Power storage element

Abstract

To provide a power storage element suppressing occurrence of short-circuit in an active material non-formed part, in which the active material non-formed part is provided along an edge part of an electrode sheet at the side of a tab.SOLUTION: A first electrode sheet comprises: an edge part extending in a first direction; metal foil including a first tab protruding from the edge part in a second direction crossing the first direction; an active material layer formed on a surface of the metal foil; and an insulation layer formed on the surface of the metal foil. A portion along the edge part and the first tab in the metal foil are defined as an active material non-formed part in which the active material layer is not formed. The insulation layer is provided in a region including a portion of the active material non-formed part along the edge part and a base part of the first tab. The insulation layer provided in the portion along the edge part and the base part is disposed in parallel with the active material layer in the second direction and integrally continued. The first tab is folded at the base part where the insulation layer is provided, and a tip end side portion of the first tab extends in a direction orthogonal to the first direction and the second direction.SELECTED DRAWING: Figure 5

Description

Technical Field

[0001] The present invention relates to an energy storage element having a positive electrode sheet and a negative electrode sheet laminated via a separator.

Background Art

[0002] For an energy storage element such as a lithium-ion battery, an electrode body having a positive electrode sheet and a negative electrode sheet alternately laminated via a separator may be used. Generally, the positive electrode sheet and the negative electrode sheet are formed by coating active material layers on both sides of a metal foil.

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

[0004] In this type of energy storage element, not only tabs but also non-active material forming portions may be formed in a portion along the edge on the tab side of the positive electrode sheet. Further, the non-active material forming portion formed along the edge of the positive electrode sheet may be disposed opposite to the active material layer of the negative electrode sheet via a separator.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] However, in a power storage element in which the active material non-forming portion formed along the edge portion on the tab side of the positive electrode sheet is disposed to face the negative electrode active material layer via a separator, if for some reason such as displacement, shrinkage, or breakage of the separator, the positive electrode active material non-forming portion and the negative electrode active material layer come into direct opposition, a short circuit may occur between them.

[0007] Therefore, an object of the present invention is to suppress the occurrence of a short circuit in the active material non-forming portion in a power storage element in which the active material non-forming portion is provided along the edge portion on the tab side of the electrode sheet.

Means for Solving the Problems

[0008] The energy storage element according to the present invention is an energy storage element including a first electrode sheet and a second electrode sheet laminated on the first electrode sheet with a separator interposed therebetween and having a polarity different from that of the first electrode sheet. The first electrode sheet includes a metal foil having 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 the surface of the metal foil, and an insulating layer formed on the surface of the metal foil. A portion along the edge and the first tab in the metal foil are active material non-forming portions where the active material layer is not formed. The insulating layer is provided in a region including a portion along the edge and a base portion of the first tab in the active material non-forming portion. The insulating layer provided in the portion along the edge and the base portion is arranged side by side with the active material layer in the second direction and is integrally continuous. The first tab is bent at the base portion provided with the insulating layer, and a tip-side portion of the first tab extends along a direction orthogonal to the first direction and the second direction. Alternatively, the energy storage element according to the present invention is an energy 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 includes a metal foil, an active material layer provided on the metal foil, and an insulating layer provided on the metal foil. The metal foil has an active material non-forming portion where the active material layer is not provided. The active material non-forming portion includes a first active material non-forming portion extending along an edge of the metal foil in a predetermined direction and a first tab protruding from the first active material non-forming portion. The insulating layer is provided in a region including a portion along the edge and a base portion of the first tab in the active material non-forming portion. The insulating layer provided in the portion along the edge and the base portion is arranged side by side with the active material layer in the predetermined direction and is integrally continuous. The first tab is bent at the base portion provided with the insulating layer, and a tip-side portion of the first tab extends along a direction along the edge and a direction orthogonal to the predetermined direction.

[0009] Thus, even when the first electrode sheet faces the second electrode sheet directly due to displacement, shrinkage, or damage of the separator, an insulating layer is interposed between the non-active material forming portion of the first electrode sheet and the second electrode sheet, thereby suppressing the occurrence of a short circuit in the non-active material forming portion of the first electrode sheet.

[0010] In the present invention, it is preferable that the insulating layer is provided in a region including the base portion of the first tab in the non-active material forming portion. Thereby, while suppressing the occurrence of a short circuit at the base portion of the first tab, the base portion can be reinforced by the insulating layer.

[0011] In the present invention, it is preferable that the first tab has a rounded shape at the base portion. Thereby, the stress applied to the base portion of the first tab can be dispersed, and the strength of the first tab can be improved.

[0012] When the power storage element according to the present invention further includes a current collector for electrically connecting the first electrode sheet to an external terminal, the first tab may be connected to the current collector in a bent state. In this case, since the base portion of the first tab where stress is concentrated by bending is reinforced by the insulating layer, the rigidity and durability of the first tab can be improved.

[0013] In the present invention, it is preferable that the portion formed on the surface of the first tab in the insulating layer protrudes more than the edge portion of the separator in the second direction. Thereby, even when the first tab faces the second electrode sheet without passing through the separator due to displacement, shrinkage, or damage of the separator, an insulating layer is interposed between the metal foil of the first tab and the second electrode sheet, thereby suppressing the occurrence of a short circuit in the first tab.

[0014] In the present invention, in the active material non-forming portion, it is preferable that the insulating layer is also formed on the end face of the metal foil. Thereby, the occurrence of short circuit in the active material non-forming portion of the first electrode sheet can be more effectively suppressed. Further, since the end face of the edge portion of the first electrode sheet is covered with the insulating layer, while suppressing short circuit at the end face of this edge portion, the edge portion of the separator located outside the second direction rather than the edge portion of the first electrode sheet can be made easier to arrange with the edge portion of the first electrode sheet being close. Therefore, the first electrode sheet can be expanded in the second direction, and thereby, an increase in battery capacity can be achieved.

[0015] In the present invention, when the second electrode sheet has an edge portion linearly extending 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 on the same side in the second direction and be arranged at intervals in the first direction. In this case, the above-described effects can be obtained in this type of power 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 wound around an axis parallel to the second direction while being overlapped with each other via the separator to form a wound body, the wound body may include a first tab bundle formed by laminating the plurality of first tabs. In this case, since the rigidity of the base portion of the first tab is enhanced by the insulating layer, when the first electrode sheet is wound, the bending of the first tab that warps in the thickness direction of the first electrode sheet is suppressed. Therefore, when the first electrode sheet is wound and the plurality of first tabs are overlapped, it becomes difficult for the first tabs to catch on each other, and thereby, the breakage of each first tab is suppressed.

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

[0018] When the power storage element 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 separator interposed therebetween, the laminate may include a first tab bundle formed by laminating the first tabs provided on each of the plurality of first electrode sheets. In this case, the above-described effects can be obtained in this type of power storage element.

Effects of the Invention

[0019] According to the present invention, even when the first electrode sheet is directly opposed to the second electrode sheet due to displacement, shrinkage, or breakage of the separator or the like, an insulating layer is interposed between the non-active material forming portion of the first electrode sheet and the second electrode sheet, thereby suppressing the occurrence of a short circuit in the non-active material forming portion of the first electrode sheet.

Brief Description of the Drawings

[0020]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Best Mode for Carrying Out the Invention

[0021] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. In the present specification, terms including "upper" and "lower" used to indicate directions and terms indicating directions related thereto indicate directions in the posture of the power storage element illustrated in the accompanying drawings, and do not necessarily coincide with the directions in the actual use state.

[0022] FIG. 1 shows a power storage element 1 according to an embodiment of the present invention. The power storage element 1 is a non-aqueous electrolyte secondary battery such as a lithium ion battery, for example. However, the present invention can be applied to various power storage elements including capacitors in addition to lithium ion batteries.

[0023] As shown in FIG. 1, the power storage element 1 has, for example, a substantially rectangular parallelepiped case 2. The case 2 has a case body 3 having an upper surface opening and a lid body 4 closing the upper surface opening of the case body 3.

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

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

[0026] Each of the external terminals 11 and 12 is fixed to the upper surface of the lid body 4 by caulking via an upper gasket 13, for example. For the material of the external terminals 11 and 12, metals such as aluminum, copper, and nickel are used, for example.

[0027] In addition, the lid body 4 is provided with a gas discharge valve 8 for discharging gas generated inside the case body 3 to the outside of the case 2 and a liquid injection port (not shown). The liquid injection port is closed with a liquid injection plug 10.

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

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

[0030] Note that the negative electrode current collector is configured in the same manner as the positive electrode current collector 15 described below, but may have a configuration different from that of the positive electrode current collector 15. Also, the positive electrode current collector 15 and the negative electrode current collector may be made of different materials. Specifically, for example, a metal such as aluminum is used for the material of the positive electrode current collector 15, and a metal such as copper is used for the material of the negative electrode current collector.

[0031] The current collector 15 is fixed, for example, by caulking to the lower surface of the lid body 4 via the lower gasket 14. The current collector 15 includes, for example, a first flat plate portion 15a fixed to the lid body 4, a connecting portion 15b that extends downward while curving from the edge portion of the first flat plate portion 15a, and a second flat plate portion 15c that is continuous with the first flat plate portion 15a via the connecting portion 15b and is disposed opposite to the lower side of the first flat plate portion 15a.

[0032] The first flat plate portion 15a is electrically connected to the external terminal 11 via, for example, a rivet portion (not shown) that extends 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 thereby is electrically connected to the electrode body 20.

[0033] Referring to FIGS. 3 and 4 together, the electrode body 20 is composed of 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), both of which are long strips of a certain width, and two separators 23, 23 made of a microporous resin sheet, which are overlapped and wound into a generally oval shape with a relatively high flatness. Between one layer of the positive electrode sheet 21 and one adjacent layer of the negative electrode sheet 22, one of the two separators 23, 23 is interposed. 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 composed of one of the separators 23.

[0034] The axis (winding axis) of winding of the positive electrode sheet 21, the negative electrode sheet 22, and the two separators 23, 23 is conceptually indicated by the reference symbol X in FIG. 3. The electrode body 20 is accommodated in the case body 3 in a posture where the winding axis X extends generally in the direction in which the bottom wall portion of the case body 3 shown in FIG. 1 faces the upper surface opening (the vertical direction in FIG. 1).

[0035] As shown in FIG. 3, at each end of the electrode body 20 in the direction in which the winding axis X extends, there are end faces 20a, 20b where the ends in the width direction (short side direction) of the positive electrode sheet 21, the negative electrode sheet 22, and the separators 23, 23 are arranged. The electrode body 20 has a pair of flat portions 20c, 20c that are arranged opposite to each other with the winding axis X interposed therebetween and extend in a linear shape 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 so as to be semicircularly curved when viewed from the direction in which the winding axis X extends and connect between the pair of flat portions 20c, 20c.

[0036] Note that the flat portion 20c is a portion that extends linearly in terms of design. In the actual state where the electrode body 20 is accommodated in the case 2, the flat portion 20c is not necessarily arranged in a completely linear shape, and may be arranged in a state where it is bent so as to have a shape close to a straight line as a whole.

[0037] As shown in FIGS. 3 and 4, the positive electrode sheet 21 includes a strip-shaped positive electrode metal foil 24 and positive electrode active material layers 25 formed on both surfaces of the positive electrode metal foil 24. The edges on both sides in the width direction (short side direction) of the positive electrode metal foil 24 are formed to extend linearly along the longitudinal direction of the positive electrode metal foil 24. On one side in the width direction of the positive electrode metal foil 24 (the lower side in FIGS. 3 and 4), the positive electrode active material layer 25 is provided up to the edge of the positive electrode metal foil 24. On the edge on the other side in the width direction of the positive electrode metal foil 24 (the upper side in FIGS. 3 and 4), a first active material non-forming portion 34 exposing the positive electrode metal foil 24 is provided without the positive electrode active material layer 25. The first active material non-forming portion 34 of the positive electrode metal foil 24 is covered with an insulating layer 40 (see FIGS. 5 to 8) described later. In FIG. 3, the illustration of the insulating layer 40 is omitted.

[0038] For the material of the positive electrode metal foil 24, for example, aluminum is used, but other metals may also be used. As the positive electrode active material, for example, lithium manganate (LiMn2O4), lithium nickel cobalt manganate (LiNixCoyMn1-x-yO2), lithium cobaltate (LiCoO2), lithium nickelate (LiNiO2), lithium iron phosphate (LiFePO4), lithium manganese phosphate (LiMnPO4), those using substitution additives for these, or mixtures thereof, etc. are 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 negative electrode active material layers 27 formed on both surfaces of the negative electrode metal foil 26. The edges on both sides in the width direction (short side direction) of the negative electrode metal foil 26 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 (the upper side and the lower side in FIGS. 3 and 4), the negative electrode active material layer 27 is provided up to the edge of the negative electrode metal foil 26. Thereby, the entire surface of each side of the negative electrode metal foil 26 is covered with the negative electrode active material layer 27.

[0040] As the material of the negative electrode metal foil 26, for example, copper is used, but other metals may also be used. As the negative electrode active material, for example, graphite is used, but other carbon materials, lithium metal, lithium alloy, lithium titanate (Li4Ti5O12), silicon, silicon monoxide, tin, and other lithium-storable materials, or mixtures thereof may also be used.

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

[0042] As shown in FIG. 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 larger than the width of the positive electrode sheet 21. The negative electrode sheet 22 protrudes outward from the edge of the positive electrode sheet 21 on both sides in the short-side direction Q. The width of the separator 23 is larger than the width of the negative electrode sheet 22. The separator 23 protrudes outward from the edge of the negative electrode sheet 22 on both sides in the short-side direction Q.

[0043] As shown in FIGS. 3 and 4, on the positive electrode metal foil 24, a plurality of positive electrode tabs (corresponding to the "first tabs" in the claims) 35 that protrude outward in the short-side direction Q from the first active material non-forming portion 34 that linearly extends along the edge on one side (the upper side in FIGS. 3 and 4) in the short-side direction Q are provided at intervals in the longitudinal direction P. The first active material non-forming portion 34 and the plurality of positive electrode tabs 35 are formed of a single positive electrode metal foil 24, and each positive electrode tab 35 is integrally continuous with the first active material non-forming portion 34. The positive electrode tab 35 is a second active material non-forming portion on the surface of the positive electrode metal foil 24 where the active material layer is not formed.

[0044] As shown in FIG. 5, at the base 35a of the positive electrode tab 35, a rounded portion 35f is provided at the corner portion 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 short transverse direction Q. The rounded portions 35f, 35f are provided at both edge portions of the base 35a in the longitudinal direction P. Thereby, the width of the base 35a in the longitudinal direction P gradually increases as it approaches the first active material non-forming portion 34. By providing such rounded portions 35f, 35f, the stress concentration applied to the base 35a of the positive electrode tab 35, particularly at the corner portion, can be dispersed, and breakage at the base 35a is suppressed. That is, the strength of the base 35a of the positive electrode tab 35 is increased.

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

[0046] As shown in FIG. 3, the electrode body 20 formed by laminating and winding the positive electrode sheet 21 and the negative electrode sheet 22 with the separators 23, 23 interposed therebetween includes a positive electrode tab bundle (corresponding to the "first tab bundle" in the claims) 55 formed by laminating a plurality of positive electrode tabs 35. The positive electrode tab bundle 55 is provided on one flat portion 20c of the electrode body 20.

[0047] The negative electrode tab 37 is arranged 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 wound electrode body 20, the plurality of negative electrode tabs 37 overlap each other, thereby forming a negative electrode tab bundle 57 as the second tab bundle.

[0048] The positive tab bundle 55 and the negative tab bundle 57 project from one end face portion 20a (the upper end face portion in FIG. 3) of the electrode body 20. Further, the positive tab bundle 55 and the negative tab bundle 57 project from one side (the front side in FIG. 3) of the pair of flat portions 20c, 20c with respect to the longitudinal center line Y when the end face portion 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 tab bundle 55 protruding from one flat portion 20c of the electrode body 20 is connected to the positive current collector 15 in a state of being bent so as to be laid down on the other flat portion 20c side in the thickness direction Z (the direction perpendicular to the winding axis X and the center line Y) of the electrode body 20.

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

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

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

[0053] Hereinafter, with reference to FIGS. 5 to 8, the insulating layer 40 of the positive electrode sheet 21 and the related configuration will be described.

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

[0055] As shown in FIGS. 6 and 7, in the short-side direction Q, the negative electrode active material layer 27 is disposed so as to protrude outward more than the positive electrode active material layer 25. Thereby, when the power storage element 1 is a lithium ion battery, lithium ions released from the positive electrode active material layer 25 during charging are easily occluded in the negative electrode active material layer 27.

[0056] As shown in FIGS. 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 surfaces of the positive electrode metal foil 24. The insulating layer 40 includes a first insulating layer portion 41 provided on the first active material non-forming portion 34 of the positive electrode metal foil 24 and a second insulating layer portion 42 provided on the positive electrode tab 35 which is the second active material non-forming portion.

[0057] As shown in FIGS. 5 and 6, the first insulating layer portion 41 is similarly provided on both surface sides 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 of the positive electrode active material layer 25 in the short-side direction Q and covers the upper edge of the positive electrode active material layer 25.

[0058] The first insulating layer portion 41 is formed so as to protrude more than 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. Thereby, both surface sides 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] As shown in FIG. 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 proximal end to the middle portion of the positive electrode tab 35. The tip-side portion 35b of the positive electrode tab 35 is exposed without being covered by the insulating layer 40, whereby the connection with the current collector 15 described above at the tip-side portion 35b is made possible.

[0060] As shown in FIG. 7, the second insulating layer portion 42 is similarly provided on both surfaces of the positive electrode tab 35. On each surface of the positive electrode tab 35, the second insulating layer portion 42 is integrally continuous outside 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] Thus, since the base portion 35a of the positive electrode tab 35 is covered by the insulating layer 40, while suppressing the occurrence of a short circuit, the base portion 35a can be reinforced by the insulating layer 40. Since the positive electrode tab 35 is bent for connection with the current collector 15 as described above (see FIG. 2), stress tends to concentrate on the bent base portion 35a, but since the base portion 35a is reinforced by the insulating layer 40, the rigidity of the positive electrode tab 35 can be increased and the durability can be improved.

[0062] Further, since the rigidity of the base portion 35a of the positive electrode tab 35 is increased by the insulating layer 40, when winding the positive electrode sheet 21, the bending of the positive electrode tab 35 that warps in the thickness direction R is suppressed. Therefore, when winding the positive electrode sheet 21 and stacking a plurality of positive electrode tabs 35, it becomes difficult for the positive electrode tabs 35 to catch on each other, whereby breakage of each positive electrode tab 35 is suppressed. Furthermore, as described above, since the rounded portions 35f, 35f are provided on the base portion 35a, even when tension is applied to the positive electrode sheet 21 during winding, stress concentration on the base portion 35a is alleviated and the strength of the base portion 35a is further improved.

[0063] As shown in Fig. 8, the second insulating layer portion 42 of the insulating layer 40 protrudes outside the positive electrode tab 35 on both sides in the longitudinal direction P, covering the side end faces 35d and 35e on both sides of the positive electrode tab 35. Thereby, the base portion 35a of the positive electrode tab 35 has the surfaces on both sides of the positive electrode tab 35 and the side end faces 35d and 35e on both sides covered by the second insulating layer portion 42.

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

[0065] As shown in Figs. 6 and 7, the insulating layer 40 is disposed opposite to the negative electrode active material layer 27 with the separator 23 interposed therebetween. In particular, the second insulating layer portion 42 of the insulating layer 40 protrudes above the upper edge portion 23a of the separator 23 in the short side direction Q. Therefore, due to some cause including displacement, shrinkage or damage of the separator 23, a portion where the separator 23 is not interposed between the first active material non-forming portion 34 and the base portion 35a of the positive electrode tab 35 in the positive electrode sheet 21 and the negative electrode active material layer 27 is generated. Even if the positive electrode sheet 21 and the negative electrode sheet 22 come into contact by chance, the insulating layer 40 covering the metal portion of the positive electrode sheet 21 is interposed between the metal foil 24 in 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] Also, as shown in Figs. 6 and 8, since the insulating layer 40 covers not only the surfaces on both sides of the first active material non-forming portion 34 and the base portion 35a of the positive electrode tab 35 but also these end faces 24a, 35d, 35e, the occurrence of a short circuit can be more effectively suppressed.

[0067] If a metal such as copper that dissolves at the positive electrode potential is mixed onto the positive electrode metal foil 24, the metal will dissolve on the positive electrode metal foil 24. When the metal thus dissolved deposits on the negative electrode sheet 22 and the deposit of the metal grows and contacts the positive electrode sheet 21, a short circuit is caused.

[0068] However, according to the present embodiment, as shown in FIGS. 6 and 7, since the positive electrode metal foil 24 is covered with the insulating layer 40, dissolution of the metal on the positive electrode metal foil 24 located in the vicinity of the negative electrode sheet 22 is prevented, and thus, deposition of the metal on the negative electrode sheet 22 can be suppressed. Thereby, a short circuit caused by the deposit of the metal can be prevented.

[0069] Furthermore, since the upper end surface 24a of the first active material non-forming portion 34 is covered with the insulating layer 40, while suppressing a short circuit at this upper end surface 24a, it becomes easier to dispose the upper end surface 24a closer to the upper edge portion 23a of the separator 23 located outside the upper end surface 24a in the short side direction Q. Therefore, the positive electrode metal foil 24 can be expanded in the short side direction Q, and thereby, an increase in battery capacity can be achieved.

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

[0071] By such cutting of the positive electrode metal foil 24, 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. Thus, since the insulating layer 40 is formed after the cutting of the positive electrode metal foil 24, the end surfaces 24a, 35d, 35e of the first active material non-forming portion 34 and the positive electrode tab 35 can be covered with the insulating layer 40.

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

[0073] As described above, the present invention has been described with reference to the above-described embodiments, but the present invention is not limited to the above-described embodiments.

[0074] For example, in the above-described embodiment, the power storage element 1 having a so-called wound electrode body 20 has been described, but the present invention is also applicable to a power storage element having a so-called stacked electrode body 120 (corresponding to the "laminated body" in the claims) as shown in FIG. 9.

[0075] The electrode body 120 shown in FIG. 9 is a laminated body in which 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 are alternately laminated with a separator 123 interposed therebetween. Each positive electrode sheet includes a first active material non-forming portion 34 similar to the above and a positive electrode tab 35 which is a second active material non-forming portion, and each negative electrode sheet 122 includes a negative electrode tab 37 similar to the above. The electrode body 120 includes a positive electrode tab bundle formed by laminating the positive electrode tabs 35 provided on each positive electrode sheet 121 and a negative electrode tab bundle formed by laminating the negative electrode tabs 37 provided on each negative electrode sheet 122.

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

[0077] Further, in the above-described embodiment, an example 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 has been described. 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-described embodiment, an example in which the first electrode sheet provided with the insulating layer is a positive electrode sheet has been described. However, the present invention is also applicable when 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 only of metal, and may be one in which a conductive coating layer (film) made of resin or the like is formed on the surface of the metal.

[0080] Also, 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 portion of the active material layer, or may be overcoated on the entire surface of the active material layer.

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

[0082] Moreover, in the above-described embodiment, an example in which a round shape is provided at the base of the first tab has been described. However, in the present invention, it is not necessary to provide a round shape at the base of the first tab.

Explanation of Reference Numerals

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

Claims

1. A power 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, wherein the first electrode sheet comprises a metal foil having 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 the surface of the metal foil, and an insulating layer formed on the surface of the metal foil, and a portion along the edge and the first tab in the metal foil are active material non-formation portions where the active material layer is not formed, the insulating layer is provided in a region including a portion along the edge and the base of the first tab in the active material non-formation portion, the insulating layer provided in the portion along the edge and the base is arranged side by side with the active material layer in the second direction and is integrally continuous, the first tab is bent at the base provided with the insulating layer, and a tip-side portion of the first tab extends along a direction orthogonal to the first direction and the second direction. The power storage element is characterized by this.

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

3. A power storage element comprising an electrode body, wherein the electrode body has a first electrode sheet and a second electrode sheet having a polarity different from that of the first electrode sheet, and the first electrode sheet comprises a metal foil, an active material layer provided on the metal foil, and an insulating layer provided on the metal foil, and the metal foil has an active material non-formation portion where the active material layer is not provided, the active material non-formation portion has a first active material non-formation portion extending along an edge of the metal foil in a predetermined direction and a first tab protruding from the first active material non-formation portion, the insulating layer is provided in a region including a portion along the edge and the base of the first tab in the active material non-formation portion, the insulating layer provided in the portion along the edge and the base is arranged side by side with the active material layer in the predetermined direction and is integrally continuous, the first tab is bent at the base provided with the insulating layer, and a tip-side portion of the first tab extends along a direction along the edge and a direction orthogonal to the predetermined direction. The power storage element is characterized by this.

4. The insulating layer is formed on the active material layer and in a region including the base of the first tab in the non-active material formation portion. The electrical storage element according to any one of claims 1 to 3, characterized in that.

5. The first tab has a rounded portion that is continuous with the edge at the base, The insulating layer is formed in a region including the rounded portion of the first tab. The electrical storage element according to any one of claims 1 to 4, characterized in that.

6. Further comprising a current collector for electrically connecting the first electrode sheet to an external terminal, The first tab is connected to the current collector in a bent state. The electrical storage element according to any one of claims 1 to 5, characterized in that.

Images