet and its surrounding area, viewed from the protruding direction of the positive electrode tab. [Figure 9] 13 is an exploded perspective view showing a schematic diagram of an electrode body of an energy storage element according to another embodiment of the present invention. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0021] Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings. Note that terms including "up" and "down" used to indicate directions in this specification and terms indicating directions related thereto indicate directions in the attitude of the energy storage element illustrated in the accompanying drawings, and do not necessarily coincide with directions in an actual state of use.

[0022] 1 shows an energy storage device 1 according to an embodiment of the present invention. The energy storage device 1 is, for example, a non-aqueous electrolyte secondary battery such as a lithium ion battery. However, the present invention can be applied to various energy storage devices including capacitors other than lithium ion batteries.

[0023] 1, the energy storage device 1 has, for example, a substantially rectangular parallelepiped case 2. The case 2 has a case body 3 having an upper opening, and a lid 4 that closes the upper opening of the case body 3.

[0024] Metal such as aluminum or an aluminum alloy is used as the material of the case body 3. The surface of the case body 3 may be entirely covered with an insulating layer (not shown) made of, for example, resin.

[0025] The lid 4 is, for example, a rectangular metal plate. The lid 4 is welded to the edge of the opening of the case body 3. On the surface of the lid 4, an external positive terminal 11 and an external negative terminal 12 are fixed.

[0026] The external terminals 11, 12 are fixed, for example, by crimping, to the upper surface of the lid 4 via an upper gasket 13. The external terminals 11, 12 are made of a material such as aluminum, copper, nickel, or the like.

[0027] The lid 4 is provided with a gas exhaust valve 8 for exhausting gas generated in the case body 3 to the outside of the case 2, and a liquid filling port (not shown). The liquid filling port is closed by a liquid filling plug 10.

[0028] As shown in FIG. 2, the case 2 contains at least one electrode body 20 (corresponding to the "wound body" in the claims), a current collector 15 that electrically connects the electrode body 20 to the positive and negative external terminals 11, 12, and an electrolyte (not shown).

[0029] The current collector 15 shown in FIG. 2 is a positive electrode current collector connected to the positive electrode external terminal 11, and the following description with reference to FIG. 2 will focus on the configuration of the positive electrode current collector 15, and the illustration and description of the negative electrode current collector connected to the negative electrode external terminal 12 will be omitted.

[0030] The negative electrode current collector is configured similarly to the positive electrode current collector 15 described below, but may have a different configuration from the positive electrode current collector 15. The positive electrode current collector 15 and the negative electrode current collector may be configured from different materials. Specifically, the material of the positive electrode current collector 15 is, for example, a metal such as aluminum, and the material of the negative electrode current collector is, for example, a metal such as copper.

[0031] The current collector 15 is fixed to the lower surface of the lid 4 by, for example, crimping via a lower gasket 14. The current collector 15 includes, for example, a first flat plate portion 15a fixed to the lid 4, a connecting portion 15b extending downward while curving from an edge portion of the first flat plate portion 15a, and a second flat plate portion 15c connected to the first flat plate portion 15a via the connecting portion 15b and disposed below and facing the first flat plate portion 15a.

[0032] The first flat plate portion 15a is electrically connected to the external terminal 11, for example, via a rivet portion (not shown) extending downward from the external terminal 11. A tab 35 (described later) provided on the electrode body 20 is joined to the lower surface of the second flat plate portion 15c, for example, by ultrasonic welding, and is thereby electrically connected to the electrode body 20.

[0033] 3 and 4, the electrode body 20 is formed by stacking a positive electrode sheet (corresponding to the "first electrode sheet" in the claims) 21, a negative electrode sheet 22 (corresponding to the "second electrode sheet" in the claims), and two separators 23, 23 made of a microporous resin sheet, all of which are long strips of a constant width, and winding them into an elliptical shape with a high flatness. One of the two separators 23, 23 is interposed between one layer of the positive electrode sheet 21 and one layer of the negative electrode sheet 22 adjacent thereto. The separators 23, 23 are longer than the positive electrode sheet 21 and the negative electrode sheet 22. As a result, the outermost layer of the electrode body 20 is formed by one of the separators 23.

[0034] The winding axis (winding axis) of the positive electrode sheet 21, the negative electrode sheet 22, and the two separators 23, 23 is conceptually indicated by the symbol X in Fig. 3. The electrode body 20 is housed in the case body 3 with the winding axis X extending generally in the direction in which the bottom wall and the top opening of the case body 3 shown in Fig. 1 face each other (the up-down direction in Fig. 1).

[0035] 3, each end of the electrode body 20 in the direction in which the winding axis X extends is an end surface portion 20a, 20b where the widthwise (short-side) ends of the positive electrode sheet 21, the negative electrode sheet 22, and the separators 23, 23 are disposed. The electrode body 20 is disposed opposite each other across the winding axis X and has a pair of flat portions 20c, 20c that extend linearly and parallel to each other when viewed from the direction in which the winding axis X extends, and a pair of curved portions 20d, 20d that extend in a semicircular curve when viewed from the direction in which the winding axis X extends and connect the pair of flat portions 20c, 20c.

[0036] The flat portion 20c is designed to extend linearly. When the electrode body 20 is actually housed in the case 2, the flat portion 20c is not necessarily arranged in a completely straight line, and may be arranged in a bent state so as to have a shape close to a straight line overall.

[0037] As shown in Figs. 3 and 4, the positive electrode sheet 21 includes a strip-shaped positive electrode metal foil 24 and a positive electrode active material layer 25 formed on both sides of the positive electrode metal foil 24. The edges of the positive electrode metal foil 24 on both sides in the width direction (short side direction) are formed so as to extend linearly along the longitudinal direction of the positive electrode metal foil 24. On one side (lower side in Figs. 3 and 4) of the positive electrode metal foil 24 in the width direction, the positive electrode active material layer 25 is provided up to the edge of the positive electrode metal foil 24. On the edge of the other side (upper side in Figs. 3 and 4) of the positive electrode metal foil 24 in the width direction, a first active material non-formed portion 34 is provided in which the positive electrode metal foil 24 is exposed without providing the positive electrode active material layer 25. The first active material non-formed portion 34 of the positive electrode metal foil 24 is covered with an insulating layer 40 (see Figs. 5 to 8) described later. Note that the insulating layer 40 is not shown in Fig. 3.

[0038] The material of the positive electrode metal foil 24 is, for example, aluminum, but other metals may be used. As the positive electrode active material, for example, lithium manganese oxide (LiMn2O4), lithium nickel cobalt manganese oxide (LiNixCoyMn1-x-yO2), lithium cobalt oxide (LiCoO2), lithium nickel oxide (LiNiO2), lithium iron phosphate (LiFePO4), lithium manganese phosphate (LiMnPO4), or a substitute additive or a mixture of these may be used, but other lithium-containing transition metal oxides may also be used.

[0039] The negative electrode sheet 22 includes a strip-shaped negative electrode metal foil 26 and a negative electrode active material layer 27 formed on both sides of the negative electrode metal foil 26. The edges of the negative electrode metal foil 26 on both sides in the width direction (short side direction) are formed to extend linearly along the longitudinal direction of the negative electrode metal foil 26. On both sides in the width direction of the negative electrode metal foil 26 (upper and lower sides in FIGS. 3 and 4 ), the negative electrode active material layer 27 is provided up to the edges of the negative electrode metal foil 26. As a result, each side of the negative electrode metal foil 26 is entirely covered with the negative electrode active material layer 27.

[0040] The material of the negative electrode metal foil 26 is, for example, copper, but other metals may be used. The negative electrode active material is, for example, graphite, but other carbon materials, lithium metal, lithium alloys, lithium titanate (Li4Ti5O12), silicon, silicon monoxide, tin, or other materials capable of absorbing lithium, or mixtures of these, may also be used.

[0041] In the following description, the longitudinal direction of the positive electrode sheet 21, the negative electrode sheet 22, and the separator 23 (the direction of the arrow P in Figs. 4 to 8) is simply referred to as the "longitudinal direction P", the transverse direction of the positive electrode sheet 21, the negative electrode sheet 22, and the separator 23 (the direction of the arrow Q in Figs. 4 to 8) is simply referred to as the "transverse direction Q", and the thickness direction of the positive electrode sheet 21, the negative electrode sheet 22, and the separator 23 (the direction of the arrow R in Figs. 5 to 8) is simply referred to as the "thickness direction R". The longitudinal direction P corresponds to the "first direction" in the claims. The transverse direction Q corresponds to the "second direction" in the claims, and is the width direction parallel to the winding axis X of the electrode body 20 (see Fig. 3).

[0042] 4, in the short-side direction Q of the positive electrode sheet 21 and the negative electrode sheet 22, the width of the negative electrode sheet 22 is greater than the width of the positive electrode sheet 21. The negative electrode sheet 22 protrudes outward beyond the edges of the positive electrode sheet 21 on both sides in the short-side direction Q. The width of the separator 23 is greater than the width of the negative electrode sheet 22. The separator 23 protrudes outward beyond the edges of the negative electrode sheet 22 on both sides in the short-side direction Q.

[0043] 3 and 4, the positive electrode metal foil 24 is provided with a plurality of positive electrode tabs (corresponding to "first tabs" in the claims) 35 at intervals in the longitudinal direction P, which protrude outward in the short-side direction Q from the first active material non-forming portion 34 that extends linearly along an edge portion on one side in the short-side direction Q (the upper side in Figs. 3 and 4). The first active material non-forming portion 34 and the plurality of positive electrode tabs 35 are formed from a single sheet of positive electrode metal foil 24, and each positive electrode tab 35 is integrally connected to the first active material non-forming portion 34. The positive electrode tabs 35 are second active material non-forming portions on the surface of the positive electrode metal foil 24 on which no active material layer is formed.

[0044] As shown in FIG. 5, in the base 35a of the positive electrode tab 35, a radius 35f is provided at the corner between the edge of the positive electrode tab 35 in the longitudinal direction P and the edge of the first active material non-forming portion 34 in the lateral direction Q. The radiuses 35f, 35f are provided at both edges of the base 35a in the longitudinal direction P. As a result, the width of the base 35a in the longitudinal direction P gradually increases toward the first active material non-forming portion 34. By providing such radiuses 35f, 35f, it is possible to disperse stress concentration on the base 35a of the positive electrode tab 35, particularly on the corners, and fracture at the base 35a is suppressed. In other words, the strength of the base 35a of the positive electrode tab 35 is increased.

[0045] 3 and 4, the negative electrode metal foil 26 is also provided with a plurality of negative electrode tabs (corresponding to "second tabs" in the claims) 37 similar to the positive electrode tabs 35. The negative electrode tabs 37 are provided to protrude on the same side as the positive electrode tabs 35 in the short-side direction Q. Most of the negative electrode tabs 37, excluding the base end portion, are active material non-formed portions where no active material layer is formed on the surface of the negative electrode metal foil 26.

[0046] 3, the electrode assembly 20, which is formed by overlapping and winding a positive electrode sheet 21 and a negative electrode sheet 22 with separators 23, 23 between them, includes a positive electrode tab bundle (corresponding to a "first tab bundle" in the claims) 55 formed by stacking a plurality of positive electrode tabs 35. The positive electrode tab bundle 55 is provided on one flat portion 20c of the electrode assembly 20.

[0047] The negative electrode tab 37 is disposed at a distance from the positive electrode tab 35 in the longitudinal direction P, and the positive electrode tab 35 and the negative electrode tab 37 do not overlap each other. In the electrode body 20 in a wound state, the multiple negative electrode tabs 37 are overlapped with each other, thereby forming a negative electrode tab bundle 57 as a second tab bundle.

[0048] The positive electrode tab bundle 55 and the negative electrode tab bundle 57 protrude from one end surface 20a (the upper end surface in FIG. 3) of the electrode body 20. In addition, the positive electrode tab bundle 55 and the negative electrode tab bundle 57 protrude from one side (the front side in FIG. 3) of the pair of flat portions 20c, 20c with respect to a center line Y in the longitudinal direction when the end surface 20a of the electrode body 20 is viewed from the direction in which the winding axis X extends.

[0049] As shown in FIG. 2, the positive electrode tab bundle 55 protruding from one flat portion 20c of the electrode body 20 is connected to the positive electrode current collector 15 in a state where it is bent so as to bend down toward the other flat portion 20c in the thickness direction Z of the electrode body 20 (a direction perpendicular to the winding axis X and the center line Y).

[0050] In this state, each positive electrode tab 35 constituting the positive electrode tab bundle 55 is curved at its base portion (portion extending from the base end to the middle portion) 35a, and the tip portion (portion extending from the tip 35c to the middle portion) 35b of each positive electrode tab 35 faces above the end face portion 20a of the electrode body 20 and is arranged along the underside of the second flat portion 15c of the positive electrode current collector 15.

[0051] The positive electrode tab bundle 55 is joined, for example, by ultrasonic welding, to the lower surface of the second flat plate portion 15c of the positive electrode current collector 15. As a result, each positive electrode tab 35 is electrically connected to the positive electrode external terminal 11 via the positive electrode current collector 15.

[0052] Although not shown, the negative electrode tab 37 is also bent in a similar manner and electrically connected to the negative electrode external terminal 12 (see FIG. 1) via a negative electrode current collector (not shown).

[0053] Hereinafter, the insulating layer 40 of the positive electrode sheet 21 and the related configuration will be described with reference to FIGS.

[0054] 5 is an enlarged view showing the positive electrode tab 35 and its surroundings as viewed from one side of the positive electrode sheet 21. FIG. 6 is a cross-sectional view taken along line BB in FIG. 5 of the first active material non-forming portion 34 and its surroundings in a portion displaced from the positive electrode tab 35 in the longitudinal direction P, as viewed from the longitudinal direction P. FIG. 7 is a cross-sectional view taken along line CC in FIG. 5 of the positive electrode tab 35 and its surroundings as viewed from the longitudinal direction P. FIG. 8 is a cross-sectional view taken along line DD in FIG. 5 of the positive electrode tab 35 and its surroundings as viewed from the protruding direction (short direction Q) of the positive electrode tab 35.

[0055] 6 and 7, in the short-side direction Q, the negative electrode active material layer 27 is disposed so as to protrude outward from the positive electrode active material layer 25. This makes it easier for the negative electrode active material layer 27 to absorb lithium ions released from the positive electrode active material layer 25 during charging when the energy storage element 1 is a lithium ion battery.

[0056] 5 to 8, the insulating layer 40 is provided on the surface of the positive electrode metal foil 24 along one edge of the positive electrode active material layer 25 in the short-side direction Q so as to be adjacent to the edge of the positive electrode active material layer 25. The insulating layer 40 is provided on both sides of the positive electrode metal foil 24. The insulating layer 40 includes a first insulating layer portion 41 provided in the first active material non-forming portion 34 of the positive electrode metal foil 24, and a second insulating layer portion 42 provided in the positive electrode tab 35 which is the second active material non-forming portion.

[0057] 5 and 6, the first insulating layer portion 41 is similarly provided on both surfaces of the first active material non-forming portion 34. On each surface of the first active material non-forming portion 34, the first insulating layer portion 41 is formed along the upper edge portion of the positive electrode active material layer 25 in the short-side direction Q, and covers the upper edge portion of the positive electrode active material layer 25.

[0058] The first insulating layer portion 41 is formed to protrude beyond the upper end surface 24a of the positive electrode metal foil 24 in the short-side direction Q, and covers the upper end surface 24a. The first insulating layer portion 41 is provided over the entire length of the first active material non-forming portion 34 in the longitudinal direction P. As a result, both side surfaces and the upper end surface 24a of the first active material non-forming portion 34 are completely covered by the first insulating layer portion 41.

[0059] 5, the second insulating layer portion 42 is provided in a region including the base portion 35a of the positive electrode tab 35. More specifically, the second insulating layer portion 42 is provided from the base end to the middle portion of the positive electrode tab 35. The tip portion 35b of the positive electrode tab 35 is exposed without being covered by the insulating layer 40, which allows connection to the current collector 15 at the tip portion 35b.

[0060] 7, the second insulating layer portion 42 is similarly provided on both sides of the positive electrode tab 35. On each surface of the positive electrode tab 35, the second insulating layer portion 42 is integrally connected to the outer side of the first insulating layer portion 41 in the short-side direction Q. In the short-side direction Q, the upper edge portion 42a of the second insulating layer portion 42 is located outside the upper edge portion 22a of the negative electrode sheet 22 and the upper edge portion 23a of the separator 23.

[0061] In this manner, by covering the base 35a of the positive electrode tab 35 with the insulating layer 40, the occurrence of a short circuit can be suppressed while the base 35a can be reinforced by the insulating layer 40. Since the positive electrode tab 35 is bent for connection to the current collector 15 as described above (see FIG. 2), stress is likely to concentrate on the base 35a curved by the bending, but by reinforcing the base 35a with the insulating layer 40, the rigidity of the positive electrode tab 35 can be increased, and durability can be improved.

[0062] Furthermore, since the rigidity of the base 35a of the positive electrode tab 35 is increased by the insulating layer 40, bending of the positive electrode tab 35 in the thickness direction R is suppressed when the positive electrode sheet 21 is rolled. Therefore, when the positive electrode sheet 21 is rolled to stack a plurality of positive electrode tabs 35, the positive electrode tabs 35 are less likely to get caught on each other, thereby suppressing bending of each positive electrode tab 35. Furthermore, since the base 35a has the radiuses 35f, 35f as described above, even if tension is applied to the positive electrode sheet 21 during rolling, stress concentration on the base 35a is alleviated, and the strength of the base 35a is further improved.

[0063] 8, the second insulating layer portion 42 of the insulating layer 40 protrudes outward beyond the positive electrode tab 35 on both sides in the longitudinal direction P, and covers both side end faces 35d, 35e of the positive electrode tab 35. As a result, the both side surfaces of the positive electrode tab 35 and both side end faces 35d, 35e of the base 35a of the positive electrode tab 35 are covered by the second insulating layer portion 42.

[0064] The insulating layer 40 is made of an insulating material with high electrical resistivity. A specific material for the insulating layer 40 is, for example, a mixture of inorganic and / or organic particles and a binder. Examples of the inorganic particles include alumina (Al2O3), SiO2, ZrO2, TiO2, and MgO, and examples of the organic particles include polyimide powder. Examples of the binder include polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polyimide, and polyamideimide.

[0065] As shown in FIGS. 6 and 7, the insulating layer 40 is disposed opposite the negative electrode active material layer 27 via the separator 23. In particular, the second insulating layer portion 42 of the insulating layer 40 protrudes from the upper edge portion 23a of the separator 23 in the short-side direction Q. Therefore, even if a portion where the separator 23 is not interposed occurs between the first active material non-forming portion 34 of the positive electrode sheet 21 and the base portion 35a of the positive electrode tab 35 and the negative electrode active material layer 27 due to some cause including displacement, shrinkage, or breakage of the separator 23, and the positive electrode sheet 21 and the negative electrode sheet 22 come into contact with each other, the insulating layer 40 covering the metal portion of the positive electrode sheet 21 is interposed between the metal foil 24 of the first active material non-forming portion 34 and the positive electrode tab 35 and the negative electrode active material layer 27, thereby preventing a short circuit.

[0066] In addition, as shown in Figures 6 and 8, the insulating layer 40 covers not only both sides of the first active material non-forming portion 34 and the base 35a of the positive electrode tab 35, but also the end faces 24a, 35d, and 35e thereof, thereby more effectively suppressing the occurrence of short circuits.

[0067] If a metal such as copper that dissolves at a positive electrode potential is mixed onto the positive electrode metal foil 24, the metal will dissolve on the positive electrode metal foil 24. The dissolved metal will deposit on the negative electrode sheet 22, and if the metal deposit grows and comes into contact with the positive electrode sheet 21, it will cause a short circuit.

[0068] However, according to the present embodiment, as shown in Figures 6 and 7, the positive metal foil 24 is covered with an insulating layer 40, thereby preventing dissolution of metal on the positive metal foil 24 located in the vicinity of the negative electrode sheet 22, and thus suppressing metal precipitation on the negative electrode sheet 22, thereby preventing short circuits caused by metal precipitation.

[0069] Furthermore, by covering the upper end surface 24a of the first active material non-forming portion 34 with the insulating layer 40, it is possible to easily arrange the upper end surface 24a close to the upper edge portion 23a of the separator 23 located outside the upper end surface 24a in the short-side direction Q, while suppressing short-circuiting at the upper end surface 24a. Therefore, the positive electrode metal foil 24 can be expanded in the short-side direction Q, and the battery capacity can be increased.

[0070] The positive electrode tab 35 is formed by cutting the positive electrode metal foil 24 into a predetermined shape. More specifically, the positive electrode tab 35 is formed by cutting off the remaining portion of the positive electrode metal foil 24 except for the portion corresponding to the positive electrode tab 35 at one end portion in the short side direction Q.

[0071] By cutting the positive electrode metal foil 24 in this manner, the upper end surface 24a of the first active material non-forming portion 34 and the side end surfaces 35d, 35e of the positive electrode tab 35 are formed, and then the insulating layer 40 is formed. By forming the insulating layer 40 in this manner after cutting the positive electrode metal foil 24, the first active material non-forming portion 34 and the end surfaces 24a, 35d, 35e of the positive electrode tab 35 can be covered with the insulating layer 40.

[0072] The insulating layer 40 is formed by applying a paste-like material using, for example, a slot die method. However, the method of forming the insulating layer 40 is not limited to this, and the insulating layer 40 may be formed by, for example, electrostatic powder coating.

[0073] Although the present invention has been described above with reference to the above-mentioned embodiment, the present invention is not limited to the above-mentioned embodiment.

[0074] For example, in the above-described embodiment, an energy storage element 1 having a so-called wound type electrode body 20 has been described, but the present invention can also be applied to an energy storage element having a so-called stacked type electrode body 120 (corresponding to the "laminate" in the claims) as shown in FIG. 9.

[0075] 9 is a laminated body formed by alternately stacking a plurality of positive electrode sheets (corresponding to the "first electrode sheet" in the claims) 121 and a plurality of negative electrode sheets (corresponding to the "second electrode sheet" in the claims) 122 with separators 123 interposed therebetween. Each positive electrode sheet has a first active material non-forming portion 34 and a positive electrode tab 35 which is a second active material non-forming portion similar to those described above, and each negative electrode sheet 122 has a negative electrode tab 37 similar to those described above. The electrode body 120 has a positive electrode tab bundle formed by stacking the positive electrode tabs 35 provided on each positive electrode sheet 121, and a negative electrode tab bundle formed by stacking the negative electrode tabs 37 provided on each negative electrode sheet 122.

[0076] In such a stacked electrode body 120, an insulating layer 40 similar to that described above is formed on the first active material non-forming portion 34 of each positive electrode sheet 121 and the positive electrode tab 35, so that the base of the positive electrode tab 35, where stress is likely to concentrate due to bending of the positive electrode tab 35, can be reinforced by the insulating layer, thereby obtaining the same effects as those of the above-described embodiment.

[0077] In addition, in the above-described embodiment, an example has been described in which the "first direction" in which the edge of the positive electrode sheet 21 constituting the first active material non-forming portion 34 extends and the "second direction" in which the positive electrode tab 35 protrudes from the edge are perpendicular to each other. However, in the present invention, the second direction may be inclined with respect to the direction perpendicular to the first direction.

[0078] Furthermore, in the above embodiment, an example has been described in which the first electrode sheet on which the insulating layer is provided is a positive electrode sheet, but the present invention is also applicable to cases in which the first electrode sheet is a negative electrode sheet.

[0079] In the present invention, the metal foil of the first electrode sheet does not necessarily have to be composed of metal only, and may be a metal having a conductive coating layer (film) made of resin or the like formed on the surface of the metal.

[0080] In the present invention, the insulating layer formed on the surface of the metal foil of the first electrode sheet may be formed so as to overlap the surface of the edge of the active material layer, or may be overcoated on the entire surface of the active material layer.

[0081] Furthermore, in the above embodiment, an example in which an insulating layer is formed not only on the surface but also on the end surface of the metal foil of the first electrode sheet has been described, but in the present invention, the insulating layer does not necessarily have to be formed on the end surface of the metal foil. When an insulating layer is not formed on the end surface of the metal foil, the first electrode sheet may be cut to form the first tab after the insulating layer is formed on the surface of the metal foil.

[0082] Furthermore, in the above embodiment, an example has been described in which the base portion of the first tab is rounded, but in the present invention, the base portion of the first tab does not necessarily have to be rounded. [Explanation of symbols]

[0083] 1: Energy storage element 11: Positive external terminal 15: Positive electrode current collector 20: Electrode body (wound body) 20c: Flat section 20d: Curved section 21: Positive electrode sheet (first electrode sheet) 22: Negative electrode sheet (second electrode sheet) 22a: Edge of negative electrode sheet 23: Separator 23a: Edge of separator 24: Positive electrode metal foil 24a: Edge surface of positive electrode metal foil 25: Positive electrode active material layer 34: First active material non-forming area 35: Positive electrode tab (first tab) (second active material non-forming portion) 35a: Base of positive electrode tab 35c: Tip of positive electrode tab 35d, 35e: Side end surface of positive electrode tab 37: Negative electrode tab (second tab) 40: Insulating layer 41: First insulating layer 42: Second insulating layer 42a: Edge of second insulating layer 55: Positive electrode tab bundle (first tab bundle) 57: Negative electrode tab bundle (second tab bundle) 120: Electrode body (laminate) 121: Positive electrode sheet (first electrode sheet) 122: Negative electrode sheet (second electrode sheet) 123: Separator P: Longitudinal direction of sheet (first direction) Q: Short side direction of sheet (second direction) X: Winding axis

Claims

1. A storage element including a first electrode sheet and a second electrode sheet laminated on the first electrode sheet via a separator and having a polarity different from that of the first electrode sheet, The first electrode sheet is a metal foil having an edge portion extending in a first direction and a first tab protruding from the edge portion in a second direction intersecting the first direction; An active material layer formed on the surface of the metal foil; An insulating layer formed on a surface of the metal foil; Equipped with a portion of the metal foil along the edge portion and the first tab are active material non-formed portions where the active material layer is not formed, the insulating layer is provided in a region including a portion along the edge of the active material non-formed portion and a base of the first tab, the insulating layer provided on the portion along the edge and on the base is disposed side by side with the active material layer in the second direction and is integrally connected thereto; the first tab is bent at the base portion on which the insulating layer is provided, A storage element, characterized in that a tip portion of the first tab extends along a direction perpendicular to the first direction and the second direction.

2. The energy storage element according to claim 1 , wherein a portion of the insulating layer formed on the surface of the first tab protrudes beyond an edge of the separator in the second direction.

3. An electric storage element including an electrode body, The electrode body includes a first electrode sheet and a second electrode sheet having a polarity different from that of the first electrode sheet, The first electrode sheet is Metal foil; An active material layer provided on the metal foil; An insulating layer provided on the metal foil; Equipped with the metal foil has an active material non-forming portion where the active material layer is not provided, the active material-free portion has a first active material-free portion extending along an edge portion of the metal foil in a predetermined direction, and a first tab protruding from the first active material-free portion, the insulating layer is provided in a region including a portion along the edge of the active material non-formed portion and a base of the first tab, the insulating layer provided on the portion along the edge and on the base is disposed side by side with the active material layer in the predetermined direction and is integrally connected thereto; the first tab is bent at the base portion on which the insulating layer is provided, A storage element, characterized in that a tip portion of the first tab extends in a direction along the edge portion and in a direction perpendicular to the specified direction.

4. 4 . The energy storage element according to claim 1 , wherein the insulating layer is formed on the active material layer and in a region including a base of the first tab in the active material non-forming portion. 5 .

5. the first tab has a radius at the base that is continuous with the edge; The energy storage element according to claim 1 , wherein the insulating layer is formed in a region including the radius of the first tab.

6. The first electrode sheet further includes a current collector for electrically connecting the first electrode sheet to an external terminal. The energy storage element according to claim 1 , wherein the first tab is connected to the current collector in a bent state.

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